ST – Solar-Terrestrial Sciences

EGU22-901 | Presentations | ST2.4 | Arne Richter Award for Outstanding ECS Lecture

Ion dynamics in the inner magnetosphere during Van Allen Probe Era 

Chao Yue

Ion dynamics are controlled by the energy-dependent source, transport, energization, and loss processes. Systematic changes in the ion dynamics are essential to understand the ring current variations in the inner magnetosphere. The Van Allen Probes mission, which orbits near the equatorial plane inside the geosynchronous orbit, has a wide energy coverage with high energy resolution and state-of-the-art ion composition instrumentation. It provides a great opportunity to investigate plasma dynamics. In this talk, I will present some of our recent studies on the ion dynamics of different populations and species as well as the related plasma wave activity during geomagnetic quiet and active times.

How to cite: Yue, C.: Ion dynamics in the inner magnetosphere during Van Allen Probe Era, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-901, https://doi.org/10.5194/egusphere-egu22-901, 2022.

EGU22-1115 | Presentations | MAL13 | Hannes Alfvén Medal Lecture

Our Heliosphere and its Interstellar Interaction: A Solar Cycle of Global Observations and Discoveries 

David McComas

The supersonic solar wind and its embedded magnetic field continuously flow outward in all directions from the sun. This magnetized plasma inflates a bubble – the heliosphere – in the very-local interstellar medium (VLISM). The Interstellar Boundary Explorer (IBEX) mission launched in late 2008 and has been continuously returning 3-D global images of Energetic Neutral Atoms (ENAs) that derive from ion populations in the heliosheath and beyond. Now spanning more than a full solar cycle, IBEX’s all-sky maps and observations uniquely inform the global outer heliosphere and its evolving interstellar interaction. Insights from IBEX, in concert with in situ observations by the two Voyager spacecraft, which were transiting two different trajectories through the outer boundaries of the heliosphere contemporaneously with IBEX, have led to a true scientific revolution in our understanding of the outer heliosphere and its interstellar interaction. This Hannes Alfvén Medal Lecture will summarize some of the many discoveries and “firsts” from the IBEX mission and their implications for the outer heliosphere and VLISM. Finally, we will also look forward to the promise of the even more advanced Interstellar Mapping and Acceleration Probe (IMAP) mission, which is under development and slated to launch in 2025.

How to cite: McComas, D.: Our Heliosphere and its Interstellar Interaction: A Solar Cycle of Global Observations and Discoveries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1115, https://doi.org/10.5194/egusphere-egu22-1115, 2022.

EGU22-8388 | Presentations | MAL13 | ST Division Outstanding ECS Award Lecture

A Revised Collection of Sunspot Group Numbers: Context and Future Improvements 

Víctor Carrasco

Rudolf Wolf, first director of the Zürich Observatory around mid-19th century, recovered a large number of sunspot observations made by astronomers several solar cycles back. Based on that database, he defined the relative sunspot number from the number of sunspot groups and individual sunspots. He extended his daily and monthly series until 1749, whereas his yearly series to 1700 (Clette et al. 2014). Nowadays, the World Data Center Sunspot Index and Long-term Solar Observations is the responsible to maintain this sunspot number index. At the end of the 20th century, Hoyt and Schatten (1998) compiled more sunspot observations made by astronomers since the beginning of the 17th century. Thus, they created the group sunspot number index from the number of sunspot groups. Unlike the relative sunspot number, their series starts in 1610.

More recently, several works have detected some problems both in these two indices and the databases. For example, Vaquero et al. (2016) published a revised collection of sunspot group numbers correcting some of the mistakes found in the Hoyt and Schatten database, in addition to incorporate other unknown sunspot records. Currently, there is an ongoing global effort to improve the weakness of the database and recalibrate the indices. Some remarkable improvements to be carried out in future versions of the sunspot number databases have been made regarding the earliest sunspot observations recorded by astronomers such as Galileo and Scheiner, inter alia. Then, corrections of significant mistakes detected in the sunspot counting assigned to these observers in the existing databases are proposed as well as the incorporation of telescopic sunspot records made by the earliest observers not included in these databases.

The sunspot number series is the index including the longest direct solar observation set to study the long-term solar activity evolution and its influence on the Earth. Therefore, we need that the databases, in which these indices are based, are free of problematic observations and, moreover, to improve their observational coverage before mid-19th century. Thus, we will understand better past, present and future solar activity.

References

Clette, F., Svalgaard, L., Vaquero, J.M., Cliver, E.W.: 2014, Revisiting the Sunspot Number. A 400-Year Perspective on the Solar Cycle, SSRv 186, 35. DOI: 10.1007/s11214-014-0074-2.

Hoyt, D.V., Schatten, K.H.: 1998, Group sunspot numbers: a new solar activity reconstruction. Solar Phys. 179, 189. DOI: 10.1023/A:1005007527816.

Vaquero, J.M., Svalgaard, L., Carrasco, V.M.S., Clette, F., Lefèvre, L., Gallego, M.C., Arlt, R., Aparicio, A.J.P., Richard, J.-G., Howe, R.: 2016, A Revised Collection of Sunspot Group Numbers, Sol. Phys. 291, 3061. DOI: 10.1007/s11207-016-0982-2.

How to cite: Carrasco, V.: A Revised Collection of Sunspot Group Numbers: Context and Future Improvements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8388, https://doi.org/10.5194/egusphere-egu22-8388, 2022.

ST1 – The Sun and Heliosphere

EGU22-307 | Presentations | ST1.1

Joint Instabilities of Sheared Flows and Magnetic Fields 

Patrick Lewis, David Hughes, and Evy Kersale

Shear flows and magnetic fields are ubiquitous in astrophysical bodies such as stars and accretion discs. Furthermore,
the interaction between flows and magnetic field plays a key role in the dynamics of plasma fusion devices. Typically,
the flows and magnetic field are both sheared, and it is therefore a problem of fundamental importance to understand
the instabilities that may occur in such a system.

In the absence of magnetic field, the linear stability of a viscous sheared flow is governed by the Orr-Sommerfeld
equation; this is one of the classic problems of hydrodynamics. At the other limit, there are somewhat analogous
instabilities of a fluid of finite electrical conductivity containing a static sheared magnetic field. These are related to
the classical tearing modes that have received considerable attention in both the astrophysical and plasma physics
literature.

In general though, the fluid flow and the magnetic field will both be important players. Previous studies have investigated
configurations which have served as models for systems such as the magnetotail and solar surges. While these
investigations have been fruitful, the prescription of the basic field and flow, while physically motivated, have been
chosen somewhat arbitrarily. It is therefore of interest to consider the instability problem within this more general
framework.

Motivated astrophysically, such as by the dynamics in the solar tachocline, here we consider a self-consistent problem
in which both instabilities can occur. In particular, we consider the stability of equilibrium states arising from the
shearing of a uniform magnetic field by a forced transverse flow. The problem is governed by three non-dimensional
parameters: the Chandrasekhar number, and the flow and magnetic Reynolds numbers. In opposite limits of parameter
space, we recover the predictions of the aforementioned classical problems. As we move through this three-dimensional
parameter space, a range of interactions are possible: We demonstrate the stabilisation of a purely hydrodynamic
instability through the magnetic field, show the existence of a joint instability outlining the physical mechanisms at
play, and demonstrate that under certain conditions, hydrodynamically-stable parallel shear flows lead to instability
growth rates that exceed those of static tearing modes. To conclude, we elucidate the consequences of considering
the linear stability of an evolving background state and show that a quasi-static approach may not be meaningful. In
these circumstances, it therefore becomes essential to perform a stability analysis of a time-varying basic state.

 

 

How to cite: Lewis, P., Hughes, D., and Kersale, E.: Joint Instabilities of Sheared Flows and Magnetic Fields, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-307, https://doi.org/10.5194/egusphere-egu22-307, 2022.

EGU22-1496 | Presentations | ST1.1

Modelling magneto-hydro-static equilibria in quiet Sun regions 

Thomas Wiegelmann and Maria Madjarska

The solar magnetic field is measured routinely only
in the solar photosphere. While reliable measurements
of the photospheric magnetic field vector are only available
in active regions, in the quiet Sun at present only
 the vertical component of the magnetic field can be obtained accurately.
 To derive magnetic field structures throughout the solar atmosphere, from
 the chromosphere to the corona, we extrapolate these photospheric measurements
into the upper photosphere, chromosphere and corona with a magneto-hydro-static
model. We optimize free model parameters by comparing the modelled magnetic
field lines with structures observed in solar images. The comparison is
done automatically with a number of quantitative measurements and
the optimal model parameters are found with the help of
a downhill simplex minimization. This newly developed modelling approach can
provide an accurate and deep understanding of the magnetic field structures
that extend to any height in the solar atmosphere.

How to cite: Wiegelmann, T. and Madjarska, M.: Modelling magneto-hydro-static equilibria in quiet Sun regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1496, https://doi.org/10.5194/egusphere-egu22-1496, 2022.

EGU22-1598 | Presentations | ST1.1

Oblique instabilities driven by pickup ion ring-beam distributions in the outer heliosheath 

Ameneh Mousavi, Kaijun Liu, and Sina Sadeghzadeh

The energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary Explorer (IBEX) spacecraft is believed to originate from the pickup ions in the outer heliosheath. The outer heliosheath pickup ions generally have a ring-beam velocity distribution at a certain pickup angle, α, the angle at which these ions are picked up by the interstellar magnetic field. The pickup ion ring-beam distributions can drive unstable waves of different propagation angles with respect to the background interstellar magnetic field, θ. Previous studies of the outer heliosheath pickup ion dynamics were mainly focused on ring-like pickup ion distributions with α≈90° and/or the parallel- and anti-parallel-propagating unstable waves (θ=0°and 180°). The present study carries out linear kinetic instability analysis to investigate both the parallel and oblique unstable modes (0°≤θ≤180°) driven by ring-beam pickup ion distributions of different pickup angles between 0° and 90°. Our linear analysis reveals that ring-beam pickup ions can excite mirror waves as well as oblique left-helicity waves and their harmonics. The maximum growth rate of the mirror mode increases with increasing α. On the other hand, the wavenumber and growth rate of the most unstable oblique left-helicity modes are consistent with the unstable modes of 0°and 180° examined in our earlier work.

How to cite: Mousavi, A., Liu, K., and Sadeghzadeh, S.: Oblique instabilities driven by pickup ion ring-beam distributions in the outer heliosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1598, https://doi.org/10.5194/egusphere-egu22-1598, 2022.

EGU22-1705 | Presentations | ST1.1

Characteristic ion length scales for four types of interplanetary shocks 

Byeongseon Park, Alexander Pitna, Jana Safrankova, and Zdenek Nemecek

The interaction between interplanetary (IP) shock and solar wind has been studied for the understanding of the energy dissipation mechanism within the collisionless plasma. The power spectra of the magnetic field exhibit breaks, where steepening of these spectra occurs. These breaks have been observed and also regarded as a threshold distinguishing the kinetic range from the inertial range of turbulence. Different heating processes can be related mainly to two characteristic ion length scales — ion inertial length and ion gyroradius. We attempt to establish the relation between these length scales and the spectral break. Data for four different types of IP shocks (fast forwards, fast reverse, slow forwards, slow reverse) measured for 2 hours (one hour for up and downstream plasma) by WIND at 1 AU were used. Continuous wavelet transform for the estimation of the power spectra of measured magnetic field was employed. Spectral breaks were determined by fitting 2-segment piecewise linear function around the expected break position in log-log space. Preliminary analysis of these spectral breaks and the characteristic length scales in fast shocks yields results consistent with the previous studies. Additionally, we extended this analysis towards slow shocks and obtained similar results. While the level of power enhancement of the magnetic field due to fast shocks reaches the order of ten on average, only the order of one was shown for slow shocks. The level of the compression of the characteristic spatial scales, however, is approximately similar for fast and slow shocks.

How to cite: Park, B., Pitna, A., Safrankova, J., and Nemecek, Z.: Characteristic ion length scales for four types of interplanetary shocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1705, https://doi.org/10.5194/egusphere-egu22-1705, 2022.

EGU22-1895 | Presentations | ST1.1

Towards a realistic evaluation of transport coefficients in non-equilibrium plasmas from space 

Edin Husidic, Marian Lazar, Klaus Scherer, Horst Fichtner, and Stefaan Poedts

While space plasmas are largely considered to be nearly collisionless, at relatively low heliocentric distances, that is, below 1 AU, particle-particle collisions still play an important role in the transport of matter, momentum, and energy. A way to quantify these processes macroscopically, e.g., in fluid models, is within classical transport theory, where fluxes and their sources are linearly related by transport coefficients. In the solar wind context, of particular interest are the observed velocity distributions of plasma particles with Kappa-distributed suprathermal tails, conditioned not only by binary collisisions, but also by their interaction with plasma waves and turbulence. We present first derivations of the main transport coefficients based on regularised Kappa distributions (RKDs), which, unlike standard Kappa distributions (SKDs), enable a macroscopic description of non-equilibrium plasmas without mathematical divergences or physical inconsistencies. All transport coefficients are finite, well defined for all values of κ > 0, and markedly enhanced in the presence of suprathermal electrons. The results indicate that for low values of κ, that is, below the SKD poles, the transport coefficients can be many orders of magnitudes higher than the corresponding Maxwellian limits, which can lead to significant underestimations if suprathermal electrons are ignored. Moreover, we show the importance of an adequate Kappa modeling of suprathermal populations by contrasting our results to other modified interpretations that underestimate the effects of suprathermals.

How to cite: Husidic, E., Lazar, M., Scherer, K., Fichtner, H., and Poedts, S.: Towards a realistic evaluation of transport coefficients in non-equilibrium plasmas from space, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1895, https://doi.org/10.5194/egusphere-egu22-1895, 2022.

EGU22-2814 | Presentations | ST1.1

Hybrid Particle-In-Cell model with Adaptive Mesh Refinement 

Nicolas Aunai, Roch Smets, Philip Deegan, Andrea Ciardi, and Alexis Jeandet

Collisionless magentized plasmas a priori need to be evolved using Vlasov-Maxwell kinetic formalism.
However the tremendous number of spatial and temporal scales involved in phenomena of interest makes it prohibitive, from a computational standpoint.
Fully kinetic particle in cell and single fluid MHD codes are commonly used at very small or very large scales.
The hybrid formalism, treating ions kinetically and electrons as a fluid, is in principle advantageous to fill the gap between these two extremities.
However, a correct treatment of critical regions such as reconnection X-lines require a good resolution of sub-ion dissipative scales, which
still constitute a major challenge if aiming at simulating meso/macro scale systems.
This work presents a new code, named PHARE, which successfully implements the adaptive mesh refinement mechanism in a hybrid particle-in-cell code.
Such a code is able to dynamically focus the resolution in critical regions while others not only have a coarser spatial resolution, but are also
evolved much less often thanks to a recursive time stepping procedure.
Adopting a patch based AMR mechanism, the code architecture is made so that the specific solver/physical model that is solved at a given refined level
is abstracted, thus giving the opportunity to handling multi-formalisms AMR patch hierarchies, where, for instance, coarsest levels are solved in MHD while
dynamicall created refined levels are solved within the Hybrid framework.

How to cite: Aunai, N., Smets, R., Deegan, P., Ciardi, A., and Jeandet, A.: Hybrid Particle-In-Cell model with Adaptive Mesh Refinement, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2814, https://doi.org/10.5194/egusphere-egu22-2814, 2022.

EGU22-2862 | Presentations | ST1.1 | Highlight

The ESA Virtual Space Weather Modelling Centre 

Stefaan Poedts and the VSWMC-P3 team

The ESA Virtual Space Weather Modelling Centre (VSWMC) project was defined as a long term project including different successive parts. Parts 1 and 2 were completed in the first 4-5 years and designed and developed a system that enables models and other components to be installed locally or geographically distributed and to be coupled and run remotely from the central system. A first, limited version went operational in May 2019 under the H-ESC umbrella on the ESA SSA SWE Portal. It is similar to CCMC but interactive (no runs on demand) and the models are geographically distributed and coupled over the internet.

The goal of the ESA project "Virtual Space Weather Modelling Centre - Part 3" (2019-2021) was to further develop the Virtual Space Weather Modelling Centre, building on the Part 2 prototype system and focusing on the interaction with the ESA SSA SWE system. The objectives and scope of this new project include maintaining the current operational system, the efficient integration of 11 new models and many new model couplings, including daily automated end-to-end (Sun to Earth) simulations, the further development and wider use of the coupling toolkit  and front-end GUI, making the operational system more robust and user-friendly. The VSWMC-Part 3 project finished recently.

The 11 new models that have been integrated are Wind-Predict (a global coronal model from CEA, France), the Coupled Thermosphere/Ionosphere Plasmasphere (CTIP) model, Multi-VP (another global coronal model form IRAP/CNRS, France), the BIRA Plasma sphere Model of electron density and temperatures inside and outside the plasmasphere coupled with the ionosphere (BPIM, Belgium), the SNRB  (also named SNB3GEO) model for electron fluxes at geostationary orbit (covering the GOES 15 energy channels >800keV and >2MeV) and the SNGI geomagnetic indices Kp and Dst models (University of Sheffield, UK), the SPARX Solar Energetic Particles transport model (University of Central Lancashire, UK), Spenvis DICTAT tool for s/c internal charging analysis (BISA, Belgium), the Gorgon magnetosphere model (ICL, UK), and the Drag Temperature Model (DTM) and operations-focused whole atmosphere model MCM being developed in the H2020 project SWAMI. Many new couplings have also been implemented and a dynamic coupling facility has been installed. Moreover, Daily runs are implemented of two model chains covering the whole Sun-to-Earth domain. The results of these daily runs are made available to all VSWMC users.

We will provide an overview of the state-of-the-art, including the new available model couplings and daily model chain runs, and demonstrate the system.

How to cite: Poedts, S. and the VSWMC-P3 team: The ESA Virtual Space Weather Modelling Centre, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2862, https://doi.org/10.5194/egusphere-egu22-2862, 2022.

The acceleration of high-energy charged particles is common both in heliophysics and astrophysics. Although the diffusive shock acceleration (DSA) has been the well-accepted standard mechanism for particle acceleration at shocks, the fundamental issue is that DSA does not predict the number of accelerated particles. In other words, it relies on an unprescribed injection mechanism that provides a seed population from which the particle acceleration proceeds. Resolving the so-called injection problem is more challenging for electrons than ions because scattering low-energy electrons requires high-frequency waves, which are usually much lower in intensity than low-frequency fluctuations.

 

We have proposed stochastic shock drift acceleration (SSDA) as a plausible electron injection mechanism that can take place within the transition layer of quasi-perpendicular shocks [Katou & Amano, 2019]. The energy gain mechanism of SSDA is essentially the same as the conventional shock drift acceleration (SDA), but the presence of stochastic pitch-angle scattering makes the acceleration more efficient. We will show that the theoretical predictions nicely explain in-situ observations by Magnetospheric MultiScale (MMS) spacecraft [Amano et al. 2020]. Recent fully kinetic Particle-In-Cell (PIC) simulation results will also be shown, in which we found signatures of SSDA [Matsumoto et al. 2017, Kobzar et al. 2021]. We will also present an extended theoretical model that unifies SSDA and DSA. The model predicts a wide range of the energy spectrum from sub-relativistic and relativistic energies. The particle acceleration in the sub-relativistic energy will be dominated by SSDA, which has a spectral index steeper than the standard DSA. Under certain conditions, the particle acceleration mechanism may smoothly transition from SSDA to DSA, and the spectral index approaches the canonical DSA prediction. Therefore, the model can consistently describe the whole particle acceleration process, including the injection by SSDA and the main acceleration to cosmic-ray energies by DSA. We argue that the electron injection scheme through SSDA is realized preferentially at shocks with higher Alfven Mach numbers defined in the Hoffmann-Teller frame.

How to cite: Amano, T.: Electron Injection via Stochastic Shock Drift Acceleration: Theory, Simulation, and Observation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3277, https://doi.org/10.5194/egusphere-egu22-3277, 2022.

EGU22-3304 | Presentations | ST1.1 | Highlight

Recent progress on developments of the magnetohydrostatic extrapolation 

Xiaoshuai Zhu, Thomas Wiegelmann, and Bernd Inhester

The magnetohydrostatic (MHS) extrapolation is developed to model the three-dimensional magnetic fields and plasma of the solar atmosphere with the measured vector magnetogram used as boundary condition. It differs from the nonlinear force-free field (NLFFF) extrapolation in that it takes into account plasma forces include pressure gradient and gravity. In this presentation, I will report the recent progress in two aspects on developments of the MHS extrapolation. The first one is the development of a preprocessing method to deal with the non-MHS vector magetograms. The reason of doing this is that there are a small number of the vector magnetograms which are not consistent with the MHS equilibria. The second aspect is the combination of the MHS extrapolation and the NLFFF extrapolation to improve the efficiency of the computation.

How to cite: Zhu, X., Wiegelmann, T., and Inhester, B.: Recent progress on developments of the magnetohydrostatic extrapolation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3304, https://doi.org/10.5194/egusphere-egu22-3304, 2022.

EGU22-3345 | Presentations | ST1.1

Fluid modeling of collisionless plasmas with a non-local kinetic closure 

Taiki Jikei and Takanobu Amano

Modeling of collisionless plasmas can be divided into two categories: fluid models and kinetic models. Generally speaking, fluid models require less computational resources than kinetic models, so they are suited for large-scale simulations. However, conventional fluid models such as MHD ignores wave-particle interaction (WPI). It has been pointed out that WPI affects microscopic and macroscopic dynamics and should not be ignored even in MHD scales. This creates a demand for a fluid model of collisionless plasma that takes into account WPI effects.

We have developed a fluid model called the cyclotron resonance closure (CRC) model [1]. The CRC model reproduces linear cyclotron resonance effects using a non-local closure method similar to the Landau closure model. The CRC model reproduces the linear cyclotron resonance and linear growth of ion temperature anisotropy instabilities qualitatively correct. We have also shown that the quasilinear relaxation of temperature anisotropy via resonant waves incorporated in the CRC model.

 Another example of a kinetic fluid model is the well-known Chew-Goldberger-Low (CGL) model. The CGL model is used to analyze low-frequency waves in collisionless plasmas. The CGL model enriched by finite Larmor radius correction and Landau closure predicts the growth rate of firehose instability with reasonable accuracy. However, the CGL model cannot reproduce cyclotron resonance effects such as cyclotron damping and electromagnetic ion cyclotron (EMIC) instability because of the low-frequency assumption.

We will discuss some basic concepts of these kinetic fluid models and their range of application, especially in nonlinear simulation. The CRC model is not limited by frequency (at least up to cyclotron frequency) and can be used for both EMIC and parallel firehose instabilities but need improvement for quantitative agreement with fully kinetic models.

The CGL model can be very accurate in linear analysis of low-frequency waves. We compared the CRC and the CGL model using a simulation of an initially parallel firehose unstable system [2]. We found that the low-frequency approximation of the CGL model fails in some parameters after the appearance of high-frequency oscillation in the nonlinear stage. Also, the absence of cyclotron damping in the CGL model results in a quasi-steady final state that is not consistent with marginal stability analysis.

We conclude that a kinetic fluid model that does not make the low-frequency approximation should be considered instead of the CGL-based approach. The CRC model is a candidate for such a model that can be used in a wide range of parameters.

 

[References]

1. T. Jikei and T. Amano (2021), A non-local fluid closure for modeling cyclotron resonance in collisionless magnetized plasmas, Physics of Plasmas, 28, 042105

2. T. Jikei and T. Amano (2022), Critical comparison of collisionless fluid models: Nonlinear simulations of parallel firehose instability, Physics of Plasmas, Accepted

How to cite: Jikei, T. and Amano, T.: Fluid modeling of collisionless plasmas with a non-local kinetic closure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3345, https://doi.org/10.5194/egusphere-egu22-3345, 2022.

EGU22-3911 | Presentations | ST1.1

Flux tube dependent propagation of Alfvén waves in the solar corona 

Chaitanya Prasad Sishtla, Jens Pomoell, Emilia Kilpua, Simon Good, Farhad Daei, and Minna Palmroth
Alfvén wave turbulence has emerged as an important heating mechanism to accelerate the solar wind. The generation of this turbulent heating is dependent on the presence and subsequent interaction of counter-propagating alfvén waves. This requires us to understand the propagation and evolution of alfvén waves in the solar wind in order to develop an understanding of the relationship between turbulent heating and solar wind parameters. In this paper we aim to study the  response  of  the  solar  wind  upon  injecting  monochromatic  single frequency alfvén waves at the base of the corona for various magnetic flux tube geometries. We use an ideal magnetohydrodynamic (MHD) model using an adiabatic equation of state. An alfvén pump wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components. The alfvén waves were found to be reflected due to the development of the parametric decay instability (PDI). Further investigation revealed that the PDI was suppressed both by efficient reflections at low frequencies as well as magnetic flux tube geometries.

How to cite: Sishtla, C. P., Pomoell, J., Kilpua, E., Good, S., Daei, F., and Palmroth, M.: Flux tube dependent propagation of Alfvén waves in the solar corona, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3911, https://doi.org/10.5194/egusphere-egu22-3911, 2022.

EGU22-4064 | Presentations | ST1.1

Mating of two current circuits – A new type of plasma instability 

Gerhard Haerendel

In the context of the onset of substorms, observations had revealed the frequent occurrence of an unidentified trigger process. Inspections of such onsets had led to the discovery that high-beta plasma at the magnetosphere-tail boundary became suddenly unstable when so-called auroral streamers lined up closely with that boundary. The manifestation was the appearance of bead-like auroral structures preceding the auroral breakup and subject to nonlinear growth. Highly resolved video coverage of a few events showed that the fast moving beads moved opposite to the convective motions on either side. This led to the proposal [Haerendel & Frey 2021] that the trigger of the instability was the formation of a new current circuit, by a non-MHD process, in the gap between the two adjacent circuits of the high-beta plasma boundary and the auroral streamer. Observational evidence and a model of the current structure will be presented.

How to cite: Haerendel, G.: Mating of two current circuits – A new type of plasma instability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4064, https://doi.org/10.5194/egusphere-egu22-4064, 2022.

EGU22-4892 | Presentations | ST1.1 | Highlight

The 3D Dynamics of Solar Flare Magnetic Reconnection 

Spiro Antiochos, Joel Dahlin, and Richard DeVore

Solar eruptive events (SEE) consisting of a massive filament eruption, intense X-class flare, and a fast CME are the most powerful manifestations of explosive energy release in our solar system and the primary drivers of highly destructive space weather at Earth and in interplanetary space. These giant events, which have global scale of solar radii, allow us to study in great detail fundamental space plasma processes such as magnetic reconnection that are important to many cosmic phenomena. Both 2.5D and 3D numerical simulations have shown that the fast energy release is due to reconnection in a large-scale current sheet that forms in the corona, but the 3D dynamics of the reconnection are far from understood.  The greatest challenge to understanding SEEs is their extreme rate of energy release, and for some events, the amazing efficiency at converting magnetic energy into high-energy particle energy. We present new ultra-high-resolution 3D simulations of flare reconnection using the adaptive-mesh-refinement code ARMS. We find that the reconnection dynamics are dominated by 3D magnetic islands, and show that the islands should have clear observational signatures, especially in the so-called flare ribbons that are commonly observed in the chromosphere. We discuss the central role of the islands for understanding the multiscale coupling at the heart of reconnection, the fast energy release rate, and the high efficiency of particle acceleration.

 

This work was supported by the NASA Living With a Star Program and by the NASA DRIVE Center Program.

 

How to cite: Antiochos, S., Dahlin, J., and DeVore, R.: The 3D Dynamics of Solar Flare Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4892, https://doi.org/10.5194/egusphere-egu22-4892, 2022.

EGU22-5498 | Presentations | ST1.1

Simulating the FIP effect in coronal loops using a multi-species kinetic-fluid model. 

Nicolas Poirier, Michael Lavarra, Alexis Rouillard, Pierre-Louis Blelly, Victor Réville, Andrea Verdini, Marco Velli, Eric Buchlin, and Mikel Indurain

We investigate abundance variations of heavy ions in coronal loops. We develop and exploit a multi-species model of the solar atmosphere (called IRAP’s Solar Atmospheric Model: ISAM) that solves for the transport of neutral and charged particles from the chromosphere to the corona. We investigate the effect of different mechanisms that could produce the First Ionization Potential (FIP) effect. We compare the effects of the thermal, friction and ponderomotive force. The propagation, reflection and dissipation of Alfvén waves is solved using two distinct models, the first one from Chandran et al. (2011) and the second one that is a more sophisticated turbulence model called Shell-ATM. ISAM solves a set of 16-moment transport equations for both neutrals and charged particles. Protons and electrons are heated by Alfvén waves, which then heat up the heavy ions via collision processes. We show comparisons of our results with other models and observations, with an emphasis on FIP biases. This work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189.

How to cite: Poirier, N., Lavarra, M., Rouillard, A., Blelly, P.-L., Réville, V., Verdini, A., Velli, M., Buchlin, E., and Indurain, M.: Simulating the FIP effect in coronal loops using a multi-species kinetic-fluid model., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5498, https://doi.org/10.5194/egusphere-egu22-5498, 2022.

EGU22-5546 | Presentations | ST1.1 | Highlight

A simulation of flare-driven coronal rain 

Wenzhi Ruan, Yuhao Zhou, and Rony Keppens

Coronal rains are cool materials (~10,000 K) that appear at hot corona. They are frequently observed in non-flaring loops of active regions and recently observed in flaring loops at gradual phases. Hot coronal loops (~10 MK) are often produced in flare events due to magnetic reconnection. The hot flare loops gradually recover to typical coronal temperature due to thermal conduction and radiative loss, during which condensation can happen due to thermal instability. Here we demonstrate how the rains formed in a flare loop with a two-and-a-half dimensional magnetohydrodynamic simulation. We simulate a flare event from pre-flare phase all the way to gradual phase and successfully reproduce coronal rains. We find that thermal conduction and radiative losses alternately dominate the cooling of the flare loop. We find that runaway cooling and rain formation also induce the appearance of dark post-flare loop systems, as observed in extreme ultraviolet (EUV) channels.

How to cite: Ruan, W., Zhou, Y., and Keppens, R.: A simulation of flare-driven coronal rain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5546, https://doi.org/10.5194/egusphere-egu22-5546, 2022.

EGU22-5633 | Presentations | ST1.1

Electron cyclotron maser model of solar radio zebras 

Jan Benáček and Marian Karlický
Solar radio zebras, occurring as fine structures in radiograms during Type IV bursts, are an excellent tool for plasma diagnostics during solar flares. The main model of zebras is the electron cyclotron maser instability based on double plasma resonance between electron cyclotron and plasma frequencies and an unstable wave in the presence of an unstable type of velocity distribution is necessary, e.g., a loss-cone. The radio emission occurs in the electromagnetic Z-mode along the magnetic field or at the first harmonic of the X-mode in the perpendicular direction. However, it is still unclear where and how the instability evolves and how the locally captured electrostatic waves are converted to escaping radio waves. To obtain the instability evolution, we calculated its growth rates and saturation energies as functions of cyclotron-to-plasma frequency ratio, loss-cone density, cold background  temperature, hot electron thermal velocity, and loss-cone angle by using analytical calculations and particle-in-cell simulations. We found that the growth rates and saturation energies form maxima, approximately located at the harmonic numbers of cyclotron frequency. The maxima shift to lower frequencies with increasing the plasma temperature, they broaden and decrease with increasing the harmonic number. We also estimated electromagnetic energy densities in the emission region and the conversion efficiency to the radio waves.

How to cite: Benáček, J. and Karlický, M.: Electron cyclotron maser model of solar radio zebras, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5633, https://doi.org/10.5194/egusphere-egu22-5633, 2022.

Ubiquitous small-scale vortical motions in the solar atmosphere are thought to play an important role in local heating of the quiet chromosphere and corona. However, an unambiguous method for their detection in observations and numerical simulations has not been found yet.
We aim at developing a robust method for the automated identification of vortices. Local and global rotations in the flow should be considered as both are necessary for the detection of coherent vortical structures. Moreover, the use of a threshold should be avoided to not exclude slow vortices in the identification process.
We present a new method that combines the rigor of mathematical criteria and the global perspective of morphological techniques. The core of the method is the estimation of the center of rotation for every point that presents some degree of local rotation in the flow. For that, we employ the Rortex criterion and the morphology of the neighboring velocity field. We then identify coherent vortical structures by clustering the estimated centers of rotation.
The application of the method to synthetic velocity fields demonstrates its reliability and accuracy. A first statistical study is performed on realistic numerical simulations of the solar atmosphere carried out with the radiative magneto-hydrodynamical code CO5BOLD. We counted on average 0.8 Mm-2 swirls in the photosphere and 1.9 Mm-2 at the bottom of the chromosphere. The average radius varies between 59 km and 72 km. Compared to previous studies, our analysis reveals more and smaller vortical motions in the simulated solar atmosphere. Moreover, we find that 84 % of the swirls in the photosphere show twists in the magnetic field lines compatible with torsional Alfvén waves. 

How to cite: Canivete Cuissa, J. R. and Steiner, O.: An innovative and automated vortex identification method based on the estimation of the center of rotation with application to solar simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5744, https://doi.org/10.5194/egusphere-egu22-5744, 2022.

EGU22-6060 | Presentations | ST1.1

Coronal rain in randomly heated arcades 

Xiaohong Li, Rony Keppens, and Yuhao Zhou

Adopting the MPI-AMRVAC code, we present a 2.5-dimensional magnetohydrodynamic simulation, which includes thermal conduction and radiative cooling, to investigate the formation and evolution of the coronal rain phenomenon. We perform the simulation in initially linear force-free magnetic fields that host chromospheric, transition-region, and coronal plasma, with turbulent heating localized on their footpoints. Due to thermal instability, condensations start to occur at the loop top, and rebound shocks are generated by the siphon inflows. Condensations fragment into smaller blobs moving downwards, and as they hit the lower atmosphere, concurrent upflows are triggered. Larger clumps show us clear coronal rain showers as dark structures in synthetic EUV hot channels and as bright blobs with cool cores in the 304 Å channel, well resembling real observations. Following coronal rain dynamics for more than 10 hr, we carry out a statistical study of all coronal rain blobs to quantify their widths, lengths, areas, velocity distributions, and other properties. The coronal rain shows us continuous heating–condensation cycles, as well as cycles in EUV emissions. Compared to the previous studies adopting steady heating, the rain happens faster and in more erratic cycles. Although most blobs are falling downward, upward-moving blobs exist at basically every moment. We also track the movement of individual blobs to study their dynamics and the forces driving their movements. The blobs have a prominence-corona transition-region-like structure surrounding them, and their movements are dominated by the pressure evolution in the very dynamic loop system.

How to cite: Li, X., Keppens, R., and Zhou, Y.: Coronal rain in randomly heated arcades, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6060, https://doi.org/10.5194/egusphere-egu22-6060, 2022.

EGU22-6120 | Presentations | ST1.1 | Highlight

Modeling Reconnection and Turbulence in the Magnetosphere on Kinetic Scales 

Wieslaw M. Macek and Szymon Gorka

We consider magnetic turbulence using observations from the Magnetospheric Multiscale (MMS) mission on kinetic (ions and electron) scales, which are far shorter than the scales characteristic for description of plasma by magnetohydrodynamic (MHD) theory. We have shown that a break of the magnetic spectral exponent to about -5.5 agrees with the predictions of kinetic theory (-16/3), see Ref. [1]. It is worth noting that the unprecedented very high (millisecond) resolution of the magnetic field instrument allowed to grasp the mechanism of reconnection in the magnetotail on kinetic scales, Ref. [2]. As expected from numerical simulations, we have verified that when the field lines and plasma become decoupled a large reconnecting electric field related to the Hall current (1–10 mV/m) is responsible for fast reconnection in the ion diffusion region both at the magnetopause and in the magnetotail regions. Although inertial accelerating forces remain moderate (1–2 mV/m), the electric fields resulting from the divergence of the full electron pressure tensor provide the main contribution to the generalized Ohm’s law at the neutral sheet (of the order of 10 mV/m), cf. [3]. This illustrates that when ions decouple electron physics dominates. The results obtained on kinetic scales may be useful for better understanding the physical mechanisms governing reconnection processes in various magnetized space and laboratory plasmas.

Acknowledgments. This work has been supported by the National Science Center, Poland (NCN), through grant No. 2021/41/B/ST10/00823.

References

1. Macek, W. M., Krasinska, A., Silveira, M. V. D., Sibeck, D. G., Wawrzaszek, A., Burch, J. L., & Russell, C. T. 2018, Magnetospheric Multiscale observations of turbulence in the magnetosheath on kinetic scales, Astrophys. J. Lett., 864, L29, https://doi.org/10.3847/2041-8213/aad9a8.

2. Macek, W. M., Silveira, M. V. D., Sibeck, D. G., Giles, B.L., & Burch, J. L. 2019a, Magnetospheric Multiscale mission observations of reconnecting electric fields in the magnetotail on kinetic scales, Geophys. Res. Lett., 46, 10,295—10,302, https://doi.org/10.1029/2019GL083782.

3. Macek, W. M., Silveira, M. V. D., Sibeck, D. G., Giles, B.L., & Burch, J. L. 2019, Mechanism of reconnection on kinetic scales based on Magnetospheric Multiscale mission observations, Astrophys. J. Lett., 885, L26, https://doi.org/10.3847/2041-8213/ab4b5a.

 

How to cite: Macek, W. M. and Gorka, S.: Modeling Reconnection and Turbulence in the Magnetosphere on Kinetic Scales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6120, https://doi.org/10.5194/egusphere-egu22-6120, 2022.

EGU22-6171 | Presentations | ST1.1

Two-fluid numerical model towards reproducing the observed solar wave cutoffs. 

Błażej Kuźma, Kris Murawski, and Zdzisław Musielak

With use of JOANNA code we developed a numerical model that describes a partially ionized plasma described by a set of two-fluid equations for ion + electron and neutral fluids, coupled by ion-neutral collisions. We used this model to simulate a quiet region of the solar atmosphere with granules spontaneously generated in the photosphere by the underlying solar convective motions. We found that such ongoing granulation excites a wide range of waves propagating into the upper atmospheric layers, with their cutoff frequencies strongly depending on height above the photosphere. We report for the first time numerically obtained cutoff frequencies that are consistent with the cutoff frequencies computed by Stark & Musielak (1993), Kraśkiewicz et al. (2019) and Wójcik et al. (2019). What is even more important, our results remain in agreement with the observational data of Wiśniewska et al. (2016) and Kayshap et al. (2018). As the exact analytical formula for two-fluid cutoff frequencies has not been found up to date, the numerical simulations are crucial tool to answer the ongoing question about impact of different physical processes on cutoffs and their variation in the solar atmosphere.

How to cite: Kuźma, B., Murawski, K., and Musielak, Z.: Two-fluid numerical model towards reproducing the observed solar wave cutoffs., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6171, https://doi.org/10.5194/egusphere-egu22-6171, 2022.

EGU22-6875 | Presentations | ST1.1 | Highlight

Data-Driven MHD Simulations on Magnetic Flux Rope Eruptions 

Yang Guo, Mingde Ding, Pengfei Chen, Chun Xia, Rony Keppens, Ze Zhong, Jinhan Guo, and Yiwei Ni

Solar eruptions such as flares and coronal mass ejections could cause disastrous space weather. To understand and predict these eruptive activities, we have to combine multi-wavelength observations and numerical simulations. Recently, data-driven magnetohydrodynamic (MHD) simulations have provided a series of new findings in studying the accumulation of electric current and magnetic energy in active regions, in explaining magnetic flux rope eruptions and coronal mass ejections. We briefly review the progress in this field and introduce one way to realize data-driven MHD simulation, including processing magnetic field observational data, inversion of velocity field and electric field, models as initial conditions and subsequent dynamic simulations. Finally, we will look into the future of the data-driven simulations and point out several methods to improve the simulation results. 

How to cite: Guo, Y., Ding, M., Chen, P., Xia, C., Keppens, R., Zhong, Z., Guo, J., and Ni, Y.: Data-Driven MHD Simulations on Magnetic Flux Rope Eruptions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6875, https://doi.org/10.5194/egusphere-egu22-6875, 2022.

EGU22-7233 | Presentations | ST1.1

Three-dimensional particle-in-cell simulation of high-speed plasma jets interacting with Mercury’s magnetosphere 

Gabriel Voitcu, Marius Echim, Eliza Teodorescu, and Costel Munteanu

The transport of high-speed plasma jets (or clouds, streams, blobs, plasmoids) across magnetic discontinuities/shocks is a key process for planetary magnetic environments. Recently, a large number of localized magnetic structures detected in-situ by MESSENGER in the Hermean magnetosheath has been reported in the literature. These structures are similar to the high-speed plasma jets identified in the Earth’s magnetosheath. Due to some limitations in the plasma measurements on-board MESSENGER, only the magnetic signature has been studied. The BepiColombo mission provides a great opportunity to further advance this type of investigation. In this paper we use 3d3v electromagnetic particle-in-cell simulations to study the transport and entry of high-speed plasma jets into Mercury’s magnetosphere. The physical setup is adapted to simulate the kinetic effects and their role on the dynamics of localized plasma structures propagating from the magnetosheath toward the Hermean magnetopause. The magnetospheric field of planet Mercury is provided by the KT17 model, while the high-speed plasma jets are defined as 3D finite-size elements with their bulk velocity pointing towards the dayside magnetopause. We investigate the space and time evolution of the plasma jets prior, during and after their impact on the Hermean magnetopause. We analyse the parallel and perpendicular dynamics with respect to the background magnetic field and emphasize key physical processes for the propagation of high-speed plasma jets across transverse magnetic fields. Our simulations shall support the future exploitation of in-situ data from BepiColombo.

How to cite: Voitcu, G., Echim, M., Teodorescu, E., and Munteanu, C.: Three-dimensional particle-in-cell simulation of high-speed plasma jets interacting with Mercury’s magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7233, https://doi.org/10.5194/egusphere-egu22-7233, 2022.

EGU22-7377 | Presentations | ST1.1

Similarity and difference of Alfvén waves' propagation and evolution in the slow and fast solar wind of inner heliosphere 

Jiansen He, Liping Yang, Die Duan, Xingyu Zhu, and Chuanpeng Hou
Parker Solar Probe detected the Alfvénic slow solar wind in the inner heliosphere. Before that, although different spacecraft had measured that slow solar wind sometimes has Alfvénic characteristics, they did not attract extensive and strong attention and discussion. The critical question is, how does the propagation and evolution of Alfvénic waves perform through the same or different processes in the fast and slow solar wind? To study this problem, we simulate the formation of high and low-speed solar wind and the propagation of evolving Alfvén waves therein from a global perspective. Compared with one-dimensional or multi-dimensional simulations with a limited range of latitude and longitude, the advantage of global simulation is that it provides a self-consistent model of fast and slow solar wind coexisting in different flow tubes. Based on this model, we study and evaluate the effects of the expansion, bending, and non-uniformity across the flux tube on the propagation of evolving Alfvén wave. The varying characteristics during the propagation consist of wave amplitude, wave-vector anisotropy, wave mode conversion, etc. As the critical interface to distinguish the sub-Alfvénic and super-Alfvénic solar wind, which is also the vital interface to distinguish the corona and interplanetary space, Alfvén surface is another important aspect of our research. We study the propagation characteristics of Alfvén waves inside and outside the non-spherical interface. In addition, we also discuss the possible relationship between the propagation and evolution of the Alfvén wave and the formation and development of switchback.

How to cite: He, J., Yang, L., Duan, D., Zhu, X., and Hou, C.: Similarity and difference of Alfvén waves' propagation and evolution in the slow and fast solar wind of inner heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7377, https://doi.org/10.5194/egusphere-egu22-7377, 2022.

EGU22-7843 | Presentations | ST1.1

How are the energetics of transverse waves in a coronal loop affected by a transition region? 

Timothy Duckenfield, Gabriel Pelouze, and Tom Van Doorsselaere

Transverse waves of a coronal loop, also known as kink waves, are commonplace in the solar atmosphere, both in their standing and propagating form. Such waves may be important in the energy + mass cycles of the solar corona. Furthermore, recent numerical studies of coronal loops have shown that the plasma heating from dissipation of these waves is sufficient to overcome radiative cooling. However, the addition of a dense mass reservoir at the end(s) of the loop in the form of a chromosphere and transition region can alter the energetics of the wave and its evolution compared to a purely coronal loop.
In this talk, I will outline current progress in 3D MHD simulations of a solar loop incorporating a chromosphere, transition region and coronal component in a stratified, thermally conducting atmosphere. Transverse waves are induced from a driver in the chromosphere, showing these waves are able to penetrate the transition region. This result is important for the decay-less oscillation regime, in which very small amplitude transverse oscillations are seen to persist for many periods, despite the (presumable) action of damping mechanisms such as resonant absorption. The fact that decay-less oscillations may be driven down in the chromosphere supports the notion that decay-less oscillations are powered from below.
When the loop is sufficiently driven, the motion of the coronal plasma leads to small scales generated from Kelvin Helmholtz instability eddies, and these deformations are regions of enhanced heating. I will discuss the simulation results on how the wave energy is dissipated into heat; the relationship between the driver and the heating; and the extent to which the entire loop is heated, and compare with the purely coronal case. 

How to cite: Duckenfield, T., Pelouze, G., and Van Doorsselaere, T.: How are the energetics of transverse waves in a coronal loop affected by a transition region?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7843, https://doi.org/10.5194/egusphere-egu22-7843, 2022.

EGU22-8175 | Presentations | ST1.1 | Highlight

The magnetopause discontinuity: a MMS study. 

Giulio Ballerini, Gerard Belmont, Laurence Rezeau, and Francesco Califano

The magnetopause boundary seems to escape the general classification of discontinuities since it mixes characteristics of shocks (magnetic field magnitude increase) and those typical for the rotational discontinuities (magnetic rotation), whereas it is very often described as a tangential discontinuity. As, the main issue is the amount of matter/momentum/energy from the solar wind and entering into the magnetosphere, the solution cannot be simply achieved by assuming the discontinuity as strictly tangential, everywhere and at all times. Here we propose to study the magnetopause boundary as a "quasi-tangential" discontinuity, with the normal magnetic component Bn small but not null since even small departures from the standard hypothesis of a zero Bn can lead to noticeable changes in the global properties. In that aim, we look into the MMS database for a large number of magnetopause crossings. For each case we will determine what are the most important features (non-planarity, non-stationarity, Hall effect, pressure anisotropy and agyrotropy) that allow the discontinuity to escape the general classification, i.e. to noticeably change the form of the conservation laws on which the theory of discontinuities is based for non-strictly tangential discontinuities. We put a special emphasis on the refined methods that can be used for determining the spatial gradients from four spacecraft data and on the accuracy that can be attained by these methods.

How to cite: Ballerini, G., Belmont, G., Rezeau, L., and Califano, F.: The magnetopause discontinuity: a MMS study., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8175, https://doi.org/10.5194/egusphere-egu22-8175, 2022.

EGU22-8824 | Presentations | ST1.1

Importance of accurate numerical implementaion of electron inertial terms in hybrid-kinetic simulations  of collisionless plasma turbulence 

Neeraj Jain, Patricio A. Muñoz, Jörg Büchner, Meisam Tabriz, and Markus Rampp

A comprehensive understanding of the turbulent dissipation of magnetic energy in collisionless space and astrophysical plasmas, an unsolved problem yet, requires efficient kinetic simulations of collisionless plasma turbulence. Fully kinetic simulations (where all the plasma species, ions and electrons, are treated kinetically) of collisionless plasma turbulence covering a full range of kinetic scales (from ion to electron scales) are computationally demanding.  Hybrid-kinetic simulations (ions treated as kinetic species and electrons as fluid and therefore ignoring electron kinetic effects) with inertia-less electron fluid, although less demanding computationally,  can not address the physics at the electron scales. Hybrid-kinetic simulations with inertial electron fluid are applicable all the way down to electron scales (still ignoring electron kinetic effects) with computational demands in between those for hybrid-kinetic simulations with inertia-less electron fluid and fully kinetic simulations, and, therefore have begun to attract significant interest recently.

The majority of hybrid-kinetic codes, solving either the Vlasov equation for the ions by an Eulerian method (called Vlasov-hybrid codes) or the equations of motion for ion macro-particles by the Lagrangian Particle-in-Cell (PIC) method (called PIC-hybrid codes), numerically implement the electron inertial terms of  the electron fluid equations under varying approximations which are not necessarily valid at electron scales. In hybrid-kinetic codes, electric field is calculated from either the generalized Ohm's law or an elliptic partial differential equation. In the former case, the non-stationary electron inertial term (time derivative of electron bulk velocity) in the generalized Ohm's law is neglected (approximation A1). In the latter case, a part of the electron inertial term involving cross partial derivatives of electric field is  neglected in comparison to the other part involving second order partial derivatives to obtain a simpler elliptic partial differential equation for electric field (approximation A2). For two dimensional collisionless plasma turbulence, we assess the validity of the two approximations of electron inertial terms used in hybrid-kinetic codes for the calculation of electric field. We employ our recently parallelized three-dimensional PIC-hybrid code CHIEF, which numerically implements the electron inertial terms without any of these approximations, in a quasi-two dimensional setup for the simulations of collisionless plasma turbulence.  We find that the approximation A1 impacts the accuracy of the results at the electron scales and therefore may lead to physically incorrect results. Approximation A2, on the other hand, is found to be invalid from ion to electron scales. We conclude that the simulation results obtained using the hybrid-kinetic codes with an approximate numerical implementation of the electron inertial term need to be interpreted with caution.  

How to cite: Jain, N., Muñoz, P. A., Büchner, J., Tabriz, M., and Rampp, M.: Importance of accurate numerical implementaion of electron inertial terms in hybrid-kinetic simulations  of collisionless plasma turbulence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8824, https://doi.org/10.5194/egusphere-egu22-8824, 2022.

EGU22-8919 | Presentations | ST1.1

Modelling the propagation of slow magnetoacoustic waves in a multi-stranded coronal loop 

Krishna Prasad Sayamanthula and Tom Van Doorsselaere

The cross-field thermal structure of a coronal loop is one of the critical parameters useful to distinguish the major heating theories. In a recent study we are able to isolate two thermal components of a coronal loop using observations of propagating slow magnetoacoustic waves in two different temperature channels. In order to properly interpret these observations and identify the actual cross-field thermal structure, we develop multiple three-dimensional magnetohydrodynamic models of coronal loop. In each of these models slow magnetoacoustic waves are driven by perturbing the plasma at one end and the corresponding multi-wavelength propagation characteristics are studied by applying forward modelling techniques. We compare the wave propagation properties between different models including a monolithic and a multi-stranded model with those from observations to draw some important inferences which will be discussed in this talk.

How to cite: Sayamanthula, K. P. and Van Doorsselaere, T.: Modelling the propagation of slow magnetoacoustic waves in a multi-stranded coronal loop, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8919, https://doi.org/10.5194/egusphere-egu22-8919, 2022.

EGU22-10585 | Presentations | ST1.1 | Highlight

Properties of cosmic ray test particles in global MHD simulation of the heliosphere 

Shuichi Matsukiyo, Kotaro Yoshida, Haruichi Washimi, and Tohru Hada

Heliosphere is a bubble occupied by the solar wind plasma and magnetic field in the local interstellar space. The motion of galactic cosmic rays (GCRs) invading into the heliosphere are strongly affected by the electromagnetic structures of the heliosphere. The statistical behavior of the GCRs near and inside the heliosphere have been conventionally studied by many authors using the diffusion convection model [e.g., Moraal (2013)].

  In this study we investigate the behavior of GCRs invading into the heliosphere in the level of particle trajectory. We conduct test particle simulations of GCRs by using the electromagnetic fields obtained from a global MHD simulation of the heliosphere. The MHD simulation assumes steady solar wind and interstellar wind. GCR protons are initially distributed outside the heliosphere and their motions in the steady virtual heliosphere are calculated by using the Buneman-Boris method. Depending on their initial energy, various types of particle motions, current sheet drift, polar drift, spiral motion, shock drift, Fermi-like acceleration, linear motion, resonantly scattered motion, mirror reflection by bottleneck interstellar field, are observed. We further discuss some statistics of the particles reached at the inner boundary (=50AU from the sun) of the simulation domain.

How to cite: Matsukiyo, S., Yoshida, K., Washimi, H., and Hada, T.: Properties of cosmic ray test particles in global MHD simulation of the heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10585, https://doi.org/10.5194/egusphere-egu22-10585, 2022.

The solar wind has historically been considered as a far simpler medium than the solar or magnetospheric plasma. From the beginning of the space era through to XXI century, it has been supposed that all solar wind structures freely expand and can be modeled in 2D. Correspondingly, current sheets have been pictured as thin planar objects carrying the electric current and separating magnetic fields of different directions. Before 2010th, Petscheck magnetic reconnection was considered as the only possible mechanism transforming the magnetic energy into the thermal energy at current sheets in the solar wind. Acceleration of particles to suprathermal energies was thought to be impossible there because of too slow inflow speeds. Interpretations of observations totally followed the theoretical dominant paradigm mainly because of the insufficiency of observational material. Things began to change when more and more theoretical and observational studies in magnetospheric and solar physics appeared pointing to the complex character of magnetic reconnection. In particular, ideas about stochastic or turbulent reconnection at current sheets in realistic space plasmas become dominating. In turn, observations of the fine structure of current sheets in the solar wind as well as evidence for local acceleration of energetic particles found with help of modern missions, including Parker Solar Probe, allow re-considering views on solar wind current sheets and better understanding physics of the processes associated with magnetic reconnection.   

How to cite: Khabarova, O.: Magnetic reconnection and particle acceleration in the solar wind: theory, observations and opinions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10641, https://doi.org/10.5194/egusphere-egu22-10641, 2022.

EGU22-10807 | Presentations | ST1.1 | Highlight

Homologous Coronal Mass Ejections Caused by Recurring Formation and Disruption of Current Sheet within a Sheared Magnetic Arcade 

Chaowei Jiang, Xinkai Bian, and Xueshang Feng

The Sun often produces coronal mass ejections with similar structure repeatedly from the same source region, and how these homologous eruptions are initiated remains an open question. Here, by using a new magnetohydrodynamic simulation, we show that homologous solar eruptions can be efficiently produced by recurring formation and disruption of coronal current sheet as driven by continuously shearing of the same polarity inversion line within a single bipolar configuration. These eruptions are initiated by the same mechanism, in which an internal current sheet forms slowly in a gradually sheared bipolar field and reconnection of the current sheet triggers and drives the eruption. Each of the eruptions does not release all the free energy but with a large amount left in the post-flare arcade below the erupting flux rope. Thus, a new current sheet can be more easily formed by further shearing of the post-flare arcade than by shearing a potential field arcade, and this is favorable for producing the next eruption. Furthermore, it is found that the new eruption is stronger since the newly formed current sheet has a larger current density and a lower height. In addition, our results also indicate the existence of a magnetic energy threshold for a given flux distribution, and eruption occurs once this threshold is approached.

How to cite: Jiang, C., Bian, X., and Feng, X.: Homologous Coronal Mass Ejections Caused by Recurring Formation and Disruption of Current Sheet within a Sheared Magnetic Arcade, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10807, https://doi.org/10.5194/egusphere-egu22-10807, 2022.

EGU22-10833 | Presentations | ST1.1 | Highlight

Can the ultraviolet bursts be generated in the low solar chromosphere? 

Lei Ni

Ultraviolet (UV) bursts and Ellerman bombs (EBs) are small scale magnetic reconnection events in the highly stratified low solar atmosphere. The plasma density, reconnection mechanisms and radiative cooling/transfer process are very different at different atmospheric layers. EBs are believed to form in the up photosphere or low chromosphere. It is still not clear whether UV bursts have to be generated at a higher atmospheric layer than the EBs or UV bursts and EBs can actually both appear in the low chromosphere.   We numerically studied the low beta magnetic reconnection process around the solar temperature minimum region (TMR) by including more realistic physical diffusions and radiative cooling models. We aim to find out if UV bursts can be formed in the low chromosphere and investigate the dominant mechanism that transfer the magnetic energy to heat in an UV burst.The single-fluid MHD code NIRVANA was used to perform simulations. The time dependent ionization degrees of Hydrogen and Helium are included in the code, which lead to the more realistic magnetic diffusion caused by electron-neutral collision and ambipolar diffusion. The more realistic radiative cooling model from Carlsson& Leenaarts 2012 is included in the simulations. The high resolution simulation results indicate that the plasmas in the reconnection region can be heated above 20,000 K as long as the reconnection magnetic fields reach above 500 G, which further proves that UV bursts can be generated in the dense low chromosphere. When the reconnection magnetic fields are stronger than 900 G, the width of the synthesized Si IV 1394 A line profile with multiple peaks can reach above 100 km s-1, which is consistent with the usually observed broad-line-width UV bursts. The dominate mechanism that converts magnetic energy to heat in an UV burst in the low chromosphere is Joule heating that is contributed by magnetic diffusion caused by electron-ion collision in the reconnection region. The average power density that is converted to the thermal energy in the reconnection region is about 100 erg cm-3 s-1, which is comparable to the average power density of the released heat in an UV burst.

 

How to cite: Ni, L.: Can the ultraviolet bursts be generated in the low solar chromosphere?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10833, https://doi.org/10.5194/egusphere-egu22-10833, 2022.

EGU22-10945 | Presentations | ST1.1

Doppler shifts of spectral lines formed in the solar transition region and corona 

Yajie Chen, Hardi Peter, Damien Przybylski, Hui Tian, and Jiale Zhang

Emission lines formed in the transition region and corona show dominantly redshifts and blueshifts, respectively. We investigate the Doppler shifts in a 3D radiation magnetohydrodynamic (MHD) model of the quiet Sun and compare these to observed properties. We concentrate on Si IV 1394 Å originating in the transition region and examine the Doppler shifts of several other spectral lines at different formation temperatures. We construct a radiation MHD model extending from the upper convection zone to the lower corona using the MURaM code. In this quiet Sun model the magnetic field is self-consistently maintained by the action of a small-scale dynamo alone. We synthesize the profiles of several optically thin emission lines, formed at temperatures from the transition region into the corona. We investigate the spatial structure and coverage of red- and blueshifts and how this changes with line-formation temperature. The model successfully reproduces the observed change of average net Doppler shifts from red- to blueshifted from the transition region into the corona. In particular, the model shows a clear imbalance of area coverage of red- vs. blueshifts in the transition region of ca. 80% to 20%, even though it is even a bit larger on the real Sun. We isolate that (at least) four processes generate the systematic Doppler shifts in our model, including pressure enhancement in the transition region, transition region brightenings unrelated to coronal emission, boundaries between cold and hot plasma, and siphon-type flows. We show that there is not the single process that is responsible for the observed net Doppler shifts in the transition region and corona. Because current 3D MHD models do not yet fully capture the evolution of spicules, one of the key ingredients of the chromosphere, most probably these have still to be added to the list of processes responsible for the persistent Doppler shifts.

How to cite: Chen, Y., Peter, H., Przybylski, D., Tian, H., and Zhang, J.: Doppler shifts of spectral lines formed in the solar transition region and corona, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10945, https://doi.org/10.5194/egusphere-egu22-10945, 2022.

EGU22-11960 | Presentations | ST1.1

A new global nonlinear force-free coronal magnetic-field extrapolation code implemented on a Yin Yang grid. 

Argyrios Koumtzis and Thomas Wiegelmann

The solar magnetic field dominates and structures the
coronal plasma and detailed insights are important to understand almost
all physical processes. While direct routine measurements
of the coronal magnetic field are not available, we have to extrapolate
the photospheric vector field measurements into the corona. To do so,
we developed a new code that performs state-of-the-art nonlinear force-free
magnetic field extrapolations in spherical geometry.
Our new implementation is based on an optimization principle and is
able to reconstruct the magnetic field in the entire corona, including
the polar regions.
Because of the nature of the finite-difference numerical scheme used in
the past, extrapolation close to polar regions was computationally
inefficient. In the current code, the so-called Yin Yang grid is used.
Both the speed and accuracy of the code is improved compared to previous
implementations. We tested our new code with a well known
semi-analytical model (Low and Lou solution). This new Yin and Yang
implementation is timely because
the Solar Orbiter mission is expected to provide reliable
vector magnetograms also in the polar regions within the following years.
Thus, this code can be used in the future when these synoptic magnetograms
are available to model the magnetic field of the solar corona for the entire
Sun including the polar regions.

How to cite: Koumtzis, A. and Wiegelmann, T.: A new global nonlinear force-free coronal magnetic-field extrapolation code implemented on a Yin Yang grid., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11960, https://doi.org/10.5194/egusphere-egu22-11960, 2022.

EGU22-12161 | Presentations | ST1.1 | Highlight

Excitations of Alfven Wave by 3D Patchy and Intermittent Magnetic Reconnection 

Liping Yang, Jiansen He, Xueshang Feng, and Ming Xiong

Alfven waves make a central role in energy transfer of the solar atmosphere and heliosphere, with the potential to heat corona, accelerate solar wind, and drive Alfvenic turbulence. It has long been suggested that magnetic reconnection can generate Alfven waves through a relaxation of a highly curved reconnected field lines. Here, with a high-resolution simulation of 3D magnetic reconnection under the solar corona environment, we study this sketch and find that Alfven waves, whose features resemble to those of the Alfven Waves observed in the solar atmosphere, are continually and energetically excited by reconnection mainly through two ways. One involves the current sheet which experiences patchy and intermittent reconnections, and the other refers to the turbulence forming in the outflow regions. The Pointing flux carried by the excited upward-propagating Alfven waves can satisfy the requirements of plasma heating in the corona. This has implications for self-consistent considerations of energy budgets in the solar atmosphere and heliosphere.

How to cite: Yang, L., He, J., Feng, X., and Xiong, M.: Excitations of Alfven Wave by 3D Patchy and Intermittent Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12161, https://doi.org/10.5194/egusphere-egu22-12161, 2022.

EGU22-12196 | Presentations | ST1.1

On the evolution equations of field gradient tensor invariants in MHD Theory 

Virgilio Quattrociocchi, Giuseppe Consolini, Massimo Materassi, Tommaso Alberti, and Ermanno Pietropaolo

The understanding of the evolution of turbulence in space plasmas requires the investigation of magnetic field and plasma structures and their time evolution. Indeed, the interactions among different topological multi scale structures have been shown to play an important role tu understand the energy transfer across scales and dissipation. A possible approach to this issue is the study of the geometrical invariants of magnetic and velocity field gradient tensors from a Lagrangian point of view. In the early 1980 a series of works (Vielliefosse, 1982 and 1984) discussed a nonlinear homogeneous evolution equation for the velocity gradient tensor in fluid dynamics.  Here, we derive the evolution equations of the geometrical invariants of the magnetic and velocity field gradient tensors in the case of magneto-hydrodynamic theory and discuss their application to the analysis of magneto-hydrodynamic turbulence in space plasmas.

How to cite: Quattrociocchi, V., Consolini, G., Materassi, M., Alberti, T., and Pietropaolo, E.: On the evolution equations of field gradient tensor invariants in MHD Theory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12196, https://doi.org/10.5194/egusphere-egu22-12196, 2022.

EGU22-12533 | Presentations | ST1.1

MHD wave modes of solar magnetic flux tubes with the realistic cross-section 

Anwar Aldhafeeri, Viktor Fedun, Istvan Ballai, and Gary Verth

 

Current and near-future high resolution solar observations indicate that theoretical modelling of the magnetohydrodynamic (MHD) modes in magnetic waveguides with realistic structure and shape now becomes an imperative necessity. 

It was recently shown that even a magnetic structure with elliptical shape, that corresponds to the weak irregularity, may significantly influence the spatial structure of MHD mode in comparison to the mode structure obtained from the modelling which is based on the magnetic flux tube shape with cylindrical cross-section (Aldhafeeri et al., ApJ, 2021). An inaccurate model used for describing waves may lead to the misinterpretation of observational data. 

The expressions for the linear MHD perturbations of a magnetic flux tube are derived by assuming zero value of the vertical component of the velocity perturbation at the boundary of the magnetic flux tube, which is in good agreement with observations. The governing equation for the vertical velocity perturbation was solved by taking into account the observed realistic shape of the sunspot umbra. With these conditions the proposed model is applicable for the analysis of slow body modes under photospheric conditions. 

Our results show that under solar photospheric conditions the conditions of continuity of the component of radial velocity and pressure at the boundary are enough to be imposed, enabling us to use Cartesian coordinates with varsity numerical methods to model the MHD modes with their realistic cross-sectional shape.

 

How to cite: Aldhafeeri, A., Fedun, V., Ballai, I., and Verth, G.: MHD wave modes of solar magnetic flux tubes with the realistic cross-section, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12533, https://doi.org/10.5194/egusphere-egu22-12533, 2022.

EGU22-12904 | Presentations | ST1.1

Three-dimensional Particle-in-Cell (PIC) simulations of non-dipolar minimagnetospheres and comparison to the experiment. 

Andrey Divin, Ildar Shaikhislamov, Igor Paramonik, Marina Rumenskikh, Daniil Korovinskiy, and Jan Deca

Magnetospheres are formed when plasma flow interacts with an external source of the magnetic field. Objects (with a size comparable to or less than the ion inertial length or ion gyroradius) formed by relatively weak magnetic field sources are called minimagnetospheres since they are rather different from more common large planetary magnetospheres. 

Moon surface has regions called Lunar Magnetic Anomalies (LMAs) where the remanent magnetization of the Lunar crust provides sources of the magnetic field strong enough to stand off the solar wind. These fields produce minimagnetospheres of the size of the several ion inertial lengths (or gyroradii) or below, typically having weakly structured topology and mostly non-dipolar nature. In this study, we combine numerical simulations and laboratory experiments to investigate ion scattering and basic properties of a non-dipolar minimagnetosphere.  A series of laboratory experiments were carried out on the KI-1 facility (Novosibirsk, Russia) to investigate minimagnetosphere properties for the case of a quadrupolar magnetic field source. The experiment consists of a vacuum chamber, of 5 m length and 1.2 m diameter (with a residual pressure of ~10-7 Torr) filled with a moving plasma. The quadrupolar magnetic field is generated by two coils connected in anti-parallel. The experimental results are supported by the Particle-in-Cell (PIC) three-dimensional simulations using code iPIC3D which capture the full kinetic behavior of the interaction. 

We report several important results based on both the experiment and numerical simulations: 1) a majority of particles is reflected by the Hall electric field formed due to the formation of the magnetopause electron current; however, a hotter portion of the inbound distribution also experiences magnetic deflection closer to the B field source; 2) reflecting electrostatic potential is smaller in the quadrupolar case (if compared to dipolar minimagnetosphere); 3) numerical simulations reproduce well the ion reflection pattern seen in the laboratory experiment, but simulations show slightly less reflected ions which might be attributed to unsteady processes developing during each laboratory run.

How to cite: Divin, A., Shaikhislamov, I., Paramonik, I., Rumenskikh, M., Korovinskiy, D., and Deca, J.: Three-dimensional Particle-in-Cell (PIC) simulations of non-dipolar minimagnetospheres and comparison to the experiment., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12904, https://doi.org/10.5194/egusphere-egu22-12904, 2022.

EGU22-915 | Presentations | NP6.3

Quantifying the electron scattering by electrostatic fluctuations in the Earth’s bow shock 

Sergey Kamaletdinov, Ivan Vasko, Anton Artemyev, and Rachel Wang

Collisionless shocks are known to be natural sources of suprathermal particles, but the mechanism resulting in acceleration of thermal electrons to suprathermal energies still remains elusive. The problem is, that the Diffusive Shock Acceleration (DSA) becomes efficient only for suprathermal electrons, which fluxes in the far upstream region are relatively low. Recent studies have shown that the so-called Stochastic Shock Drift Acceleration (SSDA) mechanism can potentially provide the necessary pre-acceleration of incoming thermal electrons to suprathermal energies. In this mechanism, electrons are temporarily kept trapped in the shock transition region due to magnetic mirror reflection by the magnetic ramp and pitch-angle scattering of electrons trying to escape upstream by wave turbulence. Spacecraft measurements showed that broadband electrostatic turbulence is always present in the Earth’s bow shock, but its efficiency in scattering suprathermal electrons has not been estimated up to date. In this study we have quantified the electron scattering by the broadband electrostatic turbulence and, specifically, by electrostatic solitary waves (ion holes) substantially contributing to this turbulence in the Earth’s bow shock. Adopting the solitary wave and turbulence parameters typical of the Earth’s bow shock, we obtain quasi-linear scattering rates and compare these scattering rates to the results of test-particle simulations. This analysis showed that scattering of suprathermal electrons by the osberved electrostatic turbulence is relatively well estimated by the quasi-linear approach. We estimated the quasi-linear scattering rates at various energies and pitch-angles and demonstrated that the electrostatic turbulence in the Earth’s bow shock can provide pre-acceleration of thermal electrons from a few tens of eV to a few hundred eV via the SSDA mechanism.

This work was supported by the Russian Scientific Foundation, Project No. 19–12-00313

How to cite: Kamaletdinov, S., Vasko, I., Artemyev, A., and Wang, R.: Quantifying the electron scattering by electrostatic fluctuations in the Earth’s bow shock, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-915, https://doi.org/10.5194/egusphere-egu22-915, 2022.

EGU22-1485 | Presentations | NP6.3

Plasmoid-dominated turbulent reconnection in symmetric and asymmetric systems 

Seiji Zenitani, Momoka Yamamoto, and Takahiro Miyoshi

In magnetohydrodynamics (MHD), magnetic reconnection has been discussed by three theoretical models: Sweet--Parker reconnection, Petschek reconnection, and plasmoid-dominated turbulent reconnection. Among these models, properties of plasmoid-dominated reconnection remain unclear, because it was discovered only recently. In this talk, we explore basic properties of plasmoid-dominated reconnection in a low-beta plasma such as in a solar corona, by using large-scale MHD simulations [1]. We have found that the system becomes highly complex due to repeated formation of plasmoids and shocks. We have further found that the reconnection rate goes higher than previously thought. Next we explore influence of asymmetry in background plasma densities in plasmoid-dominated reconnection. We have found that the average reconnection rate follows Cassak-Shay's hybrid relation [2]. Many signatures become asymmetric across the reconnection layer, and plasmas inside the plasmoids start to swirl in specific directions. Formation processes of these vortices and a potential extension of our numerical survey will be discussed.

References:
[1] S. Zenitani and T. Miyoshi, Astrophys. J. Lett., 894, L7 (2020)
[2] P. A. Cassak and M. A. Shay, Phys. Plasmas, 14, 102114 (2007)

How to cite: Zenitani, S., Yamamoto, M., and Miyoshi, T.: Plasmoid-dominated turbulent reconnection in symmetric and asymmetric systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1485, https://doi.org/10.5194/egusphere-egu22-1485, 2022.

EGU22-1577 | Presentations | NP6.3

Physical Regimes of 2D MHD turbulent reconnection in different Lundquist numbers 

Haomin Sun, Yan Yang, Quanming Lu, San Lu, Minping Wan, and Rongsheng Wang

Using two-dimensional (2D) MHD simulations in different Lundquist numbers , we investigate physical regimes of turbulent reconnection and the role of turbulence in enhancing the reconnection rate. Turbulence is externally injected into the system with varying strength. External driven turbulence contributes to the conversion of magnetic energy to kinetic energy flowing out of the reconnection site and thus enhances the reconnection rate. The plasmoids formed in high Lundquist numbers contribute to the fast reconnection rate as well. Moreover, an analysis of the power of turbulence implies its possible association with the generation of plasmoids. Additionally, the presence of turbulence has great impact on the magnetic energy conversion and may be favorable for the Kelvin-Helmholtz (K-H) instability in the magnetic reconnection process.

How to cite: Sun, H., Yang, Y., Lu, Q., Lu, S., Wan, M., and Wang, R.: Physical Regimes of 2D MHD turbulent reconnection in different Lundquist numbers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1577, https://doi.org/10.5194/egusphere-egu22-1577, 2022.

EGU22-1740 | Presentations | NP6.3

Local slope of magnetic field power spectrum in inertial and kinetic ranges of solar wind turbulence 

Alexander Pitna, Jana Safrankova, Zdenek Nemecek, Gilbert Pi, Luca Franci, and Byeongseon Park

Solar wind, a supersonic flow of plasma embedded in the magnetic field, exhibits turbulent behavior. The character of turbulent fluctuations has been investigated through low cadence measurements of particle distribution function and high cadence magnetic field measurements. One of the most frequently adopted approach in the analysis of the ‘measured’ time series of any particular quantity is the estimation of its power spectral density (PSD). The shape of the PSD then may infer which physical mechanisms govern the evolution of turbulent fluctuations. Generally, every ‘measured’ time series is ‘noisy’ and it differs from the ‘true’ one (measured by an ideal instrument). In turn, the shape of PSD is affected as well. In this paper, we focus on a special case where the signal and noise are independent, i.e., the noise is additive and therefore, the PSD of measured signal can be expressed as a sum of ‘true’ and ‘noise’ PSDs. Moreover, we define a so-called local slope in the framework of continuous wavelet transform as the finite difference derivative between the two consequent values of a global PSD. Employing this technique, we show that the noise of magnetic field measurements of the MFI instrument on board the Wind spacecraft is additive. Finally, we applied the technique to measurements of the Parker Solar Probe close to the Sun. Our preliminary results suggest that our technique may lead to a more accurate estimations of the kinetic range spectral indices.

How to cite: Pitna, A., Safrankova, J., Nemecek, Z., Pi, G., Franci, L., and Park, B.: Local slope of magnetic field power spectrum in inertial and kinetic ranges of solar wind turbulence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1740, https://doi.org/10.5194/egusphere-egu22-1740, 2022.

The measurements of the longitudinal velocity were performed in an open-circuit suction wind tunnel installed at the laboratory of the Max-Planck Institute for Dynamics and Self-Organization in Gottingen, using hot wire anemometer at different positions in turbulent flow generated by a traditional fractal square grid (FSG) and by a spaced fractal square grid (SFSG) with similar physical properties have shown that the self-similarity is present. The statistical description of this complex turbulent system was performed using Extended Self Similarity (ESS). We propose a complementary methodology suitable for non-homogeneous turbulence based on the analysis of the energy transfer hierarchy. The signature of the non-homogeneous characteristics of a turbulent field, indicated by nonlocal dynamics, is separated from those usually assigned as being only due to the intermittency. We propose a physical interpretation of the observed scale independence of the relative scaling exponents in such non-homogeneous flows by means of the compensation effect of the energy transfer on the difference between the strong coherent turbulent events and the background less intense turbulence. This procedure is able to distinguish whether the intermittency arises from the small scales or is linked to coherent structures. The practical interest of this type of turbulent excitation concerns several fields of aeronautical and space application and energy or environmental problems of noise reduction of mixers in combustion or for the numerical models of prediction of the dispersion of pollutants in the atmosphere.

How to cite: Ben Mahjoub, O. and Ouadoud, A.: Intermittency in turbulence generated by traditional fractal square grid and spaced fractal square grid, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1997, https://doi.org/10.5194/egusphere-egu22-1997, 2022.

Turbulence, the self-generated turbulence by plasmas and magnetic field collective interaction, has been found to play an essential role in energizing charged particles in the large-scale reconnecting current sheet in the major solar eruption.

The typical large-scale CME/Flare events involve sudden bursts of particle acceleration from the sudden release of magnetic energy in a few minutes to a few tens of minutes. The X-rays emission and gamma rays burst produced by the combined result from the interactions of electrons, hydrogen, helium, and other heavier ions. Space and laboratory researchers are more inclined to believe that turbulence acceleration is belonged to shock acceleration. Solar and astrophysics researchers are more inclined to believe that turbulence acceleration is an independent acceleration mechanism that belongs to the flare acceleration. The evidence in both theories and observations from solar atmosphere activities shows that the acceleration is related to nonlinear resonant wave-particle interaction (e.g., Landau acceleration). So far, many-particle acceleration models consider turbulence acceleration as an effective way of generating energetic electrons, protons, and heavier ions. However, the detailed role of turbulence in this process remains unclear. More effort needs to invest in looking into particle accelerations by turbulence that occurs over a large range of the scale in space from the inertial scale of individual particles to the MHD scale.

In this work, applying the statistical treatment of plasma physics, combing with filter theory of turbulence, the actual ratio of the proton mass to the electron mass, and mass-to-charge ratios, we investigate the interaction of charged particles with the turbulent electric field and magnetic field in the large-scale CME/flare current sheet by applying the

We found the significant Langmuir turbulence acceleration (LTA) through the nonlinear resonant wave-particle interaction in the diffusion region via tracking the trajectories and analyzing the energy spectrum of energetic protons and electrons. The results show that protons and electrons could be efficiently accelerated simultaneously and that the way of LTA is similar to that of the shock acceleration}} but is much more efficient than the shock acceleration. This indicates that large-scale reconnection is a good candidate for the mechanism for the efficient acceleration of protons and electrons in the major solar eruption.

The acceleration of heavy ion considered Helium (3He/4He) and other heavy elements in 3He-rich flares burst would explore in the follow-up work series.

URL: https://pan.cstcloud.cn/s/drEdcjIaT8E

How to cite: Zhu, B., Li, Y., and Lin, J.: Investigations of Particle Accelerations by Turbulent Magnetic Reconnection in Large-Scale CME/Flare Current Sheet: I. Protons and Electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2116, https://doi.org/10.5194/egusphere-egu22-2116, 2022.

EGU22-2649 | Presentations | NP6.3

Electromagnetic energy conversion by various processes in turbulent plasmas observed by MMS 

Thanapon Aiamsai, Peera Pongkitiwanichakul, Rungployphan Kieokaew, David Ruffolo, and Theerasarn Pianpanit

A key issue in space plasma physics is how electromagnetic energy is converted to plasma particle energy and heat. Electromagnetic energy conversion generally involves turbulence and/or instabilities. With the Magnetospheric Multiscale (MMS) mission data, we investigate such energy conversion in turbulent plasmas, separating the plasma currents from various drift motions and other processes and assessing their contributions. For example, we have explored the roles of curvature drift, gradient drift, particle inertia drift and perpendicular magnetization currents. We will discuss their roles and related mechanisms in turbulent plasmas. This research has been supported in part by grant RTA6280002 from Thailand Science Research and Innovation, by DPST scholarship grant ,and by grant RGNS 63-045 from Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation.

How to cite: Aiamsai, T., Pongkitiwanichakul, P., Kieokaew, R., Ruffolo, D., and Pianpanit, T.: Electromagnetic energy conversion by various processes in turbulent plasmas observed by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2649, https://doi.org/10.5194/egusphere-egu22-2649, 2022.

EGU22-3198 | Presentations | NP6.3

Instabilities and Turbulence in Two-Dimensional Magnetohydrodynamics 

Jonathan Tessier, Francis J. Poulin, and David W. Hughes

The solar tachocline is a dynamically important thin region in the Sun, located between the convective and radiative zones and characterised by strong shear in both the radial and latitudinal directions. Furthermore, it is believed to play a key role in the solar dynamo process through the shearing of a poloidal field into a stronger toroidal component. Motivated by the dynamics of the tachocline we have conducted a detailed numerical exploration of the dynamics of sheared MHD turbulence.

Specifically, we have implemented a parallelized numerical model using the "shenfun" Python library to solve the nonlinear two-dimensional Magnetohydrodynamic (MHD) equations to study the dynamics of unstable jets and turbulence in astrophysical plasmas. In particular, we study details of how the jet becomes unstable and the resulting cascade of energy in the case of MHD turbulence. In addition to studying the evolution of the physical quantities, we also investigate the evolution of the spectral slopes and spectral fluxes. As has been found in previous studies of MHD turbulence, a very weak large-scale magnetic field can play a key dynamical role through its amplification on small scales. For extremely weak fields, the behaviour is essentially hydrodynamic. However, once the field is dynamic, the nature of the resulting MHD solution is very different. We are able to classify the various flows and quantify the nature of the solutions in the two regimes.

How to cite: Tessier, J., Poulin, F. J., and Hughes, D. W.: Instabilities and Turbulence in Two-Dimensional Magnetohydrodynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3198, https://doi.org/10.5194/egusphere-egu22-3198, 2022.

EGU22-3354 | Presentations | NP6.3

High-Speed Jets in Earth’s Magnetosheath Downstream of the Quasi-Parallel Shock: A Two-Dimensional Global Hybrid Simulation 

Jin Guo, San Lu, Quanming Lu, Yu Lin, Xueyi Wang, Yufei Hao, Kai Huang, Rongsheng Wang, and Xinliang Gao

High-speed jets (HSJs) occur frequently in Earth’s magnetosheath downstream of the quasi-parallel bow shock. They have great impacts on the magnetosheath and the magnetosphere. Using a two-dimensional global hybrid simulation, we investigate the formation and evolution of the HSJs with an IMF cone angle of 0°. The quasi-parallel shock is near the subsolar point, and the HSJs begin to appear in the quasi-parallel magnetosheath with a parallel (perpendicular) scale size of about 1RE (0.2RE). These HSJs then converge, leading to the formation of a large-scale HSJ with a parallel (perpendicular) scale size of 6RE (1.2RE). Some long HSJs, with a large parallel but small perpendicular scale size, are formed at the quasi-parallel bow shock and extend toward the quasi-perpendicular magnetosheath along with the background magnetosheath flow. Moreover, these long HSJs can cause filamentary structures in the magnetosheath.

How to cite: Guo, J., Lu, S., Lu, Q., Lin, Y., Wang, X., Hao, Y., Huang, K., Wang, R., and Gao, X.: High-Speed Jets in Earth’s Magnetosheath Downstream of the Quasi-Parallel Shock: A Two-Dimensional Global Hybrid Simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3354, https://doi.org/10.5194/egusphere-egu22-3354, 2022.

EGU22-3546 | Presentations | NP6.3

Overshoot dependence on the shock parameters 

Natalia Borodkova, Olga Sapunova, Victor Eselevich, Georgy Zastenker, and Yury Yermolaev

The structure of the solar wind plasma flow downstream of the ramp of the interplanetary and bow shocks was studied based on the BMSW plasma spectrometer installed onboard the SPEKTR-R spacecraft. Particular attention was paid to the overshoot region, where correlated oscillations of the ion flux and magnetic field are observed. They are formed by two populations of ions: the inflowing solar wind and the beam of coherent gyrating ions. Based on the statistical analysis it was shown that overshoots form both in supercritical and subcritical shocks. It is found that maximum values of the overshoot amplitudes are significantly influenced by the angle between the shock normal and magnetic field vectors, Mach number, plasma and magnetic compression at the shock front. It was established that the oscillation wavelength determined from the magnetic field measurements onboard the WIND spacecraft, on average, coincides with the oscillation wavelength determined from the ion flux on the SPEKTR-R, while the rates of relaxation of these oscillations can greatly differ. It was also shown that the estimates of the overshoot wavelength good correlate with the convected ion gyroradius.

How to cite: Borodkova, N., Sapunova, O., Eselevich, V., Zastenker, G., and Yermolaev, Y.: Overshoot dependence on the shock parameters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3546, https://doi.org/10.5194/egusphere-egu22-3546, 2022.

Previous numerical works on electron/ion foreshocks observed upstream of a curved shock have been already performed within a self-consistent approach based on 2D PIC simulation (Savoini et Lembege, 2010, 2013, 2015), but are restricted to a supercritical regime only. Present two dimensional PIC (Particle in cell) simulations are used in order to analyze the features of a curved shock and associated foreshocks in a subcritical regime. In order to investigate the dynamic of each electron and ion backstreaming populations, we used test-particles in a pre-computed electromagnetic field (issued from 2D PIC simulations) which allows us to define precisely the characteristic of each population in terms of initial velocity and/or their upstream position to the  θBn angle (angle between the local shock normal and the interplanetary magnetic field IMF). Then, results allow to clarify the following questions: what is the impact of the subcritical regime (i) on the persistence of each electron/ion foreshock respectively ?, (ii) in the case the persistence is confirmed,  how the location (along the curved front) and the angular direction of each foreshock edge are affected ?, and (iii) how the mapping of upstream local  distribution functions are impacted ? Preliminary results will be presented and compared with those already obtained for a supercritical shock.

How to cite: Savoini, P. and Lembege, B.: Analysis of a curved shock front microstructures and associated electron/ion foreshock for a subcritical shock regime, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3631, https://doi.org/10.5194/egusphere-egu22-3631, 2022.

EGU22-3868 | Presentations | NP6.3

Model of KAW contribution to cross-magnetopause ion transport 

Alexander Lukin, Anton Artemyev, and Anatoly Petrukovich

Magnetosheath ion transport across the night-side magnetopause can be contributed by ion cross-field diffusion due to wave-particle scattering. In this presentation we focus on such scattering mechanism for the most intense magnetosheath wave emission, kinetic Alfven waves (KAWs). These waves carry a finite field-aligned electric field and potentially can accelerate particles along magnetic field lines. In the fast plasma flows these waves are usually observed as a wide Doppler-shifted electromagnetic spectrum characterized by strong electric fields in high wave-number range. Dense frequency spectrum leads to overlapping of particles resonances with waves and causes particle diffusion in pitch-angle and energy space. We investigate particles diffusion caused by interactions with KAW turbulence in a realistic model of the Earth flank magnetopause with nonuniform ambient magnetic field fitting the tangential discontinuity. The KAW spectrum is determined by a sum of a several thousand plane waves with different frequencies and propagation angles. We estimate diffusion coefficients as function of ion pitch-angle and energy for different distances from the magnetopause and discuss the expected cross-field transport rate for this model.

How to cite: Lukin, A., Artemyev, A., and Petrukovich, A.: Model of KAW contribution to cross-magnetopause ion transport, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3868, https://doi.org/10.5194/egusphere-egu22-3868, 2022.

EGU22-4040 | Presentations | NP6.3

Spectral features and energy cascade of kinetic scale plasma turbulence 

Giuseppe Arrò, Francesco Califano, and Giovanni Lapenta

Solar wind (SW) in situ observations of plasma turbulence show that the turbulent magnetic field spectrum follows a Kolmogorov-like scaling ∼k-5/3 at large MHD scales and steepens at ion scales where a different power law develops with a scaling exponent varying between -2 and -4, depending on SW conditions. Recent satellite measurements revealed the presence of a second spectral break around electron scales where the magnetic field spectrum shows an exponential falloff described by the so called exp model ∼k-8/3exp(-ρek), where ρe is the electron gyroradius. This model was tested on a large number of magnetic spectra at various distances from the Sun (from 0.3 to 1 AU) and appears to be a solid feature of turbulent magnetic field fluctuations at kinetic scales [1]. 

Using a fully kinetic energy conserving particle-in-cell (PIC) simulation of freely decaying plasma turbulence we study the spectral properties of the turbulent cascade at kinetic scales. Consistently with satellite observations, we find that the magnetic field spectrum follows the kexp(-λk) law at sub-ion scales, with an exponential range developing around kρe≈1. The same exponential falloff is observed also in the electron velocity spectrum but not in the ion velocity spectrum that drops like a power law without reaching electron scales. We investigate the development of these spectral features by analyzing the high-pass filtered electromagnetic work J·E and pressure-strain interaction -P:∇u of both the ions and the electrons. Our analysis shows that the magnetic field dynamics at kinetic scales is mainly driven by the electrons that are responsible for the formation of the exponential range. In particular, we see that at fully developed turbulence the magnetic field energy is dissipated by a two-stage mechanism lead by the electrons that first subtract energy from the magnetic field and then convert it into internal energy at electron scales through the pressure-strain interaction, that accounts for the electron heating [2].

 

References

[1] Alexandrova, O., Jagarlamudi, V. K., Hellinger, P., Maksimovic, M., Shprits, Y., & Mangeney, A. (2021). Spectrum of kinetic plasma turbulence at 0.3–0.9 astronomical units from the Sun. Physical Review E, 103(6), 063202.

[2] Arrò, G., Califano, F., & Lapenta, G. (2021). Spectral properties and energy cascade at kinetic scales in collisionless plasma turbulence. arXiv preprint arXiv:2112.12753.

How to cite: Arrò, G., Califano, F., and Lapenta, G.: Spectral features and energy cascade of kinetic scale plasma turbulence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4040, https://doi.org/10.5194/egusphere-egu22-4040, 2022.

EGU22-4447 | Presentations | NP6.3

Electron heating scales in quasi-perpendicular shocks 

Andreas Johlander, Andrew Dimmock, Yuri Khotyaintsev, Daniel Graham, and Ahmad Lalti

Collisionless shock waves are important for particle heating and acceleration in space. Electron heating at shocks is a combination of adiabatic heating due to large-scale electric and magnetic fields and scattering by high-frequency oscillations. Electron heating and scattering at the shock is still poorly understood but the scales at which heating happens can hint to which physical processes are taking place. Here, we study electron heating scales with the Magnetospheric Multiscale (MMS) spacecraft at Earth’s quasi-perpendicular bow shock. We utilize the small tetrahedron formation and rapid plasma measurements of MMS to directly measure the electron temperature gradient inside the shock. From this, we reconstruct the electron temperature profile inside the shock ramps of a number of shock crossings with varying shock parameters. We find that most of the electron temperature increase takes place on a scale of tens of electron inertial lengths. Further, we investigate the electron distribution functions and attempt to disentangle the effects of the large-scale adiabatic heating and scattering by high-frequency waves.

How to cite: Johlander, A., Dimmock, A., Khotyaintsev, Y., Graham, D., and Lalti, A.: Electron heating scales in quasi-perpendicular shocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4447, https://doi.org/10.5194/egusphere-egu22-4447, 2022.

EGU22-5068 | Presentations | NP6.3

Measurement of short  (Debye length) scale electrostatic waves with MMS EDP instrument:  Problems and possible mitigation 

Ahmad Lalti, Yuri Khotyaintsev, Daniel Graham, Konrad Steinvall, and Andreas Johlander

High frequency electrostatic oscillations are one of the most fundamental players in energy conversion in collisionless plasmas. Whether at collisionless shocks, turbulence energy cascades or reconnection, small scale Debye length processes  are at the heart of irreversible energy exchange between particles and fields. MMS is one of the most advanced still active spacecraft, with high resolution field and particle instruments. The electric field instrument (EDP) on board of MMS is formed of 3 axial double probes positioned in a perpendicular configuration allowing for the measurement of the 3D electric field. In this study we probe the limitations of the EDP instrument in measuring Debye-scale electrostatic oscillations. In particular we show that at such small wavelengths the electric field is attenuated due to the finite probe-to-probe separation. Furthermore, we propose a method to correct for the electric field attenuation based on the single spacecraft interferometry technique which will allow us to properly determine the observed wave modes.

How to cite: Lalti, A., Khotyaintsev, Y., Graham, D., Steinvall, K., and Johlander, A.: Measurement of short  (Debye length) scale electrostatic waves with MMS EDP instrument:  Problems and possible mitigation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5068, https://doi.org/10.5194/egusphere-egu22-5068, 2022.

EGU22-5192 | Presentations | NP6.3

Identifying active magnetic reconnection in simulations and in situ observations of plasma turbulence using magnetic flux transport 

Tak Chu Li, Yi-Hsin Liu, Yi Qi, and Christopher T. Russell

For decades, magnetic reconnection has been suggested to play an important role in the dynamics and energetics of plasma turbulence by spacecraft observations, numerical simulations and theory. Reliable approaches to study reconnection in turbulence are essential to advance this frontier topic of plasma physics. A new method based on magnetic flux transport (MFT) has been recently developed to identify reconnection activity in turbulent plasmas. Applications to gyrokinetic simulations of two- and three-dimensional (2D and 3D) plasma turbulence, and MMS observations of reconnection events in the magnetosphere have demonstrated the capability and accuracy of MFT in identifying active reconnection in turbulence. In 2D, MFT identifies multiple active reconnection X-lines; two of them have developed bi-directional electron and ion outflow jets, observational signatures for reconnection, while one of the X-line does not have bi-directional electron or ion outflow jets, beyond the category of electron-only reconnection recently discovered in the turbulent magnetosheath. In 3D, plentiful reconnection X-lines are identified through MFT, and a new picture of reconnection in turbulence results. In space, MMS observations have provided first evidence for MFT signatures of active reconnection under varying plasma conditions throughout the Earth's magnetosphere. MFT is applicable to in situ measurements by spacecraft missions, including PSP and Solar Orbiter, and laboratory experiments.

How to cite: Li, T. C., Liu, Y.-H., Qi, Y., and Russell, C. T.: Identifying active magnetic reconnection in simulations and in situ observations of plasma turbulence using magnetic flux transport, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5192, https://doi.org/10.5194/egusphere-egu22-5192, 2022.

EGU22-5222 | Presentations | NP6.3

Fluctuations of the solar wind ion flux near the Earth bow shock 

Olga Sapunova, Natalia Borodkova, Yuri Yermolaev, and Georgii Zastenker

In our study we analyzing fluctuations of the solar wind ion flux associated with the Earth bow shock using data obtained by the BMSW experiment, installed onboard the SPEKTR-R satellite. The high time resolution of the spectrometer (0.031 s for the plasma flux magnitude and direction and 1.5 s for velocity, temperature, and density) makes it possible to study fine structures in detail.

From 2011 to 2019 SPEKTR-R satellite crossed the Earth bow shock many times. In our work we analyzed more than 200 bow shock crossings including multiple ones. More than half of them had fluctuations near the Earth bow shock front.

It was shown that in 25% of events the frequencies of ion flux fluctuations were in the range of 3-4 Hz. In 5-7% of events the frequencies of ion flux fluctuations lay in the interval of 5-6 Hz. Just few cases had frequencies of ion flux fluctuations equal or more than 7 Hz. In other cases the frequencies of ion flux fluctuations were lower than 3 Hz or no fluctuations were observed at all.

We also observed low-frequencies fluctuations about 0.1 Hz and lower. These fluctuations were also visible by the 1.5 s plasma parameters: protons density and velocity; He++ (alpha particles) density and velocity (including helium abundance).

How to cite: Sapunova, O., Borodkova, N., Yermolaev, Y., and Zastenker, G.: Fluctuations of the solar wind ion flux near the Earth bow shock, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5222, https://doi.org/10.5194/egusphere-egu22-5222, 2022.

EGU22-5560 | Presentations | NP6.3

Statistical study of the ripples and reformation in the collisionless shocks using MMS observation 

Ajay Lotekar, Yuri Khotyaintsev, Daniel Graham, Andrew Dimmock, Ahmad Lalti, and Andreas Johlander

Collisionless shocks are ubiquitous throughout the universe in near-Earth and astrophysical plasma environments. The behavior of collisionless shocks in terms of their structure and energy dissipation has been the subject of extensive research over many decades, but many open questions remain. Recent studies have demonstrated that the Earth's bow shock can exhibit ripples that propagate along the shock surface. However, their occurrence, dependence on shock parameters, and their role in shock dynamics is still under investigation. One signature of rippling is the presence of phase space holes in reduced ion distribution (integrated along the tangential plane of the shock). Such ion phase space holes are also observed in association with the shock reformation. It is unclear at what part of the parametric space these ion phase space holes are expected. In this study, we have focused on characterizing ion phase space holes at the Earth’s bow shock using MMS observations. We analyze more than 500 shock crossings observed by the MMS spacecraft and establish a systematic procedure to find the shocks exhibiting phase space holes. We investigate the key shock physical processes responsible for the existence of these phase space holes (e.g. ripples and reformation) and study the association to shock parameters such as Mach number and geometry. We present the first statistical study of this nature, and these results are important to understanding the non-stationary behavior of collisionless shocks. 

How to cite: Lotekar, A., Khotyaintsev, Y., Graham, D., Dimmock, A., Lalti, A., and Johlander, A.: Statistical study of the ripples and reformation in the collisionless shocks using MMS observation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5560, https://doi.org/10.5194/egusphere-egu22-5560, 2022.

EGU22-6084 | Presentations | NP6.3

Suprathermal populations and small scale fluctuations in the solar wind 

Marian Lazar, Rodrigo Lopez, Hamd Shaaban, Stefaan Poedts, Horst Fichtner, and Peter Yoon

In the last decade, studies of solar wind plasma have shown that suprathermal populations (up to a few keV) are closely linked to wave turbulence and fluctuations at small (or kinetic) scales. We aim to identify those types of wave fluctuations observed at these scales scales, for which existing theories predict a major implication in particle acceleration and formation of suprathermal tails in the velocity distributions of plasma particles. On the other hand, it is currently believed that fluctuation power (magnetic, density, velocity) measured at ion scales and lower are generated by the turbulent cascade but also wave instabilities. Therefore, we also intend to discuss a number of recent results describing the kinetic instabilities driven by the anisotropy of velocity distributions (e.g., temperature anisotropy, field-aligned drifts), and how are these instabilities influenced by the suprathermal populations. These results help to understand the energy exchanges between particles and electromagnetic fields, not only in the solar wind but also in the coronal plasma ejections, with consequences for the space weather and terrestrial magnetosphere.

How to cite: Lazar, M., Lopez, R., Shaaban, H., Poedts, S., Fichtner, H., and Yoon, P.: Suprathermal populations and small scale fluctuations in the solar wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6084, https://doi.org/10.5194/egusphere-egu22-6084, 2022.

EGU22-6378 | Presentations | NP6.3 | Highlight

Kinetic signatures of magnetic reconnection in the global hybrid-Vlasov and local particle-in-cell simulations.  

Ivan Zaitsev, Andrey Divin, Urs Ganse, Yann Pfau-Kempf, Markus Battarbee, Markku Alho, Jonas Suni, Maxime Grandin, Lucile Turc, Giulia Cozzani, Maarja Bussov, Maxime Dubart, Harriet George, Konstantinos Horaites, Konstantinos Papadakis, Talgat Manglayev, Vertti Tarvus, Honyang Zhou, and Minna Palmroth

Magnetic reconnection is the energy converter in space plasma that releases magnetic energy into the kinetic energy of particles. We study the magnetotail reconnection in the first 3D global magnetospheric hybrid-Vlasov simulation performed with Vlasiator code. We also performed a simulation of symmetric magnetic reconnection in particle-in-cell technique with the iPIC3D code to compare ion kinetic signatures of reconnection for both hybrid-Vlasov and fully-kinetic approaches. Despite the relatively coarse spatial resolution in the global 3D hybrid-Vlasov model, we are able to recognize the most distinguished reconnection features: ion demagnetization, non-gyrotropic ion acceleration and energy dissipation. Using the well-known signatures of the different subregions of symmetric magnetic reconnection we are able to identify ion diffusion regions, separatrices and reconnection jet fronts in the global simulation. Guided by the measure of the ion perpendicular slippage, we identify ion diffusion regions where ion non-gyrotropic crescent-type distributions are formed. These distinguishable features are nicely visible in the PIC simulation data as well. Separatrix regions are visible as the layers containing the potential Hall electric field at the boundaries of accelerated outflow. Reconnection jet fronts in the global simulation are highlighted at the positions where the energy dissipation peaks. Three-dimensional effects affecting the extending of the reconnection characteristics in the equatorial plane are discussed.

How to cite: Zaitsev, I., Divin, A., Ganse, U., Pfau-Kempf, Y., Battarbee, M., Alho, M., Suni, J., Grandin, M., Turc, L., Cozzani, G., Bussov, M., Dubart, M., George, H., Horaites, K., Papadakis, K., Manglayev, T., Tarvus, V., Zhou, H., and Palmroth, M.: Kinetic signatures of magnetic reconnection in the global hybrid-Vlasov and local particle-in-cell simulations. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6378, https://doi.org/10.5194/egusphere-egu22-6378, 2022.

EGU22-6722 | Presentations | NP6.3

Asymmetric magnetic reconnection between two coalescing flux ropes as squeezed by convergent flows 

Qiaowen Luo, Jiansen He, and Jun Cui

We identify two coalescing flux ropes as squeezed by convergent ion flows near the magnetopause from the MMS observations. According to the electron distributions, we find that one flux rope is closer to the magnetosphere, while the other is closer to the magnetosheath. A current sheet with magnetic field reversal is found to sit at the interface between the two colliding flux ropes, and have magnetic reconnection occurring in the ion diffusion region (IDR). Due to the density asymmetry of flux ropes, the embedded magnetic reconnection event with a significant guide field component shows a large asymmetry in energy conversion across the reconnection site. On the side where the flux rope is closer to the magnetosphere with low density, we find that electrons gained energy from electromagnetic fields resulting in a parallel heating effect. In contrast, ions are found to obtain the energy from electromagnetic fields on the other side of the reconnection current sheet, where the flux rope is near the magnetosheath with high density.

How to cite: Luo, Q., He, J., and Cui, J.: Asymmetric magnetic reconnection between two coalescing flux ropes as squeezed by convergent flows, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6722, https://doi.org/10.5194/egusphere-egu22-6722, 2022.

EGU22-7069 | Presentations | NP6.3

Interplay between magnetic reconnection and flapping instabilities in the magnetotail: global hybrid-Vlasov simulation of the Earth’s magnetosphere 

Giulia Cozzani, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Jonas Suni, Maxime Grandin, Lucile Turc, Ivan Zaitsev, Maarja Bussov, Maxime Dubart, Harriet George, Konstantinos Horaites, Talgat Manglayev, Konstantinos Papadakis, Vertti Tarvus, Honyang Zhou, and Minna Palmroth

Magnetic reconnection is a fundamental process in plasma and a major cause of energy conversion and transport by means of magnetic field topology reconfiguration. It takes place in thin plasma sheets, where energy is often explosively converted from the magnetic field to plasma heating and particle energization. Magnetic reconnection in Earth’s magnetotail is thought to play a crucial role in geomagnetic storms and substorms, one of the most explosive phenomena in the context of Earth’s magnetosphere. Several other current sheet-related processes, such as the ballooning instability, tearing instability, and a variety of flapping instabilities, can occur in the magnetotail, and the interplay between magnetic reconnection and these current sheet instabilities is largely unexplored. In this study, we investigate the interplay between magnetic reconnection and other instabilities taking place in the magnetotail current sheet, using a hybrid-Vlasov simulation that provides a three-dimensional description of the global coupled solar wind-magnetosphere system down to the ion-kinetic scale. In particular, we identify and characterize the flapping instability that develops in the magnetotail midnight sector and we discuss its dynamics in relation to magnetotail magnetic reconnection.

How to cite: Cozzani, G., Ganse, U., Pfau-Kempf, Y., Alho, M., Suni, J., Grandin, M., Turc, L., Zaitsev, I., Bussov, M., Dubart, M., George, H., Horaites, K., Manglayev, T., Papadakis, K., Tarvus, V., Zhou, H., and Palmroth, M.: Interplay between magnetic reconnection and flapping instabilities in the magnetotail: global hybrid-Vlasov simulation of the Earth’s magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7069, https://doi.org/10.5194/egusphere-egu22-7069, 2022.

EGU22-7354 | Presentations | NP6.3

Hybrid-Vlasov simulations of ion velocity distribution functions within Kelvin-Helmholtz vortices 

Vertti Tarvus, Lucile Turc, Hongyang Zhou, Giulia Cozzani, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Markus Battarbee, Maarja Bussov, Maxime Dubart, Harriet George, Maxime Grandin, Konstantinos Horaites, Talgat Manglayev, Konstantinos Papadakis, Jonas Suni, Ivan Zaitsev, and Minna Palmroth

The Kelvin-Helmholtz instability (KHI) is a ubiquitous fluid instability in space plasmas. At the flanks of Earth's magnetopause, the KHI can typically develop during periods of northward interplanetary magnetic field, and it drives the solar wind-magnetosphere mass/energy transfer in the absence of dayside magnetic reconnection. We use local 2D-3V hybrid-Vlasov simulations to study the ion velocity distribution functions (VDFs) associated with the KHI in a magnetopause-like setup. Our results indicate that when the KHI enters the non-linear stage, the ion VDFs in the region perturbed by the instability become increasingly non-Maxwellian. The degree of non-Maxwellianity increases along with the magnitude of the density jump across the KHI boundary. We assess the impact of the non-Maxwellian ion VDFs on the development of the KHI, and compare the simulated VDFs with those observed by the Magnetospheric Multiscale Mission.

How to cite: Tarvus, V., Turc, L., Zhou, H., Cozzani, G., Ganse, U., Pfau-Kempf, Y., Alho, M., Battarbee, M., Bussov, M., Dubart, M., George, H., Grandin, M., Horaites, K., Manglayev, T., Papadakis, K., Suni, J., Zaitsev, I., and Palmroth, M.: Hybrid-Vlasov simulations of ion velocity distribution functions within Kelvin-Helmholtz vortices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7354, https://doi.org/10.5194/egusphere-egu22-7354, 2022.

EGU22-7371 | Presentations | NP6.3

Uniturbulence due to non-linear damping of surface Alfvén waves 

Rajab Ismayilli and Tom Van Doorsselaere

We consider a simple 1-D planar equilibrium model with piece-wise constant density. We completed analytical computations in incompressible MHD. First, we derived mathematical formulas for the wave energy density, the rate of energy dissipation, and the energy cascade damping time. Following that, we developed an analytical model to estimate the damping time for the evolution of uniturbulence in surface Alfvén waves. According to the derived equation, the damping time is inversely proportional to the perpendicular wavenumber and the amplitude of the surface Alfvén waves. Next, we determined the numerical energy dissipation rate using the Fourier transform through numerical simulations. Finally, we approximated the damping time using the fundamental mode of a perpendicular wavenumber.
Consequently, we compared our theoretical model to a series of 3D ideal MHD simulations and observed a remarkable resemblance. The numerical findings demonstrate, in particular, that the damping time is inversely related to the density contrast and amplitude of surface Alfvén waves. Besides, we studied third-order structure-function (Yaglom's law) for Uniturbulence. We compared Yaglom's law (predicted energy dissipation) statistics obtained through simulation with our analytical model. In addition, we estimated the inertial range of the turbulent flow.

How to cite: Ismayilli, R. and Van Doorsselaere, T.: Uniturbulence due to non-linear damping of surface Alfvén waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7371, https://doi.org/10.5194/egusphere-egu22-7371, 2022.

EGU22-8160 | Presentations | NP6.3

Exploring 2.5D magnetic reconnection due to Rayleigh-Taylor induced turbulence in solar prominences 

Madhurjya Changmai and Rony Keppens

The internal dynamics of solar prominences have been observed for many decades to be highly complex, many of which also indicate the possibility of turbulence. Prominences represent large-scale, dense condensations suspended against gravity at great heights within the solar atmosphere. It is therefore of no surprise that the fundamental process of the Rayleigh-Taylor (RT) instability has been suggested as the potential mechanism for driving the dynamics and turbulence remarked upon within observations. We use the open-source MPI-AMRVAC code to construct an extremely high-resolution, 2.5D fully-resistive magnetohydrodynamic model, and employ it to explore the turbulent nature of RT-induced magnetic reconnection processes within solar prominences. The intermittent events of heating and energy dissipation are caused by magnetic reconnection. Furthermore, the strength of the mean magnetic field directed into the 2D plane, and its alignment with the plane itself, creates a system with varying turbulent behaviour. Based on low plasma beta (magnetic pressure dominant) evolution near the chromosphere and a higher value (plasma pressure dominant) evolution within the corona, the stratified numerical model generates different fluctuation statistics. Hence, we find the turbulent dynamics and prominence reconnection events to differ distinctly from those elsewhere within the solar corona.

How to cite: Changmai, M. and Keppens, R.: Exploring 2.5D magnetic reconnection due to Rayleigh-Taylor induced turbulence in solar prominences, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8160, https://doi.org/10.5194/egusphere-egu22-8160, 2022.

EGU22-8705 | Presentations | NP6.3

Fully kinetic simulations of the near-Sun solar wind plasma: turbulence, reconnection, and particle heating 

Luca Franci, Emanuele Papini, Alfredo Micera, Lorenzo Matteini, Julia Stawarz, Giovanni Lapenta, David Burgess, Petr Hellinger, Simone Landi, Andrea Verdini, and Victor Montagud-Camps

We model the development of plasma turbulence in the near-Sun solar wind with high-resolution fully-kinetic particle-in-cell (PIC) simulations, initialised with plasma conditions measured by Parker Solar Probe during its first solar encounter (ion and electron plasma beta ≤ 1 and a large amplitude of the turbulent fluctuations). The power spectra of the plasma and electromagnetic fluctuations are characterized by multiple power-law intervals, with a transition and a considerable steepening in correspondence of the electron scales. In the same range of scales, the kurtosis of the magnetic fluctuations is observed to further increase, hinting at a higher level of intermittency. We observe a number of electron-only reconnection events, which are responsible for an increase of the electron temperature in the direction parallel to the ambient field. The total electron temperature, however, exhibits only a small increase due to the cooling of electrons in the perpendicular direction, leading to a strong temperature anisotropy. We also analyse the power spectra of the different terms of the electric field in the generalised Ohm’s law, their linear and nonlinear components, and their alignment, to get a deeper insight on the nature of the turbulent cascade. Finally, we compare our results with those from hybrid simulations with the same parameters, as well as with spacecraft observations.

How to cite: Franci, L., Papini, E., Micera, A., Matteini, L., Stawarz, J., Lapenta, G., Burgess, D., Hellinger, P., Landi, S., Verdini, A., and Montagud-Camps, V.: Fully kinetic simulations of the near-Sun solar wind plasma: turbulence, reconnection, and particle heating, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8705, https://doi.org/10.5194/egusphere-egu22-8705, 2022.

In supercritical shocks a substantial fraction of ions is reflected at the steep shock ramp. The beam of reflected ions carries a considerable amount of energy and momentum. As a consequence, different plasma populations can co-exist within the same foot region, which constitutes a source of micro-instabilities excited by the relative drifts between incoming ions, reflected ions, and electrons across the ambient magnetic field B. With the help of a spectral periodic 2D PIC code, we investigate the resulting micro-turbulence. Three different waves with different frequency/wave number ranges can be excited simultaneously: Bernstein waves and whistler waves near the lower-hybrid frequency as well as the electron cyclotron frequency. The present work is a 2D extension of a previous analysis (Muschietti et Lembege, Ann. Geophys. 2017) and allows to self-consistently include the mutual interaction between the different instabilities/waves which propagate in different directions with respect to Bo and are at different stages of their respective linear/nonlinear phases. In order to clarify their intricate synergies, a new filtering procedure (low or high pass filter of a given wave number range) has been developed. Taking thus advantage of the spectral nature of the code, we can include/exclude at will the impact of a given instability on the other ones. We have performed several times the simulation with exactly the same initial conditions yet with different filtering ranges. The procedure allows us to illuminate the role played by each instability in the scenario when all are included. Recent results will be presented. 

How to cite: Muschietti, L., Lembege, B., and Decyk, V.: How to define the interplay between different instabilities excited within the foot of a supercritical shock : 2D PIC simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8962, https://doi.org/10.5194/egusphere-egu22-8962, 2022.

The Jovian magnetosphere is loaded internally with material from the volcanic moon of Io, which is ionised and brought into co-rotation forming the Io plasma torus. Plasma is removed from the torus mainly via ejection as energetic neutrals and by bulk transport into sink regions in the outer magnetosphere.

There are two physical processes that are implicated in the bulk transport process, these are diffusion and the radial-interchange (RI) instability. The latter is analogous to the Rayleigh-Taylor instability, but with centrifugal force replacing gravity. This allows magnetic flux tubes containing hot, tenuous plasma to exchange places with tubes containing cool, dense plasma, moving material from the inner to outer magnetosphere whilst returning magnetic flux to the planet. Observational data does not currently provide strong evidence to favour either process and indeed they may be non-linearly coupled. Furthermore, current state-of-the-art simulations do not permit an understanding of non-linear phases of the instability nor the effect of magnetosphere-ionosphere coupling on small length scales.

In order to examine the bulk transport process we have developed a full hybrid kinetic ion, fluid-electron plasma model in 2.5-dimensions, JERICHO. The technique of hybrid modelling allows for probing of plasma motions from the scales of planetary-radii down to the ion-inertial length, considering constituent ion species kinetically as charged particles and forming the electrons into a single magnetised fluid continuum. This allows for insights into particle motions on spatial scales below the size of the magnetic flux tubes. We are particularly interested in exploring a) bulk transport on spatial scales not currently accessible with other state-of-the-art models; b) the relative contributions from diffusive motions against those from RI instabilities; and c) non-linear effects generated by RI instabilities and the impact of these on plasma transport from the inner to outer magnetosphere. In this presentation we will examine the latest simulation results from JERICHO, initialised with a range of Jovian parameters, examining the evolution of the RI instability on differing spatial and temporal scales.

How to cite: Wiggs, J. and Arridge, C.: Examining Radial-Interchange in the Jovian Magnetosphere using JERICHO: a Kinetic-Ion, Fluid-Electron Hybrid Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9788, https://doi.org/10.5194/egusphere-egu22-9788, 2022.

EGU22-9885 | Presentations | NP6.3

MMS bow shock crossings database 

Yuri Khotyaintsev, Ahmad Lalti, Andrew P. Dimmock, Andreas Johlander, and Daniel B. Graham

Identifying collisionless shock crossings in data sent from spacecraft has so far been done manually. It is a tedious job that shock physicists have to go through if they want to conduct case studies or perform statistical studies. We use a machine learning approach to automatically identify shock crossings from the Magnetospheric Multiscale (MMS) spacecraft. We compile a database of those crossings including various spacecraft related and shock related parameters for each event. Furthermore, we show that the shocks in the database have properties that are spread out both in real space and parameter space. We also present a possible science application of the database by looking for correlations between ion acceleration efficiency at shocks and different shock parameters such as the shock geometry and the Mach number.

How to cite: Khotyaintsev, Y., Lalti, A., Dimmock, A. P., Johlander, A., and Graham, D. B.: MMS bow shock crossings database, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9885, https://doi.org/10.5194/egusphere-egu22-9885, 2022.

EGU22-10339 | Presentations | NP6.3

The combined effect of electron and proton firehose instabilities for the solar wind plasma conditions 

Rodrigo A. López, Alfredo Micera, Marian Lazar, Shaaban M. Shaaban, Stefaan Poedts, and Giovanni Lapenta

In the absence of collision, kinetic instabilities triggered by velocity space anisotropies of plasma particles play an essential role in limiting the deviations from isotropy. For example, in the solar wind, firehose instabilities may inhibit the growth of the temperatures in the direction parallel to the background magnetic field, counterbalancing the effect of the expansion. Electron and proton firehose instabilities can be triggered depending on the plasma parameters and the different branches within (periodic and aperiodic). Despite the significant difference between electron and proton spatial and temporal scales, both modes can work together to alter the dynamic of the plasma.
We use a fully kinetic 2D semi-implicit particle-in-cell simulation, iPic3D, to study the evolution and interplay of firehose instabilities triggered by electrons and protons when both species are anisotropic. The aperiodic electron firehose instability remains largely unaffected by the proton anisotropy and saturates rapidly at low-level fluctuations. On the other hand, the presence of anisotropic electrons has a considerable impact on the proton firehose modes, especially on the aperiodic branch, shifting the onset of the instability and boosting the saturation levels of the fluctuations. Anisotropic electrons contribute to more effective regulation of the proton anisotropy.

How to cite: López, R. A., Micera, A., Lazar, M., Shaaban, S. M., Poedts, S., and Lapenta, G.: The combined effect of electron and proton firehose instabilities for the solar wind plasma conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10339, https://doi.org/10.5194/egusphere-egu22-10339, 2022.

EGU22-10688 | Presentations | NP6.3

Multi-Spacecraft Observations of Interplanetary Shocks 

Oksana Kruparova, Vratislav Krupar, and Adam Szabo

Interplanetary (IP) shocks provide us with a unique opportunity to extensively investigate properties of collisionless shocks using in situ measurements under a wide range of upstream conditions. Here we report a case study of several IP shock crossings observed by the Wind, Solar and Heliospheric Observatory (SOHO), Advanced Composition Explorer (ACE), and Deep Space Climate Observatory (DSCOVR) spacecraft. By applying a simple timing method to multipoint measurements, we are able to investigate their characteristic spatiotemporal features. We assume that an IP shock can be represented by a moving plane with a constant velocity, when observed at closely separated points in space and time. We compared IP shock parameters obtained with the timing method with those obtained using the magnetic coplanarity, the mixed mode methods, and Rankine-Hugoniot jump relations.

 

How to cite: Kruparova, O., Krupar, V., and Szabo, A.: Multi-Spacecraft Observations of Interplanetary Shocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10688, https://doi.org/10.5194/egusphere-egu22-10688, 2022.

EGU22-11028 | Presentations | NP6.3

Enernization of Alpha Particles in the Solar Wind Magnetic Reconnection 

Die Duan, Jiansen He, Xingyu Zhu, Rui Zhuo, Ziqi Wu, and Liu Yang
The acceleration and heating of solar wind particles by energy dissipation in the magnetic reconnection is an important problem in space physics. Although alpha particles are the second most abundant element in the solar wind, their dynamical behavior in the magnetic reconnection of the solar wind is not well understood. Using the high energy (1500~3000 eV) part of the SWA/PAS instrument on board the Solar Orbiter, we study the kinetic behavior of alpha particles in a magnetic-reconnetion exhaust region within a heliospheric current sheet. In this event, protons and alpha particles have similar bulk velocities. Alpha particles are accelerated and form a jet in the exhaust region. The counter-stream distribution of alpha particles is observed inside the exhuast region, which changes the direction from parallel to perpendicular to the magnetic field direction when the magnetic field is reversed. In addition, a pair of the slow shock/rotational discontinuity is observed in the exhuast region. The exhaust region is heated and bounded by the slow shocks , while the accelerated plasma jet is bounded by the rotational discontinuities.

How to cite: Duan, D., He, J., Zhu, X., Zhuo, R., Wu, Z., and Yang, L.: Enernization of Alpha Particles in the Solar Wind Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11028, https://doi.org/10.5194/egusphere-egu22-11028, 2022.

EGU22-11524 | Presentations | NP6.3

Turbulence-driven magnetic reconnection and the magnetic correlation length in collisionless plasma turbulence 

Julia E. Stawarz, Jonathan P. Eastwood, Tai Phan, Imogen L. Gingell, Prayash S. Pyakurel, Michael A. Shay, Sadie L. Robertson, Christopher T. Russell, and Olivier Le Contel

Observations of Earth’s magnetosheath from the Magnetospheric Multiscale (MMS) mission have provided an unprecedented opportunity to examine the detailed structure of the multitude of thin current sheets that are generated by plasma turbulence, revealing that a novel form of magnetic reconnection, which has come to be known as electron-only reconnection, can occur within magnetosheath turbulence. These electron-only reconnection events occur at thin electron-scale current sheets and have super-Alfvénic electron jets that can approach the electron Alfvén speed; however, they do not appear to have signatures of ion jets. It is thought that electron-only reconnection can occur when the length of the reconnecting current sheets along the outflow direction is short enough that the ions cannot fully couple to the newly reconnected magnetic field lines before they fully relax. In this work, we examine how the correlation length of the magnetic fluctuations in a turbulent plasma, which constrains the length of the current sheets that can be formed by the turbulence, impacts the nature of turbulence-driven magnetic reconnection. Using observations from MMS, we systematically examine 60 intervals of magnetosheath turbulence – identifying 256 small-scale reconnection events, both with and without ion jets. We demonstrate that the properties of the reconnection events transition to become more consistent with electron-only reconnection when the magnetic correlation length of the turbulence is below ~20 ion inertial lengths. We further discuss the implications of the results in the context of other turbulent plasmas by considering observations of turbulent fluctuations in the solar wind.

How to cite: Stawarz, J. E., Eastwood, J. P., Phan, T., Gingell, I. L., Pyakurel, P. S., Shay, M. A., Robertson, S. L., Russell, C. T., and Le Contel, O.: Turbulence-driven magnetic reconnection and the magnetic correlation length in collisionless plasma turbulence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11524, https://doi.org/10.5194/egusphere-egu22-11524, 2022.

EGU22-11660 | Presentations | NP6.3

Magnetosheath jets at the magnetopause: reconnection onset conditions 

Adrian LaMoury, Heli Hietala, Jonathan Eastwood, Laura Vuorinen, and Ferdinand Plaschke

Magnetosheath jets are localised pulses of high dynamic pressure plasma observed in Earth’s magnetosheath. They are believed to form from the interaction between the solar wind and ripples in Earth’s collisionless bow shock, before propagating into the turbulent magnetosheath. Upon impacting the magnetopause, jets can influence magnetospheric dynamics. In particular, previous studies have suggested that, by virtue of their internal magnetic field orientations, jet impacts may be able to trigger local magnetic reconnection at the magnetopause. This is most notable during traditionally unfavourable solar wind conditions, such as intervals of northward interplanetary magnetic field. This idea has been supported by a small number of case studies and simulations. We present a large statistical study into the properties of jets near the magnetopause. We examine the components of the magnetic reconnection onset condition – the competing effects of magnetic shear angle and plasma beta – to determine how jets may affect magnetopause reconnection in a statistical sense. We find that, due to their increased beta, jet plasma is typically not favourable to reconnection, often more so than the non-jet magnetosheath. Most jets do contain some reconnection-favourable plasma, however, suggesting that jets may be able to both trigger and suppress magnetopause reconnection. We complement this with new case studies of jets interacting with the magnetopause.

How to cite: LaMoury, A., Hietala, H., Eastwood, J., Vuorinen, L., and Plaschke, F.: Magnetosheath jets at the magnetopause: reconnection onset conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11660, https://doi.org/10.5194/egusphere-egu22-11660, 2022.

EGU22-11807 | Presentations | NP6.3 | Highlight

Agyrotropy patterns in 3D small-scall turbulent reconnection 

Jeffersson Andres Agudelo Rueda, Daniel Verscharen, Robert T. Wicks, Christopher J. Owen, Andrew P. Walsh, and Kai Germaschewski
Turbulence and magnetic reconnection are at the core of the long-standing problem of energy dissipation in collisionless plasmas. More than two decades of research on magnetic reconnection have led us to understand the characteristic plasma flows and particle agyrotropy patterns present in collisionless reconnection events. However, it is still not clear what the agyrotropy patterns associated with reconnection events are that form in a turbulent cascade. In this work, we use an explicit fully kinetic particle-in-cell code to study the plasma particles’ agyrotropy associated with three-dimensional small-scale magnetic reconnection events generated by anisotropic and Alfvénic decaying turbulence. We select one reconnection event involving two reconnecting flux ropes. Although we observe similarities with agyrotropy patterns known from two-dimensional steady-state reconnection events, the agyrotropy patterns in our event are more complex. This has further implications for the energy transfer channels available in three-dimensional turbulent reconnection.
 

How to cite: Agudelo Rueda, J. A., Verscharen, D., Wicks, R. T., Owen, C. J., Walsh, A. P., and Germaschewski, K.: Agyrotropy patterns in 3D small-scall turbulent reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11807, https://doi.org/10.5194/egusphere-egu22-11807, 2022.

EGU22-11945 | Presentations | NP6.3 | Highlight

Turbulence modified by velocity shear in coronal mass ejection sheaths 

Juska Soljento, Simon Good, Adnane Osmane, and Emilia Kilpua

Fast coronal mass ejections (CMEs) drive shock waves ahead of them. The turbulent sheath region between the shock and the CME itself contains magnetic field and velocity fluctuations on a broad spectrum of frequencies. In this work we aim to characterise the direction and source of solar wind fluctuations at MHD fluid scales in CME-driven sheaths near Earth. One possible source for these fluctuations is velocity shear, which are common occurrences in CME-driven sheaths. Here we first identify velocity shear as it occurs and then relate that to signatures of new fluctuations being created locally in the sheath. Turbulence parameters such as cross helicity, residual energy, Elsasser ratio, and Alfvén ratio are calculated, and they are correlated against large-scale signatures of velocity shear. Findings indicate a clear association between velocity shear and locally generated fluctuations, as well as a balance in the directionality of these new fluctuations, i.e., they tend to propagate equally towards and away from the Sun. In contrast, most solar wind is typically dominated by anti-sunward fluctuations.

How to cite: Soljento, J., Good, S., Osmane, A., and Kilpua, E.: Turbulence modified by velocity shear in coronal mass ejection sheaths, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11945, https://doi.org/10.5194/egusphere-egu22-11945, 2022.

The kinetic turbulence generated by accelerated particles in a reconnecting current sheet (RCS) with X- and O-nullpoints is considered. The simulations of magnetic reconnection using particle-in-cell (PIC) approach is carried out in a thin current sheet with 3D magnetic field topology affected by tearing instability that leads to a formation of two large magnetic islands . The model utilises a strong guiding field that leads to separation of the particles of opposite charges, generation of a strong polarisation electric field across the RCS and suppression of kink instability in the ’out-of-plane’ direction. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the ‘bump-in-tail’ velocity distributions that, in turn, can generates plasma turbulence in different locations. The turbulence produced by either electron or proton beams is identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains.

The spectral index of the power spectrum In a wavenumber space of the turbulent magnetic field near the ion inertial length approaches -2.7. The collective turbulence power spectra are consistent with the high-frequency fluctuations of perpendicular electric field, or upper hybrid waves, to occur in a vicinity of X-nullpoints, with the Langmuir waves  generated by accelerated electrons which can be converted to  Bernstein waves when electron beams become moving across the magnetic field lines. The frequency spectra of high and low-frequency waves are explored in the kinetic turbulence in parallel and perpendicular directions to the local magnetic field showing noticeable lower hybrid turbulence. The implication of finding for observations is also discussed.

How to cite: Zharkova, V. and Xia, Q.: Kinetic turbulence generated by accelerated particles in a reconnecting current sheet with magnetic islands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12159, https://doi.org/10.5194/egusphere-egu22-12159, 2022.

EGU22-12840 | Presentations | NP6.3

Studying multi-beam ion temperature inside a collisionless reconnection plasmoid by means of Gaussian Mixture Model 

Igor Paramonik, Andrey Divin, Ivan Zaitsev, and Vladimir Semenov

Being ubiquitous energy converter is space plasmas, magnetic reconnection releases stored magnetic energy into kinetic energy of particles. Magnetic reconnection involves several particle acceleration mechanisms which form beams directed parallel to the magnetic field. It was recently demonstrated analytically that in the presence of complicated velocity space structures, the definition of higher moments (like thermal pressure) should be extended to cover such multibeam distributions. In practice, the number of beams at each spatial point of interest is not know a priori. With the aim to automatically reveal the information about the beams generated in the reconnection process, we applied an unsupervised machine learning algorithm (Gaussian Mixture Model, GMM) to the 2.5D Particle-in-Cell simulations of collisionless magnetic reconnection. We studied the ion distributions inside a plasmoid and found that the multibeam ion temperature  within the reconnected outflow deviates significantly from the standard ion temperature (calculated as the 2nd moment of the ion distribution function). In particular, the regions of the strong parallel heating contain in fact relatively cold counterstreaming beams and the overestimation of parallel temperature in this case could be as high as 10. In the current study, we make an attempt to figure out how long the multi-beam regime exists without significant thermalization inside a plasmoid formed by two adjacent X-lines.

How to cite: Paramonik, I., Divin, A., Zaitsev, I., and Semenov, V.: Studying multi-beam ion temperature inside a collisionless reconnection plasmoid by means of Gaussian Mixture Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12840, https://doi.org/10.5194/egusphere-egu22-12840, 2022.

Cosmogenic radionuclides concentrations are predominantly determined by the solar activity and space weather around the Earth, forming an important source of cosmic-origin background radiation in the terrestrial environment. The highest values of such radiation are observed during the solar minima because the penetrability of the Earth’s magnetosphere is greatest at that time. Beryllium 7Be binds to aerosols and is transported within a few years to the Earth’s surface. Its concentrations are higher during the spring and summer months when the stratospheric 7Be penetrates the troposphere as a result of the exchange of air masses between the troposphere and stratosphere. We compare periods of strong solar and geomagnetic storms with periods of very low solar activity in the longitudinal view during the years 1986 – 2020.

For a better understanding of the process dynamics, in our work we investigate the coupling of concentrations of the cosmogenic radionuclide 7Be (time series of activity concentration of 7Be in aerosols) to space weather parameters around the Earth (Kp planetary index, disturbance storm time Dst, proton density, proton flux), proxy parameters of the solar activity (intensity of solar radio flux, relative sunspot number), stratospheric dynamics parameters (temperature, zonal component of wind, O3), and aggregates of strong atmospheric frontal transition. The beryllium radionuclide 7Be concentration was evaluated by the corresponding activity in aerosols on a weekly basis at the National Radiation Protection Institute Monitoring Section in Prague.

We also perform the case study of cosmogenic radionuclide 7Be concentrations during the period of strong solar and geomagnetic storm in November 2021 with the ERA5 reanalysis data, and Aeolus satellite lidar wind measurements.

How to cite: Podolská, K., Kozubek, M., Hýža, M., and Šindelářová, T.: The effect of space weather, proxy parameters of solar activity, and stratospheric phenomena on the concentration of cosmogenic radionuclide 7Be (in the Czech Republic), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4659, https://doi.org/10.5194/egusphere-egu22-4659, 2022.

EGU22-5539 | Presentations | GI6.4

Measurements of cosmic rays by a mini neutron monitor aboard the German research vessel Polarstern. 

Bernd Heber, Sasa Banjac, Sönke Burmeister, Martin Zoska, Hanna Giese, Konstantin Herbst, Lisa Romaneehsen, Carolin Schwerdt, Dutoit Stauss, Carsten Wallmann, Adrian Vogt, and Michael Walter

Galactic cosmic rays (GCRs) consist of energetic electrons and nuclei which are a direct sample of material from far beyond the solar system. Measurements by various particle detectors have shown that the intensity varies on different timescales, caused by the Sun’s activity and geomagnetic variation. Interplanetary disturbances cause space weather effects which warrant a more detailed study. Many studies on GCR intensity decreases is based on the analysis of ground-based neutron monitors and muon telescopes. Their measurements depend on the geomagnetic position, and the processes in the Earth's atmosphere. In order to get a better understanding of the geomagnetic filter over the solar cycle, the Christian-Albrechts-Universität zu Kiel, DESY Zeuthen, and the North-West University in Potchefstroom, South Africa agreed on a regular monitoring of the GCR intensity as a function of latitude, by installing a portable device aboard the German research vessel Polarstern in 2012. The vessel is ideally suited for this research campaign because it covers extensive geomagnetic latitudes (i.e. goes from the Arctic to the Antarctic) at least once per year. Here we present the measurements for different latitude surveys including the periods of solar maximum in 2014 and solar minimum in 2019. 

The Kiel team received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405. The team would like to thank the crew of the Polarstern and the AWI for supporting our research campaign.

How to cite: Heber, B., Banjac, S., Burmeister, S., Zoska, M., Giese, H., Herbst, K., Romaneehsen, L., Schwerdt, C., Stauss, D., Wallmann, C., Vogt, A., and Walter, M.: Measurements of cosmic rays by a mini neutron monitor aboard the German research vessel Polarstern., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5539, https://doi.org/10.5194/egusphere-egu22-5539, 2022.

EGU22-6238 | Presentations | GI6.4 | Highlight

Challenges and solutions for cosmic-ray neutron sensing in heterogeneous soil moisture situations related to irrigation practices 

Cosimo Brogi, Heye Reemt Bogena, Markus Köhli, Harrie-Jan Hendricks Franssen, Olga Dombrowski, Vassilios Pisinaras, Anna Chatzi, Kostantinos Babakos, Jannis Jakobi, Patrizia Ney, and Andreas Panagopoulos

Water availability is a key challenge in agriculture, especially given the expected increase of droughts related to climate change. Soil moisture (SM) sensors can be used to collect information on water availability in a reliable and accurate way. However, due to their very small measuring volume, the installation of multiple sensors is required. In addition, in-situ sensors may need to be removed during field management and connecting cables are often damaged by rodents and other wilderness animals. Hence, the demand for SM sensors that do not have such limitations will increase in the upcoming years. A promising non-invasive technique to monitor SM is cosmic-ray neutron sensing (CRNS), which is based on the negative correlation between fast neutrons originating from cosmic radiation and SM content. With its large measuring footprint of ~130-210m, CRNS can efficiently cover the field-scale. However, heterogeneous agricultural management (e.g., irrigation) can lead to abrupt SM differences, which pose a challenge for the analysis of CRNS data. Here, we investigate the effects of small-scale soil moisture patterns on the CRNS signal by using both modelling approaches and field studies. The neutron transport model URANOS was used to simulate the neutron signal of a CRNS station located in irrigated plots of different sizes (from 1 to 8 ha) with different soil moisture (from 5 and 50 Vol.%) inside and outside such a plot. A total of 400 different scenarios were simulated and the response functions of multiple detector types were further considered. In addition, two CRNS with Gadolinium shielding were installed in two irrigated apple orchards of ~1.2 ha located in the Pinios Hydrologic Observatory (Greece) in the context of the H2020 ATLAS project. Reference soil moisture was determined using 25 SoilNet stations, each with 6 SM sensors installed in pairs at 5, 20 and 50 cm depth and water potential sensors at 20 cm depth. The orchards were also equipped with two Atmos41 climate stations and eight water meters for irrigation monitoring. The CRNS were calibrated using either soil samples or the SM measured by the SoilNet network. In the URANOS simulations, the percentage of neutrons detected by the CRNS that are representative of an irrigated plot varied between 45 and 90% and was strongly influenced by both the dimension and SM of the irrigated plot. As expected, the CRNS footprint decreased considerably with increasing SM but did not appear to be influenced by the plot dimension. SM variation within the irrigated plot strongly affected the neutron energy at detection, which was not the case for SM variations outside the plot. The instrumented fields corroborated the URANOS findings and the performance of the local CRNS was dependent on a) the timing and intensity of irrigation and precipitation, b) the CRNS calibration strategy, and c) the management of the surrounding fields. These results provide novel and meaningful information on the impact of horizontal SM patterns on CRNS measurements, which will help to make CRNS more useful in irrigated agriculture.

How to cite: Brogi, C., Bogena, H. R., Köhli, M., Hendricks Franssen, H.-J., Dombrowski, O., Pisinaras, V., Chatzi, A., Babakos, K., Jakobi, J., Ney, P., and Panagopoulos, A.: Challenges and solutions for cosmic-ray neutron sensing in heterogeneous soil moisture situations related to irrigation practices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6238, https://doi.org/10.5194/egusphere-egu22-6238, 2022.

EGU22-6430 | Presentations | GI6.4

Utilizing Cosmic Ray data as input for neutron-based soil moisture measurement 

Hanna Giese, Bernd Heber, Konstantin Herbst, and Martin Schrön

Neutrons on Earth interact with the soil and are substantially moderated by hydrogen atoms. Since the reflected neutron flux is a function of the soil water content, cosmic-ray neutron measurements above the ground can be used to estimate the average field soil moisture. Thus, if the local incoming neutron flux and the abundance of nearby hydrogen pools are known, the reflected neutron flux could be modeled and compared to observed detector count rates. However, the incoming neutrons are secondaries produced by interacting energetic Galactic Cosmic Rays (GCRs) in the atmosphere. The total neutron flux on the ground depends on the solar modulation-dependent GCR flux, the geomagnetic position, and the altitude within the atmosphere. So far, measurements of either the Jungfraujoch neutron monitor (NM) or a NM of similar cutoff rigidity have been used and altered to estimate the neutron flux at the position of each neutron detector. In this contribution we present a new method based on the Dorman function to directly compute the local neutron flux using remote neutron monitor data.

We received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 870405

How to cite: Giese, H., Heber, B., Herbst, K., and Schrön, M.: Utilizing Cosmic Ray data as input for neutron-based soil moisture measurement, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6430, https://doi.org/10.5194/egusphere-egu22-6430, 2022.

EGU22-8872 | Presentations | GI6.4

Relationship between the time series of cosmic ray data and aerosol optical properties: (Case study: southern Italy, 2016-2020) 

Faezeh Karimian Sarakhs, Fabio Madonna, Marco Rosoldi, and Salvatore De Pasquale

Abstract

High energy Cosmic Ray (CR) particles are capable of ionizing the Earth’s atmosphere, which leads to changes in the atmospheric physical and chemical properties. One of the most important effects of interactions between the CR particles and atmospheric molecules is the formation of aerosol and its subsequent condensation nuclei processes. These interactions are known with considerable uncertainty yet and may translate into even bigger uncertainties in future climate predictions. Laser Detection and Ranging (LIDAR) is currently the best suited technology to retrieve aerosol optical and microphysical properties is also used for the atmosphere correction of high energy cosmic ray observatory data. LIDAR measurements are available from single stations or from networks at continental scale like the European Aerosol Research LIdar NETwork (EARLINET). Sun photometer data are the most suitable complement to LIDAR measurements for the study of aerosol properties due to the extensive coverage of their measurements available through the AErosol RObotic NETwork (AERONET) network. The purpose of this study is to find the correlation between the aerosol properties and the CR data. The aerosol properties retrieved from two databases for the period of 2016-2020: I) the multi-wavelength LIDAR system Potenza EArlinet Raman Lidar (PEARL) which operates at the CNR-IMAA (Tito Scalo (Italy) and contributes to the EAELINET); and II) the AERONET sun photometer data from the stations located at Southern Italy i.e. Potenza (40.60° N, 15.72° E, 820m), Naples (40.83° N, 14.30° E, 50 m) and Lecce (40.33° N, 18.11° E, 30m). whereas, the CR data made available in Italy from the Extreme Energy Events project (http://eee.centrofermi.it/monitor). Air mass back-trajectories were used to confirm the observed aerosol types and support the correlation study. Our study showed promising results in understanding the relationship between cosmic ray and aerosol properties.

Keywords: Cosmic Ray, Aerosol, Lidar, Sun Photometer, Back-trajectory

How to cite: Karimian Sarakhs, F., Madonna, F., Rosoldi, M., and De Pasquale, S.: Relationship between the time series of cosmic ray data and aerosol optical properties: (Case study: southern Italy, 2016-2020), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8872, https://doi.org/10.5194/egusphere-egu22-8872, 2022.

EGU22-9264 | Presentations | GI6.4

Smart Scintillating Neutron Detectors for Soil Moisture Monitoring 

Patrick Stowell and the COSMIC-SWAMP and STFC Food Network+ Collaborations

Cosmic ray neutron sensing has been shown to be a powerful method for continuously monitoring soil moisture over large areas. This technique relies on the detection of albedo cosmic ray neutrons coming from from the soil to infer the local hydrogen content. Cosmic ray neutron sensing is well-suited for hydrological monitoring in the field sizes typically seen on smallholder farms. The ongoing development of new lower-cost neutron detector instrumentation and processing tools will help to further support the adoption of this novel technique within the agricultural industry.

In this presentation I will discuss recent efforts at Durham University (UK) to develop low-cost cosmic ray neutron detectors to support soil moisture monitoring in the agriculture sector. These systems rely on lithium and boron-based scintillator foils for thermal neutron detection. Recent pilot studies in collaboration with the COSMOS-UK network have shown that the detected neutron rate in these sensors correlates well with results obtained from traditional gaseous systems. Work is now underway to improve the robustness of these scintillator systems for use in agricultural and civil engineering applications. 

In addition, I will present a new international research network, COSMIC-SWAMP, which is looking at the integration of cosmic ray neutron sensors with managed irrigation sites in Brazil. By combining low-cost neutron probes with a smart water management platform (SWAMP), this research network is looking at using cosmic ray neutrons to perform data-driven irrigation control over large areas. The instrumentation being considered for COSMIC-SWAMP will be presented before discussing the future plans for the network.

How to cite: Stowell, P. and the COSMIC-SWAMP and STFC Food Network+ Collaborations: Smart Scintillating Neutron Detectors for Soil Moisture Monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9264, https://doi.org/10.5194/egusphere-egu22-9264, 2022.

EGU22-9438 | Presentations | GI6.4

Geomagnetic field shielding over the past 100 000 years 

Monika Korte, Jiawei Gao, and Sanja Panovska

The geomagnetic field prevents energetic particles, such as galactic cosmic rays, from directly interacting with the Earth's atmosphere. The geomagnetic field is not static but constantly changing, and over the last 100,000 years several geomagnetic excursions occurred. During geomagnetic field excursions, the field strength is significantly decreased and the field morphology is controlled by non-dipole components, and more cosmic ray particles can access the Earth's atmosphere. Paleomagnetic field models provide a global view of the long-term geomagnetic field evolution, however, with individual spatial and temporal resolution. Here, we reconstruct the geomagnetic shielding effect over the last 100,000 years by calculating the geomagnetic field cutoff rigidity using four global paleomagnetic field models, i.e., GGF100k, GGFSS70, LSMOD.2, and CALS10k.2. We find that the non-dipole components of the geomagnetic field are not negligible for estimating the long-term geomagnetic shielding effect, in particular during excursions. Our results indicate that cosmic ray flux, impact area, and cosmic ray radiation intensity increase strongly during the excursions. Our results provide the possibility to accurately estimate the cosmogenic isotope production rate and cosmic radiation dose rate covering the last 100,000 years.

How to cite: Korte, M., Gao, J., and Panovska, S.: Geomagnetic field shielding over the past 100 000 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9438, https://doi.org/10.5194/egusphere-egu22-9438, 2022.

EGU22-11230 | Presentations | GI6.4

Space or climate? Disentangling cosmogenic and climatic drivers of present-day tritium (3H) in global precipitation 

Stefan Terzer-Wassmuth, Luis J. Araguas-Araguas, Lorenzo Copia, and Jodie A. Miller

The generation of cosmogenic tritium (3H) through spallation of 14N in the upper atmosphere and a its decay (half-life of 12.32 y) are the two main processes resulting in the global steady-state inventory of tritium in the hydrosphere of approximately 2.95 kg. Various mechanisms of scavenging of stratospheric 3H into the troposphere, such as stratosphere-troposphere transports (STTs) during the so-called “spring leak”, or the tropospheric distribution by means of the Brewer-Dobson circulation, have been described to explain the observed spatial and seasonal distribution of present-day tritium levels in global precipitation. Following thermonuclear weapons testing prior to the Preliminary Test Ban Treaty in 1963, the natural 3H input signal was overlaid by the so-called “bomb peak”. This characteristic tritium pulse has been used for decades in nuclear and hydrological sciences, with 3H values in Vienna, the reference northern hemisphere station of the IAEA-WMO Global Network of Isotopes in Precipitation (GNIP), peaking in 1963 at approximately 400 Bq L-1. Since the year 2000, this 3H pulse has dissipated in the northern hemisphere, and 3H levels at the Vienna monitoring site have reached their natural background value of ca. 1.2 Bq L-1.

The present-day steady state of natural 3H levels in precipitation allow to research their inter-annual variability as driven by cosmogenic input, with particular emphasis on neutron flux intensity governed by the 11-year sunspot cycles. With almost two full solar cycle’s worth of observed 3H data in Vienna’s precipitation and other GNIP stations in the northern hemisphere, we discuss the impact of the neutron flux (as exemplified by the Oulu Neutron Monitor) in modulating the inter-annual variability. Our findings showed that while 52% of the interannual variability was explained by changes in the cosmogenic flux, an additional 31% of the variability resulted from the seasonal distribution of the amount of precipitation, a finding prominent in the previous solar cycle valley, particularly in the year 2015, that coincided with abnormally high winter precipitation.

While the regular oscillations of the neutron flux seem to constitute the main driver of the observed interannual changes of 3H contents in precipitation, atmospheric circulation processes were of varying importance in 15 GNIP stations. In spite of the relative data paucity (i.e. absence of sufficiently long records at even spatial distribution), we hypothesize that changes in precipitation seasonality, due to climate change impacts on global or regional atmospheric circulation patterns, may drive fluctuations in the natural steady-stage 3H levels in precipitation used to investigate atmospheric and hydrological processes. Hence, we stress the importance of spatially and temporally adequate observational baselines on a global level.

How to cite: Terzer-Wassmuth, S., Araguas-Araguas, L. J., Copia, L., and Miller, J. A.: Space or climate? Disentangling cosmogenic and climatic drivers of present-day tritium (3H) in global precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11230, https://doi.org/10.5194/egusphere-egu22-11230, 2022.

EGU22-12334 | Presentations | GI6.4

Rail-based cosmic ray neutron sensing (CRNS): pushing the boundaries towards expanding footprints and temporal resolutions 

Daniel Altdorff, Sascha Oswald, Steffen Zacharias, Carmen Zengerle, Hannes Mollenhauer, Peter Dietrich, Sabine Attinger, and Martin Schrön

Cosmic ray neutron sensing (CRNS) has become an established method for deriving the soil water content (SWC), based on the inverse relationship of neutron counting and the SWC of the surrounding area. The provided footprint, lateral up to 200m and vertical of several decimeter, qualifies CRNS to bridge the information gap between classical hydrogeophysical approaches and remote sensing. While stationary CRNS offers continuous long-term SWC measurements at high temporal resolution, the covered area remains fixed and predefined. Car-borne CRNS roving on the other hand, allows to expand the mapped area. However, the method requires active operation and is limited to snap shot information only. As an alternative, the operation of a permanent mobile CRNS platform on trains promises to combine the advantages from stationary and car-borne CRNS measurements, as recently suggested by Schrön et al. (2021), while also its technical implementation, data processing and interpretation raises new challenges and complexity.

In this study we introduce a fully automatic CRNS railway system, installed in a conventional locomotive of a freight train, as first and novel of its kind. Results of the first phase of operation will be presented. The measurements along an experimental rail track were supported by local SWC measurements, gravimetric and dielectric records (Mobile Wireless Ad-hoc Sensor Network), at three areas along the railway, and by a newly installed weather station. Additionally, car-borne CRNS data were recorded on two days close to the railway track.

Preliminary results of data collected between September and December 2021 showed very stable spatial pattern in relation to the segments crossed by the train, which have been confirmed by the car-borne dataset. Temporal variations within hours were also evident as direct or indirect response to local rain and snow events.  Based on the first results, we are confident, that rail-based CRNS offers the chance to play a prominent role in addressing soil hydrology at landscape scale in the future.

Schrön, M., Oswald, S. E., Zacharias, S., Kasner, M., Dietrich, P., & Attinger, S. (2021). Neutrons on rails: Transregional monitoring of soil moisture and snow water equivalent. Geophysical Research Letters, 48, e2021GL093924

 

How to cite: Altdorff, D., Oswald, S., Zacharias, S., Zengerle, C., Mollenhauer, H., Dietrich, P., Attinger, S., and Schrön, M.: Rail-based cosmic ray neutron sensing (CRNS): pushing the boundaries towards expanding footprints and temporal resolutions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12334, https://doi.org/10.5194/egusphere-egu22-12334, 2022.

Cosmogenic isotopes are mostly produced in the stratosphere and troposphere, and the corresponding fractions depend on solar activity and tropopause altitude. Solar-cycle variability of cosmogenic isotope production is the strongest at high latitudes due to the lack of geomagnetic shielding. However, the exact zonal distribution of the production in troposphere and stratosphere regions, that is needed for the precise modelling of their transport and deposition, is not clear. In this work, we provide numerical estimates of cosmogenic isotopes production in the atmosphere for different conditions. Using the SOCOL-AER2-BE Chemical Climatic model (CCM), we present simulations of the production of cosmogenic isotopes ($^{14}$C, $^{36}$Cl, $^{10}$Be, and $^{7}$Be) and provide zonal distributions (tropical, subtropical, and polar regions) in the stratosphere and troposphere. The model is driven by four solar activity scenarios: 1) solar minimum year with solar modulation function - phi = 400 MeV and 2) solar maxima year with phi = 1100MeV. In these cases, the production is modulated by Galactic Cosmic Rays (GCR). Two other scenarios are 3) ground-level enhancement (GLE) event number 5 with hard spectrum on February 23, 1956 and 4) GLE event number 24 with soft spectrum on August 04, 1972. The production rates were calculated using a combination of the SOCOL and CRAC models.

How to cite: Golubenko, K.: Zonal distribution of cosmogenic isotopes in stratosphere and troposphere via CCM SOCOL, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12618, https://doi.org/10.5194/egusphere-egu22-12618, 2022.

EGU22-12812 | Presentations | GI6.4

Signal contribution of remote areas to cosmic-ray neutron sensors based on distance and sensitivity 

Martin Schrön, Markus Köhli, and Steffen Zacharias

Cosmic-Ray Neutron Sensing (CRNS) is an established measurement technique for water content in soils and snow. The high integration depth and the large measurement footprint is an important advantage compared to conventional point-scale sensors. However, the radial-symmetrical footprint definition based on the 86% quantile of detected neutrons is often not helpful to explain the influence of certain areas in complex fields. Many natural sites are highly heterogeneous and thus knowledge of the contribution of distant areas to the measurement signal would be very useful, e.g. to support calibration sampling, sensor location design, data interpretation, and uncertainty assessment. Here, CRNS calibration and validation remains a challenge, since the influence of the different fields and structures to the signal is usually not known.

In this presentation, we proposes a generalized analytical procedure to estimate the contribution of patches or fields in the footprint of a cosmic-ray neutron detector to its signal using the radial intensity functions. The proposed method could greatly support calibration sampling, sensor location design, and uncertainty assessment, e.g. in complex or vegetated terrain, without the need of computationally expensive neutron modeling. Furthermore, a new concept for a more practical definition of the sensor footprint is proposed, which represents the maximal distance to a field such that its soil moisture change is still sensible in terms of measurement precision. 

How to cite: Schrön, M., Köhli, M., and Zacharias, S.: Signal contribution of remote areas to cosmic-ray neutron sensors based on distance and sensitivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12812, https://doi.org/10.5194/egusphere-egu22-12812, 2022.

EGU22-486 | Presentations | ITS2.1/PS1.2

Enhancing planetary imagery with the holistic attention network algorithm 

Denis Maxheimer, Ioannis Markonis, Masner Jan, Curin Vojtech, Pavlik Jan, and Solomonidou Anezina

The recent developments in computer vision research in the field of Single Image Super Resolution (SISR)

can help improve the satellite imagery data quality and, thus, find application in planetary exploration.

The aim of this study is to enhance planetary surface imagery, in planetary bodies that there are

available data but in a low resolution. Here, we have applied the holistic attention network (HAN)

algorithm to a set of images of Saturn’s moon Titan from the Titan Radar Mapper instrument in its

Synthetic Aperture Radar (SAR) mode, which was on board the Cassini spacecraft. HAN can find

correlations among hierarchical layers, channels of each layer, and all positions of each channel, which

can be interpreted as an application and intersection of previously known models. The algorithm used

in our case-study was trained on 5000 grayscale images from HydroSHED Earth surface imagery dataset

resampled over different resolutions. Our experimental setup was to generate High Resolution (HR)

imagery from eight times lower resolution (x8 scale). We followed the standard workflow for this

purpose, which is to first train the network enhancing x2 scale to HR, then x4 scale to x2 scale, and

finally x8 scale to x4 scale, using subsequently the results of the previous training. The promising results

open a path for further applications of the trained model to improve the imagery data quality, and aid

in the detection and analysis of planetary surface features.

How to cite: Maxheimer, D., Markonis, I., Jan, M., Vojtech, C., Jan, P., and Anezina, S.: Enhancing planetary imagery with the holistic attention network algorithm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-486, https://doi.org/10.5194/egusphere-egu22-486, 2022.

EGU22-692 | Presentations | ITS2.1/PS1.2

Autonomous lineament detection in Galileo images of Europa 

Caroline Haslebacher and Nicolas Thomas

Lineaments are prominent features on the surface of Jupiter's moon Europa. Analysing these linear features thoroughly leads to insights on their formation mechanisms and the interactions between the subsurface ocean and the surface. The orientation and position of lineaments is also important for determining the stress field on Europa. The Europa Clipper mission is planned to launch in 2024 and will fly by Europa more than 40 times. In the light of this, an autonomous lineament detection and segmentation tool would prove useful for processing the vast amount of expected images efficiently and would help to identify processes affecting the ice sheet. 

We have trained a convolutional neural network to detect, classify and segment lineaments in images of Europa returned by the Galileo mission. The Galileo images that make up the training set are segmented manually, following a dedicated guideline. For better performance, we make use of synthetically generated data to pre-train the network. The current status of the work will be described.

How to cite: Haslebacher, C. and Thomas, N.: Autonomous lineament detection in Galileo images of Europa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-692, https://doi.org/10.5194/egusphere-egu22-692, 2022.

EGU22-1014 | Presentations | ITS2.1/PS1.2

Automatic detection of the electron density from the WHISPER instrument onboard CLUSTER II 

Emmanuel De Leon, Nicolas Gilet, Xavier Vallières, Luca Bucciantini, Pierre Henri, and Jean-Louis Rauch

The Waves of HIgh frequency and Sounder for Probing Electron density by Relaxation
(WHISPER) instrument, is part of the Wave Experiment Consortium (WEC) of the CLUSTER II
mission. The instrument consists of a receiver, a transmitter, and a wave spectrum
analyzer. It delivers active (when in sounding mode) and natural electric field spectra. The
characteristic signature of waves indicates the nature of the ambient plasma regime and, combined
with the spacecraft position, reveals the different magnetosphere boundaries and regions. The
thermal electron density can be deduced from the characteristics of natural waves in natural mode
and from the resonances triggered in sounding mode, giving access to a key parameter of scientific
interest and major driver for the calibration of particles instrument.
Until recently, the electron density derivation required a manual time/frequency domain
initialization of the search algorithms, based upon visual inspection of WHISPER active and natural
spectrograms and other datasets from different instruments onboard CLUSTER.
To automate this process, knowledge of the region (plasma regime) is highly desirable. A Multi-
Layer Perceptron model has been implemented for this purpose. For each detected region, a GRU,
recurrent network model combined with an ad-hoc algorithm is then used to determine the electron
density from WHISPER active spectra. These models have been trained using the electron density
previously derived from various semi-automatic algorithms and manually validated, resulting in an
accuracy up to 98% in some plasma regions. A production pipeline based on these models has been
implemented to routinely derive electron density, reducing human intervention up to 10 times. Work
is currently ongoing to create some models to process natural measurements where the data volume
is much higher and the validation process more complex. These models of electron density
automated determination will be useful for future other space missions.

How to cite: De Leon, E., Gilet, N., Vallières, X., Bucciantini, L., Henri, P., and Rauch, J.-L.: Automatic detection of the electron density from the WHISPER instrument onboard CLUSTER II, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1014, https://doi.org/10.5194/egusphere-egu22-1014, 2022.

EGU22-2765 | Presentations | ITS2.1/PS1.2

Extrapolation of CRISM based spectral feature maps using CaSSIS four-band images with machine learning techniques 

Michael Fernandes, Nicolas Thomas, Benedikt Elser, Angelo Pio Rossi, Alexander Pletl, and Gabriele Cremonese

Spectroscopy provides important information on the surface composition of Mars. Spectral data can support studies such as the evaluation of potential (manned) landing sites as well as supporting determination of past surface processes. The CRISM instrument on NASA’s Mars Reconnaissance Orbiter is a high spectral resolution visible infrared mapping spectrometer currently in orbit around Mars. It records 2D spatially resolved spectra over a wavelength range of 362 nm to 3920 nm. At present data collected covers less than 2% of the planet. Lifetime issues with the cryo-coolers prevents limits further data acquisition in the infrared band. In order to extend areal coverage for spectroscopic analysis in regions of major importance to the history of liquid water on Mars (e.g. Valles Marineris, Noachis Terra), we investigate whether data from other instruments can be fused to extrapolate spectral features in CRISMto these non-spectral imaged areas. The present work will use data from the CaSSIS instrument which is a high spatial resolution colour and stereo imager onboard the European Space Agency’s ExoMars Trace Gas Orbiter (TGO). CaSSIS returns images at 4.5 m/px from the nominal 400 km altitude orbit in four colours. Its filters were selected to provide mineral diagnostics in the visible wavelength range (400 – 1100 nm). It has so far imaged around 2% of the planet with an estimated overlap of ≲0.01% of CRISM data. This study introduces a two-step pixel based reconstruction approach using CaSSIS four band images. In the first step advanced unsupervised techniques are applied on CRISM hyperspectral datacubes to reduce dimensionality and establish clusters of spectral features. Given that these clusters contain reasonable information about the surface composition, in a second step, it is feasible to map CaSSIS four band images to the spectral clusters by training a machine learning classifier (for the cluster labels) using only CaSSIS datasets. In this way the system can extrapolate spectral features to areas unmapped by CRISM. To assess the performance of this proposed methodology we analyzed actual and artificially generated CaSSIS images and benchmarked results against traditional correlation based methods. Qualitative and quantitative analyses indicate that by this novel procedure spectral features of in non-spectral imaged areas can be predicted to an extent that can be evaluated quantitatively, especially in highly feature-rich landscapes.

How to cite: Fernandes, M., Thomas, N., Elser, B., Rossi, A. P., Pletl, A., and Cremonese, G.: Extrapolation of CRISM based spectral feature maps using CaSSIS four-band images with machine learning techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2765, https://doi.org/10.5194/egusphere-egu22-2765, 2022.

EGU22-2994 | Presentations | ITS2.1/PS1.2

Interpretable Solar Flare Prediction with Deep Learning 

Robert Jarolim, Astrid Veronig, Tatiana Podladchikova, Julia Thalmann, Dominik Narnhofer, Markus Hofinger, and Thomas Pock

Solar flares and coronal mass ejections (CMEs) are the main drivers for severe space weather disturbances on Earth and other planets. While the geo-effects of CMEs give us a lead time of about 1 to 4 days, the effects of flares and flare-accelerated solar energetic particles (SEPs) are very immediate, 8 minutes for the enhanced radiation and as short as about 20 minutes for the highest energy SEPs arriving at Earth. Thus, predictions of solar flare occurrence at least several hours ahead are of high importance for the mitigation of severe space weather effects.

Observations and simulations of solar flares suggest that the structure and evolution of the active region’s magnetic field is a key component for energetic eruptions. The recent advances in deep learning provide tools to directly learn complex relations from multi-dimensional data. Here, we present a novel deep learning method for short-term solar flare prediction. The algorithm is based on the HMI photospheric line-of-sight magnetic field and its temporal evolution together with the coronal evolution as observed by multi-wavelengths EUV filtergrams from the AIA instrument onboard the Solar Dynamics Observatory. We train a neural network to independently identify features in the imaging data based on the dynamic evolution of the coronal structure and the photospheric magnetic field evolution, which may hint at flare occurrence in the near future.

We show that our method  can reliably predict flares six hours ahead, with 73% correct flaring predictions (89% when considering only M- and X-class flares), and 83% correct quiet active region predictions.

In order to overcome the “black box problem” of machine-learning algorithms, and thus to allow for physical interpretation of the network findings, we employ a spatio-temporal attention mechanism. This allows us to extract the emphasized regions, which reveal the neural network interpretation of the flare onset conditions. Our comparison shows that predicted precursors are associated with the position of flare occurrence, respond to dynamic changes, and align with characteristics within the active region.

How to cite: Jarolim, R., Veronig, A., Podladchikova, T., Thalmann, J., Narnhofer, D., Hofinger, M., and Pock, T.: Interpretable Solar Flare Prediction with Deep Learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2994, https://doi.org/10.5194/egusphere-egu22-2994, 2022.

EGU22-5721 | Presentations | ITS2.1/PS1.2

Magnetopause and bow shock models with machine learning 

Ambre Ghisalberti, Nicolas Aunai, and Bayane Michotte de Welle

The magnetopause (MP) and the bow shock (BS) are the two boundaries bounding the magnetosheath, the region between the magnetosphere and the solar wind. Their position and shape depend on the upstream solar wind and interplanetary magnetic field conditions.

Predicting their shape and position is the starting point of many subsequent studies of processes controlling the coupling between the Earth’s magnetosphere and its interplanetary environment. We now have at our disposal an important amount of data from a multitude of spacecraft missions allowing for good spatial coverage, as well as algorithms based on statistical learning to automatically detect the two boundaries. From the data of 9 satellites over 20 years, we identified around 19000 crossings of the BS and 36000 crossings of the MP. They were used, together with their associated upstream conditions, to train a regression model to predict the shape and position of the boundaries. 

Preliminary results indicate that the obtained models outperform analytical models without making simplifying assumptions on the geometry and the dependency over control parameters.

How to cite: Ghisalberti, A., Aunai, N., and Michotte de Welle, B.: Magnetopause and bow shock models with machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5721, https://doi.org/10.5194/egusphere-egu22-5721, 2022.

EGU22-5739 | Presentations | ITS2.1/PS1.2

Deep learning for surrogate modeling of two-dimensional mantle convection 

Siddhant Agarwal, Nicola Tosi, Pan Kessel, Doris Breuer, and Grégoire Montavon

Mantle convection plays a fundamental role in the long-term thermal evolution of terrestrial planets like Earth, Mars, Mercury and Venus. The buoyancy-driven creeping flow of silicate rocks in the mantle is modeled as a highly viscous fluid over geological time scales and quantified using partial differential equations (PDEs) for conservation of mass, momentum and energy. Yet, key parameters and initial conditions to these PDEs are poorly constrained and often require a large sampling of the parameter space to find constraints from observational data. Since it is not computationally feasible to solve hundreds of thousands of forward models in 2D or 3D, some alternatives have been proposed. 

The traditional alternative to high-fidelity simulations has been to use 1D models based on scaling laws. While computationally efficient, these are limited in the amount of physics they can model (e.g., depth-dependent material properties) and predict only mean quantities such as the mean mantle temperature. Hence, there has been a growing interest in machine learning techniques to come up with more advanced surrogate models. For example, Agarwal et al. (2020) used feedforward neural networks (FNNs) to reliably predict the evolution of entire 1D laterally averaged temperature profile in time from five parameters: reference viscosity, enrichment factor for the crust in heat producing elements, initial mantle temperature, activation energy and activation volume of the diffusion creep. 

We extend that study to predict the full 2D temperature field, which contains more information in the form of convection structures such as hot plumes and cold downwellings. This is achieved by training deep learning algorithms on a data set of 10,525 2D simulations of the thermal evolution of the mantle of a Mars-like planet. First, we use convolutional autoencoders to compress the size of each temperature field by a factor of 142. Second,  we compare the use of two algorithms for predicting the compressed (latent) temperature fields: FNNs and long-short-term memory networks (LSTMs).  On the one hand, the FNN predictions are slightly more accurate with respect to unseen simulations (99.30%  vs. 99.22% for the LSTM). On the other hand, Proper orthogonal decomposition (POD) of the LSTM and FNN predictions shows that despite a lower mean relative accuracy, LSTMs capture the flow dynamics better than FNNs. The POD coefficients from FNN predictions sum up to 96.51% relative to the coefficients of the original simulations, while for LSTMs this metric increases to 97.66%. 

We conclude the talk by stating some strengths and weaknesses of this approach, as well as highlighting some ongoing research in the broader field of fluid dynamics that could help increase the accuracy and efficiency of such parameterized surrogate models.

How to cite: Agarwal, S., Tosi, N., Kessel, P., Breuer, D., and Montavon, G.: Deep learning for surrogate modeling of two-dimensional mantle convection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5739, https://doi.org/10.5194/egusphere-egu22-5739, 2022.

EGU22-6371 | Presentations | ITS2.1/PS1.2

STIX solar flare image reconstruction and classification using machine learning 

Hualin Xiao, Säm Krucker, Daniel Ryan, Andrea Battaglia, Erica Lastufka, Etesi László, Ewan Dickson, and Wen Wang

The Spectrometer Telescope for Imaging X-rays (STIX) is an instrument onboard Solar Orbiter. It measures X-rays emitted during solar flares in the energy range from 4 to 150 keV and takes X-ray images by using an indirect imaging technique, based on the Moiré effect. STIX instrument
consists of 32 pairs of tungsten grids and 32 pixelated CdTe detector units. Flare Images can be reconstructed on the ground using algorithms such as back-projection, forward-fit, and maximum-entropy after full pixel data are downloaded. Here we report a new image reconstruction and
classification model based on machine learning. Results will be discussed and compared with those from the traditional algorithms.

How to cite: Xiao, H., Krucker, S., Ryan, D., Battaglia, A., Lastufka, E., László, E., Dickson, E., and Wang, W.: STIX solar flare image reconstruction and classification using machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6371, https://doi.org/10.5194/egusphere-egu22-6371, 2022.

EGU22-8940 | Presentations | ITS2.1/PS1.2

Mars events polyphonic detection, segmentation and classification with a hybrid recurrent scattering neural network using InSight mission data 

Salma Barkaoui, Angel Bueno Rodriguez, Philippe Lognonné, Maarten De Hoop, Grégory Sainton, Mathieu Plasman, and Taichi kawamura

Since deployed on the Martian surface, the seismometer SEIS (Seismic Experiment for Interior Structure) and the APSS (Auxiliary Payload Sensors Suite) of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission have been recorded the daily Martian respectively ground acceleration and pressure. These data are essential to investigate the geophysical and atmospheric features of the red planet. So far, the InSight team were able to detect multiple Martian events. We distinguish two types: the artificial events like the lander modes or the micro-tilts known as glitches or the natural events like the pressure drops which are important to estimate the Martian subsurface and the seismic events used to study the interior structure of Mars. Despite the data complexity, the InSight team was able to catalog these events (Clinton et al 2020 for the seismic event catalog, Banfield et al., 2018, 2020 for the pressure drops catalog and Scholz et al. (2020) for the glitches catalog). However, despite all this effort, we are still in front of multiple challenges. In fact,  the seismic events' detection is limited  due to the SEIS sensitivity, which is the origin of a high noise level that may contaminate the seismic events. Thus, we can miss some of them, especially in the noisy period. Besides, their detection is very challenging and require multiple preprocessing task which is time-consuming. For the pressure drops, the detection method used in Banfield et al.  2020 is limited by a threshold equal to 0.3 Pa. Thus, the rest of pressure drops are not included. Plus, due to lack of energy, the pressure sensor was off for several days. As a result, many pressure drops were missed. As a result, being able to detect them directly on the SEIS data which are, in contrast,  provided continuously, is very important.

In this regard, the aim of this study is to overcome these challenges and thus improve the Martian events detection and provide an updated catalog automatically. For that, we were inspired of one of the main technics used today in data processing and analysis in a complete automatic way: it is the Machine Learning and particularly in our case is the Deep Learning. The architecture used for that is the “Hybrid Recurrent Scattering Neural Network” (Bueno et al 2021)  adapted for Mars

How to cite: Barkaoui, S., Bueno Rodriguez, A., Lognonné, P., De Hoop, M., Sainton, G., Plasman, M., and kawamura, T.: Mars events polyphonic detection, segmentation and classification with a hybrid recurrent scattering neural network using InSight mission data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8940, https://doi.org/10.5194/egusphere-egu22-8940, 2022.

EGU22-9077 | Presentations | ITS2.1/PS1.2

Automatic Detection of Interplanetary Coronal Mass Ejections 

Hannah Ruedisser, Andreas Windisch, Ute V. Amerstorfer, Tanja Amerstorfer, Christian Möstl, Martin A. Reiss, and Rachel L. Bailey

Interplanetary coronal mass ejections (ICMEs) are one of the main drivers for space weather disturbances. In the past,
different machine learning approaches have been used to automatically detect events in existing time series resulting from
solar wind in situ data. However, classification, early detection and ultimately forecasting still remain challenges when facing
the large amount of data from different instruments. We propose a pipeline using a Network similar to the ResUNet++ (Jha et al. (2019)), for the automatic detection of ICMEs. Comparing it to an existing method, we find that while achieving similar results, our model outperforms the baseline regarding GPU usage, training time and robustness to missing features, thus making it more usable for other datasets.
The method has been tested on in situ data from WIND. Additionally, it produced reasonable results on STEREO A and STEREO B datasets
with less input parameters. The relatively fast training allows straightforward tuning of hyperparameters and could therefore easily be used to detect other structures and phenomena in solar wind data, such as corotating interaction regions.

How to cite: Ruedisser, H., Windisch, A., Amerstorfer, U. V., Amerstorfer, T., Möstl, C., Reiss, M. A., and Bailey, R. L.: Automatic Detection of Interplanetary Coronal Mass Ejections, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9077, https://doi.org/10.5194/egusphere-egu22-9077, 2022.

EGU22-9621 | Presentations | ITS2.1/PS1.2

Machine Learning Techniques for Automated ULF Wave Recognition in Swarm Time Series 

Georgios Balasis, Alexandra Antonopoulou, Constantinos Papadimitriou, Adamantia Zoe Boutsi, Omiros Giannakis, and Ioannis A. Daglis

Machine learning (ML) techniques have been successfully introduced in the fields of Space Physics and Space Weather, yielding highly promising results in modeling and predicting many disparate aspects of the geospace. Magnetospheric ultra-low frequency (ULF) waves play a key role in the dynamics of the near-Earth electromagnetic environment and, therefore, their importance in Space Weather studies is indisputable. Magnetic field measurements from recent multi-satellite missions are currently advancing our knowledge on the physics of ULF waves. In particular, Swarm satellites have contributed to the expansion of data availability in the topside ionosphere, stimulating much recent progress in this area. Coupled with the new successful developments in artificial intelligence, we are now able to use more robust approaches for automated ULF wave identification and classification. Here, we present results employing various neural networks (NNs) methods (e.g. Fuzzy Artificial Neural Networks, Convolutional Neural Networks) in order to detect ULF waves in the time series of low-Earth orbit (LEO) satellites. The outputs of the methods are compared against other ML classifiers (e.g. k-Nearest Neighbors (kNN), Support Vector Machines (SVM)), showing a clear dominance of the NNs in successfully classifying wave events.

How to cite: Balasis, G., Antonopoulou, A., Papadimitriou, C., Boutsi, A. Z., Giannakis, O., and Daglis, I. A.: Machine Learning Techniques for Automated ULF Wave Recognition in Swarm Time Series, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9621, https://doi.org/10.5194/egusphere-egu22-9621, 2022.

The solar wind and its variability is well understood at Earth. However, at distances larger than 1AU the is less clear, mostly due to the lack of in-situ measurements. In this study we use transfer learning principles to infer solar wind conditions at Mars in periods where no measurements are available, with the aim of better illuminating the interaction between the partially magnetised Martian plasma environment and the upstream solar wind. Initially, a convolutional neural network (CNN) model for forecasting measurements of the interplanetary magnetic field, solar wind velocity, density and dynamic pressure is trained on terrestrial solar wind data. Afterwards, knowledge from this model is incorporated into a secondary CNN model which is used for predicting solar wind conditions upstream of Mars up to 5 hours in the future. We present the results of this study as well as the opportunities to expand this method for use at other planets.

How to cite: Durward, S.: Forecasting solar wind conditions at Mars using transfer learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10105, https://doi.org/10.5194/egusphere-egu22-10105, 2022.

EGU22-11501 | Presentations | ITS2.1/PS1.2

Automatic detection of solar magnetic tornadoes based on computer vision methods. 

Dmitrii Vorobev, Mark Blumenau, Mikhail Fridman, Olga Khabarova, and Vladimir Obridko

We propose a new method for automatic detection of solar magnetic tornadoes based on computer vision methods. Magnetic tornadoes are magneto-plasma structures with a swirling magnetic field in the solar corona, and there is also evidence for the rotation of plasma in them. A theoretical description and numerical modeling of these objects are very difficult due to the three-dimensionality of the structures and peculiarities of their spatial and temporal dynamics [Wedemeyer-Böhm et al, 2012, Nature]. Typical sizes of magnetic tornadoes vary from 102 km up to 106 km, and their lifetime is from several minutes to many hours. So far, quite a few works are devoted to their study, and there are no accepted algorithms for detecting solar magnetic tornadoes by machine methods. An insufficient number of identified structures is one of many problems that do not allow studying physics of magnetic tornadoes and the processes associated with them. In particular, the filamentous rotating structures are well delectable only at the limb, while one can only make suppositions about their presence at the solar disk.
Our method is based on analyzing SDO/AIA images at wavelengths 171 Å, 193 Å, 211 Å and 304 Å, to which several different algorithms are applied, namely, the convolution with filters, convolutional neural network, and gradient boosting. The new technique is a combination of several approaches (transfer learning & stacking) that are widely used in various fields of data analysis. Such an approach allows detecting the structures in a short time with sufficient accuracy. As test objects, we used magnetic tornadoes previously described in the literature [e.g., Wedemeyer et al 2013, ApJ; Mghebrishvili et al. 2015 ApJ]. Our method made it possible to detect those structures, as well as to reveal previously unknown magnetic tornadoes.

How to cite: Vorobev, D., Blumenau, M., Fridman, M., Khabarova, O., and Obridko, V.: Automatic detection of solar magnetic tornadoes based on computer vision methods., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11501, https://doi.org/10.5194/egusphere-egu22-11501, 2022.

EGU22-12480 | Presentations | ITS2.1/PS1.2

A versatile exploration method for simulated data based on Self Organizing Maps 

Maria Elena Innocenti, Sophia Köhne, Simon Hornisch, Rainer Grauer, Jorge Amaya, Jimmy Raeder, Banafsheh Ferdousi, James "Andy" Edmond, and Giovanni Lapenta

The large amount of data produced by measurements and simulations of space plasmas has made it fertile ground for the application of classification methods, that can support the scientist in preliminary data analysis. Among the different classification methods available, Self Organizing Maps, SOMs [Kohonen, 1982] offer the distinct advantage of producing an ordered, lower-dimensional representation of the input data that preserves their topographical relations. The 2D map obtained after training can then be explored to gather knowledge on the data it represents. The distance between nodes reflects the distance between the input data: one can then further cluster the map nodes to identify large scale regions in the data where plasma properties are expected to be similar.

In this work, we train SOMs using data from different simulations of different aspects of the heliospheric environment: a global magnetospheric simulation done with the OpenGGCM-CTIM-RCM code, a Particle In Cell simulation of plasmoid instability done with the semi-implicit code ECSIM, a fully kinetic simulation of single X point reconnection done with the Vlasov code implemented in MuPhy2.

We examine the SOM feature maps, unified distance matrix and SOM node weights to unlock information on the input data. We then classify the nodes of the different SOMs into a lower and automatically selected number of clusters, and we obtain, in all three cases, clusters that map well to our a priori knowledge on the three systems. Results for the magnetospheric simulations are described in Innocenti et al, 2021. 

This classification strategy then emerges as a useful, relatively cheap and versatile technique for the analysis of simulation, and possibly observational, plasma physics data.

Innocenti, M. E., Amaya, J., Raeder, J., Dupuis, R., Ferdousi, B., & Lapenta, G. (2021). Unsupervised classification of simulated magnetospheric regions. Annales Geophysicae Discussions, 1-28. 

https://angeo.copernicus.org/articles/39/861/2021/angeo-39-861-2021.pdf

How to cite: Innocenti, M. E., Köhne, S., Hornisch, S., Grauer, R., Amaya, J., Raeder, J., Ferdousi, B., Edmond, J. "., and Lapenta, G.: A versatile exploration method for simulated data based on Self Organizing Maps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12480, https://doi.org/10.5194/egusphere-egu22-12480, 2022.

EGU22-12830 | Presentations | ITS2.1/PS1.2

Re-implementing and Extending the NURD Algorithm to the Full Duration of the Van Allen Probes Mission 

Matyas Szabo-Roberts, Karolina Kume, Artem Smirnov, Irina Zhelavskaya, and Yuri Shprits

Generating reliable databases of electron density measurements over a wide range of geomagnetic conditions is essential for improving empirical models of electron density. The Neural-network-based Upper hybrid Resonance Determination (NURD) algorithm has been developed for automated extraction of electron density from Van Allen Probes electric field measurements, and has been shown to be in good agreement with existing semi-automated methods and empirical models. The extracted electron density data has since then been used to develop the PINE (Plasma density in the Inner magnetosphere Neural network-based Empirical) model, an empirical model for reconstructing the global dynamics of the cold plasma density distribution based only on solar wind data and geomagnetic indices.
In this study we re-implement the NURD algorithm in both Python and Matlab, and compare the performance of these implementations to each other and previous NURD results. We take advantage of a labeled training data set now being available for the full duration of the Van Allen Probes mission to train the network and generate an electron density data set for a significantly longer time period. We perform detailed comparisons between this output, electron density produced from Van Allen Probes electric field measurements using the AURA semi-automated algorithm, and electron density obtained from existing empirical models. We also present preliminary results from the PINE plasmasphere model trained on this extended NURD electron density data set.

How to cite: Szabo-Roberts, M., Kume, K., Smirnov, A., Zhelavskaya, I., and Shprits, Y.: Re-implementing and Extending the NURD Algorithm to the Full Duration of the Van Allen Probes Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12830, https://doi.org/10.5194/egusphere-egu22-12830, 2022.

EGU22-565 | Presentations | ST1.5

Linking In-situ Magnetic and Density Structures in the Low Latitude Slow Solar Wind to Solar Origins 

Thomas Woolley, Lorenzo Matteini, Timothy S. Horbury, Stuart D. Bale, Ronan Laker, Lloyd D. Woodham, and Julia E. Stawarz

To date, Parker Solar Probe has completed ten solar encounters and measured a wealth of in-situ data down to heliocentric distances of ~13 solar radii. This data provides a novel opportunity to investigate the near-Sun environment and understand the young slow solar wind. Typically, the slow solar wind observed in the inner heliosphere is split into an Alfvenic and a non-Alfvenic component. The Alfvenic slow wind is thought to originate from overexpanded coronal hole field lines, whereas the non-Alfvenic slow wind could originate from active regions, transient events, or reconnection at the tips of helmet streamers. In this work, we find structures associated with non-Alfvenic slow wind in the low latitude wind measured by Parker Solar Probe. We identify at least two distinct types of structure using magnetic field magnitude, electron pitch angle distributions, and electron number density. After statistically analysing these structures, with a focus on their plasma properties, shape, and location with respect to the heliospheric current sheet, we link them to solar origins. We find structures that are consistent with the plasma blobs seen previously in remote sensing observations.

How to cite: Woolley, T., Matteini, L., Horbury, T. S., Bale, S. D., Laker, R., Woodham, L. D., and Stawarz, J. E.: Linking In-situ Magnetic and Density Structures in the Low Latitude Slow Solar Wind to Solar Origins, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-565, https://doi.org/10.5194/egusphere-egu22-565, 2022.

EGU22-1353 | Presentations | ST1.5

Suprathermal Ion Observations Associated with the Heliospheric Current Sheet Crossings during Parker Solar Probe Encounters 7, 8, and 9 

Mihir Desai and the the Parker Solar Probe ISOIS, FIELDS & SWEAP Teams

We report observations of <100 keV/nucleon suprathermal (ST) H, He, O, and Fe ions in association with three separate crossings of the heliospheric current sheet that occurred near perhelia during PSP encounters 7, 8, and 9. In particular, we compare and contrast the ST ion time-intensity profiles, velocity dispersion, pitch-angle distributions, spectral forms, and maximum energies during the three HCS crossings. We find that these unique ST observations are remarkably different in each case, with those during E07 posing the most serious challenges for existing models of ST ion production in the inner heliosphere. In contrast, the ISOIS observations during E08 appear to be consistent with a scenario in which ST ions escape out of the reconnection exhausts into the separatrix layers after getting accelerated up to ~50-100 keV/nucleon by HCS-associated magnetic reconnection-driven processes. Finally, ST ions during the E09 HCS crossing have properties that are somewhat similar to those seen during both E07 and E08 crossings, with ion intensities being higher outside the exhausts and the separatrices, but significant intensity increases are also observed inside the reconnection exhausts. We discuss these new observations in terms of local versus remote acceleration sources as well as in terms of expectations of existing ST ion production and propagation, including reconnection-driven and diffusive acceleration in the inner heliosphere.

How to cite: Desai, M. and the the Parker Solar Probe ISOIS, FIELDS & SWEAP Teams: Suprathermal Ion Observations Associated with the Heliospheric Current Sheet Crossings during Parker Solar Probe Encounters 7, 8, and 9, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1353, https://doi.org/10.5194/egusphere-egu22-1353, 2022.

EGU22-1357 | Presentations | ST1.5

Evolution of power spectral density of magnetic field fluctuations in the inner heliosphere 

Jana Safrankova, Zdenek Nemecek, Frantisek Nemec, Tereza Durovcova, Luca Franci, and Alexander Pitna

The solar wind is a unique laboratory to study the turbulent processes occurring in a collisionless plasma with high Reynolds numbers. The paper analyzes power spectra of magnetic field fluctuations that are computed in the frequency range around the break between inertial and kinetic scales. We use observations made during first nine Parker Solar Probe encounters and compare them with observations of the spacecraft moving in other distances from the Sun (e.g., Solar Orbiter) and closer to 1 AU (Wind). A preliminary analysis of magnetic field fluctuations based on PSP and Wind measurements from the MHD to kinetic scales has shown that a relative level of compressive fluctuations increases until 0.25 AU and remains constant till 1 AU whereas a relative level of perpendicular fluctuations does not change with the distance from the Sun. We can conclude that the B slope is controlled by different process(es) close to the Sun against 1 AU and that, in spite of expectations, the critical distance for turbulence evolution is as large as 0.25 AU. We also discuss the role of important physical parameters (e.g., ion beta, temperature anisotropy, collisional age, magnetic field fluctuation amplitude) determining the properties of the turbulent cascade in different heliospheric locations.

How to cite: Safrankova, J., Nemecek, Z., Nemec, F., Durovcova, T., Franci, L., and Pitna, A.: Evolution of power spectral density of magnetic field fluctuations in the inner heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1357, https://doi.org/10.5194/egusphere-egu22-1357, 2022.

EGU22-1809 | Presentations | ST1.5

Correlated Magnetic Field Dropouts and Plasma Wave Activity at Switchback Boundaries as Observed by Parker Solar Probe 

Anthony Rasca, William Farrell, Robert MacDowall, Stuart Bale, and Justin Kasper

The first solar encounters by the Parker Solar Probe revealed the magnetic field to be dominated by short field reversals in the radial direction referred to as "switchbacks."  While radial velocity and proton temperature were shown to increase inside the switchbacks, B exhibits very brief dropouts only at the switchback boundaries.  Brief intensifications in spectral density measurements near the electron plasma frequency, fpe, have also been observed at these boundaries, indicating the presence of plasma waves triggered by electron beams.  We perform a correlative study using observations from the Parker FIELDS Radio Frequency Spectrometer (RFS) and Fluxgate Magnetometer (MAG) to compare occurrences of spectral density intensifications at the electron plasma frequency (fpe intensifications) and B dropouts at switchback boundaries during Parker's first and second solar encounters.  We find that only a small fraction of minor B dropouts are associated with fpe intensifications.  This fraction increases with B dropout size until all dropouts are associated with fpe intensifications.  This suggests that in the presence of strong B dropouts, electron currents that create the perturbation in B along the boundaries are also stimulating plasma waves such as Langmuir waves.

How to cite: Rasca, A., Farrell, W., MacDowall, R., Bale, S., and Kasper, J.: Correlated Magnetic Field Dropouts and Plasma Wave Activity at Switchback Boundaries as Observed by Parker Solar Probe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1809, https://doi.org/10.5194/egusphere-egu22-1809, 2022.

EGU22-2273 | Presentations | ST1.5

Sheath characteristics of interplanetary coronal mass ejections derived from Helios and PSP data 

Manuela Temmer and Volker Bothmer

Helios 1 and 2 data, covering the distance range from 0.3-1au, have been analysed to derive the characteristics of various substructures of interplanetary coronal mass ejections (ICMEs). We have investigated a data sample of 40 events observed by the Helios 1/2 spacecraft during the time period 1974-1981 with respect to the characteristics of different ICME features, such as sheath regions, leading edges and the magnetic ejecta (ME) themselves. For comparison and to investigate events at distances even closer to the Sun, we add a sample of 5 ICMEs observed with Parker Solar Probe during 2018-2021. We study the sheath density variations over distance and relate those to the ambient solar wind speed. The results show that the sheath region is moderately anti-correlated with the solar wind speed ahead of the disturbance. We further find that the sheath density becomes dominant over the ME density beyond about 0.2au and that its spatial extent constantly increases with distance. The results are important for better understanding the CME mass evolution due to sheath enlargements. Based on these analyses we derive an empirical relation between the sheath density and the local solar wind plasma speed upstream of the ICME shock. The empirical results can be used to model the sheath structure and help improve our understanding about CME propagation in the inner heliosphere.

How to cite: Temmer, M. and Bothmer, V.: Sheath characteristics of interplanetary coronal mass ejections derived from Helios and PSP data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2273, https://doi.org/10.5194/egusphere-egu22-2273, 2022.

EGU22-2638 | Presentations | ST1.5

Alfvénicity of velocity and magnetic field Increments Observed by Parker Solar Probe 

Panisara Thepthong, Peera Pongkitiwanichakul, and David Ruffolo

Alfvénicity is a well-known property of the solar wind. The magnetic and velocity fluctuations are highly correlated over much of the region between the Sun and the Earth. The Parker Solar Probe (PSP) spacecraft enables us to probe Alfvénicity closer to the Sun than before. One previous finding is that the Alfvén ratio increases as the scales become smaller, as shown in some works by using Fourier analysis. This work measures Alfvénicity from PSP observations using 2nd-order structure functions and other quantities derived from magnetic and velocity increments as functions of time lag. We introduce a method to subtract noise from the velocity structure function. We also provide the relation between a time lag in our work and the frequency that contributes most to the 2nd-order structure function for such a time lag. This relation allows a direct comparison between functions of time lag and Fourier spectra. This research has been supported in part by grant RGNS 63-045 from Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation, and by grant RTA6280002 from Thailand Science Research and Innovation.

How to cite: Thepthong, P., Pongkitiwanichakul, P., and Ruffolo, D.: Alfvénicity of velocity and magnetic field Increments Observed by Parker Solar Probe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2638, https://doi.org/10.5194/egusphere-egu22-2638, 2022.

The high Reynolds number solar wind flow provides a natural laboratory for the study of turbulence in-situ. Parker Solar Probe has to date executed nine sampling distances between 0.2 AU to 1 AU, providing an opportunity to study how turbulence evolves in the expanding solar wind. We focus on data from the PSP/FIELDS[1] and the PSP/SWEAP[2] experiments which provide magnetic field and plasma observations respectively at sub-second cadence. We have identified multiple intervals of uniform solar wind turbulence, selected to exclude coherent structures such as pressure pulses and current sheets, and in which the primary proton population velocity varies by less than 20% of its mean value. We focus on events of multiple-hour duration, which span the spectral scales from the approximately 1/f range at low frequencies, through the magnetohydrodynamic (MHD) inertial range of turbulence and into the kinetic range, below the ion gyrofrequency. We perform a Haar wavelet decomposition[3] which provides accurate estimations of the exponents of these power-law ranges of the spectra, and of higher-order moments. This allows us to study how the spectral exponents may vary with distance from the sun and with solar wind conditions such as the plasma beta. We perform this analysis for both the magnetic field components and magnitude, which track Alfvenic and compressive turbulent fluctuations, respectively. At 1 AU, compressive fluctuations are known to exhibit scaling properties distinct from that of the individual magnetic field components.[4] Here we will investigate this behaviour at different distances from the Sun, plasma beta, and proton density.

We acknowledge the NASA Parker Solar Probe Mission and the SWEAP team led by J. Kasper and the FIELDS team led by S. D. Bale for use of data.

[1] Bale, S.D., Goetz, K., Harvey, P.R. et al. The FIELDS Instrument Suite for Solar Probe Plus.Space Sci Rev 204, 49–82 (2016). https://doi.org/10.1007/s11214-016-0244-5

[2] Kasper, J.C., Abiad, R., Austin, G. et al. Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus. Space Sci Rev 204, 131–186 (2016). https://doi.org/10.1007/s11214-015-0206-3

[3] Kiyani, K.H., Chapman, S.C., Sahraoui, F., Hnat, B., Fauvarque, O., Khotyaintsev, Y.V.: Enhanced Magnetic Compressibility and Isotropic Scale Invariance at Sub-ion Larmor Scales in Solar Wind Turbulence. The Astrophysical Journal 763(1), 10 (2012). https://doi.org/10.1088/0004-637x/763/1/10

[4] Hnat, B., Chapman, S., Gogoberidze, G., Wicks, R.: Scale-free texture of the fast solar wind. Physical review. E, Statistical, nonlinear, and soft matter physics 84, 065401 (2011). https://doi.org/10.1103/PhysRevE.84.065401
 
 
 
 
 
 

How to cite: Wang, X., Chapman, S., Dendy, R., and Hnat, B.: Wavelet analysis of scaling in plasma fluctuations in the magnetohydrodynamic range of solar wind turbulence seen by Parker Solar Probe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2945, https://doi.org/10.5194/egusphere-egu22-2945, 2022.

EGU22-3195 | Presentations | ST1.5

The emission of near-fce harmonic waves at small radial distances from the Sun 

Sabrina F. Tigik, Andris Vaivads, and David M. Malaspina

Near-fce harmonic waves are prevalent in the high-frequency electric field spectrum during Parker Solar Probe's (PSP) close encounters with the Sun. These waves are electrostatic and tend to occur in regions of a relatively stable magnetic field with low broadband magnetic fluctuation levels. We show that the emissions of near-fce harmonic waves are strongly connected to the magnetic field direction. We express the magnetic field direction in terms of spherical angles, where θB is the elevation angle and φB is the azimuthal angle. Then, we show that near-fce harmonics emissions occur when the magnetic field points in a narrow angular range, bounded by 80° ≤ θB ≤ 100° and 10° ≤ φB ≤ 30°, in most of the cases. We also show that the influence of magnetic field direction on near-fce harmonic waves goes down to the shortest time scales the FIELDS instrument can access. These results suggest that cross-scale interaction might play an essential role in the dynamics of the near-fce harmonics measured by PSP at small radial distances from the Sun. It may also provide important clues about the origin of these waves and their role at the early stages of solar wind evolution.

How to cite: F. Tigik, S., Vaivads, A., and M. Malaspina, D.: The emission of near-fce harmonic waves at small radial distances from the Sun, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3195, https://doi.org/10.5194/egusphere-egu22-3195, 2022.

EGU22-3859 | Presentations | ST1.5

Polarization of Langmuir waves observed by RPW-TDS instrument on Solar Orbiter during Type III radio bursts 

Jan Soucek, Sampath Bandara, David Pisa, Ondrej Santolik, Milan Maksimovic, Thomas Chust, Yuri Khotyaintsev, Antonio Vecchio, Matthieu Kretzschmar, Robert Wimmer-Schweingruber, Lars Berger, Javier Rodriquez-Pacheco, and Raul Gomez-Herrero

We investigate the polarization of Langmuir waves observed by the Time Domain Sampler (TDS) module of the Radio and Plasma Waves instrument on Solar Orbiter during several extensive Type III burst events. During its two-year-long cruise phase, Solar orbiter often crossed the source region of the Type III radio emission and observed the Langmuir waves generated by solar energetic electrons. The waves are known to exhibit complex modulation and often non-trivial elliptical polarization which sometimes rapidly changes on the timescales of tens of milliseconds. We show that the observed waveforms are typically composed of multiple sub-packets with a relatively short coherence length. We investigate the correlation between the polarization of the waves, simultaneously observed energetic electrons beams and other plasma properties.

How to cite: Soucek, J., Bandara, S., Pisa, D., Santolik, O., Maksimovic, M., Chust, T., Khotyaintsev, Y., Vecchio, A., Kretzschmar, M., Wimmer-Schweingruber, R., Berger, L., Rodriquez-Pacheco, J., and Gomez-Herrero, R.: Polarization of Langmuir waves observed by RPW-TDS instrument on Solar Orbiter during Type III radio bursts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3859, https://doi.org/10.5194/egusphere-egu22-3859, 2022.

EGU22-3917 | Presentations | ST1.5

On the Deflections of Switchbacks 

Ronan Laker, Tim Horbury, Lorenzo Matteini, Thomas Woolley, Julia Stawarz, and Stuart Bale

Following their presence during Parker Solar Probe’s (PSP) first encounter, switchbacks have become an active area of research with several proposed mechanisms for their formation. Many of these theories have testable predictions, although it is not trivial to compare simulation results with in-situ data from PSP. For example, there is some debate regarding the deflection direction of switchbacks, with some theories predicting a consistent magnetic deflection in the +T direction in the RTN coordinate system. Such arguments are largely focussed on the first two PSP encounters, as these are the most studied encounters in the literature. We examine the deflection direction of switchbacks for the first eight PSP encounters, with the aim to clear up any ambiguity regarding this property of switchbacks. Much like the earlier results of Horbury et al. 2020 (during the first encounter) we find that switchbacks tend to deflect in the same direction for hours at a time. Although there is some consistency in deflection direction within an individual encounter, crucially we find that there is no preferred deflection direction across all the encounters. We speculate about the cause of these results and what implications they may have for switchback formation theories.

How to cite: Laker, R., Horbury, T., Matteini, L., Woolley, T., Stawarz, J., and Bale, S.: On the Deflections of Switchbacks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3917, https://doi.org/10.5194/egusphere-egu22-3917, 2022.

EGU22-4130 | Presentations | ST1.5

Observations of the Time Domain Sampler receiver from the Radio and Plasma Wave instrument during the Solar Orbiter Earth flyby 

David Pisa, Jan Soucek, Ondrej Santolik, Miroslav Hanzelka, Milan Maksimovic, Antonio Vecchio, Yuri Khotyaintsev, Thomas Chust, Matthieu Kretzschmar, Lorenzo Matteini, and Timothy Horbury

On November 27, 2021, Solar Orbiter completed its only flyby of Earth on its way to the following Sun’s encounter in March 2022. Although this fast flyby was performed primarily to decrease the spacecraft’s velocity and change orbit to get closer to the Sun, the Radio and Plasma Wave (RPW) instrument had the opportunity to perform high cadence measurements in the Earth’s magnetosphere. We review the main observation of the Time Domain Sampler (TDS) receiver, a part of the RPW instrument, made during this flyby at frequencies below 200 kHz. The TDS receiver operated in a high cadence mode providing us with the regular waveform snapshot with 62 ms length every ten seconds for two electric components. Besides the regular captures, we have got more than five hundred onboard classified snapshots and the statistical products with a sixteen-second cadence. Before entering the terrestrial magnetosphere around 02:30UT, the spacecraft wandered through the foreshock region, registering intense bursts of Langmuir waves. After the bowshock crossing, Solar Orbiter was for more than two hours in the morning sector of the magnetosphere, recording various plasma wave modes. The closest approach was reached at 04:30UT above North Africa at an altitude of 460 km. Then the spacecraft continued into the Earth’s tail and entered the magnetosheath around 13:00UT. After 15:00UT, the Solar Orbiter crossed the bowshock, and bursts of Langmuir waves were detected again pointing out to the deep downstream foreshock region. Further from the Earth, intense Auroral Kilometric Radiation (AKR) at frequencies above 100 kHz was also detected.

How to cite: Pisa, D., Soucek, J., Santolik, O., Hanzelka, M., Maksimovic, M., Vecchio, A., Khotyaintsev, Y., Chust, T., Kretzschmar, M., Matteini, L., and Horbury, T.: Observations of the Time Domain Sampler receiver from the Radio and Plasma Wave instrument during the Solar Orbiter Earth flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4130, https://doi.org/10.5194/egusphere-egu22-4130, 2022.

EGU22-8923 | Presentations | ST1.5

Origin of the solar wind observed by PSP 

Jasmina Magdalenic, Senthamizh Pavai Valliappan, and Luciano Rodriguez

The recently available novel Parker Solar Probe (PSP) observations allow mapping of the solar wind characteristics in the low solar corona, at only a few tens of solar radii, and study the characteristics of the solar wind and its transients close to the Sun. The first few perihelion passes of the PSP revealed the highly variable structure of the solar wind. These observations provided the unique possibility to study the solar wind originating from small coronal holes. Such studies were previously not possible as the majority of the in situ observations were taken at distances of about 1 AU, and the association of the solar wind originating from the small coronal holes and its sources on the Sun was extremely unreliable. We employ a magnetic connectivity tool (developed by ESA’s MADAWG group) to associate the solar wind parcels observed by the PSP with their source regions on the Sun.  Our study encompasses the first eight PSP perihelion passes, using a time window of about three weeks around each perihelion. The first results indicate that we can well distinguish and identify the solar wind observed by the PSP originating not only from the big, but also from the small coronal holes.

How to cite: Magdalenic, J., Valliappan, S. P., and Rodriguez, L.: Origin of the solar wind observed by PSP, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8923, https://doi.org/10.5194/egusphere-egu22-8923, 2022.

EGU22-8932 | Presentations | ST1.5

Solar wind modelling with EUHFORIA and comparison with the PSP observations 

Senthamizh Pavai Valliappan, Jasmina Magdalenic, Luciano Rodriguez, Stefaan Poedts, and Evangelia Samara

During recent decades, numerous studies were devoted to improve our understanding of the origin and the propagation of the fast solar wind, and its accurate modelling. The solar wind characteristics were poorly mapped up to now by the in situ observations, available mostly only at about 1AU. The novel Parker Solar Probe (PSP) observations, that are employed in this study, allow us to map the solar wind characteristics in the low solar corona at only few tens of solar radii, and to study the solar wind characteristics. These observations are also very important for understanding how accurately we can model the solar wind characteristics employing models such as EUHFORIA (European heliospheric forecasting information asset, Pomoell & Poedts, 2018), at distances rather close to the Sun.
In this study, we inspect the solar wind characteristics during the first eight closest PSP approaches to the Sun. The solar wind plasma characteristics observed by PSP are compared with the modelling results using the default set-up of EUHFORIA. We also calibrate the inner boundary (0.1 AU) conditions in EUHFORIA, but without changing the Wang-Sheeley-Arge formula which describes the solar wind characteristics at the inner boundary. The aim is to better model the solar wind at distances close to the Sun. We also use a magnetic connectivity tool (developed by ESA’s MADAWG group) to better associate the fast solar wind with its source region on the Sun.

How to cite: Valliappan, S. P., Magdalenic, J., Rodriguez, L., Poedts, S., and Samara, E.: Solar wind modelling with EUHFORIA and comparison with the PSP observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8932, https://doi.org/10.5194/egusphere-egu22-8932, 2022.

EGU22-9673 | Presentations | ST1.5

From Magnetic Reconnection at Chromospheric Network Boundaries to Switchbacks in the Inner Heliosphere 

Chuanpeng Hou, Jiansen He, Die Duan, Huichao Li, and Yajie Chen

During its perihelion encounter, Parker Solar Probe (PSP) has observed abundant kink and switchback patterns of magnetic field lines in the young solar wind. Such switchback structures have gained widespread attention due to their manifestation of Alfvenic and compressional properties, such as velocity enhancement, plasma density, and temperature variation. In particular, the origin mechanism has been a hot topic and waits to be observationally confirmed. Here we use a two-step ballistic backmapping method (tracing along the Parker Spiral and the PFSS-solution extrapolated from the GONG synoptic magnetogram) to determine the foot-points of the magnetic lines during switchback events measured by PSP on 24th-27th Jan. 2020. We identify ten jets corresponding to the PSP-switchbacks and find relevance between jets and switchback patches. We find that jets excite at the height of around low corona and position of chromospheric network boundaries. About 70% of jets accompany a magnetic cancelation, while 30% of jets are related to magnetic emergence. The variation in magnetic flux corresponding to magnetic cancelation and magnetic emergence is quantitatively equal to that of radial magnetic flux associated with switchback patches. These features suggest that switchbacks may originate from an interchange magnetic reconnection at chromospheric network boundaries, which provides direct evidence of switchbacks' solar origin. 

How to cite: Hou, C., He, J., Duan, D., Li, H., and Chen, Y.: From Magnetic Reconnection at Chromospheric Network Boundaries to Switchbacks in the Inner Heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9673, https://doi.org/10.5194/egusphere-egu22-9673, 2022.

EGU22-12654 | Presentations | ST1.5

Non-thermal features in proton and alpha velocity distribution functions in the solar wind in the inner heliosphere 

Raffaella DAmicis, Roberto Bruno, Rossana De Marco, Marco Velli, Daniele Telloni, Denise Perrone, Luca Sorriso-Valvo, and Olga Panasenco

The solar wind is a highly variable, weakly collisional plasma originating from the Sun. The recent launches of PSP and Solar Orbiter have opened the way for the exploration of the innermost regions of our solar system and will greatly advance our understanding of several plasma phenomena occurring in the near-Sun environment, such as the heating and the acceleration of the solar wind. 

Plasma waves and wave-particle interactions play a relevant role in such phenomena, determining significant deviations of the Velocity Distribution Function (VDF) from the Local Thermodynamic Equilibrium. These deviations retain information of the interaction of particles with the turbulent electromagnetic fields and can be identified as thermal anisotropy, or non-thermal ion beams and heavy ion differential streaming in the ion component of the solar wind. This study will cover these topics with particular reference to new in-situ data from Solar Orbiter, PSP and with observations at L1  (e.g. Wind), with a focus on the central role Alfvénic fluctuations play in the evolution of the VDF features mentioned above.

How to cite: DAmicis, R., Bruno, R., De Marco, R., Velli, M., Telloni, D., Perrone, D., Sorriso-Valvo, L., and Panasenco, O.: Non-thermal features in proton and alpha velocity distribution functions in the solar wind in the inner heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12654, https://doi.org/10.5194/egusphere-egu22-12654, 2022.

EGU22-1221 | Presentations | ST1.6

Diurnal anisotropy of polar neutron monitors, Dome C looks poleward 

Agnieszka Gil, Alexander Mishev, Stepan Poluianov, and Ilya Usoskin

Galactic cosmic rays (GCR) show a small local anisotropy detected as a diurnal variability of neutron monitor (NM) count rates. As the asymptotic directions of different NMs are diverse, the capability of the GCR diurnal variation observation is also various. Here we present that the Dome C (DOMC) NM is barely sensitive to the diurnal variation. Its amplitude is very small, 0.03%, in comparison to other polar NMs, for which the diurnal variability amplitudes vary from 0.16 to 0.4%. This fact is associated to the narrow asymptotic-direction cone of DOMC NM looking almost to the South pole with geographic latitude above 75o. Thus, DOMC NM is the only existing NM accepting cosmic-ray particles from the off-equatorial region, which makes this station a unique detector.

How to cite: Gil, A., Mishev, A., Poluianov, S., and Usoskin, I.: Diurnal anisotropy of polar neutron monitors, Dome C looks poleward, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1221, https://doi.org/10.5194/egusphere-egu22-1221, 2022.

The first solar proton event of solar cycle 25 was detected on 28 October 2021 by several neutron monitors (NMs) in the polar regions, the strongest signal was registered by the DOMC/DOMB monitors located at the Antarctic plateau at Concordia French-Italian research station. It is identified as the GLE (ground-level enhancement) #73 in the International GLE database. Here, we report the observations of the GLE by the global NM network and present the derived angular and spectral features of solar energetic protons with their dynamical evolution throughout the event employing a state-of-the-art model based on analysis of the neutron monitor data. Using the derived spectra we computed the related terrestrial effects, namely the cosmic rate induced ionization at several altitudes on a global map and discuss possible implications.

How to cite: Mishev, A., Larsen, N., and Usoskin, I.: The first GLE (# 73 – 28-Oct-2021) of solar cycle 25: a study of the related terrestrial effects using neutron monitor data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1243, https://doi.org/10.5194/egusphere-egu22-1243, 2022.

EGU22-4215 | Presentations | ST1.6

Cosmic Ray Flux Correlation between McMurdo and Jang Bogo Neutron Monitor Stations vs. Time Lag 

Ekawit Kittiya, Waraporn Nuntiyakul, Achara Seripienlert, Paul Evenson, Alejandro Saiz, David Ruffolo, and Sueyon Oh

A neutron monitor is a large ground-based detector responding to the flux of cosmic ray particles in space by measuring atmospheric secondary neutrons. Any ground-based detector is sensitive to cosmic rays from a specific range of directions in space. In particular, a particle arriving from a specific sky direction with a specific rigidity (momentum per unit charge) was necessarily moving from a certain direction in space, called the asymptotic direction. McMurdo and Jang Bogo neutron monitor stations are Antarctic stations with similar geomagnetic latitudes but slightly different longitudes. From December 17, 2015 to January 9, 2017, six of the eighteen neutron counters from McMurdo had been transferred to Jang Bogo (with full transfer to Jang Bogo completed in December 2017). We present an analysis of the correlation of the cosmic ray flux between the McMurdo and Jang Bogo stations, during the time when both were operating, with ten-second time resolution. Although highly correlated, there are significant differences, including a systematic time lag of approximately 16 minutes between the data from the two stations. Although McMurdo observes with similar asymptotic directions to Jang Bogo, the response-weighted average directions still have a substantial difference of 21.9 degrees in geographic longitude, so with Earth’s rotation, time-independent anisotropy effects should induce a lag of 88 minutes.  Because the observed lag of 16 minutes is intermediate between 0 and 88 minutes, the joint observations reveal structure in the interplanetary cosmic-ray density that is consistent with a combination of simultaneous temporal variations and non-simultaneous variations with direction (i.e., anisotropy). The research is supported in part by a TA/RA scholarship (active recruitment) of Chiang Mai University and Thailand Science Research and Innovation via Research Team Promotion Grant RTA6280002.

How to cite: Kittiya, E., Nuntiyakul, W., Seripienlert, A., Evenson, P., Saiz, A., Ruffolo, D., and Oh, S.: Cosmic Ray Flux Correlation between McMurdo and Jang Bogo Neutron Monitor Stations vs. Time Lag, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4215, https://doi.org/10.5194/egusphere-egu22-4215, 2022.

EGU22-4352 | Presentations | ST1.6

Diurnal Dips and Forbush Decreases in Galactic Cosmic Rays Observed at High Cutoff Rigidity 

Chanoknan Banglieng, David Ruffolo, Alejandro Sáiz, Warit Mitthumsiri, Tanin Nutaro, Marc L. Duldig, and John E. Humble

A Forbush decrease (FD) is the decrease in Galactic cosmic ray (GCR) flux, e.g., as observed by a neutron monitor count rate, in association with a coronal mass ejection (CME) and/or its shock. The FD amplitude is known to decrease at higher cutoff rigidity. During Solar Cycle 24, the Mawson neutron monitor in Antarctica, with a low (atmosphere-limited) cutoff rigidity of ~1 GV, observed numerous FDs, while the Princess Sirindhorn Neutron Monitor (PSNM) located near the Earth's equator at Doi Inthanon, Thailand, with the world’s highest geomagnetic cutoff rigidity (17 GV), observed only a fraction of these as FDs.  Instead, we find that the shock arrival is often followed by repeated dips in the PSNM count rate at only certain times of day, while the GCR flux from other directions remains near the pre-shock level.  We refer to decreases of this type as diurnal dips.  In this work, we have surveyed FDs and diurnal dip events observed by PSNM and the dependence of their maximum amplitude on the solar wind speed, ICME speed, and interplanetary magnetic field.  We acknowledge logistical support from Australia's Antarctic Program for operating the Mawson NM and support from the National Astronomical Research Institute of Thailand and grant RTA6280002 from Thailand Science Research and Innovation.

How to cite: Banglieng, C., Ruffolo, D., Sáiz, A., Mitthumsiri, W., Nutaro, T., Duldig, M. L., and Humble, J. E.: Diurnal Dips and Forbush Decreases in Galactic Cosmic Rays Observed at High Cutoff Rigidity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4352, https://doi.org/10.5194/egusphere-egu22-4352, 2022.

EGU22-5376 | Presentations | ST1.6

Boron-coated straw detector technology as an alternative to helium-3 and boron trifluoride based proportional counters for ground level neutron monitoring: a design study. 

Michael Aspinall, Cory Binnersley, Steve Bradnam, Stephen Croft, Malcolm Joyce, Lee Packer, and Jim Wild

The global network of neutron monitors comprises predominantly of the monitor standardised by Carmichael in 1964, the NM-64.  The design of these existing monitors and their instrumentation have changed very little over the last sixty years.  For example, their neutron detectors rely on gas filled proportional counters that are either filled with highly toxic boron trifluoride (BF3) or helium-3 (3He).  Almost the entire global supply of 3He is derived from a waste product of nuclear weapons programmes and, with the termination of such programmes and reducing nuclear weapons stockpile, the supply of 3He has become limited.  Consequently, 3He supply became strictly controlled in 2008 and its price has fluctuated since.  In some cases, new neutron monitors have reverted to BF3 filled counter tubes when the price of 3He has been at a premium.  Helium-3 filled proportional counters are also used extensively in radiation portal monitors deployed for homeland security and non-proliferation; objectives which have increased significantly over the last two decades.  The reduced production and increased demand for 3He has led to concerns over its supply and provided the research motivation for alternative neutron detection methods which are viable in terms of sensitivity, stability and gamma-rejection for certain applications.  One of these alternative technologies is based on boron-coated straws (BCS) manufactured and supplied by Proportional Technologies, Inc (PTI).  The technology is built on a patented low-cost technology that enables long copper tubes, known as ‘straws’, to be coated on the inside with a thin layer of 10B-enriched boron carbide (10B4C).  Thermal neutrons captured in the 10B are converted into secondary particles, through the 10B(n, α) reaction.  The straws can be of various diameter (circa 4 mm to 15 mm), length (up to 2 m) and shape (round, star or pie) to increase the surface area of 10B.  Multiple straws can be packed inside a 1” diameter aluminium tube acting as a single drop-in replacement for traditional 3He detectors or individually distributed directly throughout the moderating medium, thus increasing efficiency by detecting the thermal neutrons at the point that they are created.  BCS-based detectors are widely used in systems for homeland security, safeguards and neutron imaging in direct exchange for 3He tubes.  This study aims to design a neutron monitor utilising BCS technology that is cheaper, more compact and produces comparable results to the existing network of NM-64 monitors.  Monte Carlo simulations using the MCNP radiation transport code to model several BCS-based solutions and an NM-64 computational benchmark are reported.  These models are validated experimentally using a standard PTI portal monitor (PTI-110-NDME) to determine its efficiency, dieaway, deadtime and gamma rejection using a combination of bare 252Cf, AmLi and 137Cs sources.  The PTI-110-NDME consists of a 12” x 5” x 1 m high density polyethylene (HDPE) slab with thirty ~15-mm diameter straws, 93 cm active length, embedded uniformly throughout the moderator.  Funded by UK Research & Innovation (UKRI), this research is part of the Space Weather Instrumentation, Measurement, Modelling and Risk (SWIMMR) programme.

How to cite: Aspinall, M., Binnersley, C., Bradnam, S., Croft, S., Joyce, M., Packer, L., and Wild, J.: Boron-coated straw detector technology as an alternative to helium-3 and boron trifluoride based proportional counters for ground level neutron monitoring: a design study., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5376, https://doi.org/10.5194/egusphere-egu22-5376, 2022.

EGU22-5504 | Presentations | ST1.6

Characteristics of the First Ground Level Enhancement (GLE) of Solar Cycle 25 on 28 October 2021 

Athanasios Papaioannou, Athanasios Kouloumvakos, Alexander Mishev, Rami Vainio, Ilya Usoskin, Konstantin Herbst, Alexis P. Rouillard, Anastasios Anastasiadis, Jan Giesler, Robert Wimmer-Schweingruber, and Patrick Kuhl

We present an overview of the first ground-level enhancement (GLE) event of solar cycle 25, recorded on 28 October 2021 (GLE73), based on the available neutron monitor (NM) network observations and on data from near-Earth spacecraft (GOES, SOHO, SolO). The maximum increase was ~7.3% for DOMC (Dome C NM at Concordia station) and 5.4% for SOPO (South Pole) conventional NMs located on the Antarctic plateau. Bare (lead-free) NMs at the same sites detected a higher response (14.0% for DOMB and 6.6% for SOPB). The Fort Smith (FSMT) NM shows the earliest increase among the high-latitude NMs, indicating a moderate anisotropy in the first phase of the GLE event. The maximum rigidity of accelerated protons did not exceed 2.4 GV. We estimated the solar release time (SRT) of ≥1 GV protons into open magnetic field lines at ~15:40 UT.  In-situ proton observations from near-Earth spacecraft were combined with the detection of a solar flare in soft X-rays (SXRs), a coronal mass ejection (CME), radio bursts and extreme ultraviolet (EUV) observations to identify the solar origin of the GLE. Around the ≥1 GV proton SRT the CME-driven shock was located at a height of ~2.33 Rs. The timing of the EUV wave evolution towards the field lines magnetically connected to Earth seem to be in good agreement with the inferred release time of ≥1 GV protons.

How to cite: Papaioannou, A., Kouloumvakos, A., Mishev, A., Vainio, R., Usoskin, I., Herbst, K., Rouillard, A. P., Anastasiadis, A., Giesler, J., Wimmer-Schweingruber, R., and Kuhl, P.: Characteristics of the First Ground Level Enhancement (GLE) of Solar Cycle 25 on 28 October 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5504, https://doi.org/10.5194/egusphere-egu22-5504, 2022.

EGU22-5650 | Presentations | ST1.6

Coincident signals on multiple counters in a neutron monitor: Sparse vs. dense atmospheric secondary particles from cosmic ray showers 

Kullapha Chaiwongkhot, David Ruffolo, Poompong Chaiwongkhot, Alejandro Sáiz, and Chanoknan Banglieng

Neutron monitors were designed to measure atmospheric secondary neutrons from cosmic ray showers in order to track the cosmic ray flux vs. time.  Furthermore, at the Princess Sirindhorn Neutron Monitor (PSNM), an 18-counter NM64 detector at 2560-m altitude at Doi Inthanon, Thailand, the leader fraction (inverse multiplicity) inferred from time delay distribution between successive neutron events in the same counter has been used to track spectral variations.  More recent measurements of time delays between neutron events in different counters, as a function of counter separation, have confirmed that 1) the product neutrons from the interaction of a single atmospheric secondary neutron can spread among neighboring counters, with a cross-counter leader fraction that depends on whether the first counter is an end or middle counter, and 2) coincident counts between distant counters can be produced by multiple atmospheric secondary neutrons from the same primary cosmic ray, with a leader fraction that depends on whether the second counter is an end or middle counter.  Here we report on measurements of neutron signals in amplifier outputs at PSNM using a 4-channel oscilloscope, in order to further investigate these phenomena.  For a pair of neighboring counters located at the edge of the counter array, we find roughly equal event rates in either neighbor following a neutron trigger in one of them, implying that the difference in leader fraction relates to the base count rate of the first counter and is therefore lower if that is an end counter. In addition, an FPGA-based readout system was developed for more efficient collection of neutron events on two distant counters (Tubes 2 and 18) that were coincident within a 250-microsecond time window, while also monitoring Tube 10 in between.  The time distributions and neutron multiplicities indicate that a small fraction of the cosmic ray events that triggered both Tubes 2 and 18 also led to neutron events on Tube 10 with an enhanced rate of high multiplicity, indicating a few air shower events that densely “carpeted” the neutron monitor, while the majority of such coincidences apparently involved a sparse distribution of isolated secondary particles near Tube 2 and near Tube 18 and not near the intermediate Tube 10, which is consistent with a cross-counter leader fraction dependence on the count rate of the second counter.  This research was supported by the postdoctoral research sponsorship of Mahidol University, Thailand, by grant RTA6280002 from Thailand Science Research and Innovation, and by grant NSRF from the Program Management Unit for Human Resources & Institutional Development, Research and Innovation, NXPO, Thailand [grant number B05F640051]. 

How to cite: Chaiwongkhot, K., Ruffolo, D., Chaiwongkhot, P., Sáiz, A., and Banglieng, C.: Coincident signals on multiple counters in a neutron monitor: Sparse vs. dense atmospheric secondary particles from cosmic ray showers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5650, https://doi.org/10.5194/egusphere-egu22-5650, 2022.

EGU22-6352 | Presentations | ST1.6

Multiple interactions in a Neutron Monitor 

Pierre-Simon Mangeard, John Clem, Paul Evenson, Waraporn Nuntiyakul, David Ruffolo, Alejandro Sáiz, Achara Seripienlert, and Surujhdeo Seunarine

The flux of low-energy (GeV-range) Galactic cosmic rays at Earth is modulated by the long term magnetic variations of the Sun (11-year sunspot cycle and 22-year magnetic solar cycle). This process known as Solar modulation is most pronounced at 1 GeV and below. However, it also operates at much higher energy, still exhibiting solar magnetic polarity dependence. For the last decades, ground-based neutron monitors provided valuable observations of the solar modulation up to a rigidity cutoff of about 17 GV. To extend the energy range of the neutron monitor observations, we recently upgraded the electronics of the Princess Sirindhorn Neutron Monitor in Thailand (PSNM, the operating neutron monitor at the highest geomagnetic rigidity cutoff) to record complex combinations of hits in multiple proportional counters. We present here the detection of multiple-hit events recorded at the PSNM. We discuss these observations with the help of a detailed Monte-Carlo simulation of energetic neutrons interacting in the detector. Finally, we estimate the nucleonic spectrum of the atmospheric secondary particles at the altitude of the detector.

How to cite: Mangeard, P.-S., Clem, J., Evenson, P., Nuntiyakul, W., Ruffolo, D., Sáiz, A., Seripienlert, A., and Seunarine, S.: Multiple interactions in a Neutron Monitor, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6352, https://doi.org/10.5194/egusphere-egu22-6352, 2022.

EGU22-11286 | Presentations | ST1.6

Integral fluences of GLEs: A new full reconstruction 

Ilya Usoskin, Sergey Koldobskiy, and Gennady Kovaltsov

For many reasons, from solar physics to terrestrial and engineering applications, it is important to estimate the total fluences of solar energetic particles (SEPs) especially for the strongest hard-spectrum events known as ground-level enhancements (GLEs). Here we present a revised reconstruction of the SEP spectral fluences using a recently developed probabilistic Monte-Carlo method, applied to major GLE events of the last decades. The method utilizes data from the ground-based neutron-monitor network in the higher-energy range and revised space-borne/ionospheric data for the lower-energy part. The fluences are reconstructed along with realistic uncertainty estimates which appear large for weak events and small for strong events.

How to cite: Usoskin, I., Koldobskiy, S., and Kovaltsov, G.: Integral fluences of GLEs: A new full reconstruction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11286, https://doi.org/10.5194/egusphere-egu22-11286, 2022.

EGU22-11343 | Presentations | ST1.6

Characteristics of a long-lived CIR and analytical modelling of the corresponding depression in the GCR flux 

Mateja Dumbovic, Bojan Vrsnak, Bernd Heber, Manuela Temmer, Patrick Kuhl, and Anamarija Kirin

We observe a long-lived CIR recurring in 27 consecutive Carrington rotations 2057-2083 in the time period from June 2007 - May 2009. We characterize the in situ measurements of this long-lived CIR as well as the corresponding depression in the GCR count observed by SOHO/EPHIN, and analyze them throughout different rotations. We find that the inverted GCR count time-profile correlates well with that of the flow speed throughout different rotations. We perform a statistical analysis and find the GCR count amplitude correlated to the peak in the magnetic field and flow speed, as expected based on previous statistical studies. In order to characterize a generic CIR profile for modelling purposes, we perform the superposed epoch analysis using relative values of the key parameters. Based on the observed properties we propose a simple analytical model starting from the basic Fokker-Planck equation. We employ a convection-diffusion GCR propagation model and apply it to the solar wind and interplanetary magnetic field properties observed for the analyzed long-lived CIR. Our analysis demonstrates a very good match of the model results and observations.

How to cite: Dumbovic, M., Vrsnak, B., Heber, B., Temmer, M., Kuhl, P., and Kirin, A.: Characteristics of a long-lived CIR and analytical modelling of the corresponding depression in the GCR flux, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11343, https://doi.org/10.5194/egusphere-egu22-11343, 2022.

EGU22-13123 | Presentations | ST1.6

Galactic cosmic rays as signatures of interplanetary transients 

Mateja Dumbovic

Coronal mass ejections (CMEs), interplanetary shocks, and corotating interaction regions (CIRs) drive heliospheric variability, causing various interplanetary as well as planetary disturbances. One of their very common in-situ signatures are short-term reductions in the galactic cosmic ray (GCR) flux (i.e. Forbush decreases), which are measured by ground-based instruments at Earth and Mars, as well as various spacecraft throughout the heliosphere (most recently by Solar Orbiter). In general, interplanetary magnetic structures interact with GCRs producing depressions in the GCR flux. Therefore, different types of interplanetary magnetic structures cause different types of Forbush decreases, allowing us to distinguish between them. With new modelling efforts, as well as observational analysis we are one step closer in utilizing GCR measurements to provide information on interplanetary transients, especially where other measurements (e.g. plasma, magnetic field) are lacking.

How to cite: Dumbovic, M.: Galactic cosmic rays as signatures of interplanetary transients, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13123, https://doi.org/10.5194/egusphere-egu22-13123, 2022.

EGU22-13288 | Presentations | ST1.6

Measuring neutron monitor multiplicities at SANAE 

Du Toit Strauss

We present new results of the neutron monitor (NM) multiplicity, as measured by the SANAE NM with updated electronics, down to 10 microseconds. We identify the high-multiplicity component, formed when high-energy particles interact with the NM and produce multiple neutrons in the lead producer. This component is absent in the lead-free monitors and is absent when testing the leaded NM with a low-energy neutron source. We study the pressure dependence of both the high- and low-multiplicity components, as well as the ratio thereof. We show how this ratio, as a proxy for the energy spectrum of atmospheric particles incident on the NM, changes during a relatively small Forbush decrease observed in November 2021.

How to cite: Strauss, D. T.: Measuring neutron monitor multiplicities at SANAE, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13288, https://doi.org/10.5194/egusphere-egu22-13288, 2022.

EGU22-1608 | Presentations | ST1.7

High-frequency waves driven by pickup ion ring-beam distributions in the outer heliosheath 

Kaijun Liu, Ameneh Mousavi, and Sina Sadeghzadeh

Scattering of pickup ion ring-beam distributions in the outer heliosheath is a fundamental element in the spatial retention scenario of the energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary EXplorer (IBEX). According to our earlier linear instability analysis, pickup ion ring-beam distributions trigger magnetic field-aligned, right-hand polarized unstable waves in two separate frequency ranges which are near and far above the proton cyclotron frequency, respectively. We have performed hybrid simulations to study the unstable waves near the proton cyclotron frequency. However, the high-frequency waves well above the proton cyclotron frequency are beyond the reach of hybrid simulations. In the present study, particle-in-cell simulations are carried out to investigate the parallel- and anti-parallel-propagating high-frequency waves excited by the outer heliosheath pickup ions at different pickup angles as well as the scattering of the pickup ions by the waves excited. In the early stages of the simulations, the results confirm the excitation of the parallel-propagating, right-hand polarized high-frequency waves as predicted by the earlier linear analysis. Later in the simulations, enhanced anti-parallel-propagating modes also emerge. Furthermore, the evolution of the pickup ion ring-beam distributions of the selected pickup angles reveals that the high-frequency waves do not significantly contribute to the pickup ion scattering. These results are favorable regarding the plausibility of the spatial retention scenario of the IBEX ENA ribbon.

How to cite: Liu, K., Mousavi, A., and Sadeghzadeh, S.: High-frequency waves driven by pickup ion ring-beam distributions in the outer heliosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1608, https://doi.org/10.5194/egusphere-egu22-1608, 2022.

EGU22-3325 | Presentations | ST1.7

The Dispersive Nature of the Heliospheric Termination Shock 

Bertalan Zieger, Joe Giacalone, Marc Swisdak, Gary Zank, and Merav Opher

The Voyager spacecraft are the first man-made objects to cross the termination shock (TS), where the solar wind becomes sub-fast magnetosonic due to the interaction with the local interstellar medium. Voyager 2 observations revealed that classical single-fluid magnetohydrodynamic (MHD) or multispecies single-fluid MHD models are not sufficient to describe the microstructure of the TS and the observed nonlinear waves downstream the TS. Consequently, more sophisticated physical models, like multifluid, hybrid or fully kinetic solar wind models, are needed to capture nonlinear waves, dispersive shock waves, and ion-ion instabilities, where each ion species (and electrons) can move independently with their own bulk velocities, and the fluctuating parts of the ion velocities are often comparable to the mean velocity of the collective plasma fluid. The multifluid simulation of the TS by Zieger et al. [2015] shows a remarkable agreement with high-resolution Voyager 2 observations, reproducing not only the microstructure of the third TS crossing (TS3) but also the energy partitioning among thermal ions, pickup ions (PUI), and electrons across the shock. It was demonstrated that TS3 is a subcritical dispersive shock wave with low fast magnetosonic Mach number and high plasma ß. Here we present multifluid, hybrid, and particle-in-cell (PIC) simulations of the second TS crossing (TS2) by Voyager 2, which was somewhat stronger than TS3, with an observed compression ratio of 2.2. All three types of simulations confirm the dispersive nature of the TS in agreement with Voyager 2 observations. We conclude that TS2, just as TS3, is a subcritical dispersive shock wave with a soliton (overshoot) at the leading edge of the shock and a quasi-stationary nonlinear wave train downstream of the shock front. We compared the cross-shock electric field in the multifluid, hybrid, and PIC simulations and found a reasonable agreement. We show that the Hall electric field is dominating over the convective and ambipolar electric fields, which indicates that electrons play an important role in the shock transition. Finally, we demonstrate that the microstructure of the termination shock is controlled by dispersion rather than ion reflection, and only slightly affected by reflected solar wind ions in the hybrid and PIC simulations, which validates the multifluid model on fluid scale. The dispersive nature of the termination shock has important implications for the transition and acceleration of PUIs across the termination shock, which is revealed in the PUI distributions in our hybrid [Giacalone et al., 2021] and PIC simulations.

How to cite: Zieger, B., Giacalone, J., Swisdak, M., Zank, G., and Opher, M.: The Dispersive Nature of the Heliospheric Termination Shock, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3325, https://doi.org/10.5194/egusphere-egu22-3325, 2022.

The Voyager 1 and Voyager 2 (V1 & V2) crossings of the termination shock (TS; ~94 and ~84 AU, respectively), led to the first measurements of ions and electrons that constitute the heliosheath (HS). Their crossings of the heliopause (HP; ~122 AU and ~119 AU), pinpointed the extent of the upwind heliosphere's expansion into the Very Local Interstellar medium (VLISM). The Cassini/INCA >5.2 keV ENA images of the celestial sphere, have placed the local V1&2/LECP measurements in a global context and have led to the discovery of a high intensity and wide ENA region that encircles the celestial sphere, called “Belt” and corresponds to a “reservoir” of particles that exist within the HS. The heliosphere forms a time-dependent, roughly symmetric obstacle to the inward interstellar flow, responding within ~2-3 yrs, in both the nose and anti-nose directions to the outward propagating solar wind changes through the solar cycle. The shape of the ion energy spectra plays a critical role in determining the pressure balance and acceleration mechanisms inside the HS. Energy spectra from ~10 eV to 344 MeV show that the PUIs dominate the total pressure distribution inside the HS, but suprathermal ions provide a significant contribution that cannot be neglected, revealing that >5.2 keV ENAs serve as important indicators of the acceleration processes that the parent H+ population undergoes inside the HS, thus imposing a key constraint on any future interpretation concerning the HS dynamics. The combination of ENAs and ions in the HS show that the plasma beta is >>1, the magnetic field upstream at the heliopause required to balance the pressure from the HS is >0.5 nT (V1 direction) and ~0.67 nT (V2 direction) and that the neutral Hydrogen density is ~0.12/cm3. These inferred values are consistent with measurements from both V1 and V2 spacecraft. Energetic ion measurements from V1/LECP in and beyond the HP show an average radial inflow of 40-139 keV ions for ~10 AU inside the HS and an average radial outflow over a spatial range of ~28 AU past the HP. These particles correspond to an ion population leaking from the HS into interstellar space, most likely due to the flux tube interchange instability at the boundary and provide a direct observation of the communication between the HS and the VLISM. They may also provide an important constraint for future models that aim to explain the <6 keV ENA ribbon fluxes (measured from the IBEX mission), which are likely formed from the neutralization of energetic pickup ions gyrating in the IS magnetic field outside the HP, reflecting (in part) those ion distributions that are responsible for the formation of this unexpected structure.

How to cite: Dialynas, K., Krimigis, S., Decker, R., and Hill, M.: Highlights of the combination of “Ground truth” >28 keV in-situ ions from the Voyagers and >5.2 keV ENAs from Cassini in the study of the global heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4316, https://doi.org/10.5194/egusphere-egu22-4316, 2022.

EGU22-6402 | Presentations | ST1.7

Interstellar Neutral He Parameters from Crossing Parameter Tubes with the Interstellar Mapping and Acceleration Probe (IMAP) informed by 10 Years of Interstellar Boundary Explorer (IBEX) Observations 

Nathan Schwadron, Eberhard Moebius, David McComas, Jon Bower, Maciek Bzowski, Stephen Fuselier, David Heirtzler, Marzena Kubiak, Marty Lee, Fatemeh Rahmanifard, Justyna Sokol, Pawel Swaczyna, and Reka Winslow

The Sun’s motion relative to the surrounding interstellar medium leads to an interstellar neutral (ISN) wind through the heliosphere. For several species, including He, this wind is moderately depleted by ionization and can be analyzed in-situ with pickup ions and direct neutral atom imaging.  Since 2009, observations of the wind at 1 AU with the Interstellar Boundary Explorer (IBEX) have returned a precise 4-dimensional parameter tube for the flow vector (speed VISN, longitude λISN, and latitude βISN) and temperature TISN of interstellar He in the local cloud, which organizes VISN, λISN, and TISN as a function of λISN, and the local flow Mach number (Vth−ISN/VISN).  We refer to this functional dependence as the 4D IBEX parameter tube. On IBEX, the limitation of measuring the ISN flow observations to nearly perpendicular to the Earth-Sun line limits the range of observations in ecliptic longitude to ∼ 30º.  This limitation results in large uncertainties along the IBEX parameter tube and relatively small uncertainties across the parameter tube.   Over the past three years, IBEX operations were modified to let the spin axis pointing of IBEX drift to the maximum offset (7º) west of the Sun, which is the limit for the IBEX spacecraft. This expansion of the IBEX viewing helps break the degeneracy of the ISN parameters along the 4D IBEX parameter tube. It complements the full χ-square-minimization to obtain the ISNs parameters through comparison with detailed models of the ISN flow. The next generation IBEX-Lo sensor on IMAP will be mounted on a pivot platform, enabling IMAP-Lo to follow the ISN flow over almost the entire spacecraft orbit around the Sun.  A near-continuous set of 4D parameter tubes on IMAP will be observed for He, and for O, Ne, and H that cross at varying angles in the full ISN parameter space. This analysis substantially reduces the flow parameter uncertainties for these species and mitigating systematic uncertainties, such as those from ionization effects and the presence of secondary components. We discuss implications of these measurements for understanding our environment and its relationship to the structure of the local interstellar medium. Thus, we discuss how IMAP will probe the interstellar neutral gas flow in detail to derive the precise parameters of the interstellar flow and relate these conditions to understand our place within the interstellar medium. 

How to cite: Schwadron, N., Moebius, E., McComas, D., Bower, J., Bzowski, M., Fuselier, S., Heirtzler, D., Kubiak, M., Lee, M., Rahmanifard, F., Sokol, J., Swaczyna, P., and Winslow, R.: Interstellar Neutral He Parameters from Crossing Parameter Tubes with the Interstellar Mapping and Acceleration Probe (IMAP) informed by 10 Years of Interstellar Boundary Explorer (IBEX) Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6402, https://doi.org/10.5194/egusphere-egu22-6402, 2022.

EGU22-6502 | Presentations | ST1.7

Filtration and Scattering of Interstellar Neutral Helium beyond the Heliopause 

Paweł Swaczyna, Maciej Bzowski, Stephen Fuselier, André Galli, Jacob Heerikhuisen, Marzena Kubiak, David McComas, Eberhard Möbius, Fatemeh Rahmanifard, Nathan Schwadron, and Eric Zirnstein

The pristine very local interstellar medium (VLISM) is not available for in situ observations even with the Voyager spacecraft because the influence of the heliosphere on the VLISM plasma extends up to several hundred au from the Sun. Therefore, observations of interstellar neutral (ISN) helium, the species least modified at the heliospheric boundaries, are used to determine the pristine VLISM flow speed, direction, and temperature. For more than one solar cycle, the Interstellar Boundary Explorer (IBEX) has sampled ISN helium atoms at 1 au, significantly reducing the statistical uncertainties of the ISN helium flow parameters. Launching in 2025, the Interstellar Mapping and Acceleration Probe (IMAP) will further lower these uncertainties thanks to the utilization of a pivot platform, which provides a range of viewing orientations and reduces the parameter degeneracy seen from IBEX data. Even though interstellar helium is the least modified ISN species, recent studies show that the ISN helium flux is affected by charge exchange and elastic collisions beyond the heliopause. Charge exchange collisions outside the heliopause filter the primary ISN helium and produce a secondary population from perturbed He+ ions in the interstellar plasma. The secondary helium population, originally called the Warm Breeze, was discovered from IBEX observations. Moreover, the distribution function of the primary ISN helium population is modified by elastic collisions with slowed down and heated plasma ahead of the heliopause. Consequently, the combined primary and secondary ISN helium populations at 1 au are complex and cannot be separated. Furthermore, the modifications of the population properties are larger than the statistical uncertainty of IBEX observations. We use global heliosphere models to estimate the magnitude of the filtration and scattering caused by charge exchange and elastic collisions. Together with other sources of information about the VLISM, these estimates allow us to assess the pristine VLISM conditions outside of heliosphere influences. 

How to cite: Swaczyna, P., Bzowski, M., Fuselier, S., Galli, A., Heerikhuisen, J., Kubiak, M., McComas, D., Möbius, E., Rahmanifard, F., Schwadron, N., and Zirnstein, E.: Filtration and Scattering of Interstellar Neutral Helium beyond the Heliopause, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6502, https://doi.org/10.5194/egusphere-egu22-6502, 2022.

EGU22-11016 | Presentations | ST1.7

Recent results from neutral beam source calibration by means of the novel Absolute Beam Monitor 

Jonathan Gasser, André Galli, and Peter Wurz

The IMAP mission by NASA is dedicated to extending the physical understanding of our heliosphere and its interaction with the interstellar medium by enhancing and refining the results obtained from IBEX. The neutral atom analysis instrument IMAP-Lo will observe and map fluxes of low-energy heliospheric neutral atoms (ENAs) and interstellar neutral (ISN) H, D, He, O and Ne with energies as low as 10 eV up to 1000 eV.

The instrument testing and calibration with a neutral atom beam is foreseen in the MEFISTO test facility for ion and neutral particle instruments at the University of Bern. MEFISTO is equipped with an electron-cyclotron resonance ion source that provides ion beams at a beam energy 3keV/q up to 100 keV/q. The beam fed into the test chamber is decelerated to 10 eV/q – 3 keV/q and effectively neutralized in a removable neutralization stage via surface reflection on a highly polished single crystal tungsten surface. The relative neutral beam intensity is permanently monitored via the neutralizing surface current. The neutralization process induces a considerable reduction of particle kinetic energy and conical widening of the neutral beam.

Thus, one key improvement for the calibration of a neutral atom instrument such as IMAP-Lo is to be able to measure the absolute neutral particle flux and beam energy into the instrument in the test chamber. To achieve this goal, the Absolute Beam Monitor (ABM) was developed recently.

The ABM is a dedicated laboratory device for absolute neutral particle flux measurements below 3 keV and coarse kinetic energy determination. Neutrals entering the ABM aperture strike a single crystal W conversion surface at grazing angle and are reflected into a channeltron to generate a stop pulse. The simultaneous monitoring of secondary electrons released at the W surface as start signal, the stop signal and the coincidence event rate allows inferring the rate of neutral atoms into the ABM aperture. The average neutral beam energy is obtained from the start-stop time-of-flight spectrum. The ABM is the first and so far the only device to measure the absolute neutral atoms flux in this low energy range below a few 100 eV. It serves as a primary standard for gauging the MEFISTO neutral beam source.

We report on recent calibration results of neutral H, He, O, Ne beams in the 10 eV – 1 keV energy range with the ABM in MEFISTO.

How to cite: Gasser, J., Galli, A., and Wurz, P.: Recent results from neutral beam source calibration by means of the novel Absolute Beam Monitor, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11016, https://doi.org/10.5194/egusphere-egu22-11016, 2022.

The heliosphere surrounding our solar system is formed by the interaction between the solar wind and the local interstellar medium as the Sun moves through interstellar space. With dimensions on the order of hundreds to potentially thousands of au, it is extremely difficult to pinpoint the 3D structure of the heliosphere and its boundaries, and the properties of the plasma within it. However, we can remotely measure the properties of the heliosphere with energetic neutral atoms (ENAs) which are created as a product of charge exchange between interstellar neutrals and ions within the solar wind plasma. ENAs can propagate hundreds of au before ionizing, allowing us to remotely view the distant boundaries of the heliosphere.

The Interstellar Boundary Explorer (IBEX) mission, a NASA smaller explorer mission which has been measuring ENA fluxes at ~0.5-6 keV for more than a solar cycle, has revealed at least two separate sources of ENAs: the “ribbon” of enhanced ENA fluxes forming a narrow, circular band across the sky, and the “globally distributed flux” (GDF) that forms lower intensity, broad features near the nose and tail of the heliosphere. While it is believed that the ribbon is formed from secondary ENAs from outside the heliopause, and ENAs from the inner heliosheath inside the heliopause are a major contributor to the GDF, it is not clear exactly how much of the GDF may originate outside the heliopause, and how much of the flux observed in the Ribbon is from the GDF itself. To help solve this issue, we present recent developments in our understanding of the ribbon vs. GDF sources from both IBEX data analysis and modeling perspectives. Moreover, with the upcoming IMAP mission set to launch in 2025, we provide insight into how IMAP’s enhanced capabilities may improve our current understanding of the heliosphere.

How to cite: Zirnstein, E.: Differentiating the Ribbon and Globally Distributed ENA Flux in IBEX Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13186, https://doi.org/10.5194/egusphere-egu22-13186, 2022.

As the Sun moves through its local galactic neighborhood, it disturbs the ionized component of interstellar matter, forming a complex bow-wave structure of a slowed and heated, magnetized plasma, flowing past the heliosphere. This region is called the outer heliosheath. The neutral component of interstellar matter is in equilibrium with the ionized component far ahead of the heliosphere, but within the outer heliosheath it decouples kinematically from the perturbed plasma. A complex interaction begins, mostly by charge exchange, between the ions and the neutral atoms, and as a result, a new population of neutral atoms is created, with kinematic parameters similar to that of the surrounding plasma. In addition, elastic collisions operate, additionally modifying both the original primary and the secondary population of neutral. Both the primary and the secondary populations penetrate inside the heliosphere and can be directly sampled at 1 au. We will review results of observations of these populations obtained from IBEX-Lo and results of modeling of the secondary populations of interstellar hydrogen, helium, and oxygen in the outer heliosheath. We will illustrate how these populations can be better observed owing to enhanced capabilities of the planned IMAP-Lo instrument and demonstrate how they can be leveraged to resolve the primary and secondary populations, and investigate the properties of local interstellar matter in the immediate neighborhood of the Sun.

How to cite: Bzowski, M.: The primary and secondary populations of interstellar neutral gas as seen now by IBEX and in the future by IMAP, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13535, https://doi.org/10.5194/egusphere-egu22-13535, 2022.

EGU22-13568 | Presentations | ST1.7

Pressure Balance at the Heliosphere Boundary and in the Local Interstellar Cloud 

Eberhard Möbius and Jeffey Linsky

The pressures exerted by the solar wind from the inside and the interstellar medium from the outside control the size and shape of the heliosphere. Magnetic fields and cosmic rays play important roles to varying extents on both sides. We will assess the pressure balance by assembling the relevant component pressures in the (inner) heliosheath inside the heliopause, in the Very Local Interstellar Medium (VLISM, interstellar medium affected by the presence of the heliosphere or outer heliosheath), and in the Local Interstellar Cloud (LIC) unaffected by the heliosphere. We take the cosmic ray pressure from Voyager observations, which don’t show substantial gradients beyond the heliopause. The remaining pressure on the heliopause from inside is due to thermal and suprathermal ions in the subsonic solar wind, obtained from IBEX and INCA ENA observations and Voyager in situ measurements at the higher energies.

Besides cosmic rays, the pressure in the undisturbed LIC is composed of magnetic field pressure taken from IBEX Ribbon observations and related modeling. Thermal and turbulent pressures are based on H and He neutral and ion densities from pickup ion and interstellar gas flow observations, combined with the temperature and turbulent speed from absorption-line observations. The total LIC pressure in its rest frame is almost 40% lower than the pressure inside the heliopause, whereas adding the full ram pressure based on the LIC velocity relative to the Sun exceeds that pressure substantially. We estimate the likely effective pressure on the heliopause by combining the compressed interstellar magnetic field, as measured by Voyager, and the compressed and heated interstellar plasma, resorting to results from global heliospheric modeling. An interesting result of these pressure comparisons is that the effective ram pressure on the heliopause is somewhat larger than the combined magnetic field, thermal, and turbulent pressure in the LIC, which points to the importance of the LIC ram pressure for the shape of the heliosphere. We also compare the LIC pressure with the gravitational pressure on the galactic disk at the location of the Sun.

How to cite: Möbius, E. and Linsky, J.: Pressure Balance at the Heliosphere Boundary and in the Local Interstellar Cloud, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13568, https://doi.org/10.5194/egusphere-egu22-13568, 2022.

Space plasmas reside in non-equilibrium stationary states described by kappa distributions. The high-energy asymptotic behavior of kappa distributions leads to a power-law relationship of the energy-flux spectra; this relationship, when observed, can be analyzed for determining the thermodynamic parameters of the plasma. In the presented analysis, we use Energetic Neutral Atom (ENA) observations from the IBEX-Hi sensor, converted to the corresponding proton plasma spectra of the inner heliosheath, and timestamped with the ENA creation time. We, then, model the proton spectra with kappa distributions and derive the sky maps of the (radially averaged) values of temperature, density, kappa, and other thermodynamic parameters of the proton plasma in the inner heliosheath. We examine the variations of the determined thermodynamics and whether a correlation exists with solar activity during the 24th solar cycle.

How to cite: Livadiotis, G.: Thermodynamics of the proton plasma in the inner heliosheath during the 24th solar cycle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13574, https://doi.org/10.5194/egusphere-egu22-13574, 2022.

EGU22-564 | Presentations | ST1.8

Study on the association of solar gyroresonance emission sources with brightness temperature intensification at 17 GHz 

Abimael Amaro, Marlos Rockenbach da Silva, and Joaquim Eduardo Rezende Costa

Remarkable works done in the last decades by many authors on the solar gyroresonance mechanism have illuminated the way to establish the relationship between this form of emission and magnetic fields in the solar atmosphere and to know the magnetic nature of the middle and upper layers of the active regions. Despite all these advances, solar physics still needs a direct means (without magnetograms) of identifying the sources of gyroresonance emission.
In search of a solution to this problem, we used solar images at 17 GHz synthesized by the Nobeyama Radioheliograph (NoRH) to map the likely sources of gyroresonance. 
To achieve this result, we first hypothesized that gyroresonance and bremsstrahlung mechanisms can generate a large brightness temperature intensification due to the close relationship such mechanisms have with magnetic fields and because of the role of the magnetic field in controlling the brightness of the solar atmosphere in the radiofrequency range.
To test this hypothesis regarding the gyroresonance process, we selected 8 large active regions (ARs) among the HMI magnetograms generated by the Solar Dynamics Observatory (SDO) corresponding to the 1st half of the 24th solar cycle.  We then analyzed each AR through its magnetogram and its image at 17 GHz. Aiming to verify, in these radio maps, whether there is a correspondence between brightness bumps and parameters associated with gyroresonance emission, we constructed three categories of brightness maps for each active region, respectively presenting the field of: brightness temperature in BT maps, brightness temperature gradient in BTG maps, and brightness temperature gradient to brightness temperature ratio in BTG/BT maps. Such parameters are the characteristic circular polarization, whose modulus is greater than 30%, and characteristic magnetic field strengths, associated with the gyroresonance radiation at 17 GHz for 3rd and 4th harmonics. Such a step also aimed to verify which of these categories would best map the putative sources of gyroresonance emission.
On these maps, we then plotted the contours of the characteristic parameters. 
For each AR, we also obtained the degree of correlation between its brightness variables and the characteristic polarization. We then observed that the contours of characteristic magnetic field strengths are predominantly enveloped by the area of the brightness bumps, while the contours of the characteristic polarization fit well to such areas, being better fitted to the relative bumps (in the BTG/BT maps). In the statistical analysis, we observe that for each active region, there is a predominance of strong correlations between the brightness variables and the modulus of the characteristic polarization. Such correlation tends to be highest for the brightness temperature. For each brightness variable, the highest correlations tend to occur for the predominant polarization direction of the active region.
The data, therefore, indicate a high probability that the gyroresonance emission mechanism was at least one of the important causes of the radio bumps produced in the observed active regions.

How to cite: Amaro, A., Rockenbach da Silva, M., and Rezende Costa, J. E.: Study on the association of solar gyroresonance emission sources with brightness temperature intensification at 17 GHz, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-564, https://doi.org/10.5194/egusphere-egu22-564, 2022.

EGU22-730 | Presentations | ST1.8

Estimation of the solar wind extreme events. 

Carlos Larrodera, Lidia Nikitina, and Consuelo Cid

This research provides an analysis of extreme events in the solar wind and in the magnetosphere due to disturbances of the solar wind. Extreme value theory has been applied to a 20-year data set from the Advanced Composition Explorer spacecraft for the period 1998–2017. The solar proton speed, solar proton temperature, solar proton density, and magnetic field have been analyzed to characterize extreme events in the solar wind. The solar wind electric field, vBz has been analyzed to characterize the impact from extreme disturbances in the solar wind to the magnetosphere. These extreme values were estimated for 1-in-40- and 1-in-80-year events, which represent two and four times the range of the original data set. The estimated values were verified in comparison with measured values of extreme events recorded in previous years. Finally, our research also suggests the presence of an upper boundary in the magnitudes under study.

How to cite: Larrodera, C., Nikitina, L., and Cid, C.: Estimation of the solar wind extreme events., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-730, https://doi.org/10.5194/egusphere-egu22-730, 2022.

EGU22-939 | Presentations | ST1.8

Covariation of solar granulation size and sunspot indices in activity cycle 24 

Alexey Sharov and Arnold Hanslmeier

New theoretical arguments and empirical evidence for correlated changes in sun granulation size and sunspot indices were obtained during this two-year study using blue continuum image data acquired by the Hinode solar optical telescope in 2006-2016 and simultaneous time series of daily sunspot numbers (SSN) and areas (SSA). An original set of simple scaling equations linking the relative variation in the average size of granular cells to the sum change in the total number of granular cells, SSA and surface gravity was written under the assumption that at the height of the blue continuum formation, the entire surface of the Sun is the sum of the areas of granular cells, pores and sunspots. The magnitudes of relative changes in the horizontal size of granular cells due to variations in global solar parameters were estimated and it was shown that variations in the SSA have the dominant influence on variations in the mean granular size. Periodic spurious changes in the mean granular size due to the sun's variable tilt with respect to the telescope and apparent changes in rotational speed and surface gravity were also mentioned.

Our empirical research focussed on the automatic identification and precise morphometric measurements of granular cells in high-resolution Hinode images using an efficient marker-controlled watershed segmentation algorithm. A total of seven image sequences with a 30-, 27- and 1-day cadence, all of which contained 840 images, were compiled, processed and corrected with regard to the variable sun-earth distance and heliographic coordinates. The resultant granulation parameters, including mean area, equivalent diameter, extent and contrast were compared to SSN and SSA data using temporal cross-correlation. An essential anti-correlation was measured between the mean size of granular cells and the daily SSN for the medium time intervals of four months, which were characterized with the optimal orbital conditions for the imaging of solar granulation. The decrease in the cellular scale by 3% with the increase in the average SSN index of 20%, was revealed for both ascending and descending phases of the 24th activity cycle, while the average contrast characterizing image quality remained almost unchanged. The approximately 14-day delay in the cause-effect relationship between the SSN and the granulation scale was revealed and a plausible explanation for this delay was given.

In the quiet sun at the disk centre, the mean equivalent diameter of granules was measured at 1.37 arcseconds, while the same parameter for granular cells was given as 2.06 arc seconds, which was in good agreement with the results of other researchers. In the close vicinity of sunspots, the mean size of granular cells decreased by a few percent, while the width of intergranular lanes decreased by 60%, indicating the existence of bright rings with higher temperatures around these sunspots. The significance of all these observations is that they confirm the results of the predecessors, positively support the 70-year-old hypothesis about the dependence of granulation properties on the sunspot cycle, and stimulate the use of the granulation scale as a cyclical proxy for solar activity over medium-term periods.

How to cite: Sharov, A. and Hanslmeier, A.: Covariation of solar granulation size and sunspot indices in activity cycle 24, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-939, https://doi.org/10.5194/egusphere-egu22-939, 2022.

EGU22-1364 | Presentations | ST1.8

Variations of alpha particle parameters across corotating rarefaction regions 

Tereza Durovcova, Jana Safrankova, and Zdenek Nemecek

A corotating rarefaction region (CRR) is formed between the slow solar wind stream and the fast stream in front of it. It is associated with a region of small longitudinal extent on the solar surface and plasma parameters would correspond to a smooth transition between the interacting streams. However, previous studies have shown that the stream interaction can change parameters of individual solar wind components in an unexpected way. In our study, we focused on behavior of the second most abundant ionic component, alpha particles. Preliminary analysis of measurements at 1 AU revealed large variations of the alpha relative abundance (AHe) that did not correlate with the solar wind speed and alpha-proton relative drift changes. To determine the global profile of alpha properties across CRR at 1 AU, we performed the superposed epoch analysis of identified CRRs. We found continuous but spatially separated transitions of the alpha-proton relative abundance, relative drift, and alpha-proton temperature ratio from values corresponding to fast streams to those typical for slow streams. Despite the expectation that AHe would decrease from the beginning of the rarefaction, it corresponds to values usually observed in the fast solar wind for a large part of the CRR. Moreover, AHe is often enhanced near the expected stream interface. Therefore, we propose that a major part of the CRR is filled by the wind from a coronal hole and discuss various scenarios that could explain the obtained profiles of alpha particle parameters across CRRs. Finally, we use CRR observations at different radial distances from the Sun (Solar Orbiter, Ulysses, etc.) to identify effects connected with a radial evolution of these large-scale structures.

How to cite: Durovcova, T., Safrankova, J., and Nemecek, Z.: Variations of alpha particle parameters across corotating rarefaction regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1364, https://doi.org/10.5194/egusphere-egu22-1364, 2022.

EGU22-1856 | Presentations | ST1.8

A Study of Small-Scale Brightenings using EUV Data from SPICE on board Solar Orbiter 

Jenny Marcela Rodriguez Gomez, Peter Young, and Therese Kucera

Recently small-scale solar dynamic features have been observed on the Sun by Solar Orbiter/EUI (Berghmans et al. 2021; Panesar et al. 2021). These events (initially referred to as “campfires”) are small-scale heating events observed mainly in the solar corona. The Spectral Imaging of Coronal Environment (SPICE; SPICE Consortium et al. 2020) is a high-resolution imaging spectrometer that observes the Sun in extreme ultraviolet (EUV) wavelengths. This study uses L2 SPICE data (calibrated images)  to characterize and follow the evolution of these small-scale brightenings. Additionally, we use HRIEUV 174 Å on board Solar Orbiter and Stereo A datasets to have a complementary view of small-scale brightenings during the study period.

How to cite: Rodriguez Gomez, J. M., Young, P., and Kucera, T.: A Study of Small-Scale Brightenings using EUV Data from SPICE on board Solar Orbiter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1856, https://doi.org/10.5194/egusphere-egu22-1856, 2022.

Prominences and filaments are manifestations of magnetised, levitated plasma within the solar coronal atmosphere. Expanding on our previous 2.5D work presented in Jenkins & Keppens (2021), we will present a state-of-the-art magnetohydrodynamic simulation that yields the first fully 3D model to successfully unite the extreme-ultraviolet and Hydrogen-α prominence views that contain radial striations with the equivalent on-disk filaments comprised of finite width threads. Owed to the unprecedented resolution with which this simulation is carried out, we complete a full observational synthesis and provide predictions of exactly what the instruments associated with the upcoming Solar Orbiter and DKIST will observe. We then begin with an analysis of all hydromagnetic sources of the vorticity evolution and find the internal plasma dynamics to be consistent with the nonlinear development of the magnetic Rayleigh-Taylor instability. A further stability analysis that drops the strict, idealised mRTi initial conditions then enables us to tentatively characterise the preceding linear development as the general (quasi-) interchange gravitational instability. Our simulations and analyses show clearly how this universal interchange process operates, and how our results and conclusions finally unify the contradictory prominence/filament perspectives.

How to cite: Jenkins, J. and Keppens, R.: The Role of the Magnetic Rayleigh-Taylor Instability in Resolving the Solar Prominence/Filament Paradox, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2438, https://doi.org/10.5194/egusphere-egu22-2438, 2022.

EGU22-2663 | Presentations | ST1.8

Extrapolation of solar wind parameters in three-dimensions in the inner heliosphere 

Aniko Timar, Andrea Opitz, Gabor Facsko, Zsuzsanna Dalya, Gergely Koban, Nikolett Biro, Akos Madar, and Zoltan Nemeth

Solar wind parameters, such as the velocity, density or pressure of the solar wind, are one of the most important factors in space physics, and their knowledge at as many points in the heliosphere as possible contributes to a broader understanding of our solar system.

Solar wind parameters at various points in the inner heliosphere are estimated using extrapolation methods. Currently, all spacecraft measuring solar wind parameters are in the ecliptic plane, thus it is enough to extrapolate the data from space probes to other spacecraft or celestial bodies near the ecliptic. Solar Orbiter, on the other hand, will soon leave the ecliptic and reach heliocentric latitudes of 34 degrees by the end of the mission, opening a new perspective.

The ballistic method extrapolates solar wind parameters in one dimension from the point of measurement to a chosen heliospheric position. The simple ballistic model considers the average rotation period of the Sun for the extrapolation in longitude while assuming a constant solar wind velocity during radial propagation. Our improved solar wind propagation model takes into account the interaction of slow and fast solar wind by applying a pressure correction during the extrapolation.

Applying this pressure-corrected ballistic method to data from solar corona models, we determined the solar wind parameters in the heliosphere in three dimensions. The advantage of our pressure-corrected ballistic method is that it is simple, it requires little calculation and it can be easily applied to the data of solar corona models in order to obtain a fast and efficient prediction in three dimensions.

How to cite: Timar, A., Opitz, A., Facsko, G., Dalya, Z., Koban, G., Biro, N., Madar, A., and Nemeth, Z.: Extrapolation of solar wind parameters in three-dimensions in the inner heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2663, https://doi.org/10.5194/egusphere-egu22-2663, 2022.

EGU22-3464 | Presentations | ST1.8

The role of coronal shocks for accelerating solar energetic electrons 

Nina Dresing, Athanasious Kouloumvakos, Rami Vainio, and Alexis Rouillard

We study the role of Coronal Mass Ejection (CME)-driven shocks in the acceleration of solar energetic electrons. Using observations by the two STEREO spacecraft, we correlate electron peak intensities of solar energetic particle events measured in situ with various parameters of the associated coronal shocks. These shock parameters were derived by combining 3D shock reconstructions with global modeling of the corona. This technique provides also shock properties in the specific shock regions that are magnetically connected to the two STEREO spacecraft. We find significant correlations between the peak intensities and the Mach number of the shock with correlation coefficients of about 0.7, which are similar for electrons at ∼ 1 MeV and protons at > 60 MeV. Lower energy electrons < 100 keV show a smaller correlation coefficient of 0.47. The causal relationship between electron intensities and the shock properties is supported by the vanishing correlations, when peak intensities at STEREO-A are related with the Alfvénic Mach numbers at the magnetic footpoint of STEREO-B and vice versa, which yields correlation coefficients of 0.03 and -0.13 for ∼ 1 MeV and < 100 keV electron peak intensities, respectively. We conclude that the high-energy electrons are accelerated mainly by the shock, while the low energy electrons are likely produced by a mixture of flare and shock-related acceleration processes.

How to cite: Dresing, N., Kouloumvakos, A., Vainio, R., and Rouillard, A.: The role of coronal shocks for accelerating solar energetic electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3464, https://doi.org/10.5194/egusphere-egu22-3464, 2022.

EGU22-4121 | Presentations | ST1.8

Spatial Structure of CIRs 

Gergely Koban, Andrea Opitz, Zoltan Nemeth, Gabor Facsko, Akos Madar, Aniko Timar, Zsuzsanna Dalya, and Nikolett Biro

Co-rotating Interaction Regions are complex and fascianting structures in the Heliosphere that 
play an important role in space weather. They arise from the fast solar wind interacting with the 
slow solar wind streams. The interface between fast and slow solar wind is called the stream 
interface, and it is common for CIRs to produce forward shock at the leading edge and reverse 
shock at the trailing edge. CIRs often have considerable tilts in the north-south axis, owing to the magnetic 
conditions on the Sun.


Examination of the spatial structure of CIRs, – most importantly the aforementioned tilt – is not 
an easy task. We attempt a multi-spacecraft investigation in order to examine the spatial 
structure of CIRs on different distance scales. Using all available spacecraft data nearby, the tilt 
of the stream interface can be determined considering the time delays of the effects caused by 
the CIR recorded by each spacecraft. Our final aim is to improve solar wind propagation 
methods with these detailed CIR results.

How to cite: Koban, G., Opitz, A., Nemeth, Z., Facsko, G., Madar, A., Timar, A., Dalya, Z., and Biro, N.: Spatial Structure of CIRs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4121, https://doi.org/10.5194/egusphere-egu22-4121, 2022.

EGU22-4155 | Presentations | ST1.8

Spatial variation of the background solar wind in the Inner Heliosphere 

Nikolett Biro, Andrea Opitz, Zoltan Nemeth, Aniko Timar, Akos Madar, Gergely Koban, and Zsuzsanna Dalya
The importance of background solar wind is unquestionable as it carries information on the solar surface conditions and has a major role in space weather events. The current solar minimum is a perfect time period for investigations regarding this field, with several space probes providing in-situ measurements.
 
Our aim is to determine the spatial variations in the background solar wind through multi-spacecraft data analysis, including recent missions, such as Parker Solar Probe and Solar Orbiter. We adjust for the radial and longitudinal time-lags between the different spacecraft, then compare their solar wind plasma measurements. The effects of latitudinal differences between the observations is then backmapped to coronagraph imagery. The results will be useful for further analysis of inner heliospheric structures, for the improvement of propagation models, and to support the analysis of out-of-ecliptic solar wind observations.

How to cite: Biro, N., Opitz, A., Nemeth, Z., Timar, A., Madar, A., Koban, G., and Dalya, Z.: Spatial variation of the background solar wind in the Inner Heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4155, https://doi.org/10.5194/egusphere-egu22-4155, 2022.

EGU22-4178 | Presentations | ST1.8

Predicting the solar cycle amplitude with the new catalogue of hemispheric sunspot numbers 

Shantanu Jain, Tatiana Podladchikova, Astrid M. Veronig, Olga Sutyrina, Mateja Dumbović, Frédéric Clette, and Werner Pötzi

The sun’s magnetic field drives the 11-year solar cycle, and predicting its strength has practical importance for many space weather applications. Previous studies have shown that analysing the solar activity of the two hemispheres separately instead of the full sun can provide more detailed information on the activity evolution. However, the existing Hemispheric Sunspot Number data series (1945 onwards) was too short for meaningful solar cycle predictions. Based on a newly created hemispheric sunspot number catalogue for the time range 1874-2020 (Veronig et al. 2021, http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/652/A56) that is compatible with the International Sunspot Number from World Data Centre SILSO, we investigate the evolution of the solar cycle for the two hemispheres and develop a novel method for predicting the solar cycle amplitude. We demonstrate a steady relationship between the maximal growth rate of activity in the ascending phase of a cycle and its subsequent amplitude and form a 3rd order regression for the predictions. Testing this method for cycles 12-24, we show that the forecast made by the sum of the maximal growth rate from the North and South Hemispheric Sunspot number is more accurate than the same forecast from the Total Sunspot Number: The rms error of predictions is smaller by 27%, the correlation coefficient r is higher by 11% on average reaching values in the range r = 0.8-0.9 depending of the smoothing window of the monthly mean data. These findings demonstrate that empirical solar cycle prediction methods can be enhanced by investigating the solar cycle dynamics in terms of the hemispheric sunspot numbers, which is a strong argument supporting regular monitoring, recording, and analysing solar activity separately for the two hemispheres.

How to cite: Jain, S., Podladchikova, T., Veronig, A. M., Sutyrina, O., Dumbović, M., Clette, F., and Pötzi, W.: Predicting the solar cycle amplitude with the new catalogue of hemispheric sunspot numbers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4178, https://doi.org/10.5194/egusphere-egu22-4178, 2022.

EGU22-4182 | Presentations | ST1.8

The large-scale structure of the solar wind: flux conservation, radial scalings, Mach numbers, and critical distances 

Daniel Verscharen, Stuart D. Bale, and Marco Velli

One of the key challenges in solar and heliospheric physics is to understand the acceleration of the solar wind. As a super-sonic, super-Alfvénic plasma flow, the solar wind carries mass, momentum, energy, and angular momentum from the Sun into interplanetary space. We present a framework  based on two-fluid magnetohydrodynamics to estimate the flux of these quantities based on spacecraft data independent of the heliocentric distance of the location of measurement.

Applying this method to the Ulysses dataset allows us to study the dependence of these fluxes on heliolatitude and solar cycle. The use of scaling laws provides us with the heliolatitudinal dependence and the solar-cycle dependence of the scaled Alfvénic and sonic Mach numbers as well as the Alfvén and sonic critical radii. Moreover, we estimate the distance at which the local thermal pressure and the local energy density in the magnetic field balance.

These results serve as predictions for observations with Parker Solar Probe, which currently explores the very inner heliosphere, and Solar Orbiter, which will measure the solar wind outside the plane of the ecliptic in the inner heliosphere during the course of the mission.

How to cite: Verscharen, D., Bale, S. D., and Velli, M.: The large-scale structure of the solar wind: flux conservation, radial scalings, Mach numbers, and critical distances, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4182, https://doi.org/10.5194/egusphere-egu22-4182, 2022.

EGU22-4327 | Presentations | ST1.8 | Highlight

First results from the SO/PHI instrument on Solar Orbiter 

Sami Khan Solanki, Julian Blanco, Fatima Kahil, Philipp Loeschl, Hanna Strecker, Johann Hirzberger, David Orozco Suárez, Jose Carlos Del Toro Iniesta, Joachim Woch, Achim Gandorfer, Alberto Alvarez-Herrero, Thierry Appourchaux, and Reiner Volkmer

The ESA/NASA Solar Orbiter mission, launched in February 2020, has just completed its cruise phase. During its nominal mission, it will explore the Sun and heliosphere from close up and from out of the ecliptic plane. It aims to address the overarching questions of how the Sun creates and controls the heliosphere, and why solar activity changes with time. Among the instruments onboard Solar Orbiter  is the Polarimetric and Helioseismic Imager (SO/PHI), which is the first magnetograph to leave the Sun-Earth line and to observe the Sun from different directions. Already during the cruise phase of Solar Orbiter, SO/PHI has provided a few glimpses of its capabilities, including the excellent quality of the data. In spite of the very limited amount of data gathered during cruise, a few interesting results have already been obtained. A selection of such results will be presented.

 

How to cite: Solanki, S. K., Blanco, J., Kahil, F., Loeschl, P., Strecker, H., Hirzberger, J., Orozco Suárez, D., Del Toro Iniesta, J. C., Woch, J., Gandorfer, A., Alvarez-Herrero, A., Appourchaux, T., and Volkmer, R.: First results from the SO/PHI instrument on Solar Orbiter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4327, https://doi.org/10.5194/egusphere-egu22-4327, 2022.

EGU22-4987 | Presentations | ST1.8

Removal of false alarms from solar wind predictions 

Zsuzsanna Dalya and Andrea Opitz

Solar wind propagation models using in situ plasma observations as input can be improved by removing the signatures of Interplanetary Coronal Mass Ejections (ICMEs) from the input data. ICMEs are sporadic events that propagate in a given direction, hence their signatures in the plasma data should not be extrapolated to other heliocentric longitudes. As a result, in order to improve the prediction accuracy these should be filtered out. We create dedicated ICME lists providing the exact start and end times of ICMEs to numerous space probes such as ACE, STEREO A&B, SOHO, WIND, SolO, PSP, DSCOVER, VEX, MEX, Rosetta, BepiColombo, MAVEN and Messenger. We provide solar wind plasma and magnetic field predictions to any inner heliospheric position applying the ICME filter on the input dataset this way eliminating false alarms such as false ICME signature forecasts. Our corrected predictions contribute to the investigation of the background solar wind and related fields.

How to cite: Dalya, Z. and Opitz, A.: Removal of false alarms from solar wind predictions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4987, https://doi.org/10.5194/egusphere-egu22-4987, 2022.

EGU22-5443 | Presentations | ST1.8

Large Amplitude Oscillations in Solar Filaments Caused by Solar Jets 

Reetika Joshi, Manuel Luna, Brigitte Schmieder, Fernando Moreno-Insertis, and Ramesh Chandra

Large amplitude oscillations (LAO) are often detected in filaments. Their origin has been associated with shock waves or to interaction with eruptions and jets. In this study we present  two examples of LAOs due to solar jets interaction with filaments on February 3-5 2015 and March 14 2015.  The filament eruption on March 14 was followed by a two step filament eruption along with a CME and become the strong geomagnetic storm of Solar Cycle 24 on 17 March 2015. These LAOs are  analysed by using time-distance diagnostics. The detected LAOs have periods of around 60 minutes and are damped after three oscillations. The observations are consistent with the results of a recent developed theoretical model of jet and filament interaction. The jets are associated with very weak flares which did not initiate any EUV wave. The role of waves as trigger of these oscillations can be discarded for these two events. 

 

How to cite: Joshi, R., Luna, M., Schmieder, B., Moreno-Insertis, F., and Chandra, R.: Large Amplitude Oscillations in Solar Filaments Caused by Solar Jets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5443, https://doi.org/10.5194/egusphere-egu22-5443, 2022.

EGU22-5466 | Presentations | ST1.8

Temporal evolution of the background solar wind throughout the inner heliosphere 

Andrea Opitz, Aniko Timar, Zoltan Nemeth, Zsuzsanna Dalya, Gergely Koban, Nikolett Biro, and Akos Madar

The solar wind properties at a given point in the heliosphere depend strongly on the source surface characteristics, the dynamical effects during propagation and the transient events. We study the background solar wind structures after modelling their propagation throughout the 3-dimensional heliosphere. We remove the transient events from the observations, then apply the ballistic propagation method corrected for pressure gradients at stream interactions. A detailed multi-spacecraft investigation of the radial and latitudinal effects improves our model. These results are applied to study the temporal evolution of the solar wind by excluding the spatial effects through adjusting for the timelag calculated from the spacecraft separations.

How to cite: Opitz, A., Timar, A., Nemeth, Z., Dalya, Z., Koban, G., Biro, N., and Madar, A.: Temporal evolution of the background solar wind throughout the inner heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5466, https://doi.org/10.5194/egusphere-egu22-5466, 2022.

EGU22-6088 | Presentations | ST1.8

ULF waves upstream and downstream of interplanetary shocks 

Xochitl Blanco-Cano, Primoz Kajdic, Diana Rojas-Castillo, Luis Preisser, Lan Jian, Christopher Russell, and Janet Luhmann

Interplanetary (IP) shocks can be driven in the solar wind by fast coronal mass ejections and by the interaction of fast solar wind with slow streams of plasma. These shocks can be preceded by extended wave and suprathermal ion foreshocks. We use STEREO data to study wave modes upstream and downstream of IP shocks. Understanding these waves is important because they contribute to shock acceleration processes and modify the solar wind as the shocks propagate in the heliosphere. We find that upstream regions can be permeated by whistler waves (f ~ 1 Hz) and/or ultra low frequency (ULF) right-handed waves (f~10-2–10-1 Hz). While whistlers appear to be generated at the shock, the origin of ULF waves is most probably associated with local kinetic ion instabilities. In contrast with planetary bow shocks, most IP shocks have a small Mach number (<4) and most of the upstream waves studied here are mainly transverse and no steepening occurs. Downstream of the shocks ion cyclotron and mirror mode waves can grow due to temperature anisotropy. The waves observed downstream of IP quasi-parallel shocks have larger amplitudes than waves in the regions downstream of quasi-perpendicular shocks. A variety of waves can be found in the sheath regions of IP shocks, even when IP shocks are weak, mostly for quasi-perpendicular shocks. These include ion cyclotron waves (ICW) with well defined peaks in frequency, broad spectra ICW, and mirror mode storms, which tend to occur for higher plasma beta.

How to cite: Blanco-Cano, X., Kajdic, P., Rojas-Castillo, D., Preisser, L., Jian, L., Russell, C., and Luhmann, J.: ULF waves upstream and downstream of interplanetary shocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6088, https://doi.org/10.5194/egusphere-egu22-6088, 2022.

EGU22-6620 | Presentations | ST1.8

Directional Discontinuities in the Inner Heliosphere 

Ákos Madár, Geza Erdos, Andrea Opitz, Zoltan Nemeth, Gabor Facsko, Aniko Timar, Nikolett Biro, Gergely Koban, and Zsuzsa Dalya

The Parker Solar Probe and Solar Orbiter spacecraft make whole new spatial and time scales available in the inner Heliosphere. With these new data, we study directional discontinuities that are common structures in the solar wind in this region. Their radial distribution can provide insight into the physical processes of this virtually collisionless plasma. Applying a method (Erdős & Balogh, 2008) based on minimum variance analysis to select directional discontinuities in magnetic field data, we determine their number as a function of distance from the Sun. How the directional discontinuity occurrence rate depends on the solar wind speed is also part of our analysis.

How to cite: Madár, Á., Erdos, G., Opitz, A., Nemeth, Z., Facsko, G., Timar, A., Biro, N., Koban, G., and Dalya, Z.: Directional Discontinuities in the Inner Heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6620, https://doi.org/10.5194/egusphere-egu22-6620, 2022.

EGU22-6726 | Presentations | ST1.8

Multi-Spacecraft Observations of Gradual Solar Energetic Particle Events with Enhanced 3He Abundance 

Radoslav Bucik, Glenn M. Mason, Raúl Gómez-Herrero, Maher A. Dayeh, Mihir I. Desai, Samuel T. Hart, George C. Ho, David Lario, Vratislav Krupar, Robert F. Wimmer-Schweingruber, Javier Rodríguez-Pacheco, and Tilaye T. Asfaw

Suprathermal ions from coronal jets, characterized by enhanced 3He and heavy-ion abundances, are an essential component of the seed population accelerated by coronal mass ejection (CME)-driven shocks in gradual solar energetic particle (GSEP) events. However, the mechanisms through which CME-driven shocks gain access to these suprathermal ions and produce spectral and abundance variations in GSEP events remain largely unexplored. We study GSEP events simultaneously measured on at least two spacecraft, such as ACE, STEREO, and Solar Orbiter, where 3He finite mass peak is measured at least on one spacecraft. This presentation discusses the origin of vastly different abundances and spectral shapes in terms of variable remnant population from preceding impulsive SEP events. Furthermore, with the help of imaging observations from SDO and STEREO, we examine a possible direct contribution from parent active regions of GSEP events.

How to cite: Bucik, R., Mason, G. M., Gómez-Herrero, R., Dayeh, M. A., Desai, M. I., Hart, S. T., Ho, G. C., Lario, D., Krupar, V., Wimmer-Schweingruber, R. F., Rodríguez-Pacheco, J., and Asfaw, T. T.: Multi-Spacecraft Observations of Gradual Solar Energetic Particle Events with Enhanced 3He Abundance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6726, https://doi.org/10.5194/egusphere-egu22-6726, 2022.

EGU22-6802 | Presentations | ST1.8 | Highlight

Interstellar Probe: A Mission to the Heliospheric Boundary and Interstellar Medium to Understand our Home in the Galaxy 

Pontus Brandt and the The Interstellar Probe Study Team

For the past 60, 000 years our Sun and its protective heliosphere have been plowing through the Local Interstellar Cloud (LIC), but is now in a historic transition region towards the G-cloud that could have dramatic consequences for the global heliospheric structure. An Interstellar Probe mission to the Very Local Interstellar Medium (VLISM) would bring new scientific discoveries of the mechanisms upholding our vast heliosphere and directly sample the Local Interstellar Clouds to allow us, not only to understand the current dynamics and shielding, but also how the heliosphere responded in the past and how it will respond in the new interstellar environment. An international team of scientists and experts have now completed a NASA-funded study led by The Johns Hopkins University Applied Physics Laboratory (APL) to develop pragmatic example mission concepts for an Interstellar Probe with a nominal design lifetime of 50 years. The team has analyzed dozens of launch configurations and demonstrated that asymptotic speeds in excess of 7.5 Astronomical Units (AU) per year can be achieved using existing or near-term propulsion stages with a powered or passive Jupiter Gravity Assist (JGA). These speeds are more than twice that of the fastest escaping man-made spacecraft to date, which is Voyager 1 currently at 3.59 AU/year. An Interstellar Probe would therefore reach the Termination Shock (TS) in less than 12 years and cross the Heliopause into the VLISM after about 16 years from launch.

In this presentation we provide an overview of the study, the science mission concept, discuss the compelling discoveries that await, and the associated example science payload, measurements and operations ensuring a historic data return that would push the boundaries of space exploration by going where no one has gone before.

How to cite: Brandt, P. and the The Interstellar Probe Study Team: Interstellar Probe: A Mission to the Heliospheric Boundary and Interstellar Medium to Understand our Home in the Galaxy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6802, https://doi.org/10.5194/egusphere-egu22-6802, 2022.

EGU22-7831 | Presentations | ST1.8

Langmuir waves associated with magnetic holes in the solar wind 

Joan Jordi Boldu-O´Farrill Treviño, Daniel Graham, Michiko Morooka, Tomas Karlsson, Yuri Khotyaintsev, Mats André, Jan Souček, and Milan Maksimovic

Langmuir waves (electrostatic waves near the electron plasma frequency) are often observed in the solar wind, playing an important role in the energy dissipation of electrons. The largest amplitude waves are typically associated with type II and III solar radio bursts and planetary foreshocks. However, Langmuir waves not connected with radio bursts are also found in the solar wind. The causes of these Langmuir waves are not well understood. Langmuir waves are also found around magnetic holes, a localised depression of the magnetic field strength. This study aims to investigate the relationship between Langmuir waves and magnetic holes in the solar wind using electric and magnetic field measurements performed by the Solar Orbiter’s RPW and MAG instruments during 2020 and 2021. We identified a large set of Langmuir wave events from the RPW/TDS (Time Domain Sampler) waveform data using the plasma density estimated from the spacecraft’s potential obtained by RPW, showing that ~7% of them have been spotted inside magnetic holes. We will compare these events with local plasma conditions analysing the electron distribution functions, and discuss the mechanisms that may lead to the generation of Langmuir waves associated with magnetic holes in the solar wind.

How to cite: Boldu-O´Farrill Treviño, J. J., Graham, D., Morooka, M., Karlsson, T., Khotyaintsev, Y., André, M., Souček, J., and Maksimovic, M.: Langmuir waves associated with magnetic holes in the solar wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7831, https://doi.org/10.5194/egusphere-egu22-7831, 2022.

EGU22-7840 | Presentations | ST1.8

The exoplanetary magnetosphere extension in Sun-like stars based on the solar wind and solar UV emission 

Raffaele Reda, Luca Giovannelli, Tommaso Alberti, Francesco Berrilli, Luca Bertello, Dario Del Moro, Maria Pia Di Mauro, Piermarco Giobbi, and Valentina Penza

The solar activity in form of coronal mass ejections or solar wind disturbances, such as slow or high speed streams, affects the circumterrestrial electromagnetic environment, with a primary effect on the magnetosphere, compressing and perturbing it. Here, in order to connect the long-term solar activity variations to solar wind properties, we use measurement of a proxy for chromospheric activity, the Ca II K index, and solar wind OMNI data for the time interval 1965-2021, which almost entirely covers the last 5 solar cycles. By using both a cross correlation and a mutual information approach, a 3.6-year mean lag has been found between Ca II K index and solar wind dynamic pressure. This result allows us to obtain a relationship between the solar UV emission and the solar wind dynamic pressure, enabling us to derive the Earth’s magnetospheric extension over the last 5 solar cycles.
Moreover, the advantage of having used the Ca II K index proxy is that the relation found for the Sun can be easily extended to other stars with similar properties (i.e. Sun-like stars). To this scope, the model is then used to study the effect of stellar wind dynamic pressure on the magnetosphere of Earth-like planets orbiting at 1 AU around a sample of Sun-like stars.

How to cite: Reda, R., Giovannelli, L., Alberti, T., Berrilli, F., Bertello, L., Del Moro, D., Di Mauro, M. P., Giobbi, P., and Penza, V.: The exoplanetary magnetosphere extension in Sun-like stars based on the solar wind and solar UV emission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7840, https://doi.org/10.5194/egusphere-egu22-7840, 2022.

EGU22-8435 | Presentations | ST1.8

Studies on Space Climate Made in the University of Extremadura (Spain) 

Víctor M.S. Carrasco, Alejandro J.P. Aparicio, José M. Nogales, Nieves Bravo-Paredes, Irene Tovar, Maricruz Gallego, and José M. Vaquero

Our research group has carried out several studies on space climate in the past. One of our lines of work is the recovery and analysis of the catalogues including historical sunspot observations. We have already published in digital version some sunspot catalogues made in observatories, for example, of the Iberian Peninsula (Aparicio et al. 2018). Recently, we have also digitized the catalogue from the sunspot observations made in the Stonyhurst College Observatory for 1921 – 1935 (Carrasco et al. 2021) and completed the first step for the publication of the Sacramento Peak Observatory sunspot catalogue (1947 – 2004) (Carrasco et al. 2020). Currently, we are analyzing the sunspot observations from drawings made in Boulder (U.S.A) for the period 1966 – 1992 to create a sunspot group catalogue including that information. Furthermore, we have also analyzed long-term observation series made by individual astronomers. Two examples of this kind of studies can be the analysis of the sunspot observations made by David Hadden during the period 1890 – 1931 (Carrasco et al. 2013) and those made by Eric Strach for 1969 – 2008 (Carrasco et al. 2019). Nowadays, in collaboration with other Italian research group, we are studying all the sunspot drawings made by Father Angelo Secchi in the second half of the 19th century. We are constructing the Wolf number, group number and the area series from these drawings. As future work, our objective is to publish a sunspot group catalogue from these observations.

References

Aparicio, A.J.P., Lefèvre, L., Gallego, M.C., Vaquero, J.M., Clette, F., Bravo-Paredes, N., Galaviz, P., Bautista, M.L.: 2018, A Sunspot Catalog for the Period 1952 – 1986 from Observations Made at the Madrid Astronomical Observatory, Solar Physics 293, 164.

Carrasco, V.M.S., Vaquero, J.M., Gallego, M.C., Trigo, R.M.: 2013, Forty two years counting spots: Solar observations by D.E. Hadden during 1890–1931 revisited. New Astronomy 25, 95.

Carrasco, V.M.S, Vaquero, J.M., Olmo-Mateos, V.M.: 2019, Eric Strach: Four Decades of Detailed Synoptic Solar Observations (1969‐2008), Space Weather 17, 796.

Carrasco, V.M.S., Pevtsov, A.A., Nogales, J.M., Vaquero, J.M.: 2020, The Sunspot Drawing Collection of the National Solar Observatory at Sacramento Peak (1947–2004), Solar Physics 296, 3.

Carrasco, V.M.S., Muñoz-Jaramillo, A., Nogales, J.M., Gallego, M.C., Vaquero, J.M.: 2021, Sunspot Catalog (1921–1935) and Area Series (1886–1940) from the Stonyhurst College Observatory, Astrophysical Journal Supplement Series 256, 38.

How to cite: Carrasco, V. M. S., Aparicio, A. J. P., Nogales, J. M., Bravo-Paredes, N., Tovar, I., Gallego, M., and Vaquero, J. M.: Studies on Space Climate Made in the University of Extremadura (Spain), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8435, https://doi.org/10.5194/egusphere-egu22-8435, 2022.

With current observational methods it is not possible to determine the magnetic field in the solar corona accurately. Therefore, coronal magnetic field models have to rely on extrapolation methods using photospheric magnetograms as boundary conditions. In recent years, due to the increased resolution of observations and the need to resolve non-force-free lower regions of the solar atmosphere, there have been increased efforts to use magnetohydrostatic (MHS) field models instead of force-free extrapolation methods. Although numerical methods to calculate MHS solutions can deal with non-linear problems and hence provide more accurate models, analytical three-dimensional MHS equilibria can also be used as a numerically relatively “cheap” complementary method.

 

We discuss a family of analytical MHS equilibria that allows for a transition from a non-force-free region to a force-free region. The solution involves hypergeometric functions and while routines for the calculation of these are available, this can affect both the speed and the numerical accuracy of the calculations. We therefore look into the asymptotic behaviour of this solution in order to numerically approximate it through exponential functions aiming to improve the numerical efficiency. We present an illustrative example by comparing field line profiles, density and pressure differences between the exact solutions, the asymptotic solution and a hybrid model where the use of the hypergeometric function is restricted to an area around the transitional region between the non-force-free and the force-free domain.

How to cite: Nadol, L. and Neukirch, T.: Coronal Magnetic Field Extrapolation Using a Specific Family of Analytical 3D Magnetohydrostatic Equilibria — Practical Aspects, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9430, https://doi.org/10.5194/egusphere-egu22-9430, 2022.

EGU22-9622 | Presentations | ST1.8

Clarifying the relation between chromospheric emissions and photospheric magnetic fields using AIA 1600 Å and HMI data 

Ismo Tähtinen, Ilpo Virtanen, Alexei Pevtsov, and Kalevi Mursula

Intense photospheric magnetic fields manifest as enhanced emission in several spectral lines and parts of the continuum. Here we aim to improve the understanding of the relation between magnetic fields and radiative structures by using the seeing-free observations of the Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic Imager (HMI), both on-board Solar Dynamics Observatory (SDO). We use AIA 1600 Å band, which captures the far-ultraviolet continuum emission originating from the temperature minimum of the solar chromosphere.

We developed a novel, objective method to define thresholds separating the brightest AIA 1600 Å pixels ("bright pixels") and the least bright pixels ("dark pixels") from the AIA 1600 Å brightness distribution. According to the method bright pixels are pixels whose standardized contrast (ratio of brightness to the center-to-limb variation) exceeds the level of I = 1.93. This threshold maximizes the average size of bright clusters (4-connected regions of bright pixels). Dark pixels are pixels whose standardized contrast is below I = 0.5. This corresponds to a threshold below which there are practically no pixels on quiet days. Comparing the AIA 1600 Å intensity and HMI magnetic field observations, we found that the AIA 1600 Å dark pixels correspond to the strongest magnetic field (B > 1325 G) pixels. These pixels are typically within sunspots. On the other hand, we found the AIA bright pixels correspond to moderate (55 G < B < 475 G) magnetic field intensity pixels of HMI.

We found that the percentage of AIA bright pixels on the solar surface almost entirely explains the observed variability of the total AIA 1600 Å emission, even in the presence of large sunspot groups. We developed a multi-linear regression model, which reliably predicts the magnitude of the disk-averaged unsigned magnetic field using the measured percentages of bright and dark pixels. We found that the large bright clusters have a constant mean unsigned magnetic field, similarly as earlier found for, e.g., Ca II K plages. However, the magnetic field strength of bright clusters is 246.5 ± 0.1 G, which is roughly 100 G larger than found earlier for Ca II K plages.

How to cite: Tähtinen, I., Virtanen, I., Pevtsov, A., and Mursula, K.: Clarifying the relation between chromospheric emissions and photospheric magnetic fields using AIA 1600 Å and HMI data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9622, https://doi.org/10.5194/egusphere-egu22-9622, 2022.

EGU22-10969 | Presentations | ST1.8

Evolution and variation of the heliospheric current sheet during 1995-2009 

Kan Liou and Chin-Chun Wu

The heliospheric current sheet (HCS) is the largest known solar wind structure that exists persistently and continuously within the heliosphere. While it is discovered for more than half a century ago, owing to very limited and scattered in-situ solar wind observations in the heliosphere, the shape and evolution of the HCS are still little known and constitute the key subject in the study of global-scale solar wind. Currently the morphology of the HCS is derived largely from simple kinematic approaches that map the neutral sheet observed at 2.5 solar radii outward into the heliosphere. The dynamical effect of solar wind interactions on the evolution and global structure of the HCS is still poorly understood. Here we present results from a study of the HCS from 1995 to 2009 using time-dependent, three-dimensional, global magnetohydrodynamic (MHD) model simulations. We focus on the radial and solar cycle variations of the HCS tilt angle from 18 solar radii to 7 AU. We also compare our result with those obtained from ballistic outward projections of the neutral sheet observed at 2.5 solar radii. We present our analysis result and discuss possible implications.

How to cite: Liou, K. and Wu, C.-C.: Evolution and variation of the heliospheric current sheet during 1995-2009, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10969, https://doi.org/10.5194/egusphere-egu22-10969, 2022.

EGU22-11163 | Presentations | ST1.8

Deriving proper electron characteristics in the solar wind from Solar Orbiter observations 

Štěpán Štverák, Georgios Nicolaou, Christopher J. Owen, Milan Maksimovic, and Pavel M. Trávníček

Solar Orbiter, the latest ESA solar and heliospheric space mission, provides the most recent plasma measurements in the free streaming solar wind across a wide range of the radial distance from the Sun. Electron observations are enabled by the Electron Analyser System (EAS) being part of the Solar Wind Analyser (SWA) suit of instruments. Electron properties are measured in a form of velocity distribution functions (VDFs) with an unprecedent sampling rate of 10 s in the normal operational mode going down to even 8 Hz for limited burst mode snapshots. Regular EAS observations started in mid of 2020 and all data are being continuously made publicly available throughout the ESA's Solar Orbiter Archive (SOAR). Here we present some preliminary user-based methods and techniques of deriving proper electron characteristics from the Level 2 calibrated data set by calculating the required moments of measured VDFs. In particular, we focus on data correction with respect to possible instrument and/or spacecraft related effects. The obtained results are compared and validated by a cross calibration with respect to electron properties derived from the quasi-thermal noise measurements provided by the Radio and Plasma Waves (RPW) instrument, being also part of the in situ plasma payload of the Solar Orbiter mission.

How to cite: Štverák, Š., Nicolaou, G., Owen, C. J., Maksimovic, M., and Trávníček, P. M.: Deriving proper electron characteristics in the solar wind from Solar Orbiter observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11163, https://doi.org/10.5194/egusphere-egu22-11163, 2022.

EGU22-11326 | Presentations | ST1.8

Dynamics of helium abundance inside and around ICME 

Alexander Khokhlachev, Yuri Yermolaev, Maria Riazantseva, Liudmila Rakhmanova, and Irina Lodkina

The interplanetary manifestations of coronal mass ejections (ICME) typically characterized by an increased relative abundance of doubly ionized helium, which can be several time higher comparative to the slow solar wind streams and exceed 10%. At the same time the helium abundance can dynamically change as a result of local processes in solar wind plasma. However, the details of helium abundance dynamic have not yet been sufficiently studied.

The study is devoted to the changing of the helium abundance inside the ICME including both its types - Magnetic Clouds (MC) and EJECTA, and also in the vicinity of these large scale structures. We consider the helium abundance dynamic, and its relation with other solar wind parameters both at large (>106 km) and medium (104-105 km) scales, based on the statistic and correlation analysis of plasma and magnetic field parameters [Yermolaev et al., 2020; Khokhlachev et al., 2021]. Hourly average data from OMNI-2 database and 3 second WIND spacecraft measurements are used for the analysis of corresponding scales. Selection of the intervals related to ICME events (MC, EJECTA and SHEATH regions) was produced with the help of the catalog of large-scale events of Space Research Institute (http://iki.rssi.ru/pub/omni/catalog/ [Yermolaev et al., 2009]). It is shown that on large scales the helium abundance generally increases with a decrease in the plasma parameter β in the ICME. This relation can be predominantly explained by the strong positive correlation of helium abundance with magnetic pressure, while correlation with thermal pressure is ambiguous: weak negative for Magnetic Clouds and weak positive for EJECTA. This confirms the previously proposed hypothesis of the ion current flow enriched by helium ions inside the ICME [Yermolaev et al., 2020]. On medium scales, the trend of anticorrelation of the helium abundance with plasma β-parameter in the ICME is observed also. However, the dependences of the helium abundance on the plasma and magnetic field parameters can dynamically change at smaller scales. For example, several local medium-scale structures with a negative correlation of helium abundance and magnetic field magnitude can be observed on the background of positive correlation at large-scale structures.

References.

Yermolaev Y.I. et al., Catalog of large-scale solar wind phenomena during 1976–2000, Cosmic Res., 2009, vol. 47, no. 2, pp. 81–94

Yermolaev Y.I. et al., Dynamics of large-scale solar-wind streams obtained by the double superposed epoch analysis. 4. Helium abundance, Journal of Geophysical Research, 2020, 125 (7) https://doi.org/10.1029/2020JA027878

Khokhlachev A. A. et al., Variations of Protons and Doubly Ionized Helium Ions in the Solar Wind, Cosmic Research, 2021, vol. 59, no. 6, pp. 415-426
https://doi.org/10.1134/S0010952521060022

How to cite: Khokhlachev, A., Yermolaev, Y., Riazantseva, M., Rakhmanova, L., and Lodkina, I.: Dynamics of helium abundance inside and around ICME, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11326, https://doi.org/10.5194/egusphere-egu22-11326, 2022.

EGU22-11910 | Presentations | ST1.8

Radial evolution of the key solar wind parameters according to the Parker Solar Probe and other missions 

Uliana Antsiferova and Olga Khabarova

Knowing the temporal and spatial behavior of the main plasma parameters in the solar wind is important because of both an academic interest and the necessity to build theoretical models. Meanwhile, the solar wind characteristics are available with good accuracy only from in situspacecraft observations. There are a very limited number of studies that analyzed the radial evolution of the interplanetary magnetic field, the speed, the density, and the temperature of the solar wind. Previously, data from missions carried out in the 1970s were used for these purposes. Meanwhile, none of them approached the Sun closer than ~0.3 AU, and the information available did not allow describing the processes occurring near the solar corona. The launch of the Parker Solar Probe mission has opened up vast opportunities for studying the solar wind, starting from distances of the order of the Alfven radius. At the moment, Parker Solar Probe data are available with approaches to the Sun up to 0.08 AU.

An analysis of data obtained from Parker Solar Probe and Helios 2 (up to 1 AU), and from IMP8 and Voyager 1 (further from the Earth's orbit and up to 7 AU) was performed. The dependencies of the interplanetary magnetic field, the temperature, the speed, and the density of the solar wind on heliocentric distance are revealed and their typical profiles are analyzed. The nature of deviations of observed values from theoretical expectations is discussed. A particular attention is paid to the comparison of the results from the Parker Solar Probe and Helios missions.

How to cite: Antsiferova, U. and Khabarova, O.: Radial evolution of the key solar wind parameters according to the Parker Solar Probe and other missions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11910, https://doi.org/10.5194/egusphere-egu22-11910, 2022.

EGU22-11979 | Presentations | ST1.8

Morphology of magnetic holes in the pristine solar wind 

Henriette Trollvik, Tomas Karlsson, and Savvas Raptis

Magnetic holes (MHs) are deep depressions in the magnetic field found in the solar wind and in planetary magnetosheaths. Based on Cluster multi-point data from the pristine solar wind, we investigate the morphology of MHs exhibiting no to little rotation in the magnetic field(linear MHs). In a previous study we used timing methods to determine that the MHs were moving with the solar wind, and from that we are now able to determine the spatial scales. We investigate the morphology by comparing observations to theoretical models, starting with infinitely long solenoid model. The scale sizes are related to the orientation parallel and perpendicular to the magnetic field. Here we present the preliminary results, showing a few examples, which later will be expanded to a statistical study.

How to cite: Trollvik, H., Karlsson, T., and Raptis, S.: Morphology of magnetic holes in the pristine solar wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11979, https://doi.org/10.5194/egusphere-egu22-11979, 2022.

EGU22-12590 | Presentations | ST1.8

How to identify important magnetic helicity locations in solar active regions 

Kostas Moraitis, Spiros Patsourakos, and Alexander Nindos

Magnetic helicity is a physical quantity of great importance in the study of magnetized plasmas as it is conserved in ideal magneto-hydrodynamics and slowly deteriorating in non-ideal conditions such as magnetic reconnection. A meaningful way of defining a density for helicity is with field line helicity, which, in solar conditions, is expressed by relative field line helicity (RFLH). Here, we study in detail the behaviour of RFLH in the large, well-studied, eruptive solar active region (AR) 11158. The computation of RFLH and of all other quantities of interest is based on a high-quality non-linear force-free reconstruction of the AR coronal magnetic field, and on the recent developments in its computational methodology. The derived photospheric morphology of RFLH is very different than that of the magnetic field or the electrical current, and also manages to depict the large decrease in the value of helicity during an X-class flare of the AR. Moreover, the area of the RFLH decrease coincides with the location of the magnetic structure that later erupted, the flux rope. Based on these results we review the necessary steps one needs to follow in order to identify the locations in an AR where magnetic helicity is more important. This task can provide crucial information for the conditions of an AR, especially during eruptive events.

How to cite: Moraitis, K., Patsourakos, S., and Nindos, A.: How to identify important magnetic helicity locations in solar active regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12590, https://doi.org/10.5194/egusphere-egu22-12590, 2022.

EGU22-13141 | Presentations | ST1.8

MHD avalanches in truly curved coronal arcades: proliferation and heating 

Jack Reid, James Threlfall, and Alan W. Hood

MHD avalanches involve small, narrowly localized instabilities spreading across neighbouring areas in a magnetic field. Cumulatively, many small events release vast amounts of stored energy. Straight cylindrical flux tubes are easily modelled, between two parallel planes, and can support such an avalanche: one unstable flux tube causes instability to proliferate, via magnetic reconnection, and then an ongoing chain of like events. True coronal loops, however, are visibly curved, between footpoints on the same solar surface. With 3D MHD simulations, we verify the viability of MHD avalanches in a more physical, curved geometry, in a coronal arcade. MHD avalanches thus amplify instability across strong astrophysical magnetic fields and disturb wide regions of plasma. Contrasting with the behaviour of straight cylindrical models, a modified ideal MHD kink mode occurs, more readily and preferentially upwards. Instability spreads over a region far wider than the original flux tubes and their footpoints. Consequently, sustained heating is produced in a series of 'nanoflares', collectively contributing substantially to coronal heating. Overwhelmingly, viscous heating dominates, generated in shocks and jets produced by individual small events. Reconnection is not the greatest contributor to heating, but rather facilitates those processes that are. Localized and impulsive, heating shows no strong spatial preference, except a modest bias away from footpoints, towards the loop's apex.

How to cite: Reid, J., Threlfall, J., and Hood, A. W.: MHD avalanches in truly curved coronal arcades: proliferation and heating, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13141, https://doi.org/10.5194/egusphere-egu22-13141, 2022.

Two-dimensional Particle-In-Cell simulations are performed to study the electromagnetic radiation emitted at fundamental and harmonic plasma frequencies by a weak electron beam propagating in a background plasma with random density fluctuations, in solar wind conditions relevant to Type III solar radio bursts. The simulations use a panel of physical and numerical parameters that were not reached in previous works and involve self-consistently varying random plasma density fluctuations in an exceptionally large and well resolved simulation box. The dynamics of the waves, the beam and the inhomogeneous plasma are calculated over several thousands of plasma periods. For relevant comparisons, simulations with and without applied density fluctuations are performed for the same parameters. For the first time, the essential impact of density fluctuations of average levels of a few percent of the background plasma on the physical mechanisms driving the generation of electromagnetic waves is shown. Not only wave nonlinear interactions contribute to the generation of such emissions, but also processes of Langmuir waves' transformations on the density fluctuations.

How to cite: Krafft, C. and Savoni, P.: Electromagnetic radiation emitted at fundamental and harmonic plasma frequencies by weak electron beams in inhomogeneous solar wind plasmas : 2D PIC simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13146, https://doi.org/10.5194/egusphere-egu22-13146, 2022.

EGU22-1155 | Presentations | ST1.9

Energy transfer, discontinuities and heating in the inner solar wind measured with a weak and local formulation of the Politano-Pouquet law 

Vincent David, Sébastien Galtier, Fouad Sahraoui, and Lina Hadid

The solar wind is a highly turbulent plasma for which the mean rate of energy transfer ε has been measured for a long time using the Politano-Pouquet (PP98) exact law. However, this law assumes statistical homogeneity that can be violated by the presence of discontinuities. Here, we introduce a new method based on the inertial dissipation DI whose analytical form is derived from incompressible magnetohydrodynamics (MHD); it can be considered as a weak and local (in space) formulation of the PP98 law whose expression is recovered after integration is space. We used DI to estimate the local energy transfer rate from the THEMIS-B and Parker Solar Probe (PSP) data taken in the solar wind at different heliospheric distances. Our study reveals that discontinuities near the Sun lead to a strong energy transfer that affects a wide range of scales σ. We also observe that switchbacks seem to be characterized by a singular behavior with an energy transfer varying as σ−3/4, which slightly differs from classical discontinuities characterized by a σ−1 scaling. A comparison between the measurements of ε and DI shows that in general the latter is significantly larger than the former.

https://arxiv.org/pdf/2201.02377.pdf

How to cite: David, V., Galtier, S., Sahraoui, F., and Hadid, L.: Energy transfer, discontinuities and heating in the inner solar wind measured with a weak and local formulation of the Politano-Pouquet law, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1155, https://doi.org/10.5194/egusphere-egu22-1155, 2022.

EGU22-1298 | Presentations | ST1.9

Can instabilities work in a turbulent plasma and if so, what conditions are needed for instabilities to act? 

Simon Opie, Daniel Verscharen, Chris Chen, and Christopher Owen

The solar wind is a continuous outflow of plasma from the Sun, which expands into the space between the planets in our solar system and forms the heliosphere. The solar wind is inherently turbulent and characterised by kinetic micro-instabilities on a range of scales.  Large-scale compressions (ubiquitous in solar-wind turbulence) create conditions for proton, alpha-particle and electron micro-instabilities, which transfer energy to small-scale fluctuations. These instabilities are driven by various sources of free energy (e.g. particle beams, differential flows, heat fluxes, temperature anisotropies) and make a significant contribution to the fluctuation spectrum at kinetic scales, where energy dissipation occurs. This presentation investigates the occurrence and the behaviour of kinetic instabilities in turbulent space plasmas with particular emphasis on the conditions necessary for instabilities to act.

We consider instabilities driven by proton temperature anisotropy in the turbulent solar wind by using statistical methods to analyse the Solar Orbiter data and characterise the turbulence at the relevant scales and amplitude. We compare theoretical calculations with the high-resolution data available from the Solar Orbiter MAG and SWA instruments. From this analysis we infer conditions that are necessary for instabilities to act in a turbulent plasma and demonstrate how these conditions relate to the assumptions that underpin theoretical analyses at kinetic scales. We will also introduce the next steps in this research, including the modelling and quantification of energy transfer processes at kinetic scales with particular reference to scaling law behaviours in the turbulent solar wind.   

 

How to cite: Opie, S., Verscharen, D., Chen, C., and Owen, C.: Can instabilities work in a turbulent plasma and if so, what conditions are needed for instabilities to act?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1298, https://doi.org/10.5194/egusphere-egu22-1298, 2022.

EGU22-1369 | Presentations | ST1.9

An examination of the magnetic fluctuations in long-lasting radial IMF events 

Gilbert Pi, Alexander Pitna, Zdenek Nemecek, and Jana Safrankova

This study investigates long-lasting radial interplanetary magnetic field (IMF) intervals in which IMF points along the solar wind flow direction for several hours. We use 419 such events identified in Wind observations during 1995-2019, and we focus on the behavior of magnetic field fluctuations. Using the power spectral density (PSD) calculated over 1-hour radial IMF intervals and PSDs in adjacent regions prior to and after the radial IMF interval, we address: (i) the power of IMF fluctuations, (ii) median slopes of PSDs in both inertial and kinetic ranges, (iii) the proton temperature and its anisotropy, and (vi) the occurrence rate of wavy structures and their polarization. Comparison of PSDs in radial IMF intervals with those in prior and after them revealed that the fluctuation magnitude is low in the radial IMF intervals in both MHD and kinetic ranges and the spectral power increases with the cone angle in the MHD range. It may be related to the observation limitations because the dominant 2D component of the magnetic fluctuation is hard to observe if the sampling direction is aligned with the mean magnetic field. Moreover, the proton temperature is more isotropic, and the occurrence rate of wave structures is higher for radial IMF events. The waves have no preferred polarization in the frequency range from 0.1 to 1 Hz. It suggests that the radial IMF structure leads to a different development of turbulence than the typical Parker-spiral orientation.

How to cite: Pi, G., Pitna, A., Nemecek, Z., and Safrankova, J.: An examination of the magnetic fluctuations in long-lasting radial IMF events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1369, https://doi.org/10.5194/egusphere-egu22-1369, 2022.

EGU22-3967 | Presentations | ST1.9

Electric Field Turbulence in the Solar Wind from MHD down to Electron Scales: Artemis Observations 

Chadi Salem, John Bonnell, Jordan Huang, Christopher Chaston, Luca Franci, Kristopher Klein, and Daniel Verscharen

Recent observational and theoretical work on solar wind turbulence and dissipation suggests that kinetic-scale fluctuations are both heating and isotropizing the solar wind during transit to 1 AU.  The nature of these fluctuations and associated heating processes are poorly understood. Whatever the dissipative process that links the fields and particles - Landau damping, cyclotron damping, stochastic heating, or energization through coherent structures - heating and acceleration of ions and electrons occurs because of electric field fluctuations. The dissipation due to the fluctuations depends intimately upon the temporal and spatial variations of those fluctuations in the plasma frame.  In order to derive that distribution in the plasma frame, one must also use magnetic field and density fluctuations, in addition to electric field fluctuations, as measured in the spacecraft frame (s/c) to help constrain the type of fluctuation and dissipation mechanisms that are at play.

We present here an analysis of electromagnetic fluctuations in the solar wind from MHD scales down to electron scales based on data from the Artemis spacecraft at 1 AU. We focus on a few time intervals of pristine solar wind, covering a reasonable range of solar wind properties (temperature ratios and anisotropies; plasma beta; and solar wind speed). We analyze magnetic, electric field, and density fluctuations from the 0.01 Hz (well in the inertial range) up to 1 kHz. We compute parameters such as the electric to magnetic field ratio, the magnetic compressibility, magnetic helicity, compressibility and other relevant quantities in order to diagnose the nature of the fluctuations at those scales between the ion and electron cyclotron frequencies, extracting information on the dominant modes composing the fluctuations. We also use the linear Vlasov-Maxwell solver, PLUME, to determine the various relevant modes of the plasma with parameters from the observed solar wind intervals. We discuss the results and the relevant modes as well as the major differences between our results in the solar wind and results in the magnetosheath.

How to cite: Salem, C., Bonnell, J., Huang, J., Chaston, C., Franci, L., Klein, K., and Verscharen, D.: Electric Field Turbulence in the Solar Wind from MHD down to Electron Scales: Artemis Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3967, https://doi.org/10.5194/egusphere-egu22-3967, 2022.

In recent years, the Kolmogorov's statistical formalism of exact law that describes incompressible hydrodynamic turbulence, has been extended to compressible magnetized fluid described by isothermal or polytropic closure. Such exact laws permit an evaluation of the energy cascade rate, assumed within this formalism to be equivalent to the dissipation rate. Its estimation in the solar wind can help to better understand particle heating in such collisionless media. But previous exact laws are insufficient in a system led by pressure anisotropy. We propose a general exact law of Hall-MHD turbulence based on models with a pressure tensor that allows us to study various known equations of state as particular limits, derive a new one corresponding to the CGL (i.e., gyrotropic pressure tensor), and correlate the cascade rate to instable plasma conditions. In the incompressible MHD limit we provide a generalization of the Politano & Pouquet law to pressure-anisotropic plasmas.

How to cite: Simon, P. and Sahraoui, F.: A link between turbulent cascade and gyrotropic pressure instabilities in compressible and magnetized fluids., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4524, https://doi.org/10.5194/egusphere-egu22-4524, 2022.

EGU22-5115 | Presentations | ST1.9

Quantification of the cross-helicity cascade with Karman-Howarth-Monin and Spectral transfer equations 

Victor Montagud-Camps, Petr Hellinger, Andrea Verdini, Emanuele Papini, Luca Franci, Lorenzo Matteini, and Simone Landi

Spectral transfer equations allow to  quantify the value of the energy flux of a turbulent flow across concentric shells in Fourier space. Karman-Howarth-Monin equations serve as a complement to the Spectral Transfer analysis, since they  quantify  as well the energy transfer rate of turbulence across scales via third-order structure functions, but also provide information on the directionality of the flux. We have extended the use of these methods to study the cascade of cross-helicity and compare it to the energy cascade  in 3D compressible MHD simulations. Our results show that the cross-helicity cascade reaches stationarity after the energy cascade, thus indicating a slower turbulence development for this invariant. Once fully developed, the cross-helicity cascade matches the main features of the energy one.

How to cite: Montagud-Camps, V., Hellinger, P., Verdini, A., Papini, E., Franci, L., Matteini, L., and Landi, S.: Quantification of the cross-helicity cascade with Karman-Howarth-Monin and Spectral transfer equations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5115, https://doi.org/10.5194/egusphere-egu22-5115, 2022.

EGU22-6199 | Presentations | ST1.9

Magnetic field fluctuations in CME-driven sheath regions 

Emilia Kilpua, Simon Good, Matti Ala-Lahti, Adnane Osmane, Dominique Fontaine, Sanchita Pal, Juska Räsänen, Stuart Bale, Lingling Zhao, Lina Hadid, Miho Janvier, and Emiliya Yordanova

The sheath regions driven by coronal mass ejections (CMEs) are large-scale heliospheric structures where magnetic field fluctuations are observed over various temporal scales. Their internal structure and nature of embedded  fluctuations are currently poorly understood. We report here the key characteristics of  magnetic field fluctuations in CME-driven sheaths, including their spectral index, intermittency, amplitude and compressibility. The results highlight the gradual formation of sheaths over several days as they propagate through interplanetary and the presence of intermittent coherent structures such as strong current sheets. The Jensen-Shannon permutation entropy and complexity analysis suggest that sheath fluctuations are stochastic, but have lower entropy and higher complexity than the preceding wind.  We also show the analysis results during the slow sheath at ~0.5 AU detected by Parker Solar Probe, highlighting that slow CMEs can have prominent sheaths with distinct fluctuation properties. 

How to cite: Kilpua, E., Good, S., Ala-Lahti, M., Osmane, A., Fontaine, D., Pal, S., Räsänen, J., Bale, S., Zhao, L., Hadid, L., Janvier, M., and Yordanova, E.: Magnetic field fluctuations in CME-driven sheath regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6199, https://doi.org/10.5194/egusphere-egu22-6199, 2022.

EGU22-6596 | Presentations | ST1.9

Analysis of Turbulence Energy Transfer at an Interplanetary Shock Observed by MMS 

Nawin Ngampoopun, David Ruffolo, Riddhi Bandyopadhyay, and William Matthaeus

Turbulence near an interplanetary shock is of practical interest because turbulent magnetic fluctuations are key to the diffusive shock acceleration and transport of energetic particles, which can lead to significant space weather effects.  In this work, we examine burst-mode observations by the Magnetospheric Multiscale Mission (MMS) for an interplanetary shock passage at a distance of 25 Re­ on 8 January 2018.  The instrumental resolution offers an opportunity to examine the energy transfer rate of solar wind turbulence in both the upstream and downstream regions. We implement a Hampel filtering-based technique to mitigate the instrumental noise in plasma moment data. We use a Kolmogorov-Yaglom Law for the third-order structure function and a von Kármán-decay law to calculate the energy dissipation rates at the inertial scale and energy-containing scale, respectively. The results show that the region downstream of the shock has stronger and better developed turbulence and a higher energy transfer rate than the upstream region. N.N. has been supported by STFC studentship and UCL Doctoral School. This research has also been supported by grant RTA6280002 from Thailand Science Research and Innovation, by the MMS Theory and Modeling team grant 80NSSC19K0565, and the NASA LWS program grant 80NSSC20K0377 under NMC subcontract 655-001.

How to cite: Ngampoopun, N., Ruffolo, D., Bandyopadhyay, R., and Matthaeus, W.: Analysis of Turbulence Energy Transfer at an Interplanetary Shock Observed by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6596, https://doi.org/10.5194/egusphere-egu22-6596, 2022.

EGU22-7142 | Presentations | ST1.9

Characterization of space-time structures in 3D simulations of plasma turbulence with Fast Iterative Filtering. 

Emanuele Papini, Antonio Cicone, Mirko Piersanti, Luca Franci, Andrea Verdini, Victor Montagud-Camps, Petr Hellinger, and Simone Landi

We present results from a multiscale spatiotemporal analysis of 3D Hall-MHD and hybrid kinetic numerical simulations of decaying plasma turbulence. By combining Fourier analysis and Fast Iterative Filtering, we compute the 3D k-ω power spectrum of the magnetic and velocity fluctuations at the time when turbulence has fully developed. We find that the magnetic fluctuations around and just below the ion characteristic scales mainly consist of strongly anisotropic perturbations, with temporal frequencies smaller than the ion-cyclotron frequency and with wave vectors almost perpendicular to the ambient magnetic field. Further analysis reveals that such perturbations cannot be described in terms of wave-like fluctuations, but rather consist of localized structures that are organized in a filamentary network of current sheets, which continuously form and disrupt as a consequence of magnetic reconnection, spontaneously induced by the interaction of turbulent structures. We discuss similarities and differences with respect to previous findings from 2D simulations, and we put our results in the context of spacecraft observations in the solar wind.

How to cite: Papini, E., Cicone, A., Piersanti, M., Franci, L., Verdini, A., Montagud-Camps, V., Hellinger, P., and Landi, S.: Characterization of space-time structures in 3D simulations of plasma turbulence with Fast Iterative Filtering., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7142, https://doi.org/10.5194/egusphere-egu22-7142, 2022.

EGU22-7265 | Presentations | ST1.9

What is the role of oblique whistler waves in shaping of the solar wind electron function between 0.17 and 1 AU ? 

Lucas Colomban, Matthieu Kretzschmar, Vladimir Krasnoselskikh, Milan Maksimovic, Daniel Graham, Yuri Khotyainsev, Laura Berĉiĉ, Matthieu Berthomier, and Clara Froment

In the solar wind, whistler waves are thought to play an important role on the evolution of the electron velocity distribution function as a function of distance. In particular, oblique whistler waves may diffuse the Strahl electrons into the halo population. Using AC magnetic and electric field measured by the SCM (search coil magnetometer) and electric antenna of Solar Orbiter and Parker Solar Probe, we search for the presence of whistler waves at heliocentric distance between 0.17 and 1 AU. Spectral matrices computation and minimum variance analysis on continuous waveforms make it possible to identify whistler wave modes and to determine their direction of propagation with respect to the ambiant magnetic field (angle and direction : sunward or anti-sunward) . A statistical study of the inclination of these waves and of their parameters is presented and allows us to make assumptions about their roles. Single events are also presented in details

How to cite: Colomban, L., Kretzschmar, M., Krasnoselskikh, V., Maksimovic, M., Graham, D., Khotyainsev, Y., Berĉiĉ, L., Berthomier, M., and Froment, C.: What is the role of oblique whistler waves in shaping of the solar wind electron function between 0.17 and 1 AU ?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7265, https://doi.org/10.5194/egusphere-egu22-7265, 2022.

EGU22-8357 | Presentations | ST1.9

Ion-scale transition of plasma turbulence: Pressure-strain effect 

Petr Hellinger, Victor Montagud-Camps, Luca Franci, Lorenzo Matteini, Emanuele Papini, Andrea Verdini, and Simone Landi

We investigate properties of solar-wind like plasma turbulence using direct numerical simulations. We analyze the transition from large (magnetohydrodynamic) scales to ion ones using two-dimensional hybrid (fluid electrons, kinetic ions) simulations of decaying turbulence. To quantify turbulence properties we apply spectral transfer and Karman-Howarth-Monin equations for extended compressible Hall MHD to the simulated results. The simulation results indicate that the transition from MHD to ion scales (the so called ion break) results from a combination of an onset of Hall physics and of an effective dissipation owing to the pressure-strain energy-exchange channel and resistivity. We discuss the simulation results in the context of the solar wind.

How to cite: Hellinger, P., Montagud-Camps, V., Franci, L., Matteini, L., Papini, E., Verdini, A., and Landi, S.: Ion-scale transition of plasma turbulence: Pressure-strain effect, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8357, https://doi.org/10.5194/egusphere-egu22-8357, 2022.

EGU22-8501 | Presentations | ST1.9

Analysis of Magnetohydrodynamic Perturbations in the Radial-field Solar Wind from Parker Solar Probe Observations 

Siqi Zhao, Huirong Yan, Terry Liu, Mingzhe Liu, and Mijie Shi

We report analysis of sub-Alfvénic magnetohydrodynamic (MHD) perturbations in the low-ß radial-field solar wind employing the Parker Solar Probe spacecraft data from 31 October to 12 November 2018. We calculate wave vectors using the singular value decomposition method and separate MHD perturbations into three eigenmodes (Alfvén, fast, and slow modes) to explore the properties of sub-Alfvénic perturbations and the role of compressible perturbations in solar wind heating. The MHD perturbations show a high degree of Alfvénicity in the radial-field solar wind, with the energy fraction of Alfvén modes dominating (~45%-83%) over those of fast modes (~16%-43%) and slow modes (~1%-19%). We present a detailed analysis of a representative event on 10 November 2018. Observations show that fast modes dominate magnetic compressibility, whereas slow modes dominate density compressibility. The energy damping rate of compressible modes is comparable to the heating rate, suggesting the collisionless damping of compressible modes could be significant for solar wind heating. These results are valuable for further studies of the imbalanced turbulence near the Sun and possible heating effects of compressible modes at MHD scales in low-ß plasma.

How to cite: Zhao, S., Yan, H., Liu, T., Liu, M., and Shi, M.: Analysis of Magnetohydrodynamic Perturbations in the Radial-field Solar Wind from Parker Solar Probe Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8501, https://doi.org/10.5194/egusphere-egu22-8501, 2022.

EGU22-9796 | Presentations | ST1.9

PSP observations of the solar wind coherent structures from MHD to sub-ion scales at 0.17 AU 

Alexander Vinogradov, Olga Alexandrova, Milan Maksimovich, Anton Artemyev, Andre Mangeney, Alexei Vasiliev, Karine Issautier, Michel Moncuquet, and Anatoly Petrukovich

First perihelion Parker Solar Probe magnetic field measurements (MAG and SCM merged data) allow to resolve the fluctuations on a wide range of scales: from MHD to ion plasma scales and smaller. We trace the cascade of the fluctuations and investigate the structures formed. Using the total energy of magnetic fluctuations in time and scales, we show that coherent structures cover all the observed scales. The filling factor of the structures is a few percents. We analyze the magnetic fluctuations at different frequency ranges. We observe the coexistence of events at MHD, ion and sub-ion scales in the form of sharp discontinuities and/or vortex-like events. The approach of selecting structures by total energy alone is not complete, as it can miss structures with change in magnetic field modulus. For completeness, we perform the same analysis on longitudinal magnetic fluctuations.

How to cite: Vinogradov, A., Alexandrova, O., Maksimovich, M., Artemyev, A., Mangeney, A., Vasiliev, A., Issautier, K., Moncuquet, M., and Petrukovich, A.: PSP observations of the solar wind coherent structures from MHD to sub-ion scales at 0.17 AU, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9796, https://doi.org/10.5194/egusphere-egu22-9796, 2022.

EGU22-10131 | Presentations | ST1.9

Turbulence anisotropy observed by Parker Solar Probe 

Lingling Zhao, Gary Zank, Laxman Adhikari, Masaru Nakanotani, Daniele Telloni, Qiang Hu, and Jiansen He

Parker Solar Probe provides a unique opportunity to study anisotropic turbulence in the inner heliosphere. We summarize our recent investigations of solar wind turbulence observed by Parker Solar Probe during its first seven orbits ranging from 0.1 to 0.6 AU. First, we analyzed turbulence anisotropy based on the 2D + slab model and determined the power ratio between the 2D and slab components. We find that the fraction of the 2D component increases with radial distance. Second, we developed a method to identify small-scale magnetic flux ropes and Alfvenic structures based on the reduced magnetic helicity. Alfvenic structures are prevalent in both slow and fast solar wind in PSP's measurements, while the small flux ropes are quasi-2D structures and are relatively abundant near the heliospheric current sheet and slow solar wind. Finally, we analyzed intervals with solar wind velocity strictly parallel to the mean magnetic field. We find a Kolmogorov-like power spectrum with a power-law index of -5/3. Wave activities in both MHD and kinetic scales are also analyzed in these field-aligned intervals. Fast magnetosonic waves and ion-scale waves are identified.

How to cite: Zhao, L., Zank, G., Adhikari, L., Nakanotani, M., Telloni, D., Hu, Q., and He, J.: Turbulence anisotropy observed by Parker Solar Probe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10131, https://doi.org/10.5194/egusphere-egu22-10131, 2022.

EGU22-10948 | Presentations | ST1.9

On the scaling features of magnetic field fluctuations at sub-protonic scales 

Giuseppe Consolini, Simone Benella, Tommaso Alberti, and Mirko Stumpo

Fluctuations of magnetic field in space plasmas at sub-protonic scales have been supposed to be the result of a turbulence process involving different wave modes (EMHD, KAW, …). However, the observed spectral and scaling features seem to be non-universal. Furthermore, there is a wide evidence for the occurrence of a global scale invariance. Now, the complex nature of the fluctuations at these scales could be due to the interweaving of fluid and kinetic processes that might alter the usual scenario expected for the occurrence of strong turbulence. Here, using high-resolution data from the Parker’ Solar Probe mission we attempt an analysis of the scaling features of magnetic field fluctuations at sub-protonic scales using different approaches: i) the structure function analysis, ii) the singularity spectrum analysis and the rank-ordered multifractal analysis. The aim of these multiple approaches is to unveil the inherent complexity of fluctuation field at sub-protonic scale and to understand the controversial issues related to the occurrence of intermittency at these scales.

We acknowledge financial support by Italian MIUR-PRIN grant 2017APKP7T on Circumterrestrial Environment: Impact of Sun-Earth Interaction.

How to cite: Consolini, G., Benella, S., Alberti, T., and Stumpo, M.: On the scaling features of magnetic field fluctuations at sub-protonic scales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10948, https://doi.org/10.5194/egusphere-egu22-10948, 2022.

EGU22-11274 | Presentations | ST1.9

Cross helicity of interplanetary coronal mass ejections 

Simon Good, Lauri Hatakka, Matti Ala-Lahti, Juska Soljento, Adnane Osmane, and Emilia Kilpua

Like the solar wind in general, interplanetary coronal mass ejections (ICMEs) display magnetic field and velocity fluctuations across a wide range of scales. These fluctuations may be interpreted as Alfvénic wave packets propagating parallel or anti-parallel to the local magnetic field direction, with cross helicity, σc, quantifying the difference in power between the counter-propagating fluxes. We have determined σc at inertial range frequencies in a large sample of ICME flux ropes and sheaths observed by the Wind spacecraft at 1 au. The mean σc value was low for both the flux ropes and sheaths, with the balance tipped towards the positive, anti-sunward direction. The low values indicate that Alfvénic fluxes are more balanced in ICMEs than in the solar wind at 1 au, where σc tends to be larger and anti-sunward fluctuations show a greater predominance. Superposed epoch profiles show σc falling sharply in the upstream sheath and being typically close to balance inside the flux rope near the leading edge. More imbalanced, solar wind-like σc values are found towards the trailing edge and further from the rope axis. The presence or absence of an upstream shock also has a significant effect on σc. Coronal and interplanetary origins of low σc in ICMEs are discussed.

How to cite: Good, S., Hatakka, L., Ala-Lahti, M., Soljento, J., Osmane, A., and Kilpua, E.: Cross helicity of interplanetary coronal mass ejections, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11274, https://doi.org/10.5194/egusphere-egu22-11274, 2022.

EGU22-11566 | Presentations | ST1.9

Inverse transfer of magnetic helicity in isothermal supersonic turbulence 

Jean-Mathieu Teissier and Wolf-Christian Müller
The inverse transfer of magnetic helicity is studied through direct numerical simulations of the isothermal magnetohydrodynamics equations. Turbulent systems driven at large scales by either a solenoidal or a compressive forcing are considered, exhibiting root mean square Mach numbers ranging from 0.1 to about 10. The Fourier spectra of magnetic helicity present scaling exponents which become flatter with increasing compressibility. Considering the Alfvén velocity in place of the magnetic field leads however to more invariant spectra. A shell-to-shell transfer analysis reveals the presence of a subdominant direct transfer in the global picture of the inverse transfer, and that the inverse transport entails both local and non-local aspects. These three features (direct transfer, local inverse transfer, non-local inverse transfer) can be clearly associated with velocity fluctuations in distinct intervals of scale.
The results have been gained through a high-order finite-volume solver. Some practical aspects, benefits and challenges linked to the use of high-order numerics will also be discussed.

How to cite: Teissier, J.-M. and Müller, W.-C.: Inverse transfer of magnetic helicity in isothermal supersonic turbulence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11566, https://doi.org/10.5194/egusphere-egu22-11566, 2022.

In the solar wind, the differential flow between the alpha particles and the protons is an important source of free energy for driving A/IC waves and FM/W waves unstable. Large-scale slow-mode waves can modulate the differential flow, leading to non-negligible locally time-dependent changes in the drift velocity.

We investigate the behaviour of the maximum differential flow with multi-fluid wave theory in the parameter range 0<Uα/VA,p<1.5 and 0.1<βp<10 assuming quasi-perpendicular propagation of the slow mode wave, where Uα is the background alpha particle beam speed, VA,p is the proton Alfvén velocity, and βp is the ratio of the thermal proton energy to the magnetic field energy. We derive an analytical expression for the fluctuation in differential flow, the result of which we confirm through numerical evaluation of the multi-fluid wave equation. The thresholds in terms of Uα/VA,p for the instability of the A/IC and FM/W instabilities in the presence of slow mode waves decrease with increasing slow-mode amplitude and decreasing βp.

We statistically investigate the differential flow between alpha particles and protons based on spacecraft measurements with Solar Orbiter for intervals with clearly identified slow-mode waves as an observational test of our theoretical predictions. We find that slow mode fluctuations play an important role in the driving of A/IC and FM/W instabilities which are important for the energy transfer in the solar wind.

How to cite: Zhu, X., Verscharen, D., He, J., and Owen, C. J.: Slow-Mode-Driven Alfvén/Ion-Cyclotron (A/IC) and Fast-Magnetosonic/Whistler (FM/W) Instabilities in the Presence of an Alpha-Particle Beam in the Solar Wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11941, https://doi.org/10.5194/egusphere-egu22-11941, 2022.

EGU22-12969 | Presentations | ST1.9

Local Emission of Whistler Waves by Landau Resonance As a Signature of a Converging Magnetic Hole 

Wence Jiang, Daniel Verscharen, Hui Li, Chi Wang, and Kristopher Klein

Magnetic holes are plasma structures that trap a large number of particles in a magnetic field that is weaker than its surroundings. The unprecedented high time-resolution in-situ observations by NASA's Magnetospheric Multi-Scale (MMS) mission enable us to study the particle dynamics in the Earth's magnetosheath plasma in great detail. For the first time, we reveal the local generation of whistler waves by the Landau-resonant instability of electron beams as a response to the large-scale evolution of a magnetic hole. As the magnetic hole converges, we find a pair of counter-streaming electron beams are formed near the hole's center as a consequence of the combined action of betatron cooling and Fermi acceleration. The beams trigger the generation of slightly oblique whistler waves near the hole center, which is supported by a remarkable agreement between observations and our ALPS model predictions. Our findings show that kinetic effects and wave-particle interactions are fundamental to the dynamics and the evolution of magnetic holes as an important type of coherent structures in collisionless plasmas.

How to cite: Jiang, W., Verscharen, D., Li, H., Wang, C., and Klein, K.: Local Emission of Whistler Waves by Landau Resonance As a Signature of a Converging Magnetic Hole, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12969, https://doi.org/10.5194/egusphere-egu22-12969, 2022.

EGU22-12990 | Presentations | ST1.9

HelioSwarm: The Nature of Turbulence in Space Plasma 

Kristopher Klein and Harlan Spence and the The HelioSwarm Science Team

Quantifying the nature of turbulent fluctuations and the associated cascade of energy requires simultaneous measurements at multiple points spanning several characteristic length scales. Here, we present the HelioSwarm mission concept, which has been designed to reveal the three-dimensional, dynamic mechanisms controlling the physics of plasma turbulence. The HelioSwarm Observatory measures the plasma and magnetic fields with a novel configuration of spacecraft in the solar wind, magnetosheath, and magnetosphere. These simultaneous multi-point, multi-scale measurements span MHD, transition, and ion-scales, allowing us to address two overarching science goals: 1) Reveal the 3D spatial structure and dynamics of turbulence in a weakly collisional plasma and 2) Ascertain the mutual impact of turbulence near boundaries and large-scale structures. Addressing these goals is achieved using a first-ever "swarm" of nine spacecraft, consisting of a "hub" spacecraft and eight "node" spacecraft. The nine spacecraft co-orbit in a lunar resonant Earth orbit, with a 2-week period and an apogee/perigee of ~60/11 Earth radii. Flight dynamics design and on-board propulsion produce ideal inter-spacecraft separations ranging from fluid scales (1000's of km) to sub-ion kinetic scales (10's of km) in the necessary geometries to enable the application of a variety of established analysis techniques that distinguish between proposed models of turbulence. Each node possesses an identical instrument suite that consists of a Faraday cup, a fluxgate magnetometer, and a search coil magnetometer. The hub has the same instrument suite as the nodes, plus an ion electrostatic analyzer. With these measurements, the HelioSwarm Observatory promises an unprecedented view into the nature of space plasma turbulence.

How to cite: Klein, K. and Spence, H. and the The HelioSwarm Science Team: HelioSwarm: The Nature of Turbulence in Space Plasma, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12990, https://doi.org/10.5194/egusphere-egu22-12990, 2022.

In the present paper, we have studied the relationship between the Extreme Ultraviolet Imaging Telescope (EIT) waves phenomena with solar flares, coronal holes, solar winds, and coronal mass ejections (CMEs) events. The EIT/ SOHO instrument recorded 176 EIT events during the above period (March 25, 1997-June 17, 1998) and the EIT waves list was published by Thompson & Myers (2009). After temporal matching of EIT wave events with CMEs phenomena, we find that corresponding to 58 EIT wave events, no CMEs events were recorded and thus we excluded 58 EIT wave events from the present study. Out of 176 EIT wave events, only 106 are accompanied by CMEs phenomena. The correlation study of the speed of EIT wave events and CMEs events of 106  events shows poor correlation r= 0.32, indicating that the EIT waves and CMEs events do not have a common mechanism of origin, and also indicate that some other factor is working in the formation of  CMEs from EIT waves. Further, We have also matched the spatial matching EIT wave sources as indicated by Thomson & Myers (2009) with CHs and flares and found that CMEs appear to be associated with EIT wave phenomena and CHs.  Earlier Verma & Pande (1989), Verma (1998) indicated that the CMEs may have been produced by some mechanism, in which the mass ejected by solar flares or active prominences, gets connected with the open magnetic lines of CHs (source of high-speed solar wind streams) and moves along them to appear as CMEs. Most recently Verma & Mittal (2019)  proposed a  methodology to understand the origin of CMEs through magnetic reconnection of   CHs open magnetic field and solar flares.  In the present paper, we proposed a scenario/ 2-dimensional model, in which the origin of CMEs through reconnection of EIT waves and solar winds coming from the CHs and also found that the calculated CMEs velocity after reconnection of EIT waves and solar winds coming from the CHs are in very close to the observed CMEs linear velocity. We also calculated the value of the correlation coefficient between the observed linear velocity of CME events and the calculated value of CMEs velocity after reconnection and found the value as r=0.884. The value of correlation as r=0.884 is excellent and supports the proposed methodology.  Finally, we have also discussed the relationship of EIT wave phenomena with other solar phenomena, in the present scenario of solar heliophysics phenomena.

 

 

References:

Thompson, B. J. & Myers, D. C. (2009) APJS, 183, 225.
Verma, V. K. & Pande, M. C. (1989) Proc. IAU Colloq. 104 Solar and Stellar Flares (Poster Papers), Stanford University, Stanford, USA, p.239.
Verma, V. K.(1998) Journal of Geophysical Indian Union, 2, 65.
Verma, V. K. & Mittal, N.(2019) Astronomy Letters, 45, 164-176.

How to cite: Verma, V.: On Relation Between EIT Waves Phenomena with Other Solar Phenomena, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-56, https://doi.org/10.5194/egusphere-egu22-56, 2022.

EGU22-434 | Presentations | ST1.10

Studying the internal topology of Heliospheric Flux-ropes 

Marcel Ayora Mexia and Teresa Nieves-Chinchilla

In heliophysics, a flux rope could be defined as a confined magnetized plasma within magnetic field lines wrapping around an axis in a twisting but not necessarily a monotonic way. Nieves-Chinchilla et al. 2016, 2018 describes a flux rope model built on the flexibility of a non-orthogonal coordinate system that adds complexity in the magnetic structure with the  incorporation of current density components that are generalized in a polynomial series. This work aims to develop a methodology to explore the current density distribution within the helispheric flux ropes that will serve as constraint to the flux rope modeling and 3D reconstruction as well as to add understanding on the flux rope formation and evolution in the solar wind. 

How to cite: Ayora Mexia, M. and Nieves-Chinchilla, T.: Studying the internal topology of Heliospheric Flux-ropes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-434, https://doi.org/10.5194/egusphere-egu22-434, 2022.

EGU22-435 | Presentations | ST1.10

Study of heliospheric magnetic flux rope instabilities driven by distortions 

Samuel Capellas Coderque and Teresa Nieves-Chinchilla

Heliospheric magnetic flux ropes (MFRs) are usually considered to be the magnetic structure that dominates the transport of mass and energy from the Sun into the heliosphere. They entrain a confined plasma within a helically organized magnetic topology, transporting magnetic flux and helicity into the heliosphere, as well as being the main driver of geomagnetic activity.

Following the methodology introduced by Florido-Llinas. et. al. (Sol. Phys. 295, 118, 2020) we carry out a further study to evaluate the effect of distortions in MFR stability in the heliosphere. This way, we gain an insight in the understanding of the dynamical processes ruling the propagation and evolution of MFRs in the interplanetary medium, in a view to improve our space weather forecasting capability.

How to cite: Capellas Coderque, S. and Nieves-Chinchilla, T.: Study of heliospheric magnetic flux rope instabilities driven by distortions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-435, https://doi.org/10.5194/egusphere-egu22-435, 2022.

EGU22-437 | Presentations | ST1.10

The Grad-Shafranov reconstruction technique: overview, improvements and analysis 

Jordi Jumilla Lorenz and Teresa Nieves-Chinchilla

Heliospheric magnetic flux ropes (MFRs) are usually considered to be the magnetic structures in the solar wind confining plasma in a static or dynamic equilibria. They are also associated with the internal structure of the Coronal Mass Ejections (CMEs), the main drivers of geomagnetic activity. In the Heliosphere, MFRs can be described as straight axial-symmetric geometry with a variation with radius and angle of pressure and magnetic field.

Several missions such as STEREO or Solar Orbiter provide in-situ measurements of such magnetic structures. A well-known method to analyse them is the Grad-Shafranov reconstruction technique. In this article we provide a detailed overview, review of its variations and improvements and analysis of new events using this technique. Both quantitative and qualitative classification of such MFRs is done according to its orientation, shape and magnetic field and pressure profiles.

Based on the flux rope model described by Nieves-Chinchilla et al. (2018), we also investigate the physical characteristics and the underlying basic equilibrium state.

How to cite: Jumilla Lorenz, J. and Nieves-Chinchilla, T.: The Grad-Shafranov reconstruction technique: overview, improvements and analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-437, https://doi.org/10.5194/egusphere-egu22-437, 2022.

EGU22-899 | Presentations | ST1.10

Optimization of parameters of CME initiation in the MHD simulation suite 

Keiji Hayashi, Chin-Chun Wu, and Kan Liou

One of the important challenges in the field of space weather study is to predict the arrival time of the shocks associated with the interplanetary coronal mass ejections (ICMEs). In many Sun-to-Earth magnetohydrodynamic (MHD) simulations, a numerical perturbation mimicking the initial stage of the CME/ICME event is given at a position of corresponding coronal event in a steady state of the solar corona and/or solar wind. Then, the temporal evolution of the perturbed solar corona and solar wind are simulated. The numerical perturbation is a critical component in this kind of CME simulation model.

Recently we have developed a new model suite combining our two existing MHD models, one is for the solar corona (Hayashi, 2005 ApJ 161:480) and the other is for solar wind (Wu+, 2012 Solar Physics 295:25; Wu+ 2020 JASTP 201:105211). In this model suite, plasma perturbations expressed with Gaussian spatial distribution and several parameters are given to initiate the CME/ICME simulation. For better simulating the Sun-Earth CME and ICME propagation, we made an iterative Newton-Raphson type minimization module for optimizing the perturbation parameters such that the differences in the CME speed within r < 30 Rsun and the arrival time of the CME-driven shocks at the Earth between the observation and simulation will be reduced simultaneously. We will report the results, in particular, which kinetic, thermal, and/or magnetic parameters are most important for numerically reproducing the ICMEs propagation from corona to 1 AU in this analysis study.

How to cite: Hayashi, K., Wu, C.-C., and Liou, K.: Optimization of parameters of CME initiation in the MHD simulation suite, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-899, https://doi.org/10.5194/egusphere-egu22-899, 2022.

EGU22-1017 | Presentations | ST1.10

Evidence of a complex structure within the 2013 August 19 coronal mass ejection. Radial and longitudinal evolution in the inner heliosphere 

Laura Rodríguez-García, Teresa Nieves-Chinchilla, Raúl Gómez-Herrero, Ioannis Zouganelis, Angelos Vourlidas, Laura Balmaceda, Mateja Dumbovic, Lan Jian, Leila Mays, Fernando Carcaboso, Luiz Fernando Guedes-Dos Santos, and Javier Rodríguez-Pacheco

Context. Late on 2013 August 19, a coronal mass ejection (CME) erupted from an active region located near the far-side central meridian from Earth’s perspective. The event and its accompanying shock were remotely observed by the STEREO-A, STEREO-B and SOHO spacecraft. The interplanetary (IP) counterpart (ICME) was intercepted by MESSENGER near 0.3 au, and by both STEREO-A and STEREO-B, near 1 au, which were separated by 78 degrees in heliolongitude.

Aims. The main objective of this study is to follow the radial and longitudinal evolution of the ICME throughout the inner heliosphere, and to examine possible scenarios for the different magnetic flux-rope (MFR) configuration observed on the solar disk, and measured in-situ at the locations of MESSENGER and STEREO-A, separated by 15 degrees in heliolongitude, and at STEREO-B, which detected the ICME flank.

Methods. Solar disk observations are used to estimate the ‘MFR type’, namely, the magnetic helicity, axis orientation and axial magnetic field direction of the MFR. The graduated cylindrical shell model is used to reconstruct the CME in the corona. The analysis of in-situ data, specifically, plasma and magnetic field, is used to estimate the global IP shock geometry and to derive the MFR type at different in-situ locations, which is compared to the type estimated from solar disk observations. The elliptical cylindrical analytical model is used for the in-situ MFR reconstruction.

Results. Based on the CME geometry and on the spacecraft configuration, we find that the MFR structure detected at STEREO-B belongs to the same ICME detected at MESSENGER and STEREO-A. The opposite helicity deduced at STEREO-B, might be due to the spacecraft intercepting one of the legs of the structure far from the MFR axis, while STEREO-A and MESSENGER are crossing through the core of the MFR. The different MFR orientations measured at MESSENGER and STEREO-A arise probably because the two spacecraft measure a curved, highly distorted and rather complex MFR topology. The ICME may have suffered additional distortion in its evolution in the inner heliosphere, such as the west flank is traveling faster than the east flank when arriving near 1 au.

How to cite: Rodríguez-García, L., Nieves-Chinchilla, T., Gómez-Herrero, R., Zouganelis, I., Vourlidas, A., Balmaceda, L., Dumbovic, M., Jian, L., Mays, L., Carcaboso, F., Guedes-Dos Santos, L. F., and Rodríguez-Pacheco, J.: Evidence of a complex structure within the 2013 August 19 coronal mass ejection. Radial and longitudinal evolution in the inner heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1017, https://doi.org/10.5194/egusphere-egu22-1017, 2022.

EGU22-1124 | Presentations | ST1.10

Multi-ensemble MHD coronal modeling to improve background wind for CME propagation for EUHFORIA 2.0 

Barbara Perri, Peter Leitner, Michaela Brchnelova, Tinatin Baratashvili, Blazej Kuzma, Fan Zhang, Andrea Lani, Stefaan Poedts, Andrey Kochanov, Evangelia Samara, Allan Sacha Brun, and Antoine Strugarek

Space weather has the difficult task to try to anticipate the propagation of eruptive events such as coronal mass ejections (CMEs) in order to assess their possible impact on the Earth’s space environment. This requires an accurate description of the background in which CMEs propagate, mainly the continuum ejecta of particles that is the solar wind and the dynamo-generated heliospheric magnetic field. This proves challenging as the solar wind and dynamo magnetic field are interacting with each other depending on the activity cycle of our star, both at large and small scales. To be able to model accurately such a wide variety of scales and parameter regimes, the approach used by the EUHFORIA 2.0 project is to use a chain of models, taking advantage of existing codes to combine their strengths through numerical coupling across the heliosphere. The first step of this chain is the data-driven modeling of the inner corona, from photosphere measurements up until 0.1 AU, and it proves especially critical as it serves as boundary condition for the rest of the models.

In that regard, we will present here two coronal MHD models implemented as an alternative to the semi-empirical WSA and SCS models used so far in EUHFORIA. By using the COOLFluiD framework, we developed a new coronal model with implicit solving methods and unstructured meshes, which proves faster than traditional explicit methods on regular grids. We used the coronal code Wind-Predict to benchmark this new model for the simple polytropic approximation in the first place, and we present the similarities and differences obtained for data-driven configurations and compare them with observations (white-light images, coronal hole boundaries, in-situ data at 1 AU after coupling with EUHFORIA). We then present the improvements foreseen for each codes, especially for the heating terms: Wind-Predict will incorporate self-consistent Alfvén waves while COOLFluiD will use ad-hoc heating terms and a multi-species treatment. We will finally discuss the implications for the coupling with EUHFORIA and the CME propagation between 0.1 and 1 AU.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) and the ESA project "Heliospheric modelling techniques“ (Contract No. 4000133080/20/NL/CRS).

How to cite: Perri, B., Leitner, P., Brchnelova, M., Baratashvili, T., Kuzma, B., Zhang, F., Lani, A., Poedts, S., Kochanov, A., Samara, E., Brun, A. S., and Strugarek, A.: Multi-ensemble MHD coronal modeling to improve background wind for CME propagation for EUHFORIA 2.0, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1124, https://doi.org/10.5194/egusphere-egu22-1124, 2022.

EGU22-1964 | Presentations | ST1.10

Multipoint Interplanetary Coronal Mass Ejections Observed with Solar Orbiter, BepiColombo, Parker Solar Probe, Wind, and STEREO-A 

Christian Möstl, Andreas J. Weiss, Martin A. Reiss, Tanja Amerstorfer, Rachel L. Bailey, Maike Bauer, David Barnes, Jackie A. Davies, Richard A. Harrison, Emma E. Davies, Daniel Heyner, Tim S. Horbury, and Stuart D. Bale

We present the results of a search for multipoint in situ and imaging observations of interplanetary coronal mass ejections (ICMEs) with the Heliophysics System Observatory, from 2020 April to present day. This builds up on our recent publication in ApJ Letters introducing the living ICME lineup catalog available at https://helioforecast.space/lineups. We highlight a few new lineup events captured by those spacecraft from September to November 2021, when all were located within 50 degrees east of the Sun-Earth line. Multi-messenger observations of ICME flux ropes and shocks are much needed to make progress on the understanding of the global magnetic configuration of ICMEs, space weather forecasting, the magnetic connectivity of the solar wind to the Sun and the propagation of solar energetic particles.

How to cite: Möstl, C., Weiss, A. J., Reiss, M. A., Amerstorfer, T., Bailey, R. L., Bauer, M., Barnes, D., Davies, J. A., Harrison, R. A., Davies, E. E., Heyner, D., Horbury, T. S., and Bale, S. D.: Multipoint Interplanetary Coronal Mass Ejections Observed with Solar Orbiter, BepiColombo, Parker Solar Probe, Wind, and STEREO-A, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1964, https://doi.org/10.5194/egusphere-egu22-1964, 2022.

EGU22-2040 | Presentations | ST1.10

Deflection of CMEs in Different Background Magnetic Fields 

Tibor Torok, Michal Ben-Nun, Cooper Downs, Viacheslav S. Titov, Ronald M. Caplan, and Roberto Lionello

As suggested by Isenberg and Forbes (2007) and demonstrated numerically by Kliem et al. (2012), the Lorentz forces stemming from the interaction of the axial current in an erupting magnetic flux rope (MFR) with an ambient magnetic-field component that has the same orientation as the initial MFR axis leads to a rotation of the top part of the MFR about its rise direction. In principle, the same mechanism can be applied to CMEs that propagate in a unipolar radial field in the corona or inner heliosphere. In such cases, however, the corresponding forces should not lead to a rotation, but to a deflection of the CME front, thereby significantly altering the CME's magnetic orientation. Apart from a brief consideration in Lugaz et al. (2011), such deflections have, to the best of our knowledge, not yet been studied systematically. 

Here we employ three-dimensional (3D) idealized magnetohydrodynamic (MHD) simulations to investigate this effect in background fields of increasing complexity. We first consider a freely expanding toroidal MFR in a uniform background field, as well as the propagation of a compact, line-tied MFR in a unipolar radial field. In both cases, we find significant deflections. We then use a more realistic setup, in which we erupt an MFR from a localized, bipolar source region into a global dipole field and solar wind, which allows for a significant expansion of the MFR before it encounters open field. We perform a parametric study in which we vary the location and magnetic orientation of the source region, as well as the handedness (helicity sign) of the MFR. In this presentation, we discuss the influence of these parameters on the CME trajectory.

How to cite: Torok, T., Ben-Nun, M., Downs, C., Titov, V. S., Caplan, R. M., and Lionello, R.: Deflection of CMEs in Different Background Magnetic Fields, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2040, https://doi.org/10.5194/egusphere-egu22-2040, 2022.

EGU22-2755 | Presentations | ST1.10

3D Hybrid Simulations of the Interaction between Self-Consistently Generated Extreme Solar Events and the Terrestrial Geo-Environment 

Emanuele Cazzola, Dominique Fontaine, and Philippe Savoini

In this work we present some results from 3D hybrid simulations of the interaction between extreme solar events, such as Coronal Mass Ejections (CMEs) or Co-rotating Interaction Regions (CIRs), and a 3D Earth-like geo-environment. The events are generated and let evolve self-consistently in order to represent their typical realistic Earth-hitting characteristics as described by the averaged profiles obtained from decades of observations at 1 AU. Both shock-less and shock-driven configurations are considered to highlight the differences between the two scenarios in terms of their kinetic dynamics, as well as in terms of the effects on the Bow-Shock / Magnetosheath / Magnetosphere system.

How to cite: Cazzola, E., Fontaine, D., and Savoini, P.: 3D Hybrid Simulations of the Interaction between Self-Consistently Generated Extreme Solar Events and the Terrestrial Geo-Environment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2755, https://doi.org/10.5194/egusphere-egu22-2755, 2022.

EGU22-2833 | Presentations | ST1.10

Magnetic complexity changes within interplanetary coronal mass ejections: insights from a statistical study based on radially-aligned spacecraft observations 

Camilla Scolini, Réka M. Winslow, Noé Lugaz, Tarik M. Salman, Emma E. Davies, and Antoinette B. Galvin

We present the first statistical analysis of complexity changes affecting the magnetic structure of interplanetary coronal mass ejections (ICMEs), with the aim of answering the following questions: how frequently do ICMEs undergo magnetic complexity changes during propagation? What are the causes of such changes? Do the in situ properties of ICMEs differ depending on whether they exhibit complexity changes? 

We consider multi-spacecraft observations of 31 ICMEs carried out by MESSENGER, Venus Express, ACE, and STEREO between 2008 and 2014 during periods of radial alignment. By analyzing their magnetic properties at the inner and outer observing spacecraft, we identify complexity changes which manifest as fundamental alterations in the ICME magnetic topology, or as significant re-orientations of the ICME magnetic structure. Plasma and suprathermal electron data at 1 au, as well as simulations of the ambient solar wind enable us to reconstruct the propagation scenario for each event, and to identify critical factors controlling their evolution. 

Results show that 65% of ICMEs change their complexity between Mercury and 1 au, and that the interaction with multiple large-scale solar wind structures is the main driver of these changes. Furthermore, 71% of ICMEs observed at large radial (>0.4 au) but small longitudinal (<15 degrees) separations exhibit complexity changes, indicating that the propagation over large distances strongly affects ICMEs. Results also suggest ICMEs may be magnetically coherent over angular scales of at least 15 degrees, supporting earlier theoretical and observational estimates. This work provides statistical evidence that magnetic complexity changes are consequences of ICME interactions with large-scale solar wind structures, rather than intrinsic to ICME evolution, and that such changes are only partly identifiable from in situ measurements at 1 au.

How to cite: Scolini, C., Winslow, R. M., Lugaz, N., Salman, T. M., Davies, E. E., and Galvin, A. B.: Magnetic complexity changes within interplanetary coronal mass ejections: insights from a statistical study based on radially-aligned spacecraft observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2833, https://doi.org/10.5194/egusphere-egu22-2833, 2022.

EGU22-3474 | Presentations | ST1.10

Data-driven modelling of the evolution of CME properties in the low-corona: AR12473 

Andreas Wagner, Emilia Kilpua, Daniel J. Price, Jens Pomoell, Anshu Kumari, Farhad Daei, and Ranadeep Sarkar

To better predict the impacts of solar eruptions on Earth, understanding the low-corona evolution of CMEs is crucial because this influential early phase is highly dynamic. We therefore investigate the evolution of CME properties, such as the evolution of flux rope footpoints as well as the magnetic flux enclosed in the flux rope, during this stage of the eruption. To simulate the eruption we make use of the data-driven time-dependent magnetofrictional method (TMFM), which has been proven to accurately capture a flux rope's early evolution and lift-off. We then developed a semi-automatized method for identifying the flux rope and extracting these flux ropes from 3D data cubes and tracking their evolution in time. The extraction algorithm is based on the twist parameter Tw in a 2D plane close to the polarity inversion line as a proxy for the flux rope and its temporal evolution. It is then applied to TMFM simulations of the active region AR12473, which produced an eruption on 28th of December 2015 (see e.g., Price et al, 2020). This CME was also accompanied by an M1.9 flare, that peaked at about 12:45 UT. The extracted flux rope footpoints are then compared against observational data from SDO's AIA instrument in the 1600 Å wavelength. This comparison yields a very good match with coverage parameters (see Asvestari et al, 2019) in the range of 60-70 %. The magnetic flux is extracted from the footpoints that are rooted in one specific polarity region. 

How to cite: Wagner, A., Kilpua, E., Price, D. J., Pomoell, J., Kumari, A., Daei, F., and Sarkar, R.: Data-driven modelling of the evolution of CME properties in the low-corona: AR12473, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3474, https://doi.org/10.5194/egusphere-egu22-3474, 2022.

EGU22-5063 | Presentations | ST1.10

Case study of interacting large-scale solar wind phenomena in the heliosphere 

Paul Geyer, Mateja Dumbovic, and Manuela Temmer

The interaction of interplanetary coronal mass ejections (ICMEs) and stream interaction regions (SIRs) gives rise to complex heliospheric plasma and magnetic field conditions. Considering the different magnetic configurations of both phenomena as well as the source regions in the solar corona, there is also the possibility of magnetic reconnection either at coronal heights or farther out in the heliosphere.

The event of February 7th, 2014 shows clear signatures of a qualitative alteration of the ICME structure in ACE plasma and magnetic field data. There is a significant drop of the magnetic field strength inside the FR simultaneously to an enhancement in temperature and a high variability of speed. The flow angle reversal expected to take place at the stream interface sharply coincides with the onset of the ICME magnetic field rotations and drop of temperature below expected temperature. The speed inside the flux rope, yet showing the aforementioned variations, overall features a decline from the front to the rear of the ICME. The launch site of the ICME is derived from SDO AIA data, showing its location to be 30° West from a N-S elongated coronal hole.

These results imply a deterioration of the FR due to magnetic reconnection, either caused by the proximity of CH and CME eruption site and favorable magnetic configurations, or the heliospheric interaction of the associated SIR and ICME. WSA-ENLIL simulations suggest that the ICME catches up with the SIR close to Earth, which, along with the in-situ signatures, implies the simultaneous occurrence of stream interface and flux rope onset. The declining speed profile that is characteristic for quiescent ICME spatial evolution suggests no high-speed stream is inhibiting expansion from behind. Due to its complexity, this event provides a great opportunity to study the interaction of ICMEs and SIRs.

How to cite: Geyer, P., Dumbovic, M., and Temmer, M.: Case study of interacting large-scale solar wind phenomena in the heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5063, https://doi.org/10.5194/egusphere-egu22-5063, 2022.

EGU22-5544 | Presentations | ST1.10

Eruption and Interplanetary Evolution of a Stealth Streamer-blowout CME Observed at ~0.5 AU 

Sanchita Pal, Emilia Kilpua, Simon Good, Benjamin Lynch, Erika Palmerio, Eleanna Asvestari, Jens Pomoell, and Michael Stevens

The orbit of the Parker Solar Probe (PSP) during the 5th encounter with the Sun presented an opportunity for a multi-observation analysis including the observations of Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) coronagraphs and Large Angle and Spectrometric Coronagraph (LASCO) coronagraphs. Streamer-blowout coronal mass ejections (SBO-CMEs) are the dominant CME population during solar minimum. With the aid of extrapolated coronal fields and remote observations of the off-limb low corona, we study the initiation of an SBO-CME preceded by consecutive CME eruptions following a multi-stage sympathetic breakout scenario. The suprathermal electron pitch-angle distributions (PADs) and magnetic field observations by PSP suggest that draping of interplanetary magnetic field lines about the CME caused a curvature in the adjacent heliospheric current sheet, initiated magnetic reconnection with the CME flux rope about ~45 hours before it encountered PSP, and eroded ~38% of its initial poloidal magnetic flux at ~0.5 AU. This study covering inner heliospheric observation and analysis of SBO-CME magnetic content provides important implications for the origin of twisted magnetic field lines in SBO-CME flux ropes as the flux rope is not perturbed much by the interplanetary propagation. Also, the multi-spacecraft observations allowed us to estimate the distances where reconnection between the flux rope and its surroundings may be initiated. 

How to cite: Pal, S., Kilpua, E., Good, S., Lynch, B., Palmerio, E., Asvestari, E., Pomoell, J., and Stevens, M.: Eruption and Interplanetary Evolution of a Stealth Streamer-blowout CME Observed at ~0.5 AU, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5544, https://doi.org/10.5194/egusphere-egu22-5544, 2022.

EGU22-5613 | Presentations | ST1.10

Assessing the potential of heliospheric imager data assimilation to improve CME modelling. 

Luke Barnard, Mathew Owens, and Chris Scott

Modelling the heliospheric evolution of Coronal Mass Ejections (CMEs) is challenging and fraught with uncertainty for a range of confounding reasons. For example, there are significant uncertainties in the boundary conditions of heliospheric numerical models and such models often use CME parameterisations which are known to be overly simplistic e.g. hydrodynamic perturbations without magnetic structure. Consequently, the uncertainty on modelled CME evolution remains high and simulations often struggle to accurately represent both in-situ and remotely sensed CME observations.

Data assimilation (DA) provides a framework for merging observations and a model of a system to return simulations that better represent the true state of a system. We are exploring how to use data assimilation techniques with the white-light Heliospheric Imager (HI) CME observations to generate CME simulations that better represent the observed evolution of CMEs.

Here we present the results of a set of Observing System Simulation Experiments that begin to quantify the potential gains from assimilating HI data into the HUXt solar wind model, using a particle filter data assimilation scheme based on Sequential Importance Resampling.

We explore several specific questions: 1) By how much does the HI DA improve the simulated kinematics profiles of CMEs. 2) From which observing location are HI data best able to improve simulations of Earth directed CMEs. 3) Is it necessary to assimilate the full HI image data, or is it sufficient to assimilate HI derived data products, such as the time-elongation profile of the CME front.

How to cite: Barnard, L., Owens, M., and Scott, C.: Assessing the potential of heliospheric imager data assimilation to improve CME modelling., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5613, https://doi.org/10.5194/egusphere-egu22-5613, 2022.

The Heliospheric Expert Service Centre (H-ESC), part of ESA’s space weather service network, serves to provide existing heliophysics models for the provision of alerts and forecasts of space weather conditions at Earth and throughout the heliosphere. This is achieved by means of remote sensing and in-situ measurements of space weather transients, including Coronal Mass Ejections and high-speed solar wind streams, combined with advanced MHD modelling to predict their arrival times at points of interest in the heliosphere. Two such models include the European Heliospheric Forecasting Information Asset (EUHFORIA) and the ENLIL model operated by the UK Met Office, both of which are currently federated through the H-ESC portal. As a means to test both models, we perform daily runs of the EUHFORIA model using the same inputs (GONG magnetograms and CME cone-files) as the Met Office ENLIL simulations since the beginning of 2019, which are compared to real solar wind observations near Earth. We employ well-established model validation methodology by deriving contingency tables and the associated skill scores for both models as a means to assess their ability to make accurate space weather forecasts during this period of parallel operation.

How to cite: Barnes, D.: Assessment and Validation of Daily Enlil and EUHFORIA Simulations During 2019–2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5676, https://doi.org/10.5194/egusphere-egu22-5676, 2022.

EGU22-5935 | Presentations | ST1.10

Modelling CME rotation during propagation in the heliosphere with EUHFORIA 

Anwesha Maharana, Camilla Scolini, Brigitte Schmiede, and Stefaan Poedts

Coronal mass ejections (CMEs) are large scale magnetized plasma eruptions from the Sun that propagate to Earth and cause disruptions in space and ground-based technologies. While propagating through the heliosphere, they undergo interaction with other CMEs, as well as structures in the solar wind like high-speed streams, and co-rotating/stream interaction regions. We present a case-study of two Earth-directed interacting CMEs that erupted from the Sun on September 8, 2014, and September 10, 2014, respectively. While the first CME was a side hit, it is the second CME which is the focus of this study. With remote observations of the CME helicity and tilt, the second CME was predicted to be geoeffective. However, a mismatch in the tilt of the second CME was observed close to Earth, pointing to CME rotation during its propagation. Unexpectedly, the ejecta resulted in positive Bz but a geoeffective sheath was developed during the evolution and the interaction in the heliosphere that resulted in a minimum Dst ~ -100nT at Earth. Hence, the geoeffectiveness of the various sub-structures involved in this event was mispredicted. 

It is challenging to capture the complete picture of the CME and solar wind dynamics with in-situ observations taken at sparse localized points in the heliosphere. Therefore, we perform 3D MHD simulations that provide a global picture, making it convenient to probe into the interesting phenomena of this event. With the EUropean Heliosphere FORecasting Information Asset (EUHFORIA), we model the background solar wind in 3D, launch the flux rope CMEs in it and let the CME evolve till Earth. In this work, we aim to reproduce the observed plasma and magnetic field properties, especially the negative Bz of the sheath and the positive Bz of the ejecta at Earth. We address the possible factors and processes responsible for the development of geoeffectiveness from the CME rotation, the interplay of the two CMEs and the heliosphere. 

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0)

How to cite: Maharana, A., Scolini, C., Schmiede, B., and Poedts, S.: Modelling CME rotation during propagation in the heliosphere with EUHFORIA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5935, https://doi.org/10.5194/egusphere-egu22-5935, 2022.

EGU22-6012 | Presentations | ST1.10

Evaluations of Numerical Flux Schemes of a Coronal MHD Model 

Fan Zhang, Barbara Perri, Michaela Brchnelova, Tinatin Baratashvili, Błażej Kuźma, Peter Leitner, Andrea Lani, and Stefaan Poedts

Space weather forecasting requires precise estimation of the arrival time of eruptive events, which typically propagate through and interact with the solar atmosphere and solar wind. Therefore, the arrival time estimation depends on the accuracy of modelling the solar atmosphere and the complex interactions. For instance, the EUHFORIA 2.0 project expects an accurate and efficient coronal model that covers the region from the surface of the Sun up to 0.1AU, serving as the inner boundary condition for the heliospheric model.

Based on the open-source code COOLFluiD, we have developed a fully implicit MHD coronal model. The model has been validated by data-driven coronal simulations, and the fully implicit temporal solution significantly accelerates the numerical simulations. More physical mechanisms, e.g., the heating term(s), and numerical techniques, e.g., high-order schemes, are being developed to improve this model further. In this work, we specifically focus on the numerical flux schemes (Lax-Friedrichs, HLL, etc.) of the finite-volume MHD solver used by the coronal model, and evaluate their performance and impact on the coronal simulations. Both the internal structures and the quantities at the outer boundary are quantitatively compared.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 870405 (EUHFORIA 2.0).

 

How to cite: Zhang, F., Perri, B., Brchnelova, M., Baratashvili, T., Kuźma, B., Leitner, P., Lani, A., and Poedts, S.: Evaluations of Numerical Flux Schemes of a Coronal MHD Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6012, https://doi.org/10.5194/egusphere-egu22-6012, 2022.

EGU22-6205 | Presentations | ST1.10

On the utility of flux rope models for CME magnetic structure below 30Rs 

Benjamin Lynch, Nada Al-Haddad, Wenyuan Yu, Erika Palmerio, and Noé Lugaz

We present a comprehensive analysis of the three-dimensional magnetic flux rope structure generated during the Lynch et al. (2019, ApJ 880, 97) magnetohydrodynamic (MHD) simulation of a global-scale, 360 degree-wide streamer blowout coronal mass ejection (CME) eruption. We create both fixed and moving synthetic spacecraft to generate time series of the MHD variables through different regions of the flux rope CME. Our moving spacecraft trajectories are derived from the spatial coordinates of Parker Solar Probe’s past Encounters 7 and 9 and future Encounter 23. Each synthetic time series through the simulation flux rope ejecta is fit with three different in-situ flux rope models commonly used to characterize the large-scale, coherent magnetic field rotations observed in a significant subset of interplanetary CMEs (ICMEs). We present each of the in-situ flux rope model fits to the simulation data and discuss the similarities and differences in the model flux rope spatial orientations, field strengths, and magnetic flux content. We compare in-situ model properties to those calculated with the MHD data for both classic bipolar and unipolar ICME flux rope configurations as well as more problematic profiles such as those with a significant radial component to the flux rope axis orientation or profiles obtained with large impact parameters. We find general agreement among the in-situ flux rope fitting results for the classic profiles and much more variation among results for the problematic profiles. We also present a comparison between the MHD simulation data and the in-situ model flux ropes in a hodogram representation of the magnetic field rotation. We conclude that the in-situ flux rope models are generally a decent approximation to the field structure, but all the caveats associated with in-situ flux rope models will still apply (and perhaps moreso) at distances below 30Rs. We discuss our results in the context of future PSP observations of CMEs in the extended corona.

How to cite: Lynch, B., Al-Haddad, N., Yu, W., Palmerio, E., and Lugaz, N.: On the utility of flux rope models for CME magnetic structure below 30Rs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6205, https://doi.org/10.5194/egusphere-egu22-6205, 2022.

EGU22-6941 | Presentations | ST1.10

Statistics on Alfvénic Structures of the Solar Wind in the inner Solar System 

Johannes Z. D. Mieth, Yannis Hilgers, Daniel Heyner, Karl-Heinz Glassmeier, and Ferdinand Plaschke

Based on measurements of the magnetometer MPO-MAG on board the spacecraft BepiColombo on its way to Mercury, we present a statistical overview on Alfvénic structures in the interplanetary magnetic field (IMF) in the inner solar system between approx. 0.3 – 1 AU and their implication on the offset calibration accuracy of space-borne magnetometers.
Different properties of the Alfvén waves are examined and statistically compared to each other, as are for example: orientation of the wave plane, orientation of the main magnetic field.
In addition to the spatial properties, the temporal properties like stability, occurrence rate and typical timescales of Alfvén Waves are also studied.
To highlight possible differences of the IMF between the inner Solar System and at Earth-distance, results are then compared to measurements of the Moon-orbiting ARTEMIS probes.

How to cite: Mieth, J. Z. D., Hilgers, Y., Heyner, D., Glassmeier, K.-H., and Plaschke, F.: Statistics on Alfvénic Structures of the Solar Wind in the inner Solar System, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6941, https://doi.org/10.5194/egusphere-egu22-6941, 2022.

EGU22-8017 | Presentations | ST1.10

Modeling of the CME on 2021 October 28 

Angelo Valentino and Jasmina Magdalenic

We present the evolution of the CME/flare event observed on 2021, October 28 . The GOES X1.1 class flare originated from the active region NOAA AR 2887, situated at the moment of eruption close to the central meridian. The full halo CME had also on disc signatures, i.e. the EIT wave and coronal dimming and was associated with the white light shock and the type II radio burst. The CME propagated with the projected line of the sight speed of about 1100 km/s and it seemed to be Earth directed.

However, only the associated shock wave was observed by the DSCOVR in-situ instruments, in the morning of October 31. The observations indicate that the CME’s propagation direction had a strong southward component, which induced only glancing blow and not a direct impact to Earth.

We reconstructed the CME, using SOHO/LASCO and STEREO/COR observations, and modeled it’s propagation in the inner heliosphere employing recently developed heliospheric model EUHFORIA (EUropean Heliospheric FORecasting Information Asset, Pomoell & Poedts, 2018).  After accurately modeling the observed CME we also made the ensemble runs with EUHFORIA to study how the changes of the propagation direction of the CME influence its impact to Earth.

How to cite: Valentino, A. and Magdalenic, J.: Modeling of the CME on 2021 October 28, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8017, https://doi.org/10.5194/egusphere-egu22-8017, 2022.

EGU22-8406 | Presentations | ST1.10

Analytical Modelling of Curved Cylindrical Flux Ropes 

Andreas Weiss, Teresa Nieves-Chinchilla, Christian Möstl, Martin Reiss, Jürgen Hinterreiter, Tanja Amerstorfer, and Rachel Bailey

We present our most recent results for an analytical flux rope model that includes the effects of curvature and torsion on the magnetic field. Our analytical model consists of a cylindrical flux rope that can be bent or twisted in any manner under the condition of axial and poloidal flux conservation. We can furthermore configure our model to exhibit any arbitrary radial twist distribution but we do not necessarily assume the structure to be force-free. The approach can serve as a first stepping point to better model the deformations of ICME flux ropes that are expected to occur due to longitudinal velocity differentials in the solar wind. It is briefly discussed how this model can be implemented in real-world simulations and how it can be extended to non-cylindrical shapes.

How to cite: Weiss, A., Nieves-Chinchilla, T., Möstl, C., Reiss, M., Hinterreiter, J., Amerstorfer, T., and Bailey, R.: Analytical Modelling of Curved Cylindrical Flux Ropes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8406, https://doi.org/10.5194/egusphere-egu22-8406, 2022.

EGU22-9583 | Presentations | ST1.10

Calibrating the WSA velocity in EUHFORIA based on PSP observations 

Evangelia Samara, Charles N. Arge, Rui F. Pinto, Stefaan Poedts, Jasmina Magdalenic, and Luciano Rodriguez

Coronal models, usually extending between the solar photosphere and ~30 Rs, are an integral part of many space weather forecasting tools. They reconstruct the magnetic field in the solar corona and provide the necessary plasma conditions for initiating heliospheric models such as EUHFORIA or Enlil. A big gap in literature is identified when it comes to the validation of such models because of lack of observations, especially in situ. Nevertheless, the launch of the Parker Solar Probe (PSP) has provided, for the first time, in situ observations very close to the Sun that can help with the evaluation of such models. In this work, we aim to calibrate the Wang-Sheeley-Arge (WSA) semi-empirical formula used in EUHFORIA for the reconstruction of plasma and magnetic parameters at 0.1 AU. We exploit PSP in situ measurements between 0.1 – 0.4 AU obtained from the first 8 perihelia. We show how a parametric study of the WSA formula influences the velocity and density distributions very close to the Sun, how the modeled distributions are compared to PSP observations and present the relevant forecasting results at PSP and Earth.

How to cite: Samara, E., Arge, C. N., Pinto, R. F., Poedts, S., Magdalenic, J., and Rodriguez, L.: Calibrating the WSA velocity in EUHFORIA based on PSP observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9583, https://doi.org/10.5194/egusphere-egu22-9583, 2022.

EGU22-10425 | Presentations | ST1.10

The pickup He+ velocity distributions embedded in a CME structure 

Keiichi Ogasawara, Berndt Klecker, Harald Kucharek, Maher Dayeh, and Robert Ebert

The velocity distribution functions (VDFs) of pickup He+ ions near a Coronal Mass Ejection (CME) are expected to be extremely variable due to the specific source particle distributions and the interactions with the shock passage, turbulence, and large scale magnetic structures. One of the most eminent examples is the shock injection process. Around interplanetary (IP) shocks, significant abundance enhancements of He+ pickup ions over He++ ions of solar wind origin (e.g., Chotoo et al., 2000) provided compelling evidence that the source population for the energetic particle population is not the solar wind itself, but rather the pickup ion population that contains more particles beyond the injection threshold due to the difference in VDF. However, due to the lack of high-resolution measurements of pickup ion’s energy and phase space densities, their kinetics are not well understood.

In this study, VDFs of He+ pickup ions are investigated for a typical quasi-perpendicular shock observed in the heart of the helium focusing cone. In order to calculate the VDFs of helium ions, pulse height information from each ion event in the PLasma And SupraThermal Ion Compostion (PLASTIC) instrument (Galvin et al., 2008) on the Solar Terrestrial Relations Observatory (STEREO) was utilized. During each electrostatic analyzer energy-per-charge (E/q) step (128 steps, 435.6 ms each), PLASTIC stores 512 raw pulse height events including E/q, time-of-flight, total energy, and arrival direction. This allows us to reproduce partial 3-dimensional VDFs for various ion species with ~2° angular resolution (Taut et al., 2018). Moreover, the concentration of He+ ions in the helium focusing cone increased the count rate significantly, and provided enough counting statistics to achieve 10 min cadence.

The IP shock that we focus on was driven by a coronal mass ejection producing a fast mode shock. Our study focuses on two regions: (1) VDFs within the CME sheath in the shock downstream, and (2) VDFs in the magnetic cloud. VDFs are analyzed in terms of particle heating/cooling, acceleration/deceleration, and pitch angle diffusion. The connectivity to the shock will also be investigated. In the far downstream region, correlation between the VDFs and the ambient magnetic field activities (the power spectra and the Alfvénic activity) are discussed in terms of how they modify the He+ pitch angle distributions.

References:

Chotoo, K., et al. (2000), The suprathermal seed population for corotating interaction region ions at 1 AU deduced from composition and spectra of H+, He++, and He+ observed on Wind, doi:10.1029/1998JA000015.

Taut, A., et al. (2018), Challenges in the determination of the interstellar flow longitude from the pickup ion cutoff, doi: 10.1051/0004-6361/201731796.

Galvin, A.B., Kistler, L.M., Popecki, M.A. et al. The Plasma and Suprathermal Ion Composition (PLASTIC) Investigation on the STEREO Observatories. Space Sci Rev 136, 437–486 (2008). https://doi.org/10.1007/s11214-007-9296-x

 

How to cite: Ogasawara, K., Klecker, B., Kucharek, H., Dayeh, M., and Ebert, R.: The pickup He+ velocity distributions embedded in a CME structure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10425, https://doi.org/10.5194/egusphere-egu22-10425, 2022.

EGU22-10570 | Presentations | ST1.10

Estimating uncertainties in the back-mapping of the fast solar wind 

Alexandros Koukras, Rony Keppens, and Laurent Dolla

Although the sources of the fast solar wind are known (the coronal holes), the exact acceleration mechanism of the fast solar wind is still not fully understood. An important factor that can improve our understanding is the combination of remote sensing and in-situ measurements.

In order to combine them, it is necessary to accurately identify the source location of the in-situ solar wind with a process called back-mapping. Back-mapping consists mainly of two parts.
The first one is the ballistic mapping where the solar wind radially draws the magnetic field into the Parker Spiral, down to a point in the outer corona.
The second one is the magnetic mapping where the solar wind follows the magnetic field line topology down to the solar surface. The magnetic field in this region is derived from a global model, like the potential field source surface extrapolations (PFSS).

In this study we focus on this back-mapping of the fast solar wind and try to determine all the uncertainties and sources of error that can affect the final location deduced on the solar surface. We compare different models for the ballistic mapping and also for the magnetic mapping and explore which free parameters have the greatest effect in the back-mapped locations.
Finally, we provide an uncertainty estimation for the back-mapped footpoints and compare our results with existing frameworks, like the Connectivity-Tool of IRAP.

How to cite: Koukras, A., Keppens, R., and Dolla, L.: Estimating uncertainties in the back-mapping of the fast solar wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10570, https://doi.org/10.5194/egusphere-egu22-10570, 2022.

The solar wind is an uninterrupted flow of highly ionised plasma that is accelerated in the low solar corona and expands into the interplanetary space. Wind streams develop and are accelerated at different places of the strongly magnetised low solar atmosphere, before propagating through the less magnetically-dominated heliosphere. A wide range of space weather phenomena depend strongly on the structure and geometry of the solar wind flow, as well as on specific properties of the magnetic field that it crosses.
Determining the impacts of solar wind phenomena on Earth or at spacecraft locations require being able to causally link remote observations to in-situ measurements, or to predict Sun-to-spacecraft connectivity with accuracy.
I will discuss the impact of uncertainties in the determination of the magnetic field structure, of the solar wind acceleration profiles and of the rotational state of the corona as well as of mild coronal variablity. I will also highlight undergoing developments that aim at improving these tools, both on a physics-oriented perspective and in the frame of data-driven real-time monitoring.

How to cite: Pinto, R.: On combining background solar wind models and sun-to-spacecraft connectivity in the Parker Solar Probe and Solar Orbiter era, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10573, https://doi.org/10.5194/egusphere-egu22-10573, 2022.

Geomagnetic storms are one of the most important terrestrial space weather events and often commence in association with the arrival of coronal mass ejections (CMEs). When a CME is explosively released into the heliosphere, a shock wave can be formed in front of the dense, supersonic CME material. Thus, the first indication of the arrival of a CME at the Earth is a sudden increase in the global magnetic intensity due to magnetospheric compression by the CME-driven shock. Predictions of the arrival of the shock are a key element in space weather forecasting. Several different variety of methods, including numerical simulations, have been applied to predict the shock arrival time but with mediocre results, with an average uncertainty of ~10 hr. In this study we will use magnetohydrodynamic (MHD) simulations (Wu et al., 2020) to examine a number of input parameters such as the CME initial speed and release time in MHD simulation of CMEs and demonstrate their effect on the shock arrival time. We also explore effects of CME-CME interactions on the propagation of the CME/shock events. The multiple CME events that occurred during 6-29 July 2012 are simulated to highlight the importance of these factors on the prediction of shock arrival time using MHD simulations.

How to cite: Wu, C.-C., Liou, K., and Wood, B.: Magnetohydrodynamic simulation of multiple coronal mass ejection (CME) events: Effects of input parameters and CME-CME interactions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10862, https://doi.org/10.5194/egusphere-egu22-10862, 2022.

EGU22-11208 | Presentations | ST1.10

Studying the spheromak rotation for realistic CME modelling with EUHFORIA and its dependency on initial model parameters 

Ranadeep Sarkar, Jens Pomoell, Emilia Kilpua, Eleanna Asvestari, Nicolas Wijsen, Anwesha Maharana, and Stefaan Poedts

Coronal mass ejections (CMEs) are one of the major sources for space weather disturbances. If the magnetic field inside an Earth-directed CME, or its associated sheath region, has a southward-directed north-south magnetic field component (Bz), then it interacts effectively with the Earth’s magnetosphere, leading to severe geomagnetic storms. Therefore, it is crucial to predict the strength and direction of Bz inside Earth-impacting interplanetary CMEs (ICMEs) in order to forecast their geo-effectiveness. Since the magnetic field of solar eruptions cannot reliably be measured via remote means, and direct continuous measurements of the Earth impacting solar transients are routinely available only very close to our planet, modelling of magnetic properties is paramount. The state-of-the art global heliospheric MHD models typically use the spheromak to characterize the magnetic structure of a CME and simulate its evolution from Sun-to-Earth. However, recent studies (Asvestari et al. 2021) have reported that the spheromak tends to rotate due to its interaction with the ambient medium, posing a great challenge in space weather forecasting.  

In this work, we study the spheromak rotation by modelling a realistic CME event on 2013 April 11 using the “European heliospheric forecasting information asset” (EUHFORIA). We found that when using the default density value in EUHFORIA, the axis of symmetry of the spheromak undergoes approximately 90 degrees of rotation and nearly aligns to the propagation direction of the CME. However, if we constrain the spheromak density using the observational data, we find an order of magnitude higher density value as compared to the default one. Interestingly, the spheromak rotation is observed to be reduced for higher densities. However, we note that the high-density spheromaks undergo significant compression as compared to the low-density ones. Using the observationally constrained density values, we obtain good agreement between the model result and in-situ observation. The simulation is also able to capture the overall magnetic structure of the associated sheath region ahead of the CME flux rope. These results are promising towards forecasting of Bz in near real time inside both ICME and sheath regions.  

This research has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 870405 (EUHFORIA 2.0). 

How to cite: Sarkar, R., Pomoell, J., Kilpua, E., Asvestari, E., Wijsen, N., Maharana, A., and Poedts, S.: Studying the spheromak rotation for realistic CME modelling with EUHFORIA and its dependency on initial model parameters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11208, https://doi.org/10.5194/egusphere-egu22-11208, 2022.

EGU22-12255 | Presentations | ST1.10

Of mesh artefacts and electric fields: the bane of numerical global coronal modelling 

Michaela Brchnelova, Fan Zhang, Barbara Perri, Andrea Lani, and Stefaan Poedts

Global magnetohydrodynamic (MHD) computational fluid dynamics (CFD) simulations have become an important tool for solar weather research. These simulations use solar magnetogram data to compute structures in the solar corona. We have developed one such model based on the COOLFLuiD platform and validated it through comparison with other state-of-art codes and observations (Leitner et al., 2022, submitted). Currently, further physics is added to the solver to move it from ideal MHD to full MHD, such as radiation, coronal heating or conduction. Description of this physics and its results is what is most usually discussed in papers concerning coronal MHD CFD. 

However, physics is only one part of the solution when CFD is used. Actually, it is the numerics that is oftentimes the limiting factor, setting constraints on the accuracy and speed of these solvers. Many different problems can arise due to the finite discretisation of the domain or even due to the solver working with simplified ideal MHD equations instead of the full ones. It is rarely discussed what type of a computational grid should be used depending on the type of the simulations at hand, and it is mentioned even less often what type of errors and inaccuracies such an inappropriate grid type can cause. An unsuitable grid can also cause convergence problems and decrease the speed of the solver considerably (Brchnelova et al., 2022, submitted).

In our work, we investigate the sources of inaccuracies and errors which can compromise the global coronal MHD CFD results. We have observed that due to the large ranges of density magnitudes involved, spurious numerical fluxes can result on mesh cell interfaces when these cells are either highly skewed or the boundaries otherwise non-orthogonal. These spurious fluxes can create local errors of up to 40% in the velocity field in the most deformed portions of the computational grid. Further inaccuracies were observed also in the sharpness of the resulting velocity structures, this time due to artificially generated electric fields during the simulation. 

Thus, in our talk, we will summarize the most important of the issues observed, their causes and potential means of their mitigation. For controlling the errors due to the spurious fluxes while simultaneously optimizing the performance of the solver, we will show a trade-off between different grid topologies and what to expect in the results. Similarly, to enhance the sharpness of the features, it will also be discussed how to mitigate the generation of artificial electric fields via careful formulation of the initial state and boundary conditions.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 870405 (EUHFORIA 2.0) and the ESA project "Heliospheric modelling techniques“ (Contract No. 4000133080/20/NL/CRS).

How to cite: Brchnelova, M., Zhang, F., Perri, B., Lani, A., and Poedts, S.: Of mesh artefacts and electric fields: the bane of numerical global coronal modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12255, https://doi.org/10.5194/egusphere-egu22-12255, 2022.

EGU22-12423 | Presentations | ST1.10

Multi-spacecraft Observations of Interplanetary Coronal Mass Ejections between 0.3 and 2.2 AU: Conjunctions with the Juno Spacecraft 

Emma Davies, Réka Winslow, Camilla Scolini, Robert Forsyth, and Christian Möstl

We present a catalogue of 35 interplanetary coronal mass ejections (ICMEs) observed by the Juno spacecraft during its cruise phase to Jupiter in conjunction with at least one other spacecraft at heliocentric distances near or less than 1 AU (by MESSENGER, Venus Express, Wind, or STEREO). Previous ICME catalogues are used to find conjunctions between spacecraft, and events with magnetic field features that can be matched unambiguously across different spacecraft are selected. We conduct a multi-spacecraft analysis of ICME properties between 0.3 and 2.2 AU: we first investigate the global expansion of ICMEs by tracking the variation in magnetic field strength with increasing heliocentric distance of individual events, finding significant variability in magnetic field relationships for individual events in comparison with statistical trends. With the availability of plasma data at 1 AU, local and global expansion rates are compared; despite following expected trends, the local and global expansion rates are weakly correlated. Finally, for those events with clearly identifiable magnetic flux ropes, we investigate their magnetic complexity as they propagate; we find that 60% of events undergo at least one change in complexity between observations at the innermost spacecraft and Juno. The multi-spacecraft catalogue produced in this study provides a valuable link between ICME observations in the inner heliosphere and beyond 1 AU, contributing to our understanding of ICME evolution in situ. We intend the catalogue to be a useful resource for future studies of ICMEs and space weather research at Earth and other planets.

How to cite: Davies, E., Winslow, R., Scolini, C., Forsyth, R., and Möstl, C.: Multi-spacecraft Observations of Interplanetary Coronal Mass Ejections between 0.3 and 2.2 AU: Conjunctions with the Juno Spacecraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12423, https://doi.org/10.5194/egusphere-egu22-12423, 2022.

EGU22-12553 | Presentations | ST1.10

Revisiting the solar-interplanetary connection of the early August 1972 solar storms 

Consuelo Cid, Elena Saiz, and Manuel Flores-Soriano

The solar storms happened in early August 1972 have been recently described as an example of a space weather event due to its technological impacts. Besides the interest of this event for the space weather community, these storms were extensively analyzed by the scientific community in 1970s and 80s due to their relevance considering the enhanced levels of solar activity and also their interplanetary consequences. The passage of several interplanetary shocks was observed in Pioneers 9 and 10 data and also in Pognoz-1, Prognoz-2 and HEOS-2 data, making this event particularly suitable for the study of the evolution of the solar ejections in the Heliosphere. This work starts reviewing the papers on the interplanetary scenario during this event. Then, we revisit their conclusions considering the scientific advances since that date and finally go ahead in the analysis of the event. 

How to cite: Cid, C., Saiz, E., and Flores-Soriano, M.: Revisiting the solar-interplanetary connection of the early August 1972 solar storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12553, https://doi.org/10.5194/egusphere-egu22-12553, 2022.

EGU22-12699 | Presentations | ST1.10

Post-CME spectroscopic observations during the 2020 total solar eclipse 

Gabriel Muro and Huw Morgan

High-resolution spectral diagnostic data gathered from the total solar eclipse in Neuquen, Argentina provided a rare glimpse of Fe X, XI, XIV ions approximately ~110 minues after the initial plasma eruption that led to a near side coronal mass ejection (CME). The iron ion spectral data represents equilibrium temperatures from 0.9 to 1.9 MK and lower Mg I prominences were also observed. We present a well constrained temperature map of both sides of the corona, where the CME occurred and opposite side which is relatively unperturbed.

A geometric simulation based upon Doppler mapping from our spectrometer, perpendicular motion from other cameras, and LASCO velocity estimates is utilized to find critical CME propagation parameters that extend from the low corona until secondary detection at several solar radii. This data fills the gap of spectral measurements from other space telescopes.

How to cite: Muro, G. and Morgan, H.: Post-CME spectroscopic observations during the 2020 total solar eclipse, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12699, https://doi.org/10.5194/egusphere-egu22-12699, 2022.

EGU22-13167 | Presentations | ST1.10

Improving the Arrival Time Prediction of Coronal Mass Ejections using Magnetohydrodynamic Ensemble Modeling, Heliospheric Imager data and Machine Learning 

Talwinder Singh, Bernard Benson, Syed Raza, Tae Kim, and Nikolai Pogorelov

Coronal mass ejections (CMEs) are responsible for extreme space weather which has many undesirable consequences to our several space-based activities. The arrival time prediction of CMEs is an area of active research. Many methods with varying levels of complexity have been developed to predict CME arrival. However, the mean absolute error in the predictions have remained above 12 hours even with the best methods. In this work, we develop a method for CME arrival time prediction that uses magnetohydrodynamic simulations of a data constrained flux rope-based CME model which is introduced in a data driven solar wind background. We found that for 6 CMEs studied in this work, the mean absolute error in arrival time was 8 hours. We further improved the arrival time predictions by using ensemble modeling and comparing the ensembles with STEREO A and B heliospheric imager data by creating synthetic J-maps from our simulations. A machine learning method called lasso regression was used for this comparison. Our mean absolute error was reduced to 4.1 hours after using this method. This is a significant improvement in the CME arrival time prediction. Thus, our work highlights the importance of using machine learning techniques in combination of other models for improving space weather predictions.

How to cite: Singh, T., Benson, B., Raza, S., Kim, T., and Pogorelov, N.: Improving the Arrival Time Prediction of Coronal Mass Ejections using Magnetohydrodynamic Ensemble Modeling, Heliospheric Imager data and Machine Learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13167, https://doi.org/10.5194/egusphere-egu22-13167, 2022.

EGU22-959 | Presentations | ST1.11

Analysis of the CME and associated gradual SEP event of March 2013 

Antonio Niemela, Nicolas Wijsen, Angels Aran, Luciano Rodriguez, Jasmina Magdalenic, and Stefaan Poedts

We present the study of the propagation of energetic particles through a non-parkerian, data-driven solar wind solution for the event of 15 March 2013. In the study, we employed the recently coupled models EUHFORIA (EUropean Heliospheric FORecasting Information Asset) and PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration). 

An Earth-directed, asymmetric, full halo CME erupted from the Sun on March 15, 2013. An associated GOES M1.1 X-ray flare was observed originating from the active region 11692, reaching its peak intensity at 06:58 UT. Shortly after, at 7:12 UT, a CME was observed by coronagraphs at both STEREO and SOHO/LASCO spacecraft. During March 16, the particle counts at L1 were enhanced, and measurements show different profiles for different energy ranges, with a distinct two-step increase in the lower energy channels lasting for several days. 

The 3D MHD heliospheric solar wind and CME evolution model EUHFORIA was used to simulate this event, with special emphasis on fitting the modeled and observed CME characteristics and signatures at Earth. The energetic particles (SEPs) were simulated with the newly developed solar energetic particle transport model PARADISE. The EUHFORIA simulation results were employed as the time-dependent ambient plasma characteristics. Particle populations with different characteristics were explored with the aim to accurately describe and reproduce the in situ measured particles. Moving sources of particles were incorporated in order to model the CME shock-generated part of the population. The first results of this complex simulation will be shown in this presentation.

 

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Niemela, A., Wijsen, N., Aran, A., Rodriguez, L., Magdalenic, J., and Poedts, S.: Analysis of the CME and associated gradual SEP event of March 2013, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-959, https://doi.org/10.5194/egusphere-egu22-959, 2022.

EGU22-2745 | Presentations | ST1.11

Solar Wind Structures and their Effects on the High-Energy Tail of the Precipitating Energetic Electron Spectrum 

Josephine Salice, Hilde Nesse Tyssøy, Christine Smith-Johnsen, and Eldho Midhun Babu

Medium energy electron (MEE) (>30 keV) precipitation into the Earth's atmosphere is acknowledged as a relevant part of solar forcing as collisions between electrons and atmospheric gasses initiate several chemical reactions which can reduce ozone concentration. Ozone is critically important in the middle atmosphere energy budget as changes in ozone concentration impact temperature and winds. There is an ongoing debate to which extent the existing geomagnetic parameterizations represent a realistic precipitating flux level, especially when considering the high energy tail of MEE (>300 keV). An improved quantification might be achieved by a better understanding of the driving processes of MEE acceleration and precipitation, alongside optimized data handling. In this study, the bounce loss cone fluxes are inferred from MEE precipitation measurements by the Medium Energy Proton and Electron Detector (MEPED) on board the Polar Orbiting Environmental Satellite (POES) and the Meteorological Operational Satellite Program of Europe (METOP) at tens of keV to a couple hundred keV. It investigates MEE precipitation in contexts of different solar wind structures: corotating interaction regions (CIRs) associated with high-speed solar wind streams (HSSs), and coronal mass ejections (CMEs), during an eleven-year period from 2004 – 2014. The objective of this study is to explore general features of the MEE precipitating spectrum in the context of its solar wind driver: the intensity of MEE alongside the intensity and delayed response of its high energy tail.

How to cite: Salice, J., Tyssøy, H. N., Smith-Johnsen, C., and Babu, E. M.: Solar Wind Structures and their Effects on the High-Energy Tail of the Precipitating Energetic Electron Spectrum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2745, https://doi.org/10.5194/egusphere-egu22-2745, 2022.

EGU22-3394 | Presentations | ST1.11

Magnetic Field Line Path Length Variations and Effects on Solar Energetic Particle Transport 

Wirin Sonsrettee, Piyanate Chuychai, Achara Seripienlert, Paisan Tooprakai, Alejandro Sáiz, David Ruffolo, William Henry Matthaeus, and Rohit Chhiber

Modeling of time profiles of solar energetic particle (SEP) observations typically considers transport along a large-scale magnetic field with a fixed path length from the source to the observer.  Chhiber et al. (2021) pointed out that the path length along a turbulent magnetic field line is longer than that along the large scale field, and that the path along the particle gyro-orbit can be substantially longer again; they also considered the global variation in these quantities.  Here we point out that variability in the turbulent field line path length can affect the fits to SEP data and the inferred mean free path and injection profile.  To explore such variability, we perform Monte Carlo simulations in representations of homogeneous 2D MHD + slab turbulence in spherical geometry and trace trajectories of field lines, particle guiding centers, and full particle orbits, considering ion injection from a narrow or wide angular region near the Sun, corresponding to an impulsive or gradual solar event, respectively. We analyze our simulation results in terms of path length statistics within and among square-degree pixels in heliolatitude and heliolongitude at 0.35 and 1 AU from the Sun.  For a given representation of turbulence, there are systematic effects on the path lengths vs. heliolatitude and heliolongitude.  Field line path lengths relate to the fluctuation amplitudes experienced by the field lines, which in turn partly relate to the local topology of 2D turbulence.  Particles from an impulsive event that arrive at a distant angular separation (up to ~25 degrees from the mean field connection) generally have longer path lengths, not because of the angular distance per se but because of strong magnetic fluctuations experienced to drive the guiding field lines to such angular distances and because of the associated scattering of the particles.  We describe the effects of such path length variations on observed time profiles of solar energetic particles, both in terms of path length variability at specific locations and motion of the observer with respect to turbulence topology during the course of the observations.  This research was partially supported by Thailand Science Research and Innovation grant RTA6280002 and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165).  Additional support is acknowledged from the NASA LWS program (NNX17AB79G) and HSR program (80NSSC18K1210 & 80NSSC18K1648).

How to cite: Sonsrettee, W., Chuychai, P., Seripienlert, A., Tooprakai, P., Sáiz, A., Ruffolo, D., Matthaeus, W. H., and Chhiber, R.: Magnetic Field Line Path Length Variations and Effects on Solar Energetic Particle Transport, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3394, https://doi.org/10.5194/egusphere-egu22-3394, 2022.

Simultaneous observations of large Solar Energetic Particle (SEP) events by multiple spacecraft located near 1 AU during solar cycle 24  have shown an east-west asymmetry of the peak intensities of SEPs with respect to the source flare locations. Using the 2D improved Particle Acceleration and Transport in the Heliosphere (iPATH) model, we consider multiple cases with different solar wind speeds and eruption speeds of the Coronal Mass Ejections (CMEs) and fit the longitudinal distributions of time-averaged fluence by Gaussian functions in 8-, 24- and 48-hour respectively. The simulation results are compared with a statistical study of 28 3-spacecraft (SC) events. The east-west asymmetry shows a clear time-dependent and energy-dependent evolution. We suggest that the east-west asymmetry of SEP fluence (and peak intensity) is a consequence of the combined effect of an extended shock acceleration process and the evolution of magnetic field connection to the shock front. Our simulations show that the solar wind speed and the eruption speed of CMEs are essential factors for the east-west fluence asymmetry. 

How to cite: Ding, Z. and Li, G.: Modelling the east-west asymmetry of energetic particle fluence in large solar energetic particle  events using the iPATH model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3603, https://doi.org/10.5194/egusphere-egu22-3603, 2022.

EGU22-5899 | Presentations | ST1.11

Observation-based modelling of the energetic storm particle event of 14 July 2012 

Nicolas Wijsen, Angels Aran, Camilla Scolini, David Lario, Alexandr Afanasiev, Rami Vainio, Jens Pomoell, Blai Sanahuja, and Stefaan Poedts

In this work, we model the energetic storm particle (ESP) event of 14 July 2012 using the energetic particle acceleration and transport model named PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration), together with the solar wind and coronal mass ejection (CME) model named EUHFORIA (EUropean Heliospheric FORcasting Information Asset).  The CME generating the ESP event is simulated by using the spheromak model of EUHFORIA, which approximates the CME’s magnetic field as a linear force-free spheroidal magnetic field. The energetic particles are modelled by injecting a seed population of 50 KeV protons continiously at the CME-driven shock wave. The simulation results illustrate both the capabilities and limitations of the utilised models.  

We find that for energies below 1 MeV, the simulation results agree well with the upstream and downstream components of the ESP event observed by the Advanced Composition Explorer (ACE).  This suggests that these low-energy protons are mainly the result of interplanetary particle acceleration. In the downstream region, the sharp drop in the energetic particle intensities is reproduced at the entry into the following magnetic cloud, illustrating the importance of a magnetised CME model.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Wijsen, N., Aran, A., Scolini, C., Lario, D., Afanasiev, A., Vainio, R., Pomoell, J., Sanahuja, B., and Poedts, S.: Observation-based modelling of the energetic storm particle event of 14 July 2012, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5899, https://doi.org/10.5194/egusphere-egu22-5899, 2022.

EGU22-5984 | Presentations | ST1.11

Preferential Acceleration of Suprathermal Particles at Shocks 

Stefano Livi, Chris Owen, Philippe Louarn, Andrei Fedorov, Ben Alterman, Susan Lepri, Jim Raines, Antoniette Galvin, Lynn Kistler, Frederic Allegrini, Keiichi Ogasawara, Peter Wurz, Roberto Bruno, Raffaella D'Amicis, and Michael Collier

On October/November 2021 the Heavy Ion Sensor onboard Solar Orbiter observed data connected to three interplanetary shock events: Oct 30, Nov 3 and Nov 27. During all three events, the flux of suprathermal particles, defined as those having an energy larger than twice the energy of the solar wind component, showed remarkable intensification. We discuss those changes and specifically how particles of different mass/charge and energy/charge distribution before the shock are affected differently by the interaction with the shock front itself. From these three expampes, it appears that intensifications are stronger for species already having a seed population in the suprathermal regime.

How to cite: Livi, S., Owen, C., Louarn, P., Fedorov, A., Alterman, B., Lepri, S., Raines, J., Galvin, A., Kistler, L., Allegrini, F., Ogasawara, K., Wurz, P., Bruno, R., D'Amicis, R., and Collier, M.: Preferential Acceleration of Suprathermal Particles at Shocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5984, https://doi.org/10.5194/egusphere-egu22-5984, 2022.

EGU22-7106 | Presentations | ST1.11

The medium energy electron direct effect on mesospheric dynamics during a sudden stratospheric warming event in 2010 

Hilde Nesse Tyssøy, Héctor Daniel López Zúñiga, Christine Smith-Johnsens, and Ville Maliniemi

Medium energy electron (MEE) (30-1000 keV) precipitation enhances the production of nitric (NOx) and hydrogen oxides (HOx) throughout the mesosphere, which can destroy ozone (O3) in catalytic reactions. The dynamical effect of the direct mesospheric O3 reduction has long been an outstanding question, partly due to the concurrent feedback from the stratospheric O3  reduction. To overcome this challenge, the Whole Atmosphere Community Climate Model (WACCM) version 6 is applied in the specified dynamics mode for the year 2010, with and without MEE ionization rates. The results demonstrate that MEE ionization rates can modulate temperature, zonal wind and the residual circulation affecting NOx transport. The required fluxes of MEE to impose dynamical changes depend on the dynamical preconditions. During the Northern Hemispheric winter, even weak ionization rates can modulate the mesospheric signal of a sudden stratospheric warming event. The result is a game changer for the understanding of the MEE direct effect.

How to cite: Nesse Tyssøy, H., Zúñiga, H. D. L., Smith-Johnsens, C., and Maliniemi, V.: The medium energy electron direct effect on mesospheric dynamics during a sudden stratospheric warming event in 2010, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7106, https://doi.org/10.5194/egusphere-egu22-7106, 2022.

The propagation of Solar Energetic Particles (SEPs) has been described traditionally by means of a spatially 1D focussed transport approach. However in recent years a number of physical mechanisms that give rise to motion across the mean magnetic field have been studied. These include perpendicular transport associated with turbulence, guiding centre drifts and drift along the heliospheric current sheet. In this presentation such mechanisms will be reviewed and emphasis will be placed on how assumptions and scenarios based on a 1D approach need to be modified when looking at SEP propagation from a 3D perspective. Observables such as time intensity profiles and anisotropies obtained from 3D models will be discussed and compared with observations.

How to cite: Dalla, S.: Role of 3D propagation in shaping Solar Energetic Particle observables, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7635, https://doi.org/10.5194/egusphere-egu22-7635, 2022.

EGU22-8067 | Presentations | ST1.11

Observations of Energetic Electron Substorm Injection Signatures by Cluster and BepiColumbo During an Earth Flyby 

Manuel Grande, Beatriz Sanches-Cano, Rumi Nakamura, Rami Vainio, Yoshizumi Miyoshi, Iannis Dandouras, Rosie Johnson, Philipp Oleynik, Satoko Nakamura, Chris Perry, Patrick Johnson, Juhani Huovelin, Sophie Maguire, and Daniel Heyner

Observations of Energetic Electron Substorm Injection Signatures by Cluster and BepiColumbo During an Earth Flyby

We present an analysis of the energetic electron signatures observed by BepiColumbo and Cluster during the Bepi flyby of Earth on 10 April 2020, as well as other spacecraft. After closest approach, the SIXS instrument on Bepi observed two separate substorm injection fronts, while Cluster RAPID/IES also observed a sequence of energetic electron signatures. Bepi and Cluster were in a particularly favourable configuration during this event, with Bepi moving rapidly radially outward near the nightside equatorial plane while the four Cluster spacecraft cut the same region in a north/south direction in a string of pearls configuration. The coincidence of this favourable geometry with the substorm activity is highly fortuitous and appears to show a complicated sequence of spatially and temporally separated injections and drift echoes.

How to cite: Grande, M., Sanches-Cano, B., Nakamura, R., Vainio, R., Miyoshi, Y., Dandouras, I., Johnson, R., Oleynik, P., Nakamura, S., Perry, C., Johnson, P., Huovelin, J., Maguire, S., and Heyner, D.: Observations of Energetic Electron Substorm Injection Signatures by Cluster and BepiColumbo During an Earth Flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8067, https://doi.org/10.5194/egusphere-egu22-8067, 2022.

EGU22-8518 | Presentations | ST1.11

Energetic particle emission in two solar flares with open magnetic field 

Philippa Browning and Mykola Gordovskyy

Energetic particle populations in the solar corona and in the heliosphere appear to have different characteristics even when produced in the same solar flare. It is not clear what causes this difference: properties of the acceleration region, the large-scale magnetic field configuration in the flare, or particle transport effects, such as scattering. We use a combination of non-linear force-free magnetohydrostatic simulations, magnetohydrodynamic and test-particle modelling to investigate magnetic reconnection, particle acceleration and transport in two solar flares events: an  M-class flare on  June 19th, 2013, and an X-class flare on September 6th, 2011. We show that, although in both events particles are energised at the same locations, the magnetic field structure around the acceleration region results in different characteristics between particle populations precipitating towards the photosphere and those ejected towards the upper corona and the heliosphere. We expect this effect to be ubiquitous when particles are accelerated close to the boundary between open and colsed magnetic fields and, therefore, may be key to solar flares with  substantial particle emission into the heliosphere. Furthermore, this analysis elucidates the mechanisms by which escaping particle populations can be created in flares.

How to cite: Browning, P. and Gordovskyy, M.: Energetic particle emission in two solar flares with open magnetic field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8518, https://doi.org/10.5194/egusphere-egu22-8518, 2022.

EGU22-8953 | Presentations | ST1.11

Quiet Time Suprathermals Across Solar Cycle 23 & 24: Abundances and Spectral Indices 

Benjamin L. Alterman, Mihir I. Desai, Maher Dayeh, Glen M. Mason, and George Ho

We report on the annual variation of quiet-time suprathermal ion composition and spectral properties for C-Fe using Advanced Composition Explorer (ACE)/Ultra-Low Energy Isotope Spectrometer (ULEIS) data over the energy range 0.3 MeV/nuc to 1.28 MeV/nuc from 1998 through 2019. We show that (1) the number of quiet-time hours strongly anti-correlates with the annual Sunspot Number (SSN) at the -0.95 level; (2) a clear ordering of the cross correlation between abundance (normalized to O) and SSN as a function of solar wind mass-per-charge M/Q; (3) the slope of X/O abundance as a function of Fe/C decreases with increasing M/Q; and (4) annual spectral indices γ = 2.5 independent of solar activity and M/Q. We also discuss the trend of annual spectral indices with respect to Oxygen’s spectral index as a function of solar cycle and M/Q. Using our quiet time selection methods, we show that our results are robust against our quiet time selection criterion.

How to cite: Alterman, B. L., Desai, M. I., Dayeh, M., Mason, G. M., and Ho, G.: Quiet Time Suprathermals Across Solar Cycle 23 & 24: Abundances and Spectral Indices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8953, https://doi.org/10.5194/egusphere-egu22-8953, 2022.

EGU22-9873 | Presentations | ST1.11

Evolution of solar accelerated electron beams as a function of distance from the Sun 

Camille Lorfing and Hamish Reid

Solar electrons beams are accelerated in the corona, and can travel out into the solar wind and beyond. These beams of non-thermal electrons evolve as a function of distance from the Sun, interacting with the background plasma and growing Langmuir waves as they propagate. Subsequent radio emission is also seen in the form of type III bursts. Around 1 AU, we detect in-situ electrons up to 10-20 keV together with local Langmuir waves. However, previous studies suggest that higher energy electrons interact with Langmuir waves close to the Sun and so these electrons would not propagate scatter-free. Through beam-plasma structure simulations we study the interactions between these electron beams and the background plasma of the solar corona and the solar wind at different distances from the Sun, up to 130 solar radii. This allows us to determine what is the maximum electron velocity responsible for Langmuir wave production and growth, and consequently which electron energies are affected by wave-particle interactions as a function of distance from the Sun. We also vary the spectral index of the electron velocity distribution α and the electron beam density nbeam to identify what role they play in determining the relevant electron velocities at which wave-particle interactions occur. Understanding the mechanisms driving the change in the maximum electron velocity will permit more accurate predictions in electron onset as well as arrival times, relevant for space weather applications and the understanding of the subsequent emissions at radio and X-ray wavelength. Moreover, our radial predictions can be tested against in-situ electron and plasma measurements from the instruments on-board the Solar Orbiter and Parker Solar Probe spacecrafts.

How to cite: Lorfing, C. and Reid, H.: Evolution of solar accelerated electron beams as a function of distance from the Sun, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9873, https://doi.org/10.5194/egusphere-egu22-9873, 2022.

EGU22-10114 | Presentations | ST1.11

Simultaneous modelling of flare-accelerated electrons at the Sun and in the heliosphere 

Ross Pallister and Natasha Jeffrey

The energy released during a solar flare is efficiently transferred to energetic non-thermal particles, though the exact plasma properties of the acceleration region and the importance of individual acceleration mechanisms is not fully understood. Non-thermal acceleration of electrons in the solar atmosphere is observed from two main sources: in-situ detection of solar energetic electrons (SEEs) in interplanetary space and remote observation of high-energy emission (e.g. X-rays, radio) at the Sun itself. While these two populations are widely studied individually, a common flare-associated acceleration region has not been established. If such a region were to exist, its properties would also need to be determined based on both remote and in-situ observations.

We present preliminary results of a parameter search of the plasma properties and possible acceleration processes in a common solar acceleration region and compare the results of precipitating and escaping electrons. The number density, plasma temperature and the size of the acceleration region itself, as well as properties such as turbulence leading to acceleration, are variable parameters in a transport model code including collisional and non-collisional processes, simulating electrons in the Solar atmosphere and heliosphere. The results of these simulations produce electron time profiles, pitch-angle distributions and energy spectra at the Sun (corona and chromosphere), at 1 AU and other heliospheric locations with which to compare directly with observational data from modern instruments including those mounted on Solar Orbiter.  

The ultimate goal of this study is to model the precipitating and escaping electron populations and compare the resultant properties with observations of solar events where both remote and in-situ observations are available. With this forward modelling approach, we aim to constrain the plasma properties and transport effects present in the solar atmosphere and heliosphere.

How to cite: Pallister, R. and Jeffrey, N.: Simultaneous modelling of flare-accelerated electrons at the Sun and in the heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10114, https://doi.org/10.5194/egusphere-egu22-10114, 2022.

EGU22-11023 | Presentations | ST1.11

Ring Current Electron Precipitation During Storm Events 

Alina Grishina, Yuri Shprits, Michael Wutzig, Hayley Allison, Nikita Aseev, Dedong Wang, and Matyas Szabo-Roberts

The particle flux in the near-Earth environment can increase by orders of magnitude during geomagnetically active periods. This leads to intensification of particle precipitation into Earth’s atmosphere. The process potentially further affects atmospheric chemistry and temperature.

In this research, we concentrate on ring current electrons and investigate precipitation mechanisms on a short time scale using a numerical model based on the Fokker-Planck equation. We focus on understanding which kind of geomagnetic storm leads to stronger electron precipitation. For that, we considered two storms, corotating interaction region (CIR) and coronal mass ejection (CME) driven, and quantified impact on ring current. We validated results using observations made by POES satellite mission, low Earth orbiting meteorological satellites, and Van Allen Probes, and produced a dataset of precipitated fluxes that covers energy range from 1 keV to 1 MeV.

How to cite: Grishina, A., Shprits, Y., Wutzig, M., Allison, H., Aseev, N., Wang, D., and Szabo-Roberts, M.: Ring Current Electron Precipitation During Storm Events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11023, https://doi.org/10.5194/egusphere-egu22-11023, 2022.

EGU22-11283 | Presentations | ST1.11

The Role of Interplanetary Shocks for Accelerating MeV Electrons 

Nasrin Talebpour Sheshvan, Nina Dresing, Rami Vainio, and Alexandr Afanasiev

One source of solar energetic particle (SEP) events are shocks that are driven by fast Coronal Mass Ejections (CMEs). These can accelerate SEPs up to relativistic energies and are attributed to the largest SEP events. Even though the exact role of shocks for accelerating SEP electrons is still under debate, new studies suggest that CME-driven shocks can efficiently accelerate electrons to MeV energies in the vicinity of the Sun.

In this ongoing study, we present STEREO spacecraft observations of potential electron Energetic Storm Particle (ESP) events, characterized by intensity time series that peak at the time of the associated CME-driven shock crossing. We study near-relativistic and relativistic electrons during strong IP shocks between 2007 and 2018, to answer if the shock can actually keep accelerating electrons up to 1 AU distance. We use both, the Solar Electron and Proton Telescope (SEPT) and the High Energy Telescope (HET).

We focus especially on the MeV electron measurements and study if these are real or if the increases during the shock crossing are caused by strong proton contamination in the instrument. Therefore, we investigate the time profiles of the SEP events from the beginning until the crossing of the CME-associated shock and perform a correlation analysis of electron and proton intensities. We also investigate the in-situ plasma and magnetic field measurements at the spacecraft and analyze the energy spectrum of upstream regions of the shocks to shed light on the shock acceleration mechanism.

How to cite: Talebpour Sheshvan, N., Dresing, N., Vainio, R., and Afanasiev, A.: The Role of Interplanetary Shocks for Accelerating MeV Electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11283, https://doi.org/10.5194/egusphere-egu22-11283, 2022.

EGU22-11521 | Presentations | ST1.11

Observation of solar particle events from MGNS experiment onboard BepiColombo mission, HEND experiment onboard Mars Odyssey mission, and also FREND and Liulin-MO experiments onboard TGO mission during July-October 2021 

Alexander Kozyrev, Maxim Litvak, Alexey Malakhov, Igor Mitrofanov, Jordanka Semkova, Rositza Koleva, Victor Benghin, Krasimir Krastev, Yuri Matviichuk, Borislav Tomov, Stephan Maltchev, Nikolay Bankov, Vyacheslav Shurshakov, and Sergey Drobyshev

This report presents the results of observations of Solar Particle Events (SPE) in July-October 2021 that have been simultaneously detected by the MGNS (Mercury Gamma-ray and Neutron Spectrometer) instrument on board the MPO spacecraft of the BepiColombo mission which is currently on a cruise phase to Mercury, as well as by science instruments that are operated in near-Mars orbit: HEND (High Energy Neutron Detector) instrument onboard Mars Odyssey mission, FREND (Fine Resolution Epithermal Neutron Detector) instrument and Liulin-MO dosimeter onboard ExoMars TGO (Trace Gas Orbiter) mission. This location of the spacecrafts, allowed for stereoscopic observation of SPEs, in addition during the period July-October 2021 Mars is on the opposite side of the Sun from Earth, when it is difficult to observe these SPEs by instruments on a near-Earth group of spacecrafts for Solar monitoring. The report will present an analysis of the energy spectra deposition and analysis of time profiles. In particular it shows the Forbush decrease of GCR in effect of the arrival of the dense solar plasma to the SPE observation locations. The MGNS, HEND and FREND instrument developed and manufactured at the Space Research Institute of the Russian Academy of Sciences and are a Russian-made and Russian-funded contribution by the Russian Federal Space Agency (ROSCOSMOS) to the BepiColombo, Mars Odyssey and ExoMars TGO missions, respectively. Liulin-MO has been developed in Space Research and Technology Institute at the Bulgarian Academy of Sciences with participation of Institute of Biomedical Problems of the Russian Academy of Sciences (Moscow) and Institute for Space Research (Moscow).

Acknowledgements

The work in Bulgaria is supported by grant KP-06-Russia 24 for bilateral projects of the National Science Fund of Bulgaria and Russian Foundation for Basic Research.

How to cite: Kozyrev, A., Litvak, M., Malakhov, A., Mitrofanov, I., Semkova, J., Koleva, R., Benghin, V., Krastev, K., Matviichuk, Y., Tomov, B., Maltchev, S., Bankov, N., Shurshakov, V., and Drobyshev, S.: Observation of solar particle events from MGNS experiment onboard BepiColombo mission, HEND experiment onboard Mars Odyssey mission, and also FREND and Liulin-MO experiments onboard TGO mission during July-October 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11521, https://doi.org/10.5194/egusphere-egu22-11521, 2022.

EGU22-11792 | Presentations | ST1.11

What is the flux of low energy electron precipitation in the lower thermosphere? 

Haakon Dahl Eide, Hilde Nesse Tyssøy, Fasil Tesema, and Eldho Midhun Babu

Energetic particle precipitation (EPP) into the atmosphere, lead to chemical reactions producing NOx gases. Auroral electrons deposit their energy at altitudes throughout the upper mesosphere and lower thermosphere. During the winter the EPP-produced NOx gases can survive for months and be transported down to the stratosphere, where it can destroy ozone through catalytic reactions. Studies comparing the NO density estimated by chemistry climate models and observations suggest that the estimation of NO-production by auroral forcing is overestimated during quiet times and underestimated during active time. This study provides an intercomparison of different auroral forcing estimates. We compare fluxes from the Total energy detector (TED) onboard the NOAA Polar Orbiting Environmental Satellites (POES) and Meteorological Operational satellite (MetOp), sensor for precipitating particles (SSJ) from Defense Meteorological spacecraft Program (DMSP), alongside a Kp-driven auroral model. The data over a full year was sorted by the daily Kp and evaluated as function of geomagnetic latitude and magnetic local time. Discrepancies are evaluated in respect to geographical bias, as well as geometric factors of the satellites. Furthermore, the observations are compared to the Kp-driven auroral model.

How to cite: Eide, H. D., Tyssøy, H. N., Tesema, F., and Babu, E. M.: What is the flux of low energy electron precipitation in the lower thermosphere?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11792, https://doi.org/10.5194/egusphere-egu22-11792, 2022.

EGU22-11915 | Presentations | ST1.11

Self-consistent Monte-Carlo modeling of the November 10, 2012 energetic storm particle event 

Alexandr Afanasiev, Nasrin Talebpour Sheshvan, Rami Vainio, Nina Dresing, Domenico Trotta, Heli Hietala, and Seve Nyberg

Fluxes of solar energetic particles (SEPs) are associated with solar flares and coronal/interplanetary shock waves. In the case of shocks, particles are thought to get accelerated to high energies via the diffusive shock acceleration mechanism. In order to be efficient, this mechanism requires an enhanced level of magnetic turbulence in the vicinity of the shock front, in particular, in the so-called foreshock region upstream of the shock. This turbulence enhancement can be produced self-consistently, i.e., by the accelerated particles themselves via streaming instability. This idea underlies the SOLar Particle Acceleration in Coronal Shocks (SOLPACS) Monte-Carlo simulation code, which we developed earlier to simulate acceleration of protons in coronal shocks. In the present work, we apply SOLPACS to model an energetic storm particle (ESP) event measured by the STEREO A spacecraft on November 10, 2012. All but one main SOLPACS input parameters are fixed by the in-situ plasma measurements from the spacecraft. Comparison of a simulated proton energy spectrum at the shock with the observed one then allows us to fix the last simulation input parameter related to efficiency of particle injection to the acceleration process. Subsequent comparison of simulated proton time-intensity profiles in a number of energy channels with the observed ones shows a very good correspondence throughout the upstream region. Our results give support for the quasi-linear formulation of the foreshock. This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Afanasiev, A., Talebpour Sheshvan, N., Vainio, R., Dresing, N., Trotta, D., Hietala, H., and Nyberg, S.: Self-consistent Monte-Carlo modeling of the November 10, 2012 energetic storm particle event, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11915, https://doi.org/10.5194/egusphere-egu22-11915, 2022.

EGU22-11965 | Presentations | ST1.11

Particle Energisation in Collapsing Magnetic Traps 

Kate Mowbray and Thomas Neukirch

Investigating the motion of charged particles in time- and space-dependent electromagnetic fields is central to many areas of space and astrophysical plasmas. Here we present results of studying the energy changes of particle orbits that are trapped in inhomogeneous magnetic fields with rapidly shortening field lines. These so-called collapsing magnetic trap (CMT) models can be useful for explaining the acceleration of particles below the reconnection region in a solar flare. For both 2D and 3D CMT models (e.g. Giuliani et al. 2005; Grady & Neukirch, 2009), betatron acceleration was considered to be the dominant energisation mechanism. We present new results that have been obtained using an improved version of the 3D CMT model by Grady and Neukirch (2009). Our investigations show that a sizeable portion of particle orbits can gain a significant amount of energy that is not explained by the betatron effect. The other mechanism at play appears to be Fermi acceleration at loop tops, where the particle passes through the region of field that is collapsing the most rapidly. 

We show that the particles that experience this effect the most have initial positions that are related to specific regions of the magnetic field model and it is these particle orbits whose energy gains are not adequately explained by betatron acceleration alone. In fact, some particle orbits seem to gain energy almost entirely as a result of this Fermi acceleration. One can also show that for suitable initial conditions the same effect can be seen in the 2D CMT model given by Giuliani et al. (2005). This updated understanding of the systems at play for particle acceleration in a CMT can, for example, inform any changes made to future CMT models by accounting for the large number of particles that see energy gains due to Fermi acceleration. 

Giuliani, P. et al., ApJ 635, 636

Grady, K. & Neukirch, T., A&A 508, 1461 

 

How to cite: Mowbray, K. and Neukirch, T.: Particle Energisation in Collapsing Magnetic Traps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11965, https://doi.org/10.5194/egusphere-egu22-11965, 2022.

EGU22-12111 | Presentations | ST1.11

Determining SEP Event Onset Times and Evaluating Their Uncertainty Using a Poisson CUSUM-Bootstrap Hybrid Method 

Christian Palmroos, Nina Dresing, Jan Gieseler, Rami Vainio, and Eleanna Asvestari

We are examining a new kind of hybrid method for finding SEP (Solar Energetic Particle) event onset times and assessing their uncertainties. Determining these onset times accurately is important because they are needed to relate the in-situ particle measurements to remote-sensing observations of the associated activity phenomena at the Sun. Only by this, can one identify the actual region and acceleration processes that generated the event. Different methods have been used to determine this onset time; however, the most common ones do not provide reasonable uncertainties so far. The method presented here employs a combination of a statistical quality control scheme, the Poisson-CUSUM (cumulative sum) method, and statistical bootstrapping for calculating a distribution of the necessary parameters for the Poisson-CUSUM method.

The CUSUM method is a statistical quality control scheme, used also in many industries, that is designed to give an early warning when the inspected process or variable changes (Page, 1954). Poisson-CUSUM refers to a specific cumulative sum method that assumes that the monitored variable has a Poisson distribution. 

By randomly choosing samples from the particle flux preceding the event, we acquire a distribution of different values for the estimated mean flux and for the standard deviation of the background measurements. These two distributions produce a set of possible onset times via the Poisson-CUSUM method, allowing us to evaluate the uncertainty of an onset time by the precision of our set of candidate onset times, and also to identify the most likely onset time. In addition, we apply the new method to energetic particle observations of the Solar Orbiter spacecraft that come with high energy and time resolution, and perform velocity dispersion analyses. 

 

  • S. PAGE, CONTINUOUS INSPECTION SCHEMES, Biometrika, Volume 41, Issue 1-2, June 1954, Pages 100–115, https://doi.org/10.1093/biomet/41.1-2.100

How to cite: Palmroos, C., Dresing, N., Gieseler, J., Vainio, R., and Asvestari, E.: Determining SEP Event Onset Times and Evaluating Their Uncertainty Using a Poisson CUSUM-Bootstrap Hybrid Method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12111, https://doi.org/10.5194/egusphere-egu22-12111, 2022.

EGU22-12121 | Presentations | ST1.11

Yield function of the DOSimetry TELescope (DOSTEL) count and dose rates aboard an aircraft 

Lisa Romaneehsen, Sönke Burmeister, Bernd Bernd, Konstantin Herbst, Johannes Marquardt, Christoph Senger, and Carsten Wallmann

The Earth is continuously exposed to galactic cosmic rays. The flux of these particles is altered by the magnetized solar wind in the heliosphere and the Earth's magnetic field. If cosmic rays hit the atmosphere they can form secondary particles. The total flux measured within the atmosphere depends on the atmospheric density above the observer. Therefore, the ability of a particle to approach an aircraft depends on its energy, the altitude and position of the aircraft. The latter is described by the so-called cut-off rigidity.
The radiation detector of the detector system NAVIDOS (NAVIgation DOSimetry) is the DOSimetry Telescope (DOSTEL) measuring the count and dose rates in two semiconductor detectors. From 2008 to 2011 two instruments were installed in two aircraft. First we corrected the data for pressure variation by normalizing them to one flight level and determined their dependence on the cut-off rigidity by fitting a Dorman function to the observation. The latter was used to compute the yield function, that describes the ratio of incoming primary cosmic rays, approximated by a force field solution, to the measured count and dose rate for a particular instrument. As for neutron monitors the sensitivity increases substantially above a rigidity of about 1 GV.
We received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 870405. 

How to cite: Romaneehsen, L., Burmeister, S., Bernd, B., Herbst, K., Marquardt, J., Senger, C., and Wallmann, C.: Yield function of the DOSimetry TELescope (DOSTEL) count and dose rates aboard an aircraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12121, https://doi.org/10.5194/egusphere-egu22-12121, 2022.

EGU22-12744 | Presentations | ST1.11

Presenting the AtRIS code as a future tool to investigate the atmospheric impactof SEP events 

Patrick Pohland, Adrian Vogt, Sasha Banjac, Sönke Burmeister, Hanna Giese, Bernd Heber, Konstantin Herbst, Lisa Romaneehsen, and Carsten Wallmann

Within the wider scope of improving Space weather forecast by the EUHFORIA project, we present an updated version of the AtRIS code designed to simulate the count rates and dose deposits of space weather events in the atmosphere. As more and more of modern technological infrastructure is sensitive to radiation exposure space weather forecast can develop into a critical tool to protect it from possible damage. Thereby, AtRIS can be applied  to analyse the impact of past Solar Energetic Particle (SEP) events, complementary to the analysis and comparisons of measurements both at top the  atmosphere and at ground level by e.g. NAVIDOS and DOSTEL. AtRIS thereby is designed as a framework of the well established GEANT4 code, offering   the possibility to implement the atmospheric composition in a layer-wise model. Furthermore, it offers the possibility to select the thickness of the  shielding between 0 and 20 mm of aluminium. Here we will present the physics implemented into AtRIS, its validation, and show preliminary results for  selected past events utilising different layers of shielding.The Kiel team received funding from the European Union’s Horizon 2020 research and  innovation programme under grant agreement No 870405.

How to cite: Pohland, P., Vogt, A., Banjac, S., Burmeister, S., Giese, H., Heber, B., Herbst, K., Romaneehsen, L., and Wallmann, C.: Presenting the AtRIS code as a future tool to investigate the atmospheric impactof SEP events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12744, https://doi.org/10.5194/egusphere-egu22-12744, 2022.

EGU22-3262 | Presentations | ST1.12

Magnetic Flux Transport Identification of Active Reconnection: MMS Observations in the Earth’s Magnetosphere 

Yi Qi, Tak Chu Li, Christopher Russell, Robert Ergun, Ying-dong Jia, and Mark Hubbert

Magnetic reconnection plays an important role in converting energy while modifying the field topology. This process takes place under various plasma conditions during which the transport of magnetic flux is intrinsic. Identifying active magnetic reconnection sites with in-situ observations is challenging. A new technique, Magnetic Flux Transport (MFT) analysis, has been developed recently and proven in numerical simulation for identifying active reconnection efficiently and accurately. In this study we examine the MFT process in 37 previously reported electron diffusion region (EDR)/reconnection-line crossing events at the dayside magnetopause, in the magnetotail and magnetosheath using Magnetospheric Multiscale (MMS) measurements. The co-existing inward and outward MFT flow at the X-point provides a signature that magnetic field lines become disconnected and reconnected. The application of MFT analysis to in-situ observations demonstrates that MFT can successfully identify active reconnection sites under symmetric, asymmetric, and turbulent upstream conditions, providing a also higher rate of successful identification than plasma outflow jets alone.

How to cite: Qi, Y., Li, T. C., Russell, C., Ergun, R., Jia, Y., and Hubbert, M.: Magnetic Flux Transport Identification of Active Reconnection: MMS Observations in the Earth’s Magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3262, https://doi.org/10.5194/egusphere-egu22-3262, 2022.

EGU22-4139 | Presentations | ST1.12

Magnetic topology of actively evolving and passively convecting structures in the turbulent solar wind 

Bogdan Hnat, Sandra Chapman, and Nick Watkins

Multipoint in-situ Cluster observations of the solar wind are analysed to identify the magnetic field line topology and current density of turbulent structures using magnetic field gradient tensor invariants. Identified structures are classified as actively evolving if their magnetic field varies significantly from the force-free configuration. We find that at least 35% of all structures are both actively evolving and carrying the strongest currents, actively dissipating, and heating the plasma. These structures are comprised of 1/5 3D plasmoids, 3/5 flux ropes, and 1/5 3D X-points consistent with magnetic reconnection. Actively evolving and passively advecting structures are both close to log-normally distributed. This provides direct evidence for the significant role of strong turbulence, evolving via magnetic shearing and reconnection, in mediating dissipation and solar wind heating.

How to cite: Hnat, B., Chapman, S., and Watkins, N.: Magnetic topology of actively evolving and passively convecting structures in the turbulent solar wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4139, https://doi.org/10.5194/egusphere-egu22-4139, 2022.

EGU22-7183 | Presentations | ST1.12

Local Cascade and Dissipation: The Coarse Graining approach as a robust tool to investigate Magnetic Reconnection 

Davide Manzini, Fouad Sahraoui, and Francesco Califano

We derive the coarse-graining (CG) equations of  incompressible Hall Magnetohydrodynamics (HMHD) turbulence to investigate the local (in space) energy cascade rate as a function of the filtering scale. 
First, the CG equations are space averaged to obtain the analytical expression of the mean cascade rate. Its application to 3 dimensional (3D) simulations of (weakly compressible) HMHD shows a cascade rate consistent with the value of the mean dissipation rate in the simulations and with the classical estimates based on the "third-order" law.

 The strength of the CG approach is further revealed when considering the local-in-space energy cascade rate which is shown theoretically and numerically to match dissipative processes at a given position x, when both quantities are locally averaged over a small neighboring region (quasi-locality). This result supports the claim that the (quasi-)local cascade rate can provide a reliable estimate of the (quasi-)local energy dissipation, regardless of the nature of the dissipation processes involved.

The new model is further applied to magnetic reconnection sites observed in Hybrid-Vlasov (HVM) simulations and in spacecraft data. The results show the robustness of the new model over standard tools used to highlight energy dissipation processes and particles energization at the X points.  

How to cite: Manzini, D., Sahraoui, F., and Califano, F.: Local Cascade and Dissipation: The Coarse Graining approach as a robust tool to investigate Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7183, https://doi.org/10.5194/egusphere-egu22-7183, 2022.

EGU22-9828 | Presentations | ST1.12 | Highlight

Reconnection and Turbulence: A Qualitative Approach to their Relationship 

Subash Adhikari, Michael A. Shay, Tulasi N. Parashar, William H. Matthaeus, Prayash Sharma Pyakurel, Julia E. Stawarz, and Jonathan P. Eastwood

Over the past few decades, the relationship between turbulence and reconnection has emerged as a subject of interest. For example, various properties of reconnection have been studied in different turbulent environments using plasma simulations. In other approaches, reconnection is studied as a subsidiary process occurring in turbulence. Turbulent features are also studied as consequences of instabilities associated with large scale reconnection. Only recently, we have attempted to answer some of the fundamental questions such as: “What are the turbulent-like features of laminar magnetic reconnection?”, "Is magnetic reconnection fundamentally an energy cascade?" both related to the interplay between reconnection and turbulence. Using 2.5D particle in cell simulations, we have found that laminar magnetic reconnection in a quasi-steady phase exhibits a Kolmogorov-like power spectrum. Most notably, the energy transfer process in magnetic reconnection is also found to be similar to that of a turbulent system suggesting that reconnection involves an energy cascade. The reconnection rate is correlated to both the magnetic energy spectrum in the ion-scales and the cascade of energy. Further, similarities between reconnection and turbulence in terms of the electric field spectrum, their components, and pressure-strain interaction will be highlighted.

How to cite: Adhikari, S., Shay, M. A., Parashar, T. N., Matthaeus, W. H., Sharma Pyakurel, P., Stawarz, J. E., and Eastwood, J. P.: Reconnection and Turbulence: A Qualitative Approach to their Relationship, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9828, https://doi.org/10.5194/egusphere-egu22-9828, 2022.

EGU22-10186 | Presentations | ST1.12

On the short-scale spatial variability of electron inflows in electron-only magnetic reconnection in the turbulent magnetosheath observed by MMS 

Prayash Pyakurel, Tai Phan, Michael Shay, Julia Stawarz, Marit Øieroset, Paul Cassak, Colby Haggerty, James Drake, Tak Chu Li, James Burch, Robert Ergun, Daniel Gershman, Barbara Giles, Roy Torbert, Robert Strangeway, and Christopher Russell

In the Earth’s turbulent magnetosheath downstream of the quasiparallel bow shock region, magnetic reconnection without ion coupling was observed with bi-directional super-Alfvénic electron jets. The lack of ion coupling was attributed to the small-scale sizes of the current sheets. In an electron-only reconnection event that occurred on 26 December 2016, we examine the detailed properties of electron inflows observed by all 4 MMS spacecraft. Even though the farthest MMS probe in the outflow direction from the X-line was no more than 8 electron skin depth, the electron inflows have significant asymmetry and highly variable amplitudes. We compare MMS observations with 2D-kinetic PIC simulation and find that the asymmetry in the inflow stems directly from the tilt of the out-of-plane (guide) magnetic field structure in the reconnection plane, with inflow asymmetry enhanced in the downstream region.

How to cite: Pyakurel, P., Phan, T., Shay, M., Stawarz, J., Øieroset, M., Cassak, P., Haggerty, C., Drake, J., Li, T. C., Burch, J., Ergun, R., Gershman, D., Giles, B., Torbert, R., Strangeway, R., and Russell, C.: On the short-scale spatial variability of electron inflows in electron-only magnetic reconnection in the turbulent magnetosheath observed by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10186, https://doi.org/10.5194/egusphere-egu22-10186, 2022.

EGU22-12164 | Presentations | ST1.12 | Highlight

Turbulent dissipation in weakly-collisional plasmas 

Oreste Pezzi

Understanding the dissipation of energy and the associated heating in weakly collisional turbulent plasmas represents still an unresolved challenge. Here we examine an ensemble of parameters commonly adopted to characterize processes of energy dissipation and conversion in plasmas by means of hybrid Vlasov-Maxwell simulations describing plasma turbulence at sub-proton scales in the whole six-dimensional phase-space.

We make a distinction between ``energy-based'' and ``distribution-function'' based parameters. The first class is related to energy transfer mechanisms, while the second one requires exact knowledge of the particle distribution function in velocity space. All these measures highlight that energy dissipation occurs inhomogeneously and close to regions that are characterized by intense magnetic stresses. The dependence of these processes with respect to the proton β parameter is finally explored. 

How to cite: Pezzi, O.: Turbulent dissipation in weakly-collisional plasmas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12164, https://doi.org/10.5194/egusphere-egu22-12164, 2022.

EGU22-13243 | Presentations | ST1.12

Kinetic-Alfvén-wave turbulence in the low beta limit: role of current sheets and electron Landau damping 

Muni Zhou, Zhuo Liu, and Nuno F. Loureiro

We report analytical and numerical investigations of sub-ion scale turbulence in weakly collisional, low beta plasmas using a hybrid fluid-kinetic model. In the isothermal limit, the same scalings for the energy spectrum and for the eddy anisotropy can be obtained from two distinct approaches: (i) tearing-mediated energy cascade (Loureiro & Boldyrev 2017), and (ii) intermittency corrections, arising from magnetic and density fluctuations concentrated mostly in two-dimensional structures (Boldyrev & Perez 2012). Our numerical results indicate that the latter case is the more plausible in this regime. With the inclusion of electron kinetic physics, the energy spectrum is found to steepen due to electron Landau damping, which is enabled by the local weakening of nonlinearities in current sheets, and yields significant energy dissipation in the velocity space. The use of a Hermite formalism to express the velocity space dependence of the electron distribution function allows us to obtain an analytical, zeroth-order solution for the Hermite moments of the distribution, which is borne out by numerical simulations.

How to cite: Zhou, M., Liu, Z., and Loureiro, N. F.: Kinetic-Alfvén-wave turbulence in the low beta limit: role of current sheets and electron Landau damping, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13243, https://doi.org/10.5194/egusphere-egu22-13243, 2022.

EGU22-1253 | Presentations | PS8.1

Imaging of the Quiet Sun in the Frequency Range of 20-80MHz 

Peijin Zhang, Pietro Zucca, Kamen Kozarev, Chuanbing Wang, and Lofar ssw ksp Team

Radio emission of the quiet Sun is generally believed to be generated from thermal bremsstrahlung emission of the hot solar atmosphere. The imaging properties of the quiet Sun in the microwave band have been well studied, and they fit well to the spectrum of bremsstrahlung emission. In the meter-wave and decameter-wave bands, imaging properties of the quiet Sun have rarely been studied due to the instrumental limitations. In this work, we use the LOw Frequency ARray (LOFAR) telescope to perform high-quality interferometric imaging spectroscopy observations of quiet Sun coronal emission at frequencies below 90~MHz. In these observations of the coronal emission, we achieved unprecedented imaging quality, spatial structures are well resolved. For the first time, we find dark regions with low brightness temperatures. The brightness temperature spectrum of the quiet Sun is obtained and compared with the bremsstrahlung emission of the corona model. 

How to cite: Zhang, P., Zucca, P., Kozarev, K., Wang, C., and Team, L. S. K.: Imaging of the Quiet Sun in the Frequency Range of 20-80MHz, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1253, https://doi.org/10.5194/egusphere-egu22-1253, 2022.

EGU22-2270 | Presentations | PS8.1

Jovian auroral radio source occultation modelling and application to the JUICE science mission planning 

Baptiste Cecconi, Corentin K Louis, Claudio Muñoz Crego, and Claire Vallat

Occultations of the Jovian low frequency radio emissions by the Galilean moons have been observed by the PWS (Plasma Wave Science, Gurnett et al. 1992) instrument of the Galileo spacecraft (Kurth et al. 1997). We use the ExPRES (Exoplanetary and Planetary Radio Emission Simulator) modelling code (Louis et al., 2019), which computes the location of the visible Jovian radio sources depending on the observers location. We show that this code accurately models the temporal occurrence of the occultations in the whole spectral range observed by Galileo/PWS. This validates of the ExPRES code on a new use case. In addition to supporting the analysis of the science observations, the method can be applied for preparing the JUICE moon flyby science operation planning (Cecconi et al. 2021).

Réferences

  • Cecconi, Baptiste, Corentin K Louis, Claudio Muñoz Crego, and Claire Vallat. 2021. Jovian Auroral Radio Source Occultation Modelling and Application to the JUICE Science Mission Planning. PSS 209 (105344): 1–34. https://doi.org/10.1016/j.pss.2021.105344.

  • Gurnett, D. A., W. S. Kurth, R. R. Shaw, A. Roux, R. Gendrin, C. F. Kennel, F. L. Scarf, & S. D. Shawhan (1992). The Galileo Plasma wave investigation. SSRv, 60(1-4), 341-355. https://doi.org/10.1007/BF00216861

  • Kurth, W. S., S. J. Bolton, D. A. Gurnett, & S. Levin (1997). A determination of the source of Jovian hectometric radiation via occultation by Ganymede. GeoRL, 24(10), 1171-1174. https://doi.org/10.1029/97GL00988

  • Louis, C. K., S. L. G. Hess, B. Cecconi, P. Zarka, L. Lamy, S. Aicardi, & A. Loh (2019). ExPRES: an Exoplanetary and Planetary Radio Emissions Simulator. A&A, 627 A30. https://doi.org/10.1051/0004-6361/201935161

     

How to cite: Cecconi, B., Louis, C. K., Muñoz Crego, C., and Vallat, C.: Jovian auroral radio source occultation modelling and application to the JUICE science mission planning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2270, https://doi.org/10.5194/egusphere-egu22-2270, 2022.

EGU22-2920 | Presentations | PS8.1

NenuFAR performances for solar radio observations at high spectral and temporal resolutions 

Carine Briand, Eoin Carley, Baptiste Cecconi, Hamish Reid, and Philippe Zarka

NenuFAR is the tied-array radio instrument recently deployed in France. It is the low-frequency extension of LOFAR. It covers frequencies between 10 and 85 MHz. Its large collecting surface (53000m2 at 25MHz) makes it very sensitive. Spectral and temporal resolution can be very high, respectively, at <5kHz and < 3ms. Such resolution, associated with high sensitivity, is unique at low frequency. Each antenna is composed of two perpendicularly orientated antennas allowing polarization measurements in the four Stokes parameters. Observations were performed between December 16 and 25, 2021, for two hours around the maximum of Sun elevation. Several sunspot groups were present on the solar surface. In terms of flares, the activity was low during the observing time. Still, many Type III bursts were recorded, some with exceptional fine structures as stria or slowly drifting emission, others with a very weak signal. The capabilities of NenuFAR observations with such high resolution and polarimetric modes are presented. At the beginning of the solar cycle 25, the instrument provides unprecedented possibilities to study the solar corona.

How to cite: Briand, C., Carley, E., Cecconi, B., Reid, H., and Zarka, P.: NenuFAR performances for solar radio observations at high spectral and temporal resolutions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2920, https://doi.org/10.5194/egusphere-egu22-2920, 2022.

EGU22-4041 | Presentations | PS8.1

Fine structure of Auroral Kilometric Radiation observed by the Cluster Wideband Receiver 

Ulrich Taubenschuss, Georg Fischer, David Pisa, Ondrej Santolik, and Jan Soucek

Auroral kilometric radiation (AKR) is a strong terrestrial radio emission at frequencies below 1 MHz from source regions at high latitudes along auroral magnetic field lines. Non-thermal electron distributions (e.g. loss-cone or shell distribution) provide the free energy that is converted into electromagnetic energy via the cyclotron maser instability. Improved instrumentation installed on modern spacecraft enabled observations of spectral fine structures in AKR which is composed of discrete emissions seen at narrow frequency bandwidths (<1 kHz) and short time scales below 1 second. We will present data from the Cluster mission, where each of the four satellites is equipped with a Wideband Receiver (WBD). The extensive Cluster-WBD dataset is mostly unexplored to date, despite that a few case studies already analyzed specific AKR fine structures like striations, narrowband emissions drifting up and down in frequency or so-called V- or U-events. We will provide an overview of the large variety of AKR fine structures from Cluster-WBD and introduce a classification scheme.

How to cite: Taubenschuss, U., Fischer, G., Pisa, D., Santolik, O., and Soucek, J.: Fine structure of Auroral Kilometric Radiation observed by the Cluster Wideband Receiver, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4041, https://doi.org/10.5194/egusphere-egu22-4041, 2022.

EGU22-5067 | Presentations | PS8.1

Metric-Decametric Gyrosynchrotron Radio Emission From the Quiet Solar Corona 

Kamen Kozarev, Peijin Zhang, and Pietro Zucca

The radio emission of the quiet Sun in the metric and decametric bands has not been well studied historically due to limitations of existing instruments. It is nominally dominated by thermal brehmsstrahlung of the solar corona, but may also include significant gyrosynchrotron emission, usually assumed to be weak under quiet conditions. In this work, we investigate the expected gyrosynchrotron contribution to solar radio emission in the lowest radio frequencies observable by ground instruments, for different regions of the low and middle corona. We approximate the coronal conditions by a synoptic magnetohydrodynamic (MHD) model. The thermal emission is estimated from a forward model based on the simulated corona. We calculate the expected gyrosynchrotron emission with the Fast Gyrosynchrotron Codes framework by Fleishman and Kuznetsov (2010). The model emissions of different coronal regions are compared with quiet-time imaging observations between 20-90 MHz by the LOw Frequency ARray (LOFAR) radio telescope. The contribution of gyrosynchrotron radiation to low frequency solar radio emission may shed light on effects such as the hitherto unexplained brightness variation observed in decametric coronal hole emission, and help constrain measurements of the coronal magnetic fields. It can also improve our understanding of electron populations in the middle corona and their relation to the formation of the solar wind.

How to cite: Kozarev, K., Zhang, P., and Zucca, P.: Metric-Decametric Gyrosynchrotron Radio Emission From the Quiet Solar Corona, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5067, https://doi.org/10.5194/egusphere-egu22-5067, 2022.

EGU22-8637 | Presentations | PS8.1

Determining the beaming of Io decametric emissions, a remote diagnostic to probe the Io-Jupiter interaction 

Laurent Lamy, Lucas Colomban, Philippe Zarka, Renée Prangé, Manilo Marques, Corentin Louis, William Kurth, Baptiste Cecconi, Julien Girard, Jean Mathias Griessmeier, and Serge Yerin

We investigate the beaming of 11 Io-Jupiter decametric (Io-DAM) emissions observed by Juno/Waves, the Nançay Decameter Array and NenuFAR. Using an up-to-date magnetic field model and three different methods to position the active Io Flux Tube (IFT), we accurately locate the radiosources and determined their emission angle theta from the local magnetic field vector. These methods rely on (i) updated models of the equatorial lead angle, (ii) ultraviolet (UV) images of Jupiter's aurorae from the Hubble Space Telescope simultaneous with radio data and (iii) multi-point radio measurements. The kinetic energy E(e-) of source electrons is then inferred from theta in the framework of the Cyclotron Maser Instability. The precise position of the active IFT obtained from methods (ii) or (iii), when compared to (i), can be used to test of the effective torus plasma density. Simultaneous radio and UV observations reveal that multiple Io-DAM arcs are associated with multiple UV spots and provide the first direct evidence of an Io-DAM arc associated with a trans-hemispheric beam UV spot. Multi-point radio observations alternately probe the Io-DAM sources at various altitudes, times and hemispheres. Overall, theta decreases from ~75-80° to ~70-75° over 10-40 MHz and varies both as a function of frequency (altitude) and time (longitude of Io). Its uncertainty of a few degrees is dominated by that on the longitude of the active IFT. The inferred values of E(e-), also depending on altitude and time, vary between 3 and 16 keV, in agreement with Juno in situ measurements.

How to cite: Lamy, L., Colomban, L., Zarka, P., Prangé, R., Marques, M., Louis, C., Kurth, W., Cecconi, B., Girard, J., Griessmeier, J. M., and Yerin, S.: Determining the beaming of Io decametric emissions, a remote diagnostic to probe the Io-Jupiter interaction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8637, https://doi.org/10.5194/egusphere-egu22-8637, 2022.

EGU22-10052 | Presentations | PS8.1

Ionospheric sounding experiment IONO onboard CubeSat INSPIRE-SAT 7 

Patrick H. M. Galopeau, Mustapha Meftah, Philippe Keckhut, Kévin Grossel, Véronique Rannou, Fabrice Boust, Huy Khang Phan, Vincent Turpaud, Mohammed Y. Boudjada, and Hans U. Eichelberger

INSPIRE-SAT 7 is a French 2 Unit CubeSat weighting approximately 3 kg, very similar to the satellite UVSQ-SAT which was launched on 24 January 2021. Its main purpose is the measurement of the Earth’s radiation budget at the top of the atmosphere and the sounding of the ionosphere. It will orbit at a maximum altitude of 600 km on a Sun-synchronous orbit with a descending node at ~0930 LT. The IONO experiment embarked on the CubeSat is dedicated to the sounding of the Earth’s ionosphere. The latter results from the ionization of the upper atmosphere due to UV radiations and X-rays coming from the Sun. The electron density in the ionosphere depends on the local time, the season, and the solar activity. The propagation of the radio waves is affected by the electron density and also by refraction and reflection phenomena. We consider the following goals for the IONO instrument: improving ionosphere models, in particular the IRI (International Reference Ionosphere); study of the propagation of electromagnetic waves in the ionosphere and the factors which can disturb it (e.g., thunderstorms); analysis of temporal and spatial variability at different scales; study of the coupling between ionosphere and magnetosphere, and the electrical circuit between ionosphere and lithosphere. The observations collected by IONO will be compared to those produced by a VLF-LF antenna network designed for investigating the perturbations of the ionosphere, and the wave propagation, by seismic phenomena.

How to cite: Galopeau, P. H. M., Meftah, M., Keckhut, P., Grossel, K., Rannou, V., Boust, F., Phan, H. K., Turpaud, V., Boudjada, M. Y., and Eichelberger, H. U.: Ionospheric sounding experiment IONO onboard CubeSat INSPIRE-SAT 7, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10052, https://doi.org/10.5194/egusphere-egu22-10052, 2022.

EGU22-10739 | Presentations | PS8.1

Multi-source observations of a coronal mass ejection front from low to middle corona 

Oleg Stepanyuk and Kamen Kozarev

The shape and dynamics of coronal mass ejections (CMEs) varies significantly based on the instrument and wavelength used. This has led to significant debate about the proper definitions of CME/shock fronts, pile-up/compression regions, and cores observed in projection in optically thin vs. optically thin emission. Here we present an observational analysis of the evolving shape and kinematics of a large-scale CME that occurred on May 7, 2021 on the eastern limb of the Sun as seen from 1 au. The eruption was observed continuously, consecutively by the Atmospheric Imaging Assembly (AIA) telescope suite on the Solar Dynamics Observatory (SDO), the ground-based COronal Solar Magnetism Observatory (COSMO) K-coronagraph (K-Cor) on Mauna Loa, and the C2 and C3 telescopes of the Large Angle Solar Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SoHO). We apply the recently developed Wavetrack Python suite for automated detection and tracking of coronal eruptive features to evaluate and compare the evolving shape of the CME front as it propagated from the solar surface out to 30 solar radii.

How to cite: Stepanyuk, O. and Kozarev, K.: Multi-source observations of a coronal mass ejection front from low to middle corona, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10739, https://doi.org/10.5194/egusphere-egu22-10739, 2022.

Magnetic field measurements at middle and higher coronal heights are challenging using conventional techniques with observations at visible or extreme ultra-violet wavelengths. Low radio frequencies are ideal for probing magnetic fields at higher coronal heights. Polarization properties of solar radio emissions are known to be a rich source of information about the emission mechanisms and magnetic fields of the corona. Nonetheless, largely due to technical challenges, precise polarimetric solar observations at low radio frequencies have remained challenging. The degree of polarization of solar radio emission varies dramatically over time, frequency, and also in morphology, depending on the emission mechanism. The radio bursts show a moderate to a high degree of circular polarization, while the quiet sun thermal emissions show a very low degree of circular polarization (<1%). Once feasible, detection of this very low circular polarisation from quiet Sun thermal emission will be an important tool to measure the quiet Sun coronal magnetic field. Simultaneous measurements of linear and circular polarisation from active emissions are important to understand the quasi-longitudinal and quasi-transverse propagation and will be a direct probe of the magnetic field geometry. According to the conventional views, linear polarization the low-frequency solar emission is expected to be wiped out due to large differential Faraday rotation. Hence, the few polarization studies of the low-frequency Sun in the past many decades have concentrated on measuring only the circular polarization. Nonetheless, we will show a few examples of convincing detections of linearly polarized emission from a variety of active solar emissions using observations from the Murchison Widefield Array (MWA). Perhaps the most rewarding, and also challenging, will be the polarimetric observations of faint gyrosynchrotron or thermal emission from the coronal mass ejection (CME) plasma, which will allow us to model the CME plasma parameters unambiguously at higher coronal heights. We have recently developed state-of-the-art polarization calibration and imaging pipeline for snapshot spectro-polarimetric solar imaging to enable the studies enumerated above and more. Here we summarise its current status and showcase some early science results which challenge the conventional wisdom and open a new window of the polarimetric study of the low-frequency radio Sun. While this pipeline is optimized for the MWA, a Square Kilometer Array (SKA) precursor, it can be adapted for the future SKA-Low and other future solar arrays in a straight forward manner.

How to cite: Kansabanik, D., Oberoi, D., and Mondal, S.: Probing coronal magnetic fields using high fidelity spectro-polarimetric low radio frequency observations of the Sun using the Murchison Widefield Array, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10946, https://doi.org/10.5194/egusphere-egu22-10946, 2022.

EGU22-10960 | Presentations | PS8.1

First detailed polarimetric study of type III solar radio bursts with the Murchison Widefield Array 

Soham Dey, Devojyoti Kansabanik, and Divya Oberoi

Type III solar radio bursts form a well known class of active solar emissions and are associated with energetic electron beams propagation outwards through the coronal plasma, and in the process giving rise to their characteristic rapid spectral drifts. Though they have been the subject of a large number of studies since their discovery in the 1950s, the high fidelity and dynamic range spectroscopic snapshot images from the new technology instruments, like the Murchison Widefield Array (MWA) are enabling the exploration of a previously inaccessible part of phase space and leading to the discovery of previously unknown aspects of these well known bursts even in recent times (e.g. Mohan et al., 2019, ApJ, 875). We have now developed a robust and general full Stokes polarization calibration and imaging algorithm optimized for MWA solar observations.. Referred to as “Polarimetry using Automated Imaging Routine for Compact Arrays for the Radio Sun'' (P-AIRCARS; Kansabanik et al., 2022, in prep.), it can deliver full Stokes solar images with leakages on par with usual astronomical radio maps. Here we use this novel capability to carry out a detailed polarimetric study of a type III solar radio burst observed with the MWA. This is, once again, enabling an exploration of new phase space with an exciting discovery potential. Preliminary results show that these type III bursts show presence of linearly polarized emission. While conventional wisdom says that all traces of linear polarization should get washed out due to differential Faraday rotation in the corona, we have convincing reasons to believe that this emission is solar in origin. Here we present the current status of our first detailed polarimetric imaging study oa this  type III radio source. 

How to cite: Dey, S., Kansabanik, D., and Oberoi, D.: First detailed polarimetric study of type III solar radio bursts with the Murchison Widefield Array, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10960, https://doi.org/10.5194/egusphere-egu22-10960, 2022.

EGU22-11001 | Presentations | PS8.1

Exploring Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs): Clues to coronal heating 

Divya Oberoi, Surajit Mondal, Rohit Sharma, Ayan Biswas, Shabbir Bawaji, and Ujjaini Alam

The confluence of the data from the Murchison Widefield Array (MWA) and an imaging pipeline tailored for spectroscopic snapshot images of the Sun at low radio frequencies have led to enormous improvements in the imaging quality of the Sun. Among other science advances, these developments have lowered the detection threshold for weak nonthermal emissions by up to two orders of magnitude as compared to earlier studies, and have enabled our discovery of Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs). Their typical flux densities lie in the range of a few mSFU (1 SFU = 10,000 Jy) and they are found to occur in large numbers all over the quiet Sun regions. In the solar radio images, they appear as compact sources and our estimate of their median duration is limited by the instrumental resolution of 0.5 s. Their spatial distribution and various other properties are consistent with being the radio signatures of coronal nanoflares hypothesized by Parker (1988) to explain coronal heating in the quiet Sun emissions. As steps towards exploring this tantalising possibility of making progress on the coronal heating problem, we have been pursuing multiple projects to improve our ability to detect and characterise WINQSEs. These include attempts to look for WINQSEs in multiple independent datasets; using different independent detection techniques; attempting to characterise their morphologies in radio maps using Artificial Intelligence/Machine Learning based approaches; looking for their counter parts in EUV wavelengths; estimating the energy associated with groups of WINQSEs; and investigation of the spectro-temporal structure of WINQSEs. Here we present the current status of these projects and summarise our learnings from them.

How to cite: Oberoi, D., Mondal, S., Sharma, R., Biswas, A., Bawaji, S., and Alam, U.: Exploring Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs): Clues to coronal heating, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11001, https://doi.org/10.5194/egusphere-egu22-11001, 2022.

EGU22-11460 | Presentations | PS8.1

Understanding the morphology of Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs) 

Shabbir Bawaji, Ujjaini Alam, Surajit Mondal, and Divya Oberoi

The solar coronal heating problem has been around for several decades. While it has been well established that magnetic fields are responsible for transporting the energy from the photosphere to the corona, it has been a challenge to understand the details of the energy dissipation processes. One such process was proposed by Parker, who hypothesized that this dissipation occurs through small scale magnetic reconnections happening throughout the corona. While there are several indications that this mechanism may be active, till date direct observation of these small reconnections have not been possible. Hence searching for indirect signatures of these events is very important. One such probable signature was discovered by Mondal et al. (2020), where they demonstrated the presence of ubiquitous impulsive radio emissions in the solar corona during a very quiet time. These emissions are now named Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs). Due to the potential importance of this discovery and its implications, it is crucial that the detection techniques are improved and that we search for these transients in more datasets to confirm/reject their ubiquitous nature. In this work, we have developed a machine learning (ML) algorithm suitable for identifying and characterising the spatial distribution and morphology  of WINQSEs. For morphological characterisation we use 2D Gaussians which are found to  describe the brightness distribution of the majority of these transients very well. Since WINQSEs are expected to be the radio counterparts of the weak reconnections, we expected them to  be essentially unresolved at an angular resolution of 3.5 arcminutes. We find, however, that most of the WINQSEs are resolved by the instrument, though the distribution of their area is very steep. We hypothesise that while intrinsically unresolved, the area of WINQSEs becomes large due to coronal scattering effects. This then also presents the exciting possibility of using WINQSEs to regularly study the nature of scattering close to the Sun, which currently is only possible during solar radio bursts. Here we present a quick overview of our ML algorithm, along with a summary of our results about the morphological properties of WINQSEs, and explore the possibility of using them to study coronal scattering. 

How to cite: Bawaji, S., Alam, U., Mondal, S., and Oberoi, D.: Understanding the morphology of Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11460, https://doi.org/10.5194/egusphere-egu22-11460, 2022.

EGU22-12087 | Presentations | PS8.1

Generation of fine structures in interplanetary type III radio bursts induced by density inhomogeneities in the ambient plasma 

Immanuel Christopher Jebaraj, Jasmina Magdalenic, Vladimir Krasnoselskikh, and Stefaan Poedts

Solar radio bursts have been studied for over 60 years, however some aspects of their generation and propagation remain to be open questions to the present day. It is generally accepted that majority of solar radio bursts observed in the corona is via the coherent plasma emission mechanism, and a substantial amount of work has been done to support this idea. Fine structures in solar radio bursts can therefore provide important input for understanding the background plasma characteristics.  The presently available advanced ground-based radio imaging spectroscopic techniques (using e.g. LOFAR, MWA, etc.,) and space-based observations (Wind, STEREO A & B, Parker solar probe, Solar Orbiter) provide a unique opportunity to identify, and study fine structures observed in the low corona and interplanetary space.

In this study, we focus on the radio fine structures observed in range of the hecto-kilometric wavelengths that were much less studied than the one in the metric-decametric range. We present for the first time three different types of fine structures observed in interplanetary type III radio bursts (radio signatures of fast electron beams propagating via open and quasi-open magnetic field lines). The presented fine structures show spectral characteristics similar to the striae-like fine structures observed within the type IIIb radio bursts at decametric wavelengths. We employ the probabilistic model for beam-plasma interaction to investigate the role of density inhomogeneities on the generation of the striae elements. The results suggest that there is a good correlation between the width of the striae elements and the scale of density inhomogeneities found in interplanetary space.

How to cite: Jebaraj, I. C., Magdalenic, J., Krasnoselskikh, V., and Poedts, S.: Generation of fine structures in interplanetary type III radio bursts induced by density inhomogeneities in the ambient plasma, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12087, https://doi.org/10.5194/egusphere-egu22-12087, 2022.

EGU22-12239 | Presentations | PS8.1

The angular dependence of spectroscopic radio measurements using multi-spacecraft observations 

Nicolina Chrysaphi and Milan Maksimovic

Injections of non-thermal electrons into the heliosphere often manifest as intense radio emissions, the most common of which are known as Type III solar radio bursts.  The emission frequency of solar radio bursts is closely related to the local plasma frequency of the heliosphere, meaning that they can be used to probe the local conditions of the solar corona and interplanetary space.  However, observations of these radio emissions do not represent the true nature of the radio sources due to the scattering of radio photons.  Such radio-wave scattering is induced by anisotropic density fluctuations in the heliosphere and impacts both the imaging and spectroscopic properties of radio sources in a frequency-dependent manner, where lower frequencies are affected to a larger extent.  Using a significant number of multi-spacecraft observations, including from Solar Orbiter and Parker Solar Probe, we investigate the angular dependence of spectroscopic radio observations due to the presence of anisotropic scattering.  We present an improved estimation of the spectroscopic properties and probe whether the spacecraft position affects the recorded decay times.  Comparing observations and state-of-the-art anisotropic scattering simulations introduces new constraints on the models used to describe heliospheric radio-wave scattering.

How to cite: Chrysaphi, N. and Maksimovic, M.: The angular dependence of spectroscopic radio measurements using multi-spacecraft observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12239, https://doi.org/10.5194/egusphere-egu22-12239, 2022.

EGU22-12890 | Presentations | PS8.1

Status of the Ganymede Laser Altimeter (GALA) for ESA’s JUICE Mission 

Hauke Hussmann, Kay Lingenauber, Reinald Kallenbach, Fabian Lüdicke, Keigo Enya, Nicolas Thomas, Lara Luisa M., Kazuyuki Touhara, Kobayashi Masanori, and Kimura Jun

The Ganymede laser-altimeter (GALA) is one of 10 instruments on ESA’s Jupiter Icy Moons Explorer (JUICE) mission. The scientific goals cover a wide range  from geology, geophysics to geodesy of the icy moons Ganymede, Europa and Callisto. JUICE will explore Jupiter, its magnetosphere and satellites first in orbit around Jupiter before going finally into polar orbit around Ganymede.  GALA is developed under responsibility of the DLR Institute of Planetary Research in collaboration with industry and institutes from Germany, Japan, Switzerland and Spain. GALA has two main objectives: (1) providing Ganymede’s topography from global to local scales (2) determination of Ganymede's tidal variations of surface elevations. GALA is a single-beam laseraltimeter: a laser pulse (1064 nm) is emitted by using a Nd:YAG laser firing at 30 Hz (nominal). After about 3 msec (500 km altitude) the reflection of the pulse from the surface of Ganymede is received by a telescope and transferred to the detector (Avalanche Photo Diode). The signal is digitized and transferred to the range finder module, which determines (a) time of flight (b) pulse shape, and (c) energy of the received pulse. Including information on the spacecraft position and attitude the height of the terrain above a reference surface is determined for each shot from time-of-flight measurements. The GALA flight model was delivered to ESA in August 2021. After several tests on instrument level the integration on the JUICE spacecraft started in September 2021 and first tests were performed successfully in October 2021. With the launch scheduled for 2023, GALA will go through several tests, among them an end-to-end test including laser-receiver measurements. Here we present the instrument's current status with respect hardware integration and regarding the verification of its performance.

How to cite: Hussmann, H., Lingenauber, K., Kallenbach, R., Lüdicke, F., Enya, K., Thomas, N., Luisa M., L., Touhara, K., Masanori, K., and Jun, K.: Status of the Ganymede Laser Altimeter (GALA) for ESA’s JUICE Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12890, https://doi.org/10.5194/egusphere-egu22-12890, 2022.

EGU22-13050 | Presentations | PS8.1

Large Microwave Flare Sources with multi-loop Magnetic Reconnection observed by EOVSA Imaging Spectroscopy 

Shaheda Begum Shaik, Dale E Gary, and Stephen M White

We present the imaging spectroscopy of C-class flare SOL2017-04-04 observed by Expanded Owens Valley Solar Array (EOVSA) to investigate the source morphology and the behavior of the accelerated particles through the low-frequency microwave emission. Unlike the usually observed flare emission that neatly fit the “standard solar model” from a simple, straightforward loop system/arcade, we report that the low-frequency sources have shown an extended emission over the flaring active region and are spatially almost ten times as large as the other associated observations. These sources cannot be entirely explained by a standard two-dimensional model but with a “three-dimensional loop-loop interaction” scenario as observed from the contributions of multiple loop systems with different sizes. This scenario leads to observational evidence for a more realistic flare model consisting of a multi-polar magnetic field configuration with the accelerated particles having large access to travel over the flaring region, where other wavelength emissions are almost invisible. Thus, the study highlights the diagnostic potential of the observed microwave frequencies through which the physical conditions of the secondary emission observed in the low-frequency sources are presented.

How to cite: Shaik, S. B., Gary, D. E., and White, S. M.: Large Microwave Flare Sources with multi-loop Magnetic Reconnection observed by EOVSA Imaging Spectroscopy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13050, https://doi.org/10.5194/egusphere-egu22-13050, 2022.

ST2 – Magnetosphere

EGU22-91 | Presentations | NP4.1

The role of teleconnections in complex climate network 

Ruby Saha

A complex network provides a robust framework to statistically investigate the topology of local and long-range connections, i.e., teleconnections in climate dynamics. The Climate network is constructed from meteorological data set using the linear Pearson correlation coefficient to measure similarity between two regions. Long-range teleconnections connect remote geographical sites and are crucial for climate networks. In this study, we discuss that during El Ni\~no Southern Oscillation onset, the teleconnections pattern changes according to the episode's strength. The long-range teleconnections are significant and responsible for the episodes' extremum ONI attained gradually after onset. We quantify the betweenness centrality measurement and note that the teleconnection distribution pattern and the betweenness measurements fit well.

How to cite: Saha, R.: The role of teleconnections in complex climate network, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-91, https://doi.org/10.5194/egusphere-egu22-91, 2022.

EGU22-1831 | Presentations | NP4.1

Quantifying space-weather events using dynamical network analysis of Pc waves with global ground based magnetometers. 

Shahbaz Chaudhry, Sandra Chapman, Jesper Gjerloev, Ciaran Beggan, and Alan Thompson

Geomagnetic storms can impact technological systems, on the ground and in space, including damage to satellites and power blackouts. Their impact on ground systems such as power grids depends upon the spatio-temporal extent and time-evolution of the ground magnetic perturbation driven by the storm.

Pc waves are Alfven wave resonances of closed magnetospheric field lines and are ubiquitous in the inner magnetosphere. They have been extensively studied, in particular since  Pc wave power tracks the onset and evolution of geomagnetic storms.  We study the spatial and temporal evolution of Pc waves with a network analysis of the 100+ ground-based magnetometer stations collated by the SuperMAG collaboration with a single time-base and calibration. 

Network-based analysis of 1 min cadence SuperMAG magnetometer data has been applied to the dynamics of substorm current systems (Dods et al. JGR 2015, Orr et al. GRL 2019) and the magnetospheric response to IMF turnings (Dods et al. JGR 2017). It has the potential to capture the full spatio-temporal response with a few time-dependent network parameters. Now, with the availability of 1 sec data across the entire SuperMAG network we are able for the first time to apply network analysis globally to resolve both the spatial and temporal correlation patterns of the ground signature of Pc wave activity as a geomagnetic storm evolves. We focus on Pc2 (5-10s period) and Pc3 (10-45s period) wave bands. We obtain the time-varying global Pc wave dynamical network over individual space weather events.

To construct the networks we sample each magnetometer time series with a moving window in the time domain (20 times Pc period range) and then band-pass filter each magnetometer station time-series to obtain Pc2 and Pc3 waveforms. We then compute the cross correlation (TLXC) between all stations for each Pc band. Modelling is used to determine a threshold of significant TLXC above which a pair of stations are connected in the network. The TLXC as a function of lag is tested against a criterion for sinusoidal waveforms and then used to calculate the phase difference. The connections with a TLXC peak at non zero lag form a directed network which characterizes propagation or information flow. The connections at TLXC lag peak close to zero form am undirected network which characterizes a response which is globally instantaneously coherent.

We apply this network analysis to isolated geomagnetic storms. We find that the network connectivity does not simply track Pc wave power, it therefore contains additional information. Geographically short range connections are prevalent at all times, the storm onset marks a transition to a network which has both enhancement of geographically short-range connections, and the growth of geographically long range, global scale, connections extending spatially over a region exceeding 9h MLT. These global scale connections, indicating globally coherent Pc wave response are prevalent throughout the storm with considerable (within a few time windows) variation. The stations are not uniformly distributed spatially. Therefore, we distinguish between long range connections to avoid introducing spatial correlation. 

How to cite: Chaudhry, S., Chapman, S., Gjerloev, J., Beggan, C., and Thompson, A.: Quantifying space-weather events using dynamical network analysis of Pc waves with global ground based magnetometers., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1831, https://doi.org/10.5194/egusphere-egu22-1831, 2022.

EGU22-2014 | Presentations | NP4.1

OBS noise reduction using music information retrieval algorithms 

Zahra Zali, Theresa Rein, Frank Krüger, Matthias Ohrnberger, and Frank Scherbaum

Since the ocean covers 71% of the Earth’s surface, records from ocean bottom seismometers (OBS) are essential for investigating the whole Earth’s structure. However, data from ocean bottom recordings are commonly difficult to analyze due to the high noise level especially on the horizontal components. In addition, signals of seismological interest such as earthquake recordings at teleseismic distances, are masked by the oceanic noises. Therefore, noise reduction of OBS data is an important task required for the analysis of OBS records. Different approaches have been suggested in previous studies to remove noise from vertical components successfully, however, noise reduction on records of horizontal components remained problematic. Here we introduce a method, which is based on harmonic-percussive separation (HPS) algorithms used in Zali et al., (2021) that is able to separate long-lasting narrowband signals from broadband transients in the OBS records. In the context of OBS noise reduction using HPS algorithms, percussive components correspond to earthquake signals and harmonic components correspond to noise signals. OBS noises with narrowband horizontal structures in the short time Fourier transform (STFT) are readily distinguishable from transient, short-duration seismic events with vertical exhibitions in the STFT spectrogram. Through HPS algorithms we try to separate horizontal structures from vertical structures in the STFT spectrograms. Using this method we can reduce OBS noises from both vertical and horizontal components, retrieve clearer broadband earthquake waveforms and increase the earthquake signal to noise ratio. The applicability of the method is checked through tests on synthetic and real data.

How to cite: Zali, Z., Rein, T., Krüger, F., Ohrnberger, M., and Scherbaum, F.: OBS noise reduction using music information retrieval algorithms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2014, https://doi.org/10.5194/egusphere-egu22-2014, 2022.

EGU22-2097 | Presentations | NP4.1 | Highlight

Medium- to long-term forecast of sea surface temperature using EEMD-STEOF-LSTM hybrid model 

Rixu Hao, Yuxin Zhao, Xiong Deng, Di Zhou, Dequan Yang, and Xin Jiang

Sea surface temperature (SST) is a vitally important variable of the global ocean, which can profoundly affect the climate and marine ecosystems. The field of forecasting oceanic variables has traditionally relied on numerical models, which effectively consider the discretization of the dynamical and physical oceanic equations. However, numerical models suffer from many limitations such as short timeliness, complex physical processes, and excessive calculation. Furthermore, existing machine learning has been proved to be able to capture spatial and temporal information independently without these limitations, but the previous research on multi-scale feature extraction and evolutionary forecast under spatiotemporal integration is still inadequate. To fill this gap, a multi-scale spatiotemporal forecast model is developed combining ensemble empirical mode decomposition (EEMD) and spatiotemporal empirical orthogonal function (STEOF) with long short-term memory (LSTM), which is referred to as EEMD-STEOF-LSTM. Specifically, the EEMD is applied for adaptive multi-scale analysis; the STEOF is adopted to decompose the spatiotemporal processes of different scales into terms of a sum of products of spatiotemporal basis functions along with corresponding coefficients, which captures the evolution of spatial and temporal processes simultaneously; and the LSTM is employed to achieve medium- to long-term forecast of STEOF-derived spatiotemporal coefficients. A case study of the daily average of SST in the South China Sea shows that the proposed hybrid EEMD-STEOF-LSTM model consistently outperforms the optimal climatic normal (OCN), STEOF, and STEOF-LSTM, which can accurately forecast the characteristics of oceanic eddies. Statistical analysis of the case study demonstrates that this model has great potential for practical applications in medium- to long-term forecast of oceanic variables.

How to cite: Hao, R., Zhao, Y., Deng, X., Zhou, D., Yang, D., and Jiang, X.: Medium- to long-term forecast of sea surface temperature using EEMD-STEOF-LSTM hybrid model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2097, https://doi.org/10.5194/egusphere-egu22-2097, 2022.

In this presentation, we introduce the IMFogram method ( pronounced like "infogram" ), which is a new, fast, local, and reliable time-frequency representation (TFR) method for nonstationary signals. This technique is based on the Intrinsic Mode Functions (IMFs) decomposition produced by a decomposition method, like the Empirical Mode Decomposition-based techniques, Iterative Filtering-based algorithms, or any equivalent method developed so far. We present the mathematical properties of the IMFogram, and show the proof that this method is a generalization of the Spectrogram. We conclude the presentation with some applications, as well as a comparison of its performance with other existing TFR techniques.

How to cite: Cicone, A.: The IMFogram: a new time-frequency representation algorithm for nonstationary signals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2560, https://doi.org/10.5194/egusphere-egu22-2560, 2022.

EGU22-2922 | Presentations | NP4.1

Constraining the uncertainty in CO2 seasonal cycle metrics by residual bootstrapping. 

Theertha Kariyathan, Wouter Peters, Julia Marshall, Ana Bastos, and Markus Reichstein

The analysis of long, high-quality time series of atmospheric greenhouse gas measurements helps to quantify their seasonal to interannual variations and impact on global climate. These discrete measurement records contain, however, gaps and at times noisy data, influenced by local fluxes or synoptic scale events, hence appropriate filtering and curve-fitting techniques are often used to smooth and gap-fill the atmospheric time series. Previous studies have shown that there is an inherent uncertainty associated with curve-fitting processes which introduces biases based on the choice of mathematical method used for data processing and can lead to scientific misinterpretation of the signal. Further the uncertainties in curve-fitting can be propagated onto the metrics estimated from the fitted curve that could significantly influence the quantification of the metrics and their interpretations. In this context we present a novel-methodology for constraining the uncertainty arising from fitting a smooth curve to the CO2 dry air mole fraction time-series, and propagate this uncertainty onto commonly used metrics to study the seasonal cycle of CO2. We generate an ensemble of fifitted curves from the data using residual bootstrap sampling with loess-fitted residuals, that is representative of the inherent uncertainty in applying the curve-fitting method to the discrete data. The spread of the selected CO2 seasonal cycle metrics across bootstrap time-series provides an estimate of the inherent uncertainty in curve fitting to the discrete data. Further we show that the approach can be extended to other curve-fitting methods by generating multiple bootstrap samples by resampling residuals obtained from processing the data using the widely used CCGCRV filtering method by the atmospheric greenhouse gas measurement community.

How to cite: Kariyathan, T., Peters, W., Marshall, J., Bastos, A., and Reichstein, M.: Constraining the uncertainty in CO2 seasonal cycle metrics by residual bootstrapping., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2922, https://doi.org/10.5194/egusphere-egu22-2922, 2022.

EGU22-4795 | Presentations | NP4.1

Robust Causal Inference for Irregularly Sampled Time Series: Applications in Climate and Paleoclimate Data Analysis 

Aditi Kathpalia, Pouya Manshour, and Milan Paluš

To predict and determine the major drivers of climate has become even more important now as climate change poses a big challenge to humankind and our planet earth. Different studies employ either correlation, causality methods or modelling approaches to study the interaction between climate and climate forcing variables (anthropogenic or natural). This includes the study of interaction between global surface temperatures and CO2; rainfall in different locations and El Niño–Southern Oscillation (ENSO) phenomena. The results produced by different studies have been found to be different and debatable, presenting an ambiguous situation. In this work, we develop and apply a novel robust causality estimation technique for time-series data (to estimate causal influence between given observables), that can help to resolve the ambiguity. The discrepancy in existing results arises due to challenges with the acquired data and limitations of the causal inference/ modelling approaches. Our novel approach combines the use of a recently proposed causality method, Compression-Complexity Causality (CCC) [1], and Ordinal/ Permutation pattern-based coding [2]. CCC estimates have been shown to be robust for bivariate systems with low temporal resolution, missing samples, long-term memory and finite length data [1]. The use of ordinal patterns helps to extend bivariate CCC to the multivariate case by capturing the multidimensional dynamics of the given variables’ systems in the symbolic temporal sequence of a single variable. This methodology is tested on dynamical systems data which are short in length and have been corrupted with missing samples or subsampled to different levels. The superior performance of ‘Permutation CCC’ on such data relative to other causality estimation methods, strengthens our trust in the method. We apply the method to study the interaction between CO2-temperature recordings on three different time scales, CH4-temperature on the paleoclimate scale, ENSO-South Asian monsoon on monthly and yearly time scales, North Atlantic Oscillation-surface temperature on daily and monthly time scales. These datasets are either short in length, have been sampled irregularly, have missing samples or have a combination of the above factors. Our results are interesting, which validate some existing studies while contradicting others. In addition, the development of the novel permutation-CCC approach opens the possibility of its application for making useful inferences on other challenging climate datasets.


This study is supported by the Czech Science Foundation, Project No.~GA19-16066S and by the Czech Academy of Sciences, Praemium Academiae awarded to M. Paluš.


References:
[1] Kathpalia, A., & Nagaraj, N. (2019). Data-based intervention approach for Complexity-Causality measure. PeerJ Computer Science, 5, e196.
[2] Bandt, C., & Pompe, B. (2002). Permutation entropy: a natural complexity measure for time series. Physical review letters, 88(17), 174102.

How to cite: Kathpalia, A., Manshour, P., and Paluš, M.: Robust Causal Inference for Irregularly Sampled Time Series: Applications in Climate and Paleoclimate Data Analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4795, https://doi.org/10.5194/egusphere-egu22-4795, 2022.

Rainfall time series prediction is crucial for geoscientific system monitoring, but it is challenging and complex due to the extreme variability of rainfall. In order to improve prediction accuracy, a hybrid deep learning model (VMD-RNN) was proposed. In this study, variational mode decomposition (VMD) is first applied to decompose the original rainfall time series into several sub-sequences according to the frequency domain. Following that, different recurrent neural network (RNN) models are utilized to predict individual sub-sequences and the final prediction is reconstructed by summing the prediction results of sub-sequences. These RNN models are long short-term memory (LSTM), gated recurrent unit (GRU), bidirectional LSTM (BiLSTM) and bidirectional GRU (BiGRU), which are optimal for sequence prediction. The root mean square error (RMSE) of the predicted performance is then used to select the ideal RNN model for each sub-sequences. In addition to RMSE, the framework of universal multifractal (UM) is also introduced to evaluate prediction performances, which enables to characterize the extreme variability of predicted rainfall time series. The study employed two rainfall datasets from 2001 to 2020 in Paris, with daily and hourly resolutions. The results show that, when compared to directly predicting the original time series, the proposed hybrid VMD-RNN model improves prediction of high or extreme values for the daily dataset, but does not significantly enhance the prediction of zero or low values. Additionally, the VMD-RNN model also outperforms existing deep learning models without decomposition on the hourly dataset when evaluated with the help of RMSE, while universal multifractal analyses point out limitations. 

How to cite: Zhou, H., Schertzer, D., and Tchiguirinskaia, I.: Combining variational mode decomposition and recurrent neural network to predict rainfall time series and evaluating prediction performance by universal multifractals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6014, https://doi.org/10.5194/egusphere-egu22-6014, 2022.

EGU22-6281 | Presentations | NP4.1

Application of information theoretical measures for improved machine learning modelling of the outer radiation belt 

Constantinos Papadimitriou, Georgios Balasis, Ioannis A. Daglis, and Simon Wing

In the past ten years Artificial Neural Networks (ANN) and other machine learning methods have been used in a wide range of models and predictive systems, to capture and even predict the onset and evolution of various types of phenomena. These applications typically require large datasets, composed of many variables and parameters, the number of which can often make the analysis cumbersome and prohibitively time consuming, especially when the interplay of all these parameters is taken into consideration. Thankfully, Information-Theoretical measures can be used to not only reduce the dimensionality of the input space of such a system, but also improve its efficiency. In this work, we present such a case, where differential electron fluxes from the Magnetic Electron Ion Spectrometer (MagEIS) on board the Van Allen Probes satellites are modelled by a simple ANN, using solar wind parameters and geomagnetic activity indices as inputs, and illustrate how the proper use of Information Theory measures can improve the efficiency of the model by minimizing the number of input parameters and shifting them with respect to time, to their proper time-lagged versions.

How to cite: Papadimitriou, C., Balasis, G., Daglis, I. A., and Wing, S.: Application of information theoretical measures for improved machine learning modelling of the outer radiation belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6281, https://doi.org/10.5194/egusphere-egu22-6281, 2022.

EGU22-7256 | Presentations | NP4.1

Identifying patterns of teleconnections, a curvature-based network analysis 

Jakob Schlör, Felix M. Strnad, Christian Fröhlich, and Bedartha Goswami

Representing spatio-temporal climate variables as complex networks allows uncovering nontrivial structure in the data. Although various tools for detecting communities in climate networks have been used to group nodes (spatial locations) with similar climatic conditions, we are often interested in identifying important links between communities. Of particular interest are methods to detect teleconnections, i.e. links over large spatial distances mitigated by atmospheric processes.

We propose to use a recently developed network measure based on Ricci-curvature to visualize teleconnections in climate networks. Ricci-curvature allows to distinguish between- and within-community links in networks. Applied to networks constructed from surface temperature anomalies we show that Ricci-curvature separates spatial scales. We use Ricci-curvature to study differences in global teleconnection patterns of different types of El Niño events, namely the Eastern Pacific (EP) and Central Pacific (CP) types. Our method reveals a global picture of teleconnection patterns, showing confinement of teleconnections to the tropics under EP conditions but showing teleconnections to the tropics, Northern and Southern Hemisphere under CP conditions. The obtained teleconnections corroborate previously reported impacts of EP and CP.
Our results suggest that Ricci-curvature is a promising visual-analytics-tool to study the topology of climate systems with potential applications across observational and model data.

How to cite: Schlör, J., Strnad, F. M., Fröhlich, C., and Goswami, B.: Identifying patterns of teleconnections, a curvature-based network analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7256, https://doi.org/10.5194/egusphere-egu22-7256, 2022.

EGU22-8399 | Presentations | NP4.1

Using neural networks to detect coastal hydrodynamic phenomena in high-resolution tide gauge data 

Felix Soltau, Sebastian Niehüser, and Jürgen Jensen

Tide gauges are exposed to various kinds of influences that are able to affect water level measurements significantly and lead to time series containing different phenomena and artefacts. These influences can be natural or anthropogenic, while both lead to actual changes of the water level. Opposed to that, technical malfunction of measuring devices as another kind of influence causes non-physical water level data. Both actual and non-physical data need to be detected and classified consistently, and possibly corrected to enable the supply of adequate water level information. However, there is no automatically working detection algorithm yet. Only obvious or frequent technical malfunctions like gaps can be detected automatically but have to be corrected manually by trained staff. Consequently, there is no consistently defined data pre-processing before, for example, statistical analyses are performed or water level information for navigation is passed on.

In the research project DePArT*, we focus on detecting natural phenomena like standing waves, meteotsunamis, or inland flood events as well as anthropogenic artefacts like operating storm surge barriers and sluices in water level time series containing data every minute. Therefore, we train artificial neural networks (ANNs) using water level sequences of phenomena and artefacts as well as redundant data to recognize them in other data sets. We use convolutional neural networks (CNNs) as they already have been successfully conducted in, for example, object detection or speech and language processing (Gu et al., 2018). However, CNNs need to be trained with high numbers of sample sequences. Hence, as a next step the idea is to synthesize rarely observed phenomena and artefacts to gain enough training data. The trained CNNs can then be used to detect unnoticed phenomena and artefacts in past and recent time series. Depending on sequence characteristics and the results of synthesizing, we will possibly be able to detect certain events as they occur and therefore provide pre-checked water level information in real time.

In a later stage of this study, we will implement the developed algorithms in an operational test mode while cooperating closely with the officials to benefit from the mutual feedback. In this way, the study contributes to a future consistent pre-processing and helps to increase the quality of water level data. Moreover, the results are able to reduce uncertainties from the measuring process and improve further calculations based on these data.

* DePArT (Detektion von küstenhydrologischen Phänomenen und Artefakten in minütlichen Tidepegeldaten; engl. Detection of coastal hydrological phenomena and artefacts in minute-by-minute tide gauge data) is a research project, funded by the German Federal Ministry of Education and Research (BMBF) through the project management of Projektträger Jülich PTJ under the grant number 03KIS133.

Gu, Wang, Kuen, Ma, Shahroudy, Shuai, Liu, Wang, Wang, Cai, Chen (2018): Recent advances in convolutional neural networks. In: Pattern Recognition, Vol. 77, Pages 354–377. https://doi.org/10.1016/j.patcog.2017.10.013

How to cite: Soltau, F., Niehüser, S., and Jensen, J.: Using neural networks to detect coastal hydrodynamic phenomena in high-resolution tide gauge data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8399, https://doi.org/10.5194/egusphere-egu22-8399, 2022.

EGU22-8899 | Presentations | NP4.1

Body wave extraction by using sparsity-promoting time-frequency filtering 

Bahare Imanibadrbani, Hamzeh Mohammadigheymasi, Ahmad Sadidkhouy, Rui Fernandes, Ali Gholami, and Martin Schimmel

Different phases of seismic waves generated by earthquakes carry considerable information about the subsurface structures as they propagate within the earth. Depending on the scope and objective of an investigation, various types of seismic phases are studied. Studying surface waves image shallow and large-scale subsurface features, while body waves provide high-resolution images at higher depths, which is otherwise impossible to be resolved by surface waves. The most challenging aspect of studying body waves is extracting low-amplitude P and S phases predominantly masked by high amplitude and low attenuation surface waves overlapping in time and frequency. Although body waves generally contain higher frequencies than surface waves, the overlapping frequency spectrum of body and surface waves limits the application of elementary signal processing methods such as conventional filtering. Advanced signal processing tools are required to work around this problem. Recently the Sparsity-Promoting Time-Frequency Filtering (SP-TFF) method was developed as a signal processing tool for discriminating between different phases of seismic waves based on their high-resolution polarization information in the Time-Frequency (TF)-domain (Mohammadigheymasi et al., 2022). The SP-TFF extracts different phases of seismic waves by incorporating this information and utilizing a combination of amplitude, directivity, and rectilinearity filters. This study implements SP-TFF by properly defining a filter combination set for specific extraction of body waves masked by high-amplitude surface waves. Synthetic and real data examinations for the source mechanism of the  Mw=7.5 earthquake that occurred in November 2021 in Northern Peru and recorded by 58 stations of the United States National Seismic Network (USNSN) is conducted. The results show the remarkable performance of SP-TFF extracting P and SV phases on the vertical and radial components and SH phase on the transverse component masked by high amplitude Rayleigh and Love waves, respectively. A range of S/N levels is tested, indicating the algorithm’s robustness at different noise levels. This research contributes to the FCT-funded SHAZAM (Ref. PTDC/CTA-GEO/31475/2017) and IDL (Ref. FCT/UIDB/50019/2020) projects. It also uses computational resources provided by C4G (Collaboratory for Geosciences) (Ref. PINFRA/22151/2016).

REFERENCE
Mohammadigheymasi, H., P. Crocker, M. Fathi, E. Almeida, G. Silveira, A. Gholami, and M. Schimmel, 2022, Sparsity-promoting approach to polarization analysis of seismic signals in the time-frequency domain: IEEE Transactions on Geoscience and Remote Sensing, 1–1.

How to cite: Imanibadrbani, B., Mohammadigheymasi, H., Sadidkhouy, A., Fernandes, R., Gholami, A., and Schimmel, M.: Body wave extraction by using sparsity-promoting time-frequency filtering, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8899, https://doi.org/10.5194/egusphere-egu22-8899, 2022.

EGU22-9626 | Presentations | NP4.1

A Recurrence Flow based Approach to Attractor Reconstruction 

Tobias Braun, K. Hauke Kraemer, and Norbert Marwan

In the study of nonlinear observational time series, reconstructing the system’s state space represents the basis for many widely-used analyses. From the perspective of dynamical system’s theory, Taken’s theorem states that under benign conditions, the reconstructed state space preserves the most fundamental properties of the real, unknown system’s attractor. Through many applications, time delay embedding (TDE) has established itself as the most popular approach for state space reconstruction1. However, standard TDE cannot account for multiscale properties of the system and many of the more sophisticated approaches either require heuristic choice for a high number of parameters, fail when the signals are corrupted by noise or obstruct analysis due to their very high complexity.

We present a novel semi-automated, recurrence based method for the problem of attractor reconstruction. The proposed method is based on recurrence plots (RPs), a computationally simple yet effective 2D-representation of a univariate time series. In a recent study, the quantification of RPs has been extended by transferring the well-known box-counting algorithm to recurrence analysis2. We build on this novel formalism by introducing another box-counting measure that was originally put forward by B. Mandelbrot, namely succolarity3. Succolarity quantifies how well a fluid can permeate a binary texture4. We employ this measure by flooding a RP with a (fictional) fluid along its diagonals and computing succolarity as a measure of diagonal flow through the RP. Since a non-optimal choice of embedding parameters impedes the formation of diagonal lines in the RP and generally results in spurious patterns that block the fluid, the attractor reconstruction problem can be formulated as a maximization of diagonal recurrence flow.

The proposed state space reconstruction algorithm allows for non-uniform embedding delays to account for multiscale dynamics. It is conceptually and computationally simple and (nearly) parameter-free. Even in presence of moderate to high noise intensity, reliable results are obtained. We compare the method’s performance to existing techniques and showcase its effectiveness in applications to paradigmatic examples and nonlinear geoscientific time series.

 

References:

1 Packard, N. H., Crutchfield, J. P., Farmer, J. D., & Shaw, R. S. (1980). Geometry from a time series. Physical review letters, 45(9), 712.

2 Braun, T., Unni, V. R., Sujith, R. I., Kurths, J., & Marwan, N. (2021). Detection of dynamical regime transitions with lacunarity as a multiscale recurrence quantification measure. Nonlinear Dynamics, 1-19.

3 Mandelbrot, B. B. (1982). The fractal geometry of nature (Vol. 1). New York: WH freeman.

4 de Melo, R. H., & Conci, A. (2013). How succolarity could be used as another fractal measure in image analysis. Telecommunication Systems, 52(3), 1643-1655.

How to cite: Braun, T., Kraemer, K. H., and Marwan, N.: A Recurrence Flow based Approach to Attractor Reconstruction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9626, https://doi.org/10.5194/egusphere-egu22-9626, 2022.

EGU22-11064 | Presentations | NP4.1

The Objective Deformation Component of a Velocity Field 

Bálint Kaszás, Tiemo Pedergnana, and George Haller

According to a fundamental axiom of continuum mechanics, material response should be objective, i.e., indifferent to the observer. In the context of geophysical fluid dynamics, fluid-transporting vortices must satisfy this axiom and hence different observers should come to the same conclusion about the location and size of these vortices. As a consequence, only objectively defined extraction methods can provide reliable results for material vortices.

As velocity fields are inherently non-objective, they render most Eulerian flow-feature detection non-objective. To resolve this issue,  we discuss a general decomposition of a velocity field into an objective deformation component and a rigid-body component. We obtain this decomposition as a solution of a physically motivated extremum problem for the closest rigid-body velocity of a general velocity field.

This extremum problem turns out to have a unique,  physically interpretable,  closed-form solution. Subtracting this solution from the velocity field then gives an objective deformation velocity field that is also physically observable. As a consequence, all common Eulerian feature detection schemes, as well as the momentum, energy, vorticity, enstrophy, and helicity of the flow, become objective when computed from the deformation velocity component. We illustrate the use of this deformation velocity field on several velocity data sets.

How to cite: Kaszás, B., Pedergnana, T., and Haller, G.: The Objective Deformation Component of a Velocity Field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11064, https://doi.org/10.5194/egusphere-egu22-11064, 2022.

EGU22-11118 | Presentations | NP4.1

Explainable community detection of extreme rainfall events using the tangles algorithmic framework 

Merle Kammer, Felix Strnad, and Bedartha Goswami

Climate networks have helped to uncover complex structures in climatic observables from large time series data sets. For instance, climate networks were used to reduce rainfall data to relevant patterns that can be linked to geophysical processes. However, the identification of regions that show similar behavior with respect to the timing and spatial distribution of extreme rainfall events (EREs) remains challenging. 
To address this, we apply a recently developed algorithmic framework based on tangles [1] to discover community structures in the spatial distribution of EREs and to obtain inherently interpretable communities as an output. First, we construct a climate network using time-delayed event synchronization and create a collection of cuts (bipartitions) from the EREs data. By using these cuts, the tangles algorithmic framework allows us to both exploit the climate network structure and incorporate prior knowledge from the data. Applying tangles enables us to create a hierarchical tree representation of communities including the likelihood that spatial locations belong to a community. Each tree layer can be associated to an underlying cut, thus making the division of different communities transparent. 
Applied to global precipitation data, we show that tangles is a promising tool to quantify community structures and to reveal underlying geophysical processes leading to these structures.

 

[1] S. Klepper, C. Elbracht, D. Fioravanti,  J. Kneip, L. Rendsburg, M. Teegen, and U. von Luxburg. Clustering with Tangles: Algorithmic Framework and Theoretical Guarantees. CoRR, abs/2006.14444v2, 2021. URL https://arxiv.org/abs/2006.14444v2.

How to cite: Kammer, M., Strnad, F., and Goswami, B.: Explainable community detection of extreme rainfall events using the tangles algorithmic framework, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11118, https://doi.org/10.5194/egusphere-egu22-11118, 2022.

EGU22-11667 | Presentations | NP4.1

Spurious Behaviour in Networks from Spatio-temporal Data 

Moritz Haas, Bedartha Goswami, and Ulrike von Luxburg

Network-based analyses of dynamical systems have become increasingly popular in climate science. Instead of focussing on the chaotic systems aspect, we come from a statistical perspective and highlight the often ignored fact that the calculated correlation values are only empirical estimates. We find that already the uncertainty stemming from the estimation procedure has major impact on network characteristics. Using isotropic random fields on the sphere, we observe spurious behaviour in commonly constructed networks from finite samples. When the data has locally coherent correlation structure, even spurious link-bundle teleconnections have to be expected. We reevaluate the outcome and robustness of existing studies based on their design choices and null hypotheses.

How to cite: Haas, M., Goswami, B., and von Luxburg, U.: Spurious Behaviour in Networks from Spatio-temporal Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11667, https://doi.org/10.5194/egusphere-egu22-11667, 2022.

EGU22-12351 | Presentations | NP4.1

VAE4OBS: Denoising ocean bottom seismograms using variational autoencoders 

Maria Tsekhmistrenko, Ana Ferreira, Kasra Hosseini, and Thomas Kitching

Data from ocean-bottom seismometers (OBS) are inherently more challenging than their land counterpart because of their noisy environment. Primary and secondary microseismic noises corrupt the recorded time series. Additionally, anthropogenic (e.g., ships) and animal noise (e.g., Whales) contribute to a complex noise that can make it challenging to use traditional filtering methods (e.g., broadband or Gabor filters) to clean and extract information from these seismograms. 

OBS deployments are laborious, expensive, and time-consuming. The data of these deployments are crucial in investigating and covering the "blind spots" where there is a lack of station coverage. It, therefore, becomes vital to remove the noise and retrieve earthquake signals recorded on these seismograms.

We propose analysing and processing such unique and challenging data with Machine Learning (ML), particularly Deep Learning (DL) techniques, where conventional methods fail. We present a variational autoencoder (VAE) architecture to denoise seismic waveforms with the aim to extract more information than previously possible. We argue that, compared to other fields, seismology is well-posed to use ML and DL techniques thanks to massive datasets recorded by seismograms. 

In the first step, we use synthetic seismograms (generated with Instaseis) and white noise to train a deep neural network. We vary the signal-to-noise ratio during training. Such synthetic datasets have two advantages. First, we know the signal and noise (as we have injected the noise ourselves). Second, we can generate large training and validation datasets, one of the prerequisites for high-quality DL models.

Next, we increased the complexity of input data by adding real noise sampled from land and OBS to the synthetic seismograms. Finally, we apply the trained model to real OBS data recorded during the RHUM-RUM experiment.

We present the workflow, the neural network architecture, our training strategy, and the usefulness of our trained models compared to traditional methods.

How to cite: Tsekhmistrenko, M., Ferreira, A., Hosseini, K., and Kitching, T.: VAE4OBS: Denoising ocean bottom seismograms using variational autoencoders, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12351, https://doi.org/10.5194/egusphere-egu22-12351, 2022.

EGU22-13053 | Presentations | NP4.1

Causal Diagnostics for Observations - Experiments with the L63 system 

Nachiketa Chakraborty and Javier Amezcua

Study of cause and effect relationships – causality - is central to identifying mechanisms that cause the phenomena we observe. And in non-linear, dynamical systems, we wish to understand these mechanisms unfolding over time. In areas within physical sciences like geosciences, astrophysics, etc. there are numerous competing causes that drive the system in complicated ways that are hard to disentangle. Hence, it is important to demonstrate how causal attribution works with relatively simpler systems where we have a physical intuition. Furthermore, in earth and atmospheric sciences or meteorology, we have a plethora of observations that are used in both understanding the underlying science beneath the phenomena as well as forecasting. However in order to do this, optimally combining the models (theoretical/numerical) with the observations through data assimilation is a challenging, computationally intensive task. Therefore, understanding the impact of observations and the required cadence is very useful. Here, we present experiments in causal inference and attribution with the Lorenz 63 system – a system studied for a long time. We first test the causal relations between the variables characterising the model. And then we simulate observations using perturbed versions of the model to test the impact of the cadence of observations of each combination of the 3 variables.

How to cite: Chakraborty, N. and Amezcua, J.: Causal Diagnostics for Observations - Experiments with the L63 system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13053, https://doi.org/10.5194/egusphere-egu22-13053, 2022.

An accurate understanding of dynamical similarities and dissimilarities in geomagnetic variability between quiet and disturbed periods has the potential to vastly improve Space Weather diagnosis. During the last years, several approaches rooted in dynamical system theory have demonstrated their great potentials for characterizing the instantaneous level of complexity in geomagnetic activity and solar wind variations, and for revealing indications of intermittent large-scale coupling and generalized synchronization phenomena in the Earth’s electromagnetic environment. In this work, we focus on two complementary approaches based on the concept of recurrences in phase space, both of which quantify subtle geometric properties of the phase space trajectory instead of taking an explicit temporal variability perspective. We first quantify the local (instantaneous) and global fractal dimensions and associated local stability properties of a suite of low (SYM-H, ASY-H) and high latitude (AE, AL, AU) geomagnetic indices and discuss similarities and dissimilarities of the obtained patterns for one year of observations during a solar activity maximum. Subsequently, we proceed with studying bivariate extensions of both approaches, and demonstrate their capability of tracing different levels of interdependency between low and high latitude geomagnetic variability during periods of magnetospheric quiescence and along with perturbations associated with geomagnetic storms and magnetospheric substorms, respectively. Ultimately, we investigate the effect of time scale on the level of dynamical organization of fluctuations by studying iterative reconstructions of the index values based on intrinsic mode functions obtained from univariate and multivariate versions of empirical mode decomposition. Our results open new perspectives on the nonlinear dynamics and (likely intermittent) mutual entanglement of different parts of the geospace electromagnetic environment, including the equatorial and westward auroral electrojets, in dependence of the overall state of the geospace system affected by temporary variations of the solar wind forcing. In addition, they contribute to a better understanding of the potentials and limitations of two contemporary approaches of nonlinear time series analysis in the field of space physics.

How to cite: Donner, R., Alberti, T., and Faranda, D.: Instantaneous fractal dimensions and stability properties of geomagnetic indices based on recurrence networks and extreme value theory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13342, https://doi.org/10.5194/egusphere-egu22-13342, 2022.

EGU22-1362 | Presentations | PS5.1

Saturn ring structure inferred from comparison of Cassini observations with laboratory simulations 

Libor Nouzak, Jiri Pavlu, Jakub Vaverka, Jana Safrankova, Zdenek Nemecek, David Pisa, Mitchell Shen, Zoltan Sternovsky, and Shengyi Ye

Cassini spacecraft investigated the Saturn environment more than 13 years. In course of this long period, the RPWS (Radio Plasma Wave Science) experiment not only mapped electric fields in the Saturn’s magnetosphere but also registered a large number of sharp spiky signals caused by hypervelocity dust impacts within Saturn rings. We have identified more than 140 000 such waveforms recorded by electric antennas with 10 or 80 kHz cadence in a close proximity of the ring mid-plane (up to 0.2 Rs). Among them, shapes and amplitudes of more than 100 000 non-saturated impacts were corrected on the Cassini WBR (Wide Band Receiver) transfer function.

Our laboratory experiment with the 1:20 reduced model of Cassini positioned in the test chamber of the dust accelerator allowed us to determine dependences of the signal shape and amplitude on the dust parameters (velocity and mass) and spacecraft potential. We apply these results on calculations of the mass and size distributions of dust particles detected by the electric field antennas within the Saturn ring system. The core of the paper is devoted to relation between dust characteristics (determined from impact signals and local plasma parameters) and ring mass profiles at distances ranging from 2 to 60 Rs from the surface.

How to cite: Nouzak, L., Pavlu, J., Vaverka, J., Safrankova, J., Nemecek, Z., Pisa, D., Shen, M., Sternovsky, Z., and Ye, S.: Saturn ring structure inferred from comparison of Cassini observations with laboratory simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1362, https://doi.org/10.5194/egusphere-egu22-1362, 2022.

EGU22-1363 | Presentations | PS5.1

Laboratory Simulation of the Dust Interaction with Energetic Particles and its Implication for Interstellar medium 

Jiri Pavlu, Jan Wild, Jakub Cizek, Libor Nouzak, Jakub Vaverka, Jana Safrankova, and Zdenek Nemecek

Dust in the interstellar space is illuminated by cosmic radiation that consists of photons of different wavelengths and energetic charged particles. Whereas the photoemission is rather well understood, charging of dust grains due to interaction of with energetic charged particles was not experimentally studied in detail so far. We report the first laboratory experiment dealing with the interaction of a cosmic dust simulant with energetic charged particles emitted from a radioisotope. Measurements of the charge of micrometer silicate dust grains with an accuracy of one elementary charge revealed several processes leading to the dust charging. The observed average rate of charging events agrees well with prediction of a model based on the continuous slowing down approximation of energetic particles inside the grain. Charge steps larger than one elementary charge were attributed to emission of secondary electrons excited by the primary particle slowing down. The determined yield of secondary electron emission is approximately inversely proportional to the grain radius. The experimental results led us to the formulation of a possible scenario of interstellar dark clouds charging.

How to cite: Pavlu, J., Wild, J., Cizek, J., Nouzak, L., Vaverka, J., Safrankova, J., and Nemecek, Z.: Laboratory Simulation of the Dust Interaction with Energetic Particles and its Implication for Interstellar medium, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1363, https://doi.org/10.5194/egusphere-egu22-1363, 2022.

EGU22-1722 | Presentations | PS5.1

Dust Grain Detection by the Solar Orbiter Radio and Plasma Wave instrument 

Jakub Vaverka, Jiri Pavlu, Libor Nouzak, Jana Safrankova, Zdenek Nemecek, David Pisa, Jan Soucek, Arnaud Zaslavsky, and Milan Maksimovic

Hypervelocity dust impacting the spacecraft body can be either partly or totally destroyed and evaporated and then creates a cloud of charged particles. Electrons and ions generated by such impacts can consequently influence the spacecraft potential and/or measurements of on-board scientific instruments. Electric field instruments are sensitive to these disturbances and typically register signals generated by dust impacts as short pulses. Once they are distinguished from other signals, they can be used for the detection of dust grains by spacecraft (even without dedicated dust detectors). 

Solar Orbiter is equipped with the RPW (Radio and Plasma Wave) instrument including three electric field antennas allowing such detection. The time domain sampler (TDS) subsystem of RPW provides typically short electric field waveforms (62.5 ms) sampled at a rate of 262.1 kHz

We have analyzed individual electric field waveforms of dust impacts detected by Solar Orbiter RPW/TDS and sorted into different categories (typical dust impact, impacts with the complex response, misinterpreted events, and suspicious events). Typical dust impacts are compared with an expected signal based on a model of dust impacts. The reliability of dust detection (fraction of misinterpreted and suspicious events) is evaluated with respect to the distance from the Sun.

How to cite: Vaverka, J., Pavlu, J., Nouzak, L., Safrankova, J., Nemecek, Z., Pisa, D., Soucek, J., Zaslavsky, A., and Maksimovic, M.: Dust Grain Detection by the Solar Orbiter Radio and Plasma Wave instrument, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1722, https://doi.org/10.5194/egusphere-egu22-1722, 2022.

EGU22-1750 | Presentations | PS5.1

One-year analysis of dust detection using dipole electric field antennas at Mars by MAVEN 

Samia Ijaz, Jakub Vaverka, Jana Safrankova, and Zdenek Nemecek

Detection of dust grains in space is limited by a small number of dedicated dust detectors, however, we aim to study dust detection using electric field instruments usually placed on the majority of scientific spacecraft. This technique has been previously applied to detect dust impacts in space for several decades. The major advantage of this method is that entire spacecraft surface acts as a detector. We present a preliminary statistical analysis of 1-year (2015) observations of dust impacts by the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. The pulses generated by dust impacts were identified in data of the Langmuir Probe and Wave instrument operating in a dipole configuration (probe to probe potential measurement). Out of all the modes we use the medium frequency burst mode, the data covers 62.5 milliseconds using 4096 measured points which gives us a sampling frequency of 66.67 kHz. First, our algorithm selected events for which the derivative exceeded a threshold value. Second, these preselected events were further categorized into groups. Several groups contained suspicious events which are most likely not related to dust impacts. In total, we find 9848 events at altitudes ranging from less than 200 to 6000 kilometers that we can interpret as dust impacts. The distribution of these dust events around the Mars orbit is discussed.

How to cite: Ijaz, S., Vaverka, J., Safrankova, J., and Nemecek, Z.: One-year analysis of dust detection using dipole electric field antennas at Mars by MAVEN, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1750, https://doi.org/10.5194/egusphere-egu22-1750, 2022.

EGU22-2013 | Presentations | PS5.1

Dayside to nightside dust column density ratios in the inner comae of comets 

Nicolas Thomas, Raphael Marschall, Selina-Barbara Gerig, and Olga Pinzon-Rodriguez

It was recognized in observations of the innermost coma of comet 1P/Halley by the Halley Multicolour Camera onboard Giotto, that the dayside dust coma was, on average, only around a factor 3.2 brighter than the dust coma on the nightside. This was considered surprising because the phase angle of the approach (107.2°) was not substantially different from a terminator viewing direction. The dominance of water sublimation in comets and the assumption that nightside activity should be strongly limited led to the conclusion that lateral (non-radial) flow of dust from the dayside to the nightside must be responsible. This was apparently supported qualitatively by evidence of dust gradients seen against the background of the shadowed nucleus (Keller and Thomas, 1989).

Using observations from the MICAS camera on Deep Space 1, Ho et al. (2003) found for 19P/Borrelly a dayside to nightside coma brightness ratio (DS:NS) of just 1.7 at a phase angle of 88° and rh= 1.36 AU and subsequently compared this to the results from 1P/Halley (Ho et al., 2007). The brightness ratio was even smaller despite the observation being from almost directly above the terminator. This observation has not been widely promoted, possibly in part because of the quite poor imaging quality of MICAS.

Lateral flow is not the only means of producing low values of DS:NS. Both slow moving particles in orbit about the nucleus and nightside outgassing can influence the observed column density ratio. Gerig et al. (2020) have investigated the observational data at 67P/Churyumov-Gerasimenko and have established both the low DS:NS ratio (as at the other comets) and an increasing DS:NS ratio with reducing heliocentric distance. Furthermore, the brightness distribution with distance in the innermost coma most closely fits radial outflow suggesting that gravitationally bound particles are not the dominant influence on DS:NS. Pinzon-Rodriguez et al. (2021) have modelled H2O and CO2 emissions from 67P in a simplified, coupled, thermal system and shown that for reasonable parameters, nightside emission of dust driven by CO2 is a promising explanation for the observations.

The presentation will provide the observational evidence for the DS:NS ratio, describe the modelling work, and demonstrate the results.

 

Gerig, S.-B., et al., (2020) , Icarus, 351, 113968.

Ho, T.M., et al., (2003), Advances in Space Research, 31, 2583.

Ho, T.-M., et al. (2007), Planetary and Space Science, 55, 974-985.

Keller, H.U. and N. Thomas, (1989), Astronomy and Astrophysics, 226, L9.

Pinzón-Rodríguez, O., et al., (2021), Astronomy and Astrophysics, 655, A20.

How to cite: Thomas, N., Marschall, R., Gerig, S.-B., and Pinzon-Rodriguez, O.: Dayside to nightside dust column density ratios in the inner comae of comets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2013, https://doi.org/10.5194/egusphere-egu22-2013, 2022.

EGU22-3872 | Presentations | PS5.1

The hunt for liquid water in meteorites 

Peter A.B. Krizan, Queenie H. -S. Chan, Amy Gough, and Dominic Papineau

Hydrothermal alteration is one of the fundamental processes by which several planetary bodies within our Solar System have been modified. The abundance of transient liquid water throughout the Solar System is increasingly recognised as playing a vital and active role in shaping the evolution of planetary surfaces. In particular, the process of hydrothermal alteration affects mineral composition on a microscopic level, simultaneously altering pre-existing minerals and allowing new mineral species to nucleate. This research reports new findings of fluid inclusions and their composition from one achondrite meteorite (Allan Hills A77256) and eight chondrite meteorites (Allan Hills 84029, Bells, Lonewolf Nunataks 94101 & 94102, Mighei, Santa Cruz, Sutter’s Mill, Sayama). We show that the presence of fluid inclusions within these meteorites is much more common than previously recognised, spanning much of the diversity of chondritic meteorite classes.

The first discovery of extraterrestrial liquid water was within halite crystals of the Zag and Monahans (1998) ordinary chondrites in 1999. Recent studies concerning extraterrestrial water and its evolution throughout the Solar System have attempted to gather inferences on the hydrothermal histories of parent asteroid bodies by utilising different proxies, including (but not limited to) magnetite grains, hydrous minerals, and degree of thermal metamorphism. These studies have highlighted a lack of direct water samples used within research and the need to determine whether further extraterrestrial liquid water fluid inclusions exist. Aside from those within the Zag and Monahans (1998) chondrites, additional claims of fluid inclusions within other meteorites have been previously reported. Until now, none have been independently confirmed or analysed further to determine whether or not they host liquid water.

Here we show that both petrographically primary and secondary in all our nine meteorites are hosted in olivine. Due to the formational nature of olivine, we predict that all petrographically primary fluid inclusions will fail to host liquid water. In contrast, petrographically secondary fluid inclusions may prove to be more plausible candidates. These inclusions are much more likely to possess liquid water as they were likely formed by subsequent and late periods of localised hydrothermal alteration, resulting in the serpentinisation of the host olivine crystals. Despite their predominance within our samples, in many cases, the analysis of secondary fluid inclusions is impeded by their sub-micron sizes and technological limitations of the instruments to operate at such a minuscule specimen size (< 1µm).

This research utilises a combination of SEM-EDS and Raman spectroscopy to target and determine the composition of the trapped fluids within suitable inclusions (diameter > 1µm). Spectra from initial Raman analyses conducted on selected fluid inclusions within olivine crystals of the Bells and Santa Cruz carbonaceous chondrites are presented. The majority of spectra from twenty-eight analysed fluid inclusions showed the fingerprint wavelength peak for olivine between 820-850 cm-1 alongside an unanticipated discovery of several cosmic diamonds embedded deep within certain olivine grains at a wavelength peak of 1320-1360 cm-1. This research highlights that numerous factors can affect the probability of a fluid inclusion hosting liquid water. 

How to cite: Krizan, P. A. B., H. -S. Chan, Q., Gough, A., and Papineau, D.: The hunt for liquid water in meteorites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3872, https://doi.org/10.5194/egusphere-egu22-3872, 2022.

EGU22-4363 | Presentations | PS5.1

An analytical model for dust impact voltage signals, and its application to STEREO/WAVES data 

Kristina Rackovic Babic, Arnaud Zaslavsky, Karine Issautier, Nicole Meyer-Vernet, and Dusan Onic

Dust grains are a common constituent of the Solar system. Dust impacts have been observed using radio and wave instruments onboard spacecraft since the 1980s. Voltage waveforms show typical impulsive signals generated by dust grains. We aim at developing models of how signals are generated to be able to link observed electric signals to the physical properties of the impacting dust. To validate the model, we use the Time Domain Sampler (TDS) subsystem of the STEREO/WAVES instrument which generates high-cadence time series of voltage pulses for each monopole. A model that we propose takes into account impact-ionization-charge collection and electrostatic-influence effects. It is an analytical expression for the pulse and allows us to measure the of amount of the total ion charge, the fraction of escaping charge, the rise timescale, and the relaxation timescale. The model is simple and convenient for massive data fitting. To check our model’s accuracy, we collected all the dust events detected by STEREO/WAVES/TDS simultaneously on all three monopoles at 1AU since the beginning of the STEREO mission in 2007. Our study confirms that the rise time largely exceeds the spacecraft’s short timescale of electron collection. Our estimated rise time value allows us to determine the propagation speed of the ion cloud, which is the first time that this information has been derived from space data. Our model also makes it possible to determine properties associated with the electron dynamics, in particular the order of magnitude of the electron escape current. The obtained value gives us an estimate of the cloud’s electron temperature — a result that, as far as we know, has never been obtained before except in laboratory experiments. Furthermore, a strong correlation between the total cloud charge and the escaping charge allows us to estimate the escaping current from the amplitude of the precursor, a result that could be interesting for the study of the pulses recently observed in the magnetic waveforms of Solar Orbiter or Parker Solar Probe, for which the electric waveform is saturated.

How to cite: Rackovic Babic, K., Zaslavsky, A., Issautier, K., Meyer-Vernet, N., and Onic, D.: An analytical model for dust impact voltage signals, and its application to STEREO/WAVES data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4363, https://doi.org/10.5194/egusphere-egu22-4363, 2022.

EGU22-4474 | Presentations | PS5.1

The search for low-abundant species in the coma of comet 67P/Churyumov-Gerasimenko 

Frederik Dhooghe, Johan De Keyser, Nora Hänni, Kathrin Altwegg, Gaël Cessateur, Emmanuel Jehin, Romain Maggiolo, Martin Rubin, and Peter Wurz

During the ESA/Rosetta mission more than 1.5 million individual mass spectra have been obtained in the coma of 67P/Churyumov-Gerasimenko with the ROSINA/DFMS mass spectrometer. A single spectrum at a specific mass represents the accumulation of 3000 scans with an integration time of 6.6 ms, for a 19.8 s total measuring time.

DFMS data has been a source of information on coma composition and even on refractories. Although DFMS has a high sensitivity and high dynamic range, there may still be species hidden in the spectra. One approach to improve the signal-to-noise ratio is the summation of spectra. This way, species with a low abundance, close to the limit of detection of DFMS, should become more pronounced, however, at the cost of the loss of possible time variability information.  Unfortunately, the creation of sum spectra is not straightforward. Sum spectra need a clean dataset, where all erroneous and non-cometary data have been removed. Also, instrumental effects (e.g. detector aging, changes in settings in the course of the mission) need to be taken into account.

This contribution will present the methodology and some first results for sum spectra from DFMS. It is shown how this approach can provide inputs in the search for Fe and Ni in comet 67P.

How to cite: Dhooghe, F., De Keyser, J., Hänni, N., Altwegg, K., Cessateur, G., Jehin, E., Maggiolo, R., Rubin, M., and Wurz, P.: The search for low-abundant species in the coma of comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4474, https://doi.org/10.5194/egusphere-egu22-4474, 2022.

EGU22-4837 | Presentations | PS5.1

Validation and calibration of gas flow experiments with numerical simulations 

Sunny Laddha, Wolfgang Macher, Stephan Zivithal, and Günter Kargl

The success of the Rosetta mission to comet 67P/Churyumov–Gerasimenko has revolutionized our view of comets, while opening a plethora of new questions. In order to find the answers to them and harness the full potential of the new data, an international consortium named “Cophylab – Comet Physics Laboratory” (Cophylab.space) was launched in 2018. In this project several experiment campaigns were initialized to study cometary properties in a controlled environment. The idea was to isolate individual properties and processes in dedicated laboratory experiments. One of the experiment campaigns was designed to characterize gas flow properties of dry porous materials in a first step, with the aim of developing a model that improves our understanding of the outgassing of comets.

Before the initial model is extended to consider the sublimation of volatile components, it needs to be validated by alternative methods, such as numerical simulations. For this purpose, we chose the finite element method, to test the combination of the Darcy and Knudsen flow model, which was used in the preceding study.

Our approach was to use the results of the experiment as input in the simulations and compare the output with the measurements. This comparison confirmed the validity of the model and its assumptions. In particular, the sample is assumed to be homogenous and isotropic on a macroscopic scale, so that it can be described by a set of averaged parameters. While this description is relatively accurate for samples with well-defined grain shapes (e.g. spherical glass beads), significant discrepancies occur for inhomogeneous materials such as lunar, Asteroid or Martian analogues.

We investigated various aspects that were initially neglected in the evaluation of the measurements, such as channel building in the sample, boundary effects and non-ideal geometry of the experimental setup, which will be complemented by inhomogeneities that occur naturally in random close packing or ballistic deposition samples. Furthermore, we assessed the models range of applicability through a thorough review of the different flow regimes encountered in the measurements. Our findings indicate that boundary effects, as well as non-ideal geometry have a significant influence particularly in samples with larger grains. For finer grained samples on the other hand, inhomogeneities are the most probable cause for discrepancies. The grain size also plays an important role regarding the flow regime and its corresponding parameters.

The work for this study was performed in the framework of a master’s thesis, as part of the Cophylab project, which is funded by the D-A-CH program (DFG GU1620/3-1 and BL 298/26-1 / SNF 200021E 177964 / FWF I 3730-N36)

How to cite: Laddha, S., Macher, W., Zivithal, S., and Kargl, G.: Validation and calibration of gas flow experiments with numerical simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4837, https://doi.org/10.5194/egusphere-egu22-4837, 2022.

EGU22-5656 | Presentations | PS5.1

Decoupling of chemical and isotope fractionation processes during atmospheric entry of S-type micrometeorites 

Seppe Lampe, Bastien Soens, Stepan Chernonozhkin, Claudia González de Vega, Matthias van Ginneken, Flore Van Maldeghem, Frank Vanhaecke, Billy Glass, Ian Franchi, Herman Terryn, Vinciane Debaille, Philippe Claeys, and Steven Goderis

During atmospheric entry, micrometeorites experience variable degrees of (i) evaporation due to gas drag heating and (ii) mixing with atmospheric oxygen. Evaporation affects the physical properties and chemical and isotopic compositions of fully melted cosmic spherules (CSs). Oxygen isotope ratios of pristine micrometeorites are commonly used to relate these particles to their appropriate parent bodies. However, the degree of mixing with atmospheric oxygen and isotope fractionation by evaporation in CSs generally remains unclear, leading to uncertainties in their initial oxygen isotope ratios, which in turn complicates the precursor body identification. Previously, several studies have estimated the degree of evaporation based on contents of major refractory elements Ca and Al in combination with Fe/Si atomic ratios. This now commonly adopted chemical classification system has not yet been assessed with O and Fe isotope variability. As evaporation leads to both isotope and chemical fractionation, it is imperative to verify whether the predicted amounts of evaporation based on isotopic and chemical proxies converge.

Here, we measure the major and trace element compositions of 57 chondritic (mostly vitreous) CSs, along with their Fe isotope ratios. The δ56Fe isotope and chemical (K, Zn, Na or CaO and Al2O3 concentrations) fractionation in these particles show no correlation. This can be interpreted in two ways: (i) separate processes govern chemical and isotope fractionation or (ii) the selected proxies for isotope and/or chemical fractionation are inadequate. Because the initial Fe isotope ratios of chondrites display limited variation (0.005 ± 0.008‰ δ56Fe), Fe isotope ratios in CSs are assumed to only have changed through evaporation. At the same time, the chemical compositions of CSs show larger variability, so the CSs are thus often not chemically representative of their precursor bodies.

As oxygen isotope ratios are commonly used to identify the precursor bodies of (micro)meteorites, triple oxygen isotope ratios are measured in 37 of the 57 CSs. Based on the relationship between δ57Fe and δ18O, the effect of evaporation on the O isotope ratios can be corrected, which allows for a more precise precursor body reconstruction. Via this method, two 16O-poor spherules with greatly varying degrees of isotope fractionation (~1.0‰ and 29.1‰ δ56Fe, respectively) can be distinguished. Furthermore, it is observed that CSs that likely have an OC-like heritage all underwent the same degree of atmospheric mixing (~8‰ δ18O). These findings highlight the potential of including Fe isotope measurements to the regular methodologies applied to CS studies.

How to cite: Lampe, S., Soens, B., Chernonozhkin, S., González de Vega, C., van Ginneken, M., Van Maldeghem, F., Vanhaecke, F., Glass, B., Franchi, I., Terryn, H., Debaille, V., Claeys, P., and Goderis, S.: Decoupling of chemical and isotope fractionation processes during atmospheric entry of S-type micrometeorites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5656, https://doi.org/10.5194/egusphere-egu22-5656, 2022.

EGU22-6375 | Presentations | PS5.1

The ESA Hera mission to the binary asteroid (65803) Didymos:Planetary Defense and Science 

Michael Küppers, Patrick Michel, Stephan Ulamec, Alan Fitzsimmons, Simon Green, Monica Lazzarin, Ian Carnelli, and Paolo Martino and the The Hera Science Team

The impact of the NASA DART spacecraft on the 160 m-diameter natural satellite called Dimorphos
of the binary asteroid 65803 Didymos on 26 September 2022 will change its orbital period around
Didymos. The change can be detected by Earth-based observers. Before impact, DART will deploy the Italian LICIACube that will
provide images of the first instants after impact. ESA’s Hera spacecraft will rendezvous Didymos four
years after the impact.

Hera will characterize in detail the properties of a Near-Earth Asteroid that are most relevant to
planetary defense:
•Measuring the mass of Dimorphos to determine the momentum transfer efficiency from DART
impact.
•Investigating in detail the crater produced by DART to improve our understanding of the cratering
process and the mechanisms by which the crater formation drives the momentum transfer
efficiency.
•Observing subtle dynamical effects (e.g. libration imposed by the impact, orbital and spin
excitation of Dimorphos) that are difficult to detect for remote observers.
•Characterising the surface and interior of Dimorphos to allow scaling of the momentum transfer
efficiency to different asteroids.

Hera will also provide unique asteroid science. It will rendezvous for the first
time with a binary asteroid. The secondary has a diameter of only 160 m, the smallest asteroid visited so far. Moreover, for the first time, internal and subsurface properties will be directly measured. From small asteroid internal and surface structures, through
rubble-pile evolution, impact cratering physics, to the long-term effects of space weathering in the
inner Solar System, Hera will have a major impact on many fields. How do binaries form? What is the surface composition of the asteroid pair? What are its internal properties?  What are the surface structure and regolith mobility on both Didymos and Dimorphos?
And what will be the size and the morphology of the crater left by DART? These questions and many others will be addressed by Hera as a natural outcome of its investigations focused on planetary defense.


How to cite: Küppers, M., Michel, P., Ulamec, S., Fitzsimmons, A., Green, S., Lazzarin, M., Carnelli, I., and Martino, P. and the The Hera Science Team: The ESA Hera mission to the binary asteroid (65803) Didymos:Planetary Defense and Science, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6375, https://doi.org/10.5194/egusphere-egu22-6375, 2022.

EGU22-6496 | Presentations | PS5.1

Magnetic Signatures associated with Dust Impacts on Parker Solar Probe 

Claire Gasque, Stuart Bale, Trevor Bowen, Thierry Dudok de Wit, Keith Geotz, David Malaspina, Anna Pusack, and Jamey Szalay

As the closest humanmade object to the sun, the Parker Solar Probe (PSP) is uniquely positioned to study inner heliospheric dust. The PSP/FIELDS instrument suite detects dust via short voltage pulses generated by the plasma clouds formed during hypervelocity dust impacts on the spacecraft. Similar dust detection methods have been used on other missions, including Voyager 1 and 2, STEREO, Wind, Cassini, and Solar Orbiter. In addition to the voltage signatures, about 2% of dust impacts captured by Time Domain Sampler (TDS) burst data on PSP/FIELDS are shown to have magnetic signatures measured by the high-frequency winding of PSP's Search Coil Magnetometer (SCM). While magnetic signatures have previously been detected in laboratory hypervelocity impact experiments, they have not been previously reported in space. The signatures are brief (lasting less than 0.1ms), and are associated with high-amplitude voltage signatures. In this work, we present statistics and case studies of dust impacts with magnetic signatures on PSP. We will discuss the TDS calibration required to interpret the measurements physically, along with potential physical mechanisms for the magnetic signatures. We will also present early modeling efforts and implications for future hypervelocity impact studies.

How to cite: Gasque, C., Bale, S., Bowen, T., Dudok de Wit, T., Geotz, K., Malaspina, D., Pusack, A., and Szalay, J.: Magnetic Signatures associated with Dust Impacts on Parker Solar Probe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6496, https://doi.org/10.5194/egusphere-egu22-6496, 2022.

EGU22-6601 | Presentations | PS5.1

Shape and compression of self-gravity wakes in Saturn’s rings 

Larry W. Esposito, Miodrag Sremcevic, Joshua Colwell, Stephanie Eckert, and Richard Jerousek

The varying geometry of Cassini star occultations by Saturn’s rings constrains both the size and shape of structures that block starlight. Statistics of UVIS star occultations measure structures as small as meters, on times scales of minutes to decades. We calculate the excess variance, skewness and kurtosis including the effects of irregular particle shadows, along with a granola bar model of gaps, ghosts (local openings) and self-gravity wakes. In this model, the widths W and separation S of rectangular clumps play an analogous role to the  size of the particle shadows, R. In the first model considered, our calculations are based on the moments of the transparency T in the ring region sampled by the occultation, thus extending the work of  Showalter and Nicholson (1990) to larger τ  and fractional area δ, and to higher central moments, without their simplifying assumptions. We also calculate these statistics using an approach based on the autocovariance, autocoskewness and autocokurtosis.

These new approaches compare well to the formula for excess variance from Showalter and Nicholson in the region where all are accurate, δτ1. Skewness for small τ has a different sign for transparent and opaque structures, distinguishing gaps from clumps. The higher order central moments are calculated from higher powers of the shadow size, thus more sensitive to the extremes of the size distribution. We explain the τ dependence of the excess variance for Saturn’s background C ring by the observation of Jerousek etal(2018) that the measured optical depth is correlated with particle size in the region between 78,000 and 84,600km from Saturn.

Statistics calculated from the granola bar model give different predictions from those based on individual spherical particles. The density waves clearly show compression that triggers clump growth, as predicted by the Predator-Prey model (Esposito etal. 2012, Icarus 217, 103-114). The radial profiles and observed τ dependence suggest that the wave crests compress the gaps more than the wakes, along with broader self-gravity wakes in the wave crests, including transparent ghosts. The UVIS observations fall between the most regular and the most irregular granola bar models. Analysis of ring transparency favors irregularly-spaced elongated clumps. A closer analysis of this particular case gives H/W < 0.12, smaller than Colwell etal. (2007, Icarus 190, 127-144), suggesting wakes are more like linguine than granola bars.

How to cite: Esposito, L. W., Sremcevic, M., Colwell, J., Eckert, S., and Jerousek, R.: Shape and compression of self-gravity wakes in Saturn’s rings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6601, https://doi.org/10.5194/egusphere-egu22-6601, 2022.

EGU22-6920 | Presentations | PS5.1

Exploiting multi-point in situ measurements during the Comet Interceptor comet flyby 

Johan De Keyser, Pierre Henri, and Cyril Simon-Wedlund

The ability to conduct multi-point measurements is a hallmark of the ESA-JAXA/Comet Interceptor mission currently in development. The mission consists of one spacecraft (A) and two probes (B1 and B2) which are expected to fly by a medium- to high-activity comet at a high relative speed (up to 70 km/s). The payload on spacecraft A and on probes B1/B2 provides different opportunities to perform multi-point in-situ data exploitation. We discuss how information about radial, solar zenith angle and latitudinal variations can be extracted from the measurements, for instance using multi-point data analysis techniques inherited from the ESA/Cluster mission. We consider different spacecraft configurations and different geometries for the spacecraft trajectory relative to the comet, as well as target comets with gas production rates between those of 67P/Churyumov-Gerasimenko and 1P/Halley. We highlight the various opportunities and limitations of the proposed algorithms. Particular attention is given to the need for data that are well intercalibrated and discuss what can be done if the intercalibration is not perfect.

How to cite: De Keyser, J., Henri, P., and Simon-Wedlund, C.: Exploiting multi-point in situ measurements during the Comet Interceptor comet flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6920, https://doi.org/10.5194/egusphere-egu22-6920, 2022.

EGU22-6946 | Presentations | PS5.1

Identification of meteorite particles from AMOS data using the new user-friendly software interface. 

Karol Havrila, Maria Gritsevich, and Juraj Tóth

            All-sky camera systems such as the AMOS network, record a large number of fireball events. By using multi-station triangulation method obtain information about trajectory of the body in the description change in altitude and velocity over time. Based on the characteristic of the object trajectory can determine important physical properties as the input mass of the meteoroid or the final mass of meteorites, and thus the probability of the formation and impact of particles on the Earth's surface. For this purpose, we used the method of dimensionless coefficients α (ballistic coefficient) and β (mass loss coefficient), which define the impact of the dynamical and physical properties of meteoroids on the searched input/final masses.

            Large number of recorded fireballs requires automatic data processing and their effective reduction. For this purpose, we have created a program with a user interface that works with data from all-sky fireballs cameras (in our case we focus on data from the Slovak AMOS system), defines the values of α-β coefficients and evaluates the probability of the meteorite formation with specific mass during the flight through the atmosphere. The program gives an interactive settings of physical parameters of the body and thus defines impact on the required values of body input/final masses. This algorithms was created for the purpose of user-friendly processing of scientific data, and the same time serves for the selecting suitable candidates for the formation and impact of dust particles and meteorites on the Earth's surface.

How to cite: Havrila, K., Gritsevich, M., and Tóth, J.: Identification of meteorite particles from AMOS data using the new user-friendly software interface., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6946, https://doi.org/10.5194/egusphere-egu22-6946, 2022.

On the 1st of January 2019, the New Horizons space probe flew by the Kuiper belt object Arrokoth. Images revealed a bilobate shape that would not allow any common map projection to display the complete surface, because multiple points have the same longitude and latitude. Arrokoth shares this feature with 67P/Churyumov-Gerasimenko, the target comet of the Rosetta mission. In order to map the complete surface of the comet, a Quincuncial Adaptive Closed Kohonen (QuACK) map has been fitted to 67P by Grieger (2019). Here, we fit a QuACK map similarly to the shape model of Arrokoth by Stern et al. (2019) and project some of the closest images acquired by the LORRI instrument onto it.

How to cite: Grieger, B.: An unambiguous global map projection for the Kuiper belt object Arrokoth by fitting a Quincuncial Adaptive Closed Kohonen (QuACK) map, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6977, https://doi.org/10.5194/egusphere-egu22-6977, 2022.

EGU22-7975 | Presentations | PS5.1

Peculiar Comets Ejected Early In Solar System Formation 

Sarah E. Anderson, Jean-Marc Petit, Benoît Noyelles, Olivier Mousis, and Philippe Rousselot

Comet C/2016 R2 PanSTARRS presents an unusually high N2/CO abundance ratio, as well as a heavy depletion in H2O, making it the only known comet to have this composition. Two studies have independently estimated the possible origin of this comet from building blocks formed in a peculiar region in the protoplanetary disk, near the ice line of CO and N2. Here we explore the potential fates of comets formed from these building blocks using a numerical simulation of early solar system formation and tracking the dynamics of these objects in the Jumping Neptune scenario. We find that objects formed in the region of the CO- and N2- icelines a are highly likely to be sent towards the Oort Cloud or ejected from the Solar System altogether on a relatively short timescale, thus offering a potential explanation for the scarcity of comets with R2’s unique composition.  

How to cite: Anderson, S. E., Petit, J.-M., Noyelles, B., Mousis, O., and Rousselot, P.: Peculiar Comets Ejected Early In Solar System Formation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7975, https://doi.org/10.5194/egusphere-egu22-7975, 2022.

EGU22-7995 | Presentations | PS5.1

Machine Learning Classification of Dust Impact Signals Observed by The Solar Orbiter Radio and Plasma Waves Instrument 

Andreas Kvammen, Ingrid Mann, and Samuel Kociscak

We present results from automatic classification of dust waveforms observed by The Solar Orbiter Radio and Plasma Waves Instrument.

Every day, several dust particles impacts the Solar Orbiter as the probe travels trough the inner heliosphere. The dust impact produces a cloud of electrons and ions on the spacecraft surface and the free charge causes a sharp and characteristic voltage signal, which decays towards the equilibrium potential after a few milliseconds via interaction with the ambient plasma. Detection and analysis of the characteristic dust waveform can be used to map the density, size and velocity distribution of dust particles in the inner heliosphere, and thus enhance our understanding of the role of dust in the solar system. Such statistical analysis do however require reliable dust detection software.

It is challenging to automatically detect and separate dust waveforms from other signal shapes by "hard coded" algorithms. Both due to spacecraft charging, causing variable shapes of impact signals, and since electromagnetic waves (such as solitary waves) may induce resembling voltage signals. Here we present results of waveform classification using various supervised machine learning techniques, where manually classified data is used both to train and test the classifiers.

We investigate automatic machine learning classification as a possible tool to make statistical analysis of the distribution of dust in the inner heliosphere more reliable and easier to conduct. Furthermore, the classifier may possibly be used on data (after pre-processing) from other spacecrafts with similar instruments, such as the Parker Solar Probe (PSP), the Solar Terrestrial Relations Observatory (STEREO) and the Magnetospheric Multiscale (MMS) mission.

How to cite: Kvammen, A., Mann, I., and Kociscak, S.: Machine Learning Classification of Dust Impact Signals Observed by The Solar Orbiter Radio and Plasma Waves Instrument, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7995, https://doi.org/10.5194/egusphere-egu22-7995, 2022.

EGU22-8746 | Presentations | PS5.1

The interaction of meteoroids with the atmosphere 

Ioana Lucia Boaca, Maria Gritsevich, Mirel Birlan, Alin Nedelcu, and Tudor Boaca

In this work we present the main results of the project named ‘Meteor mathematical modelling of dark flight’ (MeMATH), and current state and future work related to our project. The MeMATH project started in September 2020.

The main objectives of the MeMATH project are:

i) numerical simulation of the dark-flight trajectory;

ii) determining the search area for meteorite fragments;

iii) the study of the ablation of large bodies.

In the first stage of the project, we developed a mathematical model for the dark flight trajectory of a meteoroid. The novelty of our model is that it considers the ellipsoidal shape of the Earth, the Coriolis effect and the centrifugal force.

In the current stage of the project, we are determining the ballistic coefficient α and the mass loss parameter β based on the meteoroid height and deceleration.

The α and β parameters have a great impact in the study of meteoroids from the identification of the parent body to determining the initial and final mass and finding out weather the remnant matter after ablation could result in a meteorite on the ground.

Acknowledgement.

The work of IB and MB was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0784, within PNCDI III.

 

How to cite: Boaca, I. L., Gritsevich, M., Birlan, M., Nedelcu, A., and Boaca, T.: The interaction of meteoroids with the atmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8746, https://doi.org/10.5194/egusphere-egu22-8746, 2022.

EGU22-9487 | Presentations | PS5.1

Primitiveness of cometary dust collected by MIDAS on-board Rosetta 

Minjae Kim, Thurid Mannel, Jeremie Lasue, Andrea Longobardo, Mark Bentley, and Richard Moissl

Comets are thought to have preserved dust particles from the beginning of Solar System formation, providing a unique insight into dust growth mechanisms. The Rosetta mission offered the best opportunity to investigate nearly pristine cometary dust particles of comet 67P/Churyumov–Gerasimenko. Among the three in-situ dust instruments, the MIDAS (Micro-Imaging Dust Analysis System) atomic force microscope collected cometary dust particles with sizes from hundreds of nanometres to tens of micrometres on dedicated targets and recorded their 3D topographic information (Bentley et al. 2016a). However, the straightforward dust collection strategy, i.e., simply hitting the collection targets, leads to an unknown degree of collection alteration (Bentley et al. 2016b)
 
We aim to understand and determine which structural properties of the MIDAS dust particle remained pristine during collection. First, we generate sophisticated dust maps showing the distribution of the dust particles on the collection targets and investigate dust clustering, i.e., determination of which particles stem from a single parent particle that fragmented upon the collection impact. Additionally, in the collaboration with Longobardo et al. 2020a, we use an algorithm to determine from which cometary source regions which MIDAS particles were stemming (Longobardo et al. 2020b). Next, we develop MIDAS particle shape descriptors such as aspect ratio (i.e., height of the particle divided by the square root of area), elongation, circularity, convexity, and particle surface/volume distribution. Furthermore, we compare structures of the MIDAS dust particles and clusters to those found in the laboratory experiments (Ellerborek et al. 2017) and by COSIMA/Rosetta (Langevin et al. 2016). Finally, we combine our findings to calculate a pristinity score for MIDAS particles and determine the most pristine particles and their properties. 

Fig 1. 3D dust coverage map of target 10

We find that there is only a weak trend between shape descriptors and cometary source regions, cluster morphology, and particle characteristics. For example, particles ejected from smooth or rough terrain are similar in their shape properties, which implies that dust particle activity such as dust ejection, partial dry out, and backfall are not responsible for the structure of particles at micrometre scales. Furthermore, the aspect ratio distributions suggest that the subunits of different cluster types are similar in their shape and composition. Thus, the different cluster morphologies detected by MIDAS are not created by a change in subunit properties, but rather by different impact velocities (Lasue et al. 2019). Next, the types of clusters found in MIDAS show good agreement (Ellerbroek et al. 2017), however, there are some differences to those found by COSIMA (Lasue et al. 2019). Furthermore, we found that almost half of the MIDAS particles suffered severe alteration by impact, which indicates dust alteration was inevitable with the given dust collection strategy. Consequently, only ~ 20 particles were rated 'moderately pristine' particles, i.e., not substantially flattened by impact, not fragmented, and/or not part of a fragmentation cluster. The microphysical properties of pristine cometary materials are established in this study and can be translated into properties of laboratory analogue materials for future study.

How to cite: Kim, M., Mannel, T., Lasue, J., Longobardo, A., Bentley, M., and Moissl, R.: Primitiveness of cometary dust collected by MIDAS on-board Rosetta, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9487, https://doi.org/10.5194/egusphere-egu22-9487, 2022.

EGU22-9496 | Presentations | PS5.1

Ballistic landslides on comet 67P/Churyumov–Gerasimenko 

Leszek Czechowski and Konrad Kossacki

Introduction:

The slow ejecta (i.e., with velocity lower than escape velocity) and landslides are similar. Both are forms of gravity movement. After landing, ejecta may be still moving like a ‘regular’ landslide. On the other hand, the motion of landslides may include free fall without contact with the ground

            Observations of comets 9P/Tempe 1 and 67P/Churyumov – Gerasimenko revealed existence of various forms of mass motion [1, 2, 3]. We compare here landslides of matter from Imhotep (in the lobe Body) and from Hathemit (in the lobe Head) depressions.

                                                        Model of ejection

A simple model of processes leading to the formation of slow ejecta is assumed [3]. The phase transition heats a certain underground volume [4, 5, 6]. It leads to vaporization of volatiles. Eventually a cavity is formed. If the pressure in the cavity exceeds some critical value then the crust could be crushed and its fragments will be ejected in the space. Note that the initial velocity of ejecta are usually approximately perpendicular to the physical surface. This assumption was used successfully in [6].

                                                                  Results

           We found that ejecta with the velocity 0.3 m s-1 (or lower) land close to the starting point for both considered depressions. Ejecta faster than 0.5 m s-1 have complex trajectories and may land far from the starting point. For the velocity  0.7 m s-1 (and higher) some of ejecta did not land during modeling even for Imhotep.

             In [6] we have found that ejecta from Hathemit fall in a wide belt mainly on the one hemisphere. For ejecta from Imhotep there is no such pattern.

             The fate of the ejecta after landing depends on many factors: the friction coefficient, the inclination of the place of landing, the vector of velocity, etc. However, often the motion is determined by small scale details. Note that the sliding grain must overcome the worst obstacle on the landing surface.

                                                 Conclusions and future plans

Determining places of deposition of the material ejected from Imhoteb or Hatmelib will allow to determine the composition of the comet's interior under these regions without the need for drilling. This would be particularly important for future missions to the comet.           

Acknowledgements:

The research is partly supported by Polish National Science Centre (decision 2018/31/B/ST10/00169)

References

[1] Czechowski L., (2017)      Geophysical Research Abstract. EGU 2017 April, 26, 2017

[2] Jorda, L., et al. (2016) Icarus, 277, 257-278, ISSN 0019-1035, https://doi.org/10.1016/j.icarus. 2016.05.002.

[3] Auger, et al., (2015). Astronomy and Astrophysics. 583. A35. 10.1051/0004-6361/201525947.

[4] Kossacki K., Czechowski L., (2018). Icarus vol. 305, pp. 1-14, doi: 10.1016/j.icarus.2017.12.027

[5] Kossacki, K.J., Szutowicz, S., (2010). Icarus 207, 320- 340.

[6] Czechowski L. and Kossacki K.J. (2019) Planetary and Space Science 209, 105358, https://doi.org/10.1016/j.pss.2021. 105358 

How to cite: Czechowski, L. and Kossacki, K.: Ballistic landslides on comet 67P/Churyumov–Gerasimenko, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9496, https://doi.org/10.5194/egusphere-egu22-9496, 2022.

EGU22-9660 | Presentations | PS5.1

The Juno Spacecraft Catches a Jupiter Family Comet by the Tail 

John Jørgensen, Peter Jørgensen, Mathias Benn, Anja Andersen, Jack Connerney, Christina Toldbo, Scott Bolton, and Steven Levine

During cruise from Earth to Jupiter, an attitude-sensing star camera scanned the sky in search of objects large and small. That star camera is part of the Advanced Stellar Compass (ASC), a subsystem of the Magnetometer Investigation charged with providing accurate attitude information at the end of Juno’s magnetometer boom.  The main objective of the cruise observation was to search for smaller, unregistered, solar system objects, but quite unexpectedly the system recorded a great many tiny objects ejected from the spacecraft by the impact of high velocity interplanetary dust particles (IDP). This led to the first ever comprehensive profiling of IDPs from 0.88 to 5.2 AU near the ecliptic plane. We observed a rich IDP population between 1.2AU and the 4:1 mean motion resonance with Jupiter near 2.1AU, and in the Kirkwood gaps, the IDP population drops to near zero beyond the 2:1 mean motion resonance with Jupiter at 3.3AU. However, a hundredfold increase in dust impacts with the spacecraft occurred during a 15-day period in December 2015, shortly before entering the Jovian system. We have identified this event with Juno’s passage through a Jupiter family comet tail. Detailed analysis demonstrates that the comet dust population we observed is characterized by cometary dust particles (CDPs) with a beta in the range of 2-10%. Subdued comet activity far from the Sun frustrates direct observations of the comet tail from Earth; however, our analysis shows that the tail evolution is still dominated by non-gravitational forces acting on particles of a few to tens of micrometers. We present the in-situ comet tail observations and couple these to the complex evolution of comet activity and dust tail dynamics.

How to cite: Jørgensen, J., Jørgensen, P., Benn, M., Andersen, A., Connerney, J., Toldbo, C., Bolton, S., and Levine, S.: The Juno Spacecraft Catches a Jupiter Family Comet by the Tail, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9660, https://doi.org/10.5194/egusphere-egu22-9660, 2022.

EGU22-10466 | Presentations | PS5.1

Collisional Evolution of the Inner Zodiacal Cloud: In-Situ observations from PSP and implications for Airless Body Surfaces 

Jamey Szalay, Petr Pokorný, David Malaspina, Anna Pusack, Mihály Horányi, Michael DeLuca, Stuart Bale, Karl Battams, Claire Gasque, Keith Goetz, Harald Krüger, David McComas, Nathan Schwadron, and Peter Strub

The zodiacal cloud is one of the largest structures in the solar system and strongly governed by meteoroid collisions near the Sun. Collisional erosion occurs throughout the zodiacal cloud, yet it has been historically difficult to directly measure. After transiting the inner-most regions of the solar system with Parker Solar Probe (PSP), we find that its dust impact rates are consistent with at least three distinct populations: bound zodiacal dust grains on elliptic orbits (α-meteoroids), unbound β-meteoroids on hyperbolic orbits, and a third population of impactors that may be either direct observations of discrete meteoroid streams or their collisional by-products (“β-streams”). The β-stream from the Geminids meteoroid stream is a favorable candidate for the third impactor population. β-streams of varying intensities are expected to be produced by all meteoroid streams, particularly in the inner solar system, and are a universal phenomenon in all exozodiacal disks. We discuss these recent PSP observations of the dust environment in the very inner solar system, provide constraints on their relative densities and fluxes, and discuss the erosion rate of zodiacal material.

These observations are also directly relevant for understanding the impactor and space weathering environment experienced by airless bodies in the inner solar system. Since the discovery of the Moon's asymmetric ejecta cloud, the origin of its sunward-canted density enhancement has not been well understood. Ejecta is produced from β-meteoroids which impact the Moon's sunward side at similar locations to this previously unresolved asymmetry. These small grains are submicron in size, comparable to or smaller than the lunar regolith particles they hit, and can impact the Moon at very high speeds ~100 km s-1.  Incorporating β-meteoroid fluxes observed by the Pioneers 8 & 9, Ulysses, and Parker Solar Probe spacecraft as a newly considered impactor source at the Moon, we find β-meteoroid impacts to the lunar surface can explain the sunward asymmetry observed by LADEE/LDEX. We discuss these observations and how this finding suggests β-meteoroids may appreciably contribute to the evolution of other airless surfaces in the inner solar system.

How to cite: Szalay, J., Pokorný, P., Malaspina, D., Pusack, A., Horányi, M., DeLuca, M., Bale, S., Battams, K., Gasque, C., Goetz, K., Krüger, H., McComas, D., Schwadron, N., and Strub, P.: Collisional Evolution of the Inner Zodiacal Cloud: In-Situ observations from PSP and implications for Airless Body Surfaces, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10466, https://doi.org/10.5194/egusphere-egu22-10466, 2022.

EGU22-10957 | Presentations | PS5.1

Dust detection by antenna instruments with applications to the STEREO spacecraft 

Zoltan Sternovsky, Alessandro Garzelli, Mihaly Horanyi, David Malaspina, Petr Pokorny, and Antal Juhasz

Plasma Wave antenna instruments are employed on a range of space missions and can also be used to characterize the population of cosmic dust particles. Such measurements are complementary to those made by a dedicated dust instrument and suitable for the detection of larger (> 1 micron) particles. These booms or deployed wires with receiving elements are sensitive to the plasma cloud generated by the hypervelocity impact of a dust particle on the spacecraft, or the antenna itself. The dust impact is registered as a transient voltage signal (waveform) that is due to the charging of the spacecraft/antenna, and the induced charging from the part of the plasma cloud that is expanding from the impact location. Recent advancements provide the capability of obtaining the mass of the impacting particle from the measured waveforms. The new models are based on first principles and account for the parameters of the impact plasma (in terms of effective temperatures and the geometry of the expansion), the parameters of the ambient space environment, and the geometry of the spacecraft. The latter two allow for determining the approximate impact location on the spacecraft and thus constrain the incoming direction of the dust particle. Once the expansion of the transient impact plasma is over, the spacecraft and the antennas discharge through the ambient environment and relax back to their equilibrium potentials. The analysis of the measured waveforms thus also provides information on the density of the ambient plasma and its temperature. The numerical model is applied for the reanalysis of the measurements made by the STEREO spacecraft.

How to cite: Sternovsky, Z., Garzelli, A., Horanyi, M., Malaspina, D., Pokorny, P., and Juhasz, A.: Dust detection by antenna instruments with applications to the STEREO spacecraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10957, https://doi.org/10.5194/egusphere-egu22-10957, 2022.

EGU22-11250 | Presentations | PS5.1

Very long electric field disturbances induced by dust impact observed by the Solar Orbiter/RPW 

Michiko Morooka, Yuri Khotyaintsev, Milan Maksimovic, Jan Soucek, and David Pisa

Transient electric field perturbations are commonly observed when the interplanetary dust grains impact spacecraft, and their characteristics are well-studied. The signals are interpreted as due to the plasma expansion at the impact site and last typically in the order of micro-to milli-seconds. Radio and Plasma Wave (RPW) Instrument onboard Solar Orbiter can observe grains with a dedicated mode to capture such short-lived signals by the dust in the inner Heliosphere. On the other hand, a large impact can cause electric field disturbance for a longer time in tens of seconds. The long signals are observed in the low-frequency range (<10 kHz) and found more frequently during the inbound of the Solar Orbiter excursion. We will discuss the plasma and spacecraft conditions for the long durational impact signals.

How to cite: Morooka, M., Khotyaintsev, Y., Maksimovic, M., Soucek, J., and Pisa, D.: Very long electric field disturbances induced by dust impact observed by the Solar Orbiter/RPW, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11250, https://doi.org/10.5194/egusphere-egu22-11250, 2022.

EGU22-12123 | Presentations | PS5.1

Solar Orbiter SWA-PAS and SWA-HIS observations of O+ ions in the very distant tails of the comets C/2019 Y4(ATLAS) and C/2021 A1(Leonard) 

Andrey Fedorov, Stefano Livi, Philippe Louarn, Chris Owen, and Jim Raines
ESA solar observatory Solar Orbiter is expected to have flown close to a comet plasma tail two times during the mission cruise phase. It passed behind the comet C/2019 Y4(ATLAS) in the end of May 2020. The second chance occurred on December 2021 when Solar Orbiter has encountered the tail of C/2021 A1(Leonard). In the both cases the distance between the spacecraft and the comet nucleus was about 40 million km. At the time of the encounter the comet ATLAS was at just 0.3 AU from Sun, and in the second case the comet Leonard was at the Venus orbit (0.7 AU). In both cases SWA-PAS ion spectrometer has seen very clear signature of the pickup O+ ions (with the maximum at about solar wind velocity). We observed the flow of the cometary tail ions as rather sharp bursts on just several minutes of duration. The heavy ion mass-spectrometer HIS observed O+ ions (among other species of the cometary origin) during the Leonard's tail encounter. We used inter-calibrated data of both instruments to get the absolute O+ flux from both comets.

How to cite: Fedorov, A., Livi, S., Louarn, P., Owen, C., and Raines, J.: Solar Orbiter SWA-PAS and SWA-HIS observations of O+ ions in the very distant tails of the comets C/2019 Y4(ATLAS) and C/2021 A1(Leonard), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12123, https://doi.org/10.5194/egusphere-egu22-12123, 2022.

EGU22-12472 | Presentations | PS5.1

Search for the parent body of the recently fallen iron meteorite 

Oleksiy Golubov, Ihor Kyrylenko, Ivan Slyusarev, Jaakko Visuri, Maria Gritsevich, Yurij N. Krugly, Irina Belskaya, and Vasilij G. Shevchenko

On November 7, 2020, a bright fireball was observed over Sweden, and 13.8 kg iron meteorite was later recovered. Multiple observations of the fireball were conducted from Denmark, Finland, and Norway, making it the first instrumentally documented fall of an iron meteorite.

We used the instrumental recordings of the bolide to reconstruct its preatmospheric orbit, and studied the past orbital evolution of the meteoroid. We found no close affinity of the orbit of the meteoroid with any near-Earth asteroid. The long YORP timescale suggests that the meteoroid could have arrived intact from the main asteroid belt. Our analysis of the orbit shows that the meteoroid probably entered its near-Earth orbit via either the 𝜈6 secular resonance with Saturn or the 3:1 mean motion resonance with Jupiter.

The work was partially funded by the National Research Foundation of Ukraine (project N2020.02/0371).

How to cite: Golubov, O., Kyrylenko, I., Slyusarev, I., Visuri, J., Gritsevich, M., Krugly, Y. N., Belskaya, I., and Shevchenko, V. G.: Search for the parent body of the recently fallen iron meteorite, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12472, https://doi.org/10.5194/egusphere-egu22-12472, 2022.

EGU22-12609 | Presentations | PS5.1

Yarkovsky and YORP Effects: Theoretical Models, Observational Confirmations, and Implications for Asteroid Evolution 

Oleksiy Golubov, Daniel J. Scheeres, and Yurij N. Krugly

The Yarkovsky and YORP effects originate due to the light pressure recoil force acting on the surface of an asteroid. The Yarkovsky effect changes the asteroid's orbit, whereas the YORP effect changes its rotation state. Both effects appear to be crucially important for the long-term evolution of kilometer-sized asteroids.

The talk will review the recent successes and difficulties in the theoretical modeling of these effects, the growing body of their observational confirmations, and how these effects can alter asteroids' shapes, create binary asteroids and asteroid pairs, spread asteroid families and help asteroids to migrate from the main belt to the near-Earth orbits.

How to cite: Golubov, O., Scheeres, D. J., and Krugly, Y. N.: Yarkovsky and YORP Effects: Theoretical Models, Observational Confirmations, and Implications for Asteroid Evolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12609, https://doi.org/10.5194/egusphere-egu22-12609, 2022.

EGU22-12656 * | Presentations | PS5.1 | Highlight

The Comet Interceptor Mission 

Geraint Jones, Colin Snodgrass, and Cecilia Tubiana and the The Comet Interceptor Team

In 2019, Comet Interceptor was selected by the European Space Agency, ESA, as the first in its new class of F missions. The Japanese space agency, JAXA, is making a major contribution to the project. Comet Interceptor's primary science goal is to characterise for the first time, a yet-to-be-discovered long-period comet, preferably dynamically new, or an interstellar object. An encounter with a comet approaching the Sun for the first time will provide valuable data to complement information gathered by all previous comet missions, which through necessity all visited more evolved short period comets. The spacecraft will be launched in 2029 with the Ariel mission to the Sun-Earth Lagrange Point, L2. This relatively stable location allows a rapid response to the appearance of a suitable target comet, which will need to cross the ecliptic plane through an annulus centered on the Sun that contains Earth’s orbit. A suitable new comet would be searched for from Earth, with short period comets acting as mission backup targets. Powerful facilities such as the Vera Rubin Observatory make finding a suitable comet nearing the Sun very promising, and the spacecraft could encounter an interstellar object if one is found on a suitable trajectory. The spacecraft must cope with a wide range of target activity levels, flyby speeds, and encounter geometries. This flexibility has significant impacts on the spacecraft solar power input, thermal design, and dust shielding that can cope with dust impacts. Comet Interceptor comprises a main spacecraft and two probes, one provided by ESA, the other by JAXA, which will be released by the main spacecraft on approach to the target. The main spacecraft, which would act as the primary communication point for the whole constellation, would be targeted to pass outside the hazardous inner coma, making remote and in situ observations on the comet’s sunward side. Planned measurements of the target include its surface composition, shape, and structure, its dust environment, and the gas coma’s composition. A unique, multi-point ‘snapshot’ of the comet- solar wind interaction region will be obtained, complementing single spacecraft observations at other comets. We shall describe the science drivers, planned observations, and the mission’s instrument complement, to be provided by consortia of institutions in Europe and Japan.

How to cite: Jones, G., Snodgrass, C., and Tubiana, C. and the The Comet Interceptor Team: The Comet Interceptor Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12656, https://doi.org/10.5194/egusphere-egu22-12656, 2022.

EGU22-671 | Presentations | ST2.4

Causes of jets in the quasi-perpendicular magnetosheath 

Primoz Kajdic, Savvas Raptis, Xóchitl Blanco-Cano, and Tomas Karlsson

Magnetosheath jets are currently an important topic in the field of magnetosheath physics. It is thought that 97 % of the jets are produced by the shock rippling at quasi-parallel shocks. Recently, large statistical studies of magnetosheath jets have been performed, however it is not clear whether rippling also produces jets found downstream of quasi-perpendicular shocks. We analyze four types of events in the quasi-perpendicular magnetosheath with signatures characteristic of magnetosheath jets, namely increased density and/or dynamic pressure, that were not produced by the shock rippling: 1) magnetic flux tubes connected to the quasi-parallel bow-shock, 2) non-reconnecting current sheets, 3) reconnection exhausts and 4) mirror mode waves. The flux tubes are downstream equivalents of the upstream traveling foreshocks. Magnetosheath jets can impact the magnetopause, so knowing the conditions under which they form may enable us to understand their signatures in the magnetosphere.

How to cite: Kajdic, P., Raptis, S., Blanco-Cano, X., and Karlsson, T.: Causes of jets in the quasi-perpendicular magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-671, https://doi.org/10.5194/egusphere-egu22-671, 2022.

EGU22-901 | Presentations | ST2.4 | Arne Richter Award for Outstanding ECS Lecture

Ion dynamics in the inner magnetosphere during Van Allen Probe Era 

Chao Yue

Ion dynamics are controlled by the energy-dependent source, transport, energization, and loss processes. Systematic changes in the ion dynamics are essential to understand the ring current variations in the inner magnetosphere. The Van Allen Probes mission, which orbits near the equatorial plane inside the geosynchronous orbit, has a wide energy coverage with high energy resolution and state-of-the-art ion composition instrumentation. It provides a great opportunity to investigate plasma dynamics. In this talk, I will present some of our recent studies on the ion dynamics of different populations and species as well as the related plasma wave activity during geomagnetic quiet and active times.

How to cite: Yue, C.: Ion dynamics in the inner magnetosphere during Van Allen Probe Era, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-901, https://doi.org/10.5194/egusphere-egu22-901, 2022.

EGU22-1297 | Presentations | ST2.4 | Highlight

Molecular and metalic ions in the magnetosphere: ISSI team preliminary results 

Masatoshi Yamauchi, Iannis Dandouras, Ingrid Mann, Stein Haaland, Peter Würz, John Plane, Daniel Kastinen, Tinna Gunnarsdottir, Andrew Yau, Lynn Kistler, Doug Hamilton, Steve Christon, Yoshufumi Saito, Shigeto Watanabe, and Satonori Nozawa

Molecular and metallic ions are vastly unexplored in near-Earth space because only a few terrestrial missions have been equipped with dedicated instrumentation to separate these molecular and metallic ions, within only a limited energy range (cold ions of < 50 eV and energetic ions of ~100 keV).  Nevertheless, existing data from past and on-going missions including those not designed for the required mass separation are capable of detecting many of these ions with available tools, although severe limitations exist (sensitivity and energy range in addition to mass resolution and mass range).  By combining these patchy and incomplete data, we found several features that indicate sources of these heavy ions.
(1) Combination of Kaguya and Cluster/RAPID during high flux events of solar wind heavy ions suggests that the Moon can be a substantial source for low charge-state metallic ions in the magnetosphere when the Moon is located upstream of the Earth.  This interpretation is consistent with Geotail/STICS statistics of increased flux of low charge-state heavy ions near new-Moon for medium activity (Kp=2-4).
(2) The major route of molecular ion supply (<10 keV) to the inner magnetosphere can be via low-latitude (< 60° invariant latitude, according to e-POP/IRMS) in addition to the cusp (according to Cluster/CIS and Akebono/SMS) during high outflow flux period.  This indicates extraordinary upward convection (or ion flow) at the sub-auroral region.
(3) A case study of lidar data during high flux events of solar wind heavy ions suggests that upward expansion of Na signal can be associated with molecular ion escape to the magnetosphere that is also observed by Cluster/RAPID and e-POP/IRM, although this expansion can be related to a major magnetic storm rather than solar wind event.

How to cite: Yamauchi, M., Dandouras, I., Mann, I., Haaland, S., Würz, P., Plane, J., Kastinen, D., Gunnarsdottir, T., Yau, A., Kistler, L., Hamilton, D., Christon, S., Saito, Y., Watanabe, S., and Nozawa, S.: Molecular and metalic ions in the magnetosphere: ISSI team preliminary results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1297, https://doi.org/10.5194/egusphere-egu22-1297, 2022.

EGU22-1360 | Presentations | ST2.4

The foreshock wave activity under quasi radial magnetic field in lunar distances: Statistical study 

Anna Salohub, Jana Safrankova, and Zdenek Nemecek

We present a large statistical study of the ultra-low frequency (ULF) waves in the terrestrial foreshock. These waves are excited in the upstream region by energetic ions streaming along the solar wind magnetic field lines connected to the bow shock. Although these waves propagate upstream and grow in the solar wind frame, they are blown down by the solar wind flow and thus their amplitudes would grow toward the bow shock. In our previous study based on ARTEMIS observations, we demonstrated that the statistically determined growth rate is positive but also the cases of a wave decay are frequently observed. We have shown that even if a possible influence of the Moon and its wake is excluded, the growth rate is decreased by non-linear effects leading to a saturation of the wave amplitude. To eliminate this problem, we have selected intervals allowing identification of an initial stage of wave amplitude growth (either in spatial or temporal sense). Our study revealed that the growth rate depends on the wave type being larger for compressive variations of the magnetic field strength and plasma density than for variations of magnetic field components. The analogous study of velocity fluctuations leads to smaller growth rates and we discuss possible causes of this disagreement.

How to cite: Salohub, A., Safrankova, J., and Nemecek, Z.: The foreshock wave activity under quasi radial magnetic field in lunar distances: Statistical study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1360, https://doi.org/10.5194/egusphere-egu22-1360, 2022.

EGU22-1727 | Presentations | ST2.4 | Highlight

Similarities and differences of jet-like structures in different regions of the magnetosheath 

Oleksandr Goncharov, Jana Safrankova, Zdenek Nemecek, Niki Xirogiannopoulou, Olga Gutynska, Herbert Gunell, and Maria Hamrin

Plasma structures with the enhanced dynamic pressure, density or speed are often observed in the Earth’s magnetosheath. These structures, known as jets and fast plasmoids, can be registered in the magnetosheath, downstream both the quasi-perpendicular and quasi-parallel bow shocks. Using measurements by the Magnetospheric Multiscale (MMS) spacecraft, Goncharov et al. (2020) showed similarities in the plasma properties of the jets and fast plasmoids. On the other hand, they pointed out that the different magnetic fields inside the structures suggest that the formation mechanisms are different. Hybrid simulations by Preisser et al. (2020) have shown differences in the mechanisms of jet and embedded plasmoid formation. Based on our comparative analysis, we discuss features of jet-like structures, their properties, occurrence, evolution, and relation to the magnetosheath parameters.

How to cite: Goncharov, O., Safrankova, J., Nemecek, Z., Xirogiannopoulou, N., Gutynska, O., Gunell, H., and Hamrin, M.: Similarities and differences of jet-like structures in different regions of the magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1727, https://doi.org/10.5194/egusphere-egu22-1727, 2022.

EGU22-1745 | Presentations | ST2.4

Foreshock compressive structures and their relations to jet-like events in the magnetosheath 

Niki Xirogiannopoulou, Oleksandr Goncharov, Jana Safrankova, Zdenek Nemecek, and Anna Salohub

Plasma structures with enhanced density or dynamic pressure, also known as jets or plasmoids, are often observed in Earth’s magnetosheath. Early studies of jets in the magnetosheath have indicated that the jet formation is closely related to processes in the foreshock region. Based on the magnetic field changes, Karlsson et al. (2015) divided the plasmoids into two distinct groups. They observed numbers of “diamagnetic” plasmoids in the foreshock region and suggested that Short Large Amplitude Magnetic Structures (SLAMS) could be a source of both plasmoid types in the magnetosheath. Using measurements by the Magnetospheric Multiscale (MMS) spacecraft we present a statistical analysis of foreshock compressive structures with significantly enhanced density and dynamic pressure. Based on our statistical analysis and previous studies, we discuss features of those structures, their properties, occurrence, evolution, and relation to the magnetosheath jets and plasmoids.

How to cite: Xirogiannopoulou, N., Goncharov, O., Safrankova, J., Nemecek, Z., and Salohub, A.: Foreshock compressive structures and their relations to jet-like events in the magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1745, https://doi.org/10.5194/egusphere-egu22-1745, 2022.

EGU22-1800 | Presentations | ST2.4 | Highlight

AMPERE and The Electric Current of the Geomagnetic Storm 

Amy Fleetham, Steve Milan, Suzie Imber, and Brian Anderson

The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) has revolutionized the way in which we can study the electrical current systems present over the poles of Earth. With high cadence measurements taken in both hemispheres, the data has proven invaluable in developing our understanding of the current systems that couple the magnetosphere and ionosphere and how they change in response to space weather. By employing the AMPERE data set, we aim to offer new insights into the complex and dynamic region 1 and region 2 current systems as they respond to the impact of solar wind disturbances on the magnetosphere and the driving of geomagnetic storms.

We investigate the relationship between the hemispherically-integrated current flowing into or out of each pole and upstream solar wind parameters to understand how these currents are driven.  As expected, current magnitude increases with increasing interplanetary magnetic field strength and solar wind speed.  A key aim of the analysis is to determine if current magnitude saturates under strongly driven conditions, in the same way that the cross-polar cap potential is known to saturate.  We present preliminary results, indicating a variety of behaviours at high driving, and discuss these in terms of theories of solar wind-magnetosphere coupling.

How to cite: Fleetham, A., Milan, S., Imber, S., and Anderson, B.: AMPERE and The Electric Current of the Geomagnetic Storm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1800, https://doi.org/10.5194/egusphere-egu22-1800, 2022.

EGU22-1976 | Presentations | ST2.4 | Highlight

Magnetotail Ion Structuring by Kinetic Ballooning-Interchange Instability 

Evgeny V. Panov, San Lu, and Philip L. Pritchett

By combining three-probe THEMIS observations and 3-D Particle-in-Cell simulations, we identify key structures on the ion gyroradius scale that occur in connection with ballooning-interchange instability (BICI) heads in the Earth’s magnetotail. The mesoscale structures occur at sites of strong ion velocity shear and vorticity where the thermal ion Larmor radius is about half of the width of the head. Finer structures occur at the smaller scales characterizing the wavelength of the electromagnetic ion cyclotron waves generated at the heads. These two processes act to erode and thin the current sheet, thereby forming a local magnetotail configuration that is favorable for reconnection.

How to cite: Panov, E. V., Lu, S., and Pritchett, P. L.: Magnetotail Ion Structuring by Kinetic Ballooning-Interchange Instability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1976, https://doi.org/10.5194/egusphere-egu22-1976, 2022.

EGU22-2347 | Presentations | ST2.4

Parameter estimation using Cluster array magnetic field data: perfomance and limits of Capon's method 

Yasuhito Narita, Simon Toepfer, Karl-Heinz Glassmeier, and Uwe Motschmann

Finding a set of model parameters using the in-situ spacecraft data (such as in the Earth or planetary magnetospheres and in the solar wind) is one of the common exercises in the field of space physics. Above all, parameter estimation using Capon's minimum variance projection, originally developed in the field of array seismology, has successfully been applied to recognizing various structures or spatial patterns in space. Examples of the Capon method can be found in the analysis of the wave structures (plane waves, spherical waves, and phase-shifted waves) and the static, large scale structures (planetary dipolar field and higher-order fields). In order to extend the scientific potential of array magnetic field data such as the Cluster, THEMIS, and MMS missions, the performance and the limits of Capon's method are studied in detail using both analytical and numerical approaches. Our findings are: 1) Capon's method is a simple yet robust implementation of the maximum likelihood method, and 2) its accuracy or error can be evaluated analytically. It is suggested that other inversion techniques such as the least square fitting, the singular value decomposition, the Tikhonov regularization, and the eigenvector-based method may be as competitive as Capon's method when the statistical method is limited in the data analysis. Data analysts have thus a wider range of choices for the structure recognition using array data. 

How to cite: Narita, Y., Toepfer, S., Glassmeier, K.-H., and Motschmann, U.: Parameter estimation using Cluster array magnetic field data: perfomance and limits of Capon's method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2347, https://doi.org/10.5194/egusphere-egu22-2347, 2022.

EGU22-2575 | Presentations | ST2.4

The Mie representation for Mercury‘s magnetospheric currents 

Simon Töpfer, Yasuhito Narita, Daniel Heyner, Patrick Kolhey, Karl-Heinz Glassmeier, and Uwe Motschmann

Poloidal–toroidal magnetic field decomposition is a useful application of the Mie representation for the reconstruction of Mercury‘s internal magnetic field. In addition, the decomposition method enables us to determine the current density observationally and unambiguously in the local region of magnetic field measurement. The application and the limits of the decomposition method are tested against the Mercury magnetic field simulation in view of BepiColombo‘s arrival at Mercury in 2025. The simulated magnetic field data are evaluated along the planned Mercury Planetary Orbiter (MPO) trajectories and the current system that is crossed by the spacecraft is extracted from the magnetic field measurements. Afterwards, the resulting currents are classified in terms of the established current system in the vicinity of Mercury.

 

Reference

  • Toepfer, S., Narita, Y., Exner, W., Heyner, D., Kolhey, P., Glassmeier, K. ‐H., Motschmann, U. (2021c)  The Mie representation for Mercury’s magnetospheric currents, Earth, Planets and Space 73:204. https://doi.org/10.1186/s40623-021-01536-8
  • Toepfer, S., Narita, Y., Glassmeier, K.-H., Heyner, D., Kolhey, P., Motschmann, U., Langlais, B. (2021a) The Mie representation for Mercury’s magnetic field, Earth Planets Space 73:65. https://doi.org/10.1186/s40623-021-01386-4

 

 

How to cite: Töpfer, S., Narita, Y., Heyner, D., Kolhey, P., Glassmeier, K.-H., and Motschmann, U.: The Mie representation for Mercury‘s magnetospheric currents, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2575, https://doi.org/10.5194/egusphere-egu22-2575, 2022.

EGU22-2750 | Presentations | ST2.4

High-speed Magnetosheath Jet Generation due to Shock Reformation 

Savvas Raptis, Tomas Karlsson, Andris Vaivads, Craig Pollock, Ferdinand Plaschke, Andreas Johlander, Henriette Trollvik, and Per-Arne Lindqvist

Magnetosheath jets are transient localized structures of enhanced dynamic pressure observed downstream of the Earth’s bow shock. They may exhibit an increase of velocity reaching solar wind levels, while their density is typically much higher than typical magnetosheath and solar wind values. Jets have been associated to several magnetospheric effects such as, magnetopause reconnection, excitations of surface eigenmodes and even direct plasma penetration in the magnetosphere. While their exact origin is unknown, many mechanisms have been proposed. One of the most prominent explanations involves the interaction of solar wind with local inclinations of the bow shock (ripples) while others include solar wind discontinuities, and foreshock structures.

In this work, by using Magnetosphere Multiscale (MMS) we show in-situ observations of a super-magnetosonic magnetosheath jet being generated as a direct result of the bow shock reformation cycle. The observed jet origin appears to be the result of the dynamical evolution of the shock and the emergence of a spatially de-attached compressive magnetic structure that acts as a local shock front. Due to this, the solar wind particles are effectively transferred downstream without experiencing a strong interaction with the shock, which allows compressed high velocity plasma to be observed downstream of the bow shock.

The proposed mechanism does not require external phenomena (e.g., solar wind discontinuities) or specific configuration of the bow shock (e.g., ripples) to take place. On the contrary, it allows the magnetosheath jet phenomenon to directly originate from the dynamical evolution of the quasi-parallel collisionless shock.

How to cite: Raptis, S., Karlsson, T., Vaivads, A., Pollock, C., Plaschke, F., Johlander, A., Trollvik, H., and Lindqvist, P.-A.: High-speed Magnetosheath Jet Generation due to Shock Reformation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2750, https://doi.org/10.5194/egusphere-egu22-2750, 2022.

EGU22-3219 | Presentations | ST2.4

Ion Acceleration at the Quasi-Parallel Shock: The Source Distributions of the Diffuse Ions 

Karlheinz Trattner, Stephen Fuselier, Steven Schwartz, Harald Kucharek, James Burch, Robert Ergun, Steven Petrinec, and Hadi Madanian

The terrestrial bow shock is the boundary between the supersonic solar wind and the terrestrial magnetosphere and converts the kinetic energy of the solar wind into thermal energy, allowing the flow to become subsonic and move past the magnetosphere. Shocks are an important acceleration site for ions and electrons in collisionless plasmas and responsible for much of the particle acceleration in solar, planetary, and astrophysical regions. One of the fundamental outstanding questions of ion acceleration at the quasi-parallel bow shock is which portion of the incoming solar wind ion distribution ultimately becomes the seed population that is subsequently accelerated to high energies.

This talk focuses on distribution functions of protons and alpha particles observed by the HPCA and FPI instruments onboard the MMS satellites during an MMS crossing of the quasi-parallel bow shock. The bow shock transition from the downstream region into the upstream solar wind shows the presence of specularly reflected ions and a distribution at 90 degree pitch angle ions in the shock ramp consistent with shock drift accelerated ions.

How to cite: Trattner, K., Fuselier, S., Schwartz, S., Kucharek, H., Burch, J., Ergun, R., Petrinec, S., and Madanian, H.: Ion Acceleration at the Quasi-Parallel Shock: The Source Distributions of the Diffuse Ions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3219, https://doi.org/10.5194/egusphere-egu22-3219, 2022.

EGU22-3297 | Presentations | ST2.4 | Highlight

Azimuthal and latitudinal changes of the near-Earth magnetotail current sheet structure during multiple dipolarizations of a substorm 

Rumi Nakamura, James Slavin, Daniel Schmid, and Weijie Sun and the The April 10, 2020 BepiColombo Earthflyby Substorm Study Team

Using data from fleet of spacecraft in the near-Earth night-side magnetosphere, we study the three-dimensional evolution of the magnetotail current sheet following the expansion phase onset of a moderate substorm (AL ~-450 nT) after 09:10 UT, April 10, 2020.  Magnetotail disturbances are observed by GOES 17 and Cluster in the midnight region.  During this substorm the BepiColombo spacecraft traversed the premidnight region duskward at 9-11 RE downtail during its Earth Flyby.  The four Cluster satellites, which were separated mainly in north-south direction, crossed the inner magnetosphere successively from north to south. They enable us to monitor the vertical (latitudinal) structure and the sequential changes of the magnetotail current sheet until the end of the recovery phase of the substorm, around 11 UT.  Multiple dipolarizations and multiple transient field-aligned currents (FAC) were observed by Cluster.  The first dipolarization around the onset, which was detected by GOES 17 in the geosychronous region, was accompanied by a plasma sheet expansion observed by the two leading Cluster 3 and 4 satellites. BepiColombo in the premidnight region observed continuous thinning of the current sheet, a typical signature of the growth phase, accompanied by a couple of transient magnetic signatures indicating flux rope and/or TCR formation around the onset.  Cluster 1 detected the most intense FAC associated with the dipolarization event starting around 10 UT, when the two BepiColombo MPO and MIO spacecraft observed dipolarization and energetic particle injection. These observations indicate the duskward and tailward expansion in the course of multiple dipolarizations.  Using the unique dataset from the multi-point observations, we examine the structure of the large-scale current sheet and analyze the embedded transient intense field-aligned current disturbances. By also comparing with an empirical magnetic field model, we obtain the changes of the near-Earth magnetotail structure during the multiple dipolarization event.

How to cite: Nakamura, R., Slavin, J., Schmid, D., and Sun, W. and the The April 10, 2020 BepiColombo Earthflyby Substorm Study Team: Azimuthal and latitudinal changes of the near-Earth magnetotail current sheet structure during multiple dipolarizations of a substorm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3297, https://doi.org/10.5194/egusphere-egu22-3297, 2022.

EGU22-3486 | Presentations | ST2.4 | Highlight

20 Years of Cluster Observations: The Magnetopause 

Stein Haaland, Hiroshi Hasegawa, Goetz Paschmann, Bengt Sonnerup, and Malcolm Dunlop

The terrestrial magnetopause forms the boundary between the solar wind plasma with its embedded interplanetary magnetic field on one side, and the terrestrial magnetosphere, dominated by Earth's dipole field, on the other side. It is therefore a key region for the transfer of mass, momentum, and energy from the solar wind to the magnetosphere. The Cluster mission, comprising a constellation of four spacecraft flying in formation was launched more than 20 years ago to study boundaries in space. During its lifetime, Cluster has provided a wealth of new knowledge about the magnetopause. In this presentation, we give an overview of Cluster-based studies of this boundary, and highlight a selection of interesting results. 

How to cite: Haaland, S., Hasegawa, H., Paschmann, G., Sonnerup, B., and Dunlop, M.: 20 Years of Cluster Observations: The Magnetopause, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3486, https://doi.org/10.5194/egusphere-egu22-3486, 2022.

EGU22-3519 | Presentations | ST2.4 | Highlight

Heavy Metal and Rock in Space: Cluster RAPID Observations 

Stein Haaland, Patrick W. Daly, Esa Vilenius, and Patrik Krcelic

Metallic and silicate ions carry essential information about the evolution of the Earth and near-Earth small bodies. Despite this, there has so far been very little focus on ions with atomic masses higher than oxygen in the terrestrial magnetosphere. In this presentation, we report on abundances and  properties of energetic ions with masses corresponding to that of silicon (Si) and iron (Fe) in Earth's geospace.  The results are based on a newly derived data product from the Research with Adaptive Particle Imaging Detectors (RAPID) on Cluster. We find traces of both Si and Fe in all of the regions covered by the spacecraft, with the highest occurrence rates and highest intensities in the inner magnetosphere. We also find that the Fe and Si abundances are modulated by solar activity. During solar maximum, the probability of observing Fe and Si in geospace increases significantly. On the other hand, we find little or no direct correlation between geomagnetic activity and Si and Fe abundance in the magnetosphere. Both Si and Fe in the Earth's magnetosphere are inferred to be primarily of solar wind origin, as indicated by correlations with heavy ion observations from the ACE spacecraft at L1. Sputtering off the Moon is another possible source of the observed heavy ions.

How to cite: Haaland, S., Daly, P. W., Vilenius, E., and Krcelic, P.: Heavy Metal and Rock in Space: Cluster RAPID Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3519, https://doi.org/10.5194/egusphere-egu22-3519, 2022.

EGU22-4018 | Presentations | ST2.4

Revisiting the wave telescope for larger numbers of spacecraft 

Leonard Schulz, Karl-Heinz Glassmeier, Ferdinand Plaschke, and Uwe Motschmann

The strong growth of the space sector along with the use of smaller satellites, for example Cubesats, has fueled the rising implementation of satellite constellations. Not only in commercial spaceflight small satellite constellations are used frequently - there also have been ideas put forward for scientific missions using constellations exceeding the 4 spacecraft constellations previously used for in-situ multi-point measurements in space plasma physics (e.g. CLUSTER or MMS). Thus, there is a need to expand current analysis techniques of those multi-point measurements to more than 4 spacecraft and characterize the benefits of a larger number of satellites. Such an analysis technique is the wave telescope, e.g. introduced in Motschmann et al., 1996. The wave telescope allows to use e.g. magnetic field data from different points in space (the different spacecraft) to estimate a spatial fourier transform and with that is able to detect multiple waves. Thus, using a confined time interval, the frequency and wave vector of several different waves can be detected with high precision. Since its introduction, the wave telescope has been successfully applied for detection of waves in in-situ magnetic field data from Earth's magnetospheric environment. Using artificial data of magnetic plane waves in simulations, we revisit the limitations of the wave telescope for satellite numbers of 4 or less and explore the quality of detection for satellite configurations of 5 and more spacecraft. We present structured analysis of the spatial analysis limit from 1D upwards, named the nyquist wavenumber or wave vector (analogous to the nyquist frequency in the frequency domain). Additionally, we show that the wave telescope suffers from so called spatial blindness when the chosen satellite configuration is not moving and non-random phase plane waves at the same frequency are present. This blindness reduces the possible number of waves detected to no more than one.

How to cite: Schulz, L., Glassmeier, K.-H., Plaschke, F., and Motschmann, U.: Revisiting the wave telescope for larger numbers of spacecraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4018, https://doi.org/10.5194/egusphere-egu22-4018, 2022.

EGU22-4045 | Presentations | ST2.4

Ion Acceleration at Magnetotail Turbulent Plasma Jet Fronts 

Louis Richard, Yuri V. Khotyaintsev, Daniel B. Graham, Andris Vaivads, Romina Nikoukar, Ian J. Cohen, Drew L. Turner, Stephen A. Fuselier, Christopher T. Russell, Barbara L. Giles, and Per-Arne Lindqvist

We investigate a series of Earthward bursty bulk flows (BBFs) observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth’s magnetotail (X ~ -24 Re, Y ~ 7 Re, Z ~ 4 Re). At the leading edges of the BBFs, we observe complex magnetic field structures. In particular, we focus on one which presents a chain of small scale (~0.5 Re) dipolarizations, and another with a large scale (~3.5 Re) dipolarization. Although the two structures have different scales, both of these structures are associated with flux increases of supra-thermal ions (Ki > 100 keV). We investigate the ion acceleration mechanism and its dependence on the mass and charge state. We show that the ions with gyroradii smaller than the scale of the structure are accelerated by the ion bulk flow. We show that whereas in the small-scale structure, ions with gyroradii comparable with the scale of the structure undergo resonance acceleration, the acceleration in the larger-scale structure is more likely due to a spatially limited electric field. In both cases, we discuss the adiabaticity of the acceleration mechanism.

How to cite: Richard, L., Khotyaintsev, Y. V., Graham, D. B., Vaivads, A., Nikoukar, R., Cohen, I. J., Turner, D. L., Fuselier, S. A., Russell, C. T., Giles, B. L., and Lindqvist, P.-A.: Ion Acceleration at Magnetotail Turbulent Plasma Jet Fronts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4045, https://doi.org/10.5194/egusphere-egu22-4045, 2022.

EGU22-4134 | Presentations | ST2.4 | Highlight

Statistics of broadband low-frequency waves at the magnetopause 

Konrad Steinvall, Yuri Khotyaintsev, and Daniel Graham

Broadband waves near and below the lower-hybrid frequency have been observed at the magnetopause for a long time. In recent years NASA's multi-spacecraft mission Magnetospheric Multiscale (MMS) has enabled the waves to be analysed in much greater detail.
Previous case studies have shown that these waves can cause plasma diffusion across the magnetopause, leading to the broadening of current layers. It has also been argued that the waves might contribute to parallel electron heating and anomalous resistivity.

In this study we analyze the aforementioned waves at the magnetopause using multi-spacecraft analysis methods and data from the MMS mission. We investigate the properties of these waves on a statistical level, using several months of data. In particular, we present the relation between the waves and ambient plasma properties such as density gradients and the corresponding gradient length-scale, and to magnetic reconnection.

How to cite: Steinvall, K., Khotyaintsev, Y., and Graham, D.: Statistics of broadband low-frequency waves at the magnetopause, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4134, https://doi.org/10.5194/egusphere-egu22-4134, 2022.

EGU22-4400 | Presentations | ST2.4

Electron Kinetic Entropy Generation at Quasi-perpendicular Collisionless Shocks: Dependence on Shock Parameters 

Martin Lindberg, Andris Vaivads, Savvas Raptis, Per-Arne Lindqvist, Barbara Giles, and Daniel Gershman

We calculate the change in electron kinetic entropy, ΔSe, across 22 supercritical quasi-perpendicular Earth bow shock crossings observed by the Magnetospheric Multiscale (MMS) mission. The crossings cover a wide range of shock parameters. We calibrate the measured distribution functions measured by MMS to correct for spacecraft potential, secondary electron contamination, lack of measurements at the lowest energies and electron density measurements based on the plasma frequency measurements. The change in electron kinetic entropy displays a strong dependence on the change in electron temperature, ΔTe, and the upstream plasma beta. Shocks with a small upstream plasma beta have a large ΔSe while shocks with high upstream plasma beta have a small ΔSe.

The calculated changes in kinetic entropy, density and temperature are used to estimate the proxy adiabatic index, γe, for each shock crossing. The estimated adiabatic indices are all in the vicinity of 1.6, comparable to that of a monatomic gas with three degrees of freedom.

How to cite: Lindberg, M., Vaivads, A., Raptis, S., Lindqvist, P.-A., Giles, B., and Gershman, D.: Electron Kinetic Entropy Generation at Quasi-perpendicular Collisionless Shocks: Dependence on Shock Parameters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4400, https://doi.org/10.5194/egusphere-egu22-4400, 2022.

EGU22-4579 | Presentations | ST2.4

EMHD Grad–Shafranov reconstruction of the electron diffusion region within a flux rope 

Daniil Korovinskiy, Evgeny Panov, Rumi Nakamura, and Martin Hosner

The compressible electron magnetohydrodynamics (EMHD) Grad–Shafranov (GS) reconstruction technique is applied to recover a magnetic reconnection electron diffusion region (EDR) immersed in a flux‐rope type dipolarization front observed by the Magnetospheric Multiscale (MMS) mission on 8 September 2018 at nearly 14:51:30 UT. An event was reported in the study of Marshall et al. (JGR, 2020). EMHD GS reconstruction confirms mainly the results of the cited study. Particularly, MMS1 is found to cross the very center of EDR at the initial steady-state stage. The reconstruction results allow also the suggestion that the reported X-line and EDR were not single ones, but rather the chain of X-lines (two at least) separated in north-south direction for about 10 de could exist.

How to cite: Korovinskiy, D., Panov, E., Nakamura, R., and Hosner, M.: EMHD Grad–Shafranov reconstruction of the electron diffusion region within a flux rope, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4579, https://doi.org/10.5194/egusphere-egu22-4579, 2022.

EGU22-5337 | Presentations | ST2.4

Kinetic generation of whistler waves in the turbulent magnetosheath 

Ida Svenningsson, Emiliya Yordanova, Yuri Khotyaintsev, Mats André, and Giulia Cozzani

Whistler waves, right-hand polarized waves with frequencies below the electron cyclotron frequency, are common in many space plasma regions such as the Earth’s magnetosheath. They can be generated by electron temperature anisotropy, in which case the instability grows through cyclotron resonance. A common way to determine the stability of an electron distribution function is to compare the parallel and perpendicular temperature (with respect to the background magnetic field) to stability thresholds. However, such an approach based on the moments of the distribution function can potentially leave out some properties of the distribution which are important for wave generation.

In this work, we investigate the features of the electron distribution functions measured by MMS in the turbulent magnetosheath downstream of a quasi-parallel shock. We show that even though statistically whistler waves tend to occur close to the regions where the stability threshold is exceeded, they are also observed in regions predicted to be stable to wave generation. For such waves we observe that the electron pitch angle distribution often has the so-called butterfly shape (with minima in both the parallel and perpendicular directions) and is located in magnetic field minima. Using a linear numerical dispersion solver (WHAMP), we show that the butterfly distribution is unstable to whistler wave generation even though the instability threshold based on the associated moments is not exceeded. Comparison between the numerical results and waves measured by the MMS spacecraft indicate that the observed whistler waves are generated by the butterfly distribution. This phenomenon has previously been observed in mirror modes and large scale magnetic holes. Our findings show that it also occurs on smaller scales (~1 ion inertial length) in more turbulent environments, such as the quasi-parallel magnetosheath.

How to cite: Svenningsson, I., Yordanova, E., Khotyaintsev, Y., André, M., and Cozzani, G.: Kinetic generation of whistler waves in the turbulent magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5337, https://doi.org/10.5194/egusphere-egu22-5337, 2022.

EGU22-5853 | Presentations | ST2.4

Investigation of the evolution of energy conversion processes at an EDR-accompanied dipolarization front, using polynomial magnetic field reconstruction techniques 

Martin Hosner, Rumi Nakamura, Daniel Schmid, Takuma Nakamura, Evgeny Panov, and Daniil Korovinskiy

The Dipolarization Front (DF), which is a sharp increase of the northward magnetic field component, accompanied by fast earthward-moving plasma flows, is a well known phenomenon in the Earth's Magnetotail. Plasma characteristics also change at the front, from colder and denser ahead of the front to a hotter and more diluted plasma at the trailing side. The DF is therefore considered to be the boundary between ambient plasma and the hotter reconnection outflow jets. The DF can be the host of several energy conversion processes between plasma particles and waves e.g. due to various instabilities. A recent statistical study by Hosner et al. PoP 2022 showed that all of the studied DFs are accompanied by enhanced wave activity around the lower hybrid frequency, suggesting the high occurrence of the Lower-Hybrid Drift instability (LHDI) at DFs. In the present study we investigate the evolution of the energy conversion process in a flux rope type DF, for which an electron-diffusion region was reported (Marshall et al. JGR 2020). We first examine the wave characteristics and LHDI signatures to compare and to contrast flux rope and non-flux rope type DFs. Secondly, we apply a magnetic field reconstruction technique (Denton et al. JGR 2020) to this event using MMS data, to reconstruct the changes of the local magnetic field structures of the flux rope and temporal/spatial evolution of the energy conversion processes within the DF.

How to cite: Hosner, M., Nakamura, R., Schmid, D., Nakamura, T., Panov, E., and Korovinskiy, D.: Investigation of the evolution of energy conversion processes at an EDR-accompanied dipolarization front, using polynomial magnetic field reconstruction techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5853, https://doi.org/10.5194/egusphere-egu22-5853, 2022.

EGU22-6366 | Presentations | ST2.4 | Highlight

Uncertainty in solar wind propagation may explain polar cap potential saturation 

Nithin Sivadas, David Sibeck, Varsha Subramanyan, Maria-Theresia Walach, Kyle Murphy, and Alexa Halford

The polar cap potential, a measure of the magnetosphere's response to the solar wind, levels off during high solar wind electric field values. Several explanations have been proposed for this saturation effect, but there has been no consensus. We show that the saturation may merely be a perception created by uncertainty in the solar wind measurements and its propagation to the polar cap. Correcting this uncertainty reveals a true response that is linear across the full range of the solar wind electric field values. These findings indicate that extreme space weather events can elicit a larger impact on Earth than we'd expect if the polar cap potential were to saturate.

How to cite: Sivadas, N., Sibeck, D., Subramanyan, V., Walach, M.-T., Murphy, K., and Halford, A.: Uncertainty in solar wind propagation may explain polar cap potential saturation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6366, https://doi.org/10.5194/egusphere-egu22-6366, 2022.

EGU22-6459 | Presentations | ST2.4 | Highlight

Electron earthward transport in the Earth magnetotail: adiabatic convection heating and magnetic curvature scattering 

Pavel Shustov, Anton Artemyev, and Anatoliy Petrukovich

The near-Earth electron population is largely formed by earthward electron transport from the middle and distant magnetotail. Such transport is associated by electron adiabatic heating by the convection electric field. Although the adiabatic heating models predict formation of strongly anisotropic electron populations, spacecraft observations show that hot electrons are well isotropic in the near-Earth magnetotail. One of the possible isotropisation mechanisms is the electron scattering by magnetic field line curvature in the magnetotail current sheet with the stretched magnetic field line configuration.  In this presentation we show model results of electron transport and curvature scattering for slow magnetosphere convection. Our model combines the canonical theory of the electron guiding center motion and the mapping technique of electron pitch-angle scattering. We show formation of electron spectra typical for the near-Earth magnetotail and estimate the contribution of the curvature scattering to electron losses.

How to cite: Shustov, P., Artemyev, A., and Petrukovich, A.: Electron earthward transport in the Earth magnetotail: adiabatic convection heating and magnetic curvature scattering, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6459, https://doi.org/10.5194/egusphere-egu22-6459, 2022.

EGU22-6521 | Presentations | ST2.4

Solar wind conditions suppressing the production of magnetosheath jets during CME occurrence 

Florian Koller, Ferdinand Plaschke, Luis Preisser, Manuela Temmer, and Owen W. Roberts

Magnetosheath jets are dynamic pressure enhancements frequently observed in the Earth’s magnetosheath. They are significant coupling elements between the solar wind and the magnetosphere of the Earth and they can be geoeffective. Jets travel anti-sunward through the magnetosheath and can impact the magnetopause. The generation of these jets is generally linked to processes at the quasi-parallel bow shock and the foreshock. We analyzed how the appearance of these jets is linked to large-scale solar wind (SW) structures, in particular coronal mass ejections (CMEs) and stream interaction regions (SIRs) and their associated high speed streams (HSSs). In our statistical analysis, we use magnetosheath jets detected by the THEMIS spacecraft between 2008 to 2020. We found that the number of detected jets is lower during the passing of CMEs. Significantly more jets are observed during SIRs and HSSs. We analyze the difference in conditions during each SW structure and compare them to the SW conditions measured during the detection of jets. We focus on SW Alfvénic Mach number and IMF cone angle, which affect the presence of the foreshock and the position of the quasi-parallel shock front. We find that jets are unlikely to appear during a mix of low Alfvénic Mach numbers and high cone angles, which are SW conditions often found during CMEs and their associated sheaths.

How to cite: Koller, F., Plaschke, F., Preisser, L., Temmer, M., and Roberts, O. W.: Solar wind conditions suppressing the production of magnetosheath jets during CME occurrence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6521, https://doi.org/10.5194/egusphere-egu22-6521, 2022.

EGU22-6554 | Presentations | ST2.4

The IMF BZ Dependence of Cusp-Aligned Arcs 

Simon Thor, Anita Kullen, and Lei Cai

Occasionally, the auroral oval is filled with arcs pointing from the night side towards the cusp. These aurorae are known as cusp-aligned arcs. While there have been some theoretical predictions about their origins, the cause of these arcs remains unknown. For this study, we have identified both cusp-aligned arcs and regular transpolar arcs from DMSP satellite data. We investigate the correlation between the appearance of cusp-aligned arcs and various solar wind parameters, with a focus on IMF BZ and solar wind velocity. These results are then compared to the occurrence of regular transpolar arcs with respect to the same parameters. We see that cusp-aligned arcs appear almost exclusively when the IMF is northward for a long period of time, contrary to regular transpolar arcs which can have a varying, but typically northward on average, IMF. This result is in agreement with previous studies. No clear correlation between the solar wind velocity and cusp-aligned arc occurrence frequency can be seen. The results indicate that cusp-aligned arcs might be caused by Kelvin-Helmholtz instabilities at the flanks, as has been previously suggested. We also discuss other potential causes and models of cusp-aligned arcs in further detail. Additionally, we investigate the conjugacy of cusp-aligned arcs, based on DMSP data.

How to cite: Thor, S., Kullen, A., and Cai, L.: The IMF BZ Dependence of Cusp-Aligned Arcs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6554, https://doi.org/10.5194/egusphere-egu22-6554, 2022.

EGU22-6812 | Presentations | ST2.4

The early-phase growth of ULF waves in the ion foreshock observed in a hybrid-Vlasov simulation 

Kun Zhang, Seth Dorfman, Lucile Turc, Urs Ganse, Chen Shi, and Minna Palmroth

Large-amplitude ULF waves are usually observed in the foreshock region ahead of quasi-parallel shocks and their generation is driven by the backstreaming ions. In the early phase of the wave growth, the waves are growing with time and traveling in space simultaneously. Therefore, it is very difficult to observe the wave growth properly using single-point measurements such as single spacecraft observations, because the spatial and temporal variations cannot be decoupled. This has also brought difficulties into understanding the detailed physical connection between the foreshock ion properties and the wave properties. In comparison, it is more straightforward to study this problem in global simulations, as simulation results are available everywhere in the foreshock at all times. Here we perform detailed analysis of the ULF wave growth and its relationship with the ion distribution using a Vlasiator simulation (a hybrid-Vlasov code). We calculate the phase speed of the ULF waves and observe the wave growth in the wave frame continuously. We show that the growth rate of the ULF waves decreases with time due to the decrease in beam velocity and the scatter of the ion distribution. And we compare the calculated growth rate with the dispersion relation solved by LEOPARD (a dispersion solver with arbitrary ion distribution input) based on the corresponding ion distribution obtained from the simulation results, and we will discuss the related physical mechanisms such as the ion-ion beam instability when the wave growth can be explained by ion distribution and discuss possible reasons when there is any discrepancy.

How to cite: Zhang, K., Dorfman, S., Turc, L., Ganse, U., Shi, C., and Palmroth, M.: The early-phase growth of ULF waves in the ion foreshock observed in a hybrid-Vlasov simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6812, https://doi.org/10.5194/egusphere-egu22-6812, 2022.

EGU22-7655 | Presentations | ST2.4 | Highlight

Transmission of foreshock waves through the Earth’s magnetosheath 

Lucile Turc, Owen Roberts, Daniel Verscharen, Andrew Dimmock, Primoz Kajdic, Minna Palmroth, Yann Pfau-Kempf, Andreas Johlander, Maxime Dubart, Emilia Kilpua, Jan Soucek, Kazue Takahashi, Naoko Takahashi, Markus Battarbee, and Urs Ganse

The foreshock, extending upstream of the quasi-parallel shock and populated with shock-reflected particles, is home to intense wave activity in the ultra-low frequency range. The most commonly observed of these waves are the "30-second" waves, fast magnetosonic waves propagating sunward in the plasma rest frame, but carried earthward by the faster solar wind flow. These waves are thought to be the main source of Pc3 magnetic pulsations (10 – 45 s periods) in the dayside magnetosphere, but how the waves can transmit through the bow shock and across the magnetosheath remains unclear. Global hybrid-Vlasov simulations performed with the Vlasiator model provide us with the global view of foreshock wave transmission across near-Earth space. We find that the foreshock waves act as fast-mode pulses hammering periodically the shock, which impulsively sends perturbations in the downstream at the fast-mode speed. These fast-mode disturbances propagate in the magnetosheath all the way to the magnetopause, where they can further transmit into the dayside magnetosphere. The wave propagation across the bow shock appears to be much more complex than the simple "direct transmission" of the foreshock waves which was inferred in early studies. This is due to the complex two-way interactions between the waves and the shock, including shock reformation. We compare our global simulation results with local 1D simulations, and we show that the wave signatures in the downstream strongly depend on the global properties of the shock-magnetosheath system. This emphasises the importance of carrying out global simulations in this context.

How to cite: Turc, L., Roberts, O., Verscharen, D., Dimmock, A., Kajdic, P., Palmroth, M., Pfau-Kempf, Y., Johlander, A., Dubart, M., Kilpua, E., Soucek, J., Takahashi, K., Takahashi, N., Battarbee, M., and Ganse, U.: Transmission of foreshock waves through the Earth’s magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7655, https://doi.org/10.5194/egusphere-egu22-7655, 2022.

EGU22-8347 | Presentations | ST2.4

Charge Separations in the Geomagnetosphere 

Chao Shen, Lai Gao, Yufei Zhou, Yong Ji, Zuyin Pu, Chris T. Russell, C. Philippe Escoubet, Yulia V. Bogdanova, Gang Zeng, Roy Torbert, and Jame L. Burch

Charges and electric currents source the electromagnetic field, and therefore the distribution and motions of charges determine its form. Charge separations may appear in various plasma boundary layers due to the inertia of electrons and ions or the trapping of the magnetic field. Based on the electric fields observed by MMS four spacecraft, the gradient of the electric field, as well as the charge density, can be obtained. The analysis on the electric field data acquired during dayside magnetopause crossing events by the MMS constellation shows a charge separation in the magnetopause boundary layer and that the positive charges are accumulated on the magnetospheric side while the negative charges are accumulated on the magnetosheath side. The charge separations in dayside, dawn side and dusk side magnetopause have been systematically explored. Furthermore, the spatial distribution of electric charge density in the inner magnetosphere is derived and analyzed based on the electric field measurements from September 2015 to December 2020 by MMS satellites. It is revealed that, the inner magnetosphere accumulates positive charge at dusk side and negative charge at dawn side, both of which vary with the magnetic activities. The charge and the electric field distribution confirm the presence of the Alfvén layer for the first time. In the Alfvén layer, the charge distribution has dawn-dusk asymmetry. The positive charge density at dusk is much greater than the negative charge density at dawn. These observations and analysis results could shed light on the structure of the magnetosphere and the magnetosphere-ionosphere coupling during storms.

How to cite: Shen, C., Gao, L., Zhou, Y., Ji, Y., Pu, Z., Russell, C. T., Escoubet, C. P., Bogdanova, Y. V., Zeng, G., Torbert, R., and Burch, J. L.: Charge Separations in the Geomagnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8347, https://doi.org/10.5194/egusphere-egu22-8347, 2022.

EGU22-8445 | Presentations | ST2.4

Revised Modular Model of Mercury’s Magnetospheric Magnetic Field 

Kristin Pump, Daniel Heyner, and Ferdinand Plaschke

Mercury is the smallest an innermost planet of our solar system and has a dipole-dominated internal magnetic field that is relatively weak, very axisymmetric and significantly offset towards north. Through the interaction with the solar wind, this field leads to a magnetosphere. Compared to the magnetosphere of Earth, Mercury’s magnetosphere is smaller and more dynamic. To understand the magnetospheric structures and processes we use in-situ MESSENGER data to develop a semi-empiric model, which can explain the observations and help to improve the mission planning for the BepiColombo mission en-route to Mercury.

We will present this semi-empiric KTH-model, a modular model to calculate the magnetic field inside the Hermean magnetosphere. Korth et al. (2015 and 2017) published a model, which is the basis for the KTH-Model. In this new version, the calculation of the magnetic field for the neutral current sheet is restructured based on observations rather than ad-hoc assumptions so that the description is more realistic. Furthermore, a new model is added to depict the partial ring current. An analysis of the residuals shows a better visibility of the field-aligned currents. In addition, this model offers the possibility to improve the main field determination.

How to cite: Pump, K., Heyner, D., and Plaschke, F.: Revised Modular Model of Mercury’s Magnetospheric Magnetic Field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8445, https://doi.org/10.5194/egusphere-egu22-8445, 2022.

EGU22-9036 | Presentations | ST2.4

Using X-ray imaging to find the magnetopause location 

Andrey Samsonov, Steven Sembay, Jennifer Carter, Graziella Branduardi-Raymont, and Andrew Read

The process of charge exchange between solar wind highly charged heavy ions and exospheric neutrals produces soft X-rays in geospace. The regions with the strongest emissivity are the magnetosheath and cusps. The Soft X-ray Imager (SXI) on board the forthcoming SMILE mission will measure X-ray emissivity integrated along the line-of-sight. By analyzing 2-D maps of X-ray counts from the SXI, we can extract information about magnetopause shape and position. It has been suggested that the maximum of integrated emissivity is tangent to the magnetopause. We check this assumption using the results of MHD simulations for different points along the SMILE trajectory. We show that this method can be used for finding the magnetopause location if some corrections are applied. We present methods of determining the location of the maximum of integrated emissivity using SXI counts maps for a moderately and strongly compressed magnetosphere.

How to cite: Samsonov, A., Sembay, S., Carter, J., Branduardi-Raymont, G., and Read, A.: Using X-ray imaging to find the magnetopause location, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9036, https://doi.org/10.5194/egusphere-egu22-9036, 2022.

EGU22-9481 | Presentations | ST2.4

Multiscale analysis of a current sheet crossing associated with a fast earthward flow during a substorm event detected by MMS 

Olivier Le Contel, Alessandro Retino, Alexandra Alexandrova, Rumi Nakamura, Soboh Alqeeq, Mohammed Baraka, Thomas Chust, Laurent Mirioni, Filomena Catapano, Christian Jacquey, Sergio Toledo-Redondo, Julia Stawarz, Katherine Goodrich, Daniel Gershman, Stephen Fuselier, Joey Mukherjee, Narges Ahmadi, Daniel Graham, Matthew R. Argall, and David Fischer and the A MMS Team

In July 2017, the MMS constellation was evolving in the magnetotail with an apogee of 25 Earth radii and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23rd of July around 16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static state. Then, MMS suddenly entered in the central plasma sheet and detected the local onset of a small substorm as indicated by the AE index (~400 nT). Fast plasma flows towards the Earth were measured for about 1 hour starting with a period of quasi-steady flow and followed by a series of saw-tooth plasma jets (“bursty bulk flows”). In the present study, we focus on a short sequence related to the crossing of an ion scale current sheet embedded in a fast earthward flow. The current sheet appears to be corrugated and with a significant guide field (BL/BM~0.5). Tailward propagating electrostatic solitary waves are detected just after the magnetic equator crossing and at the edge of the current sheet. We also analyze in detail an electron vortex magnetic hole also detected at the edge of this current sheet and discuss the Ohm’s law and energy conversion processes. We find that the energy dissipation associated with the electron vortex is three times greater (0.15nW/m3) than at the current sheet crossing (0.05nW/m3). Based on estimated statistical weight of these vortices we discuss possible consequences for the energy dissipation associated with fast earthward plasma flows.

How to cite: Le Contel, O., Retino, A., Alexandrova, A., Nakamura, R., Alqeeq, S., Baraka, M., Chust, T., Mirioni, L., Catapano, F., Jacquey, C., Toledo-Redondo, S., Stawarz, J., Goodrich, K., Gershman, D., Fuselier, S., Mukherjee, J., Ahmadi, N., Graham, D., Argall, M. R., and Fischer, D. and the A MMS Team: Multiscale analysis of a current sheet crossing associated with a fast earthward flow during a substorm event detected by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9481, https://doi.org/10.5194/egusphere-egu22-9481, 2022.

EGU22-9532 | Presentations | ST2.4

A statistical study of dipolarization fronts observed by MMS 

Soboh Alqeeq, olivier Le Contel, Patrick Canu, Alessandro Retinò, Hugo Breuillard, Thomas Chust, Alexandra Alexandrova, Laurent Mirioni, Yuri Khotyaintsev, Rumi Nakamura, Frederick Wilder, Hanying Wei, David Fischer, Daniel Gershman, James Burch, Roy Torbert, Barbara Giles, Stephen Fuselier, Robert Ergun, and Per Arne Lindqvist and the MMS Team

In the present work, we consider 49 dipolarization fronts (DF) detected by the Magnetospheric Multiscale (MMS) mission on 2017, near the Earth’s magnetotail equator (Bx<5nT). Criteria for selecting DF using an AIDApy routine are based on difference of maximum and minimum values computed with a 306 s sliding window. They request a Bz increase, an ion velocity increase and a density decrease. This first automatic selection is then ajusted manually with the following criteria : Bz increase larger than 5 nT, ion velocity larger than 150 km/s, density decrease and both ion and electron temperature increases. All these events belong to the most common category (A) defined by Schmid et al., 2015 in term of density decrease and temperature increase at the DF. However, based on a superposed epoch analysis of DF basic properties (magnetic field, density, velocity, ...) we distinguish two subcategories of events depending on the shape of the DF. The first subcategory (55.1%) corresponds to a slow decrease of the magnetic field after the DF and is associated with smaller ion velocity and hotter plasma. The second subcategory (44.9%) has the same time scale for the rising and the falling of the magnetic field (a bump) associated with a decrease of ion and electron pressures and faster velocity as shown in Alqeeq et al. 2021. For both categories we found that ions are mostly decoupled from the magnetic field by the Hall fields. The electron pressure gradient term is also contributing to the ion decoupling and likely responsible for an electron decoupling at DF. We also analyzed the energy conversion process. For the first subcategory we found that the energy in the spacecraft frame is transferred from the electromagnetic field to the plasma (J·E>0) ahead or at the DF. For the second subcategory, we found the same behavior ahead or at the DF whereas it is the opposite (J·E<0) behind the front. In the fluid frame, we found that the energy is mostly transferred from the plasma to the electromagnetic field (J·E ′ <0) ahead or at the DF for both subcategories but energy dissipation (J·E ′ >0) only occurs behind the front for the second subcategory. The possible origin of these two subcategories is discussed.

How to cite: Alqeeq, S., Le Contel, O., Canu, P., Retinò, A., Breuillard, H., Chust, T., Alexandrova, A., Mirioni, L., Khotyaintsev, Y., Nakamura, R., Wilder, F., Wei, H., Fischer, D., Gershman, D., Burch, J., Torbert, R., Giles, B., Fuselier, S., Ergun, R., and Lindqvist, P. A. and the MMS Team: A statistical study of dipolarization fronts observed by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9532, https://doi.org/10.5194/egusphere-egu22-9532, 2022.

EGU22-9556 | Presentations | ST2.4

Study of a dayside magnetopause reconnection event detected by MMS and related to a large-scale solar wind perturbation. 

Mohammed Baraka, Olivier Le Contel, Patrick Canu, Soboh Alqeeq, Mojtaba Akhavan-Tafti, Alessandro Retino, Thomas Chust, Alexandra Alexandrova, and Dominique Fontaine and the MMS Team

Magnetic reconnection is a fundamental process that is ubiquitous in the universe and allows the conversion of the magnetic field energy into heating and acceleration of plasma. It’s also very important as it is responsible for the dominant transport of plasma, momentum, and energy across the magnetopause from the solar wind into the Earth magnetosphere. Coronal Mass Ejections (CMEs) and Corotating Interaction Regions (CIRs) are the primary large-scale propagating structures and important drivers of unusual space weather disturbances causing magnetospheric activity. The present study reports on a magnetic reconnection event detected by the Magnetospheric Multiscale mission (MMS) on 21 October 2015 around 04:40 UT and related to a large-scale solar wind (SW) perturbation impacting the Earth’s magnetopause. Based on OMNI data, the event impacting the Earth’s magnetosphere is ahead of weak CIR (SW beta=~7 and Alfvénic Mach number~15) where the density of solar wind is about ~20 cm -3 (compared with average SW density ~3-10 cm -3). Furthermore, the magnetosheath (MSH) density measured by MMS just after the crossing of the magnetopause is about ~95 cm -3 (compared with average MSH density ~20 cm -3). Reconnection signatures such as ion and electron jets, Hall field, and energy conversion are compared with a “classical” reconnection event observed during quiet solar wind conditions.

How to cite: Baraka, M., Le Contel, O., Canu, P., Alqeeq, S., Akhavan-Tafti, M., Retino, A., Chust, T., Alexandrova, A., and Fontaine, D. and the MMS Team: Study of a dayside magnetopause reconnection event detected by MMS and related to a large-scale solar wind perturbation., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9556, https://doi.org/10.5194/egusphere-egu22-9556, 2022.

EGU22-9693 | Presentations | ST2.4 | Highlight

How does the presence of a large-scale magnetic field impact the solar wind energy dissipation in the Earth’s upper atmosphere? 

Romain Maggiolo, Lukas Maes, Gaël Cessateur, Fabien Darrouzet, Johan De Keyser, and Herbert Gunell

The protective effect of a planetary magnetic field on the planet’s atmosphere is still debated. This study focuses on a particular aspect of the chain of processes leading to atmospheric escape: the energy transfer from the solar wind to the upper atmosphere. Magnetized planets are surrounded by a large-scale magnetosphere which has two opposite effects. On the one hand, it efficiently diverts the solar wind so that only a small fraction of the solar wind energy flux that intercepts it eventually ends up being dissipated in the upper atmosphere. On the other hand, a large-scale magnetosphere dramatically increases the area of interaction between the solar wind and the planet and thus the amount of solar wind energy that may potentially be funneled into its upper atmosphere.

In this study, we estimate the solar wind energy flux currently dissipated in the Earth’s upper atmosphere using empirical formulas derived from observations found in the literature. We compare it to the solar wind energy that would intercept the induced magnetosphere of a hypothetical unmagnetized Earth. We show that the solar wind energy dissipated in the upper atmosphere is comparable to -if not higher than- the solar wind energy that would intercept a hypothetical unmagnetized Earth. This result indicates that the Earth's large-scale magnetic field does not protect the Earth’s upper atmosphere but rather increases the solar wind energy deposition.

How to cite: Maggiolo, R., Maes, L., Cessateur, G., Darrouzet, F., De Keyser, J., and Gunell, H.: How does the presence of a large-scale magnetic field impact the solar wind energy dissipation in the Earth’s upper atmosphere?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9693, https://doi.org/10.5194/egusphere-egu22-9693, 2022.

Outflow of ions from the terrestrial ionosphere and circulation in the magnetosphere plays an important role in the magnetospheric dynamics, by loading the magnetosphere with heavy atomic and molecular ions. Some of the outflowing ions can be re-injected into the inner magnetosphere, whereas some can completely escape to outer space. Cluster was the first mission in the magnetosphere to involve four spacecraft in a tetrahedral configuration, providing three-dimensional measurements of the space plasma parameters. The observations of the outflowing and escaping ion populations performed by Cluster are reviewed and the most prominent results highlighted. These show the dominance in the magnetotail lobes of cold plasma outflows originating from the polar caps. For the energetic heavy ion outflow the cusps constitute the main source. The dependence of the polar outflow on the solar wind parameters and on the geomagnetic activity has been evaluated for both cold ion populations and energetic heavy ions. For the later, outflow has been observed during all periods but an increase by two orders of magnitude has been shown during extreme space weather conditions. This outflow is adequate to change the composition of the atmosphere over geological time scales. At lower latitudes, the existence of a plasmaspheric wind, providing a continuous leak from plasmasphere, has been demonstrated. The general scheme of the outflowing ions circulation in the magnetosphere or escape, and its dependence on the IMF conditions, has been outlined. However, several questions remain open, waiting a future space mission to address them.

How to cite: Dandouras, I. and Yamauchi, M.: 20 Years of Cluster Observations of Heavy Ion Outflow, Circulation in the Magnetosphere and Escape: Advances and Open Questions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9917, https://doi.org/10.5194/egusphere-egu22-9917, 2022.

EGU22-9933 | Presentations | ST2.4

Flux Transfer Events in the Northern Hemisphere Polar Cusp Under Strong IMF Bx 

Caoimhe Doherty, Andrew Fazakerley, Christopher Owen, Robert Fear, Colin Forsyth, Andrew Kavanagh, Karl-Heinz Trattner, and Yulia Bogdanova

The location, shape, and size of the magnetospheric polar cusps are heavily influenced by upstream solar wind conditions. The effects of dominant IMF Bz and By components on the cusp are now well known.  However, the effect of a strong IMF Bx component on the structure of the polar cusps is relatively unexplored.  We present a case study of data recorded by the four Cluster spacecraft during a crossing of the northern hemisphere high altitude cusp in the winter season of 2018, when the IMF is directed southward and sunward. The Cluster spacecraft traverse the high-altitude cusp with separations between several hundred km and 1.5 Earth radii between each spacecraft, and travel at a roughly constant latitude with changing MLT.  We study these observations in conjunction with those of the ground based SuperDARN radars.

Each spacecraft observes many flux transfer type events within the cusp, although some events are not seen on all 4 spacecraft.  The magnetic field orientation often varies significantly during each distinct passage through individual flux tubes, clearly departing from the background magnetic field direction expected in the northern hemisphere high altitude cusp. A number of these events show bidirectional electron flux signatures typical of those expected on recently reconnected open northern hemisphere flux tubes. However, some flux tubes appear to be populated only by antiparallel moving electrons, while others show an isotropic distribution of electrons and ions. The SuperDARN STO radar site observes Poleward Moving Auroral Forms (PMAFs), consistent with the interpretation that Cluster observes open flux tubes, however the directions of convecting flux tubes seen by Cluster are not always consistent with the SuperDARN picture. We consider whether the influence of the strong IMF Bx results in the relocation of the dayside reconnection site to high northern latitudes, allowing Cluster to encounter a mix of open flux tubes in the northern cusp, each of which may be connected to either the Northern or Southern polar ionosphere.  The latter configuration may be particularly supported if reconnection near the cusp results in southern hemisphere open field lines being driven anti-sunward into the northern cusp as a result of enhanced sheath flows overcoming their magnetic tension at these latitudes.

How to cite: Doherty, C., Fazakerley, A., Owen, C., Fear, R., Forsyth, C., Kavanagh, A., Trattner, K.-H., and Bogdanova, Y.: Flux Transfer Events in the Northern Hemisphere Polar Cusp Under Strong IMF Bx, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9933, https://doi.org/10.5194/egusphere-egu22-9933, 2022.

EGU22-9956 | Presentations | ST2.4

Shock Motion and Ion Acceleration at Current Sheets Downstream of the Bow Earth’ s Bow Shock. 

Harald Kucharek, Steven J Schwartz, Imogen Gingell, Charles Farrugia, and Karlheinz J Trattner

At the Earth’s bow shock, most of the solar wind’s kinetic energy is partitioned into wave energy, particle acceleration, and heating. Very recent publications provide strong evidence that current sheets at the shock ramp region and downstream participate in the thermalization of the solar wind plasma. Their occurrence varies from single to multiple current sheets. What role do they play in downstream thermalization and ion acceleration?

We studied multiple bow shock crossings into the magnetosheath by the MMS spacecraft with its sophisticated instrumentation, characterizing and quantifying the occurrence of these current sheets, the associated magnetic field wave turbulence, and ion acceleration downstream of the shock. Shock traversals during increasing Mach number/dynamic pressure showed higher wave activity and broader distribution functions with suprathermal tails. Much less suprathermal ions downstream of the shock are observed at shock crossings during decreasing Mach numbers. These MMS observations show that current sheets and field gradients are associated with ion acceleration. The associated turbulence is likely a mediator for energy partition. With increasing Mach numbers, the bow shock moves away from the Sun and compresses the magnetosheath that favours reconnection of currents sheets, stronger electric field gradients and thus ion acceleration. With decreasing Mach numbers, the bow shock moves towards the Sun, becomes blunter, and the sheath region relaxes, making reconnecting current sheets less likely and smoothens field gradients resulting in less acceleration.

How to cite: Kucharek, H., Schwartz, S. J., Gingell, I., Farrugia, C., and Trattner, K. J.: Shock Motion and Ion Acceleration at Current Sheets Downstream of the Bow Earth’ s Bow Shock., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9956, https://doi.org/10.5194/egusphere-egu22-9956, 2022.

EGU22-10698 | Presentations | ST2.4

Detecting the edges of Earth's ion foreshock using Magnetic Gauss's Law 

Seth Dorfman, Kun Zhang, Lucile Turc, and Urs Ganse

Various types of plasma waves play key roles in magnetospheric physics in contexts ranging from the magnetosphere and its boundary layers to planetary bow shocks and foreshocks.  Due to limited available spacecraft measurements, the waves are often assumed to be plane waves that extend to infinity in all directions. A good example is the Earth's ion foreshock where intrinsically right-hand circularly polarized magnetosonic modes are generated by a fast ion beam. Many prior studies of these waves assume no variation of important physical quantities in the direction perpendicular to wave propagation. We show that Magnetic Gauss's Law implies that this assumption must be violated near the edge of the wave domain. The resulting false signature in the standard Magnetic Gauss's Law calculation of the wave vector orientation may be used to detect the domain edge. We demonstrate this new edge detection method in a simple wave model, a 2-D hybrid Vlasov simulation conducted using the Vlasiator code, and ARTEMIS spacecraft observations. In both the simulation and the spacecraft observations, this new signature is shown to correlate well with a determination of the foreshock edge based on the properties of the fast ion beam.  As the plane wave assumption is widely used in space physics data analysis techniques such as minimum variance analysis, these results may stimulate a reexamination of this assumption in other magnetospheric physics contexts.

This study is supported by NASA Grant 80NSSC20K0801.  Vlasiator is developed by the European Research Council Starting grant 200141-QuESpace, and Consolidator grant GA682068-PRESTISSIMO received by the Vlasiator PI. Vlasiator has also received funding from the Academy of Finland. See www.helsinki.fi/vlasiator

How to cite: Dorfman, S., Zhang, K., Turc, L., and Ganse, U.: Detecting the edges of Earth's ion foreshock using Magnetic Gauss's Law, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10698, https://doi.org/10.5194/egusphere-egu22-10698, 2022.

EGU22-11650 | Presentations | ST2.4

Survey of EDR-associated Magnetopause Flux Ropes with MMS 

Sadie Robertson, Jonathan Eastwood, Julia Stawarz, Christopher Russell, Barbara Giles, and James Burch

Flux ropes are twisted magnetic field structures produced during magnetic reconnection. They are thought to be important for energy transport and particle acceleration and are commonly observed throughout space plasma environments, including at the Earth’s magnetopause. Flux Transfer Events (FTEs), which typically contain flux ropes, have been observed to grow in size and flux content as they are convected over the magnetopause and into the magnetotail, contributing to flux transport in the Dungey cycle. More recently, small-scale flux ropes have been observed inside the Electron Diffusion Region (EDR) during magnetopause reconnection. 


In this study, we investigate the link between the EDR and flux ropes, presenting a survey of 245 flux ropes observed by the Magnetospheric Multiscale (MMS) mission on days during which the spacecraft also encountered the EDR. MMS measures the thermal electron and ion 3D distributions at 30 msec and 150 msec time resolution, respectively, and at spacecraft separations down to a few kilometres allowing the study of such electron-scale phenomena. We find that flux ropes are more likely to be observed closer to the EDR, and that flux ropes observed closer to the EDR tend to have greater axial magnetic field strength and therefore greater flux content. We suggest that we could be sampling a subset of flux ropes that are recently formed by the EDR and discuss how this impacts current theories for flux rope evolution on the magnetopause.

How to cite: Robertson, S., Eastwood, J., Stawarz, J., Russell, C., Giles, B., and Burch, J.: Survey of EDR-associated Magnetopause Flux Ropes with MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11650, https://doi.org/10.5194/egusphere-egu22-11650, 2022.

EGU22-11999 | Presentations | ST2.4

Magnetosheath jets during an CME passage: A case study 

Luis Preisser, Ferdinand Plaschke, Florian Koller, Manuela Temmer, and Owen Roberts

Localized enhancements in dynamic pressure observed in the Earth’s magnetosheath (EMS) have been studied since 20 years ago. These structures known as jets can propagate through the EMS transporting mass, momentum and energy being able to reach and perturb the Earth’s magnetopause.
Large scale solar wind (SW) structures called Coronal Mass Ejections (CMEs) travel through the interplanetary medium and depending on their direction they may impact the Earth. How the different SW conditions triggered by the CMEs (upstream side – shock/sheath – magnetic ejecta) change the production of jets in the EMS is a topic that is just beginning to be explored.
In this case study we characterize jets observed by THEMIS A, E and D during a CME passage. We find clear differences in number and size between the jets associated with the different CME regions arriving at the EMS. Comparing WIND and THEMIS data we discuss how these differences are associated with the SW conditions and with different jet generation mechanisms.

How to cite: Preisser, L., Plaschke, F., Koller, F., Temmer, M., and Roberts, O.: Magnetosheath jets during an CME passage: A case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11999, https://doi.org/10.5194/egusphere-egu22-11999, 2022.

EGU22-12276 | Presentations | ST2.4

Mapping High Energy Particle Population in Earth's Magnetosphere Using Augmented Star Trackers 

Christina Toldbo, Matija Herceg, Troelz Denver, Julia Sushkova, Mathias Benn, Peter S. Jørgensen, and John Leif Jørgensen

The ESA Swarm mission, launched on 22 November 2013, consists of three spacecraft each equipped with a Micro Advanced Stellar Compass (μASC) designed and validated by the Technical University of Denmark (DTU). Each Star Tracker features three Camera Head Units (CHUs) orientated orthogonally to avoid simultaneous blinding. The CCD sensor inside the star tracker is sensitive to energetic particle irradiation which appear as transient bright pixels dubbed 'hot spots' on the source images.

Conventionally hot spots are removed to support nominal attitude operation, however in February and March 2018 software was uploaded to the μASCs on-board Swarm, which in addition to using the hotspot measurements to improve the star tracking is moving the measured hotspot data to the telemetry to ground. This added functionality, enables detection and monitoring of high energy particles.

In this work we present processes and analysis of the high energy radiation data obtained from the Micro Advanced Stellar Compass (μASC) on board ESA's Swarm mission, from February 2018 to end of 2021. Taking advantage of three years of data, high sample rates (1-2 Hz), the beneficial orientation of the camera heads and simultaneous measurements from all three spacecraft it is possible to determine spatial and temporal derivatives of the electric and magnetic fields. Furthermore, since the Swarm spacecraft are in near-polar orbits at an altitude of 450-510 km above Earth's surface the spacecraft continuously monitor and map high energy particles at the South Atlantic Anomaly (SAA) of relevance for future mission planning as well as provide detailed time-radiation relations from charge injection processes from e.g. CMEs.

How to cite: Toldbo, C., Herceg, M., Denver, T., Sushkova, J., Benn, M., Jørgensen, P. S., and Jørgensen, J. L.: Mapping High Energy Particle Population in Earth's Magnetosphere Using Augmented Star Trackers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12276, https://doi.org/10.5194/egusphere-egu22-12276, 2022.

EGU22-13014 | Presentations | ST2.4 | Highlight

Seasonal and Diurnal variations of Kelvin–Helmholtz waves at Earth’s Magnetopause 

Shiva Kavosi, Joachim Raeder, and Charles Farrugia

We survey one solar cycle of in situ data from the NASA THEMIS (Time History of Events and Macro scale Interactions during Substorms) and MMS (Magnetospheric Multiscale) missions to identify Kelvin–Helmholtz Instability (KHI) along Earth’s magnetopause flank. We found that KHI occurrence rates exhibit semiannual and diurnal variations; the rate maximizes at the equinoxes and minimizes at the solstices. The rate varies for different IMF By polarities; it is maximum around fall equinox for negative IMF By, while is maximum around spring equinox for positive IMF By. The rate is directly related to the dipole tilt angle. Therefore, the equinoctial hypothesis explains most part of the seasonal and diurnal variation of KHI, while the angle of the Earth's dipole in the plane perpendicular to the Earth‐Sun line explains the difference between KHI occurrence rates with positive/negative IMF By. These results reveal the key role of Sun-Earth geometry on modulating the KHI and thus the importance of Earth’s dipole tilt and Sun solar declination angle as a function of time for plasma transport across the magnetopause.

How to cite: Kavosi, S., Raeder, J., and Farrugia, C.: Seasonal and Diurnal variations of Kelvin–Helmholtz waves at Earth’s Magnetopause, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13014, https://doi.org/10.5194/egusphere-egu22-13014, 2022.

EGU22-13170 | Presentations | ST2.4

Large-scale PIC Simulations of the Interaction of Solar Wind Discontinuities with the Dayside Magnetopause 

Jean Berchem, Giovanni Lapenta, Robert L. Richard, C.-Philippe Escoubet, and Simon Wing

Developing an understanding of the effects of solar wind structures on the dayside magnetopause is a necessary first step for comprehending how they impact the magnetosphere.  With this aim, we have used large-scale particle-in-cell (PIC) simulations to investigate the kinetic processes occurring at the magnetopause as solar wind structures impact the dayside magnetosphere.  In this presentation, we report our progress in investigating the interaction of simple discontinuities with the magnetopause.  Our procedure is to first run a global magnetohydrodynamic (MHD) simulation to predict the overall configuration of the solar wind-magnetosphere system before the impact of the discontinuity on the magnetopause. Then, fields and plasma moments within a large sub-domain of the global MHD simulation are used to set the initial conditions of the implicit PIC simulation of the impact. Preliminary results indicate that the interactions of solar wind discontinuities with the magnetopause are very likely to generate a succession of large magnetic flux ropes that move toward the cusps. The simulations reveal the development of a strong North-South asymmetry in the twisting of the ropes. This suggests that we should expect strong North- South asymmetries in particle precipitation when such discontinuities impact the magnetopause.

How to cite: Berchem, J., Lapenta, G., Richard, R. L., Escoubet, C.-P., and Wing, S.: Large-scale PIC Simulations of the Interaction of Solar Wind Discontinuities with the Dayside Magnetopause, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13170, https://doi.org/10.5194/egusphere-egu22-13170, 2022.

Energetic electron acceleration and precipitation in the Earth's outer radiation belt are highly related to whistler mode chorus waves. We perform test particle simulations to investigate electron dynamics interacting with both parallel and oblique chorus emissions at L=4.5. We build up a database of the Green's functions for a large number of electrons interacting with whistler mode chorus emissions. The loss process of electron fluxes interacting with consecutive chorus emissions in the outer radiation belt is traced by applying the convolution integrals of distribution functions and the Green's functions. Oblique chorus emissions lead to more electron precipitation than that led by parallel chorus emissions. By checking the resonance condition and resonant energies at loss cone angle, we find that the nonlinear scattering via cyclotron resonance is the main process that pushes energetic electrons into the loss cone. Electrons are difficult to be scattered into the loss cone directly by Landau resonance, but Landau resonance helps electrons moving toward the loss cone. We propose a 2-step precipitation process for oblique chorus emissions that contributes to more electron loss: (1) During the first chorus emission, the nonlinear trapping of Landau resonance accelerates an electron close to the loss cone. (2) During the second emission, the nonlinear scattering of cyclotron resonance scatters the electron into the loss cone. The combination of Landau resonance and cyclotron resonance by oblique chorus emissions results in a higher precipitation rate than the single cyclotron resonance by purely parallel chorus emissions.

How to cite: Hsieh, Y. and Omura, Y.: Energetic electron loss process associating with oblique chorus emissions in the outer radiation belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6, https://doi.org/10.5194/egusphere-egu22-6, 2022.

EGU22-475 | Presentations | ST2.5

Magnetospheric ULF wave dependence on Interplanetary Coronal Mass Ejections and Stream Interaction Regions 

Konstantina Thanasoula, Christos Katsavrias, Afroditi Nasi, Ioannis A. Daglis, Georgios Balasis, and Theodore Sarris

Radial diffusion driven by Ultra Low Frequency (ULF) waves is very important for magnetospheric dynamics, because it contributes to relativistic electron enhancements and losses in the outer Van Allen radiation belt. Previous studies have investigated the dependence of ULF wave power spectral density and radial diffusion coefficients (DLL) on solar wind parameters. However, a conclusive correlation between the type of interplanetary drivers (such as Interplanetary Coronal Mass Ejections (ICMEs) and Stream Interaction Regions (SIRs)), ULF wave power spectral density and radial diffusion coefficients DLL is still an open topic. In this study, we use the "SafeSpace" database (https://synergasia.uoa.gr/modules/document/?course=PHYS120), which includes radial diffusion coefficients DLL and ULF wave power spectral density. This database was created using magnetic and electric field measurements by the THEMIS satellites for a 9-year period (2011- 2019). We conduct a statistical analysis of radial diffusion coefficients DLL, which contributes to relativistic electron radial diffusion quantification, and ULF wave power spectral density, to find out their dependence on ICMEs (25 events) and SIRs (46 events). In addition, we study how the parameters of these solar wind drivers influence the growth of ULF waves and  the behavior of radial diffusion coefficients.

How to cite: Thanasoula, K., Katsavrias, C., Nasi, A., Daglis, I. A., Balasis, G., and Sarris, T.: Magnetospheric ULF wave dependence on Interplanetary Coronal Mass Ejections and Stream Interaction Regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-475, https://doi.org/10.5194/egusphere-egu22-475, 2022.

EGU22-1365 | Presentations | ST2.5

Alpha transmitter signals observed by the Van Allen Probes: Ducted vs. unducted propagation 

Frantisek Nemec, Ondrej Santolik, George B. Hospodarsky, William S. Kurth, and Craig Kletzing

Electromagnetic waves radiated by powerful military very low frequency transmitters can efficiently interact with energetic electrons trapped in the radiation belts and result in their precipitation. However, such interactions ultimately depend on the wave normal angles of propagating emissions. In the equatorial interaction region, these can be either very low (ducted propagation) or comparatively large (unducted propagation). It is thus important to be able to distinguish between the two propagation types and to quantify what portion of the wave energy propagates ducted/unducted. Unfortunately, spacecraft multicomponent wave measurements which would allow to directly experimentally tackle this issue typically do not extend to high enough frequencies with a sufficient frequency resolution. One exception that we exploit are signals from Alpha navigation transmitters, which radiate at frequencies as low as about 11.9 kHz. Such frequencies are readily detectable by the EMFISIS instrument onboard the Van Allen Probes spacecraft operating close to the geomagnetic equator at L-shells between about 1.1 and 6.5. We use respective multicomponent burst mode measurements to distinguish between the ducted and unducted modes of propagation and to evaluate their relative importance under different conditions. We show that while the unducted waves are detected more often, the ducted waves tend to have larger Poynting fluxes, so that the total power propagating in the two modes is roughly comparable.

How to cite: Nemec, F., Santolik, O., Hospodarsky, G. B., Kurth, W. S., and Kletzing, C.: Alpha transmitter signals observed by the Van Allen Probes: Ducted vs. unducted propagation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1365, https://doi.org/10.5194/egusphere-egu22-1365, 2022.

EGU22-1368 | Presentations | ST2.5

Determination of electron and proton fluxes in a low Earth orbit with SATRAM and comparison to EPT data 

Stefan Gohl, Benedikt Bergmann, Martin Kaplan, and Frantisek Nemec

The Space Application of Timepix based Radiation Monitor (SATRAM) was launched in May 2013 onboard the Proba-V spacecraft into a low Earth orbit of 820 km. SATRAM has been measuring the radiation environment since then. Due to its pixelized structure, one can find properties in the particle tracks that identify those tracks as electrons or protons. The goal is to determine the electron and proton fluxes measured by SATRAM. The rather thick aluminium box surrounding the Timepix detector cuts off the low end of the energy spectrum for all particle species, limiting the energy range to 700 keV to 7 MeV for electrons and 15 MeV to 400 MeV for protons. For the particle identification, a neural network was utilized. It has an accuracy of about 90 % for both particle species. A Geant4 simulation was conducted to determine the efficiency of the detector for electrons and protons, respectively. Unfortunately, the proton fluxes cannot be measured that way, as the electron background is in the same order of magnitude as the number of protons. Alternatives are being discussed. Finally, the electron fluxes are compared with the data from the Energetic Particle Telescope (EPT) in the relevant energy range, which is also situated onboard the Proba-V satellite. The electron fluxes of both instruments agree with each other.

How to cite: Gohl, S., Bergmann, B., Kaplan, M., and Nemec, F.: Determination of electron and proton fluxes in a low Earth orbit with SATRAM and comparison to EPT data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1368, https://doi.org/10.5194/egusphere-egu22-1368, 2022.

EGU22-1458 | Presentations | ST2.5

Statistical study of oxygen ion cyclotron harmonic waves observed by Van Allen Probes 

Yan Wang, Kaijun Liu, kyungguk Min, Fei Yao, Ying Xiong, Kun Cheng, Yuqi Liu, Xianming Zheng, and Jingyi Zhou

We report the first statistical survey of the oxygen ion cyclotron harmonic waves observed by Van Allen Probes throughout the mission. An example event observed on 19 February 2014 after a strong magnetic storm and a substorm was first presented to demonstrate the general properties of OCH waves. The observed waves have multiple spectral peaks around harmonics of the oxygen ion gyrofrequency. During the event, oxygen ionsof 10s keV had a ring-like partial shell velocity distribution which might have driven the wave excitation through the oxygen ion Bernstein instability. On the other hand, the phase space densities of He+ and O+ less than a few hundred eV were larger around 90° pitch angle, indicating transverse heating of these ions. Our statistical study shows that the waves occurred over 2 < L < 6 and across all magnetic local time. More than 50% of the events were observed just outside the plasmapause, and the typical wave amplitude is between ~0.1 and several nT. The frequency spacing between two consecutive wave harmonics decreases with increasing L but stabilizes when L > 5. The frequency spacing is larger than the local oxygen ion gyrofrequency for many events, especially those observed at larger L, suggesting that these waves propagated there from lower L shell regions. The waves are mainly on the dayside at L > 4 under quiet geomagnetic conditions, but can occur at lower L shells with a more uniform MLT distribution under more active geomagnetic conditions.

How to cite: Wang, Y., Liu, K., Min, K., Yao, F., Xiong, Y., Cheng, K., Liu, Y., Zheng, X., and Zhou, J.: Statistical study of oxygen ion cyclotron harmonic waves observed by Van Allen Probes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1458, https://doi.org/10.5194/egusphere-egu22-1458, 2022.

EGU22-2156 | Presentations | ST2.5

Resonance widening effect for electron scattering by electromagnetic ion cyclotron waves 

David Tonoian, Anton Artemyev, and Mark Shevelev

Resonant electron interaction with electromagnetic coherent waves in inhomogeneous magnetic fields is traditionally described by quasi-linear theory. The basic element of such a description are the diffusion coefficients evaluated for resonant energies and pitch-angles. High amplitude waves, however, may resonate with electrons nonlinearly, and such nonlinear resonance interaction would wider the energy and pitch-angle range of electrons scattered by waves. This study is devoted to investigation of the effect of a finite resonance width in energy/pitch-angle space for electrons interacting with electromagnetic ion cyclotron waves. We evaluate the resonance width for a realistic wave amplitudes and background magnetic field inhomogeneity, and then generalize the diffusion coefficients by including the resonance widening. Comparison of original and generalized diffusion rates reveals the wave parameters’ range and energy/pitch-angle range where the finite resonance width effect may be important for electron scattering.

How to cite: Tonoian, D., Artemyev, A., and Shevelev, M.: Resonance widening effect for electron scattering by electromagnetic ion cyclotron waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2156, https://doi.org/10.5194/egusphere-egu22-2156, 2022.

EGU22-2836 | Presentations | ST2.5 | Highlight

Active Control of the Radiation Belt Particle Populations with Ionospheric Amplification of VLF Waves 

Paul Bernhardt, Man Hua, Jacob Bortnik, Quanli Ma, Pekka Verronen, Michael McCarthy, Mark Golkowski, Morris Cohen, Andrew Howarth, Gordon James, and Nigel Meredith

Ground-based VLF transmitters located around the world generate signals that leak through the bottom side of the ionosphere in the form of whistler mode waves.  Wave and particle measurements on satellites have observed that these man-made VLF waves can be strong enough to scatter trapped energetic electrons into low pitch angle orbits, causing loss by absorption in the lower atmosphere.  This precipitation loss process is greatly enhanced by intentional amplification of the whistler waves in the ionosphere using a newly discovered process called Rocket Exhaust Driven Amplification (REDA).  Satellite measurements of REDA have shown between 30 and 50 dB intensification of VLF waves in space using a 60-second burn of the 150 g/s thruster on the Cygnus satellite that services the International Space Station (ISS) [Bernhardt et al. 2021; Bernhardt 2021].  This controlled amplification process is adequate to deplete the energetic particle population in the radiation belts in a few minutes rather than the multi-day period it would take naturally.  Numerical simulations of the pitch angle diffusion for radiation belt particles use the UCLA quasi-linear Fokker Planck model (QLFP) to assess the impact of REDA on radiation belt remediation (RBR) of newly injected energetic electrons [Bernhardt et al., 2022].  The simulated precipitation fluxes of energetic electrons are applied to models of D-region electron density and bremsstrahlung x-rays for predictions of the modified environment that can be observed with satellite and ground-based sensors.   

References:

Bernhardt, P.A., et al., Strong Amplification of ELF/VLF Signals in Space Using Neutral Gas Injections from a Satellite Rocket Engine (2021), Radio Science, 56(2), e2020RS007207, https://doi.org/10.1029/ 2020RS007207.

Bernhardt, P.A., The Whistler Traveling Wave Parametric Amplifier (WTWPA) Driven by an Ion Ring-Beam Distribution from a Neutral Gas Injection in Space Plasmas (2021), IEEE Transactions on Plasma Science. 49, 6, 1983-1996, DOI: 10.1109/TPS.2021.3079130.

Bernhardt, P.A., et al., Active Precipitation of Radiation Belt Electrons using Rocket Exhaust Driven Amplification (REDA) of Man-Made Whistlers, Submitted to the Journal of Geophysical Research, 2022.

How to cite: Bernhardt, P., Hua, M., Bortnik, J., Ma, Q., Verronen, P., McCarthy, M., Golkowski, M., Cohen, M., Howarth, A., James, G., and Meredith, N.: Active Control of the Radiation Belt Particle Populations with Ionospheric Amplification of VLF Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2836, https://doi.org/10.5194/egusphere-egu22-2836, 2022.

EGU22-2880 | Presentations | ST2.5 | Highlight

Chorus acceleration of ultra-relativistic radiation belt electrons during periods of low plasma density 

Hayley Allison, Yuri Shprits, Dedong Wang, Irina Zhelavskaya, and Artem Smirnov

Satellite observations show that electrons in the Van Allen radiation belts can have energies in excess of 7 MeV. The Van Allen Probes mission not only provided measurements of ultra-relativistic radiation belt electrons, but also simultaneous observations of plasma waves, allowing for the routine inference of total plasma number density. Based on a year of observations from 2015, we show that the electron plasma density has a controlling effect over local chorus acceleration to ultra-relativistic energies, which occurs only when the plasma number density drops down to very low values (~10 cm-3). Results from a Versatile Electron Radiation Belt (VERB) simulation show that a reduced electron plasma density allows chorus waves to efficiently resonate with electrons up to ultra-relativistic energies, producing enhancements from 100s of keV up to >7 MeV via local diffusive acceleration. We analyse statistically the observed chorus wave power during ultra-relativistic enhancement events, considering the contribution from both upper and lower band chorus waves. The Versatile Electron Radiation Belt (VERB) model is also used to recreate an ultra-relativistic electron acceleration event and simulation results are compared to observations, showing close agreement in the evolution when the reduction in electron plasma density is taken into account. The PINE density model allows for the investigation of global magnetospheric density changes during this event. We therefore analyze the how the global cold plasma density changes during ultra-relativistic enhancement events and compare to in-situ point measurements of the plasma density.

How to cite: Allison, H., Shprits, Y., Wang, D., Zhelavskaya, I., and Smirnov, A.: Chorus acceleration of ultra-relativistic radiation belt electrons during periods of low plasma density, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2880, https://doi.org/10.5194/egusphere-egu22-2880, 2022.

EGU22-4497 | Presentations | ST2.5

Estimating radial diffusion using a hybrid-Vlasov simulation 

Harriet George, Adnane Osmane, Emilia Kilpua, Solene Lesjone, Milla Kalliokoski, and Sanni Hoilijoki and the Vlasiator team
Radial diffusion coefficients quantify non-adiabatic transport of energetic particles by electromagnetic field fluctuations in planetary radiation belts. Theoretically, radial diffusion occurs for an ensemble of particles that experience irreversible violation of their third adiabatic invariant, which is equivalent to a change in their Roederer L* parameter. Thus, the Roederer L* coordinate is the fundamental quantity from which radial diffusion coefficients can be computed. We present a methodology to calculate the Lagrangian derivative of L* from global magnetospheric simulations, and test it with an application to Vlasiator, a hybrid-Vlasov model of near-Earth space. We use a Hamiltonian formalism for particles confined to closed drift shells with conserved first and second adiabatic invariants to compute changes in the guiding center drift paths from background electric and magnetic field fluctuations. Performing this calculation for different energies allows the rate of change of L* to be evaluated for different populations travelling along the same guiding center drift path without the need to inject and trace test particles. We investigate the feasibility of this methodology by computing the time evolution of L* for an equatorial ultrarelativistic electron population travelling along four guiding center drift paths in the outer radiation belt of a five minute portion of a Vlasiator simulation. Due to the short time scale and geometry of the test run, low amplitude Pc3 fluctuations are the primary driver of radial diffusion, which results in preliminary estimates for the radial diffusion coefficients that are two to six orders of magnitude below those corresponding to more active magnetospheric conditions with Pc5 fluctuations as the primary driver. However, our results show that an alternative methodology to compute detailed radial diffusion transport is now available and could form the basis for comparison studies between numerical and observational measurements of radial transport in the Earth’s radiation belts.

How to cite: George, H., Osmane, A., Kilpua, E., Lesjone, S., Kalliokoski, M., and Hoilijoki, S. and the Vlasiator team: Estimating radial diffusion using a hybrid-Vlasov simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4497, https://doi.org/10.5194/egusphere-egu22-4497, 2022.

Zebra stripes are structured peaks and valleys observed on spectrograms of protons and energetic electrons trapped in the inner radiation belts. They have been observed since the 1960s and even though they are transient structures, statistical studies have shown that they are commonly observed and correlated with geomagnetic Kp and Dst indices. Since their discovery, various mechanisms relying on wave-particle interactions have been suggested to explain the formation of zebra stripes. More recently, Lejosne and Roederer (JGR, 121, 2016) have presented a kinematic argument (supported with numerical results) with less constraints than models relying on drift-orbit mechanisms. In this communication, we present a theoretical derivation of zebra stripes from first principles and demonstrate that 1) their formation has a kinematic origin, and 2) that it does not require the presence of electric or magnetic field fluctuations. However, we show that the inclusion of electric or magnetic field fluctuations does not prevent the formation of zebra stripes, and our analysis therefore provides an explanation as to why simulations of drift orbit processes have been able to reproduce zebra stripes patterns.

How to cite: Osmane, A.: Theoretical explanation for the formation of zebra stripes in the inner radiation belts despite the absence of electric or magnetic field fluctuations., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4560, https://doi.org/10.5194/egusphere-egu22-4560, 2022.

EGU22-5502 | Presentations | ST2.5

On the Generation of Pi2 Pulsations due to Plasma Flow Patterns Around Magnetosheath Jets 

Christos Katsavrias, Savvas Raptis, Ioannis Daglis, Tomas Karlsson, Marina Georgiou, and George Balasis

We report observations of a magnetosheath jet followed by a period of decelerated background plasma. During this period, THEMIS-A magnetometer showed abrupt disturbances which, in the wavelet spectrum, appeared as prominent and irregular pulsations in two frequency bands (7.6–9.2 and 12–17 mHz) within the Pi2 range. The observations suggest—for the first time to our knowledge— that these pulsations were locally generated by the abrupt magnetic field changes driven by the jet’s interaction with the ambient magnetosheath plasma. Furthermore, similar pulsations, detected by THEMIS-D inside the magnetosphere with a 140 s time-lag (which corresponds to the propagation time of a disturbance traveling with Alfvénic speed), are shown to be directly associated with the ones in the magnetosheath, which raises the question of how exactly these pulsations are propagated through the magnetopause.

This research is co-financed by the Greece and the European Union (European Social Fund - ESF) through the Operational Program “Human Resources Development, Education and Lifelong Learning 2014–2020” in the context of the project ULFpulse (MIS: 5048130). C. Katsavrias and I.A. Daglis aknowledge the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437. S. Raptis and T. Karlsson acknowledge support from SNSA grant 90/17.

How to cite: Katsavrias, C., Raptis, S., Daglis, I., Karlsson, T., Georgiou, M., and Balasis, G.: On the Generation of Pi2 Pulsations due to Plasma Flow Patterns Around Magnetosheath Jets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5502, https://doi.org/10.5194/egusphere-egu22-5502, 2022.

EGU22-6643 | Presentations | ST2.5

Statistical analysis of ion composition and effects on EMIC waves in the outer magnetosphere 

Justin Lee, Sergio Toledo-Redondo, Ian Cohen, Drew Turner, Sarah Vines, and Robert Allen

Ionospheric-originating cold ions are difficult to measure throughout Earth's magnetosphere due to spacecraft charging limiting our ability to measure this low energy population, thus complicating investigations into how these cold ions participate in the growth of electromagnetic ion cyclotron (EMIC) waves. While these cold ion populations pose measurement challenges for most missions, recent event studies have shown that, at times, the Magnetospheric Multiscale (MMS) mission is capable of directly measuring both the low-energy cold populations as well as the hot ion composition, enabling improved understanding of EMIC wave generation, propagation, and wave polarization properties [1, 2, 3, 4]. These studies demonstrated the utility of considering the full ion composition for improving our understanding of different aspects of EMIC waves in the outer magnetosphere. We applied our experience analyzing the combined ion composition and EMIC wave data from event studies and conducted a statistical analysis of MMS datasets during the Prime Mission dayside intervals, with plans to expand the analysis to later mission phases and other magnetospheric regions. Out of approximately 6000 dayside wave intervals identified, around 25% of the intervals also contained simultaneous measurements of the cold ion composition needed to conduct more accurate modeling of linear wave growth in the outer magnetosphere, where the free energy source of EMIC waves may also be modulated by solar wind pressure pulses. This paper will discuss observations and progress on the statistical analysis and possible implications for studies on inner magnetospheric EMIC waves.

References
1.    Vines, S. K., Allen, R. C., Anderson, B. J., Engebretson, M. J., Fuselier, S. A., Russell, C. T., et al. (2019). EMIC Waves in the Outer Magnetosphere: Observations of an Off-Equator Source Region. Geophys. Res. Lett. 46, 5707–5716. doi:10.1029/2019GL082152
2.    Lee, J. H., Turner, D. L., Toledo-Redondo, S., Vines, S. K., Allen, R. C., Fuselier, S. A., et al. (2019). MMS Measurements and Modeling of peculiar Electromagnetic Ion Cyclotron Waves. Geophys. Res. Lett. 46, 11622–11631. doi:10.1029/2019GL085182
3.    Lee, J. H., Turner, D. L., Vines, S. K., Allen, R. C., Toledo-Redondo, S., Bingham, S. T., et al. (2021). Application of Cold and Hot Plasma Composition Measurements to Investigate Impacts on Dusk-Side Electromagnetic Ion Cyclotron Waves. J. Geophys. Res. Space Phys. 126, e2020JA028650. doi:10.1029/2020JA028650
4.    Toledo-Redondo, S., Lee, J. H., Vines, S. K., Turner, D. L., Allen, R. C., André, M., et al. (2021). Kinetic Interaction of Cold and Hot Protons with an Oblique EMIC Wave Near the Dayside Reconnecting Magnetopause. Geophys. Res. Lett. 48, e2021GL092376. doi:10.1029/2021GL092376

How to cite: Lee, J., Toledo-Redondo, S., Cohen, I., Turner, D., Vines, S., and Allen, R.: Statistical analysis of ion composition and effects on EMIC waves in the outer magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6643, https://doi.org/10.5194/egusphere-egu22-6643, 2022.

EGU22-7259 | Presentations | ST2.5

Electron Dynamics in a Chorus Wave Field Generated from Particle-in-Cell Simulations 

Zeyu An, Yifan Wu, and Xin Tao

How to properly describe resonant interactions between electrons and quasi-coherent chorus waves is still an open question. Previous studies have progressed from modeling chorus as a single wave to considering effects such as amplitude modulation or phase decoherence in wave particle resonance. However, incorporating realistic features of chorus waves in test particle calculations has always been a challenging but critically important step to evaluate their nonlinear effects. In this work, we use a chorus wave packet generated by a particle-in-cell simulation in test-particle simulations. The used chorus wave naturally has features including amplitude modulation, phase decoherence and dynamic evolution during propagation. Our results suggest that, while being latitudinal dependent, realistic features of chorus generally lead to significant suppression of nonlinear effects. This result should be important to understand phase space transport of electrons due to interactions with chorus waves.

How to cite: An, Z., Wu, Y., and Tao, X.: Electron Dynamics in a Chorus Wave Field Generated from Particle-in-Cell Simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7259, https://doi.org/10.5194/egusphere-egu22-7259, 2022.

EGU22-7574 | Presentations | ST2.5

Using mutual information to investigate non-linear correlation between AE index, ULF Pc5 wave activity and electron precipitation 

Sanni Hoilijoki, Emilia Kilpua, Adnane Osmane, Milla Kalliokoski, Harriet George, Mikko Savola, and Timo Asikainen

The Earth’s radiation belts are occupied by energetic electrons trapped by the geomagnetic field. The anisotropic electron distribution injected from the magnetotail during substorms drives the very low frequency whistler mode chorus waves in the outer radiation belt. Chorus waves are able to accelerate the electrons as well as cause them to precipitate into the upper atmosphere. The electrons in the radiation belt are also affected by ultra-low frequency (ULF) waves in the Pc5 range, that can be driven internally or by the solar wind-magnetosphere interactions. Using mutual information from information theory, we investigate the nonlinear dependence between the substorm activity indicated by the AE index, global Pc5 ULF wave activity, and electron precipitation at three different energy ranges between L shells from 5 to 7. We find that both the Pearson correlation and mutual information are highest between the AE index and precipitation of 30-100 keV energy electrons between MLTs 6-12, where the electrons are usually precipitated by the chorus waves. The time lag of the maximum correlation between the AE index and electron precipitation increases from 0 to 3h from dawn to dusk, which is consistent with drift period of the electrons in the radiation belt. We compare results from geomagnetically more and less active years and the results indicate that Pearson correlation between AE index and ULF wave activity/electron precipitation is weaker during the more active year while the changes in the mutual information are negligible. This suggest that during quieter magnetospheric conditions the interactions are more linear than during geomagnetically active times.

How to cite: Hoilijoki, S., Kilpua, E., Osmane, A., Kalliokoski, M., George, H., Savola, M., and Asikainen, T.: Using mutual information to investigate non-linear correlation between AE index, ULF Pc5 wave activity and electron precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7574, https://doi.org/10.5194/egusphere-egu22-7574, 2022.

EGU22-13168 | Presentations | ST2.5

Role of the nonlinear Landau resonance in intense precipitations of sub-relativistic electrons 

Dmitri Vainchtein, Anton V. Artemyev, and Xiaojia Zhang

Precipitations of energetic electrons into the Earth's atmosphere are important factor of radiation belt dynamics and the magnetosphere-ionosphere coupling. Microbursts, which are the most intense of such precipitations, are short-living bursts of precipitating fluxes detected by low-altitude spacecraft. Due to wide energy ranges of observed microbursts and their transient nature, they are generally associated with energetic electron scattering into the loss-cone via cyclotron resonance with field-aligned intense whistler-mode chorus waves. In this study, we show that intense sub-relativistic precipitations may be generated via the nonlinear Landau resonance of electrons with very oblique whistler-mode waves. Such precipitations are not associated with electron flux decrease in the radiation belts, but rather indicate the rapid electron acceleration up to 100-200 keV around the equator. We combine theoretical model of the nonlinear Landau resonances and equatorial observations of very oblique intense whistler-mode waves. The proposed scenario of intense sub-relativistic precipitations demonstrate the importance of very oblique whistler-mode waves for the radiation belt dynamics.

How to cite: Vainchtein, D., Artemyev, A. V., and Zhang, X.: Role of the nonlinear Landau resonance in intense precipitations of sub-relativistic electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13168, https://doi.org/10.5194/egusphere-egu22-13168, 2022.

EGU22-1026 | Presentations | ST2.6

Are Pi2 pulsations in meridian plane a field line dipolarization? 

Osuke Saka and Dmitri Klimushkin

Dawn-dusk flow shears in the nightside magnetosphere associated with field line dipolarization produce tangential discontinuities in the midnight sector and generate periodic displacement of the discontinuity surface at Pi2 periodicities through the KH instabilities [Saka et al., 2010].

Wave polarizations of Pi2 pulsations thus produced in the magnetosphere by the boundary displacement are generally reversed in the polar ionosphere [Saka et al., 2012]. The polarization reversal cannot be understood through the reconfiguration of geomagnetic field lines in terms of the fundamental harmonics but rather by considering the third harmonics in the meridian planes. On the ground, negative bays marked by decrease of the northward component of the geomagnetic fields are observed. We show that the field line deformations associated with third harmonics matched those of field line dipolarization and they are produced by the poloidal wave mode guided along the field lines: guided poloidal mode [Radoski, 1967]. This result indicates that Pi2 pulsations in meridian plane are field line dipolarization itself excited at the outer boundary of closed magnetosphere.

 

References

Radoski, H., Highly asymmetric MHD resonances: the guided poloidal mode, J. Geophys. Res., 72, 4026, 1967.

Saka,O., Hayashi, K., and Thomsen, M., First 10 min intervals of Pi2 onset at geosynchronous altitudes during the expansion of energetic ion regions in the nighttime sector, J. Atmos. Solar Terr. Phys., 72, 1100, 2010.

Saka, O., K. Hayashi, and D. Koga, Excitation of the third harmonic mode in meridian planes for Pi2 in the auroral zone. J. Geophys. Res., 117, A12215, doi:10.1029/2012JA018003, 2012.

How to cite: Saka, O. and Klimushkin, D.: Are Pi2 pulsations in meridian plane a field line dipolarization?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1026, https://doi.org/10.5194/egusphere-egu22-1026, 2022.

EGU22-1358 | Presentations | ST2.6

The Correspondence between Sudden Commencements and Induced Currents; Insights from New Zealand 

Andy Smith, Craig Rodger, Daniel Mac Manus, Colin Forsyth, Jonathan Rae, Mervyn Freeman, Mark Clilverd, Tanja Petersen, and Michael Dalzell

The impact of a solar wind pressure pulse on the Earth’s magnetosphere causes rapid changes in the surface geomagnetic field, often termed Sudden Commencements (SCs).  Such magnetic field changes can induce potentially damaging currents (GICs) in conducting infrastructure on the ground, and therefore represents a critical space weather hazard.  Unfortunately, GICs are not often measured directly.  Instead, large GICs are often inferred from easier-to-measure large magnetic perturbations.  In this work we examine the coupling between SCs and observed GICs in New Zealand, where both measurements are available.

Overall, we find excellent correlations between the maximum magnetic perturbations and GICs during SCs. Nevertheless, if the SC precedes a geomagnetic storm, then it is associated with 22% larger GICs, controlling for the size of the magnetic deflection.  Further, if the SC is observed when New Zealand is on the dayside of the Earth then the associated GICs are 30% greater.  We investigate these findings, and attribute them to the full vector directionality of the strongest magnetic field deflection and the full rate of change of the magnetic field of the SC, beyond that recorded in the one minute resolution data.

Finally, we show that based on the properties of the solar wind shock, a skilful prediction can be made as to whether an SC and/or a geomagnetic storm will be observed, which may be used to guide interpretation of the coupling between the magnetic deflection and GICs.

How to cite: Smith, A., Rodger, C., Mac Manus, D., Forsyth, C., Rae, J., Freeman, M., Clilverd, M., Petersen, T., and Dalzell, M.: The Correspondence between Sudden Commencements and Induced Currents; Insights from New Zealand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1358, https://doi.org/10.5194/egusphere-egu22-1358, 2022.

EGU22-4687 | Presentations | ST2.6

Three-dimensional Hybrid-Vlasov Simulations of Geomagnetic Storms 

Konstantinos Horaites, Markku Alho, Markus Battarbee, Maxime Dubart, Urs Ganse, Harriet George, Maxime Grandin, Talgat Manglayev, Minna Palmroth, Konstantinos Papadakis, Jonas Suni, Vertti Tarvus, Lucile Turc, Ivan Zaitsev, and Hongyang Zhou

Vlasiator (https://www2.helsinki.fi/en/researchgroups/vlasiator) is a high-performance kinetic code that is now conducting the first ever 3D hybrid-Vlasov simulations of the global magnetospheric system. In recent months, the driving conditions of these simulations have been scaled up to emulate intense space weather events. Specifically, we have investigated the impact of a pressure pulse with southward-oriented Bz on the Earth's magnetosphere. Our simulations reproduce many known effects, for example the expansion of the auroral oval, compression of the magnetopause, the development of field-aligned currents, and enhanced particle precipitation near the open/closed field line boundary. We compare our data with spacecraft observations of real events that exhibit similar parameters to those imposed in the simulation. Our analysis shows that the hybrid-Vlasov approach captures many of the important aspects of the magnetospheric response to an incoming pressure pulse. With sufficient validation of our simulations by comparison with moderate storms, we aim to show that Vlasiator can be used as a tool to study even the most extreme events and their potential impacts on Earth's critical infrastructure.

How to cite: Horaites, K., Alho, M., Battarbee, M., Dubart, M., Ganse, U., George, H., Grandin, M., Manglayev, T., Palmroth, M., Papadakis, K., Suni, J., Tarvus, V., Turc, L., Zaitsev, I., and Zhou, H.: Three-dimensional Hybrid-Vlasov Simulations of Geomagnetic Storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4687, https://doi.org/10.5194/egusphere-egu22-4687, 2022.

EGU22-8149 | Presentations | ST2.6

A perspective on substorm dynamics from 10 years of Auroral Kilometric Radiation 

James Waters, Caitriona Jackman, Daniel Whiter, Colin Forsyth, Alexandra Fogg, Laurent Lamy, Baptiste Cecconi, Xavier Bonnin, and Karine Issautier

Auroral Kilometric Radiation (AKR) is terrestrial radio emission that originates from high latitude magnetic field lines. The intensity of AKR increases when the magnetosphere is perturbed, and so can indicate the presence of driving from the solar wind. This is true for structures that can vary in scale such as pressure pulses, as well as substorm onsets that follow periods of negative turnings in the Z component of the interplanetary magnetic field. In the latter case, AKR intensification correlates with the strengthening of high-latitude current systems in the ionosphere as the magnetotail current is reconfigured. As well as this, morphological changes in the AKR source region have also been observed to coincide with substorm onset, with an intensification of the AKR emission often accompanied by a low frequency extension, interpreted as an expansion of the source region to higher altitudes along the field line. Although the directivity and source region localisation of AKR make the observations highly dependent on observer local time and latitude, we isolate AKR from Wind radio observations made over a decade and examine the observations with respect to the spacecraft viewing position, accounting for such effects. Using lists of substorm onsets, we examine the AKR power and the spectral extent of the emission with respect to the substorm timeline, expanding on previous studies of the AKR response. Results show a clear increase in AKR power that precedes substorm onset by approximately 20 minutes, and confirm a proportionally higher intensification in lower frequency AKR sources. This in turn indicates quantitatively the spatial response of parallel electric fields after the loading of magnetic flux during substorm growth phase. In characterising the typical AKR response during substorms, these results can inform observations of magnetospheric changes during sudden commencement events and those that are seperate from substorm dynamics.

How to cite: Waters, J., Jackman, C., Whiter, D., Forsyth, C., Fogg, A., Lamy, L., Cecconi, B., Bonnin, X., and Issautier, K.: A perspective on substorm dynamics from 10 years of Auroral Kilometric Radiation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8149, https://doi.org/10.5194/egusphere-egu22-8149, 2022.

EGU22-10089 | Presentations | ST2.6

A Non-Local Spread-F-like Event Over Arecibo as the Possible Result of a Solar Wind Pressure Pulse 

Salih Mehmed Bostan, Julio V. Urbina, John D Mathews, and Ross L. Dinsmore

Solar wind pressure pulses are known to modify electrodynamics of the terrestrial magnetosphere. In this paper, we present a possible electrodynamic reaction of the ionosphere to a small and brief pressure pulse observed by local and non-local instrument systems over Arecibo Observatory, Puerto Rico and extending over at least the mesoscale. Initially, a strong, four hour long, mid-latitude spread-F-like event was observed through a high frequency, wide-beam radar system, Penn State Ionospheric Radar Imager (PIRI), deployed near Arecibo (18.36◦ E, 66.75◦ S, and f = 4.42 MHz). The same spread-F event was also observed using the dual, narrow-beam 430 MHz Arecibo incoherent scatter radar. Furthermore, GPS delta-vTEC measurements from Carribean island sector revealed that the event was apparently moving from west to east and then east to west crossing over Arecibo twice. Similar GPS-TEC measurements from the South American sector showed that an equatorial spread-F was also present. We use SuperMAG magnetometer and NASA’s OMNI solar wind data to show that a small solar wind pressure pulse and rapid changes in the solar wind magnetic field are likely causes for the observed ionospheric features over Arecibo.

How to cite: Bostan, S. M., Urbina, J. V., Mathews, J. D., and Dinsmore, R. L.: A Non-Local Spread-F-like Event Over Arecibo as the Possible Result of a Solar Wind Pressure Pulse, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10089, https://doi.org/10.5194/egusphere-egu22-10089, 2022.

EGU22-11431 | Presentations | ST2.6

Multispacecraft wave diagnostics of the flapping motion of the magnetotail current sheet 

Bohdan Petrenko, Elena Kronberg, and Elena Grigorenko

The flapping motion of the magnetotail current sheet has a valuable contribution to magnetosphere dynamics. We have investigated features of flapping motions involving single- and multi-spacecraft methods using MMS and Cluster measurements. Velocities of dawn-dusk propagation of these motions and their types have been determined using Harris current sheet model and minimum variance analysis of the magnetic field. Dispersion features of such wavy motions using the phase differencing technique were explored.             

This work was carried out in accordance with the Target Comprehensive Program of the SRI NASU and SSAU in plasma physics with the support of grant no. 97742 of the Volkswagen Foundation (VW-Stiftung). 

How to cite: Petrenko, B., Kronberg, E., and Grigorenko, E.: Multispacecraft wave diagnostics of the flapping motion of the magnetotail current sheet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11431, https://doi.org/10.5194/egusphere-egu22-11431, 2022.

EGU22-12854 | Presentations | ST2.6

Ground response of seasonal Pc5 power to varying solar wind conditions 

Reko Hynönen and Eija Tanskanen

Pc5 waves are a sub-group of ultra-low frequency (ULF) waves in the magnetosphere. We determine the Pc5 wave power from ground magnetometer measurements in IMAGE network and statistically study their dependence on solar wind conditions, like solar wind speed and dynamic pressure, separating them from the solar phase and solar conditions in a statistical sense.

Pc5 power is dependent on the magnetic local time, season, and magnetic latitude. We show that while it is always heavily modulated by solar wind speed, the intensity of its ground response also varies over time. Particularly, the ground response is usually the strongest in the morning and midnight hours, while a minor maximum can sometimes be found in the midday or afternoon hours.

How to cite: Hynönen, R. and Tanskanen, E.: Ground response of seasonal Pc5 power to varying solar wind conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12854, https://doi.org/10.5194/egusphere-egu22-12854, 2022.

EGU22-801 | Presentations | ST2.7 | Highlight

Imaging the magnetosphere with the SMILE Mission 

C.-Philippe Escoubet, Chi Wang, and Graziella Branduardi-Raymont and the SMILE team

The interaction between the solar wind and the Earth's magnetosphere, and the geospace dynamics that result, is one of the key questions in space plasma physics. In situ instruments on a fleet of solar wind and magnetospheric constellation missions now provide the most detailed observations of Sun-Earth connections over multiple scales, from the smallest of a few kilometres up to the largest of a few 10s of Earth radii. However, we are still unable to quantify the global effects of the drivers of such connections, including the conditions that prevail throughout geospace. This information is the key missing link for developing a complete understanding of how the Sun gives rise to and controls Earth's plasma environment and space weather. This is where SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) comes in.
SMILE is a novel self-standing mission dedicated to observing the solar wind - magnetosphere coupling via simultaneous in situ solar wind/magnetosheath plasma and magnetic field measurements, soft X-ray imaging of the magnetosheath, magnetopause and polar cusps, and UV imaging of the Northern hemisphere auroral oval. Remote sensing of the magnetosheath and cusps with soft X-ray imaging is made possible thanks to solar wind charge exchange (SWCX) X-ray emissions known to occur in the vicinity of the Earth's magnetosphere. SMILE is a joint mission between ESA and the Chinese Academy of Sciences (CAS) due for launch at the end of 2024. SMILE science objectives as well as the latest technical developments jointly undertaken by ESA and CAS and the international instrument teams will be presented.

How to cite: Escoubet, C.-P., Wang, C., and Branduardi-Raymont, G. and the SMILE team: Imaging the magnetosphere with the SMILE Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-801, https://doi.org/10.5194/egusphere-egu22-801, 2022.

EGU22-1177 | Presentations | ST2.7

Observations and simulations of northward IMF magnetotail structure 

Laura Fryer, Robert Fear, Imogen Gingell, John Coxon, Minna Palmroth, Sanni Hoilijoki, Pekka Janhunen, and Anita Kullen

We investigate the dynamic coupling between the solar wind and Earth’s magnetosphere during northward IMF conditions. The high latitude lobe regions of the magnetosphere during such conditions are generally characterised as containing cool, very low energy plasma populations. However, when the solar wind is directed northward, hot plasma populations can sometimes be observed within the lobes, and transpolar arcs (auroral features which extend from the nightside into the polar cap) can also be present. We discuss three cases in which the Cluster spacecraft observed uncharacteristically energetic plasma populations in the lobe, with the footprint of the spacecraft intersecting a transpolar arc (Fryer et al., 2021). These observations reveal that both the hot plasma populations, and therefore transpolar arcs, are likely to form on closed field lines and are consistent with a mechanism in which magnetotail reconnection builds up closed field lines within the magnetotail, which then become “stuck” in the lobe (Milan et al., 2005).

Under certain northward IMF conditions, we find that the Grand Unified Magnetosphere-Ionosphere Coupling Simulation (GUMICS) model reproduces a similar large, closed field line region in the magnetotail. We find similarities between the structures seen within the simulation runs, the results of the in-situ observational study, and the Milan et al. (2005) magnetotail reconnection model, but also note some key differences in the configuration of the magnetotail reproduced in the simulations, compared with the remote and in situ observations. Finally, we note that the SMILE spacecraft will be ideally positioned to observe the coupling between the solar wind and Earth’s magnetosphere during northward IMF conditions, through both high latitude in situ observations and imaging of the auroral response.

How to cite: Fryer, L., Fear, R., Gingell, I., Coxon, J., Palmroth, M., Hoilijoki, S., Janhunen, P., and Kullen, A.: Observations and simulations of northward IMF magnetotail structure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1177, https://doi.org/10.5194/egusphere-egu22-1177, 2022.

EGU22-1359 | Presentations | ST2.7 | Highlight

Extreme magnetopause locations and their sources 

Zdenek Nemecek, Jana Safrankova, Kostiantyn Grygorov, Gilbert Pi, Maryam Aghabozorgi Nafchi, Frantisek Nemec, and Jiri Simunek

Comparison of observed magnetopause locations with model predictions can serve as a proof of our understanding of the interaction between solar wind and Earth magnetic field. Since the corresponding upstream conditions are usually derived from observation at L1, our knowledge on solar wind propagation and evolution on short scales are tested as well. We have collected about 40 000 of magnetopause crossings observed by THEMIS spacecraft in course of 2007–2019 years and compared the observed magnetopause position with prediction of several empirical magnetopause models using OMNI upstream parameters (mostly derived from ACE observations) and Wind magnetic field and plasma measurements propagated by our two-step propagation routine. The difference between observed and predicted magnetopause radial distance, Robs – Rmod was used for quantification of the model-observation agreement. We have found that the distribution of Robs – Rmod can be well fitted by the Gaussian distribution with FWHM ≈1.2 Re for all models and both upstream monitors. Nevertheless, the tails of the distributions are enhanced for all models and Robs – Rmod larger than 2 Re are rather frequent. A detailed analysis of such events leads to suggestions for improvement of investigated models or for a building of a new empirical model of the equatorial magnetopause.

How to cite: Nemecek, Z., Safrankova, J., Grygorov, K., Pi, G., Aghabozorgi Nafchi, M., Nemec, F., and Simunek, J.: Extreme magnetopause locations and their sources, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1359, https://doi.org/10.5194/egusphere-egu22-1359, 2022.

EGU22-1366 | Presentations | ST2.7

On the accuracy of selected empirical magnetopause models 

Maryam Aghabozorgi Nafchi, Frantisek Nemec, Gilbert Pi, Zdenek Nemecek, and Jana Safrankova

Empirical magnetopause models generally aim to predict its location as a function of upstream solar wind parameters. Many such models have been developed to date, typically based on the fitting of individual magnetopause crossings identified in spacecraft data by prescribed empirical functions deemed to reasonably characterize magnetopause shape and position dependences on selected control parameters. We use a unique list of more than 60,000 magnetopause crossings identified in THEMIS A-E, Magion, Geotail, and Interball spacecraft data to evaluate the performance of some of the most popular such models (Formisano et al., 1979; Petrinec and Russell, 1996; Shue et al., 1997; Lin et al., 2010). Differences between observed and model magnetopause locations are investigated as a function of solar wind dynamic pressure, interplanetary magnetic field magnitude, clock angle, and cone angle. A particular attention is paid to the magnetopause shape. This is studied both in terms of the level of the tail flaring, assuming a rotational symmetry around the aberrated x-axis, and in terms of asymmetries present in the real configuration. We show that although the Lin et al. (2010) model performs arguably the best, some systematic deviations are still present.

How to cite: Aghabozorgi Nafchi, M., Nemec, F., Pi, G., Nemecek, Z., and Safrankova, J.: On the accuracy of selected empirical magnetopause models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1366, https://doi.org/10.5194/egusphere-egu22-1366, 2022.

EGU22-1733 | Presentations | ST2.7

Pressure balance at the subsolar magnetopause: Statistical study 

Kostiantyn Grygorov, Zdenek Nemecek, Jana Safrankova, and Jiri Simunek

The magnetopause would be located at a point where the total pressure on the solar wind/magnetosheath side is equal to its magnetospheric counterpart. The upstream pressure is a sum of plasma thermal pressure and magnetic pressure whereas the magnetic pressure would strongly dominate on the magnetospheric side because the density of magnetospheric plasma is typically very low. Statistics of over ten years of THEMIS subsolar magnetopause (YGSM<5 RE) observations reveals that about 2 % of magnetopause crossings exhibit notably higher magnetic field in the magnetosheath than within the magnetosphere and thus the pressure balance is apparently violated. On the other hand, long series of multiple crossings suggest that the magnetopause is close to its equilibrium position and upstream and downstream pressures should be about equal. Interestingly, such crossings were found under both polarities of IMF BZ. In the paper, we study possible sources and mechanisms keeping the pressure balance. We discuss namely the upstream solar wind conditions and state of the outer magnetosphere. Comparison of these unusual magnetopause crossings with the rest of them shows that the cold plasma population coming to the magnetopause from the plasmasphere during periods of geomagnetic storms plays an important role in setting the pressure balance in the magnetopause region.

How to cite: Grygorov, K., Nemecek, Z., Safrankova, J., and Simunek, J.: Pressure balance at the subsolar magnetopause: Statistical study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1733, https://doi.org/10.5194/egusphere-egu22-1733, 2022.

EGU22-1765 | Presentations | ST2.7

Magnetospheric compressions, magnetopause shadowing and the last-closed-drift-shell 

Ravindra Desai, Jonathan Eastwood, Joseph Eggington, Jeremy Chittenden, and Richard Horne

Fluxes in the outer radiation belt can vary by orders of magnitude in response to solar wind driving conditions. Magnetopause shadowing, where electron and proton drift paths intersect the magnetopause boundary, is a fundamental loss process which operates on sub-day timescales and can result in rapid loss across the outer radiation belt. Accurate characterisation of this is therefore required to fully account for outer radiation belt dynamics and to avoid unrealistic fluxes impacting long-term forecasts. In this paper we utilise particle simulations of the radiation belts integrated within evolving global MHD simulations, to provide high-resolution high-fidelity simulations of the phenomenon of magnetopause shadowing. We model a variety of magnetopause compression scenarios corresponding to extreme cases of interplanetary shock impacts, and gradual increases in solar wind dynamic pressure. We thus constrain how time-dependent topological variation of the magnetospheric fields results in a complex interplay of open and closed particle drift paths, and examine the role of the electric field in modulating escaping particles trajectories as well as corresponding prompt injections into the inner magnetosphere.

How to cite: Desai, R., Eastwood, J., Eggington, J., Chittenden, J., and Horne, R.: Magnetospheric compressions, magnetopause shadowing and the last-closed-drift-shell, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1765, https://doi.org/10.5194/egusphere-egu22-1765, 2022.

EGU22-1969 | Presentations | ST2.7 | Highlight

Do we need to consider electrons’ kinetic effects to properly model a planetary magnetosphere? The case of Mercury 

Giovanni Lapenta, David Schriver, Raymond J. Walker, Jean Berchem, Nicole F. Echterling, Mostafa El Alaoui, and Pavel Travnicek

While a global full particle-in-cell (PIC) model of Earth’s magnetosphere cannot yet achieve enough resolution to be quantitatively accurate, the full model of smaller planets is becoming possible and can be used to learn what extra effects the full electron kinetic physics brings. From smaller planets we can learn much relevant also for the Earth. 

In this presentation, we investigate the global magnetosphere of Mercury using an implicit full particle in cell simulation (PIC). We use a hybrid simulation where ions are full particles and electrons are considered as a fluid to start a full PIC simulation where electrons are also particles (1836 mion/me) and follow their distribution function.

This approach allows us to estimate the changes introduced by the electron kinetic physics. We find that the overall macroscopic state of the magnetosphere of Mercury is little effected but several physical processes are significantly modified in the full PIC simulation: the foreshock region is more active with more intense shock reformation, the Kelvin-Helmholtz rippling effects on the nightside magnetopause are sharper, and the magnetotail current sheet becomes thinner than those predicted by the hybrid simulation.  The greatest effect of the electron physics comes from the processes of particle energization. Both species, not just the electrons, are found to gain more energy when kinetic electron processes are included. The region with the most energetic plasma is on the dusk side of the tail where magnetic flux ropes are formed due to reconnection. We find that the ion and electron energization is associated with the regions of reconnection and the development of kinetic instabilities caused by counter-streaming electron populations. The resulting electron distributions are highly non-Maxwellian, a process that neither MHD nor hybrid models can describe.

Reference: Lapenta, G., Schriver, D. Walker, R.J.,  Berchem, J., Echterling, N.F.,  El Alaoui, M., Travnicek, P., (2022) Do we need to consider electron kinetic effects to properly model a planetary magnetosphere: the case of Mercury, arXiv:2201.01653, submitted.

 

How to cite: Lapenta, G., Schriver, D., Walker, R. J., Berchem, J., Echterling, N. F., El Alaoui, M., and Travnicek, P.: Do we need to consider electrons’ kinetic effects to properly model a planetary magnetosphere? The case of Mercury, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1969, https://doi.org/10.5194/egusphere-egu22-1969, 2022.

EGU22-2939 | Presentations | ST2.7 | Highlight

Magnetospheric flux throughput in the Dungey cycle: identification of convection state during 2010 

Steve Milan, Jenny Carter, Harneet Sangha, Gemma Bower, and Brian Anderson

We quantify the contributions of different convection states to the magnetic flux through-put of the magnetosphere during 2010. To do this we provide a continuous classification of convection state for the duration of 2010 based upon observations of the solar wind and interplanetary magnetic field, geomagnetic indices, and field-aligned currents measured by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). Convection states are defined as 1) quiet and 2) weak activity, substorm 3) growth, 4) expansion, and 5) recovery phases, 6) substorm driven phase (when relatively steady magnetospheric convection occurs), 7) recovery bays (when recovery phase is accompanied by a negative excursion of the AL electrojet index), and 8) periods of multiple intensifications (storm-time periods when continuous short-period AL activity occur). The magnetosphere is quiet for 46% of the time, when very little convection takes place. The majority of convection occurs during growth and driven phases (21% and 38%, respectively, of open magnetic flux accumulation by dayside reconnection). We discuss these results in the context of the expanding/contracting polar cap model of convection, and describe a framework within which isolated substorms and disturbances during periods of more continuous solar wind-magnetosphere driving can be understood.

How to cite: Milan, S., Carter, J., Sangha, H., Bower, G., and Anderson, B.: Magnetospheric flux throughput in the Dungey cycle: identification of convection state during 2010, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2939, https://doi.org/10.5194/egusphere-egu22-2939, 2022.

EGU22-3166 | Presentations | ST2.7

Multiple Reconnection X-lines at the Magnetopause and Overlapping Cusp Ion Injections 

Stephen Fuselier, Craig Kletzing, Steven Petrinec, Karlheinz Trattner, Don George, Scott Bounds, Rhyan Sawyer, John Bonnell, James Burch, Barbara Giles, and Robert Strangeway

Magnetospheric Multiscale (MMS) observations during an extended crossing of the Earth’s dayside magnetopause show evidence of multiple reconnection at the boundary. This crossing occurred when the IMF was southward and had a significant BY component. Approximately two hours after this crossing, the Twin Rocket Investigation of Cusp Electrodynamics-2 (TRICE-2) rockets were launched into the northern hemisphere cusp and observed overlapping cusp ion injections. These overlapping injections are also evidence of multiple reconnection at the magnetopause. While the observations more than 2 hours apart do not constitute a conjunction between the spacecraft and the rockets, the IMF conditions during the magnetopause crossing and the cusp traversal were very similar. Therefore, had the magnetopause crossings and cusp traversals occurred at the same time, the observations would have been similar. This talk describes these observations and shows the link between multiple reconnection at the magnetopause and overlapping cusp ion injections. In addition, the global consequences on the magnetosphere from this link are discussed.

How to cite: Fuselier, S., Kletzing, C., Petrinec, S., Trattner, K., George, D., Bounds, S., Sawyer, R., Bonnell, J., Burch, J., Giles, B., and Strangeway, R.: Multiple Reconnection X-lines at the Magnetopause and Overlapping Cusp Ion Injections, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3166, https://doi.org/10.5194/egusphere-egu22-3166, 2022.

EGU22-3173 | Presentations | ST2.7

Polar Cap Boundary Reaction to Geomagnetic Storms 

Joachim Raeder, Beket Tulegenov, William D. Cramer, Banafsheh Ferdousi, Timothy Fuller-Rowell, Naomi Maruyama, and Robert J. Strangeway

It is well known that the polar cap, delineated by the Open
Closed field line Bound ary (OCB), responds to changes in the
Interplanetary Magnetic Field (IMF). In general, the boundary
moves equatorward when the IMF turns southward and contracts
poleward when the IMF turns northward. However, observations of
the OCB are spotty and limited in local time, making more
detailed studies of its IMF dependence difficult. Here, we
simulate five solar storm periods with the coupled
OpenGGCM-RCM-CTIM model to estimate the location and dynamics of
the OCB. For these events, polar cap boundary location
observations are also obtained from Defense-Meteorological
Satellite Pro- gram (DMSP) precipitation spectrograms and
compared with the model output. There is a large scatter in the
DMSP observations and in the model output. However, we generally
find good agreement between the model and the observations. On
average, the model overestimates the latitude of the open-closed
field line boundary by 1.61◦. Additional analysis of the
simulated polar cap boundary dynamics across all local times
shows that the MLT of the largest polar cap expansion closely
correlates with the IMF clock angle; that the strongest
correlation occurs when the IMF is southward; that during strong
southward IMF the polar cap shifts sunward; and that the polar
cap rapidly contracts at all local times when the IMF turns
northward.

How to cite: Raeder, J., Tulegenov, B., Cramer, W. D., Ferdousi, B., Fuller-Rowell, T., Maruyama, N., and Strangeway, R. J.: Polar Cap Boundary Reaction to Geomagnetic Storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3173, https://doi.org/10.5194/egusphere-egu22-3173, 2022.

EGU22-3196 | Presentations | ST2.7 | Highlight

Magnetosphere simulations with ideal MHD, Hall MHD and the MHD with Adaptively Embedded Particle-in-Cell (MHD-AEPIC) models 

Gabor Toth, Xiantong Wang, and Yuxi Chen

The Magnetohydrodynamic with Embedded Particle-In-Cell (MHD-EPIC) model has been developed and applied successfully to Earth, Mercury, Mars and Ganymede magnetosphere simulations. While MHD-EPIC is many orders of magnitude faster than a fully kinetic global model, it can become prohibitively slow if the potential region of interest where kinetic phenomena, such as magnetic reconnection, can occur is large. This is due to the fact that the PIC domain in MHD-EPIC is restricted to a set of static Cartesian boxes. For example, a very large PIC box would be needed to accommodate the flapping motion of the magnetotail current sheet during a geomagnetic storm simulation. To tackle this problem, we have developed a new MHD with Adaptively Embedded Particle-In-Cell (MHD-AEPIC) model. MHD-AEPIC inherits all numerical algorithms from MHD-EPIC and incorporates a new adaptive PIC model, the Flexible Kinetic Simulator (FLEKS). FLEKS allows the PIC cells to be activated and deactivated during a simulation. The coupling between the MHD model and the adaptive PIC grid has been developed and implemented into the Space Weather Modeling Framework. We have also developed physics-based criteria to identify potential reconnection sites, which makes the adaptation fully automatic. In this work, we apply the new MHD-AEPIC model to a geomagnetic storm simulation and demonstrate how adaptation makes this simulation feasible. We compare MHD-AEPIC, Hall MHD and ideal MHD simulation results with each other and with observations ranging from electron scales to global scales. In particular, we demonstrate that MHD-AEPIC is capable of reproducing electron-scale physics in a global simulation.

How to cite: Toth, G., Wang, X., and Chen, Y.: Magnetosphere simulations with ideal MHD, Hall MHD and the MHD with Adaptively Embedded Particle-in-Cell (MHD-AEPIC) models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3196, https://doi.org/10.5194/egusphere-egu22-3196, 2022.

EGU22-3429 | Presentations | ST2.7

Subgrid modelling of pitch-angle diffusion for ion-scale waves in a global hybrid-Vlasov simulation 

Maxime Dubart, Markus Battarbee, Urs Ganse, Felix Spanier, Jonas Suni, Andreas Johlander, Markku Alho, Maarja Bussov, Giulia Cozzani, Harriet George, Maxime Grandin, Talgat Manglayev, Kostis Papadakis, Yann Pfau-Kempf, Vertti Tarvus, Lucile Turc, Ivan Zaitsev, Hongyang Zhou, and Minna Palmroth

Numerical simulations play a central role in modern sciences. The trade-off between the accuracy of the physical processes described and the cost of computational resources is often the main limiting factor in these simulations. In global hybrid-Vlasov simulations, such as Vlasiator, lowering the spatial resolution in order to save on resources can lead to key processes being unresolved. A previous study has shown how insufficient resolution of the proton cyclotron instabilities leads to a misrepresentation of ion dynamics. This leads to larger temperature anisotropy and loss-cone shaped velocity distribution functions. In this study, we present a numerical model to introduce pitch-angle diffusion in velocity space, at a spatial resolution where this process was previously not correctly resolved. We test two different methods to enable pitch-angle diffusion in the 3D cartesian velocity space of Vlasiator. We show that we are successfully able to isotropise loss-cone shaped velocity distribution functions, and that this method could be applied to large simulations in order to save computational resources and still correctly model the Earth's magnetosheath.

How to cite: Dubart, M., Battarbee, M., Ganse, U., Spanier, F., Suni, J., Johlander, A., Alho, M., Bussov, M., Cozzani, G., George, H., Grandin, M., Manglayev, T., Papadakis, K., Pfau-Kempf, Y., Tarvus, V., Turc, L., Zaitsev, I., Zhou, H., and Palmroth, M.: Subgrid modelling of pitch-angle diffusion for ion-scale waves in a global hybrid-Vlasov simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3429, https://doi.org/10.5194/egusphere-egu22-3429, 2022.

EGU22-3465 | Presentations | ST2.7

Multi-scale observations and evolution of the magnetopause Kelvin-Helmholtz waves during southward IMF 

Kevin Alexander Blasl, Takuma Nakamura, Ferdinand Plaschke, Rumi Nakamura, Hiroshi Hasegawa, Julia E. Stawarz, Yi-Hsin Liu, Sarah A. Peery, Justin C. Holmes, Martin Hosner, Daniel Schmid, Owen Wyn Roberts, and Martin Volwerk

The mass and energy transfer across Earth’s magnetopause is caused by a variety of different plasma processes. One of these processes is the Kelvin-Helmholtz instability (KHI), excited by the velocity shear between the fast-flowing magnetosheath plasma and the relatively stagnant magnetosphere. It has been frequently observed during periods of northward interplanetary magnetic field (IMF), however much less is known about its behaviour during southward IMF conditions.

We present the first Magnetospheric Multiscale (MMS) observations of KH waves and vortices at the dusk-flank magnetopause during southward IMF conditions on September 23, 2017. The instability criterion for the KHI was fulfilled during this event. The boundary normal vectors, obtained by using multi-point methods, are consistent with the predicted structures of the KH waves. We further performed a series of realistic 2D and 3D fully kinetic PIC simulations based on the plasma parameters observed during this MMS event. A comparison to results from these simulations demonstrated quantitative consistencies with the MMS data in many aspects such as the flow and total pressure variations in the KH waves, and the signatures of the non-linearly rolled up KH vortices including the Low Density Faster Than Sheath (LDFTS) plasma.

The simulations further showed that secondary instabilities are excited at the edges of the primary KHI. The Rayleigh-Taylor instability (RTI) can lead to the penetration of high-density arms into the magnetospheric side and disturb the structures of the vortex layer, leading to irregular variations of the surface waves. This can be an important factor in explaining the lower observational probability of KH waves during southward IMF than northward IMF. In the non-linear growth stage of the primary KHI, the lower-hybrid drift instability (LHDI) is excited at the vortex edges leading to efficient plasma mixing across the magnetopause.

The high-time resolution of MMS measurements demonstrated the occurrence of kinetic-scale plasma waves mainly on the low-density side of the edges of the KH waves. Given quantitative consistencies with the simulations, these waves can be interpreted as being generated by the LHDI. These observed waves form due to the strong density gradient between the two sides of the boundary layer and can lead to a flattening of the edge layers.


In this presentation, we will show the consistencies between MMS observations and 2D and 3D simulation runs focusing on the large-scale surface waves (KHI, RTI) and the small-scale fluctuations (LHDI) and outline the multi-scale properties of the observed KH waves during southward IMF.

How to cite: Blasl, K. A., Nakamura, T., Plaschke, F., Nakamura, R., Hasegawa, H., Stawarz, J. E., Liu, Y.-H., Peery, S. A., Holmes, J. C., Hosner, M., Schmid, D., Roberts, O. W., and Volwerk, M.: Multi-scale observations and evolution of the magnetopause Kelvin-Helmholtz waves during southward IMF, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3465, https://doi.org/10.5194/egusphere-egu22-3465, 2022.

EGU22-3573 | Presentations | ST2.7 | Highlight

Substorm onset and current sheet flapping in a 6D global ion-kinetic simulation 

Minna Palmroth, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Jonas Suni, Maxime Grandin, Lucile Turc, Markus Battarbee, Andreas Johlander, Vertti Tarvus, Hongyang Zhou, Maarja Bussov, Maxime Dubart, Harriet George, Konstantinos Horaites, Talgat Manglayev, Konstantinos Papadakis, Rumi Nakamura, and Tuija Pulkkinen

Among the most unpredictable phenomena within the near-Earth space are substorms, periods of energy loading and explosive release within the magnetospheric tail. Substorms are global, as energy is extracted from the solar wind via dayside reconnection, while the tail energy release takes place in a vast domain within a few tens of seconds. Due to the scarcity of space-borne observations, it has been difficult to conclusively separate between the onset scenarios that include magnetic reconnection and various ion-kinetic instabilities, which occur at mesoscales, and small scales. Another decades-long investigation concerns the flapping of the plasma sheet, occurring within a large area favouring the substorm growth phase, although it has been observed at other times as well. Mechanisms to explain the flapping are presently unknown. Modelling efforts have failed to explain the substorm onset either because all the required physics has not been included in the simulation, or the simulation does not cover the entire domain, thus possibly missing important drivers. Vlasiator is a  model describing the global magnetosphere accurately at ion-kinetic scales, including the ion-kinetic effects that are absent in the fluid descriptions. Unlike many other kinetic simulations, Vlasiator extends the simulation domain to global scales and accurately represents the Earth’s unscaled magnetosphere from the dayside to the tail, in six dimensions including the 3D real space and 3D velocity space without noise that is present in the alternative PIC method. We present the first global 6D simulation encompassing the entire near-Earth space to simulate ion-kinetic magnetospheric dynamics self-consistently. We determine reconnection, ion-kinetic instabilities, plasma sheet flapping, and bursty bulk flows in the simulation domain, and show how they all contribute to the whole and work in concert in developing the substorm onset. Our results help to understand spacecraft measurements and the overall substorm process, which will significantly improve understanding space physics and eventually space weather. Our results can also be used in strategies to design a mission, which will finally and conclusively capture the substorm onset with in situ measurements.

How to cite: Palmroth, M., Ganse, U., Pfau-Kempf, Y., Alho, M., Suni, J., Grandin, M., Turc, L., Battarbee, M., Johlander, A., Tarvus, V., Zhou, H., Bussov, M., Dubart, M., George, H., Horaites, K., Manglayev, T., Papadakis, K., Nakamura, R., and Pulkkinen, T.: Substorm onset and current sheet flapping in a 6D global ion-kinetic simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3573, https://doi.org/10.5194/egusphere-egu22-3573, 2022.

EGU22-5549 | Presentations | ST2.7

Using the Virial Theorem to Analyze Effects of Energy Dynamics in the Magnetosphere 

Austin Brenner, Tuija Pulkkinen, Gabor Toth, Qusai Al Shidi, and Mike Liemohn

The solar wind couples with Earth’s magnetosphere driving plasma dynamics which can create magnetic perturbations at Earth’s surface impacting life on the ground. One classic way of understanding this process is via the Dungey cycle where magnetic flux is injected into the magnetosphere on the dayside via a dayside reconnection site. This flux is then transported downstream and is released from the magnetosphere via a tail reconnection site, bringing high hydrodynamic energy plasma earthward which becomes trapped in the ring current, leading to intense sustained magnetic perturbation.

In this work, we take a closer look at this process using 3D MHD results from the Space Weather Modeling Framework. Building off previous work by Brenner et al. 2021, the magnetopause surface is identified in the simulation domain to a fixed downstream tail distance. This 3D volume is then split into regions based on magnetic topology and L shell location. From here two methods are used to describe the magnetic perturbation resulting from each region. The first is using the Biot-Savart law that integrates current density vectors weighted by position and direction. The second uses the virial theorem which employs the scalar product of momentum with the position vector integrated over the magnetosphere. The latter formulation is advantageous since it directly relates the magnetic perturbation with stress terms at the magnetopause boundary and volume integrated energy density in the magnetosphere.

Results from the Biot Savart integration and virial theorem are compared with observations of ground based magnetic perturbations to study the effects of energy transport within the system during a simulated storm event.

How to cite: Brenner, A., Pulkkinen, T., Toth, G., Al Shidi, Q., and Liemohn, M.: Using the Virial Theorem to Analyze Effects of Energy Dynamics in the Magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5549, https://doi.org/10.5194/egusphere-egu22-5549, 2022.

EGU22-5653 | Presentations | ST2.7

Magnetospheric Responses to Solar Wind Pc5 Density Fluctuations: Results from 2D Hybrid Vlasov Simulation 

Hongyang Zhou, Lucile Turc, Vertti Tarvus, Yann Pfau-Kempf, Markus Battarbee, Maxime Dubart, Urs Ganse, Markku Alho, Maxime Grandin, Harriet George, Jonas Suni, Maarja Bussov, Konstantinos Papadakis, Talgat Manglayev, Kosta Horaites, Ivan Zaitsev, Giulia Cozzani, and Minna Palmroth

Ultra-low frequency (ULF) waves in the Pc5 range, with periods between 150 – 600 s, play a key role in the dynamics of Earth’s magnetosphere, in particular through their interaction with radiation belt electrons. One important source of magnetospheric Pc5 waves are fluctuations of the upstream solar wind parameters in the same frequency range. Pressure variations in the solar wind are thought to result in a forced breathing of the magnetosphere, as the magnetosphere would expand and compress in response to the changing upstream conditions, which drives ULF waves inside the magnetosphere. The details of the interaction of these solar wind variations with the Earth’s bow shock and magnetosheath, their impact on the magnetosheath plasma properties and how the fluctuations would change before reaching the magnetopause, remain however unclear. In this study, we investigate the influence of externally-driven variations across near-Earth space using global 2D simulations performed with the hybrid-Vlasov model Vlasiator. The new time-varying boundary setup in Vlasiator allows us to set Pc5 periodic density pulses coming from the upstream. The density pulses cause the breathing motion of the bow shock, create clear stripes of variations inside the magnetosheath, and modulate the electromagnetic ion cyclotron (EMIC) and mirror modes. We characterize the spatial-temporal variations of waves on the simulation plane within the magnetosheath and discuss the potential impact on the near-Earth environment.

How to cite: Zhou, H., Turc, L., Tarvus, V., Pfau-Kempf, Y., Battarbee, M., Dubart, M., Ganse, U., Alho, M., Grandin, M., George, H., Suni, J., Bussov, M., Papadakis, K., Manglayev, T., Horaites, K., Zaitsev, I., Cozzani, G., and Palmroth, M.: Magnetospheric Responses to Solar Wind Pc5 Density Fluctuations: Results from 2D Hybrid Vlasov Simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5653, https://doi.org/10.5194/egusphere-egu22-5653, 2022.

EGU22-5654 | Presentations | ST2.7 | Highlight

Global three-dimensional draping of magnetic field in Earth's magnetosheath from in-situ measurements 

Bayane Michotte de Welle, Nicolas Aunai, Gautier Nguyen, Benoit Lavraud, Vincent Genot, Roch Smets, and Alexis Jeandet

Understanding where the magnetic reconnection occurs at the Earth’s magnetopause is one of the important remaining questions about this phenomena. Since the last decades various models predicting the position of the X-line have been made. These models largely depend on the orientation of the magnetic field in the magnetosheath close to the magnetopause, such as the Maximum Magnetic Shear model (Trattner et al 2007). Therefore understanding how it  is structured as a function of the solar wind and interplanetary magnetic field is of pivotal importance. Machine learning was used to collect around 45 million measurements in the magnetosheath at 5s resolution in all available Cluster, MMS, Double Star, THEMIS dataset, and to build detailed maps of the field structure in that region as a function of the IMF orientation. It allowed us to reconstruct for the first time the three dimensional magnetic field draping in the dayside magnetosheath from in-situ data only. Our results reveal how the frozen-in condition constrains the draping around the magnetopause. A comparison of the draping obtained with in-situ data with the one from a widely used magnetostatic model (Kobel et al 1994) was made. Differences of up to 180° were found for cone angle between 12.5° and 45°, for which the consequences regarding the position of the X-line will be discussed. 

 

How to cite: Michotte de Welle, B., Aunai, N., Nguyen, G., Lavraud, B., Genot, V., Smets, R., and Jeandet, A.: Global three-dimensional draping of magnetic field in Earth's magnetosheath from in-situ measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5654, https://doi.org/10.5194/egusphere-egu22-5654, 2022.

EGU22-6954 | Presentations | ST2.7

The relationship between dayside and nightside Dynamics under northward interplanetary magnetic field substorms 

Reham Elhawary, Karl Laundal, Jone Reistad, Anders Ohma, Spencer Hatch, and Sara Gasparini

Substorms that occur under northward interplanetary magnetic field (IMF) conditions can elucidate the relationship between the dayside and nightside dynamics of the ionosphere. We investigate the relationship between the dayside and the nightside dynamics in response to northward IMF substorms. While the dynamics of the dayside ionosphere are directly related to the interaction between the solar wind interplanetary magnetic field (IMF) and the earth’s magnetic field, the dynamics in the nightside are strongly controlled by magnetotail activity like substorms. Under southward IMF conditions, both reconnection on the dayside and substorms on the nightside increase Dungey convection, making it difficult to distinguish the separate contributions of dayside and nightside processes to large-scale dynamics. Under northward IMF conditions, on the other hand, it is easier to distinguish between dayside and nightside processes, since northward IMF does not increase Dungey flows. We present a superposed epoch analysis of the equivalent current and magnetic perturbations above 60 deg magnetic latitude (mlat) from ground-based magnetometer stations based on 280 northward IMF substorms. We also investigate whether the dayside current pattern is influenced by the substorm onset.

How to cite: Elhawary, R., Laundal, K., Reistad, J., Ohma, A., Hatch, S., and Gasparini, S.: The relationship between dayside and nightside Dynamics under northward interplanetary magnetic field substorms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6954, https://doi.org/10.5194/egusphere-egu22-6954, 2022.

EGU22-7248 | Presentations | ST2.7

Magnetosheath jet occurrence in solar wind parameter space 

Ferdinand Plaschke, Florian Koller, Luis Federico Preisser Renteria, Adrian T. LaMoury, Heli Hietala, Manuela Temmer, and Owen Wyn Roberts

Plasma jets in the magnetosheath are identified as strong local enhancements in dynamic pressure. Being created at the bow shock, they are able to traverse the entire magnetosheath and impact the magnetopause. There, they can severely indent the boundary, set up waves on it, and trigger magnetic reconnection. They are a key yet heavily underexplored element in the solar wind – magnetosphere coupling. Jets are mostly (but not exclusively) observed downstream of the quasi-parallel shock. Consequently, they have been observed significantly more often under low interplanetary magnetic field cone angle conditions.

In this study, we revisit the occurrence of jets, this time taking into account the whole space of parameters of solar wind input conditions. We answer the question where in this space jet occurrences cluster and how the emerging patterns change when the solar wind input becomes significantly different in nature, e.g., under the influence of coronal mass ejections or stream interaction regions.

How to cite: Plaschke, F., Koller, F., Preisser Renteria, L. F., LaMoury, A. T., Hietala, H., Temmer, M., and Roberts, O. W.: Magnetosheath jet occurrence in solar wind parameter space, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7248, https://doi.org/10.5194/egusphere-egu22-7248, 2022.

EGU22-7611 | Presentations | ST2.7 | Highlight

Proton precipitation in a hybrid-Vlasov simulation with southward interplanetary magnetic field driving: First 3D results 

Maxime Grandin, Thijs Luttikhuis, Markku Alho, Markus Battarbee, Maarja Bussov, Giulia Cozzani, Maxime Dubart, Urs Ganse, Harriet George, Konstantinos Horaites, Talgat Manglayev, Konstantinos Papadakis, Yann Pfau-Kempf, Jonas Suni, Vertti Tarvus, Lucile Turc, Ivan Zaitsev, Hongyang Zhou, and Minna Palmroth

The precipitation of charged particles from the magnetosphere into the ionosphere is one of the crucial coupling mechanisms between these two regions of geospace. While precipitating particle fluxes have been measured by numerous spacecraft missions over the past decades, it often remains difficult to obtain global precipitation patterns with a good time resolution during a substorm. Numerical simulations can contribute to bridge this gap and help improve the understanding of mechanisms leading to particle precipitation at high latitudes through the global view they offer on the near-Earth space system. We present the first results on proton precipitation within a 3-dimensional simulation of the Vlasiator hybrid-Vlasov model. The run is driven by southward interplanetary magnetic field conditions with steady solar wind parameters. We analyse the large-scale proton precipitation pattern in both hemispheres and discuss its dynamics in relation to the processes taking place in the magnetotail.

How to cite: Grandin, M., Luttikhuis, T., Alho, M., Battarbee, M., Bussov, M., Cozzani, G., Dubart, M., Ganse, U., George, H., Horaites, K., Manglayev, T., Papadakis, K., Pfau-Kempf, Y., Suni, J., Tarvus, V., Turc, L., Zaitsev, I., Zhou, H., and Palmroth, M.: Proton precipitation in a hybrid-Vlasov simulation with southward interplanetary magnetic field driving: First 3D results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7611, https://doi.org/10.5194/egusphere-egu22-7611, 2022.

EGU22-7637 | Presentations | ST2.7

The role of ionospheric convection in shaping the auroral oval 

Sara Gasparini, Karl M. Laundal, Jone P. Reistad, Anders Ohma, Spencer Hatch, and Reham Elhawary

The solar wind’s embedded interplanetary magnetic field (IMF) impinging on the Earth’s magnetosphere has an impact on the terrestrial environment. The primary mechanism which allows for direct interaction between the solar wind and the terrestrial environment is magnetic reconnection on the Earth’s dayside between the IMF and the Earth’s magnetic field. Changes in the IMF result in a change of magnetic reconnection rates at the Earth’s dayside leading to changes in the auroral oval morphology/topology. The auroral oval is rather dynamic, and its variability is currently not well understood. We hypothesise that much of this variability is due to variations in ionospheric convection. We interpret its temporal and morphological variability in terms of ionospheric convection and dayside and nightside reconnection rates, (i.e., the "expanding/contracting polar cap" paradigm). Dayside reconnection is responsible for opening magnetic flux on the dayside and initiating ionospheric flows whereas nightside reconnection is ensuring closure of open magnetic field lines. In this study we infer convection patterns with SuperDARN (Super Dual Auroral Radar Network) measurements and ground-based magnetometers data (SuperMAG) using a new data assimilation technique. We combine convection flows with auroral precipitation patterns and solar wind parameters to understand the behavior of the auroral oval and the physical mechanisms that drive its dynamical changes. By examining both the dynamic evolution of the ionospheric convection and the corresponding dynamics of the colocated auroral forms seen in global UV images, we investigate to what extent convection can be associated with the changes observed in the large scale auroral boundaries in selected events. 

How to cite: Gasparini, S., Laundal, K. M., Reistad, J. P., Ohma, A., Hatch, S., and Elhawary, R.: The role of ionospheric convection in shaping the auroral oval, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7637, https://doi.org/10.5194/egusphere-egu22-7637, 2022.

Large-scale global three-dimensional PIC simulations are used in order to analyze the dynamics of the cusp boundaries and particle fluxes penetrating the cusp as the interplanetary magnetic field (IMF) rotates from northward to dawn-dusk direction. Recent 3D simulation works have been previously focussed on the formation of so called Alfven Transition Layer (ATL) located at the upper edge of the Stagnant Exterior Cusp (SEC) as evidenced originally in CLUSTER data (Lavraud et al., 2005) and on 3D dynamics of  electron / ion fluxes penetrating the cusp (Cai et al., 2015; Lembege et al., 2022), but  have been restricted to the northward direction of the IMF. The ATL is defined as a transition layer through which the plasma flow changes its bulk velocity from super-Alfenic regime (in the magnetosheath) to a sub-Alfvenic regime (in the ESC). The present work is an extension of these previous works and is focussed on the impact of the IMF rotation: (i) on the formation and the structure of the cusp itself, (iii) on the size, the location and the 3D features of the ATL, and (iii) on the 3D dynamics of the electron/ion fluxes when penetrating the cusp region. These preliminary results will be compared with those already obtained for a northward IMF. 

How to cite: Cai, D. and Lembege, B.: How the cusp features  and the Alfven Transition Layer are affected by  the IMF Rotation from North to dawn-dusk  direction ?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9508, https://doi.org/10.5194/egusphere-egu22-9508, 2022.

EGU22-9701 | Presentations | ST2.7 | Highlight

What are the ionospheric and ground magnetic signatures of global magnetopause surface modes? 

Martin Archer, Joseph Eggington, Michael Hartinger, Michael Heyns, Ferdinand Plaschke, Lutz Rasaetter, Xueling Shi, David Southwood, and Andrew Wright

Surface waves on Earth’s magnetopause act as an efficient mechanism of filtering, accumulating, and guiding the turbulent disturbances present in the solar wind into terrestrial space, thereby playing a key role in controlling global magnetospheric dynamics. However, it is difficult to directly measure these processes since orbiting spacecraft often only provide sparse observation points. It would, therefore, be desirable to be able to remote sense magnetopause surface modes via ionospheric radar or networks of ground magnetometers. The Alfvénic signatures of localised, tailward propagating magnetopause surface waves in ionospheric and ground magnetometer data are somewhat established. However, those associated with the global-scale compressional surface eigenmodes – the lowest frequency and largest-scale normal mode of the magnetospheric system – remain poorly understood. In this presentation we discuss how high-resolution global magnetosphere simulations coupled to an ionosphere model may be able to predict the qualitative features expected in ground-based instruments. Finally, we compare the results of our simulation to simple theory and reported potential observations.

How to cite: Archer, M., Eggington, J., Hartinger, M., Heyns, M., Plaschke, F., Rasaetter, L., Shi, X., Southwood, D., and Wright, A.: What are the ionospheric and ground magnetic signatures of global magnetopause surface modes?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9701, https://doi.org/10.5194/egusphere-egu22-9701, 2022.

EGU22-10242 | Presentations | ST2.7

Magnetospheric Source of a Transpolar Auroral Arc: Coupled SWMF Simulation results 

Shannon Hill, Tuija Pulkkinen, Qusai Al Shidi, Austin Brenner, Agnit Mukhopadhyay, Shasha Zou, and Michael Liehmon

We present the first coupled MHD-ring current simulation results that produce the global transpolar auroral arc phenomenon. We examine a unique observation of a midnight transpolar auroral arc that is produced during compressed magnetosphere conditions and persistent into an extended interval of southward IMF and substorm onset. The IMAGE satellite FUV-WIC camera observed the transpolar auroral arc in the southern hemisphere on 15 May 2005. The IMAGE observations show that the transpolar auroral arc originates at 24 MLT and stretches sunward across the polar cap to form a theta aurora with dusk-dawn motion that does not correspond with IMF By sign reversal or continuous magnitude decrease. Even though the theta aurora is typically a northern IMF phenomenon, the IMAGE observations show that the theta aurora persisted for almost an hour under disturbed geomagnetic conditions with peak AL below -1500 nT and Dst around -100 nT. We use the University of Michigan Space Weather Modeling Framework (SWMF) global geospace simulation to study the ionospheric conditions and magnetotail configuration throughout the observation period. Our SWMF simulation results show good agreement with the observed SYM-H and AL indices during the event interval. In the simulation, we identify peaks in Joule heating, precipitation, and anti-sunward flows in the region where the theta aurora is observed. We also demonstrate the temporal evolution of the open-closed field line boundary with respect to the observed theta aurora location, which suggests that the theta aurora is a closed field line phenomenon. We analyze the open-closed field line boundary mapping into the magnetotail and search for causes of precipitation within the simulation as well as analyze the hemispheric conjugacy of the event.

How to cite: Hill, S., Pulkkinen, T., Al Shidi, Q., Brenner, A., Mukhopadhyay, A., Zou, S., and Liehmon, M.: Magnetospheric Source of a Transpolar Auroral Arc: Coupled SWMF Simulation results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10242, https://doi.org/10.5194/egusphere-egu22-10242, 2022.

EGU22-11257 | Presentations | ST2.7

Explicit IMF By-dependence of magnetospheric energetic protons and the ring current 

Lauri Holappa and Natalia Buzulukova

The interaction of the solar wind with the Earth’s magnetic field produces geomagnetic activity, which is critically dependent on the orientation of the interplanetary magnetic field (IMF). While the dawn-dusk (By) component of the IMF is known to play an important role in this interaction, its effects are usually assumed to be independent of its sign. However, recent studies have shown that auroral electrojets and substorm activity are stronger for By < 0 in Northern Hemisphere (NH) summer. This so-called explicit By-dependence is reversed for NH winter. Here we study how IMF By modulates magnetospheric energetic protons and the ring current by using measurements of NOAA POES satellites and the Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model coupled in with the global BATSRUS MHD code. We show that the energetic magnetospheric protons and the ring current (Dst index) exhibit an explicit By-dependence (stronger for By < 0 in NH summer), which can be reproduced by the model. Our results highlight the importance of the IMF By component for space weather and must be taken into account in the future space weather modeling.

How to cite: Holappa, L. and Buzulukova, N.: Explicit IMF By-dependence of magnetospheric energetic protons and the ring current, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11257, https://doi.org/10.5194/egusphere-egu22-11257, 2022.

EGU22-11573 | Presentations | ST2.7

Magnetosheath jets and their dynamical properties derived from an analysis of Cluster data at solar minimum (2007,2008) 

Marius Echim, Mirela Voiculescu, Costel Munteanu, Gabriel Voitcu, Eliza Teodorescu, Simona Condurache-Bota, Emilian Bujor Dănilă, and Cătălin Negrea

We analize magnetosheath Cluster data from 2007 and 2008, included in FP7 STORM database (http://www.storm-fp7.eu). We identify magnetosheath jets based on a procedure that searches for significant departures of the local dynamic pressure from an average value.  The latter  is estimated from a running window spanning 20 minutes of data. The selection criterion is applied on Cluster 3 dataset and identifies 955 magnetosheath jets, with a notable difference between 2007 and 2008 (352 versus 603 events). The statistical analysis of the plasma bulk velocity, density, temperature, plasma beta, magnetic field and radial distance of the jets provides interesting elements for understanding their dynamics. There is evidence for deceleration of jets with decreasing distance from the Earth; interestingly, this trend manifests more clearly for jets detected in 2008. More jets are found in the dawn than in the dusk flank, for 2007 and 2008.  A comparison with the plasma parameters of the driver, the IMF Bz and the solar wind dynamic pressure from OMNI database, indicate there is no preference in terms of Bz polarity. The distribution of jet magnetic field, temperature (parallel, perpendicular), dynamic pressure, plasma beta and total speed is symetric when organized as a function of IMF Bz, with one exception, the jet perpendicular temperature and plasma beta. An increased solar wind dynamic pressure seems to correlate to higher values of the jet density but not velocity. We discuss these results in the context of previous similar magnetosheath jet analysis performed on MMS and THEMIS data.

How to cite: Echim, M., Voiculescu, M., Munteanu, C., Voitcu, G., Teodorescu, E., Condurache-Bota, S., Bujor Dănilă, E., and Negrea, C.: Magnetosheath jets and their dynamical properties derived from an analysis of Cluster data at solar minimum (2007,2008), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11573, https://doi.org/10.5194/egusphere-egu22-11573, 2022.

EGU22-12309 | Presentations | ST2.7

Morphology of the ionospheric convection pattern during time-dependent solar wind and magnetospheric driving 

Adrian Grocott and Maria-Theresia Walach

We use an 18 year database of Super Dual Auroral Radar Network (SuperDARN) data to investigate the morphology of the large-scale ionospheric convection pattern. In particular, we look statistically at the location of the foci of the dawn and dusk convection cells which, according to the theoretical picture of Cowley and Lockwood (1992), are expected to move towards the dayside (nightside) when the Dungey cycle is dominated by magnetopause (magnetotail) reconnection. We use concurrent observations of the solar wind and interplanetary magnetic field to provide a proxy for the level of magnetopause reconnection and ground magnetic indices such as AL to provide an indication of the expected level of magnetotail reconnection. We find that, on average, the cell foci do move as predicted by the theory, but the presence of significant variability is consistent with additional factors being involved in governing the convection morphology at any given instant.

Cowley, S. W. H., and M. Lockwood (1992), Excitation and decay of solar wind-driven flows in the magnetosphere-ionosphere system, Ann. Geophysicae, 10, 103-115.

How to cite: Grocott, A. and Walach, M.-T.: Morphology of the ionospheric convection pattern during time-dependent solar wind and magnetospheric driving, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12309, https://doi.org/10.5194/egusphere-egu22-12309, 2022.

EGU22-12946 | Presentations | ST2.7 | Highlight

Controlling Effect of the Cold Plasma Density on Acceleration and Loss of Electrons at Ultra-Relativistic Energies 

Yuri Y. Shprits, Hayley Allison, Alexander Drozdov, Dedong Wang, Nikita Aseev, Irina Zhelavskaya, and Maria Usanova

Measurements from the Van Allen Probes mission clearly demonstrated that the radiation belts cannot be considered as a bulk population above approximately electron rest mass. Ultra-relativistic electrons (~>4Mev) form a new population that shows a very different morphology (e.g. very narrow remnant belts) and slow but sporadic acceleration.

We show that acceleration to multi-MeV energies can not only result of two-step processes consisting of local heating and radial diffusion but occurs locally due to energy diffusion by whistler-mode waves. Local heating appears to be able to transport electrons in energy space from 100s of keV all the way to ultra-relativistic energies (>7MeV) and is a dominant process for acceleration to ultra-relativistic energies. Acceleration to such high energies occurs only for the conditions when cold plasma in the trough region is extremely depleted down to the values typical for the plasma sheet.

There is also a clear difference between the loss mechanisms at MeV and multi MeV energies. The difference between the loss mechanisms at MeV and multi-MeV energies is due to EMIC waves, that can very efficiently scatter ultra-relativistic electrons, but leave MeV electrons unaffected.

These observations and modelling clearly show that cold plasma at eV energies has a controlling effect on the trapped electrons at energies seven orders of magnitude more energetic. Depletion in cold plasma is a requirement for acceleration while fast loss occurs only in the regions of high plasma density.

We also present how the new understanding gained from the Van Allen Probes mission can be used to produce the most accurate data assimilative forecast. Under the recently funded EU Horizon 2020 Project Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER) we will study how ensemble forecasting from the Sun can produce long-term probabilistic forecasts of the radiation environment in the inner magnetosphere.

How to cite: Shprits, Y. Y., Allison, H., Drozdov, A., Wang, D., Aseev, N., Zhelavskaya, I., and Usanova, M.: Controlling Effect of the Cold Plasma Density on Acceleration and Loss of Electrons at Ultra-Relativistic Energies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12946, https://doi.org/10.5194/egusphere-egu22-12946, 2022.

EGU22-536 | Presentations | ST2.8 | Highlight

Coordinated observations of relativistic electron enhancements following the arrival of consecutive Corotating Interaction Regions 

Afroditi Nasi, Ioannis A. Daglis, Christos Katsavrias, Ingmar Sandberg, Wen Li, Hayley Allison, Yoshizumi Miyoshi, Shun Imajo, Takefumi Mitani, Tomo Hori, Yuri Shprits, Satoshi Kasahara, Shoichiro Yokota, Kunihiro Keika, Iku Shinohara, Ayako Matsuoka, and Yoshiya Kasahara

During July-October of 2019, a sequence of Corotating Interaction Regions (VSW ≥ 600 km/s) impacted the magnetosphere, for four consecutive solar rotations. Even though the series of CIRs resulted in relatively weak geomagnetic storms (SYM-Hmin ≈ -60 nT, Kpmax ≈ 5), the net effect of the outer radiation belt during each disturbance was different, depending on the electron energy. During the August-September CIR, intense substorm activity was recorded (SMLmin ≈ - 2000 nT), as well as significant enhancement of ultra-relativistic electrons.

We exploit coordinated and cross-calibrated particle measurements from the Van Allen Probes, Arase and Galileo 207, 215 satellites, to investigate the relative contribution of radial diffusion and gyro-resonant acceleration, using both electron fluxes and Phase Space Density (PSD) radial profiles, also compared with a 1D Fokker-Planck simulation.

Additionally, we use chorus wave amplitude and radial diffusion coefficient (DLL) estimations, from the SafeSpace DLL database, density measurements from the GFZ-Potsdam database, as well as solar wind and geomagnetic parameters, for a detailed investigation of these events.

This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace project.

How to cite: Nasi, A., Daglis, I. A., Katsavrias, C., Sandberg, I., Li, W., Allison, H., Miyoshi, Y., Imajo, S., Mitani, T., Hori, T., Shprits, Y., Kasahara, S., Yokota, S., Keika, K., Shinohara, I., Matsuoka, A., and Kasahara, Y.: Coordinated observations of relativistic electron enhancements following the arrival of consecutive Corotating Interaction Regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-536, https://doi.org/10.5194/egusphere-egu22-536, 2022.

EGU22-633 | Presentations | ST2.8 | Highlight

Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER) 

Yuri Y. Shprits and the Horizon 2020 PAGER team

This project aims to provide space weather predictions that will be initiated from observations on the Sun and to predict radiation in space and its effects on satellite infrastructure. Real-time predictions and a historical record of the dynamics of the cold plasma density and ring current allow for evaluation of surface charging, and predictions of the relativistic electron fluxes will allow for the evaluation of deep dielectric charging. The project aims to provide a 1-2 day probabilistic forecast of ring current and radiation belt environments, which will allow satellite operators to respond to predictions that present a significant threat. As a backbone of the project, we use the most advanced codes that currently exist and adapt existing codes to perform ensemble simulations and uncertainty quantifications. This project includes a number of innovative tools including data assimilation and uncertainty quantification, new models of near-Earth electromagnetic wave environment, ensemble predictions of solar wind parameters at L 1, and data-driven forecast of the geomangetic Kp index and plasma density. The developed codes may be used in the future for realistic modelling of extreme space weather events. The PAGER consortium is made up of leading academic and industry experts in space weather research, space physics, empirical data modelling, and space environment effects on spacecraft from Europe and the US.

How to cite: Shprits, Y. Y. and the Horizon 2020 PAGER team: Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-633, https://doi.org/10.5194/egusphere-egu22-633, 2022.

Using observations of Van Allen Probes, we present a statistical study of plasmaspheric plumes in the inner magnetosphere. Plasmaspheric plumes tend to occur during the recovery phase of geomagnetic storms. Furthermore, the results imply that the occurrence rate of observed plasmaspheric plume in the inner magnetosphere is larger during stronger geomagnetic activity. This statistical result is different from the observations of the Cluster satellite with much higher L-shells in most orbital period, which suggest that the plasmaspheric plume near the magnetopause tends to be observed during moderate geomagnetic activity (Lee et al., 2016). In the following, the dynamic evolutions of plasmaspheric plumes during a moderate geomagnetic storm in February 2013 and a strong geomagnetic storm in May 2013 are simulated through group test particle simulation. It is obvious that the plasmaspheric particles drift out on open convection paths due to sunward convection during both geomagnetic storms. It seems that the outer plasmaspheric particles exhaust sooner and the plasmasphere shrinks faster during strong geomagnetic storms. As a result, the longitudinal width of the plume is narrower and the plume is limited to lower L-shells during the recovery phase of strong geomagnetic storm. The simulated evolutions may provide a possible interpretation for the occurrence rates: Van Allen Probes tend to observe plumes during stronger geomagnetic storms, and the Cluster satellite with higher L-shells tends to observe plumes during moderate geomagnetic storms. 

How to cite: Li, H.: Statistical Study and Corresponding Evolution of Plasmaspheric Plumes under Different Levels of Geomagnetic Storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1081, https://doi.org/10.5194/egusphere-egu22-1081, 2022.

EGU22-1143 | Presentations | ST2.8

Interhemispheric Conjugacy of Concurrent Onset and Poleward Traveling Geomagnetic Responses for Throat Aurora Observed Under Quiet Solar Wind Conditions 

Hui-Ting Feng, De‐Sheng Han, Xiang‐Cai Chen, Jian‐Jun Liu, and Zhong‐Hua Xu

Throat auroras frequently observed near local noon have been confirmed to correspond to magnetopause indentations, but the generation mechanisms for these indentations and the detailed properties of throat aurora are both not fully understood. Using all‐sky camera and magnetometer observations, we reported some new observational features of throat aurora as follows. (1) Throat auroras can occur under stable solar wind conditions and cause clear geomagnetic responses. (2) These geomagnetic responses can be simultaneously observed at conjugate geomagnetic meridian chains in the Northern and Southern Hemispheres. (3) The initial geomagnetic responses of throat aurora show concurrent onsets that were observed at all stations along the meridians. (4) Immediately after the concurrent onsets, poleward moving signatures and micropositive bays were observed in the X components at higher‐ and lower‐latitude stations, respectively. We argue that these observations provide evidence for throat aurora being generated by low‐latitude magnetopause reconnection. We suggest that the concurrent onsets reflect the instantaneous responses of the reconnection signal arriving at the ionosphere, the followed poleward moving signatures reflect the antisunward dragging of the footprint of newly opened field lines, and the micropositive bays may result from a pair of field‐aligned currents generated during the reconnection. This study may shed new light on the geomagnetic transients observed at cusp latitude near magnetic local noon.

How to cite: Feng, H.-T., Han, D., Chen, X., Liu, J., and Xu, Z.: Interhemispheric Conjugacy of Concurrent Onset and Poleward Traveling Geomagnetic Responses for Throat Aurora Observed Under Quiet Solar Wind Conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1143, https://doi.org/10.5194/egusphere-egu22-1143, 2022.

EGU22-1426 | Presentations | ST2.8

Evidence of wave–wave coupling between frequency harmonic bands of magnetosonic waves 

Zhengyang Zou, Zhonglei Gao, Pingbing Zuo, and Binbin Ni

Previous studies demonstrated that frequency harmonic structures of fast magnetosonic (MS) waves are usually excited by the hot proton instability. Here, we present an unusual event of MS waves with more than six harmonics wavebands (n = 1–6) in which their high harmonic bands are highly phase-coupled with their fundamental waveband. While calculations of the wave growth rates indicate that the local instability of the hot protons can excite the fundamental waveband (n = 1) as well as only a part of wave branches in the second and third wavebands (n = 2, 3), the bicoherence index adopted to analyze the phase coupling between different wavebands provides evidence that the wave–wave coupling between the low-frequency parts of MS waves can contribute to the generation of their higher harmonics (n > 1). Such wave–wave coupling processes have the potential to additionally redistribute the energy of MS waves and then broaden the frequency range of wave–particle interactions, which has important implications for a better understanding of the generation, distribution, and consequence of space plasma waves.

How to cite: Zou, Z., Gao, Z., Zuo, P., and Ni, B.: Evidence of wave–wave coupling between frequency harmonic bands of magnetosonic waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1426, https://doi.org/10.5194/egusphere-egu22-1426, 2022.

EGU22-1546 | Presentations | ST2.8

Parameterized Lifetime of Energetic Electrons due to Interactions with Chorus Waves 

Dedong Wang, Yuri Shprits, and Bernhard Haas

Chorus waves can cause the loss of energetic electrons in the Earth's radiation belts and ring current via pitch-angle diffusion. To quantify the effect of chorus waves on energetic electrons, we calculated the bounce-averaged quasi-linear diffusion coefficients. In this study, using these diffusion coefficients, we parameterize the lifetime of the electrons with an energy range from 1 keV to 2 MeV. In each magnetic local time (MLT), we calculate the lifetime for each energy and L-shell using two different methods. By applying polynomial fits, we parameterize the electron lifetime as a function of L-shell and electron kinetic energy (Ek) in each MLT and geomagnetic activity (Kp). The parameterized electron lifetimes show a strong functional dependence on L-shell and electron energy. During storm time, the lifetimes for higher energy (> 100 keV) electrons range from hours to days in the heart of the radiation belts. In contrast, the lifetimes for electrons with lower energy (< 100 keV) range from minutes to hours. This parameterization of electron lifetime is convenient for inclusion in simulations in the inner magnetosphere. 

How to cite: Wang, D., Shprits, Y., and Haas, B.: Parameterized Lifetime of Energetic Electrons due to Interactions with Chorus Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1546, https://doi.org/10.5194/egusphere-egu22-1546, 2022.

EGU22-1623 | Presentations | ST2.8

Electromagnetic Ion Cyclotron Harmonic Waves Generated via Nonlinear Wave-Wave couplings 

Dan Deng, Zhigang Yuan, Shiyong Huang, Zuxiang Xue, Zheng Huang, and Xiongdong Yu

 In this letter, we report an electromagnetic ion cyclotron (EMIC) harmonic event observed by the Van Allen Probe B, whose generation is demonstrated to result from nonlinear wave-wave resonances through the bicoherence analysis. Hybrid simulation shows that the second to sixth harmonics could be excited in sequence after a pump EMIC wave is initially injected, which is in consistent with the observations of EMIC harmonic. It indicates the important role of the second harmonic in the generation of higher harmonics. Finally, the statistical distribution for the amplitude of EMIC second harmonic waves indicates that the energy transfer rate from the fundamental wave to the second harmonic is mainly less than 2%, which might be too low to result in third and other higher harmonics above the observational level. Our results will give some new insights into the excitation of EMIC harmonic waves in the inner magnetosphere.

How to cite: Deng, D., Yuan, Z., Huang, S., Xue, Z., Huang, Z., and Yu, X.: Electromagnetic Ion Cyclotron Harmonic Waves Generated via Nonlinear Wave-Wave couplings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1623, https://doi.org/10.5194/egusphere-egu22-1623, 2022.

EGU22-1678 | Presentations | ST2.8

Simultaneous Generation of EMIC and MS Waves During the Magnetic Dip in the Inner Magnetosphere 

Zheng Huang, Zhigang Yuan, Xiongdong Yu, Zuxiang Xue, and Zhihai Ouyang

The Van Allen Probe B satellite simultaneously observed electromagnetic ion cyclotron (EMIC) and fast magnetosonic (MS) waves in a magnetic dip on April 29, 2017. During the magnetic dip, we found the coexistence of flux enhancements of ring current protons (∼11.2–∼51.7 keV) and flux reductions of relativistic electrons (∼1 MeV), which are identified as typical signatures of a magnetic dip in the inner magnetosphere. Based on linear theoretical calculations and observational analysis, the observed ring current protons show an anisotropic temperature distribution and partial shell distribution for different energies during the magnetic dip to provide free energies for the generation of EMIC and MS waves, respectively. Our findings indicate that the complex unstable distribution in the velocity phase space of ring current protons during the magnetic dip can trigger the simultaneous generation of EMIC and MS waves in the inner magnetosphere.

How to cite: Huang, Z., Yuan, Z., Yu, X., Xue, Z., and Ouyang, Z.: Simultaneous Generation of EMIC and MS Waves During the Magnetic Dip in the Inner Magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1678, https://doi.org/10.5194/egusphere-egu22-1678, 2022.

EGU22-2106 | Presentations | ST2.8

Hot Plasma Effects on the Pitch-Angle Scattering of Ring Current Protons by EMIC Waves 

Qi Zhu, Xing Cao, Binbin Ni, Xudong Gu, and Xin Ma

Via cyclotron resonant interactions, electromagnetic ion cyclotron (EMIC) waves play an important role in the loss of ring current protons. In this study, by calculating the proton bounce-averaged pitch angle diffusion coefficients using both the cold and hot plasma dispersion relations, we investigate the hot plasma effects on the EMIC wave-induced scattering loss of ring current protons. Our results show that, for H+ band (He+ band) EMIC waves, inclusion of hot protons results in significant decrease of pitch angle diffusion coefficients of ~ 10 - 60 keV (4 - 30 keV) protons, while the scattering efficiency of higher energy protons increases at low pitch angles and decreases at relatively high pitch angles. We also find that the cold plasma approximation seriously underestimates the loss timescales of protons at energies from a few keV to tens of keV but overestimate that of higher energy protons. The differences in proton loss timescales caused by hot plasmas are generally less than a factor of ~ 5 for H+ band but can exceed an order of magnitude for He+ band, showing a strong dependence on ,  and L-shell. This study confirms that hot plasma effects play a crucial role in the EMIC wave driven loss of ring current protons and should be included in future modeling of ring current dynamics.

How to cite: Zhu, Q., Cao, X., Ni, B., Gu, X., and Ma, X.: Hot Plasma Effects on the Pitch-Angle Scattering of Ring Current Protons by EMIC Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2106, https://doi.org/10.5194/egusphere-egu22-2106, 2022.

EGU22-2109 | Presentations | ST2.8

Interchange instability analysis based on magnetosphere-ionosphere coupling theory 

Sina Sadeghzadeh, Jian Yang, and Ameneh Mousavi

A localized flux tube with reduced entropy (PV5/3, where P and V stand for the plasma pressure and flux tube volume, respectively) as compared to its neighbors is defined as a plasma-sheet bubble. Bubbles are susceptible to interchange instability. The interchange instability plays a key role in the transport of plasma from the magnetotail to the near-Earth region. A strong dawn-to-dusk electric field is formed inside the bubble which creates a shear flow. The E×B drift causes the bubble to grow earthward and the magnetic tension force drives it towards the equilibrium location where its total entropy matches the entropy of the surrounding area. According to the Vasyliunas equation, when the angle (α) between ∇V and ∇PV5/3 is either 0 (being parallel) or 180° (being antiparallel), the Birkeland current cannot be flown between the plasma sheet and the ionosphere. In this study, using the linear instability analysis we investigate the excitation and development of interchange modes in the low-beta plasma sheet (β<<1) when 0<α<180°. To this end, a boundary layer (with thickness δ) separating regions of higher and lower entropy is assumed in a small region of the ionosphere. The first-order electric potential (Φ) within this layer is numerically calculated based on time-sequence technique. The complete analytical solution for the temporal variation of Φ clearly shows that the unstable interchange modes with large wavelengths compared to the boundary layer (i.e., λ>>δ) can be generated.

How to cite: Sadeghzadeh, S., Yang, J., and Mousavi, A.: Interchange instability analysis based on magnetosphere-ionosphere coupling theory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2109, https://doi.org/10.5194/egusphere-egu22-2109, 2022.

EGU22-2136 | Presentations | ST2.8 | Highlight

Bounce Resonance Scattering of Radiation Belt Energetic Electrons by Extremely Low-Frequency Chorus Waves 

Deyu Guo, Zheng Xiang, Binbin Ni, Xing Cao, Song Fu, Ruoxian Zhou, Xudong Gu, Juan Yi, Yingjie Guo, and Luhuai Jiao

Bounce-resonant diffusion coefficients of radiation belt energetic electrons induced by extremely low-frequency (ELF) chorus waves are comprehensively evaluated using Van Allen Probes observations on 22 December 2014. ELF chorus waves can efficiently scatter 85° < eq < 89° electrons with bounce resonance pitch angle scattering rates above 10-4/s and energy scattering rates above 10-7/s. By comparing diffusion coefficients due to bounce resonance with those due to cyclotron and Landau resonances, we found that bounce resonance diffusion rates have slight energy dependence for >100 keV electrons while Landau-resonant scattering rates decrease significantly in the MeV energy range. These findings suggest that bounce resonances by ELF chorus waves have potentially significant contributions to the dynamics of energetic electrons and should be considered in the further modeling of Earth’s radiation belts.

How to cite: Guo, D., Xiang, Z., Ni, B., Cao, X., Fu, S., Zhou, R., Gu, X., Yi, J., Guo, Y., and Jiao, L.: Bounce Resonance Scattering of Radiation Belt Energetic Electrons by Extremely Low-Frequency Chorus Waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2136, https://doi.org/10.5194/egusphere-egu22-2136, 2022.

EGU22-3288 | Presentations | ST2.8

Asymmetry of Auroral Kilometric Radiation in the Northern and Southern hemispheres 

Jiawen Tang, Fuliang Xiao, Si Liu, and Sai Zhang

Auroral kilometric radiations (AKR) are existed by suprathermal (1-10keV) electrons, which are accelerated by parallel electric fields and pitch angle scattered by magnetic field gradients. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study of AKR distribution characteristic in the region of λ = 0°−40°and L = 3.0−9.0. Results (totally 32,043 samples) show that southern AKR on the nightside (12,853 samples) are positioned to the east relative to their northern conjugates (13,630 samples), the wave frequencies and amplitudes of AKR in the southern hemisphere are greater than those in the northern hemisphere. Further studies suggest that SYM-H indexes and interplanetary magnetic field (IMF) have different distributions in the northern and southern hemispheres. The probable reason is that different IMF conditions cause asymmetric Field-aligned currents between the northern and southern hemispheres, then yield the asymmetry of AKR and auroras. This study helps to provide more information on the magnetosphere-ionosphere-atmosphere coupling.

How to cite: Tang, J., Xiao, F., Liu, S., and Zhang, S.: Asymmetry of Auroral Kilometric Radiation in the Northern and Southern hemispheres, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3288, https://doi.org/10.5194/egusphere-egu22-3288, 2022.

EGU22-4043 | Presentations | ST2.8

Seasonal Characteristic of Auroral Kilometric Radiation in the Radiation Belts 

Ping Li, Fuliang Xiao, Si Liu, and Sai Zhang

Auroral kilometric radiation (AKR) is one of the strong radio emission phenomenons with kilometer wavelengths, and similar emissions have been detected on other magnetized planets of the solar system. AKR is generated by suprathermal electrons (1-10 keV) injected from the plasma sheet and has been observed at the lower latitude region of the radiation belts from the Van Allen Probes. Here, we analyze the seasonal characteristic of AKR in the region of L = 3-7 and λ = 0− 20using observations from 1 December 2012 to 31 November 2018. Statistical results (4,559 events in total) show that AKR emissions occur most frequently in autumn both in the northern and southern hemispheres. The correlation coefficient between the number of AKR events in each season and the Kp (the geomagnetic activity index) index of these events can reach 0.82. These results suggest that AKR emissions in the lower latitude regions depend on the geomagnetic activity.

How to cite: Li, P., Xiao, F., Liu, S., and Zhang, S.: Seasonal Characteristic of Auroral Kilometric Radiation in the Radiation Belts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4043, https://doi.org/10.5194/egusphere-egu22-4043, 2022.

EGU22-4057 | Presentations | ST2.8 | Highlight

Global magnetic field oscillations on the breathing-mode timescale and their effects on energetic electron precipitation 

Murong Qin, Wen Li, Qianli Ma, Xiaochen Shen, and Xiaochen Shen

In this study, we present simultaneous multi-point observations of whistler-mode chorus waves and global magnetospheric oscillations on a timescale of several to ~10s minutes (breathing mode magnetic field oscillations), associated with concurrent energetic electron precipitation observed through enhanced BARREL X-rays. Similar fluctuations on a timescale of several to ~10s minutes are observed in the X-ray measurements and the compressional component of global oscillations. The spatial scale of global oscillations spans from 4 to 12 h in MLT and from 5 to 11 in L shell. Such global oscillations, which have been suggested to play a potential role in precipitating energetic electrons by either wave scattering or loss cone modulation, show high correlation with the enhancement in X-rays. However, the correlation coefficient between whistler-mode waves and X-rays is low. Observations and model results show that the breathing-mode magnetic field oscillations could play a significant role in modulating the electron precipitation driven by whistler-mode waves even though the whistler-mode wave intensity is not fully modulated by global oscillations.

How to cite: Qin, M., Li, W., Ma, Q., Shen, X., and Shen, X.: Global magnetic field oscillations on the breathing-mode timescale and their effects on energetic electron precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4057, https://doi.org/10.5194/egusphere-egu22-4057, 2022.

EGU22-6518 | Presentations | ST2.8 | Highlight

Advanced Prediction of the Outer Van Allen Belt Dynamics and a Prototype Service: the H2020 SafeSpace project 

Ioannis A. Daglis and the SafeSpace Team

The European SafeSpace project has been implementing a synergistical approach to improve space weather forecasting capabilities from the current lead times of a few hours to 2-4 days. We have combined the solar wind acceleration model MULTI-VP with the heliospheric propagation models Helio1D and EUHFORIA to compute the evolution of the solar wind from the surface of the Sun to the Earth orbit. The forecasted solar wind conditions are then fed into the ONERA Geoffectiveness Neural Networks, to forecast the level of geomagnetic activity with the Kp index as the chosen proxy. The Kp index is used as the input parameter for the IASB plasmasphere model and for the Salammbô radiation belts code. The plasma density is used to estimate VLF wave amplitude and then VLF diffusion coefficients, while the predicted solar wind parameters are used to estimate the ULF diffusion coefficients. Plasmaspheric density and VLF/ULF diffusion coefficients are used by the Salammbô radiation belts code to deliver a detailed flux map of energetic electrons. Finally, particle radiation indicators will also be provided as a prototype space weather service of use to spacecraft operators and space industry. The performance of the prototype service will be evaluated in collaboration with space industry stakeholders. The work leading to this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace (Radiation Belt Environmental Indicators for the Safety of Space Assets) project.

How to cite: Daglis, I. A. and the SafeSpace Team: Advanced Prediction of the Outer Van Allen Belt Dynamics and a Prototype Service: the H2020 SafeSpace project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6518, https://doi.org/10.5194/egusphere-egu22-6518, 2022.

EGU22-6555 | Presentations | ST2.8

Radial diffusion coefficients database in the framework of the SafeSpace project: A Machine Learning model and the application to radiation belt simulations 

Ioannis A. Daglis, Christos Katsavrias, Sigiava Aminalragia-Giamini, Afroditi Nasi, Nourallah Dahmen, Antoine Brunet, Sebastien Bourdarie, and Constantinos Papadimitriou

Radial diffusion has been established as one of the most important mechanisms contributing to the acceleration and loss of relativistic electrons in the outer radiation belt. Over the past few years efforts have been devoted to identify empirical relationships of radial diffusion coefficients (DLL) for radiation belt simulations, yet several studies have suggested that the difference between the various models can be orders of magnitude different at high levels of geomagnetic activity, as the observed DLL have been shown to be highly event-specific. In the framework of the SafeSpace project we have used 12 years (2010 – 2020) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of calculated DLL. In this work we present the statistics on the evolution of DLL during the solar cycle 24 with respect to the various solar wind parameters, geomagnetic indices and universal coupling functions. Furthermore, we show the importance of the use of event-specific DLL through simulations of seed and relativistic electrons with the Salammbo code during the intense storm of St. Patricks 2015 and the high-speed stream driven storm of Christmas 2013. Finally, we present a new approach for a Machine Learning model driven solely by Solar wind parameters.

This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437.

How to cite: Daglis, I. A., Katsavrias, C., Aminalragia-Giamini, S., Nasi, A., Dahmen, N., Brunet, A., Bourdarie, S., and Papadimitriou, C.: Radial diffusion coefficients database in the framework of the SafeSpace project: A Machine Learning model and the application to radiation belt simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6555, https://doi.org/10.5194/egusphere-egu22-6555, 2022.

EGU22-6611 | Presentations | ST2.8 | Highlight

A Neural Network-Based Model of the Relativistic Electrons Fluxes in the Outer Radiation Belt 

Xiangning Chu, Donglai Ma, Jacob Bortnik, W Kent Tobiska, Alfredo Cruz, S. Dave Bouwer, Hong Zhao, Qianli Ma, Kun Zhang, Daniel N. Baker, Xinlin Li, Harlan Spence, and Geoffrey D Reeves

We present a machine-learning-based model of relativistic electron fluxes >1.8 MeV using a neural network approach in the Earth's outer radiation belt. The Outer RadIation belt Electron Neural net model for Relativistic electrons (ORIENT-R) uses only solar wind conditions and geomagnetic indices as input. For the first time, we show that the state of the outer radiation belt can be determined using only solar wind conditions and geomagnetic indices, without any initial and boundary conditions. The most important features for determining outer radiation belt dynamics are found to be AL, solar wind flow speed and density, and SYM-H indices. ORIENT-R reproduces out-of-sample relativistic electron fluxes with a correlation coefficient of 0.95 and an uncertainty factor of ∼2. ORIENT-R reproduces radiation belt dynamics during an out-of-sample geomagnetic storm with good agreement to the observations. In addition, ORIENT-R was run for a completely out-of-sample period between March 2018 and October 2019 when the AL index ended and was replaced with the predicted AL index (lasp.colorado.edu/home/personnel/xinlin.li). It reproduces electron fluxes with a correlation coefficient of 0.92 and an out-of-sample uncertainty factor of ∼3. Furthermore, ORIENT-R captured the trend in the electron fluxes from low-earth-orbit (LEO) SAMPEX, which is a completely out-of-sample data set both temporally and spatially. In sum, the ORIENT-R model can reproduce transport, acceleration, decay, and dropouts of the outer radiation belt anywhere from short timescales (i.e., geomagnetic storms) and very long timescales (i.e., solar cycle) variations.

How to cite: Chu, X., Ma, D., Bortnik, J., Tobiska, W. K., Cruz, A., Bouwer, S. D., Zhao, H., Ma, Q., Zhang, K., Baker, D. N., Li, X., Spence, H., and Reeves, G. D.: A Neural Network-Based Model of the Relativistic Electrons Fluxes in the Outer Radiation Belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6611, https://doi.org/10.5194/egusphere-egu22-6611, 2022.

EGU22-6712 | Presentations | ST2.8

Observations of Higher-band ECH waves and its impact on radiation belt energetic electrons 

Yang Qiwu, Xiao Fuliang, Zhou Qinghua, Liu Si, Gao Zhonglei, He Yihua, Zhang Sai, Deng Zhoukun, and Tang Jiawen

Electron cyclotron harmonic (ECH) waves which mainly observed in the first harmonic band are believed to play a part in scattering diffuse aurora electrons in the Earth's magnetosphere. Here we report two enhanced ECH emission events with nominal wave magnitudes exceeding 1mV/m in higher bands ( up to the 4th harmonic bands) observed from Van Allen Probes mission during geomagnetic disturbance periods in the low density area. Based on actual measurements sampled by Van Allen Probes, we model the electron distribution using a superposition of bi-Maxwellian functions and then numerically evaluate the local growth rates and diffuse coefficients. These differences in frequency distribution for two events can be explained by differences in the loss cone feature of hot electron components. The scattering properties in the first four bands for two events are debated, these results suggest ECH waves in higher band can still cause efficient pitch angle scattering which are similar to ECH waves in the first band. This work broadens our understanding in the formation of diffuse aurora contributed by ECH waves.

How to cite: Qiwu, Y., Fuliang, X., Qinghua, Z., Si, L., Zhonglei, G., Yihua, H., Sai, Z., Zhoukun, D., and Jiawen, T.: Observations of Higher-band ECH waves and its impact on radiation belt energetic electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6712, https://doi.org/10.5194/egusphere-egu22-6712, 2022.

EGU22-6869 | Presentations | ST2.8 | Highlight

Subauroral polarization streams (SAPS): Intrinsic response of geospace during storm time 

Dong Lin, Wenbin Wang, Viacheslav Merkin, Michael Wiltberger, Kareem Sorathia, Kevin Pham, Shanshan Bao, Adam Michael, Xueling Shi, Chaosong Huang, Qian Wu, Yongliang Zhang, Meers Oppenheim, Frank Toffoletto, John Lyon, Jeffrey Garretson, and Brian Anderson

Subauroral polarization streams (SAPS) typically refer to an enhanced westward plasma flow channel in the duskside subauroral ionosphere. SAPS overlap with the low-latitude part of downward Region-2 field-aligned currents (FACs). The relatively low subauroral conductance in this region requires a strong electric field for current closure, which drives the fast sunward plasma flow. Observations have shown dynamic variability of SAPS under various solar wind and interplanetary magnetic field (IMF) conditions, which are related to the variability of FACs and auroral precipitation, as well as their source regions in the ring current and plasmasheet. In this study, we use satellite observations and numerical simulations with the state-of-the-art Multiscale Atmosphere Geospace Environment (MAGE) model to investigate: 1) The role of diffuse electron precipitation in the formation of SAPS; 2) SAPS variability under IMF BY; and 3) Dawnside (as opposed to the more conventional duskside) SAPS as a unique feature of major geomagnetic storms. With data-model comparison, we will demonstrate that SAPS result from the different behaviors of ring current ions and plasma sheet electrons, and the corresponding self-consistent response of the ionosphere-thermosphere system via electrodynamic and particle coupling with the magnetosphere. We conclude that SAPS distribution and variability represent a fundamental feature of the geospace response to solar disturbances during storm time.

How to cite: Lin, D., Wang, W., Merkin, V., Wiltberger, M., Sorathia, K., Pham, K., Bao, S., Michael, A., Shi, X., Huang, C., Wu, Q., Zhang, Y., Oppenheim, M., Toffoletto, F., Lyon, J., Garretson, J., and Anderson, B.: Subauroral polarization streams (SAPS): Intrinsic response of geospace during storm time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6869, https://doi.org/10.5194/egusphere-egu22-6869, 2022.

EGU22-7570 | Presentations | ST2.8 | Highlight

The Effect of Plasmaspheric Plumes on the Loss of Ring Current Electrons 

Bernhard Haas, Yuri Shprits, Michael Wutzig, Hayley Allison, and Dedong Wang

Low-energy ring current electrons of up to 50 keV represent a major threat to spacecrafts within the inner magnetosphere since they are one of the main causes of spacecraft surface charging. Furthermore, they can provide a seed population for relativistic radiation belt electrons during geomagnetic storms. In this work, we report the first results of coupling the Versatile Electron Radiation Belt (VERB) code with a fully MLT resolved physics-based plasmasphere model to investigate the loss mechanisms of low energy electrons. Our four dimensional ring current model used in this study includes radial diffusion, convection, and loss due to whistler-mode chorus and hiss waves. The physics-based model of the plasmasphere includes convection of cold plasma and refilling from the ionosphere.
We simulate two storm events from the Van Allen Probes' era and compare results of cold plasma density and electron flux against measurements from the twin Van Allen Probe satellites. Our plasmasphere model is not only capable of predicting the plasmapause location but also the formation of plasmaspheric plumes, where plume whistler mode waves propagate. Including the plume region, which usually has very restricted spatial coverage, allows us to examine the effect of plume whistler mode waves on the loss of ring current electrons during these two events. These plasma boundaries show significant dynamics during the main and recovery phase of storms and are crucial to correctly predict electron loss.
By using the extracted plasma boundaries to determine the spatial extent of different waves species, we find better agreement of electron flux results with measurements, especially during the main phase of storms. We also report on the first ring current simulation results including the loss introduced by spatially localised whistler-wave scattering in plasmaspheric plumes.

How to cite: Haas, B., Shprits, Y., Wutzig, M., Allison, H., and Wang, D.: The Effect of Plasmaspheric Plumes on the Loss of Ring Current Electrons, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7570, https://doi.org/10.5194/egusphere-egu22-7570, 2022.

EGU22-7578 | Presentations | ST2.8 | Highlight

Assessing the contribution of charge exchange and Coulomb collisions to ring current proton dynamics with the new 4-D Proton Versatile Electron RadiationBelt (proVERB) code 

Julia Himmelsbach, Hayley Allison, Yuri Shprits, Bernhard Haas, Michael Wutzig, and Dedong Wang

Ring current particles affect the terrestrial magnetic field configuration, altering particle trajectories, as well as presenting a surface charging hazard for satellites. These particles can act as a seed population for the electron radiation belts and generate plasma waves. Accurately describing ring current dynamics is crucial to understand the near-Earth plasma environment. Here we report on our first results of the expansion of the Versatile Electron Radiation Belt (VERB) code to model ring current proton dynamics (proVERB). We perform sensitivity studies for the four dimensional grid, considering the grid resolution necessary to resolve proton dynamics. Analysing the banana shaped orbits for ring current protons shows that the azimuthal grid resolution is comparable to the electron grid, while the resolution in the radial grid has to be significantly enhanced. Loss mechanisms of charge exchange and Coulomb collisions, thought to be largely responsible for the decay of the ring current during the recovery phase of a storm, are included in proVERB. We present our first simulation results and compare them to observations from the Van Allen probes HOPE and MagEIS instruments. By retaining and omitting charge exchange and Coulomb collisions in our simulations, we study the role of these loss processes on the ring current evolution during active periods.

How to cite: Himmelsbach, J., Allison, H., Shprits, Y., Haas, B., Wutzig, M., and Wang, D.: Assessing the contribution of charge exchange and Coulomb collisions to ring current proton dynamics with the new 4-D Proton Versatile Electron RadiationBelt (proVERB) code, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7578, https://doi.org/10.5194/egusphere-egu22-7578, 2022.

EGU22-7732 | Presentations | ST2.8

Equatorial electron pitch angle distributions in Earth's outer radiation belt: Storm-time evolution and empirical modeling 

Artem Smirnov, Yuri Shprits, Hayley Allison, Nikita Aseev, Alexander Drozdov, Peter Kollmann, Dedong Wang, and Anthony Saikin

Pitch angle distributions (PADs) of trapped particles play an important role in understanding the processes driving the dynamics of Earth’s radiation belts and ring current. The Van Allen Probes mission has provided electron observations of PADs with an unprecedented coverage in energy (from tens of keV to several MeV) and pitch angles during the mission’s lifespan. We approximate the equatorial electron PADs using the Fourier sine series expansion up to degree 5. The corresponding coefficients can be directly related to the main PAD shapes (pancake, butterfly, flat-top and cap), and the approximated PADs can be easily integrated and converted to omnidirectional flux. Using the entire Van Allen Probes MagEIS data set in 2012-2019, we analyze the response of the equatorial electron PAD shapes to 129 geomagnetic storms with minimum Dst< -50nT. At lower energies (<100 keV), the PADs are stable throughout geomagnetic storms and mainly exhibit a pancake shape. At higher energies, the storm-time PAD evolution depends on the magnetic local time (MLT). At dayside, the pancake distributions become steeper during the main phase and then recover to their original broader form during recovery phase, likely due to the inward radial diffusion. At nightside MLT, the butterfly distributions become more pronounced during the main phase due to the combination of drift-shell splitting and magnetopause shadowing. We present a simple polynomial regression model of PAD shapes driven by the solar wind dynamic pressure. The model allows reconstructions of the full equatorial PADs based on uni-directional measurements at low equatorial pitch angles (applicable to LEO satellite data), as well as from omnidirectional electron flux observations and significantly outperforms the standard sin(alpha) approximation.

How to cite: Smirnov, A., Shprits, Y., Allison, H., Aseev, N., Drozdov, A., Kollmann, P., Wang, D., and Saikin, A.: Equatorial electron pitch angle distributions in Earth's outer radiation belt: Storm-time evolution and empirical modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7732, https://doi.org/10.5194/egusphere-egu22-7732, 2022.

EGU22-8485 | Presentations | ST2.8

The EMIC wave-driven proton precipitation and related effects on the ionosphere 

Xingbin Tian, Yiqun Yu, and Longxing Ma

Protons of tens of keV can be resonantly scattered by EMIC waves excited in the magnetosphere and further precipitate down to the upper atmosphere. In this study, we show a case event that shows direct linkage of the EMIC waves, proton precipitation, and ionospheric ionization using space-borne and ground-based measurements. On Oct 11, 2012, the POES observed that the precipitating flux of the proton much larger than that of the electrons in the night sector around magnetic latitude of 65°. Around the same time and location, ground-based magnetometer detected clear signature of EMIC waves, indicating the causal relation to the proton precipitation. We further simulate the impact of this tens of keV proton precipitation on the upper atmosphere, and found good agreement with PFISR observations of electron density and conductivity. On the other hand, the large ionization rate cannot be accounted for by the electron precipitation at that location. This study shows a clear evidence of the precipitating coupling processes within the magnetosphere-ionosphere system.

How to cite: Tian, X., Yu, Y., and Ma, L.: The EMIC wave-driven proton precipitation and related effects on the ionosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8485, https://doi.org/10.5194/egusphere-egu22-8485, 2022.

EGU22-8799 | Presentations | ST2.8 | Highlight

On the Similarity and Repeatability of Fast Magnetopause Shadowing Loss 

Leonid Olifer, Ian Mann, Louis Ozeke, Seth Claudepierre, Daniel Baker, and Harlan Spence

Properly characterizing fast relativistic electron losses in the terrestrial Van Allen belts remains a significant challenge for accurately simulating their dynamics. In particular, magnetopause shadowing losses can deplete the radiation belt within hours or even minutes but can have long-lasting impacts on the subsequent belt dynamics. By statistically analyzing seven years of data from the entire Van Allen Probes mission in the context of the last closed drift shell, here we show how these losses are much more organized and predictable than previously thought. Once magnetic storm electron dynamics are properly analyzed in terms of the location of the last closed drift shell, not only is the loss shown to be repeatable but its energy-dependent spatio-temporal evolution is also revealed to follow a very similar pattern from storm to storm. Employing an energy-dependent ULF wave radial diffusion model, we further show for the first time how the similar and repeatable fractional loss of the pre-storm electron population in each storm can be reproduced and explained. Empirical characterization of this loss may open a pathway toward improved radiation belt specification and forecast models. This is especially important since underestimates of loss can also create unrealistic sources in models, creating phantom electron radiation and leading to the prediction of an overly harsh radiation environment.

How to cite: Olifer, L., Mann, I., Ozeke, L., Claudepierre, S., Baker, D., and Spence, H.: On the Similarity and Repeatability of Fast Magnetopause Shadowing Loss, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8799, https://doi.org/10.5194/egusphere-egu22-8799, 2022.

EGU22-8840 | Presentations | ST2.8 | Highlight

Relativistic electron scattering by electromagnetic ion cyclotron waves: the hot plasma Model 

Muhammad Fraz Bashir, Anton Artemyev, Xiaojia Zhang, and Vassilis Angelopoulos

Resonant scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms of relativistic electron losses in the inner magnetosphere. For the majority of observed waves, such scattering is well described by the quasi-linear diffusion theory. Low-altitude spacecraft measurements, however, often show that the energy range of precipitating electrons is wider than theoretical predictions based on the cold plasma dispersion of EMIC waves. We develop a hot plasma model based on the observed ion distribution functions and investigate the hot plasma effects on EMIC wave dispersion for a wide frequency range. The results obtained from the analytical hot plasma model agree very well with the numerical solution of the exact dispersion relation of EMIC waves for a wide range of plasma parameters. We also show the implementation of this model for diffusion rate evaluation. Combining near-equatorial spacecraft measurements and wave dispersion model, we show that hot ion effects tend to increase the minimum resonant energy for the frequency range around wave intensity maxima, but can decrease the minimum resonant energy for the higher-frequency part of wave spectra.

This study highlights the importance of hot plasma effects on the relativistic electron scattering and provides a hot plasma model applicable to a wide range of plasma parameters for realistic quasi-linear diffusion rate calculations.

How to cite: Bashir, M. F., Artemyev, A., Zhang, X., and Angelopoulos, V.: Relativistic electron scattering by electromagnetic ion cyclotron waves: the hot plasma Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8840, https://doi.org/10.5194/egusphere-egu22-8840, 2022.

EGU22-8977 | Presentations | ST2.8 | Highlight

A Test of Energetic Particle Precipitation Models Using Simultaneous Incoherent Scatter Radar and Van Allen Probes Observations 

Ennio Sanchez, Qianli Ma, Wei Xu, Robert Marshall, Jacob Bortnik, Pablo Reyes, Roger Varney, and Stephen Kaeppler

Quantification of energetic electron precipitation caused by wave-particle interactions is fundamentally important to understand the cycle of particle energization and loss of the radiation belts. One important way to determine how well the wave-particle interaction models predict losses through pitch-angle scattering into the atmospheric loss cone is the direct comparison between the ionization altitude profiles expected in the atmosphere due to the precipitating fluxes and the ionization profiles actually measured with incoherent scatter radars. This paper reports such a comparison using a forward propagation of loss-cone electron fluxes, calculated with the electron pitch angle diffusion model applied to Van Allen Probes measurements, coupled with the Boulder Electron Radiation to Ionization (BERI) model, which propagates the fluxes into the atmosphere. The density profiles measured with the Poker Flat Incoherent Scatter Radar operating in modes especially designed to optimize measurements in the D-region, show multiple instances of quantitative agreement with predicted density profiles from precipitation of electrons caused by wave-particle interactions in the inner magnetosphere. There are two several-minute long intervals of close prediction-observation approximation in the 65-93 km altitude range. These results indicate that the whistler wave-electron interactions models are realistic and produce precipitation fluxes of electrons with energies between 10 keV to >100 keV that are consistent with observations.

How to cite: Sanchez, E., Ma, Q., Xu, W., Marshall, R., Bortnik, J., Reyes, P., Varney, R., and Kaeppler, S.: A Test of Energetic Particle Precipitation Models Using Simultaneous Incoherent Scatter Radar and Van Allen Probes Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8977, https://doi.org/10.5194/egusphere-egu22-8977, 2022.

Electromagnetic ion cyclotron (EMIC) wave plays an important role in precipitating relativistic electrons. In this study, we analyze an EMIC wave event on 6 November 2015 that extended over 6 hours in local time and the amplitude of this EMIC wave is about 3nT. Solar wind dynamic pressure enhancement excites EMIC waves, and whistler mode chorus waves are observed at the same time. When the EMIC wave occurs, the flux of relativistic electrons with pitch angle around 90° increases and the flux of small-pitch-angle relativistic electrons decreases. We calculate the electron PSD, which proves that EMIC wave leads to relativistic electron precipitation. Our result indicates that the large-amplitude EMIC wave will lead to nonlinear wave-particle interaction, thus leading to relativistic electron precipitation. When the wave amplitude is larger, the nonlinear wave-particle interaction becomes stronger.

How to cite: Yan, Y. and Yue, C.: EMIC Waves Induced by the Enhancement of Solar Wind Dynamic Pressure and Subsequent Relativistic Electron Precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9034, https://doi.org/10.5194/egusphere-egu22-9034, 2022.

EGU22-9039 | Presentations | ST2.8 | Highlight

A comparative study on electron contribution to the ring current during CME and CIR driven geomagnetic storms using RAM-SCB simulations and Arase and ground magnetic data 

Sandeep Kumar, Yoshizumi Miyoshi, Vania Koleva Jordanova, Miles Engel, Kazushi Asamura, Shoichiro Yokota, Satoshi Kasahara, Yoichi Kazama, Shiang-Yu Wang, Takefumi Mitani, Kunihiro Keika, Tomoaki Hori, Chae-Woo Jun, and Iku Shinohara

Geomagnetic storms are the main component of space weather and are driven by coronal mass ejections (CMEs) or corotating interaction regions (CIRs). During the main phase of geomagnetic storms, the ring current enhances and a global decrease in the H component of the geomagnetic field is observed. The storm time distribution of ring current ions and electrons in the inner magnetosphere depend strongly on their transport in evolutions of electric and magnetic fields along with acceleration and loss. Recently, we showed that the electron pressure contributes to the depression of ground magnetic field during the storm time by comparing Ring current Atmosphere interactions Model with Self Consistent magnetic field (RAM-SCB) simulation, Arase in-situ plasma/particle data, and ground-based magnetometer data [Kumar et al., 2021]. In this study, we compare the contribution of electron pressure to the ring current during selected CIR and CME geomagnetic storms using ground observations and the self-consistent inner magnetosphere model: RAM-SCB. The previous results show that the ions are the major contributor (~ 90 %) to the total ring current and the electron contributes ~10 % to the ring current pressure in the post-midnight to dawn sector where electrons flux is higher compared to ions flux. As CIR and CME storms have different origins, we will discuss expected differences in the contribution of electron pressure to the ring current.

How to cite: Kumar, S., Miyoshi, Y., Jordanova, V. K., Engel, M., Asamura, K., Yokota, S., Kasahara, S., Kazama, Y., Wang, S.-Y., Mitani, T., Keika, K., Hori, T., Jun, C.-W., and Shinohara, I.: A comparative study on electron contribution to the ring current during CME and CIR driven geomagnetic storms using RAM-SCB simulations and Arase and ground magnetic data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9039, https://doi.org/10.5194/egusphere-egu22-9039, 2022.

EGU22-9045 | Presentations | ST2.8

Substorm influences on plasma properties distributions in the inner magnetosphere 

Haobo Fu, Chao Yue, Qiu-gang Zong, and Xu-zhi Zhou

The plasma properties in the inner magnetosphere play critical roles in plasma dynamics by changing magnetic field configurations and generating the ring current. Geomagnetic substorms, especially intense substorms can significantly influence inner magnetosphere. This study presents our preliminary statistical results of plasma properties and their substorm dependence at the equatorial plane based on the Van Allen Probe observations. We find that both H+ and O+ pressure increases significantly during substorms, and the pressure ratio of O+ to H+ also increases. The peak of H+ pressure is almost fixed around L=4, while that of O+ moves inward as the substorm intensifies. In addition, substorms can significantly change the ion energy distributions. They will increase the proportion of pressure provided by the lower energy components of H+ (E < ~100keV), especially in lower L-shells. At the same time, they decrease the contribution to the plasma pressure from lower energy components of O+, which shows almost no L-shell dependence. During quiet times, the perpendicular current density distributes roughly symmetrically, with negative value inside (L < ~4.5) and positive value outside. During substorms, the current density enhances and shows asymmetry with higher current density from the pre-dusk to the post-midnight. The parallel current density caused by the pressure gradient also increases with substorms. These field-aligned currents (FACs) enter the ionosphere at dusk and move upward at dawn, as region II FAC.

How to cite: Fu, H., Yue, C., Zong, Q., and Zhou, X.: Substorm influences on plasma properties distributions in the inner magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9045, https://doi.org/10.5194/egusphere-egu22-9045, 2022.

EGU22-9063 | Presentations | ST2.8

Coupling of lightning generated electromagnetic waves to the inner magnetosphere: a case study 

Ondřej Santolík, Ivana Kolmašová, Jolene S. Pickett, and Donald A. Gurnett

Our case study aims at contributing to the discussion on sources of plasmaspheric hiss, which is known for its interactions with the Earth radiation belts. We analyze multi-point measurements of electromagnetic field waves by the Wide Band Data instruments onboard the four Cluster spacecraft in order to find sources of hiss observed close to the geomagnetic equator in the dayside outer plasmasphere. We find hiss to be triggered from whistlers of different spectral properties. Whistlers with the lowest observed dispersion arrive to different spacecraft with time delays indicating their origin in the northern hemisphere. Positions of source lightning discharges are then found using the time coincidences with the Word Wide Lightning Location Network data from three active thunderstorm regions in Europe. We find that subionospheric propagation of lightning atmospherics is necessary to explain the observations. Geographic locations of their ionospheric exit points then determine spectral properties of resulting unducted whistlers and triggered hiss. By this well documented chain of events starting with a lightning discharge in the atmosphere we confirm that magnetospherically reflecting whistlers and hiss triggered from them are among possible sources of plasmaspheric hiss.

How to cite: Santolík, O., Kolmašová, I., Pickett, J. S., and Gurnett, D. A.: Coupling of lightning generated electromagnetic waves to the inner magnetosphere: a case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9063, https://doi.org/10.5194/egusphere-egu22-9063, 2022.

The Earth’s ring current is a complex dynamic system that plays an important role in geomagnetic storms. This ring-shaped current environment changes its structure and intensity on different time scales as a result from the incoming solar wind. Particle populations display very different behaviors, making it extremely hard to develop physics-based forecasting models for the ring current environment.
 
Satellite data provides electron point measurements that can be used to study the different physical processes occurring in the Earth’s magnetospheric ring current. However, in order to fully understand the particle dynamics and injection processes in this region, high temporal and spatial data resolutions are required. We attempt to tackle this issue by using a combination of electron-flux observations from different satellite missions and instruments, in order to improve the global resolution of this dynamic environment.
 

In this work, we present a global reconstruction of the ring current population (energies from 1to a few 100 keV) using global multi-satellite data from Arase, POES, GOES, THEMIS and the Van Allen Probes (RBSP) missions. We achieved this by intercalibrating the satellite data for the year 2017.

Additionally, we present a comparison of the observed electron flux environment with a re-analysis of the ring current region obtained by using  the simplified version of the VERB-4D, which solves the convection equation and reduces the problem to a two-dimensional case by using parameterized lifetimes. For the reanalysis, we assimilate GOES and Van Allen Probes (RBSP A and RBSP B) data with a Stardard Kalman Filter.

How to cite: García Peñaranda, M.: Ring Current Reconstruction via Multi-Satellite Observations and Comparison with VERB-4D Reanalysis Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9530, https://doi.org/10.5194/egusphere-egu22-9530, 2022.

EGU22-9577 | Presentations | ST2.8

Radiation belt model including semi-annual variation and Solar driving (SENTINEL) 

Sigiava Aminalragia-Giamini, Christos Katsavrias, Constantinos Papadimitriou, Ioannis Daglis, Ingmar Sandberg, and Piers Jiggens

The Earth’s outer radiation belt response to geospace disturbances is extremely variable spanning from a few hours to several months. In addition, the numerous physical mechanisms, which control this response, depend on the electron energy, the time-scale and the types of geospace disturbances. As a consequence, the various models that currently exist are either specialized, orbit-specific data-driven models, or sophisticated physics-based ones. In this paper we present a new approach for radiation belt modelling using Machine Learning methods driven solely by solar wind speed and pressure, Solar flux at 10.7 cm and the Russell-McPherron angle. We use Van Allen Probes data to train our model and show that it can successfully reproduce and predict the electron fluxes of the outer radiation belt in a broad energy (0.033–4.062 MeV) and L-shell (2.5–5.9) range and, moreover, it can capture the long-term modulation of the semi-annual variation. We also present validation studies of the model’s performance using data from other missions which are outside the spatio-temporal training regime such as the E>0.8 MeV electron flux measurements from GOES-15/EPEAD at geostationary orbit.

This work has received funding from the European Union’s Horizon 2020 research and innovation programme "SafeSpace" under grant agreement No 870437 and from the European Space Agency under the "European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System" activity under ESA Contract No 4000127282/19/NL/IB/gg.

How to cite: Aminalragia-Giamini, S., Katsavrias, C., Papadimitriou, C., Daglis, I., Sandberg, I., and Jiggens, P.: Radiation belt model including semi-annual variation and Solar driving (SENTINEL), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9577, https://doi.org/10.5194/egusphere-egu22-9577, 2022.

EGU22-9648 | Presentations | ST2.8

Simultaneous Cross-energy Ion Response and Wave Generation after An Interplanetary Shock: A Case Study 

Yuxuan Li, Chao Yue, Qiugang Zong, and Xuzhi Zhou

Interplanetary (IP) shocks in general have strong impact on particles and electromagnetic field. In this study, we have examined the dynamics of cross-energy ions and plasma waves observed by the Van Allen Probe B satellite which was located near the equator at the noon sector after the impact of an IP shock on 27 Feb, 2014. We found that the ULF waves and electromagnetic waves are induced and the differential fluxes of protons with different energies increased or decreased after the IP shock arrival. For low energy ions (10-100eV), the perpendicular flux increased intensively due to ExB drift and betatron acceleration. These adiabatic processes also accounted for the special behavior of 10~200 keV ions, which are due to the positive gradient in phase space density before the IP shock arrival. In addition, the short-lived ultra-low frequency waves triggered by the IP shock interacted with the ~100 keV protons and resulting in the stripes in pitch angle distribution. Meanwhile, the anisotropic ions of ~50-300 keV generate EMIC wave at higher L shell after the shock arrival. This study reveals that an IP shock event can cause comprehensive responses of different energy ions and drive several plasma waves at the same time.

How to cite: Li, Y., Yue, C., Zong, Q., and Zhou, X.: Simultaneous Cross-energy Ion Response and Wave Generation after An Interplanetary Shock: A Case Study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9648, https://doi.org/10.5194/egusphere-egu22-9648, 2022.

EGU22-11179 | Presentations | ST2.8

Whistler and electron cyclotron harmonic waves at the near-Earth dayside plasma sheet: statistics of modulation by ultra-low frequency waves 

Abdul Waheed, Muhammad Fraz Bashir, Anton Artemyev, and Xiaojia Zhang

Magnetopause perturbations by solar wind transients drive a wide variety of ultra-low-frequency (ULF) waves in the Earth’s magnetosphere. Compressional ULF waves modulate thermal and energetic electron fluxes, changing their flux anisotropy. Such modulation may move electron distributions beyond the threshold of instabilities and drive the generation of electron cyclotron harmonic (ECH) and whistler-mode waves. Given the importance of ECH and whistler-mode waves for electron scattering into the atmosphere, we statistically investigate the main characteristics of ULF-modulated ECH and whistler-mode waves. We find two main types of events: with the correlation of whistler-mode and ECH waves and with their anti-correlation. We present the spatial distribution of these two types of events and examine correlations of background plasma/magnetic field characteristics with properties of whistler and ECH waves modulated by ULF waves.

How to cite: Waheed, A., Bashir, M. F., Artemyev, A., and Zhang, X.: Whistler and electron cyclotron harmonic waves at the near-Earth dayside plasma sheet: statistics of modulation by ultra-low frequency waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11179, https://doi.org/10.5194/egusphere-egu22-11179, 2022.

EGU22-11316 | Presentations | ST2.8

Properties of quasi-periodical emission of electromagnetic ion cyclotron waves 

Muhammad Shahid, M. Fraz Bashir, Anton Artemyev, Xiaojia Zhang, Vassilis Angelopoulos, and Ghulam Murtaza

Energetic electron scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms of electrons losses in the inner magnetosphere. Such resonant scattering has been traditionally considered as a controlling process for the dynamics of relativistic electron fluxes in the Earth’s radiation belts. EMIC wave generation is mainly associated with the ring current ion population injected from the plasma sheet. These ions are drifting westward and generate the most intense EMIC waves on the dusk flank. In this work, we consider an alternative mechanism of EMIC wave generation due to local plasma compression by strong ultra-low-frequency (ULF) waves that modulate a quasi-periodical ion anisotropy responsible for EMIC excitation. Using THEMIS spacecraft observations of simultaneous EMIC waves and compressional ULF waves, we investigate the statistical properties of such quasi-periodic EMIC emission. We show spatial distributions of ULF-modulated EMIC waves, statistics of their amplitudes and typical frequencies. We also discuss the associated measurements of ULF-modulated hot ion populations responsible for EMIC wave generation.

How to cite: Shahid, M., Bashir, M. F., Artemyev, A., Zhang, X., Angelopoulos, V., and Murtaza, G.: Properties of quasi-periodical emission of electromagnetic ion cyclotron waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11316, https://doi.org/10.5194/egusphere-egu22-11316, 2022.

EGU22-11579 | Presentations | ST2.8

Plasmapause Surface Waves Triggered by Substorms 

Yixin Hao, Qiugang Zong, Chao Yue, Xuzhi Zhou, Hui Zhang, Zuyin Pu, and Yuri Shprits

In this study, we present in-situ measurement by Van Allen Probes showing that surface wave could oscillate the plasmapause and modulate hiss and electron cyclotron harmonic (ECH) waves. Plasmapause sur-face wave (PSW) in Ps6 band was observed during an intense substorm on 16 July 2017, accompanied with quasi-periodic emissions of hiss (positively correlated to plasma density) and ECH waves (anticorrelated to the density). Phase relation between magnetic field and velocity perturbations indicatesthat the PSW was an eigenmode between southern and northern ionosphere. Measurements from ground-based magnetometers suggest that such PSW propagates sunward at dusk flank and were excited around the expansion phase of an intense substorm. Addiational cases of PSWs are also presented to demonstrate that such waves are commonly observed near plasmapause and are likely to be related to substorm activities.

How to cite: Hao, Y., Zong, Q., Yue, C., Zhou, X., Zhang, H., Pu, Z., and Shprits, Y.: Plasmapause Surface Waves Triggered by Substorms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11579, https://doi.org/10.5194/egusphere-egu22-11579, 2022.

EGU22-11822 | Presentations | ST2.8 | Highlight

Energetic electron precipitations by chorus waves and its impact on the middleatmosphere 

Yoshizumi Miyoshi, Shinji Saito, Keisuke Hosokawa, Kazushi Asamura, Shinichiro Oyama, Takefumi Mitani, Takeshi Sakanoi, Antti Kero, Esa Turunen, and Pekka Verronen

Whistler chorus waves cause energetic electron precipitations into the Earth’s atmosphere, and signatures of precipitations are observed as diffuse,
pulsating aurora, and microbursts of energetic electrons. In this talk, we present our model that propagating chorus waves cause wide energy electron precipitations and relativistic electron microbursts are a high-energy tail of the pulsating aurora electrons. The chorus waves can resonate with tens keV electrons near the magnetic equator, which causes the pulsating aurora emissions, while the chorus waves can resonate with sub-relativistic/relativistic electrons at the off-equator, which cause the microbursts of energetic electrons. Moreover, we discuss that relativistic electrons cause a significant ozone destruction at the middle atmosphere by conjugate observations of Arase, ground-based observations, SIC ion chemistry simulation.

How to cite: Miyoshi, Y., Saito, S., Hosokawa, K., Asamura, K., Oyama, S., Mitani, T., Sakanoi, T., Kero, A., Turunen, E., and Verronen, P.: Energetic electron precipitations by chorus waves and its impact on the middleatmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11822, https://doi.org/10.5194/egusphere-egu22-11822, 2022.

It is demonstrated that the application of a height-integrated conductivity (HIC) boundary condition in theories of the ionospheric feedback instability is valid only for very thin (few km) conducting layers. In the presence of global convection, the strong variation of the ion mobility with altitude produces strongly sheared transverse ion flows within the E-layer.  These flows are not accounted for when the HIC boundary condition is applied, and when accounted for they cause a drastic reduction in growth rates of the IFI even for very large convection electric fields on the order of a few hundred mV/m. Thie reduction in IFI growth rates is verified through linear eigenmode analysis of the IFI similar to Watanabe & Maeyama (JGR, 45, 2018), except that (a) parallel electric fields in the ionosphere are accounted for, and (b) collision frequency profiles are determined from the IRI and MSIS models (Sydorenko and Rankin, GRL, 44, 2017).

The IFI in field line resonances (FLRs) and the ionospheric resonator (IAR) is studied for a collisional slab ionosphere of thickness 300 km. Constant density is assumed for FLRs, with the slab adjoining a collisionless plasma embedded in a constant magnetic field. Symmetry boundary conditions are applied at the equatorial magnetosphere. In the IAR study, the density varies with altitude and reflecting boundary conditions are used. Instability growth rates are computed numerically and compared with results for slabs of varying thickness (2 km to 300 km) and identical height-integrated conductivity. Growth rates for the most unstable mode are significantly reduced compared to the HIC case for layers as thin as 2 km, even in the long parallel wavelength limit.

The parallel electric field obtained from Faraday’s Law is strongly stabilizing for short transverse wavelength perturbations, especially for higher harmonics. A new unstable mode is found that does not require reflection of  waves within the IAR. It satisfies the resonance condition ω=ky<Vd> where ky is the transverse wavelength and <Vd> is the average ion drift velocity within the sptaially structured E-layer. The physical implication of this newly identified ionospheric instability is considered in the context of discrete auroral arcs and field line resonances.

How to cite: Rankin, R., Sydorenko, D., and Shen, W.: A new interpretation of the ionospheric feedback instability applied to feld line resonances and the ionospheric Alfven resonator, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13019, https://doi.org/10.5194/egusphere-egu22-13019, 2022.

During geomagnetic storms rapid magnetic variations cause large, sharp enhancements of the magnetic and geoelectric field at mid-latitudes. These present a potential hazard to grounded technology such as high voltage transformers, pipelines and railway systems. Spatio-temporal quantification can provide insight into the magnitude and configuration of their potential hazard. We perform a wavelet decomposition on both European ground-based magnetometer measurements and modelled Geomagnetically Induced Currents (GICs) from the high voltage grid of Great Britain (GB).  A wavelet decomposition localizes the signal in the time-frequency domain, and we show that in both magnetometer observations, and modelled GIC response, the Haar wavelet extracts the signal power and waveform at the signal fastest rate-of-change.

We then use Haar wavelet cross-correlation of the GIC in the grounded nodes to build a time-varying network of GIC coherent response around the GB grid during intense geomagnetic storms [1]  including the 2003 Halloween storm. We find a highly intermittent (few 10s of minutes duration) long-range coherent response that can span the entire physical grid at most intense times. The spatial pattern of coherent response seen in the GIC flow network does not simply follow that of the amplitude of the rate of change of B field that is estimated via the Haar wavelet. Coherent response is excited across spatially extended clusters comprised of a subset of nodes that are highly connected to each other, with a tendency for east-west linkages following that of the physical grid, simultaneous with  the overhead presence of the auroral electrojet and the inducing component of the magnetic field. This can quantify the spatial and temporal location of increased hazard in specific regions during large storms by including effects of both the geophysical and engineering configuration of the high voltage grid.

[1] L. Orr, S. C. Chapman, C. Beggan, Wavelet and network analysis of magnetic field variation and geomagnetically induced currents during large storms, Space Weather (2021) doi: 10.1029/2021SW002772

 

How to cite: Chapman, S., Orr, L., and Beggan, C.: Wavelet cross-correlation dynamical network of the coherent GIC response to intense geomagnetic storms in the high voltage grid of Great Britain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1769, https://doi.org/10.5194/egusphere-egu22-1769, 2022.

EGU22-3006 | Presentations | EMRP2.13 | Highlight

Modelling space weather impacts on UK railway signalling systems 

Cameron Patterson and Jim Wild

Track circuits are widely used signalling systems that use electrical currents to detect the presence or absence of a train in predefined sections of a railway network, as such, they are susceptible to interference from geomagnetically induced currents.

This work aims to determine the impact space weather has on realistic track circuits across geologically different regions of the UK under various storm conditions by using the Spherical Elementary Current System method of geomagnetic field interpolation, a ground conductivity model of the UK, a 1D-layered model to provide estimations of the geoelectric field and track circuit modelling techniques developed by Boteler (2021).

Early results of a modelled section of the West Coast Main Line in North West England will be presented.

How to cite: Patterson, C. and Wild, J.: Modelling space weather impacts on UK railway signalling systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3006, https://doi.org/10.5194/egusphere-egu22-3006, 2022.

EGU22-3218 | Presentations | EMRP2.13

Assessing the impact of weak and moderate geomagnetic storms on UK power station transformers 

James Wild, Zoe Lewis, and Matthew Allcock

It is well documented that space weather can impact electricity infrastructure, and several incidents have been observed in recent decades and directly linked to large geomagnetic storms (e.g. the Hydro Quebec incident in 1989). However, less is understood aboutthe impact of lower-level geomagnetically induced currents (GICs) on the health of transformers in the long term. In this study, the long term impact of geomagnetic activity  on 13 power station transformers in the UK is investigated. Dissolved gas measurements from 2010–2015 were used to look for evidence of a link between degradation of the transformer and heightened levels of the global SYM-H index and dB as measured at Eskdalemuir magnetometer station in southern Scotland. First, case studies of the most significant storms in this time period were examined using dissolved gas analysis (DGA) methods, specifically the Low Energy Degradation Triangle (LEDT). These case studies were then augmented with a statistical survey, including Superposed Epoch Analysis (SEA) of multiple storm events. No evidence of a systematic space weather impact can be found during this time period, likely owing to the relatively quiet nature of the Sun during this epoch and the modernity of the transformers studied.

How to cite: Wild, J., Lewis, Z., and Allcock, M.: Assessing the impact of weak and moderate geomagnetic storms on UK power station transformers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3218, https://doi.org/10.5194/egusphere-egu22-3218, 2022.

In this research the analysis of shutdowns in long power line SS147AL169A in Almaty power grid for 2016-2021 was done. For the analyzed period, there were 16 emergency shutdowns. 6 of them occurred due to evident external causes. Other 10 cases analyzed for the possibility of a connection with the geomagnetic environment. Initial analysis showed a possible connection between the automatic operation of relay protection and the presence of geomagnetically induced currents. This is due to the geomagnetic situation, which was before the moment the relay was triggered. At the moment, more detailed calculations are being carried out.

This research has been/was/is funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP00000000).

How to cite: Nurgaliyeva, K.: Analysis of correlations between geomagnetic storms and emergency shutdowns in the part of Almaty power grid for 2016-2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3317, https://doi.org/10.5194/egusphere-egu22-3317, 2022.

EGU22-6243 | Presentations | EMRP2.13 | Highlight

Estimating the Geoelectric Field, Transmission Line Voltages, and GICs During a Geomagnetic Storm in Alberta, Canada 

Darcy Cordell, Martyn Unsworth, Benjamin Lee, Cedar Hanneson, David Milling, Hannah Parry, and Ian Mann

Estimating the effect of geomagnetic disturbances on infrastructure is an important problem since they can induce damaging currents in electric power transmission lines. In this study, an array of magnetotelluric (MT) impedance measurements in Alberta and southeastern British Columbia are used to estimate the geoelectric field resulting from a magnetic storm on September 8, 2017. The resulting geoelectric field is compared to the geoelectric field calculated using the more common method involving a piecewise-continuous 1-D conductivity model. The 1-D model assumes horizontal layers, which result in orthogonal induced electric fields while the empirical MT impedance data account for fully 3-D electromagnetic induction. The geoelectric field derived from empirical MT impedance data demonstrates a preferential polarization in southern Alberta, and the geoelectric field magnitude is largest in northeastern Alberta where resistive Canadian Shield outcrops. The induced voltage in the Alberta transmission network is estimated to be ~120 V larger in northeastern Alberta when using the empirical MT impedances compared to the piecewise-continuous 1-D model. Transmission lines oriented northwest-southeast in southern Alberta have voltages which are 10-20% larger when using the MT impedances due to the polarized geoelectric field. As shown with forward modelling tests, the polarization is due to the Southern Alberta British Columbia conductor in the lower crust (20-30 km depth) that is associated with a Proterozoic tectonic suture zone. This forms an important link between ancient tectonic processes and modern-day geoelectric hazards that cannot be modelled with a 1-D analysis. The geoelectric field model and resulting line voltage is compared to differential magnetometer GIC measurements on one transmission line near the Heartland transformer in northeastern Alberta.

How to cite: Cordell, D., Unsworth, M., Lee, B., Hanneson, C., Milling, D., Parry, H., and Mann, I.: Estimating the Geoelectric Field, Transmission Line Voltages, and GICs During a Geomagnetic Storm in Alberta, Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6243, https://doi.org/10.5194/egusphere-egu22-6243, 2022.

EGU22-6442 | Presentations | EMRP2.13

Investigating the levels of Geomagnetically Induced Currents in the Mediterranean region during the most intense geomagnetic storms of solar cycle 24 

Adamantia Zoe Boutsi, Georgios Balasis, Ioannis A. Daglis, Kanaris Tsinganos, and Omiros Giannakis

Geomagnetically Induced Currents (GIC) constitute an integral part of space weather research and are a subject of ever-growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. Here, we exploit data from the HellENIc GeoMagnetic Array (ENIGMA), which is deployed in Greece, complemented by magnetic observatories in the Mediterranean region (Italy, France, Spain, Algeria and Turkey), to calculate values of the GIC index, i.e., a proxy of the geoelectric field calculated entirely from geomagnetic field variations. We perform our analysis for the most intense magnetic storms (Dst < -150 nT) of solar cycle 24. Our results show that GIC indices do not exceed low activity levels despite the increase in their values, at all magnetic observatories / stations under study during the selected storm events.

How to cite: Boutsi, A. Z., Balasis, G., Daglis, I. A., Tsinganos, K., and Giannakis, O.: Investigating the levels of Geomagnetically Induced Currents in the Mediterranean region during the most intense geomagnetic storms of solar cycle 24, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6442, https://doi.org/10.5194/egusphere-egu22-6442, 2022.

EGU22-9495 | Presentations | EMRP2.13

Combining geoelectric field modelling and differential magnetometer data to validate GIC modelling in the UK High voltage power transmission grid 

Juliane Huebert, Ciaran Beggan, Gemma Richardson, Natalia Gomez Perez, and Alan Thomson

Geomagnetically induced currents (GICs) have been identified as a hazard to the UK power grid and the security of electricity supply during severe geomagnetic storms. In order to monitor, model and forecast GICs, sophisticated models of the ground electric field and the network topology are required. We present a detailed analysis of differential magnetometer (DMM) and magnetotelluric (MT) data in the UK that allow the verification and validation of our network model for the UK power transmission grid. Combining the observation of line GICs measured with DMM in the past three years and the MT impedance tensor estimated at several locations in the UK shows an excellent fit of prediction and observation of GICs when using realistic modelled ground electric fields. This validates our whole network model allowing us to use it with confidence for real time and forecasting as well as extreme event analysis.

How to cite: Huebert, J., Beggan, C., Richardson, G., Gomez Perez, N., and Thomson, A.: Combining geoelectric field modelling and differential magnetometer data to validate GIC modelling in the UK High voltage power transmission grid, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9495, https://doi.org/10.5194/egusphere-egu22-9495, 2022.

EGU22-1276 | Presentations | PS4.6

Observation of a Total Eclipse of the Moon at 183 GHz 

Martin Burgdorf, Niutao Liu, Stefan A. Buehler, and Yaqiu Jin

The observation of an eclipse of the Moon at millimetre wavelengths makes it possible to investigate the electrical and thermal properties of the lunar surface to a depth of 10 cm without being influenced by deeper layers. Such measurements are usually carried out with radio telescopes on Earth. When microwave instruments on weather satellites use observations of deep space for their calibration, however, the whole lunar disk appears sometimes in their field of view as well. We identified such an event with the Advanced Microwave Sounding Unit-B on NOAA-15 that coincided with a total lunar eclipse. From this unique vantage point in a polar orbit around the Earth we could measure, once per orbit, the lunar radiance at 183 GHz - a frequency, where the atmosphere is not transparent.

We found a maximum temperature drop during the eclipse of 47±9 K at 183 GHz, corresponding to 16.6±2.1% of the flux density of full Moon, and of 17.3±6 K, corresponding to 6.4±2.1% of the flux density of full Moon, for the window channel at 89 GHz. The evolution in time of the global flux agrees well with the predictions from a new radiative transfer model simulating the global brightness temperatures. Our measurements are consistent with results reported in the past, except for two, which we consider erroneous. The temperature changes are similar everywhere on the lunar disc. The good agreement between the observations from a weather satellite and theoretical predictions demonstrates that the Moon is very useful as flux reference and for checking the reliability of climate data records from Earth observation.

How to cite: Burgdorf, M., Liu, N., Buehler, S. A., and Jin, Y.: Observation of a Total Eclipse of the Moon at 183 GHz, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1276, https://doi.org/10.5194/egusphere-egu22-1276, 2022.

EGU22-2214 | Presentations | PS4.6

Large impact cratering during lunar magma ocean solidification 

Katarina Miljkovic, Mark A. Wieczorek, Matthieu Laneuville, Alexander Nemchin, Phil A. Bland, and Maria T. Zuber

The lunar cratering record is used to constrain the bombardment history of both the Earth and the Moon. However, it is suggested from different perspectives, including impact crater dating, asteroid dynamics, lunar samples, impact basin-forming simulations, and lunar evolution modelling, that the Moon could be missing evidence of its earliest cratering record. Here we report that impact basins formed during the lunar magma ocean solidification should have produced different crater morphologies in comparison to later epochs. A low viscosity layer, mimicking a melt layer, between the crust and mantle could cause the entire impact basin size range to be susceptible to immediate and extreme crustal relaxation forming almost unidentifiable topographic and crustal thickness signatures. Lunar basins formed while the lunar magma ocean was still solidifying may escape detection, which is agreeing with studies that suggest a higher impact flux than previously thought in the earliest epoch of Earth-Moon evolution.

How to cite: Miljkovic, K., Wieczorek, M. A., Laneuville, M., Nemchin, A., Bland, P. A., and Zuber, M. T.: Large impact cratering during lunar magma ocean solidification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2214, https://doi.org/10.5194/egusphere-egu22-2214, 2022.

EGU22-2815 | Presentations | PS4.6

Estimation of Lunar Ephemeris from Lunar Laser Ranging 

Vishwa Vijay Singh, Liliane Biskupek, Juergen Mueller, and Mingyue Zhang

Lunar Laser Ranging (LLR) has been measuring the distance between the Earth and the Moon since 1969, where the measurements are provided by the observatories as Normal Points (NPs). The Institute of Geodesy (IfE) LLR model has (as of April 2021) 28093 NPs. Using the LLR observation equation, the LLR residuals (difference of observed and calculated values of the light travel time) are obtained for each NP. The LLR analysis procedure is an iteration of the calculation of ephemeris of the solar system followed by the calculation of residuals and the estimation of parameters using a Least-Squares Adjustment (LSA). The initial orbit of the Moon (Euler angles and angular velocity of the lunar mantle, Euler angles of the lunar core, and the position and the velocity of the selenocenter), amongst many other parameters, is estimated from the LSA. In our previous standard calculation, the initial orbit of the Moon was estimated for June 28, 1969 and ephemeris was calculated from this time until June 2022. In this study, we estimate the initial orbit of the Moon for Jan 1, 2000 to be able to benefit from the higher accuracy of the NPs over the timespan of LLR. The ephemeris is then calculated in forward and backward directions (until June 2022 and June 1969). When comparing the uncertainty obtained from a LSA of this study with the previous standard calculation, preliminary results show an improvement of over 50% in the initial position and the initial velocity of the Moon, a deterioration of about 20% in the Euler angles of the mantle and the core, and an improvement of over 15% in the angular velocity of the mantle. The changed analysis procedure will allow to compute a more accurate ephemeris for the upcoming years benefitting future lunar science. Recent results will be presented and major changes would be discussed.

Acknowledgement. This research was funded by Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy EXC 2123 QuantumFrontiers-390837967.

How to cite: Singh, V. V., Biskupek, L., Mueller, J., and Zhang, M.: Estimation of Lunar Ephemeris from Lunar Laser Ranging, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2815, https://doi.org/10.5194/egusphere-egu22-2815, 2022.

EGU22-5452 | Presentations | PS4.6

Investigating Potential Safe Landing Sites for ESA/ROSCOSMOS' Luna 27 Mission 

Sarah Boazman, David Heather, Elliot Sefton-Nash, Csilla Orgel, Berengere Houdou, Xavier Lefort, and The Lunar Lander Team

ESA and ROSCOSMOS’ Luna 27 mission will explore the south polar region of the Moon and will sample the lunar surface. To ensure the best samples are collected, which yield the greatest scientific return eight potential landing sites are being investigated using remote sensing methods. We have studied the safety of the eight potential landing sites by creating slope maps using the LOLA (30m/px) digital elevation model and classified slopes into safe areas (slopes <10°) and unsafe areas (slopes >10°). Additionally, we created slope maps classified in 2° intervals from 0-14° and greater than 14°, to further investigate which areas have the lowest slopes and therefore potentially the safest landing sites.

      We found that each of the eight landing sites contain areas that are safe for landing (slopes <10°) and sites 1, 2, 4, 6 and 8 contain large areas (>500 km2) that are classified as safe for landing. Site 3 has large craters with steep crater walls, which may present a hazard to landing. At site 5 there is a large crater (~20 km diameter) to the bottom right of the site, which has a steep crater walls and rim, which creates a topographic ridge in the south east of the landing site and should be avoided as a landing site. Site 7 also has a steep topographic ridge which again should be avoided as a landing area. In comparison site 8 contains a large area with shallow slopes in the center with slopes of 0-2°, which would be an ideal landing site. Site 1 covers a large crater (~40 km diameter), and the center of the crater floor has shallow slopes with less than 4°. Site 2 similarly has a large crater floor with slopes less than 4°. Both the crater floors of site 1 and site 2 could be a safe landing site.

     This initial investigation into the potential landing sites has identified areas which could be safe for landing Luna 27. Future work will use multiple datasets to explore the scientific potential of the landing sites including investigating the surface roughness, identifying craters and boulders, which could present a hazard to the lander, using thermal maps to measure the thermal stability, and exploring the illumination conditions and Earth visibility at each of the landing sites.

How to cite: Boazman, S., Heather, D., Sefton-Nash, E., Orgel, C., Houdou, B., Lefort, X., and Lunar Lander Team, T.: Investigating Potential Safe Landing Sites for ESA/ROSCOSMOS' Luna 27 Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5452, https://doi.org/10.5194/egusphere-egu22-5452, 2022.

EGU22-7634 | Presentations | PS4.6

GPR Reverse-Time Migration for Layered Media: A Case Study at the Chang’E-4 Landing Site 

Iraklis Giannakis, Javier Martin-Torres, Maria-Paz Zorzano, Craig Warren, and Antonis Giannopoulos

   Chang’E-4 was the first mission to land a human object on the far side of the Moon. The landing site was at the Von Kármán (VK) crater at the South-Pole Aitken (SPA) basin, one of biggest craters in the solar system. SPA is believed that was created by a huge impact that penetrated the lunar crust and uplifted mantle materials. Evidence of these materials are expected to be found by the Yutu-2, the rover of the mission that is still active to this day, having covered more than 1km on the lunar’s surface. Yutu-2 is equipped with a stereo camera, visible/near-infrared imaging spectrometer, alpha particle x-ray spectrometer and Ground-Penetrating Radar (GPR). In-situ GPR is a powerful geophysical methodology with a uniquely wide range of applications to civil engineering, archaeology and geophysics. In planetary science, it was first used in 2013 during the Chang’E-3 mission. Since then, GPR has become a very popular instrument in planetary missions, and has been included in the scientific payload of Chang’E-4, E-5, Tianwen-1, and Perseverance. It is also planned to be used in the future missions Chang’E-7 (2024) and ExoMars (September 2022).

   Yutu-2 rover is equipped with three different GPR systems. One low frequency and two high frequency antennas. Unfortunately, due to interferences between the antenna and the metallic parts of the rover, the low frequency data have very low signal to clutter ratio making the interpretation of these data unreliable. On the other hand, the signal from the high frequency antennas is very clear, probably due the lack of ilmenite in the area, which results to low electromagnetic losses (compared to the Chang’E-3 landing site). This resulted to good quality radagrams that provided new insights into the structure and composition of the top ejecta layers at the VK crater.

    In the current paper, we introduce a complete processing scheme, tuned for high frequency lunar penetrating radar.  The first step of the proposed framework is an advanced hyperbola fitting (AHF) capable of inferring previously unseen layers due to their smooth boundaries. Subsequently, the reconstructed layered structure is used in a Reverse-Time Migration (RTM) coupled with Finite-Differences Time-Domain (FDTD) method. Via this approach, the radagram is focused subject to a 1D model, avoiding homogeneity constrains that often deviate from reality. Lastly, an un-supervised thresholding is applied to cluster the migrated image into two categories i.e. A) the background host medium and B) rocks/boulders. The suggested scheme is applied to the high frequency data collected by the Yutu-2 rover at the first 100 meters of the mission. A layered structure is inferred at the top 12 meters, similar to the results presented in [1]. Moreover, using the proposed RTM, an abundance of rocks/boulders was revealed. The distribution of the rocks/boulders correlates with the permittivity/density profile, indicating the reliability of the proposed scheme.   

References

[1] Giannakis, I., Zhou, F., Warren, C., & Giannopoulos, A. (2021). Inferring the shallow layered structure at the Chang’E-4 landing site: A novel interpretation approach using lunar penetrating radar. Geophysical Research Letters, 48, e2021GL092866

How to cite: Giannakis, I., Martin-Torres, J., Zorzano, M.-P., Warren, C., and Giannopoulos, A.: GPR Reverse-Time Migration for Layered Media: A Case Study at the Chang’E-4 Landing Site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7634, https://doi.org/10.5194/egusphere-egu22-7634, 2022.

Targeting the deployment of sustainable human and robotic exploration on the Moon by the end of this decade, there is a pressing need for better understanding the lunar water cycle and the availability of water for ISRU. The O-H isotope signatures in lunar water are key for determining the water origin in the Earth-Moon system and the mechanisms controlling water distribution and redistribution on the Moon. This has profound implications for understanding the Earth-Moon system’s history and the stability and renewability of water deposits.
Lunar volatiles are involved in a largely unconstrained and complex system of input, transport, trapping, recycling, and loss. The water origin on the Earth-Moon system remains poorly understood. The δD signatures from Apollo samples and meteorites suggest various contributing reservoirs of different origins for lunar water, and/or secondary processes [1], [2]. The different origins include: i) Magmatic (primordial) [3]; ii) asteroidal/cometary impacts [4], [5]; iii) solar wind H+ [1]; iv) mixed origin (solar wind H+/inclusion within meteorite impact glasses or volcanic glasses [6]).
The Roscosmos/ESA Luna 27 mission [7] is one of several international lunar polar missions for in-situ analyses of lunar surface, targeting pressing scientific and industrial knowledge gaps. To interpret the results derived from those polar missions it is critical to understand the extent and nature of any potential water ice loss and related isotope fractionation during the sampling chain.
Experimental studies on isotope fractionation during ice sublimation in nonequilibrium conditions are scarce. These studies concluded on different trends: i) no relevant isotope fractionation up to 40% ice mass loss [8], ii) relevant Rayleigh-like fractionation trend [9]. There is no kinetic isotope fractionation model (theoretical or experimental) for ice sublimation in low pressure systems at cryogenic temperatures, which considers the expected physical processes. Thus, the calculation of water ice isotope signatures remains highly uncertain, hindering the assessment of potential lunar water resources and the interpretation of scientific planetary data.
Here we present a theoretical isotope fractionation model derived from concepts developed by Criss (1999) [10] and adapted to the physical processes expected under lunar conditions, which will contribute to i) more robust interpretations of water ice behaviour in lunar environment and/or extra-terrestrial and/or extreme terrestrial environments; ii) mission operational planning, data processing, extraction/processing techniques; iii) exploration/exploitation roadmap, space mining business plan, natural resources management. [1] B. M. Jones et al., 2018. Geophys. Res. Lett., 45(20), 10,959-10,967; [2] F. M. McCubbin and J. J. Barnes, 2019. Earth Planet. Sci. Lett., 526; [3] A. E. Saal et al., 2013. Science, 340(6138), 1317–1320; [4] J. P. Greenwood et al., 2011. Nat. Geosci., 4(2), 79–82; [5] J. J. Barnes et al., 2016. Nat. Commun., 7(1), 11684; [6] C. I. Honniball et al., 2021. Nat. Astron., 5(2), 121–127; [7] D. J. Heather et al., 2021. Lunar Planet. Sci. Conf. LPI, Abstract #2111; [8] J. Mortimer et al., 2018. Planet. Space Sci., 158(Feb), 25–33; [9] R. H. Brown et al., 2012. Planet. Space Sci., 60(1), 166–180 [10] R. E. Criss, 1999. USA: Oxford University Press.

How to cite: López Días, V., Pfister, L., Hissler, C., and Barnich, F.: A more robust interpretation of water ice isotope signature from lunar polar missions: theoretical model for isotope fractionation during water ice sublimation in very low pressure systems at cryogenic temperatures., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8169, https://doi.org/10.5194/egusphere-egu22-8169, 2022.

EGU22-8651 | Presentations | PS4.6

Constraints on the lunar magnetic sources location using orbital magnetic field data 

Joana S. Oliveira, Foteini Vervelidou, Mark A. Wieczorek, and Marina D. Michelena

Orbital magnetic field observations of the Moon show several magnetic anomalies distributed heterogeneously across its surface. These observations and results from paleomagnetic studies on lunar rocks corroborates that the lunar crust is locally magnetized. The origin of these magnetic field anomalies is still debated, as most of them are not related to known geological structures or processes. Some of the current suggestions to explain the origin of the anomalies sources include contamination from impactors that could deliver iron-rich material to the lunar surface, and heating associated with localized magmatic activity that could thermochemically alter rocks to produce strong magnetic carriers. Both hypotheses need however an inducing field to magnetize the lunar crust, and strong evidence from previous studies argues in favor of this being a global magnetic field generated by a core dynamo.

In this work, we aim to elucidate the origin of the magnetic anomalies by constraining the location and shape of the underlying magnetization. We do so by inferring the magnetization geometry from orbital magnetic field measurements using an inversion scheme that assumes unidirectional magnetization while making no a priori assumptions about its shape. This method has been used up to now to infer the direction of the underlying magnetisation but it has not yet been used to infer the geometry of the sources. We test the performance of the method by conducting a variety of synthetic tests using magnetized bodies of different geometries such as basins, dykes, and lava tubes, each corresponding to a different possible origin scenario for the observed magnetic anomalies.  Results from our synthetic tests show that the method is able to recover the location and shape of the magnetized volume. We explore how different input parameters, such as shape, depth, thickness, and field direction influence the method’s performance in retrieving the characteristics of the magnetized volume. Such an analysis can be performed on many lunar magnetic anomalies, including those which are not related to swirls or impact craters, i.e., the mechanisms that have been most studied up to now. This will help elucidate the geological history of the Moon and key features of the lunar dynamo evolution.

How to cite: Oliveira, J. S., Vervelidou, F., Wieczorek, M. A., and D. Michelena, M.: Constraints on the lunar magnetic sources location using orbital magnetic field data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8651, https://doi.org/10.5194/egusphere-egu22-8651, 2022.

EGU22-9722 | Presentations | PS4.6

Sensitivity analysis of frequency-dependent visco-elastic effects on lunar orbiters 

Xuanyu Hu, Alexander Stark, Dominic Dirkx, Hauke Hussmann, Agnès Fienga, Marie Fayolle-Chambe, Daniele Melini, Giorgio Spada, Anthony Mémin, Nicolas Rambaux, and Jürgen Oberst

Tidal response of the Moon provides crucial insight into the structure and rheology of the lunar interior (Williams et al. 2013). The body deformation subject to forces raised by external objects, most evidently Earth and the Sun, induces a variability of the gravitational field, which is characterized by the Love number, k. This effect may, in turn, manifest itself over time in the perturbed motion of orbiting spacecraft (Konopliv et al. 2013; Lemoine et al. 2013).

For an elastic body the response to the periodic excitation is instantaneous and relaxation times resulting in phase lags of the response are thus neglected. In reality, the lunar interior exhibits a degree of viscosity and dissipates energy through friction, in which case k not only varies with frequency but also comprises an imaginary part that represents a phase lag in tidal response (Williams et al. 2013).

Here, we investigate the signatures of the frequency-dependent Love number in the motion of a lunar orbiter. We formulate the problem following Williams & Boggs (2015), and focus on the variability of five Stokes' coefficients of the second degree effected by k2. The time-varying components are expanded at given characteristic frequencies associated with (linear combinations of) the Delaunay arguments. We make use of the Technical University Delft Astrodynamics Toolbox (Dirkx et al., 2019; https://tudat-space.readthedocs.io/) to investigate the orbit evolution of lunar orbiters, e.g., the Lunar Reconnaissance Orbiter (Mazarico et al. 2018), subject to the time-varying lunar gravitation. Meanwhile, we leverage the analytic theory of Kaula (1966) to illuminate the impact of such specific yet minute perturbations, especially non-short-period variations of the spacecraft orbit (Kaula 1964; Lambeck et al. 1974; Felsentreger et al. 1976).

A particular interest here is in the potential estimability of the frequency-dependent phase lag. Following Dirkx et al. (2016), we conduct a preliminary study of the sensitivity of spacecraft orbit adjustment to the said tidal effects. That is, we investigate if, under which conditions, and to what degree, the signals in question will be absorbed by the adjustment of initial states or other parameters, a consequence that will effectively prohibit the detection of the tidal effects. The outcome is expected to shed light on the minimum criteria of their estimation and thus instructive to real-world data analysis in the future.

 

Reference

Dirkx, D., et al. (2016), PSS, 134, 84-95
Dirkx, D., et al. (2019), Astrophysics and Space Science, 364:37
Kaula W.M. (1964), Reviews of Geophysics, 2, 661-685
Kaula W.M. (1966), Theory of Satellite Geodesy, Dover Publications, Inc.
Konopliv, A.S., et al. (2013), GRL, 41, 1452-1458 
Lambeck, K., et al. (1974), Reviews of Geophysics and Space Physics, 12, 412-434
Felsentreger, T.L. et al. (1976), JGR, 81, 2557-2563
Lemoine, F.G., et al. (2013), JGRP, 118, 1676-1698
Mazarico, E., et al. (2018), PSS, 162, 2-19
Williams J.G., et al. (2013), JGRP, 119, 1546-1578
Williams J.G., and Boggs, D.H. (2015), JGRP, 120, 689-724

How to cite: Hu, X., Stark, A., Dirkx, D., Hussmann, H., Fienga, A., Fayolle-Chambe, M., Melini, D., Spada, G., Mémin, A., Rambaux, N., and Oberst, J.: Sensitivity analysis of frequency-dependent visco-elastic effects on lunar orbiters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9722, https://doi.org/10.5194/egusphere-egu22-9722, 2022.

EGU22-10171 | Presentations | PS4.6

The Moon Science Working Group of the Lunar Gravitational-Wave Antenna Project 

Alessandro Frigeri, Marco Olivieri, Jan Harms, Alessandro Bonforte, Carlo Giunchi, Goro Komatsu, Josipa Majstorović, Matteo Massironi, and Daniele Melini

Lunar Gravitational-wave Antenna (LGWA) proposes to deploy an array of high-end seismometers on the surface of the Moon. The LGWA network will measure the lunar surface displacement excited by Gravitational waves (GWs) with a targeted observation band of 1mHz – few Hz.   Seismic noise in that frequency band is very low due to the absence of atmosphere and oceans, representing the main inherent advantage that makes the Moon an ideal target for a GW detection experiment. 

The scientific and technical challenges of LGWA are diverse.  Since its initiation, LGWA has relied on experts from fundamental physics, astrophysics, geophysics, engineering, and planetary science. 

The collaboration is currently organized in working groups (WGs) to cover five key themes: GW science, lunar science, payload, deployment, and operations.  

At the beginning of 2022, we started the activities of WG2 to assess the current knowledge of the lunar environment. We aim to characterize and develop models of deployment scenarios suitable for LGWA sensors, via a multi-pronged approach of data analysis and on-field experiments probing terrestrial analogs of lunar terrains. 

Besides characterizing the lunar seismic background noise, other goals of the group are related to modeling the lunar interior structure as well as Moon’s normal modes. These will be further used to develop a model of the interaction between the Moon and GWs. The knowledge about the displacement level of this excitation and the background noise will be used to define novel techniques for background noise reduction.

For this purpose, WG2 is composed of physicists, engineers, geophysicists, and geologists. For our activities, we chose an interdisciplinary approach that requires initial communication efforts to create a common ground that will evolve into a crucial baseline activity for the whole LGWA project.

Here we will report our progress in the first months of the activity of our collaboration.     

How to cite: Frigeri, A., Olivieri, M., Harms, J., Bonforte, A., Giunchi, C., Komatsu, G., Majstorović, J., Massironi, M., and Melini, D.: The Moon Science Working Group of the Lunar Gravitational-Wave Antenna Project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10171, https://doi.org/10.5194/egusphere-egu22-10171, 2022.

Mons Hansteen Alpha is a lunar ‘red spot’ that is now considered to be of non-mare volcanic origin. In addition to being characterized by an evolved silicic composition, Mons Hansteen Alpha is also of interest because of the presence of Mg-spinel exposures in association with the siliceous lithology, as detected by the Moon Mineralogy Mapper on board the Chandrayaan-1 mission. The Compton-Belkovich volcanic complex on the Moon is the only other established example of this kind. The origin of Mg-spinel exposures on the lunar surface is considered to be either impact related or endogenic. Models have been proposed in earlier studies to explain the spinel exposures on anorthosites, and spinel in association with other mafic minerals such as olivine and orthopyroxene. However, the origin of Mg-spinel exposures within an evolved siliceous body that has very limited associated mafic minerals is yet to be fully explored. In this study, the Mg-spinel exposures on Mons Hansteen Alpha were analyzed using high resolution LROC NAC images and correlated with topographic information from the SLDEM data. These investigations suggest that in most cases, the spinel exposures on Mons Hansteen are not related to any impact related structures. The exposures are often found on elevated features such as ridges, or around irregular-shaped pits. The distribution of the exposures is mostly limited to the Pitted unit, the youngest unit in the volcanic structure; this favours an endogenic origin instead of one related to impact as otherwise, the exposures would also have been distributed in the other units. On the bases of these observations, it is suggested that the Mg-spinel exposures on Mons Hansteen Alpha are endogenic in nature. A model is proposed for the origin of endogenic Mg-spinel exposures on silicic volcanic structures. For this, model reactions were considered between a lunar picritic basaltic magma and two types of crustal protoliths- (i) a mixture of silica and anorthosite and (ii) a lunar monzogabbro. The modelling has been done using the alphaMELTS 2 software. The proposed model combines the crustal melting model for the genesis of silicic volcanic structures with a genetic model for the Mg-spinel exposures. The mixture of silica and anorthosite has been considered as a possible crustal protolith consistent with recent experimental lunar magma ocean (LMO) crystallization models that crystallized silica as one of the end stage products. On the other hand, earlier studies have proposed monzogabbro as a possible protolith composition for lunar silicic lithology. The models demonstrate the possible pathways of forming silicic compositions similar to the lunar granite samples collected during the Apollo missions, with simultaneous crystallization of Mg-spinel.

How to cite: Moitra, H. and Gupta, S.: Investigating the origin of Mg-spinel exposures on Mons Hansteen Alpha, an evolved silicic volcanic structure on the Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10274, https://doi.org/10.5194/egusphere-egu22-10274, 2022.

Understanding whether the Moon had a long-lived magnetic field is crucial for determining how the lunar interior and surface evolved, and in particular for assessing whether a paleomagnetosphere shielded the regolith. Magnetizations from some Apollo samples have been interpreted as records of a global lunar magnetic field between approximately 4.2 and 1.5 Ga that would have created shielding, but the inferred paleofields are too strong and continuous to be generated by the small lunar core. Moreover, vast areas of the lunar crust lack magnetic anomalies that should mark the past presence of a dynamo. New paleointensity data from an Apollo impact glass associated with a young 2 million-year-old crater records a strong Earth-like magnetization, providing evidence that impacts can impart intense signals to samples recovered from the Moon, and other planetary bodies (Tarduno, Cottrell, Lawrence et al., Science Advances, 2021). This observation provides motivation for future lunar collections to constrain impact size - magnetization scaling relationships. Moreover, new data from silicate crystals bearing magnetic inclusions from Apollo samples formed at 3.9, 3.6, 3.3, and 3.2, Ga are capable of recording strong core dynamo-like fields but do not, indicating the lack of a global magnetic field (Tarduno, Cottrell, Lawrence et al., Science Advances, 2021). Together, these new data indicate that the Moon did not have a long-lived core dynamo. As a result, the Moon was not sheltered by a sustained paleomagnetosphere, and the lunar regolith should hold buried 3He, water, and other volatiles resources acquired from solar winds and Earth’s magnetosphere over some 4 billion years. These findings highlight the opportunity to learn about the evolution of the solar wind and Earth’s earliest atmosphere during future lunar exploration. This could in turn provide key data to better understand how Earth evolved as a habitable planet despite the expected extreme solar forcing during its first billion years (Tarduno, Blackman, Mamajek, Phys. Planet Inter., 2014).

How to cite: Tarduno, J.: Absence of a long-lived lunar paleomagnetosphere and opportunities for future exploration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10400, https://doi.org/10.5194/egusphere-egu22-10400, 2022.

EGU22-10626 | Presentations | PS4.6

Measurement of tidal deformation through self-registration of laser profiles: Application to Earth’s Moon 

Alexander Stark, Haifeng Xiao, Xuanyu Hu, Agnès Fienga, Hauke Hussmann, Jürgen Oberst, Nicolas Rambaux, Antony Mémin, Arthur Briaud, Daniel Baguet, Giorgio Spada, Daniele Melini, and Christelle Saliby

Many moons of the Solar System, e.g. the Galilean satellites or Earth’s Moon, are subject to strong tidal deformations. Measurements of the tidal Love number h2 by laser altimeters from orbiting spacecraft may provide crucial constraints on their interior structures and rheology. Using precise observations by laser altimeters estimates for h2 were obtained for the Moon (Mazarico et al. 2014, Thor et al., 2021) and Mercury (Bertone et al., 2021), and are planned for Ganymede (Steinbrügge et al., 2015). Typically, height differences at crossing points of laser profiles, so called crossover points, are used for such measurements (Mazarico et al. 2014, Bertone et al., 2021). However, a new method based on simultaneous inversion of tidal deformations and global topography has recently been demonstrated (Thor et al. 2021) using data from the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO).

 

Here we propose the refined “self-registration” method, which makes use of an accurate reference digital terrain model (DTM) constructed from the laser profiles themselves. This DTM is obtained by iteratively co-registering random subsets of laser profiles to an intermediate DTM produced by the other profiles. With our method we are not limited to profiles that are actually crossing themselves and can obtain height difference between all available profiles. Moreover, we can overcome the interpolation error at the crossover points as we use the entire profile with all its data points to measure the relative height differences. This method was recently successfully applied to measure the seasonal change of the ice/snow level in polar regions of Mars using Mars Orbiter Laser Altimeter (MOLA) data (Xiao et al., 2021).

 

In order to validate our method and assess its performance we perform a simulation of a tidal signal in the LOLA data with an assumed value for the tidal Love number h2 of the Moon. Thereby the height measurement at the location of the LOLA footprint is derived from a DTM and an artificial tidal signal applied on it. Thereby, we consider viscoelastic effects on the tidal deformation and different tidal frequencies. With the help of these simulations we assess the accuracy of the h2 measurement and check the sensitivity to the measurement of the tidal phase lags.

 

References:

Mazarico et al. (2014). Detection of the lunar body tide by the Lunar Orbiter Laser Altimeter. GRL, 41(7), 2282-2288. doi:10.1002/2013GL059085

Thor et al. (2021). Determination of the lunar body tide from global laser altimetry data. JoG, 95(1). doi:10.1007/s00190-020-01455-8

Bertone et al. (2021). Deriving Mercury Geodetic parameters with Altimetric Crossovers from the Mercury Laser Altimeter (MLA). JGR-Planets, 126(4), e2020JE006683. doi:10.1029/2020JE006683

Xiao et al. (2021). Prospects for Mapping Temporal Height Variations of the Seasonal CO2 Snow/Ice Caps at the Martian Poles by Co-registration of MOLA Profiles. Under review in PSS, https://arxiv.org/abs/2109.04899

How to cite: Stark, A., Xiao, H., Hu, X., Fienga, A., Hussmann, H., Oberst, J., Rambaux, N., Mémin, A., Briaud, A., Baguet, D., Spada, G., Melini, D., and Saliby, C.: Measurement of tidal deformation through self-registration of laser profiles: Application to Earth’s Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10626, https://doi.org/10.5194/egusphere-egu22-10626, 2022.

EGU22-10764 | Presentations | PS4.6

Effect of Volcanically-Induced Transient Atmospheres on Transport and Deposition of Lunar Volatiles. 

Igor Aleinov, Michael Way, James Head, Konstantinos Tsigaridis, Chester Harman, Eric Wolf, Guillaume Gronoff, Matthew Varnam, and Christopher Hamilton

While the origin of lunar polar volatiles remains an open question, their most likely sources are volcanic outgassing or volatile-rich impactors. Both such sources are sporadic in nature and are characterized by release of large amounts of volatiles over a short period of time and long periods of repose between such events. If a sufficient amount of volatiles was generated in such a delivery event, a transient collisional atmosphere could form. Such an atmosphere, if it persists for a long enough time, would protect certain volatiles (like water) from photodissociation and escape to space and would promote their transport to the polar cold traps where they could be stored and preserved for billions of years. Hence, such transient atmospheres could have a significant impact on the distribution and abundance of volatiles currently observed on the Moon. Here we study such a hypothetical atmosphere that could have been formed due to volcanic outgassing during the peak of lunar volcanic activity at ~3.5 Ga and investigate its longevity, climatology and effect on volatile transport.

We employ the ROCKE-3D [1] planetary climate model to simulate processes in a volcanically-induced lunar atmosphere. We use orbital and radiation parameters corresponding to conditions at 3.5 Ga (17.8 days rotation period and a solar constant 75% of the modern value). For most experiments we use zero obliquity, though we investigate the effect of non-zero obliquity on atmospheric stability and volatile transport. We assume a CO2-dominated atmosphere in accordance with predictions of our chemistry model [2]. For the atmospheric thickness we follow the argument of Head et al. [3] that due to long periods of repose between the volcanic events the atmosphere would not accumulate above the pressure of a few microbars, and thus we limit our parameter space to a range of 1 microbar to 1 mb surface pressures. To investigate the ability of such an atmosphere to transport volatiles we set up a typical volcanic eruption experiment [4] and follow the fate of the outgassed water.

In most of our experiments the atmosphere was stable, though in some cases a small non-zero obliquity (a few degrees) was needed to prevent a collapse due to CO2 condensation at the poles. We found that even very thin atmospheres were efficiently transporting volatiles to the poles. The efficiency of transport sometimes was higher for thinner atmospheres, most likely due to a stronger circulation cell. We also found that water transport efficiency depended on initial conditions at the surface. A water-free dry surface suppressed re-evaporation, thus reducing the total flux of outgassed water to the poles. But even in the case of dry soil, water transport was efficient with 19% of outgassed water delivered to the poles in just a few months (for the 10 microbar atmosphere).

References: [1] Way M. J. et al. (2017) ApJS, 231, 12. [2] Aleinov I. et al.  (2019) GRL, 46, 5107–5116. [3] Head J. W. et al. (2020) GRL, 47, e2020GL089509. [4] Wilson L. and Head J. W. (2018) GRL, 45, 5852-5859.

 

How to cite: Aleinov, I., Way, M., Head, J., Tsigaridis, K., Harman, C., Wolf, E., Gronoff, G., Varnam, M., and Hamilton, C.: Effect of Volcanically-Induced Transient Atmospheres on Transport and Deposition of Lunar Volatiles., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10764, https://doi.org/10.5194/egusphere-egu22-10764, 2022.

China’s first lunar sample return mission, Chang’E-5, has collected 1.731 kg samples from one of the youngest mare basalt units in the northern Oceanus Procellarum. In this study, we conducted a systematical analysis on regolith properties at the landing site using optical, multispectral, thermal infrared and radar observations, and then traced regolith provenance using ejecta deposition models.


The CE-5 landing site is within a flat (< 5° in slope), young (˜1.3 Ga), intermediate titanium (4.6 wt.%) mare basalt unit, named P58/EM4, which is surrounded by several older, low titanium mare basalt units. In the Kaguya Multiband Imager TiO2 map, some impact craters have low titanium ejecta blankets (e.g., Mairan G), indicating that they have excavated the underlying low titanium materials. Size and spatial distribution of these craters suggest that the basalt is thicker in the center of unit P58 and thinner around the perimeter with thickness from ˜15 to ˜50 m. Morphologies of small fresh craters identified in high-resolution optical images show that regolith thickness varies from ˜1.5 to ˜8 m with a median value of ˜5 m. A comparison between Mini-RF radar image and Lunar Reconnaissance Orbiter Diviner surface rock abundance (RA) map indicates that subsurface rocks play a significant role in producing the observed radar backscatter. Further analysis of the radar echo suggests that subsurface RA is ˜0.47%–0.88% if the effective size is 3 cm, which can explain the shallow sampling depth (˜0.9 m) of the CE-5 drilling device.


To study sample provenance, deposition history and stratigraphy of landing site, we established a catalogue of 1896 craters that can deposit materials to the landing site. Our analysis shows that 80% of the primary ejecta (˜0.6 m) sampled by CE-5 comes from 12 craters within 1 km range from the landing site, and that XuGuangqi crater (46–90 Ma) contributes about 50%. There are four major source craters outside P58 unit, and their primary ejecta contribution is less than 10%. The detailed locations and depths of ejecta at landing site are given by using Maxwell Z-model (e.g., for XuGuangqi crater, 18.7–43.7 m depth and 112.3–123.0 m from crater center). Based on the age of the major craters, we further simulated the deposit thickness and composition profile of the regolith at landing site using the Monte Carlo and ballistic sedimentation model. The results show that the craters totally produced ˜1.1 m thick ejecta deposits, and the uppermost ˜0.46 m consists of primary ejecta from XuGuangqi and a smaller crater near landing site. The model predicts that FeO and TiO2 abundances decrease with depth, to a minimum value at ˜0.1 m, and then increase and become constant with depth. This can provide a feasible way to identify the provenance of single sample by using FeO and TiO2 abundances.


This study provides key information about geological context, regolith property, sample provenance and stratigraphy of landing site, which is critical for explaining laboratory measurements of CE-5 samples.

How to cite: Jia, B. and Fa, W.: Properties and provenance of the lunar regolith at Chang’E-5 landing site: Constraints from remote sensing observations and ejecta deposition models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10988, https://doi.org/10.5194/egusphere-egu22-10988, 2022.

EGU22-12217 | Presentations | PS4.6

Estimating Lunar Rock Abrasion Stage using Photometric Studies 

Rachael Martina Marshal, Ottaviano Rüsch, Christian Wöhler, and Kay Wohlfarth

The study and investigation of local scale geological features (boulders and boulder fields) of planetary/asteroid surfaces can provide insight on the evolution of the regolith and the contribution of various processes to their formation. Numerous studies have employed photometric modelling to study the surface properties of the lunar regolith on a regional and local scale (e.g., [1], [2], [3])

In this study we employ photometric methods to study the properties of boulder fields/rock fragments in a multiscale approach from resolved (meter scale) to sub pixel (cm scale). In our approaches we use the Hapke model [4] on LROC NAC data [5]. The retrieved properties of boulders, in particular their shape, can in turn shed light on the boulder material strength and surface exposure time [6].

Usually, photometric studies (e.g., [2]) consider the Hapke parameters SSA (single scattering albedo), b, c, theta_bar (roughness) as unknown and estimate them by inversion. Here we take a different approach and strongly constrain the possible combinations of the four parameters. The constraint is facilitated by the knowledge of the geological context of the surface either above (sub pixel approach) or below (resolved boulder field approach) the image resolution, visually inferred with images.

We are interested in the relative probability of each geologic context for a given region. This information is sufficient reveal information about the possible micro-scale geology of a region, namely the shape, and thus degradation, of rocks. We apply these techniques to the boulder fields in the vicinity of the Apollo 16 landing site at North Ray crater.

Our approach consists of the construction of a set of digital terrain models (DTMs) representative of the most possible geologic contexts. The contexts are described by the rock and debris apron shape and reflect the abrasion stage of the rock – Non-Abraded (flat top), Non-Abraded (angular), Mildly and Highly Abraded. The size-frequency distribution of the rocks follows a power-law [1]. The rock abundance is either measured (resolved scale analysis) or set as a free parameter (unresolved scale analysis). The size and spatial resolution of the DTM is defined by the scale of the analysis, either resolved or unresolved by LROC NAC. The Hapke reflectance model [4] is then used to illuminate these DTMs. Direct comparison of the reflectance at two phase angles as well as the Normalized Log Phase Ratio Difference value is carried out for the unresolved and resolved scale analysis, respectively.

References:

[1] Watkins R.N. et al. (2019) JGR-Planets, 124, 2754–2771 [2] Sato et al. (2014) JGR-P, 119,1775-1805 [3] Lin et al. (2020) A&A,638 [4] Hapke (2012) Theory of Reflectance and Spectroscopy [5] Robinson M.S. et al. (2010) SSR,150,81-124 [6] Rüsch and Wöhler (2021) submitted to Icarus arXiv:2109.00052v1

 

How to cite: Marshal, R. M., Rüsch, O., Wöhler, C., and Wohlfarth, K.: Estimating Lunar Rock Abrasion Stage using Photometric Studies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12217, https://doi.org/10.5194/egusphere-egu22-12217, 2022.

EGU22-12932 | Presentations | PS4.6

Lunar TLP's and the tectonic processes of the Earth and the Moon 

Dimitar Ouzounov, Patrick Taylor, Menas Kafatos, and Kayden Cutchins

We are studying the transient lunar phenomena (TLP) as an indicator of lunar tectonics. Seismic events can be used as a direct indicator of some tectonic activities of the planets. The Moon-Earth gravitational interaction has been studied extensively as a triggering mechanism for earthquakes. However, this is a controversial topic. Our present study investigated the reverse Earth-Moon interaction concerning the TLP activities. The lunar outgassing is potentially the leading source of TLP activities. We have investigated both Earth venting and earthquakes and have found that radon was frequently activated before significant seismic events due to the Moon-Sun interaction with the Earth (Ouzounov et al., 2018). Earthquake lights, an associated phenomenon reported before some major earthquakes, are analogous to TLP activities on the Moon. In 1972, N. Kozyrev suggested a possible lunar response to the significant seismic events on the Earth. To understand whether TLP's have any possible connection with earthquakes, we performed a statistical review between significant earthquakes, using the NEIC catalog and TLPs during 1907-1977, for four lunar areas: Aristarchus, Plato, Gassendi, and Alphonsus. We used TLP catalogs published by Middlehurst et al. 1968; Cameron, 2006; and Crotts, 2008.  Our results revealed a causal relationship between significant earthquakes and TLP events. However, the strength of this relationship varies from the location and depth of the earthquakes. Deformation on the Moon triggers the degassing process, and TLPs are indicators for those underlying activities. Our work can provide new information about the origin of TLP and the existence of a possible relationship between the tectonic processes of Earth and the Moon. The Earth causes crustal tides on the Moon, and the Moon produces tides on the Earth.

 

How to cite: Ouzounov, D., Taylor, P., Kafatos, M., and Cutchins, K.: Lunar TLP's and the tectonic processes of the Earth and the Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12932, https://doi.org/10.5194/egusphere-egu22-12932, 2022.

EGU22-13240 | Presentations | PS4.6

The evolution of lunar rock size-frequency distributions: An updated model 

Ottaviano Ruesch, Rachael M. Marshal, Wajiha Iqbal, Jan Hendrik Pasckert, Carolyn H. van der Bogert, and Markus Patzek

The model for the catastrophic rupture of rocks on the lunar surface [1] is revisited by considering new functions describing rock shattering by impacts and size-frequency distributions of meteoroids. The input functions are calibrated by comparing the model block size–frequency
distributions with the measured size–frequency distribution of ejecta blocks around Tycho crater, which formation age is known. We find that the evolution of lunar block size–frequency distribution in the range 1–50 m is as follow: For young (≤ 50
Myr) population, the size–frequency distribution is best approximated by a power law, whereas for older populations, the extrapolation at small diameters is best performed by an exponential
distribution. New destruction rates are in better agreement with recent measurements [2,3] compared to the original model. For rocks above ~5 cm the survival time increases with increasing size, whereas for rocks below ~5 cm the survival time slightly increases with decreasing size. The updated model allows the estimation of both the exposure age and the initial abundance of a block field using the measurement of a block size–frequency distribution from LROC/NAC images.


References: [1] Hoerz et al., 1975, The Moon 13, 235–258. [2] Basilevsky et al., 2013, PSS, 89 (118–12). [3] Ghent et al., 2014, doi:10.1130/G35926.1.

How to cite: Ruesch, O., Marshal, R. M., Iqbal, W., Pasckert, J. H., van der Bogert, C. H., and Patzek, M.: The evolution of lunar rock size-frequency distributions: An updated model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13240, https://doi.org/10.5194/egusphere-egu22-13240, 2022.

EGU22-13340 | Presentations | PS4.6

ArtMoonMars Science, Cultural and Artistic programme: towards an Artscience Museum on the Moon  

Bernard Foing and ILEWG Lunar Explorers team and the ArtMoonMars collaboration team

The ArtMoonMars programme of   cultural and artistic activities was started in 2010 by ILEWG Lunar Explorers Group in collaboration with ESA ESTEC and number of partner institutions, with more than 45 events (workshops, space artscience classes, public events, sessions at international conferences) and exhibitions.

What payload for an Artscience Museum on the Moon ?  For prototype ExoGeoLab lander in 2009. the team looked at possibility to host cultural or artscience  payload. Some joint ArtMoonMars events between space science, technology and art communities were organized, such as MoonLife Academy in 2010 .

ArtMoonMars organised classes of Artscience & Space at Royal Academy of Fine Arts in the Hague KABK –ESTEC. Artscience students participated to workshops at ESTEC & KABK and developed projects inspired by space and the Moon. These ArtScience classes were conducted 3 years with different themes. Some 50 ArtScience & Space projects were developed by students. Artists demos with scientists and engineers, including visual, electronic, VR artefacts and art performances.

ITACCUS The Committee for the Cultural Utilisation of Space (ITACCUS, created in 2006) https://www.iafastro.org/about/iaf-committees/technical-committees/committee-for-the-cultural-utilisation-of-space-itaccus.html

MoonGallery Foundation: The MoonGallery idea and concept was developed from 2010, to send an expanded gallery of artscience artefacts to the Moon on possible landers. on Gallery will launch 100 artefacts to the Moon within the compact format of 10 x 10 x 1cm plate on a lunar lander exterior panelling as early as 2022. .

A MoonGallery project team was formed in 2018 to issue a call for the community of artists. For these activities, ILEWG established ArtMoonMars grants to MoonGallery curators, and to some artists or temporary team members.

MoonMars Foundation : A new effort with external partner building on previous ArtMoonMars and EuroMoonMars programmes led to the definition of a new MoonMars foundation with broader objectives to develop opportunities and funding, to various groups including space artists.

Space Renaissance and Art: Space Renaissance International (SRI) is a global organisation dedicated to getting humanity off-world, not just astronauts engaged in pioneering exploration. The early Space Renaissance concept was founded on a pragmatic form of the humanist philosophy, with its roots here on Earth, and with its destiny among the stars. The founders took the historical Renaissance era with its focus on patronage of the arts and sciences as a model for a New Renaissance, a Space Renaissance. SRI runs a number of programs, projects and activities in support of its mission. It has started a Space Renaissance Art chapter.

How to cite: Foing, B. and team, I. L. E. and the ArtMoonMars collaboration team: ArtMoonMars Science, Cultural and Artistic programme: towards an Artscience Museum on the Moon , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13340, https://doi.org/10.5194/egusphere-egu22-13340, 2022.

ST3 – Ionosphere and Thermospere

EGU22-1089 | Presentations | NP0.1

Tropical Background and Wave Spectra: Contribution of Wave–Wave Interactions in a Moderately Nonlinear Turbulent Flow 

Nathan Paldor, Chaim I. Garfinkel, and Ofer Shamir

Variability in the tropical atmosphere is concentrated at wavenumber–frequency combinations where linear theory indicates wave modes can freely propagate, but with substantial power in between. This study demonstrates that such a power spectrum can arise from small-scale convection triggering large-scale waves via wave–wave interactions in a moderately turbulent fluid. Two key pieces of evidence are provided for this interpretation of tropical dynamics using a nonlinear rotating shallow-water model: a parameter sweep experiment in which the amplitude of an external forcing is gradually ramped up, and also an external forcing in which only symmetric or only antisymmetric modes are forced. These experiments do not support a commonly accepted mechanism involving the forcing projecting directly onto the wave modes with a strong response, yet still simulate a power spectrum resembling that observed, though the linear projection mechanism could still complement the mechanism proposed here in observations. Interpreting the observed tropical power spectrum using turbulence offers a simple explanation as to why power should be concentrated at the theoretical wave modes, and also provides a solid footing for the common assumption that the background spectrum is red, even as it clarifies why there is no expectation for a turbulent cascade with a specific, theoretically derived slope such as −5/3. However, it does explain why the cascade should be toward lower wavenumbers, that is an inverse energy cascade, similar to the midlatitudes even as compressible wave modes are important for tropical dynamics.
It also explains why  in satellite observations and reanalysis data, the symmetric component is stronger than the anti-symmetric component, as any bias in the small-scale forcing from isotropy, whether symmetric or antisymmetric, leads to symmetric bias in the large-scale spectrum regardless of the source of variability responsible for the onset of the asymmetry.


Shamir, O., C. Schwartz, C.I. Garfinkel, and N. Paldor, The power distribution between symmetric and anti-symmetric components of the tropical wavenumber-frequency spectrum, JAS, https://doi.org/10.1175/JAS-D-20-0283.1 .
Garfinkel, C.I., O. Shamir, I. Fouxon, and N. Paldor, Tropical background and wave spectra: contribution of wave-wave interactions in a moderately nonlinear turbulent flow, JAS, https://doi.org/10.1175/JAS-D-20-0284.1.
Shamir, O., C.I. Garfinkel, O. Adam, and N. Paldor, A note on the power distribution between symmetric and anti-symmetric components of the tropical Brightness Temperature spectrum in the wavenumber-frequency plane , JAS,doi: 10.1175/JAS-D-21-0099.1.

How to cite: Paldor, N., Garfinkel, C. I., and Shamir, O.: Tropical Background and Wave Spectra: Contribution of Wave–Wave Interactions in a Moderately Nonlinear Turbulent Flow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1089, https://doi.org/10.5194/egusphere-egu22-1089, 2022.

EGU22-2192 | Presentations | NP0.1

Nonlinear subcritical and supercritical thermal convection in a sphere 

Tobias Sternberg and Andrew Jackson
Fluids that are subject to temperature gradients (or internal heating) and a gravity force will begin convecting when the thermal forcing, conventionally measured by the nondimensional Rayleigh number Ra exceeds a critical value. The critical value RL for the transition from a static, purely conductive state to an advective state can be determined by linearising the equations of motion and formulating an associated characteristic value problem. We discuss two aspects of fluid behaviour away from this point:
(i) Highly supercritical behaviour, and the asymptotic behaviour of heat transport in the highly nonlinear regime. (ii) Subcritical behaviour for Ra<RL, which may be possible for finite amplitude fluid motions. We work in both full sphere and shell geometries, with various forms of heating and gravitational profiles. We report on both theoretical developments and direct numerical simulations using highly accurate fully spectral methods for solving the relevant equations of motion and of heat transfer.

How to cite: Sternberg, T. and Jackson, A.: Nonlinear subcritical and supercritical thermal convection in a sphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2192, https://doi.org/10.5194/egusphere-egu22-2192, 2022.

EGU22-2238 | Presentations | NP0.1

Direct evidence of an oceanic dual kinetic energy cascade and its seasonality from surface drifters 

Jin-Han Xie, Dhruv Balwada, Raffaele Marino, and Fabio Feraco

Ocean turbulence causes flows to split into smaller whirls or merge to make larger whirls, cascading energy to small or large scales respectively. Conventional ocean dynamics dictates that the kinetic energy in the ocean will cascade primarily to larger scales, via the inverse energy cascade, and has raised the question of how the kinetic energy in the ocean dissipates, which would necessarily require the transfer towards the molecular scales. However, so far no clear observational quantification of the energy cascade at the scales where these mechanisms are potentially active has been made. By using forcing-scale resolving third-order structure-function theory, which captures bidirectional energy fluxes and is applicable beyond inertial ranges, we analyse data from surface drifters, released in dense arrays in the Gulf of Mexico, to obtain the kinetic energy flux magnitude and directions along with the energy injection scales. We provide the first direct observational verification that the surface kinetic energy cascades to both small and large scales, with the forward cascade dominating at scales smaller than approximately 1-10km. Our results also show that there is a seasonality in these cascades, with winter months having a stronger injection of energy into the surface flows and a more energetic cascade to smaller scales. This work provides exciting new opportunities for further probing the energetics of ocean turbulence using non-gridded sparse observations, such as from drifters, gliders, or satellites.

How to cite: Xie, J.-H., Balwada, D., Marino, R., and Feraco, F.: Direct evidence of an oceanic dual kinetic energy cascade and its seasonality from surface drifters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2238, https://doi.org/10.5194/egusphere-egu22-2238, 2022.

According to the classic energy cascade notion, large eddies as energy carrier are unstable to break up, through which energy is transferred from large scales till the smallest ones to dissipate the kinetic energy. A fundamental issue hereof is how to quantify the eddies of different sizes, else the energy cascade scenario remains illustrative. A possible remedy is the idea of dissipation element (DE) analysis, which is a topological approach based on extremal points. In this method, starting from each spatial point in a turbulent scalar field ϕ, a local minimum point and a local maximum point will inevitably be reached along the descending and ascending directions of the scalar gradient trajectory, respectively. The ensemble of spatial points whose gradient trajectories share the same pair of minimum and maximum points define a spatial region, called a DE. The entire filed can thus be partitioned into space-filling DEs. Typically, DE can be parameterized with l, the linear distance between the two extremal points, and ∆ϕ = ϕ_max – ϕ_min, the absolute value of the scalar quantity difference between the two extremal points. It needs to mention that dependence of the DE structure on the ϕ field is conformal with the physics that different variable fields are different structured, although related. In the past years, DE analysis has been implemented to understand the turbulence dynamics under different conditions. Since inside each DE, the monotonous change of the field variable (from ϕ_min  to ϕ_max  along the trajectory) depicts a laminar like structure in a local region, the space-filling DEs can be recognized as the smallest eddies.

In a more general sense, a newly defined multi-level DE structure has been developed. Introducing the size of the observation window S, extremal points are multi-level, based on which the DE structure can be extended to multi-level. At each S-level, the turbulent field can be decomposed into space-filling DEs, which makes it possible to understand to entire field from the properties of such individual units. In this sense, it is tentatively possible to define turbulent eddies of different scales as DEs at different S-levels. Conventional analyses based on “turbulent eddies” can be implemented using such idea. For instance, during energy cascade, eddy breakup corresponds to the splitting of DEs at higher levels (with larger S) to smaller ones at lower levels (with smaller S). Because of DE can be exactly defined, eddies can be quantified as well, but not just demonstrative. Such kind of multi-level DE structure is uniquely different from other existing approaches (e.g. vortex tube, PoD, Fourier analysis etc.) in the following senses. First, DEs at any S-level are quantitatively defined, rather than qualitatively visualized. Second, DEs at any S-level are space-filling.  The multi-level DE approach is generally applicable in turbulence analysis.

How to cite: Wang, L.: Quantification of “turbulent eddies” in energy cascade based on the multi-level dissipation element structure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3335, https://doi.org/10.5194/egusphere-egu22-3335, 2022.

EGU22-3918 | Presentations | NP0.1

Turbulent intermittency as a consequence of stationarity of the energy balance 

Sébastien Aumaitre and Stéphan Fauve

In his seminal work on turbulence, Kolmogorov made use of the stationary hypothesis to determine the Power Density Spectra of velocity field in turbulent flows. However to our knowledge, the constraints that stationary processes impose on the fluctuations of power have never been used in the context of turbulence. Here we recall that the Power Density Spectra of the fluctuations of the injected power, the dissipated power and the energy flux have to converge to a common value at vanishing frequency. Hence, we show that the intermittent GOY-shell model fulfills these constraints on the power as well as on the energy fluxes. We argue that they can be related to intermittency. Indeed, we find that the constraints on the power fluctuations imply a relation between scaling exponents, which is consistent with the GOY-shell model and in agreement with the She-Leveque formula. It also fixes the intermittent parameter of the log-normal model at a realistic value. The relevance of these results for real turbulence is drawn in the concluding remarks.

How to cite: Aumaitre, S. and Fauve, S.: Turbulent intermittency as a consequence of stationarity of the energy balance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3918, https://doi.org/10.5194/egusphere-egu22-3918, 2022.

EGU22-5934 | Presentations | NP0.1

Scalewise Universal Relaxation to Isotropy of Inhomogeneous Atmospheric Boundary Layer Turbulence 

Ivana Stiperski, Gabriel G. Katul, and Marc Calaf

The turbulent energy cascade is one of the most recognizable characteristics of turbulent flow. Still, representing this tendency of large-scale anisotropic eddies to redistribute their energy content with decreasing scale, a phenomenon referred to as return to isotropy, remains a recalcitrant problem in the physics of turbulence. Atmospheric turbulence is characterised by large scale separation between production and viscous destruction of turbulent kinetic energy making it suitable for exploring such scale-wise redistribution of energy among velocity components.  Moreover, real-world atmospheric turbulence offers an unprecedentedly diverse source of inhomogeneity and large-scale anisotropy (caused by shear, buoyancy, terrain-induced pressure perturbations, closeness to the wall) while maintaining a high Reynolds number state. It may thus be assumed that relaxation through the energy cascade may be dependent on the anisotropy source, thus adding to the ways that atmospheric turbulence differs from canonical turbulent boundary-layers.

Here, we examine the scalewise return to isotropy for an unprecedented dataset of atmospheric turbulence measurements covering flat to mountainous terrain, stratification spanning convective to very stable conditions, surface roughness ranging over several orders of magnitude, various distances from the surface, and Reynolds numbers that far exceed the limits of direct numerical simulations and laboratory experiments.  The results indicate that irrespective of the complexity of the dataset examined, the return-to-isotropy trajectories that start from specific initial anisotropy at large scales show surprising scalewise universality in their trajectories towards isotropy. This novel finding suggests that the effects of boundary conditions, once accounted for in the starting anisotropy of the trajectory in the cascade, cease to be important at much smaller scales. It can therefore be surmised that large-scale anisotropy encodes the relevant information provided by the boundary conditions, adding to the body of evidence that the information on anisotropy is a missing variable in understanding and modelling atmospheric turbulence [1-3].

 

[1]  Stiperski I, and M Calaf. Dependence of near-surface similarity scaling on the anisotropy of atmospheric turbulence. Quarterly Journal of the Royal Meteorological, 144, 641-657, 2017.

[2]  Stiperski I, M Calaf and MW Rotach. Scaling, anisotropy, and complexity in near-surface atmospheric turbulence. Journal of Geophysical Research: Atmospheres, 124, 1428-1448, 2019.

[3] Stiperski I, GG Katul, M Calaf. Universal return to isotropy of inhomogeneous atmospheric boundary layer turbulence. Physical Review Letters, 126 (19), 194501, 2021

How to cite: Stiperski, I., Katul, G. G., and Calaf, M.: Scalewise Universal Relaxation to Isotropy of Inhomogeneous Atmospheric Boundary Layer Turbulence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5934, https://doi.org/10.5194/egusphere-egu22-5934, 2022.

EGU22-7004 | Presentations | NP0.1

Turbulent Energy Cascade in the Gulf of Mexico 

Yinxiang Ma, Jianyu Hu, and Yongxiang Huang

Due  to the extreme complexity of the oceanic dynamics, e.g., stratification, air-sea interaction,  waves, current, tide, etc., the corresponding turbulent cascade remains unknown. The third-order longitudinal structure-function is often employed to diagnose  the cascade direction and intensity, which is written as  SLLL(r)=< Δ uL3(r)>, where Δ uL is the  velocity increment along the distance vector r, and r is the modulus of r. In the case of  three-dimension homogeneous and isotropic turbulence, SLLL(r) is scaled as -4/5εr in the inertial range, where ε is the energy dissipation rate per unit.  In this work, SLLL(r) is estimated for two experimental velocities that obtained in the Gulf of Mexico, namely Grand LAgrangian Deployment (GLAD) and the LAgrangian Submesoscale ExpeRiment (LASER). The experimental SLLL(r) for both experiments shows a transition from negative values to a positive one roughly at rT=10km, corresponding to a timescale  around τT=12-hour (e.g., τT=rT/urms with urms ≈0.24m/s.  Power-law is evident for the scale on the range 0.01≤ r≤1km as SLLL(r)∼ -r1.45±0.10, and for the scale on the range 30≤ r≤300km as SLLL(r)∼ r1.45±0.10. Note that a weak stratification with depth of 10∼15m has been reported for the GLAD experiment, indicating a quasi-2D flow topography. The scaling ranges are above this stratification depth. Hence, the famous Kraichnan's 2D turbulence theory or the geostrophic turbulence proposed by Charney are expected to be applicable. However, due to the complexity of real oceanic flows, hypotheses behind these theories cannot be verified either directly or indirectly. To simplify the situation, we still consider here the sign of  SLLL(r) as an indicator of the energy cascade. It thus suggests a possible forward energy cascade below the spatial scale rT, and an inverse one above the scale  spatial rT.  While, the scaling exponents 1.45 are deserved more studied in the future if more data is available.

 

Ref.

Charney, J. G. (1971). Geostrophic turbulence. J. Atmos. Sci., 28(6), 1087-1095.

Frisch, U., & Kolmogorov, A. N. (1995). Turbulence: the legacy of AN Kolmogorov. Cambridge University Press.

Alexakis, A., & Biferale, L. (2018). Cascades and transitions in turbulent flows. Phys. Rep., 767, 1-101.

Dong, S., Huang, Y., Yuan, X., & Lozano-Durán, A. (2020). The coherent structure of the kinetic energy transfer in shear turbulence. J. Fluid Mech., 892, A22.

Poje, A. C., Özgökmen, T. M., Bogucki, D. J., & Kirwan, A. D. (2017). Evidence of a forward energy cascade and Kolmogorov self-similarity in submesoscale ocean surface drifter observations. Phys. Fluids, 29(2), 020701.

How to cite: Ma, Y., Hu, J., and Huang, Y.: Turbulent Energy Cascade in the Gulf of Mexico, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7004, https://doi.org/10.5194/egusphere-egu22-7004, 2022.

EGU22-7115 | Presentations | NP0.1

Turbulent Cascade of  the Lithosphere Deformation in the Tibetan Plateau 

Tinghui Yan, Yinxiang Ma, Jianyu Hu, and Yongxiang Huang

Recently, multiscale statics is found to be relevant in description of the lithosphere deformation of the Tibetan Plateau (Jian et al, Phys. Rev. E, 2019). More precisely, a dual-power-law behavior is observed respectively on the spatial scale range of  50≤ r≤ 500km and 500≤ r ≤2000km, which coincidently agrees well with the one reported for the atmospheric movement (Nastrom et al., Nature, 1984). The corresponding high-order scaling exponents demonstrated a nonlinear shape, showing multifractality nature of the underlying dynamics. To diagnose further whether the lithosphere deformation is turbulent or not, the third-order longitudinal structure-function SLLL(r)=< ΔuL(r)3> is estimated, where r is the modulus of the distance vector  r, and  ΔuL is the velocity component that paralleling with r.  Due to the finite sample size, the experimental SLLL(r) is not reliable when r≤200km. The measured SLLL(r) is scaled as  -r4±0.2 on the spatial scale range of 500≤ r ≤ 2000km, indicating the existence of a turbulent cascade. Because of the complexity of the geodynamics, e.g., Coriolis force, mantle convection, India-Eurasia collision, to list a few, the exact force balance is remained unknown. Therefore, the full interpretation of the current observation is not feasible.

 

Ref.

A. Alexakis, &  L. Biferale (2018). Cascades and transitions in turbulent flows, Phys. Rep., 767, 1-101.

U. Frisch, (1995) Turbulence: The Legacy of A.N. Kolmogorov, Cambridge University Press

X. Jian, W. Zhang, Q. Deng & Y.X. Huang (2019) Turbulent lithosphere deformation in the Tibetan Plateau, Phys. Rev. E, 99:062122

G.D. Nastrom, K.S Gage & Jasperson (1984) Kinetic energy spectrum of large- and mesoscale atmospheric processes, Nature, 310:36

How to cite: Yan, T., Ma, Y., Hu, J., and Huang, Y.: Turbulent Cascade of  the Lithosphere Deformation in the Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7115, https://doi.org/10.5194/egusphere-egu22-7115, 2022.

EGU22-7557 | Presentations | NP0.1

Upscale and forward transfer of kinetic energy: Impact on giant planetary jet and vortex formation 

Vincent Böning, Paula Wulff, Wieland Dietrich, Ulrich R. Christensen, and Johannes Wicht

In this study, we analyse the non-linear transfer of kinetic energy in simulations of convection in a 3D rotating shell. Our aim is to understand the role of upscale transfer of kinetic energy and a potential inverse cascade for the formation of zonal jets and large vortices on the giant planets Jupiter and Saturn. We find that the main driving of the jets is associated with upscale transfer directly from the convection scale to the jets. This transfer of energy is mediated by Reynolds stresses, i.e. statistical correlations of velocity components of the small-scale flow.  Intermediate scales are mostly not involved, therefore strictly speaking the jets are not powered by an inverse energy cascade. To a much smaller degree, energy is transferred upscale from the convective scale to large vortices. However, these vortices also receive energy from the jets, likely due to an instability of the jet flow.  Concerning transport in the forward direction, we find as expected that the 3D convective motions transfer energy to the even smaller dissipation scales in a forward cascade.

How to cite: Böning, V., Wulff, P., Dietrich, W., Christensen, U. R., and Wicht, J.: Upscale and forward transfer of kinetic energy: Impact on giant planetary jet and vortex formation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7557, https://doi.org/10.5194/egusphere-egu22-7557, 2022.

EGU22-8277 | Presentations | NP0.1

Scale-to-Scale Energy and Enstrophy Fluxes of Atmospheric Motions via CFOSAT 

Yang Gao, Francois G. Schmitt, Jianyu Hu, and Yongxiang Huang

Turbulence theory essentially describes energy and enstrophy flows crossing scales or a balance between input and output. A famous example is the Richardson-Kolmogorov forward energy cascade picture for three-dimensional homogeneous and isotropic turbulence. However, due to the complexity of turbulent systems, and the lack of an efficient method to describe the cascade quantitatively, the factual cascade features for most fluids are still unknown. In this work, an improved Filter-Space-Technique (FST) is proposed to extract the energy flux ΠE, and enstrophy flux ΠΩ between different scales for the ocean surface wind field which was remotely sensed by the China-France Oceanography Satellite (CFOSAT). With the improved FST method, ΠE and ΠΩ can be calculated for databases which contain gaps or with irregular boundary conditions. Moreover, the local information of the fluxes are preserved. A case study of the typhoon Maysak (2020) shows both inverse and forward cascades for the energy and enstrophy around the center of the typhoon, indicating a rich dynamical pattern. The global views of ΠE and ΠΩ for the wind field are studied for scales from 12.5 to 500 km. The results show that both ΠE and ΠΩ are hemispherically symmetric, with evident spatial and temporal variations for all the scales. More precisely, positive and negative ΠE  are found for the scales less and above 60 km, respectively. As for ΠΩ, the transition scale is around 150 km, forward and backward cascades are corresponding to the scales below and above this scale. In the physical space, stronger fluxes are occurring in midlatitudes than the ones in tropical regions, excepts for a narrow region around 10oN, where strong fluxes are observed. In the temporal space, the fluxes in winter are stronger than the ones in summer. Our study provides an improved approach to derive the local energy and enstrophy fluxes with complex field observed data. The results presented in this work contribute to the fundamental understanding of ocean surface atmospheric motions in their multiscale dynamics, and also provide a benchmark for atmospheric models.

 

Ref. 

Alexakis, A., & Biferale, L. (2018). Cascades and transitions in turbulent flows. Phys. Rep., 767, 1-101.

Dong, S., Huang, Y.X., Yuan, X., Lozano-Durán, A. (2020). The coherent structure of the kinetic energy transfer in shear turbulence. J. Fluid Mech., 892, A22.

Frisch, U., Kolmogorov, A. N. (1995). Turbulence: the legacy of AN Kolmogorov. Cambridge University Press.

Gao, Y. , Schmitt, F.G., Hu,  J.Y. &  Huang, Y.X. (2021) Scaling analysis of the China France Oceanography Satellite along-track wind and wave data. J. Geophys. Res. Oceans, 126:e2020JC017119

 

How to cite: Gao, Y., Schmitt, F. G., Hu, J., and Huang, Y.: Scale-to-Scale Energy and Enstrophy Fluxes of Atmospheric Motions via CFOSAT, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8277, https://doi.org/10.5194/egusphere-egu22-8277, 2022.

EGU22-8564 | Presentations | NP0.1

Global view of oceanic cascades from the Global Circulation Model 

Jingjing Song, Dan Zhang, Yan Peng, Yang Gao, and Yongxiang Huang

In his seminal work "Weather Prediction by Numerical Process" in 1922, Lewis Fry Richardson proposed the famous cascade picture qualitatively for a turbulent flow that energy transferring from large to small scale  structures, until the viscosity one where the kinetic energy is converted  into heat. This picture has been recognized further as the forward energy  cascade.  But, it cannot be applied directly to the real atmospheric  or oceanic motions. Whatever, the global circulation model is indeed established within this framework by considering more complex situations, e.g., earth rotation, stratification, tide, mesoscale eddies, to list a few. In  this work, an improved Filter-Space-Technique (FST) is applied to a reanalysis product provided by the CMEMS global ocean eddy-resolving (1/12o degree horizontal resolution).   The FST provides a global view of the  energy flux ΠE  that associated with the oceanic cascades for all resolved  scales, e.g., from mesoscale eddies to global circulations. For instance, at scale r=160 km (i.e., radius of the Gaussian filter kernel), a rich dynamic pattern is observed for an instantaneous flow filed. Both forward (ΠE>0, energy transferring from large scale to small scale structures) and inverse (ΠE<0, energy transferring from small scale to large scale structures) cascades are evident in the equator, western boundary current regions, Antarctic Circumpolar Current region, to name a few. While, the long-term averaged flux field show mainly a negative ΠE (inverse energy cascade) except for the equatorial region. Moreover, a high intensity negative flux is found for both the Loop Current and Kuroshio Current, indicating that the mesoscale eddies might be absorbed by the main flow.

 

Ref.

Charney, J. G. (1971). Geostrophic turbulence. J. Atmos. Sci., 28(6), 1087-1095.

Frisch, U.,  Kolmogorov, A. N. (1995). Turbulence: the legacy of AN Kolmogorov. Cambridge University Press.

Alexakis, A.,  Biferale, L. (2018). Cascades and transitions in turbulent flows. Phys. Rep., 767, 1-101.

Dong, S., Huang, Y.X., Yuan, X., & Lozano-Durán, A. (2020). The coherent structure of the kinetic energy transfer in shear turbulence. J. Fluid Mech., 892, A22.

How to cite: Song, J., Zhang, D., Peng, Y., Gao, Y., and Huang, Y.: Global view of oceanic cascades from the Global Circulation Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8564, https://doi.org/10.5194/egusphere-egu22-8564, 2022.

Big whirls have little whirls that feed on their velocity,

and little whirls have lesser whirls and so on to viscosity.

These famous words written in 1922 by Lewis Fry Richardson have become inspiration for intensively developing scientific field studying scales of climate variability and their interactions. In spite of ever growing interest in this research area, the description of this session states: ”We still lack an efficient methodology to diagnose the scale-to-scale energy or other physical quantities fluxes to characterize the cascade quantitatively, e.g., strength, direction, etc. ”  In this contribution we would like to remind the methodology able to identify causal relations and information transfer between dynamical processes on different time scales and even to quantify the effect of such causal influences. Moreover, in macroscopic systems the information transfer is tied to the transfer of mass and energy [1].

The detection of cross-scale causal interactions [2] starts with a wavelet (or other scale-wise) decomposition of a multi-scale signal into quasi-oscillatory modes of a limited bandwidth, described using their instantaneous phases and amplitudes. Then their statistical associations are tested in order to search interactions across time scales. An information-theoretic formulation of the generalized, nonlinear Granger causality [3] uncovers causal influence and information transfer from large-scale modes of climate variability, characterized by time scales from years to almost a decade, to regional temperature variability on short time scales.  In particular, a climate oscillation with the period around 7-8 years has been identified as a factor influencing variability of surface air temperature (SAT) on shorter time scales.  Its influence on the amplitude of the SAT annual cycle was estimated in the range 0.7-1.4 °C, while its strongest effect was observed in the interannual variability of the winter SAT anomaly means where it reaches 4-5 °C in central European stations and reanalysis data [4].  In the dynamics of El Niño-Southern Oscillation (ENSO), three principal time scales - the annual cycle (AC), the quasibiennial (QB) mode(s) and the low-frequency (LF) variability – and their causal network have been identified [5]. Recent results show how the phases of ENSO QB and LF oscillations influence amplitudes of precipitation variability in east Asia in the annual and QB scales.

Support from the Czech Science Foundation (GA19-16066S) and the Czech Academy of Sciences (Praemium Academiae) is gratefully acknowledged.

[1] J. Hlinka et al., Chaos 27(3), 035811 (2017)

[2] M. Palus, Phys. Rev. Lett. 112, 078702 (2014)

[3] M. Palus, M. Vejmelka, Phys. Rev. E 75, 056211  (2007)

[4] N. Jajcay, J. Hlinka, S. Kravtsov, A. A. Tsonis, M. Palus, Geophys. Res. Lett. 43(2), 902–909 (2016)

[5] N. Jajcay, S. Kravtsov, G. Sugihara, A. A. Tsonis, and M. Palus, npj Climate and Atmospheric Science 1, 33 (2018).  doi:10.1038/s41612-018-0043-7, https://www.nature.com/articles/s41612-018-0043-7

How to cite: Palus, M.: Big whirls talking to smaller whirls: detecting cross-scale information flow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9028, https://doi.org/10.5194/egusphere-egu22-9028, 2022.

EGU22-9226 | Presentations | NP0.1

Study of Submesoscale Coherent Vortices (SCVs) in the Atlantic Ocean along different isopycnals 

Ashwita Chouksey, Xavier Carton, and Jonathan Gula

The ocean is densely populated with energetic coherent vortices of different sizes. Mesoscale and submesoscale vortices contribute to stirring of the ocean, transporting and redistributing water masses and tracers (active and passive), affecting ventilation pathways and thus impacting the large-scale circulation. Submesoscale Coherent Vortices (SCVs), i.e. vortices with radii between 1-30 km have been detected via satellite and in-situ measurements at surface or at depth (usually not more than ~2000 m depth). They are found to be of different shapes and sizes depending upon latitude and place of origin. Previous studies mostly describe the surface mesoscale and submesoscale eddies rather than the deep SCVs (> 2000 m). This study focuses on SCVs below the mixed layer along four different isopycnal surfaces: 26.60, 27.60, 27.80, and 27.86, which lie in the depth range of 10-500 m, 200-2000 m, 1200-3000 m, and 1800-4500 m, respectively. We aim to quantify their physical characteristics (radius, thickness, bias in polarity: cyclones versus anticyclones) in different parts of the Atlantic ocean, and analyze the dynamics involved in the generation and destruction of the SCVs throughout their life-cycle. We use the Coastal and Regional Ocean COmmunity model (CROCO) ocean model in a high resolution setup (3 km) of the Atlantic Ocean. The detection of SCVs are done every 12 hr using the Okubo-Weiss parameter along the isopycnal surfaces using the eddy-tracking algorithm by Mason et al., 2014. We consider only structures living for more than 21 days. The census of SCVs shows that there are in total more cyclonic than anticyclonic SCV detections. However cyclones are on average smaller and shorter lived, such that there is a dominance of anticyclones while considering long-lived and larger distance travelling SCVs. We concentrate on the strongest and longest lived SCVs among which meddies that we compare to previous in-situ observations. This study is the first step in the understanding of the formation, occurrences and structure of SCVs in the Atlantic Ocean, and their impact on the large-scale ocean circulation.

How to cite: Chouksey, A., Carton, X., and Gula, J.: Study of Submesoscale Coherent Vortices (SCVs) in the Atlantic Ocean along different isopycnals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9226, https://doi.org/10.5194/egusphere-egu22-9226, 2022.

In recent years a consensus has been reached regarding the direction of the energy cascade in the mesoscales in the Upper Tropospheric-Lower Stratospheric (UTLS) altitudes. Numerous measurements and model results confirm the existence of a predominantly forward spectral energy flux from low to high horizontal wavenumbers. However, the details to explain the observed -5/3 power law for Kinetic and Available Potential Energy (KE and APE) are still being debated.

In this study we performed simulations using the dry version of the Kühlungsborn Mechanistic general Circulation Model (KMCM) with high horizontal and vertical resolution for permanent January conditions. Horizontal diffusion schemes for horizontal momentum and sensible heat satisfy the Scale Invariance Criterion (SIC) using the Dynamic Smagorinsky Model (DSM). We investigated the simulated KE and APE spectra with regard to the scaling laws of Stratified Macro-Turbulence (SMT). Zonally and temporally averaged dissipation rates for KE & APE and SMT statistics correlate highly in subtropical mid-latitudes and the UTLS levels. Particularly the characteristic dimensionless numbers of Buoyancy Reynolds Number and turbulent-Rossby Number are pronounced in the regions, where the maximum of the forward spectral fluxes of nonlinear interactions are also found. During this process the spectral contribution of the negative buoyancy production term plays an important role by converting KE to APE. These findings are entirely in line with the spectral and statistical predictions of idealized Stratified Turbulence (ST) and confirms that the energy cascades that give rise to the simulated mesoscale shallowing are strongly nonlinear.

Furthermore level by level analyses of the horizontally averaged spectral tendencies and fluxes of both KE and APE reservoirs in this specific region revealed that there is a non-negligible spectral contribution by the energy deposition term of upward propagating Gravity Waves (GW). Further investigation indicate the dynamics of these resolved GWs look like a superposition of westward Inertia GWs that are subject to a Lindzen-type saturation condition. Their vertical propagation in UTLS heights is non-conservative above their generation level. These results associate directly for the first time ST and GW dynamics, which were thought to be distinct in character. Finally we present simulations with different diffusion schemes and show that the previously mentioned energy deposition contribution was only identified if both horizontal momentum and sensible heat diffusion schemes fulfill the SIC.

How to cite: Can, S.: Macro-Turbulent Energy Cascades in UpperTropospheric-Lower Stratospheric Mesoscales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9270, https://doi.org/10.5194/egusphere-egu22-9270, 2022.

EGU22-9329 | Presentations | NP0.1

Mesoscale Eddy Kinetic Energy budgets and transfers between vertical modes in the Agulhas Current 

Pauline Tedesco, Jonathan Gula, Pierrick Penven, and Claire Ménesguen

Western boundary currents are hotspots of the mesoscale oceanic variability and of energy transfers, channeled by topography, toward smaller scales and eventually down to dissipation. Here, we assess the main mesoscale eddies energy sinks in the Agulhas Current region, with an emphasize on the different paths of energy toward smaller scales, from a regional numerical simulation. 

We derive an eddy kinetic energy (EKE) budget in the framework of the vertical modes. This comprehensive method accounts for energy transfers between energy reservoirs and vertical modes, including transfers channeled by topography and by a turbulent vertical cascade. 

The variability is dominated by mesoscale eddies (barotropic and 1st baroclinic modes) in the path of intense mean currents. Eddy-topography interactions result in a major mesoscale eddy energy sink (50 % of the total EKE sink). They represent energy transfers both toward higher baroclinic modes (27 % of the total EKE sink) and mean currents (23 % of the total EKE sink). Energy transfers toward higher baroclinic modes take different forms in the Northern Agulhas Current, where it corresponds to non-linear transfers to smaller vertical eddies on the slope (5 % of the total EKE sink), and in the Southern Agulhas Current, where it is dominated by a (linear) generation of internal-gravity waves over topography (22 % of the total EKE sink). The vertical turbulent cascade is significant in offshore regions, away from topography and intense mean currents. In these regions the direction of the turbulent vertical cascade is inverse - energy transferred from higher baroclinic modes toward mesoscale eddies - and it can locally amounts for most of the mesoscale eddies energy gain (up to 68 % of the local EKE source).

However, the Agulhas Current region remains a net source of mesoscale eddy energy due to the strong generation of eddies, modulated by the topography, especially in the Southern Agulhas Current. In the complex Agulhas Current system, which includes an intense mean oceanic current and mesoscale eddies field as well as strong topographic constraint and stratification gradients, the local generation of mesoscale eddies dominates the net EKE budget. It is in contrast with the paradigm of mesoscale eddies decay upon western boundaries, suggested as being due to topographically-channeled interactions triggering a direct energy cascade.

How to cite: Tedesco, P., Gula, J., Penven, P., and Ménesguen, C.: Mesoscale Eddy Kinetic Energy budgets and transfers between vertical modes in the Agulhas Current, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9329, https://doi.org/10.5194/egusphere-egu22-9329, 2022.

EGU22-13450 | Presentations | NP0.1

Relative Dispersion with Finite Inertial Ranges 

Joe LaCasce and Thomas Meunier

The relative dispersion of pairs of particles was first considered in a seminal article by Richardson (1926). The dispersion subsequently was subsequently linked to turbulence, and pair separation statistics can advantageously be used to deduce energy wavenumber spectra. Thus one can, for example, employ surface drifters to identify turbulent regimes at scales well below those resolved by satellite altimetry. The identification relies on knowing how dispersion evolves with a specific energy spectrum. The analytical predictions commonly used apply to infinite inertial ranges, i.e. assuming the same dispersive behavior over all scales. With finite inertial ranges, the metrics are less conclusive, and often are not even consistent with each other.

We examine this using pair separation probability density functions (PDFs), obtained by integrating a Fokker-Planck equation with different diffusivity profiles. We consider time-based metrics, such as the relative dispersion, and separation-based metrics, such as the finite scale Lyapunov exponent (FSLE). As the latter cannot be calculated from a PDF, we introduce a new measure, the Cumulative Inverse Separation Time (CIST), which can. This behaves like the FSLE, but advantageously has analytical solutions in the inertial ranges. This allows establishing consistency between the time- and space-based metrics, something which has been lacking previously.

We focus on three dispersion regimes: non-local spreading (as in a 2D enstrophy inertial range), Richardson dispersion (as in the 3D and 2D energy inertial ranges) and diffusion (for uncorrelated pair motion). The time-based metrics are more successful with non-local dispersion, as the corresponding PDF applies from the initial time. Richardson dispersion is barely observed, because the self-similar PDF applies only asymptotically in time. In contrast, the separation-based CIST correctly captures the dependencies, even with a short (one decade) inertial range, and is superior to the traditional FSLE at large scales. Furthermore, the analytical solutions permit reconciling the CIST with the other measures, something which is generally not possible with the FSLE.

How to cite: LaCasce, J. and Meunier, T.: Relative Dispersion with Finite Inertial Ranges, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13450, https://doi.org/10.5194/egusphere-egu22-13450, 2022.

EGU22-8191 | Presentations | ST3.2

Sources of variability in the ionospheric spatio/temporal scales measured by Swarm instrument suite 

Jaroslav Urbar, Luca Spogli, Antonio Cicone, Lasse Clausen, Yaqi Jin, Alan Wood, Lucilla Alfonsi, Claudio Cesaroni, James Rawlings, Daria Kotova, Per Høeg, and Wojciech Miloch

The ionosphere is a dynamical system exhibiting nonlinear couplings with the other “spheres” characterizing the geospace environment. Such nonlinearity manifests also through the non-trivial, largely varying range of spatial and temporal scales. We investigate how the different scales of the in situ plasma density as provided by different data products measured by Swarm satellites relate to the same range of scales of the field-aligned currents from Swarm FAC dataset and how their intensifications reflect the various conditions of the geospace.

The present study compares the spatio-temporal variability in the topside ionosphere by leveraging on the Fast Iterative Filtering (FIF) technique. FIF is able to  reveal the hidden features of a time series, as it decomposes any nonstationary, nonlinear signals, like those provided by Langmuir probes onboard Swarm, into oscillating modes, called intrinsic mode components or functions (IMCs or IMFs), characterized by their specific frequencies. 

The instantaneous time-frequency representation of the IMFs is provided through the so-called “IMFogram” which illustrates the time development of the multi-scale processes. The IMFogram has the potentiality to show the finer details of the scale sizes which intensify during the various phases of geomagnetic storms.

This work is performed in the framework of the Swarm Variability of Ionospheric Plasma (Swarm-VIP) project, funded by ESA in the “Swarm+4D-Ionosphere” framework (ESA Contract No. 4000130562/20/I-DT).

How to cite: Urbar, J., Spogli, L., Cicone, A., Clausen, L., Jin, Y., Wood, A., Alfonsi, L., Cesaroni, C., Rawlings, J., Kotova, D., Høeg, P., and Miloch, W.: Sources of variability in the ionospheric spatio/temporal scales measured by Swarm instrument suite, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8191, https://doi.org/10.5194/egusphere-egu22-8191, 2022.

EGU22-8293 | Presentations | ST3.2

Statistical characteristics of ionospheric irregularities in the cusp ionosphere based on multi-instrument techniques 

Andres Spicher, Juha Vierinen, Kjellmar Oksavik, and Yaqi Jin

Plasma density irregularities disturbing signals from Global Navigation Satellite Systems (GNSS) are known to be regular features of the high-latitude ionosphere, especially around the cusp and auroral regions. Despite their relevance for society, irregularity formation and evolution are still relatively poorly understood, and observations revealing the spatio-temporal characteristics of ionospheric structuring at different scales are needed to assess the exact mechanism(s) responsible for them.

In this study, we focus on data from the European Incoherent Scatter Scientific Association (EISCAT) Svalbard Radars (ESR) operating in fast scanning mode. We use ESR experiments in which the antenna was swept in elevation, and create consecutive two-dimensional images showing how electron density, ion velocity, electron temperature, and ion temperatures change with latitude and time at different altitudes.

We present selected events in which the ESR scans are combined with all-sky images and in-situ data from the Swarm satellites to provide multi-scale observations of cusp phenomena comprising polar cap patches, flow channels, particle precipitation, and ion heating.  We compare the observations with the presence of GNSS scintillations, allowing to monitor the onset and development of irregularities causing scintillations, and to inspect their connection with the phenomena above-mentioned. We then extend the analysis by performing a statistical study using all ESR fast scans identified between January 2001 and December 2015. We investigate the statistical characteristics of the measured parameters at different altitudes and under different geomagnetic conditions. Overall, this study will provide further insights onto the spatio-temporal evolution of ionospheric cusp dynamics, and on the possible physical sources causing ionospheric irregularities with Space weather impacts.

How to cite: Spicher, A., Vierinen, J., Oksavik, K., and Jin, Y.: Statistical characteristics of ionospheric irregularities in the cusp ionosphere based on multi-instrument techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8293, https://doi.org/10.5194/egusphere-egu22-8293, 2022.

EGU22-8954 | Presentations | ST3.2

Direct comparison of sporadic E from COSMIC-2 radio occultation and vertical wind shears from ICON/MIGHTI 

Yosuke Yamazaki, Christina Arras, Satoshi Andoh, Yasunobu Miyoshi, Hiroyuki Shinagawa, Brian J. Harding, Christoph R. Englert, Thomas J. Immel, Sahar Sobhkhiz-Miandehi, and Claudia Stolle

The formation of a sporadic-E (Es) layer at mid and low latitudes is generally attributed to the vertical wind shear, which is predicted to cause vertical ion convergence. According to wind shear theory, a negative shear of the eastward wind is effective in converging metallic ions into a thin layer to produce Es. However, the direct comparison of Es with the local wind shear has been limited due to the lack of neutral wind measurements. This study examines the role of the vertical wind shear for Es, using signal-to-noise ratio profiles from COSMIC-2 radio occultation measurements and concurrent measurements of neutral wind profiles from the Ionospheric Connection Explorer (ICON). We find that the Es occurrence rate is correlated with the negative vertical shear of the eastward wind, providing observational support for the wind shear theory.

How to cite: Yamazaki, Y., Arras, C., Andoh, S., Miyoshi, Y., Shinagawa, H., Harding, B. J., Englert, C. R., Immel, T. J., Sobhkhiz-Miandehi, S., and Stolle, C.: Direct comparison of sporadic E from COSMIC-2 radio occultation and vertical wind shears from ICON/MIGHTI, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8954, https://doi.org/10.5194/egusphere-egu22-8954, 2022.

The global total electron content (TEC) map in 2013, retrieved from the International Global Navigation Satellite Systems (GNSS) Service (IGS), and the International Reference Ionosphere (IRI-2016) model are used to monitor the diurnal evolution of the equatorial ionization anomaly (EIA). The statistics are conducted during geomagnetic quiet periods in the Peruvian and Indian sectors, where the equatorial electrojet (EEJ) data and reliable TEC are available. The EEJ is used as a proxy to determine whether the EIA structure is fully developed. Most of the previous studies focused on the period in which the EIA is well developed, while the period before EIA emergence is usually neglected. To characterize dynamics accounting for the full development of EIA, we defined and statistically analyzed the onset, first emergence, and the peaks of the northern crest and southern crest based on the proposed crest-to-trough difference (CTD) profiles. These time points extracted from IGS TEC show typical annual cycles in the Indian sector which can be summarized as winter hemispheric priority, i.e., the development of EIA in the winter hemisphere is ahead of that in the summer hemisphere. However, these same time points show abnormal semiannual cycles in the Peruvian sector, that is, EIA develops earlier during two equinoxes/solstices in the northern/southern hemisphere. We suggest that the onset of EIA is a consequence of the equilibrium between sunlight ionization and ambipolar diffusion. However, the latter term is not considered in modeling the topside ionosphere in IRI-2016, which results in a poor capacity in IRI to describe the diurnal evolution of EIA. Meridional neutral wind’s modulation on the ambipolar diffusion can explain the annual cycle observed in the Indian sector, while the semiannual variation seen in the Peruvian sector might be due to additional competing effects induced by the F region height changes

How to cite: Wan, X., Zhong, J., Xiong, C., and Liu, Y.: Seasonal and Interhemispheric Effects on the Diurnal Evolution of EIA: Assessed by IGS TEC and IRI-2016 over Peruvian and Indian sectors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9000, https://doi.org/10.5194/egusphere-egu22-9000, 2022.

EGU22-9366 | Presentations | ST3.2

Statistical Study of Decameter Scale Plasma Irregularities in the Polar Ionosphere 

Yaqi Jin, Lasse Clausen, Andres Spicher, Magnus Ivarsen, Yongliang Zhang, Wojciech Miloch, and Joran Moen

The polar ionosphere is often highly irregular and turbulent with significant plasma structures. As a result, the satellite-based navigation and communication systems that rely on trans-ionospheric radio signals can be severely disrupted. In this study, we take advantage of the high-resolution (1 kHz) electron density observations of a polar orbiting satellite (NorSat-1) to address plasma structures at several 10s of meters that are responsible for scattering of High Frequency (HF) radar signals. The in-situ electron density data are taken from the winter season of 2017-2018. Though the solar activity is very low, NorSat-1 frequently observes significant plasma irregularities from several 10s km down to several decameter. These are often observed near the dayside cusp and dawnside auroral zone. The decameter-scale irregularities are positively correlated with intermediate-scale (10 km) density gradients, for both negative and positive gradients encountered by the satellite. The spatial distribution of electron density over two winter months in the Northern hemisphere along NorSat-1 orbits is constructed, which shows significant density increases in the cusp ionosphere (75º-80º MLAT) and in regions near the dawnside auroral oval. Intermediate scale density gradients and small-scale irregularities are clearly collocated with these density enhancements. These density enhancements and irregularities are likely induced by auroral particle precipitation/plasma dynamics. The power of decameter scale irregularities is also directly compared with the backscatter echo of HF radars.

How to cite: Jin, Y., Clausen, L., Spicher, A., Ivarsen, M., Zhang, Y., Miloch, W., and Moen, J.: Statistical Study of Decameter Scale Plasma Irregularities in the Polar Ionosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9366, https://doi.org/10.5194/egusphere-egu22-9366, 2022.

EGU22-10099 | Presentations | ST3.2

Ionospheric Turbulence and the Equatorial Plasma Density Irregularities: Scaling Features and RODI 

Paola De Michelis, Tommaso Alberti, Igino Coco, Giuseppe Consolini, Fabio Giannattasio, Michael Pezzopane, Alessio Pignalberi, and Roberta Tozzi

In the framework of space weather, the understanding of the physical mechanisms responsible for the generation of ionospheric irregularities is particularly relevant for their effects on global positioning and communication systems. Ionospheric equatorial plasma bubbles are one of the possible irregularities. Using data from the ESA’s Swarm mission, we investigate the scaling features of electron density fluctuations characterizing equatorial plasma bubbles. Results strongly support the turbulent character of these structures and suggest the existence of a clear link between the observed scaling properties and the value of the Rate Of change of electron Density Index (RODI).

In addition, considering that important features of plasma bubbles such as their dependence on latitude, longitude, solar and geomagnetic activities have been inferred indirectly using their magnetic signatures, we study also the scaling properties of the magnetic field inside them. We show that the spectral features of plasma irregularities cannot be directly inferred from their magnetic signatures. A relation more complex than the linear one is necessary to properly describe the role played by the evolution of plasma bubbles with local time and by the development of turbulent phenomena. A better comprehension of the plasma bubbles dynamics and of the turbulence processes that characterize their time evolution may benefit from the use of very high-resolution vector magnetic field and plasma density measurements such as those available from the future NanoMagSat mission.

 

How to cite: De Michelis, P., Alberti, T., Coco, I., Consolini, G., Giannattasio, F., Pezzopane, M., Pignalberi, A., and Tozzi, R.: Ionospheric Turbulence and the Equatorial Plasma Density Irregularities: Scaling Features and RODI, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10099, https://doi.org/10.5194/egusphere-egu22-10099, 2022.

EGU22-10326 | Presentations | ST3.2

Altitude distribution of large and small-scale equatorial ionospheric irregularities sampled by the Swarm Echo satellite 

Ali Mohandesi, David J. Knudsen, Susan Skone, Richard B. Langley, and Andrew W. Yau

Variations in ionospheric electron density, so-called irregularities, produce rapid fluctuations on propagating communication and navigation signals, which can be severe near the magnetic equator and in the polar regions. This may result in positioning error. Due to sparse sampling, our knowledge of the vertical distribution of small-scale irregularities is limited. In this study, we examine the vertical distribution of multi-scale scintillation-inducing irregularities in the low-latitude ionosphere. In four sets of novel experiments, we sampled altitudes from 330-1280 km in the 18-24 MLT sector using the Swarm Echo GAP-O GPS receiver with its antenna oriented toward zenith. In order to identify multi-scale irregularities both above and at the satellite’s position, we utilize high-sample-rate GAP-O amplitude and phase measurements along with a measurement of net current onto the surface of the IRM sensor on board, which serves as a proxy for density variations. We find that amplitude scintillations on the GPS signal coincide with strong in-situ small-scale density irregularities in 74% of cases, and above 500 km of altitude in all but one instance. In addition, we show that large-scale ionospheric disturbances occur predominantly below 500 km, and down to the 330 km perigee of Swarm Echo in the 18-21 MLT sector. In contrast, small-scale variations on total electron content (TEC) are detected at all MLTs between 18 MLT and magnetic midnight and at all altitudes sampled in this experiment. However, they are more frequent in the 22-24 MLT range.

How to cite: Mohandesi, A., Knudsen, D. J., Skone, S., Langley, R. B., and Yau, A. W.: Altitude distribution of large and small-scale equatorial ionospheric irregularities sampled by the Swarm Echo satellite, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10326, https://doi.org/10.5194/egusphere-egu22-10326, 2022.

EGU22-11014 | Presentations | ST3.2

Diagnose the diffractive contribution to GNSS scintillation at high latitude during the geomagnetic storm on 7-8 September 2017 

Chao Xiong, Yuhao Zheng, Yaqi Jin, Dun Liu, Chunyu Xu, Yixun Zhu, and Kjellmar OKsavik

The ionospheric plasma irregularities can cause severe scintillation of the trans-ionospheric radio waves, e.g., signals from the global navigation satellite system (GNSS). The phase scintillation of GNSS signal are usually caused by both refractive and diffractive variations, while the amplitude scintillation is mainly attributed to diffractive process. At high latitude, the GNSS signals usually exhibit strong phase scintillation, but the meanwhile amplitude scintillation is very low. Such a feature leads to the commonly known issue as “phase without amplitude scintillation at high latitude”. In this study, we focused on the geomagnetic storm happened on 7-8 September 2017. High-resolution data from four GNSS receivers at high latitudes were utilized. Quite intense phase and amplitude scintillations, represented by σ4 and S4, respectively, were observed during the storm mainly phase. By checking the ionosphere-free linear combination (IFLC) parameter, the intense phase and amplitude scintillations are found associated with diffractive effects. Simultaneous observations from the Swarm satellite have been further analyzed to resolve the possible reasons that cause the diffractive influence of scintillation. 

How to cite: Xiong, C., Zheng, Y., Jin, Y., Liu, D., Xu, C., Zhu, Y., and OKsavik, K.: Diagnose the diffractive contribution to GNSS scintillation at high latitude during the geomagnetic storm on 7-8 September 2017, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11014, https://doi.org/10.5194/egusphere-egu22-11014, 2022.

EGU22-11044 | Presentations | ST3.2

Climatological distributions of mid-latitude trough region irregularities based on Swarm in situ measurements 

Yiwen Liu, Wenhao Xie, Chao Xiong, Ting Ye, Yuhao Wang, Xin Wan, and Yueyan Cao

A large number of studies have confirmed the frequent occurrence of plasma irregularities in the mid-latitude ionospheric trough (MIT), but their distribution characteristics have not been fully understood. Based on the Swarm in situ plasma density measurements from 2014 to 2020, the diurnal, seasonal, solar activity and geomagnetic activity variations of the occurrence rate of MIT region irregularities are analyzed. The results show that for the irregularities with scale size of 7.5-75 km: (1) the geomagnetic activity has an obvious inhibitory effect on the formation of irregularities inside the MIT region, regardless of dayside or nightside. (2) The occurrence rate of irregularities inside MIT region during the day is significantly higher than that at night, and the difference between day and night is greater than the difference between the two walls at the same local time sector. (3) On the dayside, the highest and lowest occurrence rate appears in winter and summer, respectively; but on the nightside, the highest and lowest occurrence rate appears in equinoxes and winter, respectively. (4) On the nightside, it shows lower occurrence rate under high solar activity conditions, but no obvious solar activity effect is shown on the dayside occurrence rate. The above results of the seasonal dependence, geomagnetic activity inhibitory effect, and solar activity influnce are newly and important for understanding the behaviors of the plasma irregularities at MIT region.

How to cite: Liu, Y., Xie, W., Xiong, C., Ye, T., Wang, Y., Wan, X., and Cao, Y.: Climatological distributions of mid-latitude trough region irregularities based on Swarm in situ measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11044, https://doi.org/10.5194/egusphere-egu22-11044, 2022.

EGU22-11426 | Presentations | ST3.2

Plasma transport across high latitudes 

Dimitry Pokhotelov, Isabel Fernadez-Gomez, and Claudia Borries

Plasma anomalies appear at high latitudes, extending across the polar cap as a tongue of ionisation and/or polar patches. Physical mechanisms responsible for plasma uplifts and transport are investigated using global ionospheric circulation models driven by parameterised high-latitude plasma convection models. Various convection models will be considered, including the models based on satellite data, SuperDARN radar data, and data assimilation models. Relative contributions from electrodynamic plasma transport and neutral wind forcing are assessed. The simulations are compared with GNSS and radar observations. The results are discussed in the context of space weather modelling and scintillation environment modelling at high latitudes.

How to cite: Pokhotelov, D., Fernadez-Gomez, I., and Borries, C.: Plasma transport across high latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11426, https://doi.org/10.5194/egusphere-egu22-11426, 2022.

EGU22-11690 | Presentations | ST3.2

Spectral Properties of Kilometer-scale Equatorial Irregularities as Seen by theSwarm Satellites 

Stephan Buchert, Sharon Aol, Edward Jurua, and Luca Sorriso-Valvo

The ESA Swarm satellites have since year 2014 provided measurements of electron density at a frequency of 2 Hz and at times also 16 Hz corresponding to about 500 m along the satellite paths. The spectral characteristics of these 16 Hz density estimates were analyzed to study the F-region ionospheric
irregularities at altitudes between about 440 and 510 km. The data were obtained during the period from October 2014 to October 2018. The Power
Spectral Densities (PSDs) observed followed to a very good approximation a power law. The values of spectral indices obtained showed a peak centered at around -2.5, located at the Equatorial Ionization Anomaly (EIA) belts. The spectral indices were found to be sensitive to the amplitudes of the irregular
variations. Most spectra were obtained  within the time sector 20:00 LT - 22:00 LT, and they became slightly shallower towards later local times. The largest contribution to the spectra came from in the South American-Antlantic-African longitudes and it was generally low in the Asian-Pacific region. The angle between the Swarm satellite orbital path and the magnetic field (∠(B, v)) was examined. The highest percentage of occurrence of ionospheric irregularities and the peak in spectral index was obtained for ∠(B, v) between 20° and 40°. Over this range of angles PSD spectra steepened with increasing ∠(B, v) (p becomes increasingly negative), consistent with local anisotropic turbulence at scales of a few km.

How to cite: Buchert, S., Aol, S., Jurua, E., and Sorriso-Valvo, L.: Spectral Properties of Kilometer-scale Equatorial Irregularities as Seen by theSwarm Satellites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11690, https://doi.org/10.5194/egusphere-egu22-11690, 2022.

To provide new insights into the relationship between geomagnetic conditions and plasma irregularity scale-sizes, high-latitude irregularity spectra are developed using a novel Incoherent Scatter Radar (ISR) technique. This new technique leverages: 1) the ability of phased array Advanced Modular ISR (AMISR) technology to collect volumetric measurements of plasma density, 2) the slow F-region cross-field plasma diffusion at scales greater than 10 km, and 3) that high-latitude geomagnetic field lines are nearly vertical. The resulting irregularity spectra are of a higher spatial-temporal resolution than has been previously possible with ISRs, capable of resolving approximately 20 km structures in less than two minutes (depending on the radar mode). By comparing irregularity spectra from high-latitude Resolute Bay ISR data to solar and magnetospheric conditions, we have found that although structures 100s of km wide can be prevalent for a variety of geomagnetic conditions, polar cap structures 10s of km will become more prevalent during quiet geomagnetic conditions. Furthermore, structures that are 10s of km wide will also become more dominant near midnight, reflecting the role of polar cap convection in breaking down structures as they travel from the dayside ionosphere to the nightside. This presentation will expand on these and other findings, as well as discuss the future goals of this work.

How to cite: Goodwin, L. and Perry, G.: The Impact of Solar and Magnetospheric Conditions on High-Latitude Irregularity Spatial-Scales as Observed Using Advanced Radar Techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11882, https://doi.org/10.5194/egusphere-egu22-11882, 2022.

EGU22-12957 | Presentations | ST3.2

LOFAR ionospheric scintillation spectral measurements in mid-latitude region 

Mariusz Pożoga, Helena Ciechowska, Barbara Matyjasiak, Marcin Grzesiak, Hanna Rothkaehl, Roman Wronowski, Łukasz Tomasik, and Katarzyna Beser

Due to its small intensity, ionospheric scintillation at the mid-latitudes is difficult to observe. The measurements of signal amplitude scintillation from GNSS in this region are almost impossible to perform with sufficient quality. 
The European interferometer LOFAR observing in the frequency range 10-90 MHz, provides a good opportunity to carry out complex studies on the ionospheric scintillation in the mid-latitudes. 
In this work, we show statistical analysis of amplitude scintillation intensity described by the S4 index as well as spectral parameters given from specially designed pipelines dedicated to computing and analyzing spectra obtained with a single LOFAR station and ILT observation. We also show temporal and spatial statistics for spectral index, Fresnel frequency, and noise level of measurement.

How to cite: Pożoga, M., Ciechowska, H., Matyjasiak, B., Grzesiak, M., Rothkaehl, H., Wronowski, R., Tomasik, Ł., and Beser, K.: LOFAR ionospheric scintillation spectral measurements in mid-latitude region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12957, https://doi.org/10.5194/egusphere-egu22-12957, 2022.

EGU22-453 | Presentations | ST3.4

Investigation of Ionospheric and Ground Level Signatures of Geomagnetic Storms over Turkey 

Ezgi Gülay, Zerefşan Kaymaz, and Emine Ceren Kalafatoğlu Eyigüler

We study the ionospheric and ground signatures of geomagnetic activity over Marmara region in Turkey. In our study, we use ionospheric electron density measurements using Dynasonde measured in ITU Campus, Istanbul (41°N, 29°E), magnetic field measurements in İznik (40.43oN, 29.72oE) and magnetotelluric measurements of magnetic field and electric field in Bozcaada (37.5°N, 106°E). Combined measurements are utilized in search of the geomagnetically induced currents (GICs) and their connection to ionospheric variations for the selected geomagnetic storms. Variations in dB/dt which are used to refer to the GICs are determined and quantified. Accompanying variations in electron density and electric field will be revealed and the deviations from the quiet day will be presented. Although strong GICs are mostly reported to exist over high latitudes, depicted based on the dB/dt variations, we show that they are also present over mid-latitudes where Turkey is located at. At the meeting, we will present our first results based on our measurements and discuss the physical causes of the variations observed.

How to cite: Gülay, E., Kaymaz, Z., and Kalafatoğlu Eyigüler, E. C.: Investigation of Ionospheric and Ground Level Signatures of Geomagnetic Storms over Turkey, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-453, https://doi.org/10.5194/egusphere-egu22-453, 2022.

EGU22-481 | Presentations | ST3.4

Dependence of Joule heating on the ICME parameters 

Pelin Erdemir, Zerefsan Kaymaz, Emine Ceren Kalafatoglu Eyiguler, and Lutz Rastaetter

Ionospheric Joule heating occurs as a result of the geomagnetic storms which are driven by ICMEs in the solar wind.  High speed ICMEs and the strong and enduring southward IMFs are the key parameters in occurrence of the geomagnetic storms.  In this study, we investigate the dependence of the Joule heating on the ICME parameters. We obtained Joule heating using SWMF-BATSRUS MHD model for the selected geomagnetic storms.  ICME magnetic field and plasma parameters that cause these storms were sorted and the threshold levels for each ICME parameter were determined in order to find the most influential parameter that controls the Joule heating.   A clear separation exists in the Joule heating that corresponds to the sheath and magnetic cloud regions of the ICME.  Our preliminary results indicate that the Joule heating higher than 600 GW occurs when the southward IMF Bz last more than a day within the magnetic cloud arrives at the Earth despite the corresponding speed and the density, thus the pressure, are lower. While the velocity is higher, the fact that the density is much lower within the cloud results in lower Joule heating.  In this presentation, three cases will be compared and discussed in order to advance our understanding on the solar wind-magnetosphere-ionosphere coupling.

How to cite: Erdemir, P., Kaymaz, Z., Kalafatoglu Eyiguler, E. C., and Rastaetter, L.: Dependence of Joule heating on the ICME parameters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-481, https://doi.org/10.5194/egusphere-egu22-481, 2022.

EGU22-1322 | Presentations | ST3.4

Determining latitudinal extent of energetic electron precipitation  using MEPED on-board NOAA POES 

Eldho Midhun Babu, Hilde Nesse Tyssøy, Christine Smith-Johnsen, Ville Maliniemi, Josephine Alessandra Salice, and Robyn Millan

Energetic Electron Precipitation (EEP) from the plasma sheet and the radiation belts ionize the polar lower thermosphere and mesosphere. EEP increase the production of NOx and HOx, which will catalytically destroy stratospheric ozone, an important element of atmospheric dynamics. Therefore, measurement of the latitudinal extent of the precipitation boundaries is important in quantifying atmospheric effects of Sun-Earth interaction.
This study uses measurements by Medium Energy Proton Electron Detector (MEPED) of six NOAA/POES and EUMETSAT/METOP satellites from 2004 to 2014 to determine the latitudinal boundaries of EEP and its variability with geomagnetic activity and solar wind drivers. Variation of the boundaries with respect to different particle energies and magnetic local time is studied. Regression analyses are applied to determine the best predictor variable based on solar wind parameters and geomagnetic indices. The highest correlation was found for pressure-corrected Dst index through linear regression. Although, the model has an error estimate of ±2.2° cgmlat and exhibits a solar cycle bias, it performs well in predicting the precipitation boundaries. The result will be a key element for constructing a model of EEP variability to be applied in atmosphere climate models.

How to cite: Babu, E. M., Tyssøy, H. N., Smith-Johnsen, C., Maliniemi, V., Salice, J. A., and Millan, R.: Determining latitudinal extent of energetic electron precipitation  using MEPED on-board NOAA POES, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1322, https://doi.org/10.5194/egusphere-egu22-1322, 2022.

To model ionospheric climate and to study its long-term changes and trends we need solar activity proxies, because long and homogeneous data series of solar ionizing flux are not available. To select the optimum solar activity proxies, we use yearly average foF2 data of eleven ionospheric stations from middle and low/equatorial latitudes of four continents over 1976-2014 and six solar activity proxies, F10.7, sunspot numbers, F30, Mg II, He II and solar Lyman-α flux. For middle latitudes and higher low latitudes down to about 20-24oN, Mg II and F30 are found to be the optimum solar proxies, not the usually used F10.7 or sunspot numbers. At lower and particularly equatorial latitudes the situation is different; the optimum proxy for Jicamarca is sunspot number and He II, and for Vanimo He II. Solar activity describes 99% of the total variance of yearly foF2 at midlatitudes and its dependence on solar proxies is highly linear. Long-term trends in foF2 are found to depend to some extent on solar proxy used

How to cite: Laštovička, J.: Different optimum solar activity proxies for foF2 at middle and low latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1593, https://doi.org/10.5194/egusphere-egu22-1593, 2022.

EGU22-1660 | Presentations | ST3.4

Modeling horizontal currents and magnetic ground perturbations with the IPIM model 

Julian Eisenbeis, Pierre-Louis Blelly, Simon Thomas, and Aurelie Marchaudon

The IRAP Plasmasphere Ionosphere Model (IPIM) is an ionospheric model which describes the transport equations of ionospheric plasma species along magnetic closed field lines. The development of a new operational version of IPIM as part of the EUHFORIA project to monitor and forecast space weather conditions and hazards includes using in-situ solar wind observations from the OMNI data set, ionospheric radar data of plasma motions from the Super Dual Auroral Radar Network (SuperDARN), and precipitation data from the Ovation model, as inputs to the model. A new conductivity module has also been developed for help in the simulation of geomagnetically induced currents based on a simplified version of IPIM. This model uses the photochemical module of IPIM in place of the fluid module and the full kinetic module, so that inter-hemispheric transport of suprathermal electrons is accounted for in the ion production term. As the main contribution to the conductivities comes from the lower ionosphere (typically below 150km) where the chemistry dominates, neglecting the field-aligned transport contribution in the fluid module does not alter significantly the conductivities. Based on the conductivities, the neutral wind and the electric field, ionospheric horizontal currents are computed. The ionospheric currents are used as an input for the Biot and Savart module to compute the resulting magnetic perturbations at the ground. We present the first results from this version which explores the ionosphere's response to different conditions in different regions in mid and high latitudes.

How to cite: Eisenbeis, J., Blelly, P.-L., Thomas, S., and Marchaudon, A.: Modeling horizontal currents and magnetic ground perturbations with the IPIM model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1660, https://doi.org/10.5194/egusphere-egu22-1660, 2022.

EGU22-2309 | Presentations | ST3.4

Comprehensive analysis of the response of the ionospheric F2-layer to the largest geomagnetic storms from solar cycle #24 over Europe 

Kitti Alexandra Berényi, Árpád Kis, Balázs Heilig, Jaroslav Urbář, and Veronika Barta

The complex analysis of the largest geomagnetic storms of solar cycle #24 maximum is our main aim in this study. Our focus is on the ionosphere, more precisely on the ionospheric F2-layer. The selected storm intervals are: 11-17 November 2012 (Kpmax=6.33, Dstmin=-108 nT ), 16-23 March 2013 (Kpmax= 6.67, Dstmin=-132 nT ),  and 16-25 March 2015 (Kpmax=7.67, Dstmin=-228 nT). Data from 6 digisonde (DPS4D) stations, ground GNSS TEC and Swarm satellite constellation have been used for the investigation.

This study is the next step to validate our previous results discussed in Berényi et al. (2018). We analyse the meridional behaviour of the geomagnetic disturbance caused ionospheric storms to understand and interpret the evolution of the caused effects.

The storm from 2012 is a no-positive phase (NPP) storm, but the 2013 and 2015 storms show the pattern of the regular positive phase (RPP) storm type (after the categorization by Mendillo and Narvaez, 2010). In all three cases a significant increase in electron density of the F2-layer can be observed at dawn/early morning (around 6:00 UT, 07:00 LT).  We compared also the digisonde foF2 parameter with the GNSS TEC data. Besides, we observed the fade-out of the ionospheric layers at night during the geomagnetically disturbed time periods of storm 2012 and 2015. In order to determine whether this fade-out is connected to the L-shell location of the plasmapause we analysed the Swarm observations (for the storm 2015), too.

Berényi, K. A., Barta, V., & Kis. (2018). Midlatitude ionospheric F2-layer response to eruptive solar events-caused geomagnetic disturbances over Hungary during the maximum of the solar cycle 24: A case study. Advances in Space Research, 61(5), 1230–1243. https://doi.org/10.1016/j.asr.2017.12.021

Mendillo, M., & Narvaez, C. (2010). Ionospheric storms at geophysically-equivalent sites - Part 2: Local time storm patterns for sub-auroral ionospheres. Annales Geophysicae, 28(7), 1449–1462. https://doi.org/10.5194/angeo-28-1449-2010

How to cite: Berényi, K. A., Kis, Á., Heilig, B., Urbář, J., and Barta, V.: Comprehensive analysis of the response of the ionospheric F2-layer to the largest geomagnetic storms from solar cycle #24 over Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2309, https://doi.org/10.5194/egusphere-egu22-2309, 2022.

EGU22-2324 | Presentations | ST3.4

Investigating the variation of the ionospheric absorption during large solar flares based on modern Digisonde data 

Attila Buzás, Dalia Burešová, Daniel Kouba, Zbyšek Mošna, and Veronika Barta

As a result of the enhanced X-ray and EUV fluxes following large solar flares, the electron density of the ionospheric layers increases. Furthermore, it causes higher absorption or even partial or total fade-out of the emitted radio waves which can be measured with ionosondes and Digisondes by studying the amplitude of the reflected electromagnetic waves [1,2].

In the present study, the ionospheric response to large solar flares has been investigated using the ionosonde data measured at the Průhonice (Czech Republic, 49.98° N, 14.55° E) and San Vito (Italy, 40.6° N, 17.8° E) stations in September 2017, the most active solar period of Solar Cycle 24. A novel method [3]  to calculate and investigate the absorption of radio waves propagating in the ionosphere is used to determine the absorption during large solar flare events (M and X class). Subsequently, the absorption data are compared with the indicators derived from the fmin method (fmin, the minimum frequency is considered as a qualitative proxy for the “nondeviative” radio wave absorption occurring in the D-layer). Total and partial radio fade-out and increased values (with 2–5 MHz) of the fmin parameter were experienced during and after the intense solar flares (> M3). Furthermore, the signal-to-noise ratio (SNR) measured by the Digisondes was used as well to quantify and characterize the fade-out events and the ionospheric absorption. The combination of these three methods may prove to be an efficient approach to monitor the ionospheric response to solar flares.

[1] Sripathi, S., Balachandran, N., Veenadhari, B., Singh, R., and Emperumal, K.: Response of the equatorial and low-latitude ionosphere to an intense X-class solar flare (X7/2B) as observed on 09 August 2011, J. Geophys. Res.-Space, 118, 2648–2659, 2013.

[2] Barta, V., Sátori, G., Berényi, K. A., Kis, Á., and Williams, E. (2019). Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa. Annales Geophysicae, Vol. 37, No. 4, pp. 747-761

[3] Sales, G. S., 2009, HF absorption measurements using routine digisonde data, Conference material, XII. International Digisonde Forum, University of Massachusetts

How to cite: Buzás, A., Burešová, D., Kouba, D., Mošna, Z., and Barta, V.: Investigating the variation of the ionospheric absorption during large solar flares based on modern Digisonde data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2324, https://doi.org/10.5194/egusphere-egu22-2324, 2022.

EGU22-2360 | Presentations | ST3.4

Statistics of transpolar arcs identified by an automated detection algorithm 

Gemma Bower, Steve Milan, Larry Paxton, and Suzie Imber

Transpolar arcs (TPAs) are auroral features that occur polewards of the main auroral oval, at latitudes where auroras are less common, suggesting that the magnetosphere has acquired a complicated magnetic topology. They are primarily a northward interplanetary magnetic field auroral phenomenon, and their formation and evolution have no single explanation that is unanimously agreed upon. An automated detection algorithm has been developed to detect the occurrence of TPAs in UV images captured by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument onboard the Defense Meteorological Satellite Program (DMSP) spacecraft, in order to further study their occurrence. Via this detection algorithm TPAs are identified as a peak in the average radiance intensity above 12.5° colatitude, in two or more of the wavelengths/bands sensed by SSUSI.

Using the detection algorithm on observations from the years 2010 to 2016, over 5000 images containing TPAs are identified. The occurrence of these TPA images suggest a seasonal dependence, with more TPAs observed in the winter hemisphere. The orbital plane of DMSP has been investigated as a possible explanation of the dependences in the results of the detection algorithm. It has been found that each DMSP spacecraft has a different bias due to its orbit. For the spacecraft of interest (F16, F17 and F18) this leads to a preferential observation of the northern hemisphere, with the detection algorithm missing TPAs in the southern hemisphere around 01 - 06 UT. No seasonal bias has been found for these spacecraft.

We also discover that the majority of TPAs occur in the dawn sector of the polar cap, which is unexpected in current TPA models. Comparing with previous statistical surveys, we note that the dawn-dusk asymmetry has been present but has not gained significant attention.  We suggest that field-aligned current polarity may play a role in the observed asymmetry.

We discuss the ramifications of these findings in terms of proposed TPA generation mechanisms and suggest reasons for the seasonal dependence including it being a reflection of probability of seeing TPAs due to visibility.

How to cite: Bower, G., Milan, S., Paxton, L., and Imber, S.: Statistics of transpolar arcs identified by an automated detection algorithm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2360, https://doi.org/10.5194/egusphere-egu22-2360, 2022.

EGU22-3759 | Presentations | ST3.4

Empirical modelling of SSUSI derived auroral ionization rates 

Stefan Bender, Patrick Espy, and Larry Paxton

Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models with interactive chemistry in the upper atmosphere, such as WACCM-X or EDITh, usually parametrize this ionization and calculate the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra. These satellites provide in-situ measurements of the particle populations at the satellite altitude, but require interpolation and modelling to infer the actual input into the upper atmosphere.

Here we use the electron energy and flux data products from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of currently three operating satellites observes both auroral zones in the far UV from (115--180 nm) with a 3000 km wide swath and 10 x 10 km (nadir) pixel resolution during each orbit. From the N2 LBH emissions, the precipitating electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate auroral ionization rates in the lower thermosphere (≈ 90–150 km), which have been validated previously against ground-based electron density measurements from EISCAT. We present an empirical model of these ionization rates derived for the entire satellite operating time and sorted according to magnetic local time and geomagnetic latitude and longitude. The model is based on geomagnetic and solar flux indices, and a sophisticated noise model is used to account for residual noise correlations. The model will be particularly targeted for use in climate models that include the upper atmosphere, such as the aforementioned WACCM-X or EDITh models. Further applications include the derived conductances in the auroral region, as well as modelling and forecasting E-region disturbances related to Space Weather.

How to cite: Bender, S., Espy, P., and Paxton, L.: Empirical modelling of SSUSI derived auroral ionization rates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3759, https://doi.org/10.5194/egusphere-egu22-3759, 2022.

EGU22-4262 | Presentations | ST3.4

Multi-instrument observations of polar cap patches and traveling ionospheric disturbances during geomagnetic storms 

Paul Prikryl, Robert G. Gillies, Shibaji Chakraborty, David R. Themens, Evan G. Thomas, and James M. Weygand

Solar wind Alfvén waves [1] coupling to the magnetosphere-ionosphere-thermosphere (MIT) have been associated with high-intensity long-duration continuous auroral electrojet activity [2] and shown to modulate ionospheric convection in the cusp generating polar cap patches and atmospheric gravity waves [3,4]. The Resolute Bay Incoherent Scatter Radars (RISR-C and RISR-N) [5] are well suited for observing the ionospheric signatures of flux transfer events and subsequent polar patch formation in the cusp.  During minor to moderate geomagnetic storms caused by corotating interaction regions at the leading edge of solar wind high speed streams polar patches were observed as they convected over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN) ionosondes and GPS receivers [6]. The patches were generated by the MIT coupling of Alfvén waves in the upstream solar wind. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including auroral electrojets. The horizontal equivalent ionospheric currents and vertical current amplitudes are estimated from the ground-based magnetometer data using an inversion technique [7].  Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves causing traveling ionospheric disturbances (TIDs) propagating equatorward. TIDs were observed in the SuperDARN HF radar ground scatter [8], in the detrended GPS TEC maps, and in one case, in the altitude profiles of ionospheric electron densities observed by the Poker Flat ISR [9].

[1] Belcher, JW, Davis, L, Jr. 1971. J. Geophys. Res. 76, 3534–3563.

[2] Tsurutani, BT, Gonzalez, WD. 1987. Planet. Space Sci. 35(4), 405–412.

[3] Prikryl, P, et al., 1999. Ann. Geophys. 17, 463–489.

[4] Prikryl, P, et al., 2005. Ann. Geophys. 23, 401–417.

[5] Gillies RG, et al., 2016. Radio Sci., 51(10):1645-1659.

[6] Jayachandran, PT, et al., 2009. Radio Sci., 44, RS0A03.

[7] Weygand, JM, et al., 2011. J. Geophys. Res. 116, A03305.

[8] Chisham, G., et al., 2007. Surv. Geophys. 28, 33–109.

[9] Heinselman, CJ, Nicolls, MJ, 2008. Radio Sci., 43, RS5013.

How to cite: Prikryl, P., Gillies, R. G., Chakraborty, S., Themens, D. R., Thomas, E. G., and Weygand, J. M.: Multi-instrument observations of polar cap patches and traveling ionospheric disturbances during geomagnetic storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4262, https://doi.org/10.5194/egusphere-egu22-4262, 2022.

EGU22-4829 | Presentations | ST3.4

The Ionospheric Alfvén Resonator observed at Eskdalemuir magnetic observatory  

Rosie Hodnett, Timothy Yeoman, Darren Wright, and Ciarán Beggan

Ionospheric Alfvén Resonances (IAR) are observed in the British Geological Survey's ground based induction coil magnetometer data at Eskdalemuir. IAR are caused when Alfvén waves are partially reflected at boundaries of changing plasma density in the ionosphere. At the boundaries, the Alfvén velocity reaches a maximum and the IAR occurs in the cavity which is in the F region. In the data we observed some unusual variations in the frequency of the harmonics and so created a model to investigate this. We have modelled the harmonic frequency separation of the IAR using the magnetic field strength from the International Geomagnetic Reference Field, and the electron density and ion composition from the International Reference Ionosphere. We found the Alfvén velocity and calculated the time of flight for the Alfvén wave to travel up and down the cavity, and hence we found the frequency. The model shows that the frequency is highest in the winter, and often shows a double peak each day in the winter months. We then compared the model of the harmonic frequency separations to the harmonic frequency separations from the data, determined from an autocorrelation analysis of the observed spectra.

How to cite: Hodnett, R., Yeoman, T., Wright, D., and Beggan, C.: The Ionospheric Alfvén Resonator observed at Eskdalemuir magnetic observatory , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4829, https://doi.org/10.5194/egusphere-egu22-4829, 2022.

EGU22-5277 | Presentations | ST3.4

Multi-instrumental investigation of the solar flares impact on the ionosphere occurring in December 2006 

Veronika Barta, Randa Natras, Vladimir Srećković, David Koronczay, Michael Schmidt, and Desanka Šulic

The sudden increase of X-radiation and EUV emission following solar flares causes additional ionization and increased absorption of electromagnetic (EM) waves in the sunlit hemisphere of the Earth’s ionosphere. The solar flare impact on the ionosphere above Europe on 05 and 06 December 2006 was investigated using ground-based (ionosonde and VLF) and satellite-based data (Vertical Total Electron Content (VTEC) derived from Global Navigation Satellite Systems (GNSS) observations and VLF measurements from the DEMETER satellite). Based on the geomagnetic indices Kp and Dst, 05 December was a quiet day, while there was a geomagnetic storm on 06 December 2006.

The total fade-out of the EM waves emitted by the ionosondes was experienced at all investigated stations during an X9 class flare on 05 December. The variation of the fmin parameter ( representing the minimum frequency of the echo trace observed in the ionogram, and is a rough measure of the “nondeviative” absorption) and its difference between the quiet period and during the flares have been analyzed. A latitude dependent enhancement of fmin (2-9 MHz) and Delta_fmin (relative change of about 150-300 %) was observed at every station at the time of the X9 (on 05 December) and M6 (on 06 December) flares.

Furthermore, we analyzed VTEC changes during and after the flare events with respect to the mean VTEC values of reference quiet days. During the X9 solar flare, VTEC increased depending on the latitude (2-3 TECU and 5-20 %). On 06 December, the geomagnetic storm increased ionization (5-10 TECU) representing a „positive” ionospheric storm. However, an additional peak in VTEC related to the M6 flare could not be detected.

We have also observed a quantifiable change in transionospheric VLF absorption of signals from ground transmitters detected in low Earth orbit associated with the X9 and M6 flare events on 05 and 06 December in the DEMETER data. Moreover, amplitude and phase of ground-based, subionospherically propagating VLF signals were measured simultaneously during the investigated flares to analyze ionosphere reaction and to evaluate the electron density profile versus altitude. For the X9 and M6 flare events we have also calculated the ionospheric parameters (sharpness, reflection height, etc.) important for the description and modeling of this medium under forced additional ionization.

How to cite: Barta, V., Natras, R., Srećković, V., Koronczay, D., Schmidt, M., and Šulic, D.: Multi-instrumental investigation of the solar flares impact on the ionosphere occurring in December 2006, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5277, https://doi.org/10.5194/egusphere-egu22-5277, 2022.

EGU22-5482 | Presentations | ST3.4

Detection of Solar Flares from the Analysis of Signal-To-Noise Ratio Recorded by Digisonde at Ebro Observatory 

Antoni Segarra, Victor de Paula, David Altadill, Juan Jose Curto, and Estefania Blanch

This work proposes a new indirect method to detect solar flares based on the effects that produce in the signal of the radio waves reflected from the ionosphere as observed by a digisonde. Analysis of the signal-to-noise ratio (SNR) measured from ionograms for Ebro Observatory ionospheric station made possible to estimate a daily pattern of the SNR under no flare conditions and to detect absorption effects in the SNR caused under flare conditions. The method allows to characterize the ionospheric absorption of High Frequency radio waves as a product of these energetic events, and provides observational data to the international Service of Rapid Magnetic Variations (SRMV) to confirm Sfe (Solar Flare Effects). To set up the method, we have analyzed a data set of solar flares occurred during 2011—2014 at daylight hours at EB040 (262 flares, 17 X-class, 124 M-class, and 121 C-class). This led to impose a minimum threshold of -20dB in the SNR for at least four consecutive frequencies to confirm that a given solar flare happened. The method is particularly sensitive in the X-class solar flares detection, performs quite well with M-class flares and even detects some C-class flares. Furthermore, we deeply studied the observational and energetic constraints that affect the detection of the solar flares from the analysis of GOES hard X-Ray; e.g. for each event, we computed the solar altitude angle at the time of the ionospheric sounding to get an estimation of the geoeffective irradiance which has an effect on the local ionosphere. According to these constraints, we can confirm that the method is more effective for detection of flares that occur when the solar elevation angle is higher than 18.94º and have a geoeffective hard X-Ray irradiance above of 3.30·10-6 W/m2.

How to cite: Segarra, A., de Paula, V., Altadill, D., Curto, J. J., and Blanch, E.: Detection of Solar Flares from the Analysis of Signal-To-Noise Ratio Recorded by Digisonde at Ebro Observatory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5482, https://doi.org/10.5194/egusphere-egu22-5482, 2022.

EGU22-5686 | Presentations | ST3.4

Characteristics of Fragmented Aurora-like Emissions (FAEs) 

Joshua Dreyer, Noora Partamies, Daniel Whiter, Pål G. Ellingsen, Lisa Baddeley, and Stephan C. Buchert

We present observations of a new type of small-scale aurora-like feature, which is further referred to as fragmented aurora-like emission(s) (FAEs).

They seem to appear in two categories – randomly occurring individual FAEs and wave-like structures with regular spacing between FAEs alongside auroral arcs. FAEs show horizontal sizes typically below 20 km, a lack of field-aligned emission extent, and short lifetimes of less than a minute. Emissions were observed at the 557.7 nm line of atomic oxygen and at 673.0 nm (N2; first positive band system) but not at the 427.8 nm emission of N2+ or the 777.4 nm line of atomic oxygen. This suggests an upper limit to the energy that can be produced by the generating mechanism. Their lack of field-aligned extent and 777.4 nm emissions indicates a different generation mechanism than for aurorae, which are caused by particle precipitation. Possible sources are Farley–Buneman instabilities or electrostatic ion cyclotron waves.

How to cite: Dreyer, J., Partamies, N., Whiter, D., Ellingsen, P. G., Baddeley, L., and Buchert, S. C.: Characteristics of Fragmented Aurora-like Emissions (FAEs), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5686, https://doi.org/10.5194/egusphere-egu22-5686, 2022.

EGU22-6035 | Presentations | ST3.4

Fine-scale electric felds and Joule heating from observations of the Aurora 

Patrik Krcelic, Robert Fear, Daniel Whiter, Betty Lanchester, and Anasuya Aruliah

Our goal is to research highly dynamic electric fields near auroral arcs and their effects on the thermosphere via Joule heating. Optical measurements from three selected wavelengths have been combined with modelling of emissions from an auroral event to estimate the magnitude and direction of small-scale electric fields on either side of an auroral arc. The direction of these fields was found to be towards the arc on both sides. The temporal resolution of the estimates is 0.1 seconds, which is much higher resolution than measurements from SuperDARN from the same region, with which we compare our estimates. Additionally, we have used the SCANDI instrument to measure the neutral wind during the event in order to calculate the height integrated Joule heating. Joule heating obtained from the small scale electric fields gives higher values than the Joule heating obtained from more conventionally used SuperDARN data. This result indicates that high resolution electric felds may play an important role in the dynamics of the thermosphere, and thus the ionosphere-magnetosphere system in general. Furthermore, we are aiming to combine our method with EISCAT-measured electron density profiles and high- resolution spectrographic observations of N2 auroral emissionto obtain local Joule heating profile. We will then compare it to the estimates of a local neutral temperature profiles.

How to cite: Krcelic, P., Fear, R., Whiter, D., Lanchester, B., and Aruliah, A.: Fine-scale electric felds and Joule heating from observations of the Aurora, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6035, https://doi.org/10.5194/egusphere-egu22-6035, 2022.

EGU22-6101 | Presentations | ST3.4

Long-Term Trends in the Equatorial Ionization Anomaly 

Sovit Khadka and Andrew Gerrard

Due to the special geometry of the electric and magnetic fields at the equator, the vertical ExB drift removes plasma from the geomagnetic equator via an equatorial plasma fountain. This process forms the equatorial ionization anomaly (EIA) by creating the crests at/around 20° latitudes on either side of the geomagnetic equator. It has been reported that symmetric/asymmetric structure and latitudinal extent of the EIAs are affected by the electric fields and thermospheric neutral winds. We investigate the long-term trends in the equatorial ionization anomaly (EIA) and associated phenomena over the South American low-latitude region. These long-term analyses help to develop/update the empirical model of various ionospheric parameters. The EIA features are analyzed using the ground-based Global Positioning System (GPS)-total electron content (TEC) data. We also compare the TEC in EIA obtained from the latest International Reference Model (IRI) model with the observed GPS-TEC data for seasons, different levels of solar activity, and geomagnetic conditions. Finally, We discuss the mechanisms, drivers, and impacts of the EIAs in upper atmospheric electrodynamics. 

How to cite: Khadka, S. and Gerrard, A.: Long-Term Trends in the Equatorial Ionization Anomaly, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6101, https://doi.org/10.5194/egusphere-egu22-6101, 2022.

EGU22-6396 | Presentations | ST3.4

Energy input in the dayside polar cap during IMF By dominated conditions: Summer vs. Winter 

Jone Peter Reistad, Karl Magnus Laundal, Anders Ohma, and Spencer Hatch

When IMF By is dominant, which is the typical situation, a highly vortical convection pattern is seen inside the dayside polar cap in the summer hemisphere. In the winter hemisphere, however, the convection is mainly from noon to midnight with little vorticity inside the polar cap. Combined with the vastly different ionospheric conductance between summer and winter due to solar EUV irradiance, these differences in convection cause large summer/winter differences in the Birkeland currents in the dayside polar cap. Hence, the joule heating rates will be very different in the dayside polar cap between summer and winter during the IMF By dominant periods, which is typically associated with weak geomagnetic activity inside the auroral oval. This presentation will focus on the hemispheric differences in e.g. joule heating during such conditions, which will be quantified using the newly developed LOcal Mapping of Polar ionospheric Electrodynamics (Lompe) data assimilation technique. The Lompe technique is similar to the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) technique, but allows the electrodynamics to be described only in a limited region to reflect the observational coverage. The prescribed conductance will be provided from UV imaging of the aurora (in addition to EUV), allowing also the energy from precipitation to be estimated. While existing empirical models [e.g. Weimer 2005, doi:10.1029/2004JA010884] capture some aspects of the hemispheric asymmetries, this presentation will focus on how recent advances in data assimilation techniques allows us to quantify these asymmetries on an event basis, showing how these typical conditions can lead to vastly different energy input into the two hemispheres.

How to cite: Reistad, J. P., Laundal, K. M., Ohma, A., and Hatch, S.: Energy input in the dayside polar cap during IMF By dominated conditions: Summer vs. Winter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6396, https://doi.org/10.5194/egusphere-egu22-6396, 2022.

EGU22-6535 | Presentations | ST3.4

High-resolution Poynting fluxes derived from the ESA Swarm mission: How much are we underestimating? 

Daniel Billett and Kathryn McWilliams

The ESA Swarm constellation of satellites have been measuring the ionospheric electric and perturbation magnetic fields since 2013. Recently, the entire dataset of Swarm electric fields has been reprocessed into a 16Hz data product, allowing the analysis of ionospheric dynamics on sub-kilometre scales.

In combination with the on-board magnetometer data, the Swarm satellites can use the electric field measurements to determine the total electromagnetic energy into and out of the ionosphere, the Poynting flux. The 16Hz dataset allows for the capturing of much smaller scale sizes than previously considered, thus presenting the opportunity to study how much Poynting flux is missed when utilizing data across typically monitored scales (usually on the order of tens to hundreds of kilometres).

We present a statistical analysis of the Swarm A and B derived 16Hz Poynting flux, utilising various low-pass filters on the electric and magnetic field data to simulate smoothing the data to larger scale sizes. We find that by increasing the width of the low-pass filters, measured Poynting flux decreases significantly and quickly. Our results show that there is an over 50% underestimation in the total hemisphere integrated Poynting flux when observing it on scale sizes of a few hundred kilometres, compared to the raw 16Hz measurements that correspond to scales of around 0.5km. Under certain circumstances, as much as a 10% underestimation in the Poynting flux is observed by increasing scale size to only 5km. These results stress the importance observing small-scale electric and magnetic fields, as they may account for a large proportion of the ionosphere-thermosphere energy budget.

How to cite: Billett, D. and McWilliams, K.: High-resolution Poynting fluxes derived from the ESA Swarm mission: How much are we underestimating?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6535, https://doi.org/10.5194/egusphere-egu22-6535, 2022.

EGU22-8135 | Presentations | ST3.4

High latitude ionospheric electric field models comparison 

Lauren Orr, Adrian Grocott, Maria Walach, Mai Mai Lam, Mervyn Freeman, Gareth Chisham, and Robert Shore

Modern high latitude ionospheric electric field models have been developed to incorporate advances in data availability, however the use of older spacecraft-based models is still widespread.  AENeAS (Advanced Ensemble electron density [Ne] Assimilation System) is a physics-based, thermosphere-ionosphere, coupled, assimilative model, which makes possible thermospheric forecasts. Currently AENeAS uses the Heelis and Weimer electric field spacecraft climatology models but it is possible a more recent electric field model could improve its functionality.  Two such models are calculated using line-of-sight velocity measurements from the Super Dual Auroral Radar Network (SuperDARN): the Thomas and Shepherd model (TS18), and the Time-Variable Ionospheric Electric Field model (TiVIE) . Here we compare the electric field models during the September 2017 storm, covering a range of solar wind and interplanetary magnetic field (IMF) conditions. We explore the relationships between the IMF conditions and model output parameters such as transpolar voltage, the polar cap size and the lower latitude boundary. We find the spacecraft-based model electric potential and field parameters to have a significantly higher magnitude than the SuperDARN-based models. We will discuss the similarities and differences in topology and magnitude for each model.

How to cite: Orr, L., Grocott, A., Walach, M., Lam, M. M., Freeman, M., Chisham, G., and Shore, R.: High latitude ionospheric electric field models comparison, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8135, https://doi.org/10.5194/egusphere-egu22-8135, 2022.

EGU22-8283 | Presentations | ST3.4

A consistently derived set of empirical models for high-latitude electrodynamics 

Spencer Hatch, Karl M Laundal, Jone P Reistad, and Anders Ohma

The ionosphere-thermosphere research community has clearly expressed a need for improved, observation-based estimates of key ionosphere-thermosphere parameters such as Joule dissipation, Poynting flux, and ionospheric conductances. While global estimates of these key parameters can be obtained by combining existing empirical models, one often encounters some frustrating sources of uncertainty: the models to be combined often use different input parameters, different assumptions about hemispheric symmetry, and/or different coordinate systems. We eliminate these sources of uncertainty by deriving a new model of high-latitude ionospheric potential that can be combined with the Average Magnetic Field and Polar Current System (AMPS) model to obtain empirical estimates of Joule dissipation, Poynting flux, and ionospheric conductances. These models treat the two hemispheres independently, are derived in a mutually consistent fashion, and are based entirely on electric and magnetic field measurements made by the Swarm satellites.

How to cite: Hatch, S., Laundal, K. M., Reistad, J. P., and Ohma, A.: A consistently derived set of empirical models for high-latitude electrodynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8283, https://doi.org/10.5194/egusphere-egu22-8283, 2022.

EGU22-9261 | Presentations | ST3.4

Height-integrated polar cap conductances during an average substorm 

Jennifer A. Carter, Steven Milan, Mark Lester, Colin Forsyth, Larry Paxton, Jesper Gjerloev, and Brian Anderson

We track the progression of height-integrated conductances over the course of an average substorm in a narrow local time sector of the nightside polar cap. These conductances are calculated from the mean energy flux and energy flux of precipitation, as estimated from a ratio of auroral emissions of the Lyman-Birge-Hopfield long and short band obtained by multiple polar region crossings of the Defence Meteorological Satellite Program F16, F17, and F18 spacecraft. Contributing auroral emission data span 1 January 2005 to 31 December 2017. Both Pedersen and Hall conductances are considered, as well as the influence of the magnetic latitude of substorm onset. Substorm onset times and magnitudes are provided by the SuperMAG network and SOPHIE substorm lists. We compare superimposed epoch ordered conductances with similarly averaged field aligned currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). Shortly before onset, conductances increase in a low latitude region, before an increase in conductance seen at all latitudes at the time of onset. The energy flux is shown to peak quickly after substorm onset, followed by mean energy. The conductances, energy flux, and mean energy are ordered by magnetic latitude of substorm onset, so that the lowest onset latitudes correspond to the highest value of any given parameter. Conductances recover quicker to pre-substorm levels for those substorms with higher onset magnetic latitudes.

 

How to cite: Carter, J. A., Milan, S., Lester, M., Forsyth, C., Paxton, L., Gjerloev, J., and Anderson, B.: Height-integrated polar cap conductances during an average substorm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9261, https://doi.org/10.5194/egusphere-egu22-9261, 2022.

EGU22-9989 | Presentations | ST3.4

Tracing the evolution of energetic particle fluxes using radar inversion techniques  

Joseph Mayes, Darren Wright, and Timothy Yeoman

Following the dynamic processes in the Earth-Sun system such as magnetic reconnection a significant amount of energy is transferred inwards from the outer magnetosphere by magnetohydrodynamic (MHD) waves. One of the ways this energy is dissipated is through energetic particle precipitation. In order to understand this energy transfer it is important that we are able to quantify the evolution of energetic particles as they precipitate. This study investigates the nature of the precipitating electron energy spectrum, whether the particles are accelerated and where the energy is absorbed in the atmosphere.

By inverting EISCAT incoherent scatter radar (ISR) data to produce a modelled incident energetic electron flux entering the upper atmosphere as detected by the radar and comparing those with the flux observed by satellites such as DMSP and Arase as they traverse flux tubes conjugate to the radar, we have been able to investigate both the magnitude of acceleration of energetic particles as well as how different energies are accelerated as they move down flux tubes. We will use these modelled fluxes to determine the level of field aligned acceleration of the energetic particles and the altitude profile of energy deposition.

How to cite: Mayes, J., Wright, D., and Yeoman, T.: Tracing the evolution of energetic particle fluxes using radar inversion techniques , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9989, https://doi.org/10.5194/egusphere-egu22-9989, 2022.

EGU22-10777 | Presentations | ST3.4

Ionospheric Measurement Using a Linearly Polarized Tri-Band Small Satellite Beacon 

Ferry Pascal Lanter, Adrian Sutinjo, and John Morgan

Radio waves propagating the ionosphere are subject to a number of unpredictable and corrupting effects, the most significant of which are phase path reduction, Faraday rotation, and scintillation. A method of measuring these effects is therefore necessary in order to study, understand and anticipate their impact. The rise in popularity of small satellites presents a new cost-effective opportunity to study the ionosphere in detail, however the challenge of realizing a beacon within the constraints of a CubeSat system must be overcome. First we introduce a measurement technique that builds on past multi-frequency beacons, incorporating the well established differential phase technique, as well as introducing a new differential polarization technique. We achieve this by employing linearly polarized beacon signals, which enables us to separate phase path reduction and Faraday rotation into a phase and polarization change respectively. The introduction of linear polarization overcomes some of the key limitations in current ionospheric measurement techniques: eliminating errors associated with indirect Faraday rotation measurement, and enabling absolute unambiguous parameter measurement. To validate the capability of measuring the ionosphere within the constraints of a small satellite package, we establish the influence of system noise, weak scattering, clock errors and antenna characteristics on the measurement technique. We then use this to inform a practicable CubeSat beacon design solution which achieves absolute and high resolution measurement of ionospheric parameters within the constraints of the system.

How to cite: Lanter, F. P., Sutinjo, A., and Morgan, J.: Ionospheric Measurement Using a Linearly Polarized Tri-Band Small Satellite Beacon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10777, https://doi.org/10.5194/egusphere-egu22-10777, 2022.

EGU22-11881 | Presentations | ST3.4

AMICal Sat, ATISE : From imagery to spectro-imagery for auroral studies 

Mathieu Barthelemy, Vladimir Kalegaev, and Elisa Robert

Space weather is a system science in the sense that it includes a chain of complex phenomena coming from the Sun and going to the Earth mainly through the magnetosphere. Added to this, the effects on the Earth infrastructures and their vulnerability should be taken into account. All this chain is too poorly described to allow accurate nowcasting and forecasting of the space weather events and of their effects on Earth. In this chain, the upper atmosphere as well as its interface with the magnetosphere require improvements in their description.

Precipitations of auroral electrons along magnetic lines lead to auroras, which are one of the most striking manifestations of space weather. These phenomena characterize the relationship of the magnetosphere and the upper atmosphere, and their intensity and localization indicate the state of near-Earth space. The energy release in the region of the auroral oval, associated with precipitation of auroral electrons, is controlled by the solar wind parameters and is one of the important reasons leading to changes in space weather in the polar magnetosphere and ionosphere.

In this frame, one of the main gaps in both data and modelling is the monitoring of the precipitation of low-energy (0.02 − 30keV ) particles in the ionosphere and in the magnetosphere, especially electrons which are key contributors to ionospheric currents.

Numerous satellites observed the polar lights both in the UV and visible, however AMICal Sat is the first cubesat to be dedicated to the observation of the optical emissions of the auroras. It contains a sparse RGB imager and has been launched on board the VV16 flight, September 3rd 2020. It will be followed by a spectrometer ATISE planned to be launched in 2023.

In this presentation, we propose to present the first results of AMICal Sat, the data processing to extract the intensity of each lines and thus deduce the electron fluxes. Plans for ATISE developments and ground based tests will also be detailed.

How to cite: Barthelemy, M., Kalegaev, V., and Robert, E.: AMICal Sat, ATISE : From imagery to spectro-imagery for auroral studies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11881, https://doi.org/10.5194/egusphere-egu22-11881, 2022.

EGU22-12282 | Presentations | ST3.4

Optical observations of thermospheric neutral temperature in aurora 

Daniel Whiter and David Price

The aurora can have strong electric fields and currents associated with it, which deposit a significant amount of energy in the neutral upper atmosphere through heating. Such heating must be included in global atmospheric models used to study thermospheric dynamics, coupling between the atmospheric layers, climate, and drag on spacecraft and space debris in low Earth orbit. However, the heating rate is poorly quantified, and often spatial structure is not well represented. Heating is typically estimated by measuring the ionospheric electric field using radar, which is then combined with measurements or estimates of the neutral wind velocity and Pedersen conductivity to calculate a Joule heating rate. However, such measurements of the electric field necessarily neglect small scale spatial and temporal variability through their relatively coarse resolution and averaging. The Joule heating rate is proportional to the square of the electric field, and therefore the spatial and temporal averaging can lead to a significant underestimate of the Joule heating rate. As a step towards improving estimates of neutral heating, we have developed a technique to invert spectrographic measurements of aurora to observe the thermospheric neutral temperature altitude profile at high temporal resolution. Application of the technique to an auroral event shows substantial Joule heating adjacent to an arc where the E-field must be strong, as well as heating embedded within an auroral curl, which we associate with an intense field-aligned current.

How to cite: Whiter, D. and Price, D.: Optical observations of thermospheric neutral temperature in aurora, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12282, https://doi.org/10.5194/egusphere-egu22-12282, 2022.

EGU22-12298 | Presentations | ST3.4

Mid-latitude comparisons of ion and neutral velocity observations with general circulation model outputs. 

Elliott Day, Adrian Grocott, Maria Walach, Jim Wild, Gang Lu, Michael Ruohoniemi, and Jonathan Makela

Modelling of Joule heating is key to understanding the impact of space weather on the neutral atmosphere. One of the most commonly used models in the scientific community is the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). The modelled plasma and neutral wind velocities are key parameters for Joule heating estimates, however there is limited validation of TIEGCM’s performance at mid-latitudes. In this study we use the Blackstone Super Dual Auroral Radar Network (SuperDARN) and the Michigan North American Thermosphere Ionosphere Observing Network (NATION) Fabry-Perot interferometer (FPI) to obtain the local nightside plasma and neutral velocities at ~40 degrees geographic latitude during a 10 hour interval on 15 July 2014 and compare our observations with the outputs from TIEGCM. We find that TIEGCM lacks the variability seen in our observations while overestimating quiet time plasma velocities as well as neutral wind velocities during both quiet and active times compared to our observations. We also find that TIEGCM agrees with the observed neutral wind flow direction but disagrees with the observed plasma flow direction. We note that a better representation of the mid-latitude neutral winds and ion drifts is required in order to improve the accuracy of the modelled Joule heating rate. 

How to cite: Day, E., Grocott, A., Walach, M., Wild, J., Lu, G., Ruohoniemi, M., and Makela, J.: Mid-latitude comparisons of ion and neutral velocity observations with general circulation model outputs., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12298, https://doi.org/10.5194/egusphere-egu22-12298, 2022.

EGU22-12910 | Presentations | ST3.4

Main ionospheric trough and field-aligned currents responses to the geomagnetic storms in October 2015 and September 2017 

Agata Chuchra-Konrad, Dorota Przepiórka, Barbara Matyjasiak, and Hanna Rothkaehl

The Earth's ionosphere is a coupled system affected by interactions with precipitating energetic particles and electrical currents from the Earth's magnetosphere, and in addition by upward propagating disturbances from lower atmospheric layers. Geomagnetic disturbances triggered by solar activity influence the ionosphere, its fine and global structures. The energy injection into the magnetosphere during geomagnetic storms and substorms directly affects the auroral and sub-auroral region of the Earth’s ionosphere, where auroral oval expansion and variations of plasma density and field-aligned currents intensity can be observed. Main ionospheric trough (MIT) and field-aligned currents (FACs) are very sensitive to geomagnetic conditions. This work analyses both phenomenon response to the elevated geomagnetic conditions during October 2015 and September 2017 geomagnetic storms. The analysis is based on the data from the Swarm and DMSP missions.

How to cite: Chuchra-Konrad, A., Przepiórka, D., Matyjasiak, B., and Rothkaehl, H.: Main ionospheric trough and field-aligned currents responses to the geomagnetic storms in October 2015 and September 2017, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12910, https://doi.org/10.5194/egusphere-egu22-12910, 2022.

In this work, the effect of disturbance dynamo electric field (DDEF) induced by subauroral polarization streams (SAPS) on the variations of the equatorial electrojet (EEJ) and its counter electrojet (CEJ) during the geomagnetic storm on June 1, 2013 is analyzed in detail for the first time. Observations from ground-based magnetometers showed that the SAPS-induced EEJ flows westward and eastward in the daytime and dawn/dusk sectors, respectively. The effects of SAPS on EEJ are mainly associated with the changes of zonal ionospheric electric field, while the changes in the ionospheric conductivity play a secondary role. By using Thermosphere Ionosphere Electrodynamic General Circulation Model simulations, the zonal electric field induced by SAPS associated with the DDEF is examined. The results of the simulations show that the DDEF has a significant impact on the EEJ variability. The daytime westward EEJ at the dip equator is mainly driven by disturbance zonal wind, with secondary contributions from disturbance meridional wind. A similar mechanism can be observed in the dawn/dusk sector when the eastward EEJ is produced; however, it has a much weaker intensity than that during the daytime.

How to cite: Zhang, K., Yamazaki, Y., and Xiong, C.: Effects of Subauroral Polarization Streams on the Equatorial Electrojet During the Geomagnetic Storm on June 1, 2013, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-21, https://doi.org/10.5194/egusphere-egu22-21, 2022.

Using ground-based magnetic field measurements and numerical simulations from the Thermosphere-Ionosphere Electrodynamic General Circulation Model (TIEGCM), a first paper (Zhang et al., 2021b, under review) introduced the potential roles of disturbance dynamo electric field due to subauroral polarization streams (SAPS) on the equatorial electrojet (EEJ) during a moderate geomagnetic storm on June 1, 2013. Our second study investigated the temporal responses of equatorial electrojet to SAPS. At noon, the residual EEJ (ΔEEJ) owing to SAPS flows westward, that is, counter equatorial electrojet (CEJ). The temporal variation of CEJ excited by the dynamo electric field was basically consistent with that by SAPS, and the effects of zonal wind were larger than those of meridional wind. The relative time delay of CEJ and SAPS was related to the propagation time of disturbance wind from mid-latitudes to low-latitudes. It took 2-3 h for SAPS-related disturbance wind to propagate to the equatorial region and change the polarity of EEJ. The influence of meridional winds on the temporal variations of ΔEEJ is related to the generation of eastward currents at mid-latitudes, which can accumulate the positive charges at dusk terminator and then generate a westward electric field at lower latitudes.

How to cite: Qian, C. and Zhang, K.: Effects of Subauroral Polarization Streams on the Equatorial Electrojet During the Geomagnetic Storm on June 1, 2013. Part II: the temporal variations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-984, https://doi.org/10.5194/egusphere-egu22-984, 2022.

Based on Thermosphere-Ionosphere Electrodynamics General Circulation Model simulation and CHAllenging Minisatellite Payload observations, the effects of the geomagnetic field intensity and solar activity on the thermospheric zonal wind and the related physical mechanisms are investigated. The weakening of the magnetic field results in an increase in the westward wind during the daytime and a decrease in the eastward wind at night, and leading to a decreasing superrotation. The weakening solar activity causes a reduction in the zonal wind and superrotation. The theoretical term analysis shows that when the magnetic field is weakened, the vertical upward drift velocity of the plasma increases, resulting in a decrease in the electron density and ion drag in the F layer. The weakening of eastward acceleration of the viscous force and ion drag results in an enhanced westward wind. The downward drift velocity of ions increases at night, resulting in an increase in the electron density at the F layer, while the ion-neutral velocity difference decreases. The weakening of eastward acceleration of the pressure gradient and viscous force at night are the main reasons for the decreased eastward wind. The reduced solar activity leads to a decrease in the pressure gradient and ion drag. Combined with the change of viscous force, these processes cause the decrease in the superrotation. The geomagnetic field configuration is the main reason for the variation in the superrotation with UT. When the magnetic field is weakened, although the average neutral wind decreases, the Pedersen conductivity of the F-layer is quadrupled. Therefore, the meridional current system driven by the F-layer dynamo is enhanced accordingly. Due to obvious longitudinal difference in the magnetic field intensity, the longitudinal variation of superrotation is expected.

How to cite: Gao, J. and Zhang, K.: Influence of the Magnetic Field Strength and Solar Activity on the Thermospheric Zonal Wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-985, https://doi.org/10.5194/egusphere-egu22-985, 2022.

EGU22-998 | Presentations | ST3.5

Local time variations of auroral electrojet during storm time: DMSP and CHAMP coordinated observations 

Yunfang Zhong, Hao Xia, and Chengyu Qian

The auroral electrojet plays an important role in the ionosphere-magnetosphere coupling progress. Based on ten years of DMSP and CHAMP coordinated observations, we investigate the local time variations of the auroral electrojets during storm periods. The results show that the auroral electrojets respond obviously to the sudden change of solar wind inputs (merging electric field, substorm, and interplanetary shock) in all local time. The local time asymmetry of the response time and strength of the electrojets to these three types of disturbances are investigated. The auroral electrojets respond to the shock faster than the sudden change of merging electric field. The disturbed auroral electrojet strength peaks at different local times during different kinds of solar wind input events. The different features of eastward and westward electrojets during storm periods are studied during the disturbance periods. The physical mechanisms for the local time variations of auroral electrojets in response to the disturbance are discussed in detail. 

How to cite: Zhong, Y., Xia, H., and Qian, C.: Local time variations of auroral electrojet during storm time: DMSP and CHAMP coordinated observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-998, https://doi.org/10.5194/egusphere-egu22-998, 2022.

     

        The high-resolution Vector Field Magnetometer and Langmuir Probe onboard the Swarm satellites provide us an opportunity to observe both EMIC wave and plasma density oscillation. A total of 102 plasma density oscillation events were found during storm time from 2014 to 2018. The temporal and spatial distribution of these oscillation events is roughly consistent with the EMIC wave. The longitudinal distribution and related mechanism are studied. There are obvious magnetic local time (MLT) differences in the peak occurrence rate of plasma density oscillation during storm phases and distinct geomagnetic activity. As the geomagnetic disturbance intensifies,the plasma density oscillations show a trend of westward drift and are more likely to occur at lower latitudes. For all plasma density oscillation events, the phase of these oscillation with EMIC wave is different. Most plasma density oscillation have a relative amplitude ratio of 100 to 1000 to the compressional wave, the possible mechanism is discussed in detail.

How to cite: He, Y. and Sun, L.: A Stastistical study of plasmas density oscillation induced from pc1 wave by Swarm Satellites during storm time from 2014 to 2018, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1000, https://doi.org/10.5194/egusphere-egu22-1000, 2022.

In the present work, the magnetic local time and latitude (MLT and MLat) distributions of ionospheric large-scale (> 20° MLat) electromagnetic ion cyclotron waves were investigated using high-resolution 50-Hz geomagnetic field data from Swarm A and B satellites. Both longitudinal and transverse waves were studied in a comparative manner for different geomagnetic activities and seasons. Frequent occurrences of large-scale waves in the South Atlantic Anomaly and North America, where the longitudinal waves propagate over the longest distance, were observed. Waves appear mostly in the 02–10 MLT sector wherein the pre-noon longitudinal waves propagate farthest in latitudinal range. With the enhancement of geomagnetic activity, both transverse and longitudinal waves increase in occurrence. The dayside occurrence rate is higher during weak geomagnetic activity, whereas the situation is reversed on the nightside and duskside. The dayside waves are located outside of the mid-latitude trough, and the nightside waves are located near (inside) the equatorward boundary of the mid-latitude trough. Large-scale waves tend to occur at the equinox when the absolute value of the dipole tilt angle is less than 10°, while the long-distance transmission in the waveguide occurs in the pre-noon in summer. Longitudinal waves propagate in the region where the electron density is higher than that of the transverse waves. This study reveals potential factors that contribute to the occurrence of ionospheric waveguide events.

How to cite: Sun, L. and Liu, Y.: Magnetic local time and latitude distribution of ionospheric large-scale EMIC wave events: Swarm observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1001, https://doi.org/10.5194/egusphere-egu22-1001, 2022.

 Based on the magnetic field observation of Swarm satellite from 2015 to 2019, the variation of ionospheric radial current (IRC) with local time and geographic longitude at March equinox, June solstice and December solstice are analyzed, respectively. The observations are compared with the simulation results of thermosphere ionosphere electrodynamics general circulation model (TIE-GCM). The observed IRC are mainly downward in the noon section and upward in the evening section, which is reproduced well by the model. The zonal distribution of IRC shows obvious local time asymmetry. The downward IRC in the eastern hemisphere in the noon section is greater than that in the western hemisphere, while the upward IRC in the western hemisphere in the evening section is greater than that in the eastern hemisphere. This zonal variation in the evening sector is more obvious at March equinox and less obvious at June solstice. The simulation results of TIE-GCM also show similar zonal characteristics, especially on the nightside. The physical mechanisms of the local time and geographic longitude distribution of IRC are discussed in details.

How to cite: Xia, H. and Qian, C.: Zonal variation of ionospheric radial current (IRC) as observed by Swarm and simulated by TIE-GCM, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1412, https://doi.org/10.5194/egusphere-egu22-1412, 2022.

EGU22-1511 | Presentations | ST3.5

Assimilation of total electron content in a SAMI3 simulation 

John Haiducek, Joseph Helmboldt, and Joseph Huba

Total electron content (TEC) observations can provide insights into electron density variations in the ionosphere. Such variations are associated with many aspects of ionospheric dynamics, including traveling ionospheric disturbances. In the present work we assimilate observations of TEC and horizontal TEC gradients into the SAMI3 (SAMI3 is Another Model of the Ionosphere 3D) ionosphere model. Assimilation into SAMI3 is accomplished using an ensemble Kalman filter implemented within LightDA, an extensible data assimilation library. Our TEC gradient observations are obtained from the Very Large Array Low-band Ionosphere and Transient Experiment (VLITE) and the TEC measurements are derived from GNSS receiver data. VLITE provides high precision and high spatial resolution TEC gradient observations over a small area, while GNSS observations supplement these with global coverage. By leveraging TEC observations in a physics-based model through data assimilation, we aim to improve our understanding of ionospheric processes and develop tools for improved ionospheric forecasting capabilities.

How to cite: Haiducek, J., Helmboldt, J., and Huba, J.: Assimilation of total electron content in a SAMI3 simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1511, https://doi.org/10.5194/egusphere-egu22-1511, 2022.

EGU22-3034 | Presentations | ST3.5

Thermospheric density variation and its response to Joule heating during geomagnetic storms 

Xin Wang, Siqing Liu, Juan Miao, Xian Lu, Ercha Aa, and Binxian Luo

Thermospheric density is essential for the calculation of atmospheric drag, which is the main cause of the orbit decay for low-Earth-orbit (LEO) satellites. During geomagnetic storms, the Joule heating has a strong impact on neutral mass density. In this work, we statistically investigate 265 geomagnetic storms to explore the response of thermospheric density to Joule heating from 2002 to 2008. We obtain the density enhancements from Challenging Minisatellite Payload (CHAMP) and the Gravity Recovery and Climate Experiment (GRACE) satellites, and we also calculate Joule heating from the Defense Meteorological Satellite Program (DMSP) spacecraft and the Weimer electric potential model. The results show that the thermospheric density delays Joule heating during geomagnetic storms. The time lag is about 0-2 hrs during weak and moderate storms, while it is 3-5 hrs for intense storms. In addition, Joule heating can affect the density enhancement at higher latitude regions. The latitudinal difference between thermospheric density and Joule heating is about 0°-10° during weak and moderate geomagnetic storms, while it increases to 10°-15° for intense storms. Besides, we use the temporal relationship of thermospheric density with geomagnetic activity indices and Joule heating as calibration for the NRLMSISE-00 model during geomagnetic storms. The calibrated NRLMSISE-00 model results can better simulate the storm-time thermospheric density, with the Mean Relative Error (MRE) between observation and model decreasing from 40% to 10%.

How to cite: Wang, X., Liu, S., Miao, J., Lu, X., Aa, E., and Luo, B.: Thermospheric density variation and its response to Joule heating during geomagnetic storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3034, https://doi.org/10.5194/egusphere-egu22-3034, 2022.

EGU22-5961 | Presentations | ST3.5

Evidence for Presence of a Global Resonant Mode of Oscillations During High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events 

Diptiranjan Rout, Ram Singh, Kuldeep Pandey, Tarun Pant, Claudia Stolle, Dibyendu Chakrabarty, Smitha Thampi, and Tikemani Bag

The interaction between the Sun and the Earth defines the space environment of the Earth. This interaction is complex and exhibits various time scales ranging from a  few seconds to years. The High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events are mainly the manifestations of the interactions of the corotating interaction regions (CIRs) with the terrestrial magnetosphere which continues for several days. The responses of two HILDCAA events are investigated by using solar wind observations at the L1 point, magnetospheric measurements at geosynchronous orbit, and changes in the global ionosphere. This study provides evidence of the existence of quasi-periodic oscillations (1.5-2hr) in the ionospheric electric field over low latitude, total electron content at high latitude, the magnetic field over the globe, energetic electron flux and magnetic field at geosynchronous orbit, geomagnetic indices (SYM-H, AE, and PC) and the Y-component of the interplanetary electric field (IEFy) during the HILDCAA events at all local times. Based on detailed wavelet and cross-spectrum analyses, it is shown that the periodic oscillations of 1.5-2hr in IEFy are the most effective one that controls the solar wind-magnetosphere-ionosphere coupling process during the  HILDCAA events for several days. Therefore, this investigation for the first time, shows that the  HILDCAA event affects the global magnetosphere-ionosphere system with a “resonant” mode of oscillation. These results are important not only to evaluate the solar wind-magnetosphere-ionosphere coupling process during the HILDCAA events but can also help to build up a forecasting strategy in the future.

How to cite: Rout, D., Singh, R., Pandey, K., Pant, T., Stolle, C., Chakrabarty, D., Thampi, S., and Bag, T.: Evidence for Presence of a Global Resonant Mode of Oscillations During High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5961, https://doi.org/10.5194/egusphere-egu22-5961, 2022.

EGU22-8194 | Presentations | ST3.5

Total Electron Content Variations during an HSS/CIR driven storm at high and middle latitudes 

Gopika Prasannakumara Pillai Geethakumari, Anita Aikio, Lei Cai, Heikki Vanhamaki, Marcus Pedersen, Anthea Coster, Aurelie Marchaudon, Pierre-Louis Blelly, Veronika Haberle, Astrid Maute, Nada Ellahouny, Ilkka Virtanen, Johannes Norberg, Shin-Ichiro Soyama, and Maxime Grandin

Magnetic storms are caused by the interactions between the solar wind and the Earth’s magnetosphere. Many studies have been carried out for strong magnetic storms. However, moderate or weak storms and their impacts on the ionosphere are less explored. This study investigates the large-scale and mesoscale structures in ionospheric total electron content (TEC) during a moderate storm (Sym-H index minimum: -63 nT) driven by two interacting solar wind high-speed streams (HSSs) and associated co-rotating interaction regions (CIRs) during 14-21 March 2016. For the solar wind, the IMF Bz minimum is -20 nT and the solar wind speed maximum 612 km/s. The long storm starts with a strong storm sudden commencement (SSC) with a peak close to 19 UT on 14 March 2016. The GNSS/TEC maps are obtained from the Madrigal database. The associated field-aligned currents (FACs) from AMPERE, ionospheric convection maps from SuperDARN, and the O/N2 ratio from TIMED/GUVI are also studied for understanding the physics behind.

The focus of the study is on the changes of TEC at high and middle latitudes and the possible coupling between the two. To better characterize the changes, we subtract from the TEC maps the quiet time background (13 March 2016). Our analysis shows the different responses of TEC changes during the storm initial, main, and recovery phases. During the initial phase, TEC enhancements and depletions are found mainly at high latitudes within the auroral oval and close to the cusp, plausibly associated with auroral precipitation and variations in the upward and downward field-aligned currents (FACs). After the onset of the main phase, the TEC is enhanced at mid-latitudes with a maximum of ~10 TECU. During the main phase, we observe the evolution of a storm-enhanced-density (SED) plume and a transient enhancement of TEC in the polar cap. During the late main and the recovery phases, a strong TEC depletion at high and middle latitudes is found on the dayside and in the evening sector. The depletion is associated with the decrease of the O/N2 ratio indicating upwelling of the neutral atmosphere. The possible physical mechanisms associated with the observed TEC variations will be discussed.

How to cite: Geethakumari, G. P. P., Aikio, A., Cai, L., Vanhamaki, H., Pedersen, M., Coster, A., Marchaudon, A., Blelly, P.-L., Haberle, V., Maute, A., Ellahouny, N., Virtanen, I., Norberg, J., Soyama, S.-I., and Grandin, M.: Total Electron Content Variations during an HSS/CIR driven storm at high and middle latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8194, https://doi.org/10.5194/egusphere-egu22-8194, 2022.

EGU22-8322 | Presentations | ST3.5

Ionosphere and Thermosphere Observations in the Context of Whole Atmosphere Modelling 

Maria-Theresia Walach, Adrian Grocott, Lauren Orr, Wuhu Feng, Daniel Marsh, and Anasuya Aruliah

Modelling the whole atmosphere from the surface to the ionosphere allows us to better forecast and understand our weather and climate. It is a scientific and computational challenge to model this complex system numerically with its many drivers and feedback loops. Recent efforts to improve whole atmosphere models include raising the altitude to incorporate improved representations of the ionosphere and thermosphere. The Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) is one of the most comprehensive numerical models, spanning the range of altitude from the Earth’s surface to the upper thermosphere (~700 km). WACCM-X can model the global ionosphere and thermosphere, whilst providing coupling between atmosphere layers through chemical, physical and dynamical processes. Using WACCM-X, we can explore the implications of this coupling for the climate and for the near space environment. 

The high-latitude ionosphere-thermosphere behaves dynamically during geomagnetically active times due to time-varying solar wind driving and internal magnetospheric dynamics. We present high- and mid-latitude observations from the Super Dual Auroral Radar Network, Incoherent Scatter Radars and Fabry-Perot Interferometers which observe the ionosphere-thermosphere system. We investigate observed plasma flows, which respond directly to solar wind driving, alongside WACCM-X model simulations which are nudged to a meteorological reanalysis dataset in the troposphere and stratosphere during a variety of solar storm conditions. We discuss these in the context of time-varying dynamics due to solar wind driving and investigate the expansion of the high-latitude convection to lower latitudes during geomagnetic storms. Our results show that the latitudinal expansion is not yet fully captured in WACCM-X and we discuss how this may be mitigated. We further show that during a geomagnetic storm, the differences between the WACCM-X ionospheric data and the observations by SuperDARN at high- to mid-latitudes may vary by up to ~20 kV for the electrostatic potential during a geomagnetic storm. This translates to an electric field difference of 25 mV/m and differences in the plasma drift velocities in excess of ~800 m/s.

How to cite: Walach, M.-T., Grocott, A., Orr, L., Feng, W., Marsh, D., and Aruliah, A.: Ionosphere and Thermosphere Observations in the Context of Whole Atmosphere Modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8322, https://doi.org/10.5194/egusphere-egu22-8322, 2022.

EGU22-880 | Presentations | ST3.6

First results from comparison ERA5 and Aeolus measurements: Lidar measurements to Identify Streamers and analyze Atmospheric waves (LISA) (Aeolus+Innovation) 

Michal Kozubek, Jan Lastovicka, Jaroslav Chum, Tereza Sindelarova, Katerina Podolska, Lisa Kuechelbacher, Sabine Wuest, and Michael Bittner

For a better understanding of atmospheric dynamics, it is very important to know the general condition (dynamics and chemistry) in the atmosphere. Aeolus wind measurements provide wind measurements from satellite instrument. ERA 5 can produce very detailed information about dynamics without gaps in time series in high resolution (0.25°). Planetary waves (PWs) are global scale waves, which are well-known as main drivers of the large-scale weather patterns in mid-latitudes on time scales from several days up to weeks in the troposphere. When PWs break, they often cut pressure cells off the jet stream. A specific example are so-called streamer events, which occur predominantly in the mid- and high-latitudes of the lower stratosphere. Streamers are characterized by ozone-poor airmasses occuring mainly in the Northern Atlantic / European section and leading to various consequences due to a strong increase of UV radiation. We compare ERA5 reanalysis with Aeolus measurements. This comparison can bring us an answer if we can use ERA5 instead of Aeolus measurements in case of time gaps. We also use homogeneity test for ERA5 time series. Moreover, we also analyze characteristics of gravity waves (GW) in the ionosphere using continuous Doppler sounding and in the troposphere using large aperture array of microbarometers. Similarly, ground based infrasound monitoring is performed. We investigate, if there are any changes of GW or infrasound characteristics related to stratospheric processes, e.g., streamer events.

How to cite: Kozubek, M., Lastovicka, J., Chum, J., Sindelarova, T., Podolska, K., Kuechelbacher, L., Wuest, S., and Bittner, M.: First results from comparison ERA5 and Aeolus measurements: Lidar measurements to Identify Streamers and analyze Atmospheric waves (LISA) (Aeolus+Innovation), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-880, https://doi.org/10.5194/egusphere-egu22-880, 2022.

EGU22-1136 | Presentations | ST3.6

Planetary wave-driven enhanced NO descent into the top of the Arctic polar vortex during major and minor sudden stratospheric warmings 

V. Lynn Harvey, Nicholas Pedatella, Seebany Datta-Barua, Cora Randall, David Siskind, Katelynn Greer, and Larisa Goncharenko

The polar vortices play a central role in vertically coupling the Sun-Earth system by facilitating the descent of reactive odd nitrogen (NOx = NO + NO2) produced in the atmosphere by energetic particle precipitation (EPP-NOx). Downward transport of EPP-NOx from the mesosphere-lower thermosphere (MLT) to the stratosphere inside the winter polar vortex is particularly impactful in the wake of prolonged sudden stratospheric warming (SSW) events. This work is motivated by the fact that state-of-the-art global climate models severely underestimate EPP-NOx abundances in the polar MLT. It is not clear whether this deficiency is due to a missing NOx source or to inadequate transport processes. As a step toward understanding the transport pathways by which MLT air enters the top of the polar vortex, we explore the extent to which planetary waves impact the geographic distribution of NO near the polar winter mesopause in the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension combined with data assimilation using the Data Assimilation Research Testbed (WACCMX+DART). We present planetary wave-driven NO patterns near the polar winter mesopause during 16 case studies from the Arctic winters of 2005/2006 through 2018/2019. During all cases the model is in reasonable agreement with Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) derived zonal winds and Solar Occultation For Ice Experiment (SOFIE) and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) NO measurements. Superposed Epoch Analysis is employed to diagnose typical mesopause planetary wave behavior and vertical transport characteristics during 10 minor and 6 major SSW events. Results show that descent of NO into the top of the polar vortex is enhanced by about a factor of 4 in traveling planetary wave troughs vs. in ridges and that this planetary wave-driven enhanced NO descent occurs during both minor and major SSW events. These results present a new conceptual model of zonally varying, vs. zonally uniform, polar descent in the MLT.

How to cite: Harvey, V. L., Pedatella, N., Datta-Barua, S., Randall, C., Siskind, D., Greer, K., and Goncharenko, L.: Planetary wave-driven enhanced NO descent into the top of the Arctic polar vortex during major and minor sudden stratospheric warmings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1136, https://doi.org/10.5194/egusphere-egu22-1136, 2022.

EGU22-1317 | Presentations | ST3.6

Attenuation of gravity waves and kinetic viscosity in the ionosphere 

Jaroslav Chum, Mariano Fagre, Katerina Podolska, and Jan Rusz

     Gravity waves (GW) couple various atmospheric layers and influence dynamics of the region in which they dissipate their energy. Attenuation of GW is in this contribution calculated from the ratio of GW kinetic energies observed at different heights by multi-frequency and multi-point continuous Doppler sounding that allows three-dimensional (3D) analysis of GW propagation in the ionosphere. It is shown that the attenuation of GWs increases with height, which is consistent with the hypothesis that mainly viscous damping and losses due to thermal conductivity are responsible for the wave attenuation in the thermosphere/ionosphere. The kinematic viscosity of the highly rarefied air at the height of observation is estimated from the observed attenuation with altitude and complex dispersion relation for GWs that includes viscosity and thermal conductivity, which is linked with the viscosity via Prandtl number. The intrinsic (wind rest frame) characteristics of GW that enter the dispersion relation are obtained after subtracting the neutral wind velocities from the observed phase velocities using HWM-14 wind model. A more detailed modelling of GW attenuation will be done in the future. 

How to cite: Chum, J., Fagre, M., Podolska, K., and Rusz, J.: Attenuation of gravity waves and kinetic viscosity in the ionosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1317, https://doi.org/10.5194/egusphere-egu22-1317, 2022.

EGU22-1942 | Presentations | ST3.6

Comparison of the Tidal Signatures in Sporadic E and Vertical Ion Convergence Rate, Using FORMASAT-3/COSMIC Radio Occultation Observations and GAIA Model 

Sahar Sobhkhiz-Miandehi, Yosuke Yamazaki, Christina Arras, Yasunobu Miyoshi, and Hiroyuki Shinagawa

Sporadic E or Es is a transient phenomenon where thin layers of enhanced electron density appear in the ionospheric E region (90-120 km altitude). Es can influence radio propagation, and its global characteristics have been of great interest to radio communications and navigations. The presence of neutral wind shear caused by atmospheric tides will lead ions to converge at E-region heights and form Es layers.The neutral wind shear caused by atmospheric tides can lead ions to converge vertically at E-region heights and form the Es layers. This research aims to determine the role of atmospheric solar and lunar tides in Es occurrence. For this purpose, radio occultation data of FORMASAT-3/COSMIC have been used, which provides complete global coverage of Es events. Moreover, GAIA model simulations have been employed to evaluate the vertical ion convergence induced by solar tides. The results show both migrating and non-migrating solar tidal signatures and the semidiurnal migrating lunar tidal signature in Es occurrence. The seasonal variations of the diurnal and semidiurnal solar migrating components of Es are in good agreement with those in the zonal wind shear. Furthermore, some non-migrating components of solar tides also have a significant effect on the Es occurrence rate.

How to cite: Sobhkhiz-Miandehi, S., Yamazaki, Y., Arras, C., Miyoshi, Y., and Shinagawa, H.: Comparison of the Tidal Signatures in Sporadic E and Vertical Ion Convergence Rate, Using FORMASAT-3/COSMIC Radio Occultation Observations and GAIA Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1942, https://doi.org/10.5194/egusphere-egu22-1942, 2022.

EGU22-2763 | Presentations | ST3.6

Quasi-2-Day Wave in Low-Latitude Atmospheric Winds as Viewed From the Ground and Space During January–March, 2020 

Maosheng He, Jorge L. Chau, Jeffrey M. Forbes, Xiaoli Zhang, Christoph R. Englert, Brian J. Harding, Thomas J. Immel, Lourivaldo M. Lima, S. Vijaya Bhaskar Rao, M. Venkat Ratnam, Guozhu Li, John M. Harlander, Kenneth D. Marr, and Jonathan J. Makela

In the mesosphere and lower-thermosphere, quasi-2-day waves are spectacular planetary-scale oscillations. Almost all relevant observational studies are based on ground-based single-station or single-satellite methods and, therefore, cannot determine the zonal wavenumber unambiguously. We employ a series of multi-station methods on winds measured by four longitudinally separated low-latitude ground-based radars in the current work. These methods help us to determine two dominant zonal wavenumbers at 80–100 km altitude. These results are used to complement satellite measurements. The agreement between datasets is extraordinary, allowing us to extend the characteristics of the waves to higher altitudes using satellite measurements.

The current work was published in He et al. (2021, https://doi.org/10.1029/93jd00380), which was extended into a broad altitude range up to the topside F-region in Forbes et al. (2021, https://doi.org/10.1029/2021JA029961).

How to cite: He, M., Chau, J. L., Forbes, J. M., Zhang, X., Englert, C. R., Harding, B. J., Immel, T. J., Lima, L. M., Rao, S. V. B., Ratnam, M. V., Li, G., Harlander, J. M., Marr, K. D., and Makela, J. J.: Quasi-2-Day Wave in Low-Latitude Atmospheric Winds as Viewed From the Ground and Space During January–March, 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2763, https://doi.org/10.5194/egusphere-egu22-2763, 2022.

Ionospheric day‐to‐day variability is ubiquitous, even under undisturbed geomagnetic and solar conditions. In this paper, quiet‐time day‐to‐day variability of equatorial vertical E × B drift is investigated using observations from ROCSAT‐1 satellite and the Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCM‐X) v2.1 simulations. Both observations and model simulations illustrate that the day‐to‐day variability reaches the maximum at dawn, and the variability of dawn drift is largest around June solstice at ~90–180°W. However, there are signifificant challenges to reproduce the observed magnitude of the variability and the longitude distributions at other seasons. Using a standalone electro‐dynamo model, we fifind that the day‐to‐day variability of neutral winds in the E‐region (≤~130 km) is the primary driver of the day‐to‐day variability of dawn drift. Ionospheric conductivity modulates the drift variability responses to the E‐region wind variability, thereby determining its strength as well as its seasonal and longitudinal variations. Further, the day‐to‐day variability of dawn drift induced by individual tidal components of winds in June are examined: DW1, SW2, D0, and SW1 are the most important contributors.

How to cite: Zhou, X.: Quiet‐Time Day‐to‐Day Variability of Equatorial Vertical E × B Drift From Atmosphere Perturbations at Dawn, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3361, https://doi.org/10.5194/egusphere-egu22-3361, 2022.

EGU22-3552 | Presentations | ST3.6

Global Teleconnections between QBO Dynamics and ITM Anomalies 

Valery Yudin, Larisa Goncharenko, Svetlana Karol, Ruth Lieberman, Hanli Liu, Joe McInerney, and Nicholas Pedatella

The importance of the realistic predictions of the climate variability in the whole atmosphere system, vertical and horizontal teleconnections between the stratospheric QBO and SAO and ITM dynamics are now well recognized. The paper presents a brief summary of the QBO impact on the MLT neutral dynamics seen from the last decade of ITM observations and predictions by two whole atmosphere models constrained in the lower atmosphere by GEOS meteorology of NASA/GMAO. We present the initial modeling and observational evidences that the QBO-related variations in the MLT thermal tides can modulate the equatorial ionospheric anomaly wave-4 and wave-3 longitudinal structure affecting the ITM system on regional scales. Several hypotheses about the influence of the stratospheric QBO on the ionosphere due to the combined influences of migrating and non-migrating tides will be suggested based on the preliminary multi-year observational analysis of TEC data.   

How to cite: Yudin, V., Goncharenko, L., Karol, S., Lieberman, R., Liu, H., McInerney, J., and Pedatella, N.: Global Teleconnections between QBO Dynamics and ITM Anomalies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3552, https://doi.org/10.5194/egusphere-egu22-3552, 2022.

EGU22-5895 | Presentations | ST3.6

Long-term variations and trends in the E and sporadic E layer over Juliusruh (54° N), Europe 

Mani Sivakandan, Jens Mielich, Toralf Renkwitz, and Jorge L. Chau

Sporadic E (Es) is a thin layer of metallic ion plasma that forms in the E region of the Earth’s ionosphere, mostly between 90 and 125 km. It can affect the radio frequencies in the HF range of up to 30 MHz. In the mid-latitudes, the wind shear mechanism causes the formation of the Es layers. In general, solar forcing primarily controls changes in the E layer. On the other hand, the formation of the mid-latitude Es layer is driven by the wind shear associated with lower atmosphere originated wave activities. Since the formation of the Es layer is caused by the lower atmospheric forcing, it can be used as a tracer to estimate the lower atmospheric impact on the upper mesosphere and lower thermosphere (UMLT). Therefore, the study of the long-term changes and trends (if any) in the E and Es layers will throw some light on the effect of the lower atmosphere and solar forcing on the UMLT region.

In the present study, we investigate the long-term variation and trends in the E region, using sixty-three years of continuous ionosonde observations over Juliusruh (54.6° N 13.4° E), Europe. Before the trend analysis, predominant long-term variations are estimated using the Lomb-Scargle periodogram analysis. We found that the annual and solar cycle oscillations are strongly present in both foE and foEs. In addition, a weak semi-annual oscillation is also noted in the foE.  Furthermore, the model time series data of foE and foEs is created using the period and amplitude of the predominant oscillations. Then, the residual value of foE and foEs is calculated by subtracting the model values from the observation. By using the least square fit analysis, the trend is estimated. Interestingly, weak negative trends in the foE and foEs are found. The plausible causative mechanism for the observed trends will be detailed in the presentation.

How to cite: Sivakandan, M., Mielich, J., Renkwitz, T., and Chau, J. L.: Long-term variations and trends in the E and sporadic E layer over Juliusruh (54° N), Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5895, https://doi.org/10.5194/egusphere-egu22-5895, 2022.

EGU22-6823 | Presentations | ST3.6

Influence of stratospheric gravity waves on TID activity at middle latitudes 

Larisa Goncharenko, V Lynn Harvey, Chihoko Cullens, Erich Becker, Shun-Rong Zhang, and Anthea Coster

This study investigates the role of hotspots in stratospheric gravity waves (GWs) in the generation of traveling ionospheric disturbances (TIDs) at middle latitudes. We utilize observations of GWs at 35 km altitude by the Atmospheric InfraRed Sounder (AIRS) on NASA’s Aqua satellite to characterize stratospheric gravity wave activity. The evolution of GWs with altitudes extending from the stratosphere to mesosphere-lower-thermosphere (MLT) region is examined using temperature observations from the Sounding of the Atmosphere using Broadband Emission Radiometry instrument. Ground-based total electron content observations from GNSS receivers are used to characterize TID activity in the ionosphere. Simulations by the High Altitude Mechanistic general Circulation Model (HIAMCM) that is nudged to the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) reanalysis in the troposphere and stratosphere are used to study multi-step vertical coupling between the stratosphere and the thermosphere.  We investigate two case studies, the Arctic winter of 2016/2017 when a sudden stratospheric warming developed in January-February 2017, and the winter of 2019/2020 that was characterized by mostly strong polar vortex conditions. The hotspot in stratospheric GWs peaks at 55-75N at the edge of polar vortex and in a limited range of longitudes.  Our results indicate that GW activity evolves with altitude and expands to 35-40N in the MLT region. Amplifications of TIDs during times of high stratospheric GW activity are seen from ~25-30N to 60N. HIAMCM simulations indicate a very good agreement with observations in the timing of GW activity and latitudinal coverage. We conclude that TIDs are generally amplified during high stratospheric GW activity and weakened during the periods of low stratospheric GW activity (during and after SSW).

How to cite: Goncharenko, L., Harvey, V. L., Cullens, C., Becker, E., Zhang, S.-R., and Coster, A.: Influence of stratospheric gravity waves on TID activity at middle latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6823, https://doi.org/10.5194/egusphere-egu22-6823, 2022.

The ionosphere exhibits enhanced semi-diurnal lunitidal (M2) perturbations during sudden stratospheric warming (SSW) events, of which the manifestation and mechanism are not well documented and understood. We studied the latitudinal and interhemispheric variations of the ionospheric M2 perturbations during the 2009 SSW with total electron content (TEC) data in the American and eastern Asia-Australia sectors. Results show that the M2 perturbations in the two sectors all enhanced during the SSW. The largest M2 amplitudes in the Northern and Southern Hemispheres appear at about 15°N and 20°S geomagnetic latitudes, respectively, with stronger magnitude in the Northern Hemisphere. Also, M2 perturbations in the two sectors all extend to middle latitudes only in the Southern Hemisphere and show local maxima around 35~40°S geomagnetic latitudes. The similar latitudinal and interhemispheric variations of the low-latitude M2 perturbtations in the two sectors indicate that such variations may be mainly caused by the meridional wind modulation on the equatorial plasma fountain. Meanwhile, the longitudinal differences are also noticeable. The TEC M2 amplitude in the American sector is obviously larger than that in the eastern Asia-Australia sector, especially in the southern middle latitude. The M2 perturbations in the American southern middle latitude may be influenced by the combined effect of the zonal wind and local positive magnetic declination in the Weddell Sea Anomaly region.

How to cite: Liu, J., Zhang, D., Hao, Y., and Xiao, Z.: The latitudinal and interhemispheric variations of the ionospheric M2 perturbations during the 2009 SSW in the American and eastern Asia-Australia sectors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8318, https://doi.org/10.5194/egusphere-egu22-8318, 2022.

EGU22-9390 | Presentations | ST3.6

Planetary wave activity observed in atmosphere-ionosphere system over low latitudes 

Ashish Jadhav, Gurubaran Subramanian, and Parashram Patil

The coupled response of the atmosphere-ionosphere system to planetary waves propagating from below has been observed through MF and Meteor radars at different longitudes along with the ground geomagnetic data from 23 stations of Northern (NH) and Southern Hemisphere (SH) during northern winter months of January, 2015 and 2017. The focus is on delineating the quasi-2-day (Q2DW) and quasi-6-day wave signatures in the mesosphere-lower thermosphere (MLT) and in ionospheric Sq currents besides deciphering their effects on the overall neutral dynamics at low latitudes. Analysis extended to longitudinally separated stations confirms the penetration of these planetary waves into the ionosphere either directly or indirectly through interaction with other wave modes in the MLT region.

How to cite: Jadhav, A., Subramanian, G., and Patil, P.: Planetary wave activity observed in atmosphere-ionosphere system over low latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9390, https://doi.org/10.5194/egusphere-egu22-9390, 2022.

EGU22-10900 | Presentations | ST3.6

Multi-step vertical coupling from the troposphere to the thermosphere due to gravity waves 

Erich Becker, Sharon L. Vadas, Larisa Goncharenko, and V. Lynn Harvey

Multi-step vertical coupling (MSVC) describes a paradigm shift regarding the role of gravity waves (GWs) in the winter middle and upper atmosphere. It is well known that primary GWs propagate into the winter stratosphere and lower mesosphere, where they dissipate. However, since this process is localized in space and intermittent, secondary GWs are generated. These propagate into the lower thermosphere, dissipate, and generate tertiary GWs and so forth. Recent modeling and observational studies showed that secondary and tertiary GWs from MSVC are the predominant GWs in the upper mesosphere and in the thermosphere during wintertime. MSVC cannot be simulated with GW parameterizations as used in conventional whole atmosphere models.

In this presentation, we describe the HIgh Altitude Mechanistic general Circulation Model (HIAMCM), which resolves medium-scale GWs from the surface up to z~450 km, including MSVC induced by primary GWs from jets, fronts, and orography. This is made possible by combining a sufficiently high spatial resolution with advanced methods for turbulent and molecular diffusion. Furthermore, the HIAMCM can be nudged to MERRA-2 reanalysis in the troposphere and stratosphere. The nudging is performed in spectral space and restricted to horizontal wavelenghs larger than ~1500-2000 km. As a result, the generation, propagation, and dissipation of resolved GWs is not affected by the nudging and simulated like in the free-running model. We present recent applications of the HIAMCM regarding 1) the role of secondary GWs in the winter polar mesopause region, 2) the wintertime thermospheric GW hotspot over the Southern Andes/Antarctic Peninsula, and 3) the southward propagation of thermospheric GWs during daytime (as a driver for corresponding traveling ionospheric disturbances). Furthermore, we contrast the MSVC during the strong polar vortex period in December 2016 to the MSVC during the sudden stratospheric warming in January/February 2017.

How to cite: Becker, E., Vadas, S. L., Goncharenko, L., and Harvey, V. L.: Multi-step vertical coupling from the troposphere to the thermosphere due to gravity waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10900, https://doi.org/10.5194/egusphere-egu22-10900, 2022.

EGU22-10996 | Presentations | ST3.6

Enhanced Quasi-6-Day Wave during the 2019 Southern Hemisphere SSW and its modulation of diurnal tides and gravity waves 

Zishun Qiao, Alan Z. Liu, Nick Pedatella, Gunter Stober, Iain Reid, Javier Fuentes, and Chris Adami

A newly established multi-static meteor radar network, CONDOR (31.2ºS,70.0ºW), provides the capability to resolve wind and temperature oscillations over a broad range of periods, calculate E-P flux of planetary waves and investigate the short-term variability in the 80-100 km MLT region. In this study we present results of an enhanced westward wavenumber 1 Q6DW activity and its modulation with the amplified diurnal tides and gravity waves (GW) meridional wind variance during a rare minor SH SSW in 2019, using two SH midlatitude meteor radar observations and a recently developed 3DVAR algorithm. This algorithm creates a tomographic reconstruction of the 3D wind field based on optimal estimation technique and Bayesian statistics and is particularly suitable for investigating GW dynamics on regional scales. Furthermore, we present the first results of meteor radar observed Q6DW E-P flux and its comparison with SD-WACCM-X simulated Q6DW E-P flux. The encouraging agreement demonstrated that this SSW-related Q6DW activity had a significant impact on the dynamically coupled MLT region at SH midlatitude.

How to cite: Qiao, Z., Liu, A. Z., Pedatella, N., Stober, G., Reid, I., Fuentes, J., and Adami, C.: Enhanced Quasi-6-Day Wave during the 2019 Southern Hemisphere SSW and its modulation of diurnal tides and gravity waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10996, https://doi.org/10.5194/egusphere-egu22-10996, 2022.

EGU22-11327 | Presentations | ST3.6

Migrating solar diurnal tidal variability during Northern and Southern Hemisphere Sudden Stratospheric Warmings 

Tarique Adnan Siddiqui, Claudia Stolle, and Yosuke Yamazaki

In this study, the variability of migrating solar diurnal (DW1) tide in the mesosphere-lower thermosphere (MLT) region during Northern and Southern Hemisphere (NH & SH) Sudden Stratospheric Warmings (SSWs) is investigated using Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature  observations and reanalysis-driven Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) simulations. The periods examined include four major NH SSWs that occurred during January in 2006, 2009, 2010 and 2013 and two SH SSWs that were recorded in September in 2002 and 2019. Our analysis shows that the observed DW1 tide displays a marked decline in the equatorial region after the onset of NH and SH SSWs. As WACCM-X simulations qualitatively reproduce this feature of DW1 tidal variability common to both NH and SH SSWs, they have been used to examine the possible mechanism that could explain these observations in DW1 tide. It is known that changes in the latitudinal shear of zonal winds at low-latitudes strongly affect the seasonal variation of DW1 tide in the MLT. We explore this mechanism to show that SSW-associated changes in the latitudinal shear in the MLT could be used to explain the observed variability of DW1 tide during NH and SH SSWs.

How to cite: Siddiqui, T. A., Stolle, C., and Yamazaki, Y.: Migrating solar diurnal tidal variability during Northern and Southern Hemisphere Sudden Stratospheric Warmings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11327, https://doi.org/10.5194/egusphere-egu22-11327, 2022.

EGU22-11510 | Presentations | ST3.6

Response of the traveling planetary waves at low latitude middle atmosphere during September 2019 minor sudden stratospheric warming 

Gourav Mitra, Amitava Guharay, Paulo Batista, and Ricardo Buriti

Planetary wave (PW) associated dynamical variability in the equatorial and extratropical middle atmosphere during the September 2019 Southern hemisphere minor sudden stratospheric warming (SSW) is investigated utilizing meteor radar wind observations from São João do Cariri (7.4°S, 36.5°W) and Cachoeira Paulista (22.7°S, 45°W) and reanalysis data. Signature of the mesospheric warming in conjunction with the stratospheric cooling is found at low latitudes. The strong westerly wind at low latitudes decelerates notably near 65 km at the onset of the warming episode, although no wind reversal is observed. The wind spectra reveal a prevalent quasi-16-day wave (Q16DW) prior to the SSW and existence of a quasi-6-day wave (Q6DW) after the warming event. Possible existence of barotropic/baroclinic instability in the low and mid latitude middle atmosphere may be responsible for exciting the Q6DW. The traveling PW is primarily found to travel westward corresponding to zonal wavenumber 1 and 2. Furthermore, significant latitudinal mixing of airmass between the tropics and high latitudes is evident in the potential vorticity map. The Eliassen-Palm flux diagnosis shows the propagation of the Q6DW and Q16DW from mid to low latitudes during the warming event.

How to cite: Mitra, G., Guharay, A., Batista, P., and Buriti, R.: Response of the traveling planetary waves at low latitude middle atmosphere during September 2019 minor sudden stratospheric warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11510, https://doi.org/10.5194/egusphere-egu22-11510, 2022.

EGU22-62 | Presentations | PS2.2

Full-kinetic global simulations of the plasma environment at Mercury: a model from planetary to electrons scales to support BepiColombo 

Federico Lavorenti, Pierre Henri, Francesco Califano, Jan Deca, Sae Aizawa, and Nicolas Andre

Mercury is the only telluric planet of the solar system, other than Earth, with an intrinsic magnetic field. Thus, the Hermean surface is shielded from the impinging solar wind via the presence of an “Earth-like” magnetosphere. However, this cavity is twenty times smaller than its alike at the Earth. The relatively small extension of the Hermean magnetosphere enables us to model it using global full-kinetic simulation with the aid of modern supercomputers. Such modeling is crucial to interpret, and prepare, the future observations of the ongoing joint ESA-JAXA mission BepiColombo.

The model used in this work is based on three-dimensional, implicit full-PIC simulations of the interaction between the solar wind and Mercury’s magnetosphere (i.e. at 0.3-0.47 AU). This model includes self-consistently the ion and electron physics down to kinetic electron scales. On top of that, we show comparisons between in-situ observations by Mariner-X and BepiColombo space missions. This comparison allows us (i) to validate our model and (ii) to gain insights into the electron dynamics in the Hermean environment, thought to be governed by kinetic-scale processes.

First, we validate our model through a qualitative comparison between three-dimensional outcomes of our global simulations and the ones of reduced fluid/hybrid simulations (in the context of the SHOTS collaboration). Moreover, comparison with in-situ Mariner-X observations during its first Mercury flyby complete the validation of our model. Second, we study the global dynamics of electrons showing regions where strongest particle acceleration/energization occurs, giving quantitative estimate of electron temperature anisotropy in the Hermean environment. Such results are used to interpret past, and plan future, BepiColombo in-situ observations.

How to cite: Lavorenti, F., Henri, P., Califano, F., Deca, J., Aizawa, S., and Andre, N.: Full-kinetic global simulations of the plasma environment at Mercury: a model from planetary to electrons scales to support BepiColombo, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-62, https://doi.org/10.5194/egusphere-egu22-62, 2022.

EGU22-169 | Presentations | PS2.2

On the Growth and Development of Non-linear Kelvin-Helmholtz Instability at Mars: MAVEN Observations 

Gangkai Poh, Jared Espley, Katariina Nykyri, Christopher Fowler, Xuanye Ma, Shaosui Xu, Gwen Hanley, Norberto Romanelli, Charles Bowers, Jacob Gruesbeck, and Gina DiBraccio

We analyzed MAVEN observations of fields and plasma signatures associated with an encounter of fully-developed Kelvin–Helmholtz (K–H) vortices at the northern polar terminator along Mars’ induced magnetosphere boundary. The signatures of the K–H vortices event are: (i) quasi-periodic, “bipolar-like” sawtooth magnetic field perturbations, (ii) corresponding density decrease, (iii) tailward enhancement of plasma velocity for both protons and heavy ions, (iv) co-existence of magnetosheath and planetary plasma in the region prior to the sawtooth magnetic field signature (i.e. mixing region of the vortex structure), and (v) pressure enhancement (minimum) at the edge (center) of the sawtooth magnetic field signature. Our results strongly support the scenario for the non-linear growth of K–H instability along Mars’ induced magnetosphere boundary, where a plasma flow difference between the magnetosheath and induced-magnetospheric plasma is expected. Our findings are also in good agreement with 3-dimensional local magnetohydrodynamics (MHD) simulation results. MAVEN observations of protons with energies greater than 10 keV and results from the Walén analyses suggests the possibility of particle energization within the mixing region of the K–H vortex structure via magnetic reconnection, secondary instabilities or other turbulent processes. We estimated the lower limit on the K–H instability linear growth rate to be ~5.84 x 10-3 s-1. For these vortices, we estimate the lower limit of the instantaneous atmospheric ion escape flux due to the detachment of plasma clouds during the late non-linear stage of K–H instability to be ~5.90 x 1026 particles/s, which is agrees with earlier studies for the Venusian plasma clouds but ~two orders of magnitude larger than that calculated for Mars. 

How to cite: Poh, G., Espley, J., Nykyri, K., Fowler, C., Ma, X., Xu, S., Hanley, G., Romanelli, N., Bowers, C., Gruesbeck, J., and DiBraccio, G.: On the Growth and Development of Non-linear Kelvin-Helmholtz Instability at Mars: MAVEN Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-169, https://doi.org/10.5194/egusphere-egu22-169, 2022.

EGU22-653 | Presentations | PS2.2

Proton Temperature Anisotropies in the Venus Plasma Environment during Solar Minimum and Maximum 

Sebastián Rojas Mata, Gabriella Stenberg Wieser, Yoshifumi Futaana, Alexander Bader, Moa Persson, Andrey Fedorov, and Tielong Zhang

Venus’ lack of an intrinsic magnetic field allows the solar wind to closely interact with its atmosphere [1], making it a
prime target for investigating how unmagnetized atmospheric bodies in our Solar System [2] or elsewhere [3] interact
with magnetized plasma flows. This close interaction means that solar-activity correlations exhibited by the solar wind and
other heliospheric parameters [4, 5] cause solar-cycle variations in Venus’ plasma environment and plasma phenomena. We
investigate these variations by characterizing the proton population around Venus during periods of solar minimum (2006–2009)
and maximum (2010–2014). We use data from the Ion Mass Analyser (IMA) instrument, a particle mass-energy spectrometer
which was onboard the Venus Express (VEX) mission. We apply a previously developed methodology which fits Maxwellian
models to measurements of the protons’ velocity distribution functions [6] to produce statistical distributions of bulk speeds and
temperatures in various regions of Venus’ plasma environment. We also present spatial maps and probability-density histograms
comparing the proton parameters between the two time periods.
We find that the temperatures perpendicular (T) and parallel (T) to the background magnetic field are 20–35% lower
in the magnetosheath during solar maximum. This suggests that the heating of particles as they cross the bow shock varies
between the two time periods. We also find that the regions in the magnetosheath with highest temperature ratio T/T are
farther downstream from the bow shock during solar maximum than minimum. This is consistent with previous observations of
how mirror-mode structures presumably generated at the bow shock strictly decay as they are convected into the magnetosheath
during solar minimum, whereas during solar maximum they first grow and then decay [7]. We also present ongoing work to
further characterize the plasma environment as a function of upstream solar-wind parameters (such as Mach number or cone
angle) and bow shock geometry. We discuss preliminary results concerning energy conversion processes at Venus’ bow shock.


REFERENCES
[1] Y. Futaana, G. Stenberg Wieser et al., “Solar Wind Interaction and Impact on the Venus Atmosphere,” Space Science Reviews, vol. 212, no. 3-4, 2017.
[2] C. Bertucci, F. Duru et al., The induced magnetospheres of mars, venus, and titan, 2011, vol. 162, no. 1-4.
[3] C. Dong, M. Jin et al., “Atmospheric escape from the TRAPPIST-1 planets and implications for habitability,” Proceedings of the National Academy of
Sciences of the United States of America, vol. 115, no. 2, 2017.
[4] C. T. Russell, E. Chou et al., “Solar and interplanetary control of the location of the Venus bow shock,” Journal of Geophysical Research, vol. 93, no. A6, 1988.
[5] P. R. Gazis, “Solar cycle variation in the heliosphere,” Reviews of Geophysics, vol. 34, no. 3,  1996.
[6] A. Bader, G. Stenberg Wieser et al., “Proton Temperature Anisotropies in the Plasma Environment of Venus,” Journal of Geophysical Research: Space
Physics, vol. 124, no. 5, 2019.
[7] M. Volwerk, D. Schmid et al., “Mirror mode waves in Venus’s magnetosheath: Solar minimum vs. solar maximum,” Annales Geophysicae, vol. 34, no. 11, 2016.

How to cite: Rojas Mata, S., Stenberg Wieser, G., Futaana, Y., Bader, A., Persson, M., Fedorov, A., and Zhang, T.: Proton Temperature Anisotropies in the Venus Plasma Environment during Solar Minimum and Maximum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-653, https://doi.org/10.5194/egusphere-egu22-653, 2022.

In 2020 and 2021 both BepiColombo and Solar Orbiter used Venus for a gravity assist in order to reach Mercury and to finally get into the correct orbit around the Sun, respectively. These flybys were the first since Mariner 10 to sample a long stretch, more than 30 Venus radii of the induced magnetotail of Venus. This brought the opportunity to study the structure and dynamics of the tail during different solar wind conditions. On this poster we will discuss the differences and also the similarities (even though the four flybys took different trajectories through the induced magnetotail) using the magnetometers on both spacecraft. Field line draping, magnetic reconnection, and plasma waves will all pass by on stage.

How to cite: Volwerk, M. and the The VenusMagTeam: Two Spacecraft, Four Flythroughs: Magnetometer Measurements by BepiColombo and Solar Orbiter in the Induced Magnetotail of Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-822, https://doi.org/10.5194/egusphere-egu22-822, 2022.

EGU22-1609 | Presentations | PS2.2

Ranking the drivers of the Martian bow shock location: a statistical analysis of Mars Atmosphere and Volatile EvolutioN and Mars Express observations 

Philippe Garnier, Christian Jacquey, Xavier Gendre, Vincent Génot, Christian Mazelle, Xiaohua Fang, Jacob Gruesbeck, Beatriz Sanchez-Cano, and Jasper Halekas

The Martian interaction with the solar wind leads to the formation of a bow shock upstream of the planet. The shock dynamics appears complex, due to the combined influence of external (solar photons, solar wind plasma and fields) and internal (crustal magnetic fields, ionized atmosphere) drivers. The extreme ultraviolet fluxes and magnetosonic mach number are known major drivers of the shock location, while the influence of other possible drivers is less constrained or unknown such as crustal magnetic fields or the solar wind dynamic pressure and the Interplanetary Magnetic Field (IMF) intensity and orientation.

We analyze and rank the influence of the main drivers of the Martian shock location, based on published datasets from Mars Express and Mars Atmosphere Volatile EvolutioN missions and on several methods such as the Akaike Information Criterion, Least Absolute Shrinkage Selection Operator regression, and partial correlations. We include here the influence of the crustal fields, extreme ultraviolet fluxes, magnetosonic mach number, solar wind dynamic pressure and various Interplanetary Magnetic Field parameters (intensity and orientation angles).

We conclude that the major drivers of the shock location are extreme ultraviolet fluxes and magnetosonic mach number, while crustal fields and solar wind dynamic pressure are secondary drivers at a similar level. The IMF orientation also plays a significant role, with larger distances for perpendicular shocks rather than parallel shocks.

How to cite: Garnier, P., Jacquey, C., Gendre, X., Génot, V., Mazelle, C., Fang, X., Gruesbeck, J., Sanchez-Cano, B., and Halekas, J.: Ranking the drivers of the Martian bow shock location: a statistical analysis of Mars Atmosphere and Volatile EvolutioN and Mars Express observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1609, https://doi.org/10.5194/egusphere-egu22-1609, 2022.

EGU22-1814 | Presentations | PS2.2

A Fully Kinetic Perspective on Weakly Active Comets: Symmetric versus Asymmetric Outgassing 

Jan Deca, Peter Stephenson, Andrey Divin, Pierre Henri, and Marina Galand

For more than two years, ESA’s Rosetta mission measured the complex and ever-evolving plasma environment surrounding comet 67P/Churyumov-Gerasimenko. In this work, we explore the structure and dynamics of the near-comet plasma environment at steady state, comparing directly the results of a spherically symmetric Haser model and an asymmetric outgassing profile based on the measurements from the ROSINA instrument onboard Rosetta during 67P’s weakly outgassing stages. Using a fully kinetic semi-implicit particle-in-cell code, we are able to characterise (1) the various ion and electron populations and their interactions, and (2) the implications to the mass-loading process caused by taking into account asymmetric outgassing. Our model complements observations by providing a full 3D picture that is directly relevant to help interpret the measurements made by the Rosetta Plasma Consortium instruments. In addition, understanding such details better is key to help disentangle the physical drivers active in the plasma environment of comets visited by future exploration missions.

How to cite: Deca, J., Stephenson, P., Divin, A., Henri, P., and Galand, M.: A Fully Kinetic Perspective on Weakly Active Comets: Symmetric versus Asymmetric Outgassing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1814, https://doi.org/10.5194/egusphere-egu22-1814, 2022.

EGU22-1821 | Presentations | PS2.2

First evidence of carbon escape through Venus magnetosheath along draped magnetic field lines 

Lina Hadid and the MSA, MIA and MEA teams

On August 10, 2021, the Mercury-bound BepiColombo spacecraft flew for the second time by Venus for a Gravity-Assist Maneuver. During this second flyby of Venus, a limited number of instruments were turned on, allowing unique observations of the planet and its environment. Among these instruments, the Mass Spectrum Analyzer (MSA) that is part of the particle analyzer consortium onboard the magnetospheric orbiter (Mio) was able to acquire its first plasma composition measurements in space. As a matter of fact, during a limited time interval upon approach of the planet, substantial ion populations were recorded by MSA, with characteristic energies ranging from about 20 eV up to a few hundreds of eVs. Comparison of the measured Time-Of-Flight spectra with calibration data reveals that these populations are of planetary origin, containing both Oxygen and Carbon ions. The Oxygen observations are to some extent consistent with previous in situ measurements from mass spectrometers onboard Venus Express and Pioneer Venus Orbiter. On the other hand, the MSA data provide the first ever in situ evidences of Carbon ions in the near-Venus environment at about 6 planetary radii. We show that the abundance of C+ amounts to about ~30% of that of O+. Furthermore, the fact that photoelectrons are simultaneously observed with the low energy planetary ions indicate a magnetic connection to the dayside ionosphere from which ions are ejected under the effect of the ambipolar electrostatic field.

How to cite: Hadid, L. and the MSA, MIA and MEA teams: First evidence of carbon escape through Venus magnetosheath along draped magnetic field lines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1821, https://doi.org/10.5194/egusphere-egu22-1821, 2022.

EGU22-2181 | Presentations | PS2.2

Numerical prediction of the effects of solar energetic particle precipitation on the Martian atmospheric chemical composition 

Yuki Nakamura, Naoki Terada, Francois Leblanc, Hiromu Nakagawa, Shotaro Sakai, Sayano Hiruba, Ryuho Kataoka, and Kiyoka Murase

Solar energetic particles (SEPs) are high-energetic particles that consist mainly of electrons and protons with energies from a few tens of keV to GeV ejected  associated with solar flares and coronal mass ejections. SEPs can precipitate into planetary atmospheres cause ionization, excitation and dissociation of atmospheric molecules, leading to changes in atmospheric chemical composition via chemical network [e.g. Solomon et al., 1981; Adams et al., 2021].

The effect of SEPs on ozone concentration in the Earth’s polar region has been intensively studied for the past decades. For instance, during the enormous solar flare that occurred in late October 2003, NOx and HOx concentrations were enhanced and ozone concentration was depleted by 40% at the polar lower mesosphere [e.g. Jackman et al., 2005]. Increased ionization and dissociation of atmospheric N2 and O2molecules led to the production of NOx and HOx, which catalytically destroyed ozone at the polar mesosphere.

Recently, the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft has discovered global diffuse aurora on the nightside of Mars down to few tens km in altitude during SEP events, indicating that a significant amount of energy could be deposited in the atmosphere deeper than previously thought  [Schneider et al., 2015; Nakamura et al., 2022]. However, the effects of SEPs on the atmospheric chemistry of present-day Mars have not yet been investigated by observations and/or models.

By coupling a Monte Carlo model PTRIP (Nakamura et al., 2022) and a newly developed photochemical model to investigate the effects of SEPs on the atmospheric compositions at Mars, we performed a simulation to track the effects of a large SEP event on the Martian atmospheric composition. We found that HOx increased by a factor of 10 and ozone decreased by a factor of 10 in the altitude range from 20 km to 60 km. This is the very first estimation of the effects of SEPs on the atmospheric neutral compositions at Mars, indicating that similar effects on HOx and ozone could be expected on Mars than on Earth.

How to cite: Nakamura, Y., Terada, N., Leblanc, F., Nakagawa, H., Sakai, S., Hiruba, S., Kataoka, R., and Murase, K.: Numerical prediction of the effects of solar energetic particle precipitation on the Martian atmospheric chemical composition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2181, https://doi.org/10.5194/egusphere-egu22-2181, 2022.

EGU22-2853 | Presentations | PS2.2

Exploring the solar wind-planetary interaction at Mars: Implication for Magnetic Reconnection 

Charles F. Bowers, Gina A. DiBraccio, James A. Slavin, Jacob R. Gruesbeck, Tristan Weber, Norberto Romanelli, Abigail R. Azari, and Shaosui Xu

The Martian crustal magnetic anomalies create a varied, asymmetric obstacle for the draped interplanetary magnetic field (IMF) to interact with. One possible result of this interaction is magnetic reconnection, a process by which anti-parallel magnetic field lines connect and reconfigure, transferring energy into the surrounding environment and mixing previously separated plasma populations. Here, we present an analysis to determine the draped IMF conditions that favor reconnection with the underlying crustal anomalies at Mars. First, we plot a map of the crustal anomalies’ strength and orientation compiled from magnetic field data taken throughout the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Second, we create “shear maps” which calculate and plot the angle of shear between the transverse component of the anomalies and a chosen overlaid draping direction. Third, we define a “shear index” which quantifies the susceptibility of a particular region to undergo reconnection based on a given draped IMF orientation and the resulting shear map for that region. We then compare the shear index for a variety of draped field orientations within different regions of the Martian magnetosphere. Our results suggest eastward/westward (horizontal) draped fields present regions that are more likely for anti-parallel magnetic reconnection to occur with the crustal anomalies than northward/southward (vertical) draped fields, with one notable exception being the strongest crustal anomalies located in the southern hemisphere ~180° longitude. An east/west draped field roughly corresponds to a +/- By IMF direction on the dayside, implying the rate of magnetic reconnection on the dayside of Mars may be enhanced for IMF field lines pointing in the +/- YMSO direction compared to that of IMF field lines pointing in the +/- ZMSO direction, with MSO referring to the Mars Solar Orbital coordinate system. Understanding the interplay between Mars’s crustal magnetic fields and the IMF is crucial to answer outstanding science questions regarding nightside magnetospheric activity at Mars, namely how IMF orientation affects the twisting of the magnetotail, open magnetic topology observations on the nightside, and discrete aurora observations in the southern hemisphere.

How to cite: Bowers, C. F., DiBraccio, G. A., Slavin, J. A., Gruesbeck, J. R., Weber, T., Romanelli, N., Azari, A. R., and Xu, S.: Exploring the solar wind-planetary interaction at Mars: Implication for Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2853, https://doi.org/10.5194/egusphere-egu22-2853, 2022.

EGU22-3658 | Presentations | PS2.2

Solar Orbiter Data-Model Comparison in Venus' Induced Magnetotail 

Katerina Stergiopoulou, Riku Jarvinen, David J. Andrews, Niklas J.T. Edberg, Andrew P. Dimmock, Esa Kallio, and Yuri Khotyaintsev

We investigate the Venusian magnetotail and its boundaries utilising magnetic field and density measurements that cover a wide range of radial distances, from the two geometrically similar Solar Orbiter Venus flybys on 27 December 2020 and 9 August 2021. We look at the magnetic field components along the spacecraft trajectory in an attempt to identify boundary crossings, as well as the extent and intensity of the bowshock deep in the magnetotail. We compare these observations with results of a simulation of the induced magnetosphere and magnetotail of Venus, where the initial upstream conditions are provided by Solar Orbiter measurements, to examine in what degree the simulation representation agrees with the observations. The model encloses a massive volume of 80RV x 60RV x 60RV  in which we look at magnetic field and proton density variations. Additionally, we vary the rotation of the clock angle in order to find for which rotation angle we get the best match with the observations during the different steps of the spacecraft's trajectory. 

How to cite: Stergiopoulou, K., Jarvinen, R., Andrews, D. J., Edberg, N. J. T., Dimmock, A. P., Kallio, E., and Khotyaintsev, Y.: Solar Orbiter Data-Model Comparison in Venus' Induced Magnetotail, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3658, https://doi.org/10.5194/egusphere-egu22-3658, 2022.

EGU22-4000 | Presentations | PS2.2

Influence of planetary space weather on the shapes of Venus plasma boundaries 

Claire Signoles, Moa Persson, Alexander Wolff, Nicolas Martinez, Viktor Lindwall, Yoshifumi Futaana, Sebastian Rojas-Mata, Tielong Zhang, Nicolas André, Sae Aizawa, and Andrei Fedorov

As Venus does not have an intrinsic magnetic field, the solar wind interacts directly with the Venusian atmosphere, altering its structure and composition, for example through atmospheric ion escape to space. In particular, the interaction will result in the formation of plasma boundaries, which separate regions of different plasma populations around Venus. Knowing how space weather influences the shape of these boundaries is one of the key pieces to understanding the current state of the Venusian atmosphere.

During its eight years mission, including more than 3000 orbits around Venus, Venus Express made measurements of the plasma environment, covering a wide range of upstream conditions. Using conjoint plasma and magnetic field measurements from the ASPERA-4 (Analyser of Space Plasma and Energetic Atoms) and the magnetometer instruments, we identified the locations where the spacecraft crossed the bow shock and the ion composition boundary for each orbit. Using the derived dataset, we then determined the boundary shapes with a two-parameter fit. The boundary shape fittings were done with respect to one or multiple upstream conditions.

Here we report that both boundaries are highly dependent on solar wind extreme ultraviolet (EUV) flux, expanding further from the planet at solar maximum. A likely explanation is that at solar maximum, combined heating of the exosphere ions and a higher photoionization rate lead to a higher planetary ion production. These additional ions increase the internal thermal pressure, pushing the boundaries outward.

Additionally, at solar minimum, solar wind parameters like dynamic pressure and energy flux were found to not affect the shape of the bow shock, which is consistent with previous studies. The influence of the strength and orientation of the interplanetary magnetic field, the Mach number, and potential correlations between multiple upstream parameters, are also discussed in this talk.

How to cite: Signoles, C., Persson, M., Wolff, A., Martinez, N., Lindwall, V., Futaana, Y., Rojas-Mata, S., Zhang, T., André, N., Aizawa, S., and Fedorov, A.: Influence of planetary space weather on the shapes of Venus plasma boundaries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4000, https://doi.org/10.5194/egusphere-egu22-4000, 2022.

EGU22-4175 | Presentations | PS2.2

LatHyS hybrid simulation of the August, 10 2021 BepiColombo Venus flyby 

Sae Aizawa, Moa Persson, Thibault Menez, Nicolas Andre, Ronan Modolo, Alain Barthe, Emmanuel Penou, Andrei Fedorov, Jean-Andre Sauvaud, Francois Leblanc, Jean-Yves Chaufray, Yoshifumi Saito, Shoichiro Yokota, Go Murakami, Vincent Genot, Beatriz Sanchez-Cano, Daniel Heyner, Tim Horbury, Philippe Louarn, and Christopher Owen

The 2nd Venus flyby of BepiColombo has been examined and compared by the newly developed global hybrid simulation LatHyS for the Venusian environment. The LatHyS has been first validated by comparison with Venus Express observations, then using the observation from Solar Orbiter, which was located in the upstream region and both observed the same solar wind, it is applied for the Venus flyby. The simulation successfully reproduced the observed signatures and it shows that BepiColombo passed through the stagnation region of Venus, which supports the results obtained by data-analysis. In addition, we have sampled the plasma information along the trajectory and constructed the energy spectrum for three species (solar wind proton, planetary proton, and planetary oxygen ion) and possible effect due to the limited field of view is discussed. Moreover, ion escape from Venus for planetary species have been discussed and the escape rate is estimated. 

How to cite: Aizawa, S., Persson, M., Menez, T., Andre, N., Modolo, R., Barthe, A., Penou, E., Fedorov, A., Sauvaud, J.-A., Leblanc, F., Chaufray, J.-Y., Saito, Y., Yokota, S., Murakami, G., Genot, V., Sanchez-Cano, B., Heyner, D., Horbury, T., Louarn, P., and Owen, C.: LatHyS hybrid simulation of the August, 10 2021 BepiColombo Venus flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4175, https://doi.org/10.5194/egusphere-egu22-4175, 2022.

EGU22-4289 | Presentations | PS2.2

Space Weather detections with housekeeping sensors onboard Mars Express, Rosetta, BepiColombo and Solar Orbiter 

Beatriz Sanchez-Cano, Olivier Witasse, Elise W. Knutsen, Dikshita Meggi, Mark Lester, and Robert F. Wimmer-Schweingruber and the ESA mission teams

While space weather has been a growing field of research and applications over the last 15-20 years, “planetary space weather” is an emerging discipline. In fact, as long as we expand our robotic exploration within the solar system, monitoring planetary space weather is becoming more necessary than ever. Despite this, not every spacecraft is designed for plasma science and only a few of them have the necessary plasma instrumentation for space weather purposes. However, all of them have thousands of housekeeping detectors distributed along the spacecraft. In particular, energetic particles impact detectors and subsystems on a spacecraft and their effects can be identified in selected housekeeping data sets, such as the Error detection and correction (EDAC) counters. In this study, we investigate these engineering datasets for scientific purposes by performing the first feasibility study of solar energetic particle detection using EDAC counters from several available ESA Solar System missions, such as Mars Express, Rosetta, BepiColombo and Solar Orbiter. In order to validate the results, these detections are compared to other observations from scientific instruments on board these missions. Moreover, the potential implications of space weather event detections based on EDAC sensors at Mars and Comet 67P/Churyumov-Gerasimenko is analysed. This study has the potential to provide a good network of solar particle observations at locations where no scientific observations of this kind are available.

How to cite: Sanchez-Cano, B., Witasse, O., Knutsen, E. W., Meggi, D., Lester, M., and Wimmer-Schweingruber, R. F. and the ESA mission teams: Space Weather detections with housekeeping sensors onboard Mars Express, Rosetta, BepiColombo and Solar Orbiter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4289, https://doi.org/10.5194/egusphere-egu22-4289, 2022.

EGU22-4455 | Presentations | PS2.2

Estimating heavy ions escape rate from Mars using hybrid model and observations from MAVEN 

Qi Zhang, Mats Holmström, Xiaodong Wang, and Shahab Fatemi

We apply a new method, coupling a hybrid plasma model (ions as particles, electrons as a fluid) and measurements from the Mars Atmosphere and Volatile Evolution (MAVEN) mission, to calculate heavy ion escape rates from Mars. With this method, we acquire estimates of the escape rate orbit by orbit in different upstream conditions. We have investigated how the estimated ion escape depends on the assumed composition of heavy ions, the solar wind velocity aberration and the amount of alpha particles in the solar wind. We also estimate the amount of tail escape and radial escape and compare the model results with  recent Mars Express and MAVEN studies.

How to cite: Zhang, Q., Holmström, M., Wang, X., and Fatemi, S.: Estimating heavy ions escape rate from Mars using hybrid model and observations from MAVEN, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4455, https://doi.org/10.5194/egusphere-egu22-4455, 2022.

EGU22-5255 | Presentations | PS2.2

Global hybrid modeling of ultra-low frequency solar wind foreshock waves at Mercury, Venus and Mars 

Riku Jarvinen, Esa Kallio, and Tuija Pulkkinen

We study the solar wind interactions of Mercury, Venus and Mars in a global hybrid model, where ions are treated as particles and electrons form a charge-neutralizing fluid. We concentrate on the formation of large-scale, ultra-low frequency (ULF) waves in planetary ion foreshocks and their dependence on solar wind and interplanetary magnetic field conditions in the inner solar system. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is small enough. The magnetic connection to the bow shock allows the backstreaming of solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter bow shock and transmit in the downstream region. The analyzed simulation runs use more than two hundred simulation particles per cell on average to allow fine enough velocity space resolution for resolving the foreshocks and waves self-consistently. We find significant differences in wave and foreshock properties between these three planets and discuss their causes.

How to cite: Jarvinen, R., Kallio, E., and Pulkkinen, T.: Global hybrid modeling of ultra-low frequency solar wind foreshock waves at Mercury, Venus and Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5255, https://doi.org/10.5194/egusphere-egu22-5255, 2022.

EGU22-5413 | Presentations | PS2.2

Mirror mode-like structures around unmagnetised planets: a comparison between the magnetosheaths of Mars and Venus 

Cyril Simon Wedlund, Martin Volwerk, Christian Mazelle, Sebastián Rojas Mata, Gabriella Stenberg Wieser, David Mautner, Jasper Halekas, Jared Espley, Diana Rojas-Castillo, Christian Möstl, and César Bertucci

Mirror mode structures arise whenever a temperature anisotropy is present in the plasma, classically in the wake of the bow shock in a quasi-perpendicular configuration with respect to the interplanetary magnetic field, or from pickup ion distribution effects. Born from space plasma instabilities and in competition with other wave modes, these ultra-low frequency waves contribute to energy exchanges between the different plasma populations present in the magnetosheath. At Mars and Venus, such structures have very similar scales: they last typically a few tens of seconds and appear as peaks or dips in the magnetic field data in antiphase with the local plasma density variations. As magnetometers are present on many space missions, magnetic field-only criteria are an ideal tool to study these structures across different magnetosheath environments. We present here for the first time a comparison of the statistical occurrence of magnetosheath mirror mode-like structures at Mars with MAVEN and at Venus with Venus Express. Based on magnetic field-only measurements, we use identical detection criteria at both planets to select quasi-linear structures in B-field measurements. We then present two-dimensional maps of mirror mode-like occurrence rates with respect to solar cycle variations and EUV flux levels, atmospheric seasons (for Mars) and the nature of the shock crossing (quasi-parallel or quasi-perpendicular configurations), and compare them between planets. Finally, we discuss ambiguities in the nature of the detected structures and their global effects on the magnetosheath.

How to cite: Simon Wedlund, C., Volwerk, M., Mazelle, C., Rojas Mata, S., Stenberg Wieser, G., Mautner, D., Halekas, J., Espley, J., Rojas-Castillo, D., Möstl, C., and Bertucci, C.: Mirror mode-like structures around unmagnetised planets: a comparison between the magnetosheaths of Mars and Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5413, https://doi.org/10.5194/egusphere-egu22-5413, 2022.

EGU22-5627 | Presentations | PS2.2

Cometosheath observations around comet 67P/Churyumov-Gerasimenko 

Hayley Williamson, Hans Nilsson, Gabriella Stenberg Wieser, and Anja Moeslinger

The Rosetta spacecraft orbited the comet 67P/Churuymov-Gerasimenko for approximately two years, primarily remaining close to the nucleus, unlike previous cometary flyby missions. The combination of Rosetta's close orbit and comet 67P's relatively low cometary activity make detections of the bow shock difficult. However, magnetosheath-like proton distributions have been observed, indicating Rosetta indeed was downstream of a bow shock, during periods of higher cometary activity. Here, we search the Ion Composition Analyzer (ICA) data for additional evidence of the cometosheath, the region downstream of the bow shock analogous to a magnetosheath. We examine the proton velocity distributions for high time and spatial variability that is not correlated with changes in the electric or magnetic fields. We present an overview of cometosheath detections and a discussion of the relation between the cometosheath and bow shock properties. Other work shows that the electric potential of the solar wind can be retrieved from the differential slowing of the solar wind species, so we compare time periods with a high electric potential to cometosheath detections, as a high potential can also indicate shock formation.

How to cite: Williamson, H., Nilsson, H., Stenberg Wieser, G., and Moeslinger, A.: Cometosheath observations around comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5627, https://doi.org/10.5194/egusphere-egu22-5627, 2022.

EGU22-5648 | Presentations | PS2.2

Observation of dual proton populations by the Rosetta Ion Composition Analyser 

Anja Moeslinger, Hans Nilsson, Gabriella Stenberg Wieser, and Hayley Williamson

During Rosetta’s 2-year observation period of comet 67P/Churyumov-Gerasimenko, the Ion Composition Analyser (ICA) continuously measured the plasma environment around the comet. The interaction of the solar wind with the cometary plasma and the evolution of the observed solar wind over the course of the mission has been subject of previous studies. It usually shows a single proton population with a large anti-sunward component that gets more and more deflected when the comet approaches perihelion. 

In this study we focus on ICA data obtained during the 19th of April 2016, where we detected two clear peaks in the energy spectra of the proton population. For the level of cometary activity during this time period, a few months after perihelion, a deflected single population is characteristic for the solar wind protons. We attempt to separate these two observed proton populations in the mass-separated ICA data. We then analyse selected plasma properties of the two populations, such as flow velocity (magnitude and direction) and temperatures. This dual proton population is sporadically observed throughout the day, but is otherwise uncommon during the mission. We want to study how these occurrences are related to changes in the cometary environment and the interaction with the solar wind.

A previous study has shown that the difference in proton and alpha particle velocity downstream of a shock can be used to estimate the electrostatic potential of the observation point relative to the solar wind. We take a look on how to interpret the electrostatic potential estimate using the newly estimated proton velocities of both populations.

How to cite: Moeslinger, A., Nilsson, H., Stenberg Wieser, G., and Williamson, H.: Observation of dual proton populations by the Rosetta Ion Composition Analyser, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5648, https://doi.org/10.5194/egusphere-egu22-5648, 2022.

EGU22-5973 | Presentations | PS2.2

Reconstruction of the upstream solar wind at comet 67P 

Hans Nilsson, Anja Möslinger, Hayley Williamson, Sofia Bergman, and Gabriella Stenberg Wieser

 Rosetta followed comet 67P at heliocentric distances from 1.25 to 3.6 au. The solar wind was observed for much of this time, but significantly deflected and to some extent slowed down by the interaction with the coma. A method is derived to reconstruct the upstream solar wind from H+ and He2+ observations. The method is based on the assumption that the comet - solar wind interaction can be described by an electric potential that is the same for both H+ and He2+. The reonstructed speed is compared to estimates from the Tao model, as well as OMNI and Mars Express data propagated to the observation point. The reconstruction agrees well with the Tao model for most of the observations, in particular the statistical distribution of solar wind speed. The electrostatic potential relative to the upstream solar wind is derived and shows values from a few tens of V at large heliocentric distances to about 1 kV during solar events and close to perihelion. Reconstructed values of the solar wind for periods of high electrostatic potential are also in good agreement with propagated observations and model results. The Tao model captures some slowing down of high speed streams as compared to observations at Earth or Mars. At low solar wind speeds, below 400 km/s, agreement is better between our reconstruction and Mars observations than with the Tao model. The magnitude of the reconstructed electrostatic potential is a good measure of the slowing down of the solar wind at the observation point.

How to cite: Nilsson, H., Möslinger, A., Williamson, H., Bergman, S., and Stenberg Wieser, G.: Reconstruction of the upstream solar wind at comet 67P, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5973, https://doi.org/10.5194/egusphere-egu22-5973, 2022.

EGU22-6298 | Presentations | PS2.2

Global Current System of Martian Induced Magnetosphere: a Hybrid View 

Xiaodong Wang and Shahab Fatemi

Recent spacecraft observations have revealed the averaged global morphology of the magnetospheric current system of Mars. This current system is generated by the induction of the interplanetary magnetic field and the motional electric field of the solar wind. It couples the ionosphere below and the solar wind above and determines the distribution of the energy inputs from the fast-moving solar wind to the planetary atmospheric ions.

We use Amitis, a GPU-based hybrid (particle ions and fluid electrons) numerical model to study the current system. Under the typical space environment condition, we successfully reproduce the morphology of the observed current system, including the bow shock current, the induced magnetospheric boundary current, and the ionospheric current.

With the full information provided by the model, we can calculate the inner product of the electric field intensity and the current density for any location in the simulation domain. Furthermore, we can separate the currents due to solar wind and planetary ions, and separate the electric field terms caused by different mechanisms, thereby clarifying the contribution of different mechanisms to the ion escape in the solar wind interaction with Mars. 

How to cite: Wang, X. and Fatemi, S.: Global Current System of Martian Induced Magnetosphere: a Hybrid View, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6298, https://doi.org/10.5194/egusphere-egu22-6298, 2022.

EGU22-6696 | Presentations | PS2.2

Spatially Highly Resolved Solar-wind-induced Magnetic Field on Venus 

Maosheng He, Joachim Vogt, Eduard Dubinin, Tielong Zhang, and Zhaojin Rong

The current work investigates the Venusian solar-wind-induced magnetosphere at a high spatial resolution using all Venus Express (VEX) magnetic observations through an unbiased statistical method. We first evaluate the predictability of the interplanetary magnetic field (IMF) during VEX's Venusian magnetospheric transits and then map the induced field in a cylindrical coordinate system under different IMF conditions. Our mapping resolves structures on various scales, ranging from the ionopause to the classical IMF draping. We also resolve two recently reported structures, a low-ionosphere magnetization over the terminator, and a global "looping" structure in the near magnetotail. In contrast to the reported IMF-independent cylindrical magnetic field of both structures, our results illustrate their IMF dependence. In both structures, the cylindrical magnetic component is more intense in the hemisphere with an upward solar wind electric field (E^SW) than in the opposite hemisphere. Under downward E^SW, the looping structure even breaks, which is attributable to an additional draped magnetic field structure wrapping toward −E^SW. In addition, our results suggest that these two structures are spatially separate. The low-ionosphere magnetization occurs in a very narrow region, at about 88°–95° solar zenith angle and 185–210 km altitude. A least-squares fit reveals that this structure is attributable to an antisunward line current with 191.1 A intensity at 179 ± 10 km altitude, developed potentially in a Cowling channel.

How to cite: He, M., Vogt, J., Dubinin, E., Zhang, T., and Rong, Z.: Spatially Highly Resolved Solar-wind-induced Magnetic Field on Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6696, https://doi.org/10.5194/egusphere-egu22-6696, 2022.

EGU22-7665 | Presentations | PS2.2

Modeling the variability of Martian O+ ion escape due to Solar Wind forcing 

Ronan Modolo, Francois Leblanc, Jean-Yves Chaufray, Norberto Romanelli, Eduard Dubinin, Vincent Génot, Claire Baskevitch, David Brain, Shannon Curry, and Robert Lillis

During the last decade, MAVEN space mission have emphasized a widespread spatial distribution of escaping O+ ions (Brain et al., 2015; Dong et al., 2015; Curry et al., 2015). Statistical studies have demonstrated that such structure is constant and present an asymmetry with respect to the solar wind convective electric field direction. In the Mars Solar Ecliptic coordinate system, continuous large O+ ion fluxes have been observed from the Martian wake to the Northward hemisphere. Global hybrid models have been developed since more than fiffteen years (Modolo et al., 2005, 2016; Brecht and Ledvina, 2006; Kallio et al., 2006) predicting and reproducing successfully the main characteristics of these escaping ion signatures. To further characterize this heavy-ion escape and its variability due to the solar wind forcing, global hybrid simulations have been performed with different set of upstream solar wind parameters. The impact of the solar wind drivers on the dynamics of O+ ion fluxes are reported and compared to the statistical ion fluxes maps derived from MAVEN/STATIC observations (Dong et al., 2015).

Brain, D. A., McFadden, J. P., Halekas, J. S., Connerney, J. E. P., Bougher, S. W., Curry, S., et al. (2015). The spatial distribution of planetary ion fluxes near Mars observed by MAVEN. Geophys. Res. Lett. 42, 9142–9148. doi:10.1002/2015GL065293

Dong, Y., Fang, X., Brain, D. A., McFadden, J. P., Halekas, J. S., Connerney, J. E., et al. (2015). Strong plume fluxes at Mars observed by MAVEN: An important planetary ion escape channel. Geophys. Res. Lett. 42, 8942–8950. doi:10.1002/2015GL065346

Curry, S. M., Luhmann, J. G., Ma, Y. J., Dong, C. F., Brain, D., Leblanc, F., et al. (2015). Response of Mars O+ pickup ions to the 8 March 2015 ICME: Inferences from MAVEN data-based models. Geophys. Res. Lett. 42, 9095–9102. doi:10.1002/2015GL065304

Modolo, R., Chanteur, G. M., Dubinin, E., and Matthews, A. P. (2005). Influence of the solar EUV flux on the Martian plasma environment. Annales Geophysicae 23, 433–444. doi:10.5194/angeo-23-433-2005

 

Brecht, S. H. and Ledvina, S. A. (2006). The Solar Wind Interaction With the Martian Ionosphere/Atmosphere 126, 15–38. doi:10.1007/s11214-006-9084-z

Kallio, E., Fedorov, A., Budnik, E., Sa¨les, T., Janhunen, P., Schmidt, W., et al. (2006). Ion escape at Mars: Comparison of a 3-D hybrid simulation with Mars Express IMA/ASPERA-3 measurements 182, 350–359. doi:10.1016/j.icarus.2005.09.018

 

How to cite: Modolo, R., Leblanc, F., Chaufray, J.-Y., Romanelli, N., Dubinin, E., Génot, V., Baskevitch, C., Brain, D., Curry, S., and Lillis, R.: Modeling the variability of Martian O+ ion escape due to Solar Wind forcing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7665, https://doi.org/10.5194/egusphere-egu22-7665, 2022.

EGU22-7692 | Presentations | PS2.2

Europa’s interaction with the Jovian plasma from hybrid simulation 

Claire-Alexandra Baskevitch, Ronan Modolo, and Baptiste Cecconi

               Galilean moons are embedded in Jupiter’s giant magnetosphere. The Jovian plasma particles interact with the atmosphere of the moons, exchanging momentum and energy, and generate different phenomena such as aurora, electric current, etc.

The exploration of the Galilean moons, and in particular Ganymede and Europa, considered as potential habitats, are listed among the main objectives of the ESA JUpiter ICy moon Explorer (JUICE) mission. In preparation for future observations, a modelling effort is conducted to describe the Europa moon-magnetosphere system.

               We have used the LATMOS Hybrid Simulation (LatHyS) model to characterize the Jovian plasma and magnetic field interaction with the moon and its atmosphere. The model is a hybrid 3D, multi-species and parallel simulation model which is based on a kinetic description of ions and a fluid description of electrons. The model is based on the CAM-CL algorithm and various physical processes has been implemented to describe the solar wind (or a magnetospheric plasma) interaction with Mars, Mercury, Titan, Ganymede, Earth-like body etc… (Matthews, 1994, Modolo et al, 2016, Richer et al, 2012, Modolo et al, 2008, Leclercq et al, 2015, Turc et al, 2015).  This simulation model depicts the dynamic and the structure of the ionized environment in the neighborhood of these bodies. Recently, the model has been adapted to Europa-Jupiter interaction. Global simulation results are compared to Galileo observations and will be used to illustrate the conditions that JUICE might encounter during its flybys.

         
References :

Alan P. Matthews, Current Advance Method and Cyclic Leapfrog for 2D Multispecies Hybrid Plasma Simulations, Journal of Computational Physics, Volume 112, Issue 1, 1994, Pages 102-116, ISSN 0021-9991, https://doi.org/10.1006/jcph.1994.1084.

Turc L., Fontaine D., Savoini P., Modolo R., 3D hybrid simulations of the interaction of a magnetic cloud with a bow shock, JGR, 2015

Richer E, Modolo R, Chanteur GM, Hess S and Leblanc F, A Global Hybrid Model for Mercury's Interaction With the Solar Wind: Case Study of the Dipole Representation, Journ. Geophys. Res., doi:10.1029/2012JA017898, 2012

Leclercq L., Modolo R., Leblanc F., Hess S., Mancini M. ,3D Magnetospheric parallel hybrid multi-grid method applied to planet-plasma interactions, Journal of Computational Physics, 309, pp.295-313, 10.1016/j.jcp.2016.01.005, 2016

Modolo R., Hess S., Mancini M., Leblanc F., Chaufray J.-Y., Brain D., Leclercq L., Esteban Hernandez R., Chanteur G., Weill P., Gonzalez-Galindo F. et al., Mars-solar wind interaction: LatHyS, an improved parallel 3-D multispecies hybrid model, Journal of Geophysical Research : Space Physics, American Geophysical Union/Wiley, 2016, 121 (7), pp.6378-6399.10.1002/2015JA022324, 2016

How to cite: Baskevitch, C.-A., Modolo, R., and Cecconi, B.: Europa’s interaction with the Jovian plasma from hybrid simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7692, https://doi.org/10.5194/egusphere-egu22-7692, 2022.

EGU22-7952 | Presentations | PS2.2

Degenerate induced magnetospheres 

Stas Barabash, Mats Holmström, Futaana Yoshifumi, Qi Zhang, and Robin Ramstad

Induced magnetospheres of non-magnetized atmospheric bodies like Mars and Venus are formed by magnetic fields of ionospheric currents induced by the convective electric field E = - V x B/c of the solar wind. When the interplanetary magnetic field is mostly radial (the cone angle θ is close to 0°, quasi-parallel conditions) and the convective field E ≈ 0, an induced magnetosphere becomes degenerate. The degenerate induced magnetospheres can be considered as a specific type of the interaction with ambient plasma. This type of interaction were observed at Venus and Mars, for example, 12 observed cases for Venus and 17 observed cases for Mars for θ < 10° as recorded by Venus Express (2006-2014) and Mars express (2014-2019). However, the quasi-parallel conditions are nominal for the majority of discovered exoplanets (hot Jupiters) orbiting the parent stars on distances 0.01 – 0.1 au when θ < 4° (assuming the solar conditions). The conditions at some moons of icy giants, Neptune (Triton) and Uranus, are also quasi-parallel due to large angle between magnetic dipole and the rotation axis though the plasma flow is subsonic.

In this report we introduce degenerate induced magnetospheres as a new type of interaction and review the current works on the subject. We also show examples of observations at Mars and Venus and numerical simulations, and describe the main properties and basic physics of such configurations.

How to cite: Barabash, S., Holmström, M., Yoshifumi, F., Zhang, Q., and Ramstad, R.: Degenerate induced magnetospheres, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7952, https://doi.org/10.5194/egusphere-egu22-7952, 2022.

EGU22-8557 | Presentations | PS2.2

A magnetosheath hydrodynamic plasma flow model around Mercury 

Daniel Schmid, Yasuhito Narita, Ferdinand Plaschke, Martin Volwerk, Rumi Nakamura, and Wolfgang Baumjohann

The magnetosheath is defined as the plasma region between the bow shock, where the super-magnetosonic solar wind plasma is decelerated and heated, and the outer boundary of the intrinsic planetary magnetic field, the so-called magnetopause. Recently we  presented an analytical magnetosheath plasma flow model around Mercury, which can be used to estimate the plasma flow magnitude and direction at any given point in the magnetosheath exclusively on the basis of the plasma parameters of the upstream solar wind. However, this model assumes a constant plasma density and velocity along the flowlines. Here we present a more sophisticated model were we take hydrodynamic effects into account, to also obtain the density and velocity change along the flowline. The model serves as a useful tool to trace the magnetosheath plasma along the streamline both in a forward sense (away from the shock) and a backward sense (toward the shock), offering the opportunity of studying the growth or damping rate of a particular wave mode or evolution of turbulence energy spectra along the streamline in view of upcoming arrival of BepiColombo at Mercury.

How to cite: Schmid, D., Narita, Y., Plaschke, F., Volwerk, M., Nakamura, R., and Baumjohann, W.: A magnetosheath hydrodynamic plasma flow model around Mercury, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8557, https://doi.org/10.5194/egusphere-egu22-8557, 2022.

EGU22-8569 | Presentations | PS2.2

Martian crustal magnetic fields and their control of ionospheric plasma densities and temperatures 

David Andrews, Laila Andersson, Robert Ergun, Anders Eriksson, Marcin Pilinski, and Katerina Stergiopoulou

Mars Express and MAVEN observations have demonstrated the influence of Mars’s spatially variable crustal magnetic fields upon the configuration of the plasma in the ionosphere. This influence furthermore leads to variations in ionospheric escape, conceivably in part through the modification of the plasma density and electron temperature in the upper ionosphere. However, quantifying this control remains challenging given the generally dynamic and spatially varied nature of the Mars solar wind interaction, and the therefore naturally varying densities and temperatures of the upper ionosphere in particular. In this study we examine MAVEN Langmuir Probe and Waves data, finding a very clear correspondence between the structure of the crustal fields and both the measured electron temperatures and densities, by first constructing a robust “average” profile from which departures can be quantified. Electron temperatures are shown to be systematically lower in regions of strong crustal fields over a wide altitude range, as has been previously reported. Here, we additionally use measurements made by MAVEN in the solar wind, to explore the dependence of this crustal field control on the coupling to the solar wind and IMF.  We also attempt to quantitatively determine the altitude range over which this coupling between plasma density and temperature and crustal fields is effective.

How to cite: Andrews, D., Andersson, L., Ergun, R., Eriksson, A., Pilinski, M., and Stergiopoulou, K.: Martian crustal magnetic fields and their control of ionospheric plasma densities and temperatures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8569, https://doi.org/10.5194/egusphere-egu22-8569, 2022.

EGU22-9415 | Presentations | PS2.2

Discrete Aurora on Mars: Insights into reconnection? 

Nicholas Schneider, Ben Johnston, Sonal Jain, Zac Milby, Charlie Bowers, Gina Dibraccio, Jean-Claude Gérard, and Lauriane Soret

Analysis of nightside nadir-viewing observations taken by MAVEN's Imaging Ultraviolet Spectrograph instrument has identified nearly 200 discrete aurora emissions.  Discrete aurora are sporadic localized ultraviolet emissions originating in the upper Martian atmosphere that occur brightest and most frequently near regions of strong crustal magnetic field strength.  The emission detections were verified and characterized by visual appearance across the disk and spectral analysis of Cameron band and ultraviolet doublet emissions.  No geographic or magnetic field information was used to determine whether a suspected emission was real or an artifact in the data.   Unlike limb observations, nadir observations have no line-of-sight ambiguity, allowing us to locate the emissions with high geographic accuracy.  Nadir viewing also provides global coverage of the nightside disk, giving broad geographic and local time coverage.  We find the same dependence on local time, crustal field strength and interplanetary magnetic field orientation seen in limb observations (Schneider et. al. 2021).  

A large fraction of the observed events occur in open field regions associated with the strongest radial magnetic fields. These events occur along approximately east-west lines at the footprints of two magnetic field arcades, one with a north-directed horizontal crustral field and one south-directed (see below). Observations show that these arcades become active in an auroral sense at opposite times of night, one pre-midnight and the other post-midnight. We will show that the geometry of draping of the interplanetary magnetic field over the crustal fields provides a natural explanation for the different local time auroral triggerings, with magnetic reconnection more likely in one arcade pre-midnight and the other post-midnight.
 
    Figure 1: Mars Crustal Magnetic Field Geometry

How to cite: Schneider, N., Johnston, B., Jain, S., Milby, Z., Bowers, C., Dibraccio, G., Gérard, J.-C., and Soret, L.: Discrete Aurora on Mars: Insights into reconnection?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9415, https://doi.org/10.5194/egusphere-egu22-9415, 2022.

EGU22-9911 | Presentations | PS2.2

Protons in the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko 

Charlotte Goetz, Lucie Scharré, Cyril Simon Wedlund, Hans Nilsson, Elias Odelstad, Matthew Taylor, and Martin Volwerk

Against expectations, the Rosetta spacecraft was able to observe protons of solar wind origin in the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko. This study investigates these unexpected observations and gives a working hypothesis on what could be the underlying cause.

The cometary plasma environment is shaped by two distinct plasma populations: the solar wind, consisting of protons, alpha particles, electrons and a magnetic field, and the cometary plasma, consisting of heavy ions such as water ions or carbon dioxide ions and electrons.

As the comet follows its orbit through the solar system, the amount of cometary ions that is produced varies significantly. This means that the plasma environment of the comet and the boundaries that form there are also dependent on the comet's heliocentric distance.

For example, at sufficiently high gas production rates (close to the Sun) the protons from the solar wind are prevented from entering the inner coma entirely. The region where no protons (and other solar wind origin ions) can be detected is referred to as the solar wind ion cavity.

A second example is the diamagnetic cavity, a region very close to the nucleus of the comet, where the interplanetary magnetic field, which is carried by the solar wind electrons, cannot penetrate the densest part of the cometary plasma.

The Rosetta mission clearly showed that the solar wind ion cavity is larger than the diamagnetic cavity at a comet such as 67P/Churyumov-Gerasimenko. However, this new study finds that in isolated cases, ions of solar wind origin (mostly protons, but also helium) can be detected inside the diamagnetic cavity. We present the observations pertaining to these events and list and discard possible mechanisms that could lead to the solar wind cavity becoming permeable to protons, moving inside the diamagnetic cavity or vanishing entirely. Only one mechanism cannot be discarded: that of a solar wind configuration where the solar wind velocity is aligned with the magnetic field. We show evidence that fits this hypothesis as well as solar wind models in support.

How to cite: Goetz, C., Scharré, L., Simon Wedlund, C., Nilsson, H., Odelstad, E., Taylor, M., and Volwerk, M.: Protons in the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9911, https://doi.org/10.5194/egusphere-egu22-9911, 2022.

EGU22-10492 | Presentations | PS2.2

Lower-Hybrid waves observed by Rosetta at comet 67P 

Elias Odelstad, Anders Eriksson, and Tomas Karlsson

Electric field measurements from cometary environments are very rare, but can provide important information on how plasma waves help fashion the plasma environment. We investigate the plasma wave activity observed in the electric field measurements obtained by the Langmuir probe instrument (RPC-LAP) onboard ESA's Rosetta spacecraft, which followed the comet 67P/Churyumov-Gerasimenko in its orbit around the sun for over two years in 2014-2016. We focus on waves in the range 1-30 Hz, roughly corresponding to the lower-hybrid frequency range. Here, electric field oscillations close to the local H2O+ lower hybrid frequency are common. Especially large wave amplitudes are often observed at or near pronounced plasma density gradients, and a linear instability analysis shows that conditions are often favourable for wave growth by the lower hybrid drift instability. However, the association to density gradients is not ubiquitous and other instabilities are likely needed as well to explain the observed wave activity, e.g. the two-stream instability between solar wind protons and cometary pick-up ions. Close to peak activity of the comet however, the solar wind flow was entirely diverted and excluded from the inner parts of the coma, where the spacecraft was. Here, we instead propose that an ion/ion streaming instability between cold newborn cometary ions and heated heavy ions that were picked up earlier, plays an important role for generating the waves observed in the lower hybrid frequency range. We compare theoretical conditions for growth of these instabilities to observed conditions in the plasma at 67P. This investigation helps to clarify the role and importance of these plasma waves in the cometary plasma environment. They can, for example, heat or cool plasma populations, produce supra-thermal electrons, reduce plasma anisotropies and gradients, couple different plasma species, and provide anomalous resistivity.

How to cite: Odelstad, E., Eriksson, A., and Karlsson, T.: Lower-Hybrid waves observed by Rosetta at comet 67P, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10492, https://doi.org/10.5194/egusphere-egu22-10492, 2022.

EGU22-10876 | Presentations | PS2.2

Energetic Neutral Atoms at Mars: Predicted Distributions Based on MAVEN Measurements 

Robin Ramstad, David Brain, Yaxue Dong, Jasper Halekas, James McFadden, Jared Espley, and Bruce Jakosky

Measurements of Energetic Neutral Atoms (ENAs) provide information about both the plasma and neutral components along the line-of-sight for any ENA instrument, though the individual influences of the plasma and neutral environments are convoluted due to the nature of the charge-exchange ENA generation process. We combine ion flux and magnetic field measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter at Mars with models for the Martian exospheric components to predict the average observable 10 eV – 10 keV oxygen and hydrogen ENA distributions from virtual orbits in the near-Mars space environment. The predicted distributions are consistent with past ENA measurements, informing and constraining future ENA investigations of the neutral and plasma near-Mars space environments.

How to cite: Ramstad, R., Brain, D., Dong, Y., Halekas, J., McFadden, J., Espley, J., and Jakosky, B.: Energetic Neutral Atoms at Mars: Predicted Distributions Based on MAVEN Measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10876, https://doi.org/10.5194/egusphere-egu22-10876, 2022.

EGU22-13021 | Presentations | PS2.2

Simulating the interaction between a turbulent solar wind and bodies of the solar system. 

Etienne Behar and Pierre Henri

Menura, a  newly developped hybrid PIC code, allows the self-consistent simulation between a turbulent upstream flow and an obstacle. A global view of such interactions is a novel product which allows us to diagnose both the impact of the additional turbulent energy on the obstacle, and the evolution of the turbulence when processed by planetary boundaries. We present the examples of exospheres (comets, at various heliocentric distances) and ionospheres (Mars-like obstacle). We find that the boundaries are changed in size, and present a much more dynamic behaviour. New plasma structures appear within the magnetospheres due to the impinging perpendicular magnetic field fluctuations, piling up and draping around the dense ionospheres/exospheres (see Figure). The spectral content is also extracted from within the magnetospheres, providing a strong comparison point with experimental studies of magnetospheric turbulence.

 

How to cite: Behar, E. and Henri, P.: Simulating the interaction between a turbulent solar wind and bodies of the solar system., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13021, https://doi.org/10.5194/egusphere-egu22-13021, 2022.

ST4 – Space Weather and Space Climate

EGU22-2968 | Presentations | ST4.1

Predicting the Transit Time and Geo-effectiveness of Coronal Mass Ejections using Neural Networks 

Mohamed Nedal, Heba Shalaby, and Ayman Mahrous

Predicting the arrival time of Coronal Mass Ejections (CME) and the strength of their geomagnetic storms at Earth is crucial in space operations and essential to avoid losing our space instruments and not to risk our astronauts’ lives in space. Besides, protecting the power grids and pipelines on the ground from the side effects of geomagnetic storms. We contribute to this matter by implementing Neural Network (NN) models to predict the CME transit time and the minimum value of the Disturbed storm time (Dst) index of the associated geomagnetic storm.

For the first time, we employed the planets' ephemeris as input features. Taking the CME properties (angular width, linear speed, speed at 20 solar radii, measurement position angle, latitude, and longitude), the solar wind and plasma parameters (the differential speed between the CME and the solar wind, the average interplanetary magnetic field with its 3D components, proton density and plasma temperature, speed in 3D components, dynamic pressure, electric field, plasma beta parameter, Mach number, and magnetosonic Mach number), and the planets' ephemeris in the solar system (distance from the Sun, latitude, and longitude) as inputs, we performed a grid of NNs to predict not only the CME transit time but also the minimum disturbed storm time (Dst) index of the associated geomagnetic storm.

We proposed the new Best-of-the-Best (BOB) approach to optimize the NN hyperparameters using the GridSearch method in Python. We assembled our dataset from (Gopalswamy et al., 2010), (Micha lek et al., 2004), and (Richardson and Cane, 2010) with a total of 230 events between 1997 and 2020. This is the largest dataset of CME-ICME pairs along with solar wind indices and planets locations in the solar system so far.

Remarkably, for the given dataset, the best set of input features for predicting the CME transit time was the CME features and the planets' ephemeris, while for predicting the Dst index were the top correlated features, with a Mean Absolute Error (MAE) of 13.54 hr and 35.57 nT, respectively. More details are described in the manuscript. 

How to cite: Nedal, M., Shalaby, H., and Mahrous, A.: Predicting the Transit Time and Geo-effectiveness of Coronal Mass Ejections using Neural Networks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2968, https://doi.org/10.5194/egusphere-egu22-2968, 2022.

EGU22-3816 | Presentations | ST4.1

Drag-Based Ensemble Model (DBEMv4) with variable solar wind speed input 

Jaša Čalogović, Mateja Dumbović, Bojan Vršnak, Manuela Temmer, and Astrid Veronig

Drag-Based Ensemble Model (DBEM) is a probabilistic model for heliospheric propagation of Coronal Mass Ejections (CMEs) that predicts the CME hit chance, most probable arrival times and speeds, quantify the prediction uncertainties and calculate the confidence intervals. DBEM is based on the 2D analytical Drag-based Model (DBM) with very short computational time. By using CME cone geometry with flattening DBM calculates the CME arrival time and speed at Earth or any other given target in the solar system. DBEM considers the variability of model input parameters by making an ensemble of n different input parameters to obtain the distribution and significance of the DBM results. As an important tool for space weather forecasters, DBM/DBEM web application is integrated as one of the ESA Space Situational Awareness portal services (https://swe.ssa.esa.int/current-space-weather). Important requirement to perform DBM calculations is to assume that two input parameters namely background solar wind speed and the drag parameter γ are constant in order to have the analytical solution and fast computational times. However, this assumption is not always valid in more complex heliospheric conditions. Thus, to further increase the accuracy of CME propagation forecast we developed the new DBEMv4 version that calculates CME propagation in more steps with variable solar wind speeds. This allows also to employ as DBEMv4 input the dynamic solar wind data in real-time taken from simple persistence model under consideration of the CME propagation direction.

How to cite: Čalogović, J., Dumbović, M., Vršnak, B., Temmer, M., and Veronig, A.: Drag-Based Ensemble Model (DBEMv4) with variable solar wind speed input, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3816, https://doi.org/10.5194/egusphere-egu22-3816, 2022.

EGU22-3857 | Presentations | ST4.1

Determination of CME orientation and consequences for their propagation 

Karmen Martinic, Mateja Dumbovic, Manuela Temmer, Astrid Veronig, and Bojan Vrsnak

The configuration of the interplanetary magnetic field and features of the related ambient solar wind in the ecliptic and meridional plane are different. Therefore, one can expect that the orientation of the flux rope axis of a coronal mass ejection (CME) influences the propagation of the CME itself. However, the determination of the CME orientation remains a challenging task to perform. This study aims to provide a reference to different CME orientation determination methods in the near-Sun environment. Also, it aims to investigate the non-radial flow in the sheath region of the interplanetary CME (ICME) in order to provide the first proxy to relate the ICME orientation with its propagation. We investigated 22 isolated CME-ICME events in the period 2008-2015. We first determined the CME orientation in the near-Sun environment using a 3D reconstruction of the CME with the graduated cylindrical shell (GCS) model applied to coronagraphic images provided by the STEREO and SOHO missions. The CME orientation in the near-Sun environment was determined using an ellipse fitting technique to the CME outer front as determined from the SOHO/LASCO coronagraph. In the near-Earth environment, we obtained the orientation of the corresponding ICME using in-situ plasma and field data and also investigated the non-radial flow in its sheath region. The ability of GCS and ellipse fitting to determine the CME orientation is found to be limited to only distinguishing between the high or low inclination of the events. Most of the CME-ICME pairs under investigation were found to be characterized by a low inclination, and regardless of whether their inclination was high or low, the CME-ICME pairs maintained their inclination during interplanetary propagation. The observed non-radial flows in the sheath region show a greater y-direction to z-direction flow ratio for low-inclination events which suggests that there is a connection between the orientation and propagation of the observed CME-ICME pairs.

How to cite: Martinic, K., Dumbovic, M., Temmer, M., Veronig, A., and Vrsnak, B.: Determination of CME orientation and consequences for their propagation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3857, https://doi.org/10.5194/egusphere-egu22-3857, 2022.

EGU22-4063 | Presentations | ST4.1

Improving the Empirical Solar Wind Forecast (ESWF) model 

Daniel Milosic, Manuela Temmer, Stephan Heinemann, Tatiana Podladchikova, Astrid Veronig, and Bojan Vršnak

The empirical solar wind forecast (ESWF) model is an ESA service to forecast the solar wind speed at Earth with 4 days lead time. The model uses a simple empirical relation between the area of coronal holes (CHs) as measured in meridional slices in EUV at the Sun and the in-situ measured solar wind speed at 1 AU (Vršnak, Temmer, Veronig, 2007). The relation has the drawback that Gaussian type speed profiles are produced as the CH rotates in and out of the meridional slice. With adaptations to the ESWF algorithm we aim to improve the precision of the ESWF speed profile by implementing compression and rarefaction effects occurring between SW streams of different velocities in the interplanetary space. By considering the propagation times for plasma parcels between the Sun and Earth and their interactions, we achieve the asymmetrical shape of the speed profile that is characteristic of high-speed streams (HSS). We present a statistical analysis for the period 2012 - 2019 showing that our adaptions improve the ability to predict HSS speed profiles as well as smaller structures with higher precision.

How to cite: Milosic, D., Temmer, M., Heinemann, S., Podladchikova, T., Veronig, A., and Vršnak, B.: Improving the Empirical Solar Wind Forecast (ESWF) model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4063, https://doi.org/10.5194/egusphere-egu22-4063, 2022.

EGU22-4595 | Presentations | ST4.1

L1 observations and geoeffectivity consecutive to the frontside halo coronal mass ejections (CMEs) of year 2002 

Benjamin Grison, Nicole Cornilleau-Wehrlin, Karine Bocchialini, and Brigitte Schmieder

Bocchialini et al. (2018) showed that among the 28 frontside halo coronal mass ejections (CMEs) with a visible source seen on the Sun in 2002, 21 are unambiguously associated with sudden storm commencements (SSCs). Based on velocity comparisons (LASCO, L1, and ballistic velocities), we look for association between these 28 halo CMEs and shock-like discontinuities observed in solar wind and interplanetary magnetic field (IMF) observations at L1. Geoeffectivity is tested on Dst, am, PCN, and auroral indices responses.

The present work complements the Boochialini's study by analysing systematically all the 28 halo CMEs, including the seven halos CMEs not associated with SSCs. Source locations, potential L1 signatures and geoeffectivity of these seven halo CMEs provide an overview of the properties related to halo CMEs in 2002, complementing Boccialini's et al. results. None of the discontinuities possibly associated to each of the seven halo CMEs corresponds to a clear ICME signature, based on our observations and on existing catalogs, showing that the central regions of the halo CMEs are not passing L1.

From the L1 observations of frontside CME halos observed in 2002, we conclude that halo CMEs not associated with SSCs in 2002 are non-geoeffective. We also note that all halo CMEs observed in 2002 and associated with ICMEs or magnetic clouds at L1 are also associated with SSCs. lders. The work leading to this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace (Radiation Belt Environmental Indicators for the Safety of Space Assets) project.

How to cite: Grison, B., Cornilleau-Wehrlin, N., Bocchialini, K., and Schmieder, B.: L1 observations and geoeffectivity consecutive to the frontside halo coronal mass ejections (CMEs) of year 2002, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4595, https://doi.org/10.5194/egusphere-egu22-4595, 2022.

EGU22-5020 | Presentations | ST4.1

The effect of AMR on the advanced magnetized CME model 

Tinatin Baratashvili, Stefaan Poedts, and Christine Verbeke

Coronal Mass Ejections (CMEs) are the main drivers of interplanetary shocks and space weather disturbances. One of the key parameters that determine the geo-effectiveness of the CME is its internal magnetic configuration. Strong CMEs directed towards Earth can have a severe impact on our planet and their prediction can mitigate possible damages. 

 

The novel heliospheric model Icarus, which is implemented within the framework of MPI-AMRVAC (Xia et al., 2018) introduces new capabilities to model the heliospheric wind and real CME events. Advanced techniques, such as adaptive mesh refinement and grid stretching are implemented. By imposing these techniques, we avoid cell deformation in the domain and only the necessary/desired areas are refined to higher spatial resolutions (and coarsened again when the high resolution is no longer necessary, e.g. behind a travelling shock wave). The refinement and coarsening conditions are controlled by the user. These techniques result in optimised computer memory usage and a significant speed-up, which is crucial for forecasting purposes. 

 

In order to model the magnetic field of the CME and its interaction with the solar wind, the Gibson and Low model is implemented in Icarus. In order to assess the ICARUS model capabilities to predict the solar wind conditions in the heliosphere, especially at L1, we consider a real CME event.  Further, we perform a comparison of the results of the existing Linear Force-Free Spheromak model and the new advanced model. To perform the full comparison we compare the time series data at L1 and other satellites, while we also monitor the time that simulations require to model the heliospheric wind and CME events. 

 

The solution mesh refinement is applied to the CMEs in order to model its arrival time and interior magnetic field better. To analyse the results, the radial, longitudinal and latitudinal components of the magnetic field are compared to the original EUHFORIA simulations and the observed data. As a result, the new magnetized model gives an opportunity to model the CME better and a bigger range of parameters to investigate to model the event as accurately as possible.  

 

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Baratashvili, T., Poedts, S., and Verbeke, C.: The effect of AMR on the advanced magnetized CME model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5020, https://doi.org/10.5194/egusphere-egu22-5020, 2022.

EGU22-8660 | Presentations | ST4.1

Geomagnetic storms forecasting from solar coronal holes 

Simona Nitti, Tatiana Podladchikova, Astrid M. M. Veronig, Stefan Hofmeister, Giuliana Verbanac, and Mario Bandić

Coronal holes (CHs) are the source of high-speed solar wind streams (HSSs), which interact with the slow solar wind and form corotating interaction regions (CIRs) in the heliosphere. These high-speed streams and their associated structures influence the geomagnetic activity, causing recurrent geomagnetic storms. The propagation time of solar wind from Sun to Earth is about 1–5 days, creating a natural lead-time for early warning. However, the magnetic structure of an interplanetary perturbation, in particular the southward component Bz of the interplanetary magnetic field (IMF), driving the storm, cannot be determined from solar observations yet, which strongly limits the possibility of storm forecast several days in advance. Current approaches to quantitative storm predictions are often limited to a short-term forecast based on measurements of IMF and solar wind at the Lagrange point L1, which is possible due to the 1-hour difference in the propagation time from L1 to Earth between the radio signal and solar wind.

In this study, we focus on predictions of CIR-driven geomagnetic storms from solar observations with the aim of increasing the warning lead-time from hours to days. We develop a prediction technique of geomagnetic storms using coronal holes at the Sun as well as corresponding solar magnetic field data (cf. Vrsnak et al. 2007). The method is based on establishing empirical relations between the time-series of coronal hole areas on the Sun derived from SDO/AIA images and the solar wind speed at L1; between remote-sensing magnetic field maps of the solar photosphere and that measured in-situ at L1, and finally between coronal hole areas, corresponding magnetic field at Sun and geomagnetic Dst and Kp indices. We demonstrate that the inward/outward direction of the magnetic field originating from the base of a coronal hole is preserved in more than 80% of cases when compared to the related magnetic field measured at Earth. This opens the possibility to use the magnetic field derived from solar observations instead of that at L1. Additionally, to improve the predictions for which we need to derive the Bz component, we analyze the Russel-McPherron effect, which reflects the change of the Bz component and the associated geomagnetic activity through the seasons. The approach proposed in this study for forecasting the Dst/Kp indices makes use of the Gaussian Process Regression, a non-parametric Bayesian model, suitable in case of limited available data, flexible non-linear problems and known prior information about the output (e.g. periodicity). Testing the developed forecasting technique for the whole SDO period 2010-2020, we obtained that the correlation coefficient between the predicted and observed Dst (Kp) index reaches r = 0.68/0.73 (0.67/0.76), for coronal holes having the positive/negative polarity on the Sun. These results demonstrate that the proposed technique opens a possibility to predict CIR-driven geomagnetic storms from solar observations resulting in the extension of the lead time from hours up to several days, which is highly important for warnings of the space weather conditions in the near-Earth environment and other space weather applications.

How to cite: Nitti, S., Podladchikova, T., M. Veronig, A. M., Hofmeister, S., Verbanac, G., and Bandić, M.: Geomagnetic storms forecasting from solar coronal holes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8660, https://doi.org/10.5194/egusphere-egu22-8660, 2022.

EGU22-8887 | Presentations | ST4.1

CME-learn: An interactive playground to benchmark CME databases for the time of arrival (ToA) prediction for using machine learning methods. 

Ajay Tiwari, Enrico Camporeale, Dario Del Moro, Raffaello Foldes, Gianluca Napoletano, Giancarlo de Gasperis, and Jannis Teunissen

Coronal mass ejections are one of the most significant drivers of space weather. The ToA predictions along with the Arrival speed of the CMEs are one of the crucial pieces of information for preparing for the possible geomagnetic storms. Geomagnetic storms can have adverse effects on several key components of modern society e.g. communications and electrical grids. The development of many machine learning methods provides us with the opportunity to use these tools in space weather applications. There have been several studies using machine learning methods for ToA predictions. In this study, we present an interactive dashboard to apply several machine learning methods (regression models) to test on the several CME databases used in the community. We also use this opportunity to benchmark various CME databases for TOA and CME arrival speed predictions. We also welcome the community to use this interactive dashboard as a tool to learn about machine learning.

How to cite: Tiwari, A., Camporeale, E., Del Moro, D., Foldes, R., Napoletano, G., de Gasperis, G., and Teunissen, J.: CME-learn: An interactive playground to benchmark CME databases for the time of arrival (ToA) prediction for using machine learning methods., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8887, https://doi.org/10.5194/egusphere-egu22-8887, 2022.

EGU22-8908 | Presentations | ST4.1

The impact of the spheromak tilting in space weather modelling 

Eleanna Asvestari, Tobias Rindlisbacher, Jens Pomoell, and Emilia Kilpua

Accurate reconstruction of the magnetic field topology of coronal mass ejections (CMEs) is essential in space weather forecasting and thus in the spotlight of modelling efforts. The spheromak, a force-free, axisymmetric configuration within which plasma is confined by a twisted magnetic field that fills a spherical volume, is at the moment the most commonly employed flux rope model, which has entered numerous published event studies. Despite its widespread application, not much attention has been paid to the spheromak tilting, which not only affects the spheromak's orientation in the modelling domain, but also its direction of propagation. This can lead to implications when comparing simulation output to observations. The tilting of the spheromak occurs when its magnetic moment is at an angle with the ambient magnetic field. In this case a torque is exerted on the spheromak, forcing it to rotate, so that its magnetic moment aligns to the ambient magnetic field. In our study we used EUHFORIA to investigate the spheromak tilting under different conditions. We developed a method to monitor the spheromak's position and orientation in the EUHFORIA simulation output, and we quantified how the spheromak's total drift and rotation angle depend on various input parameters. We find that the spheromak experienced tilting in all studied scenarios resulting often in a significantly changed orientation to that which it had during insertion. We emphasize that in space weather modelling it is crucial to take into consideration the spheromak tilting, in particular when comparing the model output to observations.

How to cite: Asvestari, E., Rindlisbacher, T., Pomoell, J., and Kilpua, E.: The impact of the spheromak tilting in space weather modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8908, https://doi.org/10.5194/egusphere-egu22-8908, 2022.

EGU22-9162 | Presentations | ST4.1

Drag-based deformation of a multi-point CME event 

Tanja Amerstorfer, Maike Bauer, Christian Möstl, Luke Barnard, Pete Riley, Andreas J. Weiss, and Martin A. Reiss

We present first results of a case study on a CME from October 2021 that was in situ detected by BepiColombo, Solar Orbiter, DSCOVR and STEREO-A, whose Heliospheric Imagers (HI) additionally observed the event remotely. The latter observations are used to model the evolution of the CME through the inner heliosphere using the CME propagation model ELlipse Evolution based on HI (ELEvoHI). ELEvoHI assumes a drag-based interaction of the CME-sheath with the solar wind and allows it to deform according to local drag regimes. The ambient solar wind is provided by the time-dependent HelioMAS/HUXt model. Using the arrivals at the four different spacecraft we are able to assess the ability of ELEvoHI to model the evolution of the shape of this CME.

How to cite: Amerstorfer, T., Bauer, M., Möstl, C., Barnard, L., Riley, P., Weiss, A. J., and Reiss, M. A.: Drag-based deformation of a multi-point CME event, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9162, https://doi.org/10.5194/egusphere-egu22-9162, 2022.

EGU22-9594 | Presentations | ST4.1

Coronal dimmings as indicators of the CME  evolution close to the Sun 

Galina Chikunova, Tatiana Podladchikova, Karin Dissauer, and Astrid Veronig

Coronal dimmings are regions in the solar corona that represent a sudden decrease of the coronal EUV and SXR emission, which is interpreted as a density depletion caused by the evacuation of plasma due to the CME eruption. Distinct relations have been established between coronal dimming parameters (intensity, area, magnetic flux) and key characteristics (mass, speed) of the associated CMEs by combining coronal and coronagraphic observations from different viewpoints in the heliosphere   (Dissauer et al. 2019, Chikunova et al. 2020).

In this contribution, we study whether coronal dimmings can be used to indicate possible deflections of CMEs close to the Sun and to identify their propagation direction. We present a set of detailed case studies where, by using simultaneous observations from the SDO and STEREO satellites, we track both the evolution of the coronal dimmings and the CME properties with respect to their directions. Our findings suggest that the direction of growth of the coronal dimming region and the evolution of the dimming intensity are related to the initial direction of the CME and also reflect various changes in its evolution, indicating deflection and/or interaction with surrounding active regions. These findings are important in better constraining CME evolution and direction close to the Sun and its further connection toward interplanetary space.

How to cite: Chikunova, G., Podladchikova, T., Dissauer, K., and Veronig, A.: Coronal dimmings as indicators of the CME  evolution close to the Sun, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9594, https://doi.org/10.5194/egusphere-egu22-9594, 2022.

EGU22-10472 | Presentations | ST4.1

Modeling solar wind background for CME propagation using the Alfven Wave Solar atmosphere Model (AWSoM) 

Nishtha Sachdeva, Gabor Toth, Ward Manchester, Bart van der Holst, Zhenguang Huang, and Carl Henney

The first step towards reliable prediction of the impact of solar transients that drive space weather is to accurately model the background solar wind into which these transients propagate. Uncertainties in the plasma environment into which CMEs propagate can lead to significant errors in time of arrival and impact prediction which is important for technology that humans are routinely dependent on as well as space-based explorations.

We use the physics-based 3D extended MHD Alfven Wave Solar atmosphere Model (AWSoM) within the Space Weather Modeling Framework (SWMF) developed at the University of Michigan to model the solar wind conditions during periods of high activity that include many strong solar transient events. These modeling efforts are validated by both in-situ and remote observations including EUV observations in the low corona from STEREO-A/B and SDO-AIA as well as plasma parameters at L1 from the OMNI database. AWSoM is driven by observations of the photospheric magnetic field. We use the ADAPT magnetic field maps that model the evolution of the observed magnetic field on the solar surface using physical processes like flux-transport, supergranulation and meridional flows. Our results show how our solar corona model behaves when driven by different data products like GONG and HMI observations.

In addition to the input magnetograms, the results also depend on model parameters. AWSoM is a self-consistent physics-based model with only a few free parameters. In our NSF funded Space Weather with Quantified Uncertainty (SWQU) project we systematically study the uncertainty quantification associated with various model inputs and parameters. We find that during periods of higher solar activity the Poynting flux parameter at the inner boundary needs to be adjusted to match the observations well to provide correct initial conditions for CME propagation. This work is in preparation for simulating CMEs launched from the Sun and propagating into correct solar wind background in order to achieve accurate and reliable space weather modeling and prediction.

How to cite: Sachdeva, N., Toth, G., Manchester, W., van der Holst, B., Huang, Z., and Henney, C.: Modeling solar wind background for CME propagation using the Alfven Wave Solar atmosphere Model (AWSoM), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10472, https://doi.org/10.5194/egusphere-egu22-10472, 2022.

Coronal mass ejections (CMEs) and solar energetic particles (SEPs) are manifestations of the dynamic and explosive nature of solar activity and major drivers of space weather events. They often occur in concert, especially in the case of large and fast CMEs that are associated with strong flares and that are able to accelerate SEPs at the shocks ahead of them. Modelling efforts that aim to forecast and mitigate the effects of these solar phenomena range from empirical to analytical to numerical. Although the primary focus of space weather forecasts is naturally on Earth, the increased amount of heliospheric and planetary missions launched in the past ~15 years has provided new opportunities for CME and SEP measurements at other locations in the inner solar system. This has resulted in the possibility to test space weather forecasting models at multiple locations well separated in both heliocentric distance and longitude within the same event, which in turn represents a novel way to benchmark and validate the present capabilities.

In this presentation, we will first briefly review the current status of CME and SEP space weather forecasting, with particular attention given to the main challenges to overcome for advancing predictions. We will then present a few examples of CME and SEP events that were detected in situ at multiple locations in the inner heliosphere and show forecasting—or actually hindcasting—results for each of them. Finally, we will conclude by addressing possible future improvements that take advantage of model validation via multi-spacecraft measurements.

How to cite: Palmerio, E.: Space weather predictions of CMEs and SEPs through the inner heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10831, https://doi.org/10.5194/egusphere-egu22-10831, 2022.

EGU22-11485 | Presentations | ST4.1

Evolution of the critical torus instability height and CME likelihood in solar active regions 

Alexander James, David Williams, and Jennifer O'Kane

Aims: Working towards improved space weather predictions, we aim to quantify how the critical height at which the torus instability drives coronal mass ejections (CMEs) varies over time in a sample of solar active regions.

Methods: We model the coronal magnetic fields of 43 active regions and quantify the critical height at their central polarity inversion lines throughout their observed lifetimes. We then compare these heights to the changing magnetic flux at the photospheric boundary and identify CMEs in these regions.

Results: We find higher rates of CMEs per unit time during phases when the critical height is falling rather than rising, and when magnetic flux is increasing rather than decreasing. Furthermore, we support and extend the results of previous studies by demonstrating that the critical height in active regions is generally proportional to the separation of their magnetic polarities through time.

How to cite: James, A., Williams, D., and O'Kane, J.: Evolution of the critical torus instability height and CME likelihood in solar active regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11485, https://doi.org/10.5194/egusphere-egu22-11485, 2022.

EGU22-11702 | Presentations | ST4.1

A potential near real-time algorithm for CME propagation utilizing heliospheric imaging observations 

Evangelos Paouris and Angelos Vourlidas

The estimation of the Coronal Mass Ejection (CME) arrival at Earth is an open issue in the field of Space Weather. We present a new near real-time algorithm based on heliospheric imaging (HI) observations of the CME front as a function of time. First, we transform the front elongation angle into radial distance using basic stereoscopic techniques (i.e. fixed-phi, harmonic mean and self-similar expansion). Then we adopt the assumptions that (1) CME accelerate (or decelerate) from the Sun up to some distance and (2) they move with a constant speed past that distance. This “two-phase kinematics” behavior forms the core of our algorithm. The resulting kinematic profiles provide estimates of the CME Time-of-Arrival (ToA) and Speed-on-Arrival (SoA) at 1 AU. This new tool is tested on a sample of CMEs where stereoscopic views were possible, from the STEREO-A and -B HIs were available. The algorithm is promising with predictions for the ToA of CMEs of the order of ±1 hour and for SoA of ±100 km/s. Our approach is in preparation for a possible future combination of HI data from missions at L5. We will test our method further for cases beyond the 1 AU studying ICMEs which has been spotted also on Mars (1.52 AUs).

How to cite: Paouris, E. and Vourlidas, A.: A potential near real-time algorithm for CME propagation utilizing heliospheric imaging observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11702, https://doi.org/10.5194/egusphere-egu22-11702, 2022.

EGU22-11848 | Presentations | ST4.1

Current sheets in front of geoeffective streams and flows as precursors of geomagnetic storms 

Mikhail Fridman, Olga Khabarova, Timofey Sagitov, and Roman Kislov
The number of current sheets observed at 1 AU depends on the corresponding type of the solar wind plasma flow or stream in which current sheets occur. Prior studies have shown that the maximum of the current sheet rate is detected in turbulent and hot flows and streams such as corotating/stream interaction regions (CIRs/SIRs) and the coronal mass ejection (ICME) sheath (Khabarova et al. JGR, 2021,  https://doi.org/10.1029/2020JA029099).  It is also known that the number of current sheets per hour begins to rise several hours before the arrival of potentially geoeffective CIRs/SIRs and ICMEs. This effect has been interpreted in literature as a crossing of so-called magnetic cavities filled with coherent structures (Khabarova et al. Sp Sci Rev. 2021, https://doi.org/10.1007/s11214-021-00814-x).
On the other hand, it is known that geomagnetic storms are preceded by ULF variations in the interplanetary magnetic field and solar wind density. We show that such ULF variations are associated with crossings of magnetic islands and current sheets inside magnetic cavities formed in front of geoeffective high-speed streams and flows.
A statistical analysis of the occurrence of current sheets prior to geomagnetic storms has been carried out employing the multi-year database of current sheets at 1 AU for 2011-2013 (see https://csdb.izmiran.ru) . 43 geomagnetic storms with Dst index lower than  -50nT were detected during that period . The results show that there is an 80% increase in the number of current sheets before a geomagnetic storm commencement with a 10-hour advance time, on average. Therefore, current sheets can potentially be used as geomagnetic storm precursors.
A mid-term geomagnetic storm forecast technique using a Recurrent Neural Network for an automatic pattern search is proposed, based on this phenomenon. The minute data of the solar wind density, the number of current sheets, and the window Fourier transform results are taken as input data. Examples of the mid-term prognosis of geomagnetic storms are presented.

How to cite: Fridman, M., Khabarova, O., Sagitov, T., and Kislov, R.: Current sheets in front of geoeffective streams and flows as precursors of geomagnetic storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11848, https://doi.org/10.5194/egusphere-egu22-11848, 2022.

EGU22-84 | Presentations | ST4.2

The future evolution of the auroral zones 

Stefano Maffei, Philip Livermore, Jonathan Mound, Joseph Eggington, Jonathan Eastwood, Sabrina Sanchez, and Mervyn Freeman

The auroral zones indicate the locations on the Earth’s surface where, on average, it is most likely to spot aurorae as a consequence of increased solar activity. The shape of the auroral zones and, similarly, the geographical locations most vulnerable to extreme space weather events are modulated by the geomagnetic field of internal origin. As the latter evolves in time, the formers will be subject to variations on the same timescales.

From available geomagnetic field forecasts (which provide an estimate of the future evolution of the geomagnetic field of internal origin) we derive AACGM latitudes and estimate the future evolution of the auroral zones. The novel aspect of this technique is that we make use of all available Gauss coefficients to produce the forecasts, while the majority of present techniques estimate the location of the auroral zones based on the dipolar coefficients only. Our results show that, while the shift of the geomagnetic dipole axis has a first order contribution, higher order Gauss coefficients contribute significantly to the location and shape of the auroral zones.

The same technique is then extended to estimate the future location of the geographical location that would be, on average, most exposed to extreme space weather event. We find that the space-weather related risk will not change significantly for the UK over the next 50 years. For the Canadian provinces of Quebec and Ontario, however, we predict a significant increase in the risk associated to extreme solar activity.

How to cite: Maffei, S., Livermore, P., Mound, J., Eggington, J., Eastwood, J., Sanchez, S., and Freeman, M.: The future evolution of the auroral zones, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-84, https://doi.org/10.5194/egusphere-egu22-84, 2022.

EGU22-1655 | Presentations | ST4.2

Using IPIM to Simulate the Ionosphere’s Response to Extreme Space Weather 

Simon Thomas, Pierre-Louis Blelly, Aurelie Marchaudon, Julian Eisenbeis, and Samuel Bird

The IRAP Plasmasphere Ionosphere Model (IPIM) describes the transport equations of
ionospheric plasma species along magnetic closed field lines. As input, the previous iteration
of IPIM used basic models to provide estimations of the solar wind conditions, convection,
and precipitation within the ionosphere. In this presentation, we discuss the development of
a new operational version of IPIM as part of the EUHFORIA project to monitor and forecast
space weather conditions and hazards. The developments of the model include using in-situ
solar wind observations from the OMNI data set, ionospheric radar data of plasma motions
from the Super Dual Auroral Radar Network (SuperDARN), and precipitation data from the
Ovation model, as inputs to the model. We present the first results from the latest IPIM
version, focussing on case study coronal mass ejections on 14th December 2006 and 14th
July 2012 which featured clear magnetic clouds and long-lasting southward magnetic field.
For these events, we explore simulations of plasma densities, temperature, and motions,
and compare with observations from EISCAT ionospheric radars and ionosonde launches.
With these results in mind, we will discuss the skill of using IPIM as a space weather
forecasting and analysis tool.

How to cite: Thomas, S., Blelly, P.-L., Marchaudon, A., Eisenbeis, J., and Bird, S.: Using IPIM to Simulate the Ionosphere’s Response to Extreme Space Weather, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1655, https://doi.org/10.5194/egusphere-egu22-1655, 2022.

EGU22-1732 | Presentations | ST4.2

Effects of Forbush Decreases on Clouds as determined from PATMOS-x 

Haruka Matsumoto, Henrik Svensmark, and Martin Enghoff

This study examines the relationship between cosmic rays and clouds during Forbush decreases (FDs) to understand the cause-effect relationships between cloud microphysics, cloud condensation nuclei (CCN), and ionisation in the atmosphere. The results of a Monte Carlo analysis of cloud parameters during FDs from newly calibrated satellite data, namely, the Pathfinder Atmospheres Extended (PATMOS-x) from 1978 to 2018, show the connections between some cloud parameters and FDs. For context, FD is the event where, the amount of cosmic rays arriving in the atmosphere decreases and recovers over several days. Other studies have shown that FDs impacted the cloud fraction, aerosol optical depth, CCN, water content, and cloud effective radius (reff ) in the atmosphere. Using the Monte Carlo analysis, nine atmospheric parameters from the dataset were evaluated for a significant response level to FDs. Each FD event added (after the first event) reduces the noise, but only the strongest events add a significant signal (exceptionally when the 2nd and 5th rank FD data are added, the signal/noise ration dropped due to change of satellite version). We found that cloud fraction shows statistically significant signals following FDs at an achieved significance level of 0.33%. Cloud emissivity also showed highly significant signals from the analysis, however these cannot be determined as physical cause by FDs since the response starts a week before the FDs. In contrast, the cloud optical depth, integrated total cloud water over the entire column, and reff did not show any significant signals in frameworks of the applied methods. The top-of-atmosphere brightness temperature at nominal wavelengths of 3.75, 11.0, and 12.0 µm and surface brightness temperature were analysed anew and showed significant signals. The estimated brightness temperature changes from a radiative transfer model (Fu-Liou model) show consistent results with the observed changes in cloud parameters during FD events. Among analysed several atmospheric/cloud/aerosol parameters, cloud fraction and the top-of-atmosphere brightness temperature at nominal wavelengths of 3.75, 11.0, 12.0 µm remain the only parameters depicting a statistically significant and correct-phase response to FDs.

How to cite: Matsumoto, H., Svensmark, H., and Enghoff, M.: Effects of Forbush Decreases on Clouds as determined from PATMOS-x, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1732, https://doi.org/10.5194/egusphere-egu22-1732, 2022.

EGU22-1995 | Presentations | ST4.2 | Highlight

The open-ended, high-cadence, Kp-like and fully operational geomagnetic Hpo indices for the ESA Space Weather G-ESC service network 

Guram Kervalishvili, Jürgen Matzka, and Jan Rauberg

Global geomagnetic indices are widely used not only to characterize the geomagnetic disturbance level but also for the parameterization of physical and empirical models of the near-Earth space environment and in data (re)analysis. One of the most utilized index families is the three-hourly Kp and the ap, Ap, Cp, C9 indices derived and disseminated by the GFZ German Research Centre for Geosciences.

The new global geomagnetic open-ended, high-cadence, Kp-like Hpo index family (consisting of the half-hourly Hp30, ap30 and hourly Hp60, ap60) was developed within the Space Weather Atmosphere Models and Indices (SWAMI) project of the H2020 EU research activity. These open-ended Hpo indices are based on the data of the same 13 geomagnetic observatory and similar algorithms as the three-hourly Kp index. The open-ended indices are designed such that 15 Hp60 and 32 Hp60 values exceeding 9 (maximum amplitude for the Kp index) have been assigned since 1995.

Near real-time indices and archive indices back to 1995 are available for download under the CC BY 4.0 license and include the linear versions of the Hp30 and Hp60 indices, the ap30 and ap60 indices. Near real-time plots of the Hp30 and Hp60 indices for the current day and the previous six days are also provided. Here, the operational capabilities and examples of these indices will be presented.

How to cite: Kervalishvili, G., Matzka, J., and Rauberg, J.: The open-ended, high-cadence, Kp-like and fully operational geomagnetic Hpo indices for the ESA Space Weather G-ESC service network, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1995, https://doi.org/10.5194/egusphere-egu22-1995, 2022.

A modeling approach for long time predictions (more than 12 h) of ionospheric disturbances driven by solar storm events is presented. Intended for an operational framework, this model shall deliver fast and precise localized warnings for these disturbances in the future. For this reason, a data base of historical solar storm impacts covering two solar cycles is used to reconstruct future events and resulting ionospheric disturbances. Here, we will present the basic components of the model and show first validation results based on predicted and observed geomagnetic activity, global total electron content and selected solar storms. Two storm events (including the St. Patrick’s Day geomagnetic storm during the 17 March 2015) are analyzed in more detail to illustrate the model capabilities. We will also discuss possible future improvements of the individual model parts, as well as the planned extensions and applications.

How to cite: Schmölter, E. and Berdermann, J.: An ionospheric disturbance forecast model based on real-time solar wind analysis with the best-fitting historical storm events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2155, https://doi.org/10.5194/egusphere-egu22-2155, 2022.

EGU22-2233 | Presentations | ST4.2

On the magnetosphere-ionosphere coupling during the May 2021 Geomagnetic storm. 

Piero Diego, Mirko Piersanti, Dario Del Moro, Alexandra Parmentier, Matteo Martucci, Farnacesco Palma, Alessandro Sotgiu, Christina Plainaki, Giulia D'Angelo, Francesco Berrilli, Dario Recchiuti, Emanuele Papini, Gianluca Napoletano, Antonio Cicone, Roberto Iuppa, Roberta Sparvoli, Pietro Ubertini, Roberto Battiston, and Piergiorgio Picozza

On May 12,  2021 the interplanetary counterpart of the May 9,  2021 coronal mass ejection impacted the Earth’s magnetosphere, giving rise to a strong geomagnetic storm.  This work discusses the evolution of the various events linking the solar activity to the Earth’s ionosphere with special focus on the effects observed in the circumterrestrial environment. We investigate the propagation of the interplanetary coronal mass ejection and its interaction with the magnetosphere - ionosphere system in terms of both magnetospheric current systems and particle redistribution, by jointly analysing data from interplanetary, magnetospheric, and low Earth orbiting satellites. The principal magnetospheric current system activated during the different phases of the geomagnetic storm is correctly identified through the  direct  comparison  between  geosynchronous  orbit  observations  and  model  predictions. From the particle point of view, we have found that the primary impact of the storm development is a net and rapid loss of relativistic electrons from the entire outer radiation belt. Our analysis shows no evidence for any short-term recovery to pre-storm levels during the days following the main phase.  Storm effects also included a small Forbush decrease driven by the interplay between the interplanetary shock and subsequent magnetic cloud arrival.

How to cite: Diego, P., Piersanti, M., Del Moro, D., Parmentier, A., Martucci, M., Palma, F., Sotgiu, A., Plainaki, C., D'Angelo, G., Berrilli, F., Recchiuti, D., Papini, E., Napoletano, G., Cicone, A., Iuppa, R., Sparvoli, R., Ubertini, P., Battiston, R., and Picozza, P.: On the magnetosphere-ionosphere coupling during the May 2021 Geomagnetic storm., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2233, https://doi.org/10.5194/egusphere-egu22-2233, 2022.

EGU22-2776 | Presentations | ST4.2 | Highlight

Nowcasting the Orbit Decay of Earth orbiting Satellites 

Lukas Drescher, Sofia Kroisz, Manuela Temmer, Sandro Krauss, Barbara Suesser-Rechberger, Saniya Behzadpour, and Torsten Mayer-Guerr

The FFG funded project SWEETS (space weather effects on low Earth orbiting satellites) covers the analysis of a large sample of more than 300 ICMEs (interplanetary coronal mass ejections) from 2002 to 2017 and how they relate to the orbit decay of satellites. Based on the results by Krauss et al. (2018, 2020), we investigate the correlation between the interplanetary magnetic field of ICMEs and the variation of the neutral density in the thermosphere. So far, the satellite drops were calculated from either accelerometer measurements or kinematic orbits for the satellite GRACE at a height of approximately 490 km. Presently, we are working on constructing kinematic orbits for satellites in various heights so we will be able to cover altitudes between 300 to 800 km and a wider timeframe. The algorithm is also going to be improved with respect to multiple ICME events and the calculation of a so-called “effective Bz” component and its duration.

With the correlation and the real-time in-situ magnetic field data from satellites at L1 we were able to construct a nowcast. The nowcast algorithm is the basis of a new service called SODA (Satellite Orbit DecAy) which will be implemented in the ESA Space Safety Program (Ionospheric Weather Expert Service Center).

How to cite: Drescher, L., Kroisz, S., Temmer, M., Krauss, S., Suesser-Rechberger, B., Behzadpour, S., and Mayer-Guerr, T.: Nowcasting the Orbit Decay of Earth orbiting Satellites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2776, https://doi.org/10.5194/egusphere-egu22-2776, 2022.

EGU22-2946 | Presentations | ST4.2

Accounting for Uncertainties in MSIS 2.0 

Piyush Mehta, Richard Licata, Daniel Weimer, Douglas Drob, W Kent Tobiska, and Jean Yoshi

Modeling of the upper atmosphere, specifically the thermosphere mass density, remains the primary source of uncertainty in satellite drag and orbital operations in low Earth orbit (LEO). The variations in mass density are dominated by changes in solar irradiance on the timescales of the solar cycle, however, short-term space weather changes can significantly impact the state of the thermosphere, especially during geomagnetic storms. Because of our limited understanding of such variations and the resulting inaccurate modeling, quantifying the uncertainty in density specification and forecasting becomes critical for space operations including decision making for collision avoidance and safeguarding of our space assets.

The Naval Research Laboratory’s MSIS model is one of the most widely used models in operations, especially in the commercial industry. Several different versions of the models have been developed, the most recent being MSIS 2.0. A new methodology for calibration of the MSIS model with exospheric temperatures inverted using accelerometer-derived density estimates has recently been developed. In this work, we apply a similar but updated methodology to the MSIS 2.0 model and use machine learning, specifically a neural network, to develop a version of the MSIS 2.0 model calibrated to the accelerometer-derived density estimates  that also provides reliable uncertainty estimates.

How to cite: Mehta, P., Licata, R., Weimer, D., Drob, D., Tobiska, W. K., and Yoshi, J.: Accounting for Uncertainties in MSIS 2.0, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2946, https://doi.org/10.5194/egusphere-egu22-2946, 2022.

EGU22-4842 | Presentations | ST4.2

Predicting the Bz magnetic field component from upstream in situ observations of coronal mass ejections using machine learning 

Martin Reiss, Christian Möstl, Rachel Bailey, Hannah Rüdisser, Ute Amerstorfer, Tanja Amerstorfer, Andreas Weiss, Jürgen Hinterreiter, and Andreas Windisch

Predicting the Bz magnetic field embedded in interplanetary coronal mass ejections (ICMEs), also called the Bz problem, is a core challenge in space weather research and prediction. We tackle this problem with a new approach by taking upstream in situ measurements of the ICME sheath region and the first few hours of the magnetic obstacle to predict the downstream Bz component. To do so, we trained a machine learning algorithm on 348 ICMEs (extracted from the open source ICMECATv2.0 catalog) observed by the Wind, STEREO-A, and STEREO-B satellites to predict the minimum value of Bz. The predictive tool was built to mimic a real-time scenario, where the ICMEs sweep over the spacecraft, which allows us to continually provide updates and improved predictions of Bz as time passes and more of the CME structure is observed. The final model, which is based on random forests, can predict the minimum value of Bz with a reasonable level of agreement compared to observations. In this presentation, we will discuss the main challenges we face in using a data-driven machine learning application to solve the Bz problem, and outline the lessons learned and future strategies for predicting and potentially mitigating the effects of ICMEs arriving at Earth.

How to cite: Reiss, M., Möstl, C., Bailey, R., Rüdisser, H., Amerstorfer, U., Amerstorfer, T., Weiss, A., Hinterreiter, J., and Windisch, A.: Predicting the Bz magnetic field component from upstream in situ observations of coronal mass ejections using machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4842, https://doi.org/10.5194/egusphere-egu22-4842, 2022.

EGU22-5210 | Presentations | ST4.2

Effects of CME removal and observation age on solar wind data assimilation 

Harriet Turner, Mathew Owens, and Matthew Lang

Accurate space weather forecasting requires knowledge of the solar wind conditions in near-Earth space. Data assimilation (DA) combines model output and observations to find an optimum estimation of reality and has led to large advances in terrestrial weather forecasting. It is now being applied to space weather forecasting. Here, we use solar wind DA to reconstruct the conditions from 30 solar radii to Earth's orbital radius and over all longitudes and produce solar wind speed forecasts. In this study, we assimilate observations from the Solar Terrestrial Relations Observatory (STEREO) and the Advanced Composition Explorer (ACE). Analysis of two periods of time, one in solar minimum and one in solar maximum, reveals that assimilating observations from multiple spacecraft is preferable over observations from a single spacecraft. The age of the observations also has an impact on forecast error, whereby the mean absolute error (MAE) increases by up to 23% when the forecast lead time exceeds the time associated with the longitudinal separation between the observing spacecraft and the forecast location. It was also found that removing CMEs from the DA input observations acts to reduce the forecast MAE by up to 10% through removal of false streams in the forecast time series. This work adds further evidence to the usefulness of the L5 space weather monitoring mission, but also shows that a mission to L4 would aid in future solar wind DA forecasting capabilities. 

How to cite: Turner, H., Owens, M., and Lang, M.: Effects of CME removal and observation age on solar wind data assimilation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5210, https://doi.org/10.5194/egusphere-egu22-5210, 2022.

The total electron content (TEC) over the Iberian Peninsula was modeled using a PCA-NN models based on the decomposition of the observed TEC series using the principal component analysis (PCA) and reconstruction of the daily mean TEC and daily PCA modes’ amplitudes by different types of neural networks (NN) using several types of space weather parameters as predictors. Lags of 1 and 2 days between the TEC and space weather parameters are used.

Two main goals are set:

  • To find a NN configuration(s) that produces forecasts of reasonable quality with minimal amount of input data
  • To find a best set of space weather parameters that work as predictors for PCA-NN models

Here we present preliminary results related to the second goal: PCA-NN models with different sets of predictors are compared. Among predictors we consider proxies for the solar UV and XR fluxes, number of the solar flares of different types, parameters of the solar wind and of the interplanetary magnetic field, and geomagnetic indices.

How to cite: Morozova, A., Barata, T., and Barlyaeva, T.: Comparison of the performance of PCA-NN models for daily mean TEC over the Iberian Peninsula: the role of space weather parameters as predictors for TEC, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5220, https://doi.org/10.5194/egusphere-egu22-5220, 2022.

EGU22-5411 | Presentations | ST4.2

Automated tool for estimating field line resonance frequencies using ground-based magnetometer measurements 

Ermanno Pietropaolo, Raffaello Foldes, Alfredo Del Corpo, Massimo Vellante, and Raffaele Marino

Ground-based magnetometer stations offer a valuable and easy-to-access tool for sounding the Earth’s magnetic field disturbances in the inner magnetosphere with a multi-viewpoint system. Using Ultra-Low Frequency (ULF) measurements recorded from meridional aligned stations, it is possible to infer the Field Line Resonance (FLR) frequencies, using a well-established technique, namely the gradient method (Baransky et al. 1985 and Waters et al. 1991). Based on this technique, several authors developed (semi-)automated tools for estimating FLR from ground-based magnetometer measurements. Recently it has been observed (Foldes et al., 2021) that the Machine Learning (ML) approach represents a valuable tool to estimate FLRs from Fourier cross-phase spectra. However, it is commonly known that detecting FLRs using cross-phase spectra may often be unfeasible due to data gaps, noisy signals and/or quiescent ULF wave periods. To handle these situations, we implement an ML classification algorithm to detect periods in which resonance frequencies are clearly observable and thus can be easily estimated. Our algorithm can distinguish between periods with observed frequency from the others; moreover, it can determine if the considered field line is crossing the plasma boundary layer (PBL) at a given time. The results of our method are validated for a particular pair of stations (at L=2.9), along the Equatorial quasi-Meridional Magnetometer Array (EMMA), which provides an extensive data set with several different geomagnetic conditions. This kind of approach in the analysis of ground-based magnetic field measurements, combined in a two-stage ML pipeline with a regression algorithm (as in Foldes et al., 2021), may provide a prominent tool for monitoring the plasmasphere dynamics using a completely automated system.

How to cite: Pietropaolo, E., Foldes, R., Del Corpo, A., Vellante, M., and Marino, R.: Automated tool for estimating field line resonance frequencies using ground-based magnetometer measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5411, https://doi.org/10.5194/egusphere-egu22-5411, 2022.

EGU22-7606 | Presentations | ST4.2

First step of data assimilation technique Parametric Kalman Filter adaptation to Space Weather 

Martin Sabathier, Olivier Pannekoucke, and Vincent Maget

Space weather is of interest to the satellite industry as the quantity of radiation can rapidly change in the Earth’s radiation belts during solar events (called geomagnetic storms). Radiation belts dynamics are complex and modelled at ONERA by an advection-diffusion equation with added sources and losses terms: the Salammbô model. For several years, data assimilation has been used to reduce the uncertainties inherent to imprecise physics and numerical assumptions used in the Salammbô model alone. An Ensemble Kalman Filter has thus been developed and the overall process has been optimized from the physics-based point of view.

To improve the benefits of data assimilation and thus the accuracy of the prevision, we are considering the implementation of a Parametric Kalman Filter (PKF) [1,2,3]. We think it is a pertinent choice to reduce computational costs and use the information on the uncertainties dynamics brought by the evolution equation. The PKF also allows direct access to the variance and correlation length-scale within the domain, helping with uncertainty estimation. The prevision step of the PKF uses the dynamics of a system to yield the dynamics for a set of parameters (usually the variance and a local anisotropy tensor). These parameters are then used to approximate the covariance matrix coefficients used for the analysis and uncertainty estimation.

As mentioned above, the data assimilation technique currently used at ONERA is a slightly adapted Ensemble Kalman Filter (EnKF) which has mostly been used as a black box to merge the model prevision and the observations. In order to better understand uncertainties dynamics in the case of radiation belts, we run diagnostics on the ensemble to compute the PKF parameters and study their dynamics as propagated by the EnKF. This study shows encouraging results regarding the compatibility of the Salammbô model with the PKF.

Following the work of O.Pannekoucke in [1] and using SymPKF library [4], we find the dynamics of the parameters for a 1D heterogeneous diffusion equation resembling the equation governing the radiation belts. This test case allows for quick and easy study of particularities not covered in [1,2] such as boundary conditions handling with the PKF.

During my presentation I will introduce the PKF and the ensemble diagnostics with examples related to the Salammbô model. I will then compare the way we handle boundary conditions for the EnKF and the PKF.

 

[1] Pannekoucke, O., Bocquet, M., and Ménard, R.: Parametric covariance dynamics for the nonlinear diffusive Burgers equation, Nonlin. Processes Geophys., 25, 481–495, https://doi.org/10.5194/npg-25-481-2018, 2018.

[2] Olivier Pannekoucke, Sophie Ricci, Sebastien Barthelemy, Richard Ménard & Olivier Thual (2016) Parametric Kalman filter for chemical transport models, Tellus A: Dynamic Meteorology and Oceanography, 68:1, 31547, DOI: 10.3402/tellusa.v68.31547

[3] Olivier Pannekoucke (2021) An anisotropic formulation of the parametric Kalman filter assimilation, Tellus A: Dynamic Meteorology and Oceanography, 73:1, 1-27, DOI: 10.1080/16000870.2021.1926660

[4] Olivier Pannekoucke, Philippe Arbogast: SymPKF: a symbolic and computational toolbox for the design of parametric Kalman filter dynamics, arXiv(physics):2103.09226, 2021.

How to cite: Sabathier, M., Pannekoucke, O., and Maget, V.: First step of data assimilation technique Parametric Kalman Filter adaptation to Space Weather, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7606, https://doi.org/10.5194/egusphere-egu22-7606, 2022.

EGU22-8377 | Presentations | ST4.2

Evaluating Auroral Forecasts Against Satellite Observations 

Michaela Mooney, Mike Marsh, Colin Forsyth, Michael Sharpe, Teresa Hughes, Suzy Bingham, David Jackson, Jonathan Rae, and Gareth Chisham

The aurora is a readily visible phenomenon of interest to many members of the public. However, the aurora and associated phenomena can also significantly impact communications, ground-based infrastructure and high-altitude radiation exposure. Forecasting the location of the auroral oval is therefore a key component of space weather forecast operations. A version of the OVATION-Prime 2013 auroral precipitation model was implemented for operational use at the UK Met Office Space Weather Operations Centre (MOSWOC), delivering a 30-minute forecast of the auroral oval location and the probability of observing the aurora.

Using weather forecast evaluation techniques, we evaluate the ability of the operational version of the OVATION-Prime 2013 model to predict the location of the auroral oval and the probability of aurora occurring. We compare the forecasts with auroral boundaries determined from data from the IMAGE satellite between 2000 and 2002. Our analysis shows that the operational model performs well at predicting the location of the auroral oval, with a relative operating characteristic (ROC) score of 0.82. We analyse the model performance in detail during different levels of geomagnetic activity levels and in different spatial locations.

How to cite: Mooney, M., Marsh, M., Forsyth, C., Sharpe, M., Hughes, T., Bingham, S., Jackson, D., Rae, J., and Chisham, G.: Evaluating Auroral Forecasts Against Satellite Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8377, https://doi.org/10.5194/egusphere-egu22-8377, 2022.

EGU22-8476 | Presentations | ST4.2

Perspectives on the thermosphere response to extreme magnetic storms: Current status of neutral mass density modeling 

Denny Oliveira, Eftyhia Zesta, Piyush Mehta, Richard Licata, Marcin Pilinski, W. Kent Tobiska, and Hisashi Hayakawa

Orbits of human assets such as satellites, crewed spacecraft and stations in low-Earth orbit (LEO) are very sensitive to the highly dynamic environment in which they fly. Atmospheric drag caused by the interaction between the orbiting object and the local thermospheric neutral mass density affects the satellite’s lifetime and orbital tracking, which becomes increasingly inaccurate or uncertain with storm intensity. Given the planned increase of government and private satellite presence in LEO, the need for accurate density predictions for collision avoidance and lifetime optimization, particularly during extreme events, has become an urgent matter and requires comprehensive international collaboration. Additionally, long-term solar activity models and historical data suggest that the solar activity will significantly increase in the following years and decades. In this presentation, we briefly summarize the main achievements in the research of thermospheric density response to magnetic storms occurring particularly after the launching of many satellites with state-of-the-art accelerometers for density determination (CHAMP, GRACE, GOCE, Swarm). We argue that specification models (e.g., HASDM) perform reasonably well during storm main and recovery phases of extreme storms, but forecasting models (e.g., JB2008) do not perform well throughout the storm cycle. We will discuss how forecasting models can be improved by looking into two directions: first, to the past, by adapting historical extreme storm datasets for density predictions, and second, to the future, by facilitating the assimilation of large-scale data sets that will be collected in future events. We invite the community to the discussion on the possible use of several hundreds of satellites with lower resolution density measurements along with data assimilation schemes or the use of ~100 high precision tracked satellites as a more effective approach for future density determinations.

How to cite: Oliveira, D., Zesta, E., Mehta, P., Licata, R., Pilinski, M., Tobiska, W. K., and Hayakawa, H.: Perspectives on the thermosphere response to extreme magnetic storms: Current status of neutral mass density modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8476, https://doi.org/10.5194/egusphere-egu22-8476, 2022.

EGU22-8782 | Presentations | ST4.2

Chaos and Predictability in vTEC time series 

Massimo Materassi, Yenca Migoya-Orue, Tommaso Alberti, Sandro Radicella, and Giuseppe Consolini

Modeling the Earth’s ionosphere is a big challenge, due to the complexity of the system. Any ionospheric model misses the behavior of the real system for some fluctuating component, that appears almost impossible to predict, and is particularly threatening for the human technologies (e.g., GNSS navigation). While producing models extremely rich, including many physical agents acting on the Earth’s ionosphere, it is necessary to understand whether the residual, non-modeled component is predictable in principle as a “simple" dynamical system, or is conversely so chaotic to be practically stochastic, and should be treated probabilistically.

The question of how chaotic and how predictable the time series of vertical total electron content (vTEC) are, depending on the different locations and solar activity conditions, is dealt with by employing tools of dynamical system theory.

In particular, we calculate the correlation dimension D2 and the Kolmogorov entropy rate K2 for the vTEC time series at different latitudes in both northern and southern hemispheres and during both high and low solar activity periods.

The quantity D2 is a proxy of the degree of chaos and dynamical complexity: the larger D2 is, the higher the number of dynamical variables needed to describe the phenomenon is. Instead, K2 measures the speed of destruction of the mutual information between the signal and a delayed copy of it, so that (K2)-1 is a sort of maximum time horizon for predictability.

The analysis of the D2 and K2 for the vTEC time series will then allow to give a measure of chaos and predictability of the Earth ionosphere. Being such analysis performed for different locations and different solar activity conditions, these characteristics will indicate possible differences depending on location.

How to cite: Materassi, M., Migoya-Orue, Y., Alberti, T., Radicella, S., and Consolini, G.: Chaos and Predictability in vTEC time series, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8782, https://doi.org/10.5194/egusphere-egu22-8782, 2022.

EGU22-11658 | Presentations | ST4.2

Reconstructing the Dynamics of the Outer Electron Radiation Belt by Means of the Standard and Ensemble Kalman Filter With the VERB-3D Code 

Angelica M. Castillo Tibocha, Jana de Wiljes, Yuri Y. Shprits, and Nikita A. Aseev

Reconstruction and prediction of the state of the near-Earth space environment is important for anomaly analysis, development of empirical models, and understanding of physical processes. Accurate reanalysis or predictions that account for uncertainties in the associated model and the observations, can be obtained by means of data assimilation. The ensemble Kalman filter (EnKF) is one of the most promising filtering tools for nonlinear and high dimensional systems in the context of terrestrial weather prediction. In this study, we adapt traditional ensemble-based filtering methods to perform data assimilation in the radiation belts. By performing a fraternal twin experiment, we assess the convergence of the EnKF to the standard Kalman filter (KF). Furthermore, with the split-operator technique, we develop two new three-dimensional EnKF approaches for electron phase space density that account for radial and local processes, and allow for reconstruction of the full 3D radiation belt space. The capabilities and properties of the proposed filter approximations are verified using Van Allen Probe and GOES data. Additionally, we validate the two 3D split-operator Ensemble Kalman filters against the 3D split-operator KF. We show how the use of the split-operator technique allows us to include more physical processes in our simulations and is a computationally efficient data assimilation tool that delivers an accurate approximation of the optimal KF solution, and is suitable for real-time forecasting.

How to cite: Castillo Tibocha, A. M., de Wiljes, J., Shprits, Y. Y., and Aseev, N. A.: Reconstructing the Dynamics of the Outer Electron Radiation Belt by Means of the Standard and Ensemble Kalman Filter With the VERB-3D Code, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11658, https://doi.org/10.5194/egusphere-egu22-11658, 2022.

EGU22-13001 | Presentations | ST4.2

Monitoring Van Allen Radiation Belts using EU Galileo satellites: Observations and Data Products of energetic particle fluxes 

Ingmar Sandberg, Georgios Provatas, Constantinos Papadimitriou, Sigiava Aminalragia-Giamini, Keith Ryden, and Hugh Evans

The Environmental Monitoring Units (EMU), on-board two satellites of the EU Galileo constellation, monitor the radiation environment along the GNSS orbit providing measurements of the energetic electron fluxes in the outer Van Allen Belt. With new calibration studies that take into account more realistic shielding provided by the spacecraft and the characteristics of the encountered environment along the satellite orbit, we have derived a new version of the GSAT/EMU Level 1 dataset that provides high quality validated fluxes of trapped energetic electrons within the 0.2-4.5 MeV energy range.  

In this work, we present an overview of the EMU measured electron fluxes over the last five years including recently completed validation studies with Arase [ERG] and RBSP energetic electron measurements. The new dataset, available to users from European member states registered at https://gssc.esa.int, will be used in the assimilation processes and/or the validation of the ONERA Salammbô electron radiation belt models - under the EU Safespace activity and ESA S2P RBFAN activity - leading to improved forecasts of the state of the outer belt. In addition, the quality of the time-coverage of the dataset permits their use in the development and/or evaluation of quantitative radiation environment specification models.

 

This work has received funding from the European Union’s Horizon 2020 research and innovation programme "SafeSpace" under grant agreement No 870437, from the European Space Agency activity "Cross Calibration EMU Dataset with RBSP" under ESA Contract 4000135823/21/NL/GLC/mkn and the “SSA P3-SWE-X Space Environment Nowcast and Forecast Development” activity under ESA Contract 4000131381/20/D/CT.

How to cite: Sandberg, I., Provatas, G., Papadimitriou, C., Aminalragia-Giamini, S., Ryden, K., and Evans, H.: Monitoring Van Allen Radiation Belts using EU Galileo satellites: Observations and Data Products of energetic particle fluxes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13001, https://doi.org/10.5194/egusphere-egu22-13001, 2022.

EGU22-13037 | Presentations | ST4.2

Progress On a New Interactive 3-Dimensional Data Viewer for the Enlil Solar Wind Model 

Christopher Pankratz, Greg Lucas, Jenny Knuth, Dusan Odstrcil, James Craft, and Thomas Berger

One of the critical models in space weather forecasting is the Enlil solar wind prediction model that can inform space weather forecasters the direction and speed of coronal mass ejections CMEs. The Enlil code calculates the propagation of the solar wind throughout the 3D heliosphere, but current visualization capabilities in the forecasting offices are restricted to 2D planes intersecting Earth. This limits forecasters to only be able to view CME properties that are traveling directly in the plane of the Earth.

 

Here, we present an update on a new visualization capability being developed to take advantage of the full Enlil 3D data volume and interactively visualize the CME expansion out of the plane of the Earth.  We have been collaborating closely with researchers and forecasters at the Met Office in the UK and the Space Weather Prediction Center (SWPC) in the USA to develop a tool to enable full view of the heliosphere in a manner that can be tailored to these different types of users. To accomplish this, we are deploying the Enlil solar wind model into a scalable Cloud-based model staging platform computing environment, which will allow the full 3D Enlil output to reside in-situ with the visualization engine.  We will discuss our progress in deploying and running the Enlil model in the Cloud-based testbed environment, the process of interacting directly with space weather forecasters to design a new interactive 3D visualization tool that meets their needs, and will demonstrate use of the actual visualization tool, which is deployed and running in the Amazon Web Services (AWS) Cloud environment.

How to cite: Pankratz, C., Lucas, G., Knuth, J., Odstrcil, D., Craft, J., and Berger, T.: Progress On a New Interactive 3-Dimensional Data Viewer for the Enlil Solar Wind Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13037, https://doi.org/10.5194/egusphere-egu22-13037, 2022.

EGU22-13384 | Presentations | ST4.2 | Highlight

Variability of ionospheric plasma studied and modelled based on data from the Swarm satellites 

Yaqi Jin, Wojciech J. Miloch, Lucilla Alfonsi, Luca Spogli, Jaroslav Urbář, Claudio Cesaroni, Antonio Cicone, Alan G. Wood, James Rawlings, Golnaz Sahtahmassebi, Lasse B.N. Clausen, Per Høeg, Jaime Muñoz Redondo, Maria José Brazal Aragón, and Paweł Wojtkiewicz

The state of the Earth’s ionosphere is an important aspect of the Sun-Earth system. It reflects  dynamical coupling of the solar wind with the Earth’s magnetosphere. Its understanding has also an applied aspect in the context of the space weather effects. For example, ionospheric plasma irregularities impact the propagation of radio waves, and they can degrade radio communication or positioning with the Global Navigation Satellite Systems (GNSS). The European Space Agency’s Swarm+ 4DIonosphere initiative aims at advancing our understanding and characterisation of the processes in the ionosphere to better model and eventually predict the state of the ionosphere. Within this framework, through the project “Swarm Variability of Ionospheric Plasma” (Swarm-VIP), we analyse spatiotemporal characteristics of ionospheric plasma at different geomagnetic latitudes and uncover coupling between various scales in the ionosphere. Taking advantage of the orbital characteristics of the Swarm satellites and using complementary analysis techniques, such as wavelets or Fast Iterative Filtering, we ascertain the dominant scales at given geomagnetic conditions. The result of the study is a semi-empiric model of the ionosphere based on the generalised linear modeling approach. The model determines the probability of occurrence of different scales in ionospheric plasma with respect to geomagnetic conditions. It also gives insight into ionospheric structuring and related space weather effects. The Swarm-VIP model is provided globally, along the whole orbits of the Swarm satellites, and a special emphasis is put on the polar regions, Arctic and Antarctica, and the European sector, where the validation study is carried out with a network of the ground-based instruments.

How to cite: Jin, Y., Miloch, W. J., Alfonsi, L., Spogli, L., Urbář, J., Cesaroni, C., Cicone, A., Wood, A. G., Rawlings, J., Sahtahmassebi, G., Clausen, L. B. N., Høeg, P., Redondo, J. M., Brazal Aragón, M. J., and Wojtkiewicz, P.: Variability of ionospheric plasma studied and modelled based on data from the Swarm satellites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13384, https://doi.org/10.5194/egusphere-egu22-13384, 2022.

The space environment near Earth is constantly subjected to changes in the solar wind flow generated at the Sun. Examples of this variability are the occurrence of powerful solar disturbances, such as coronal mass ejections (CMEs). The impact of CMEs on the Earth's magnetosphere perturbs the geomagnetic field causing the occurrence of geomagnetic storms. Such extremely variable geomagnetic fields trigger geomagnetic effects measurable not only in the geospace but also in the ionosphere, upper atmosphere, and on the ground. For example, during extreme events, rapidly changing geomagnetic fields generate intense geomagnetically induced currents (GICs). In recent years, GIC impact on the power networks at middle and low latitudes has attracted attention due to the expansion of large-scale power networks into these regions. This work presents the analysis of the geoelectric field determined by the use of the MA.I.GIC. (Magnetosphere - Ionosphere - Ground Induced Current) model, on May 12, 2021 Geomagnetic Storm over the northern hemisphere. In addition, we discriminate between the ionospheric and magnetospheric origin contribution on the geoelectric field in Europe and on the Northern America in order to evaluate their relative contribution to the GIC amplitude.

How to cite: Piersanti, M., D'Angelo, G., and Recchiuti, D.: On the possible magnetospheric and ionospheric sources of the geoelectric field variations during the May 2021 Geomagnetic storm., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1249, https://doi.org/10.5194/egusphere-egu22-1249, 2022.

EGU22-1416 | Presentations | EMRP2.15

Extraction of ground magnetic signatures from solar quiet current systems in sub-auroral regions 

Veronika Haberle, Aurélie Marchaudon, Aude Chambodut, and Pierre-Louis Blelly

In order to monitor space weather events and their impacts, ground magnetic field data has proven to be a long-lasting and powerful source of information. For the determination of space weather effects, it is essential to extract and understand the evolution of the quiet-time magnetic field. However, the data shows a high degree of complexity since the Earth’s magnetic field is a superposition of sources that cover a broad amplitude and frequency spectrum. In sub-auroral regions, it is well understood that the solar quiet current system contributes to the quiet signal with smooth patterns that depend on season and local time, having distinct periods of 24 hours and beneath.

In this work, we apply signal filtering techniques on time-series magnetic data from ground observatories in sub-auroral regions. In order to extract the solar quiet current contributions, we use its specific periods of 24h and beneath and analyse the results with respect to season, local time, and day-to-day variability between 1991 and 2019. Careful investigations and interpretation of the contributing sources are given, confirming the main contribution to the filtered signal is the solar quiet current system. This implies that the filter approach is able to extract the quiet magnetic field variations and due to its simplicity may be used for real-time determination of the quiet magnetic field, including magnetic baselines. 

How to cite: Haberle, V., Marchaudon, A., Chambodut, A., and Blelly, P.-L.: Extraction of ground magnetic signatures from solar quiet current systems in sub-auroral regions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1416, https://doi.org/10.5194/egusphere-egu22-1416, 2022.

EGU22-1797 | Presentations | EMRP2.15

A parameter for the solar cycle variation in geomagnetic activity as quantified by bursts in the AE and SMR indices 

Aisling Bergin, Sandra Chapman, Nicholas Moloney, and Nicholas Watkins

Geomagnetic storms have the potential for significant impact on a wide range of technologies, including aviation, communications and power transmission grids. The likelihood of occurrence of geomagnetic storms varies with the solar cycle of level of activity, and each solar cycle has a unique amplitude and duration. The space weather response at earth then varies within and between successive solar cycles and can be characterized by the statistics of bursts, that is, time-series excursions above a threshold, in geomagnetic indices derived from ground based magnetometer observations. We consider non-overlapping 1 year samples of the minute-resolution auroral electrojet index (AE) and the minute-resolution SuperMAG-based ring current index (SMR), across the last four solar cycles. These indices respectively characterize high latitude and equatorial geomagnetic disturbances. We propose that average burst duration T and burst return period R (that is, the time between successive upcrossings of the threshold) form an activity parameter, T/R [1] which characterizes the fraction of time the magnetosphere spends, on average, in an active state for a given burst threshold. If the burst threshold takes a fixed value, T/R for SMR tracks sunspot number, while T/R for AE peaks in the solar cycle declining phase. Level crossing theory directly relates T/R to the observed index value cumulative distribution function (cdf). For burst thresholds at fixed quantiles, we find that the probability density functions of T and R each collapse onto single empirical curves for AE at solar cycle minimum, maximum, and declining phase and for -SMR at solar maximum. Moreover, underlying empirical cdf tails of observed index values collapse onto common functional forms specific to each index and cycle phase when normalized to their first two moments. Together, these results offer operational support to quantifying space weather risk which requires understanding how return periods of events of a given size vary with solar cycle strength.

 

[1] A. Bergin, S. C. Chapman, N. Moloney, N. W. Watkins, Variation of geomagnetic index empirical distribution and burst statistics across successive solar cycles, J. Geophys. Res, in press (2022)

How to cite: Bergin, A., Chapman, S., Moloney, N., and Watkins, N.: A parameter for the solar cycle variation in geomagnetic activity as quantified by bursts in the AE and SMR indices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1797, https://doi.org/10.5194/egusphere-egu22-1797, 2022.

EGU22-2259 | Presentations | EMRP2.15

Power density dissipated by field-aligned currents in the topside ionosphere 

Fabio Giannattasio, Giuseppe Consolini, Igino Coco, Michael Pezzopane, and Alessio Pignalberi

The response of the magnetosphere-ionosphere (MI) system to the forcing by plasma of solar origin gives rise to several phenomena relevant to Space Weather. In particular, part of the energy injected into the ionosphere by means of field-aligned currents (FACs) connecting the magnetosphere with the high-latitude ionosphere is converted into mechanical energy and dissipated via Joule heating. Under reasonable assumptions, in the direction parallel to the geomagnetic field the only relevant contribution to dissipation is from the Ohmic term. Dissipated power density may significantly affect the physical parameters characterizing the upper ionosphere, such as electron temperature and density, and alter its chemical composition. This can result, for example, in the increased atmospheric drag and affect the satellite orbits. For this reason, understanding the dissipation of FACs in the topside ionosphere is important to shed light on the physical processes involved in MI coupling. Power density dissipated by FACs in crossing the topside ionosphere can be estimated by using Swarm data. Here, for the first time, we show statistical maps of power density features dissipated by FACs by using six-year time series of electron density and temperature data acquired by the Langmuir Probes onboard the Swarm A satellite (flying at an altitude of about 460 km) at 1 s cadence, together with the field-aligned current density product provided by the ESA’s Swarm Team at the same cadence. Maps of the same quantity under different levels of geomagnetic activity are also shown and discussed in light of the previous literature.

This work is partially supported by the Italian National Program for Antarctic Research under contract N. PNRA18 00289-SPIRiT and by the Italian MIUR-PRIN grant 2017APKP7T on "Circumterrestrial Environment: Impact of Sun-Earth Interaction".

How to cite: Giannattasio, F., Consolini, G., Coco, I., Pezzopane, M., and Pignalberi, A.: Power density dissipated by field-aligned currents in the topside ionosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2259, https://doi.org/10.5194/egusphere-egu22-2259, 2022.

EGU22-3338 | Presentations | EMRP2.15

Geomagnetically Induced Currents over Kazakhstan during Large Geomagnetic Storms 

Saule Mukasheva, Alexey Andreyev, Vitaliy Kapytin, and Olga Sokolova

The paper shows that during very large magnetic storms (VLMS), the energy systems of Kazakhstan are exposed to geomagnetically induced currents for quite a long time (from tens of minutes to several hours). The minute values of the magnetic field vector B or its components Bx, By, Bz during four very large geomagnetic storms with a local geomagnetic activity K-index≥7 were used to calculate the values of geomagnetically induced currents:

- September 26-28, 2011, VLMS, Sc, duration 54 h 00 min, K-index =7;

- June 22-25, 2015, VLMS, Sc, duration 78 h 30 min, K-index =8;

- October 24-28, 2016, VLMS, duration 93 h 00 min, K-index =7;

- May 12-17, 2021, VLMS, Sc, duration 17 h 25 min, K-index =7.

Sc – a sudden commencement of strong storms.

The data of four magnetic observatories of the INTERMAGNET network, whose geomagnetic latitudes are close to the geomagnetic latitudes of the southern and northern borders of Kazakhstan were considered: Alma-Ata Observatory, Kazakhstan (code AAA, 43.25°N, 76.92°E); Novosibirsk Observatory, Russia (code NVS, 54.85N, 83.23E); Irkutsk Observatory, Russia (code IRT, 52.17°N, 104.45°E) and the Beijing Ming Tombs Observatory, Beijing, China (code BMT, 40.3°N, 116.2°E).

Variations of the Bx component of the geomagnetic field during the four considered very large magnetic storms according to the observatories AAA, NVS, IRT, BMT showed variability from 50 nT to 150 nT for several hours.

Also, based on measurements of geomagnetic observatories AAA, NVS, IRT, BMT, the analysis of variations of the horizontal component H of the magnetic field vector and its time derivative (dH/dt) was carried out. Histograms of the distribution dH/dt and histograms of the distribution of the directions H and dH/dt are constructed.

It is shown that the energy systems of Kazakhstan are exposed to geomagnetically induced currents when dH/dt/ varies from 17 nT/min and more. The geomagnetic-induced current is estimated based on the calculation that the electromotive force of self-induction is proportional to the rate of change in the magnetic field strength. According to preliminary calculations, the values of geomagnetic-induced currents are fractions of mA. For more accurate calculations, it is necessary to take into account the topology of the electrical system, the composition of the underlying surface and other factors that determine the degree of susceptibility of individual elements of the power system.

This research has been/was/is funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP09259554).

How to cite: Mukasheva, S., Andreyev, A., Kapytin, V., and Sokolova, O.: Geomagnetically Induced Currents over Kazakhstan during Large Geomagnetic Storms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3338, https://doi.org/10.5194/egusphere-egu22-3338, 2022.

EGU22-4513 | Presentations | EMRP2.15

Markovian features of the Super-MAG Auroral Electrojet Index 

Simone Benella, Giuseppe Consolini, Mirko Stumpo, and Tommaso Alberti

Earth's magnetospheric dynamics displays dynamical complexity during magnetic substorms and storms. This complex dynamics includes both  stochastic and deterministic features, which manifest at different timescales. In this work, we investigate the stochastic properties of the  magnetospheric substorm dynamics by analysing the Markovian character of the SuperMAG SME time series, which is used as a proxy of the energy  deposition rate in the auroral regions. In detail, performing the Chapman-Kolmogorov test, the SME dynamics appears to satisfy the Markov condition  below 100 minutes. Moreover, the Kramer-Moyal analysis allows to highlight that a purely diffusive process is not representative of the magnetospheric  dynamics, as the fourth order Kramers-Moyal coefficient does not vanish. As a consequence, we show that a model comprising both diffusion and  Poisson-jump processes is more suitable to reproduce the SME dynamical features at small scales. A discussion of the similarities and differences  between this model and the actual SME properties is provided with a special emphasis on the metastability of the Earth’s magnetospheric dynamics.  Finally, the relevance of our results in the framework of Space Weather is also addressed.

How to cite: Benella, S., Consolini, G., Stumpo, M., and Alberti, T.: Markovian features of the Super-MAG Auroral Electrojet Index, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4513, https://doi.org/10.5194/egusphere-egu22-4513, 2022.

EGU22-4570 | Presentations | EMRP2.15 | Highlight

Building a GIC forecasting tool based on geomagnetic and solar wind data: challenges and future avenues 

Rachel L. Bailey, Roman Leonhardt, Christian Möstl, Ciaran Beggan, Martin Reiss, Ankush Bhaskar, and Andreas Weiss
Measurements of geomagnetically induced currents (GICs) in the Austrian power transmission grid have been carried out since 2014 at multiple locations. Following an analysis of the scales of GICs across the grid, we now look into forecasting the GICs from incoming solar wind data. Using nearby geomagnetic field measurements stretching back 26 years, we can estimate the local geoelectric field and consequently the GICs over longer time periods. We apply a machine learning method based on recurrent neural networks to this dataset combined with solar wind data as input. In this talk, we present the final method to forecast both the local geoelectric field E and the GICs in substations in the Austrian power grid, with our model results being compared to GIC measurements from recent years. We will discuss the current status of the model, outline limitations, and consider future applications.

How to cite: Bailey, R. L., Leonhardt, R., Möstl, C., Beggan, C., Reiss, M., Bhaskar, A., and Weiss, A.: Building a GIC forecasting tool based on geomagnetic and solar wind data: challenges and future avenues, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4570, https://doi.org/10.5194/egusphere-egu22-4570, 2022.

EGU22-4733 | Presentations | EMRP2.15

Swarm Fast Track spherical harmonic model of the external magnetic field to degree and order 3 

Natalia Gomez Perez and Ciaran Beggan

The development of satellite measurements over the past four decades has allowed us to understand the magnetic field in the Earth environment at higher temporal and spatial resolution than before. This is most evident for satellite ensembles such as ESA’s Swarm constellation which allows simultaneous global coverage with three independent satellites.

Thanks to Swarm’s particular configuration, we can take advantage of the Local Time sampling difference between Swarm A/C and Swarm B in order to estimate the low degree variation of the external magnetic field in latitude and longitude. We separate the external and induced fields measured at satellite altitude, and obtain the spherical harmonic decomposition of each source to degree and order 3 twice per day. However, there is a trade-off between spatial and temporal resolution and clear disadvantages occur when the measured field varies rapidly during a geomagnetic storm, since the method used will result in coefficients of the averaged field over the chosen time interval rather than the peaks.

We compare our results with previous models of the external field during the St Patrick storm 2015, which used up to four different local time simultaneous coverage, as well as during quiet times and lesser storms using our own solutions. We find good agreement in each case.

In this talk we will describe the algorithm and methodology used and show results over the lifetime of the Swarm mission to date (2013-). A new daily product for the Swarm mission (MMA_SHA_2E) is being developed.

How to cite: Gomez Perez, N. and Beggan, C.: Swarm Fast Track spherical harmonic model of the external magnetic field to degree and order 3, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4733, https://doi.org/10.5194/egusphere-egu22-4733, 2022.

EGU22-5792 | Presentations | EMRP2.15

Utilisation of geomagnetic data and indices for GIC applications 

Larisa Trichtchenko

The development of mitigation capabilities to counteract the detrimental impacts of space weather on critical ground infrastructure, such as power lines, pipelines and cables, depends on the availability of the observations of their causes as well as monitoring of the subsequent results.
Although direct monitoring of critical infrastructure response to GeoMagnetic Disturbances (GMD) has become more advanced in recent years, observations of geomagnetic variations continue to play the most important role in all aspects of development of safe and robust operational procedures and technology, from the forecast of geomagnetically induced currents (GIC) to their climatological studies.
This presentation shows how different types of geomagnetic data are utilised, from 3-hour and 1-hour geomagnetic indices to 1 sec. geomagnetic data, and from real-time to multi-year climatology in order to provide forecasts of GIC, identify the effects of different geomagnetic patterns on infrastructure response or provide “climatology” for network design considerations.  

How to cite: Trichtchenko, L.: Utilisation of geomagnetic data and indices for GIC applications, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5792, https://doi.org/10.5194/egusphere-egu22-5792, 2022.

EGU22-6037 | Presentations | EMRP2.15

Statistical and spectral study of geomagnetic storm forecasting 

Laurentiu Asimopolos, Natalia-Silvia Asimopolos, Alexandru Stanciu, and Adrian-Aristide Asimopolos

The purpose of this study is to analyze the associated spectrum of geomagnetic field, frequencies intensity and the time of occurrence of geomagnetic storms. Also, we set out to analyze the possibility of predicting these geomagnetic storms.

A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by solar coronal mass ejections, coronal holes or solar flares. Solar wind shock wave typically strikes the Earth’s magnetic field 24 to 36 hours after the event.

This only happens if the shock wave travels in a direction toward Earth. The solar wind pressure on the magnetosphere will increase or decrease depending on the Sun's activity. These solar wind pressure changes modify the electric currents in the ionosphere. The data used in this paper are acquired within the Surlari Observatory, and additional information to characterize the geomagnetic storms analyzed, we obtained from the specialized sites such as www.intermagnet.org and www.noaa.gov. Information about geomagnetic data from other observatories, as well as planetary physical parameters allowed us to perform comparative studies between the data recorded in different observatories.

We calculated the variation of the correlation coefficients, with mobile windows of various sizes, for the recorded magnetic components at different latitudes and latitudes. Also, we have used for this purpose a series of filtering algorithms, spectral analysis and wavelet with different mather functions at different levels.

Wavelets allow local analysis of magnetic field components through variable frequency windows. Windows that contain longer time intervals allow us to extract low-frequency information, average ranges of different sizes lead to extraction of medium frequency information, and very narrow windows highlight the high frequencies or details of the analyzed signals. The wavelet functions describe the orthogonal bases with signal approximation properties, while the orthonormal bases in the Fourier analysis are made up of sinusoidal waves.

Estimation of geomagnetic field disturbances is similar to the standard problem of estimating a signal disturbed by signal theory.

The term noise refers to any modification that changes the periodic or quasi-periodic characteristics of the original signal.

The Dst index is used to assess the severity of geomagnetic storms and to determine the effects of the solar wind on space and terrestrial infrastructures and is very important to be able to predict the effects of the geomagnetic storm.

The numerical experiments presented in this paper are part of different methodological categories, with the same purpose, but with different approaches. The common goal is the prediction of geomagnetic disturbances and the methodologies used comparatively are Fourier spectral deconvolution, autoregressive models on time series and recurrent Long Short Term Memory (LSTM) neural networks that are capable of long-term dependence.

How to cite: Asimopolos, L., Asimopolos, N.-S., Stanciu, A., and Asimopolos, A.-A.: Statistical and spectral study of geomagnetic storm forecasting, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6037, https://doi.org/10.5194/egusphere-egu22-6037, 2022.

EGU22-6096 | Presentations | EMRP2.15

Pressure-Gradient current at high latitude from Swarm measurements 

Giulia Lovati, Paola De Michelis, Giuseppe Consolini, and Francesco Berrilli

The pressure-gradient current is among the weaker ionospheric current systems arising from plasma pressure variations. It is also called diamagnetic current because it produces a magnetic field which is oriented oppositely to the ambient magnetic field, causing its reduction. The magnetic reduction can be revealed in measurements made by low-Earth orbiting satellites flying close to ionospheric plasma regions where rapid changes in density occur. This type of current can be revealed at both low and high latitudes and more generally in all those regions where the plasma pressure gradients are greatest. In the recent past, most studies have focused on low latitude, in the equatorial belt, while only a few papers have focused on high latitudes. Here these currents, although weak, may pose additional challenge since they seem to appear preferentially at the same geographic locations.

Using geomagnetic field, plasma density and electron temperature measurements recorded onboard ESA Swarm constellation from April 2014 to March 2018, we reconstruct the flow patterns of the pressure-gradient current at high-latitude ionosphere in both hemispheres, and investigate their dependence on magnetic local time, geomagnetic activity, season and solar forcing drivers. Although being small in amplitude, these currents appear to be a ubiquitous phenomenon at ionospheric high latitudes, characterized by well defined flow patterns, which can cause artifacts in main field models. Our findings can be used to correct magnetic field measurements for diamagnetic current effect, to improve modern magnetic field models, as well as understanding the impact of ionospheric irregularities on ionospheric dynamics at small-scale sizes of a few tens of kilometers. All these points are important in the framework of space weather effect modeling and confirm the key role of Swarm mission in providing information even on phenomena of very weak signature.

How to cite: Lovati, G., De Michelis, P., Consolini, G., and Berrilli, F.: Pressure-Gradient current at high latitude from Swarm measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6096, https://doi.org/10.5194/egusphere-egu22-6096, 2022.

EGU22-6269 | Presentations | EMRP2.15

Dawn-dusk asymmetry of solar flare-driven ionospheric current at high latitudes 

Pierre Cavarero, Masatoshi Yamauchi, Magnar G. Johnsen, Shin-Ichi. Ohtani, and Janet Machol

Solar flares are known to enhance the ionospheric electron density and thus influence the D- and E-region electric currents in the sunlit hemisphere.  The resultant geomagnetic disturbances (called "crochet") are found at both low latitudes and high latitudes with a minimum in between.  The subsolar response, with short-lived and symmetric changes around the subsolar region, is understood as a temporal re-distribution of the electron density.  However, no systematic study has been made of the high-latitude responses, covering the auroral oval, the cusp, and the dayside sub-auroral region.  Even global patterns are not well described or understood.  

Using data from GOES satellites and SuperMAG, we made a statistical study of the high-latitude geomagnetic responses to X-class solar flares in the northern polar region.  First, we needed to create a reliable X-flare database that we could use to get precise timings of when the flares start and when they stop. We merged XRS databases from different GOES satellites to create a X-class solar flare database between 1984 and 2017, gathering 331 X-flares over 34 years.  

For all these X-flares, we plotted the geomagnetic disturbance (∆B) on a polar map during the periods when the X-ray flux exceeds 1e-4 W/m2 (>X1 flare).  Plots were made also for merged data, i.e., different events on the same map organized by geographic coordinates and local time to obtain the average disturbance pattern caused by the flares.  Large events (∆B >300 nT) were excluded to minimize the contamination from substorm events.  

In these "merged" plots, we classify the data by season (summer - 4 months, equinox ±2 months, winter 4 months), flare intensity (X1-X2 flares and >X2 flares), and maximum ∆B among all stations > 65° GGlat (< 100 nT and 100-300 nT). 

 

Except for winter, we found a large poleward ∆B which peaks at 13-16 LT, particularly for > X2 flares, but no enhancements in the pre-noon sector.  This asymmetry, surprisingly, remains even after we consider IMF By polarity.  We do not have any plausible explanation for this result, and we will discuss it during the presentation.

 

[Acknowledgement: This work is resulted from a 2021 summer internship study at the Swedish Institute of Space Physics, Kiruna.   The GOES X-ray data is provided by NOAA (USA). The geomagnetic data at high latitudes are obtained from SuperMAG and are originally provided by DTU (Denmark), TGO (Norway), FMI (Finland), SGO (Finland), SGU (Sweden), GSC (Canada), USGS (USA), AARI (Russia), PGI (Russia), IZMIRAN (Russia), BAS (UK), BGS (UK), IPGP (France), PAS (Poland), ZAMF (Austria), and ASCR (Czech)]

How to cite: Cavarero, P., Yamauchi, M., Johnsen, M. G., Ohtani, S.-I., and Machol, J.: Dawn-dusk asymmetry of solar flare-driven ionospheric current at high latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6269, https://doi.org/10.5194/egusphere-egu22-6269, 2022.

EGU22-6336 | Presentations | EMRP2.15

Swarm-derived indices of geomagnetic activity 

Constantinos Papadimitriou, Georgios Balasis, Adamantia Zoe Boutsi, Alexandra Antonopoulou, Georgia Moutsiana, Ioannis A. Daglis, Omiros Giannakis, Giuseppe Consolini, Jesper Gjerloev, and Lorenzo Trenchi

Ground-based indices, such as the Dst, ap and AE, have been used for decades to describe the interplay of the terrestrial magnetosphere with the solar wind and provide quantifiable indications of the state of geomagnetic activity in general. These indices have been traditionally derived from ground-based observations from magnetometer stations all around the Earth. In the last 7 years though, the highly successful satellite mission Swarm has provided the scientific community with an abundance of high quality magnetic measurements at Low Earth Orbit (LEO), which can be used to produce the space-based counterparts of these indices, such the Swarm-Dst, Swarm-ap and Swarm-AE indices. In this work, we present the first results from this endeavour, with comparisons against traditionally used parameters. We postulate on the possible usefulness of these Swarm-based products for a more accurate monitoring of the dynamics of the magnetosphere and thus, for providing a better diagnosis of space weather conditions.

How to cite: Papadimitriou, C., Balasis, G., Boutsi, A. Z., Antonopoulou, A., Moutsiana, G., Daglis, I. A., Giannakis, O., Consolini, G., Gjerloev, J., and Trenchi, L.: Swarm-derived indices of geomagnetic activity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6336, https://doi.org/10.5194/egusphere-egu22-6336, 2022.

EGU22-8015 | Presentations | EMRP2.15

Towards an improved proxy for geomagnetically induced currents (GICs) 

Fernando Jorge Gutiérrez Pinheiro, Marta Neres, M. Alexandra Pais, Joana Alves Ribeiro, Rute Santos, and João Cardoso

The irregular variation of geomagnetic activity caused by the solar wind interaction with the magnetosphere/ionosphere (space weather) occurs in wide temporal and amplitude ranges. Major geomagnetic storms can induce geoelectric fields in the Earth conducting layers (through the lithosphere and down to the mantle), which may, in turn, be responsible for generating geomagnetically induced currents (GICs). The vulnerability of grounded conducting infrastructures, particularly electrical power transmission systems, to GICs, makes it important to understand the relation between the varying geomagnetic field components and the generated GICs, as well as the role of the local conductivity, i.e., geology, on the inducing process. Looking for proxies that better translate this relation is an open matter of debate.

In this work, we present a comprehensive study of several possible candidates for GIC proxies. We use geomagnetic time series from the Portuguese mid-latitude Coimbra observatory (COI) to calculate geomagnetic indices considering different periods (whole-storm duration, 3-h, 1-h and 1-min), with different focuses on the field components or their derivatives, and discuss their advantages and limitations. We compare the computed indices with both GIC simulations of the Portuguese mainland high voltage power network (150, 220 and 400 kV) (Alves Ribeiro et al., 2021), and observations from a Hall effect sensor based system installed at a power transformer located in the vicinity of Coimbra. 
We then propose a better GIC proxy, an index obtained from geomagnetic field components filtered by convolution with a uniform conductivity Earth model filter (EGIC index), based on previous work by Marshall et al (2010,2011). We search for empirical parameters that may contain information on local conductivity effects and power network geometry.

This study is funded by national funds through FCT (Portuguese Foundation for Science and Technology, I.P.), under the project MAG-GIC (PTDC/CTA-GEO/31744/2017). FCT is also acknowledged for support through projects UIDB/50019/2020-IDL, PTDC/CTA-GEF/1666/2020 (MN) and PTDC/CTA-GEO/031885/2017 (MN). CITEUC is funded by FCT (UIDB/00611/2020 and UIDP/00611/2020). We acknowledge the collaboration with REN (Redes Energéticas Nacionais).

References:
Alves Ribeiro J., F.J. Pinheiro, M.A. Pais, 2021. First Estimations of Geomagnetically Induced Currents in the South of Portugal. Space Weather, 19(1)
Marshall R. A., C. L. Waters, M. D. Sciffer (2010). Spectral analysis of pipe‐to soil potentials with variations of the Earth’s magnetic field in the Australian region. Space Weather 8.5
Marshall, R. A., et al (2011). "A preliminary risk assessment of the Australian region power network to space weather." Space Weather 9.10

How to cite: Gutiérrez Pinheiro, F. J., Neres, M., Pais, M. A., Alves Ribeiro, J., Santos, R., and Cardoso, J.: Towards an improved proxy for geomagnetically induced currents (GICs), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8015, https://doi.org/10.5194/egusphere-egu22-8015, 2022.

EGU22-8752 | Presentations | EMRP2.15

A quasi-real time geomagnetic activity index from ground based measurements at geomagnetic observatories run by italian INGV for space weather nowcasting 

Paolo Bagiacchi, Lili Cafarella, Alfredo Del Corpo, Domenico Di Mauro, Stefania Lepidi, and Mauro Regi

The geomagnetic observatories managed by INGV (Istituto Nazionale di Geofisica e Vulcanologia), both in Italy and Antarctica, send data to a server and the data are collected and stored in a MySQL database. The database has been operating for almost two decades and it is implemented on a local server which serves also as a web portal for the data display and distribution. By analyzing the data of all the INGV geomagnetic observatories at middle and polar latitudes, i.e. the values of the H, D and Z components, the F module and the K indices, the algorithm aims to distinguish the activity of the Earth's magnetic field in the following categories: “Quiet Period”, “Local disturbance” and “Magnetic Activity”, possibly distinguishing, within the latter, the level and the kind of event (sudden impulse, sudden ionospheric and magnetic disturbance driven by solar flare, magnetic storm or substorm). A preliminary automatic procedure allows to detect possible instrumental failure from a comparison between the vector components and the total field intensity in each observatory. A second level of check allows to discriminate local or regional against global features with the final goal to reject local noise, possibly of anthropic nature, eventually present in a single observatory through a majority logic based procedure. After these first filtering steps an automatic software procedure provides an empirical estimation of the current  Magnetic Activity (nowcasting) organized according to the above three possible categories. The embedded algorithm in the procedure operates on the geomagnetic field element (H, D, Z and F) and the local K indices of all observatories. The operations that the algorithm performs are aimed to identify the impulsive components in the signal, which are caused by external events. The quiet field component is removed from the signal, leaving the impulsive components present in the signal almost unaltered. If in the residual field is present a significant activity (with respect to an appropriate threshold) a procedure is performed that distinguishes between an isolated impulse or a cluster of impulses, by using time windows of different sizes. The whole procedure allows us to generate two different geomagnetic activity indices, one at low and the other at high latitude. In a final step we compute a cross correlated geomagnetic index comparing processed data at low and high latitude to retrieve a large spatial scale index.

How to cite: Bagiacchi, P., Cafarella, L., Del Corpo, A., Di Mauro, D., Lepidi, S., and Regi, M.: A quasi-real time geomagnetic activity index from ground based measurements at geomagnetic observatories run by italian INGV for space weather nowcasting, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8752, https://doi.org/10.5194/egusphere-egu22-8752, 2022.

EGU22-9999 | Presentations | EMRP2.15

Long-term Trends and Occurrence Distributions of Geomagnetic Fluctuations as Revealed by 35 Years of CARISMA Observations at 5s Cadence 

Stavros Dimitrakoudis, Ian R. Mann, Andy Kale, and David K. Milling

The rate of change of the horizontal component of the geomagnetic field is a useful proxy for determining the severity of geomagnetically induced currents (GIC). While contemporary measurements for geomagnetic disturbances (GMD) are available from a number of arrays, short timescale datasets are not ideal for the characterisation of extreme events since their data sets are rarely indicative of the most extreme geomagnetic conditions. In the absence of long duration data sets, statistical methods have to be employed to assess the overall longer timescale historical power occurrence distributions, so as to extrapolate the behaviour of their high-end tail and which is required for the assessment of extreme events. Conversely, the CANOPUS array, subsequently expanded and operated as the CARISMA magnetometer array (www.carisma.ca), has been in continuous operation in Canada since 1986, first with a 5-second and then more recently with a 1-second cadence. Using that long timebase dataset we are able to evaluate the occurrence distributions of 5-second cadence measurements for over 10,000 operational days for each of several stations. Of particular significance for the expected magnitude of extreme events is an assessment of whether the disturbances follow a power law or log-normal distribution. Such indications can inform risk assessments on the potential for extremely hazardous GICs, for example in the estimation of a 1-in-100-year event. The CANOPUS/CARISMA GMD occurrence distributions, overall, appear to be well-approximated by log-normal rather than power law distributions. However, for extreme events, the local time at which the largest GMD typically occurs rotates away from the midnight sector, such that the largest events in the tail of the distribution most often occur instead at dawn. This has significant implications for assessing the size of expected extreme GMD events, and indeed the local time of the largest vulnerability, with clear applications for assessing extreme space weather impacts on the electric power grid. 

How to cite: Dimitrakoudis, S., Mann, I. R., Kale, A., and Milling, D. K.: Long-term Trends and Occurrence Distributions of Geomagnetic Fluctuations as Revealed by 35 Years of CARISMA Observations at 5s Cadence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9999, https://doi.org/10.5194/egusphere-egu22-9999, 2022.

EGU22-10681 | Presentations | EMRP2.15

Causality and information transfer in interactions of solar wind, radiation belts and geomagnetic field 

Pouya Manshour, Constantinos Papadimitriou, George Balasis, Milan Palus, Simon Wing, Ioannis A. Daglis, Reik Donner, Adamantia Zoe Boutsi, Giuseppe Consolini, Juergen Kurths, and Bruce T. Tsurutani

Understanding physical processes that drive dynamics of the radiation belts - the high-energy charged particle population trapped by the geomagnetic field in the inner magnetosphere, is of great importance for science and society. In fact, this population dynamically interacts with the solar wind and geomagnetic field over various temporal and spatial scales, and can have significant impacts on its surrounding environment, including hazards to satellites and astronaut health. Understanding the relevant acceleration mechanisms of these particles can help not only to uncover the underlying physics, but also to improve our ability to predict and to protect. Despite numerous attempts over several decades, unfolding the dynamics of interactions in such systems is still one of the challenging research areas and has not yet been achieved, due to the complex and nonlinear underlying physics of the radiation belts. However, information theory is not constrained by such limitations and has proven itself to be a powerful non-parametric approach to discover the causal interactions among different nonlinear complex systems, and can be considered complementary to physics-based approaches. In this work, we apply entropy-based causality measures such as conditional mutual information to determine the information transfer between various variables including different solar wind parameters and geomagnetic activity indices obtained from NASA’s OmniWeb service and omnidirectional electron fluxes from the MagEIS units onboard Van Allen Probe B in the outer radiation belt, ranging in energy from a few keV to several MeV. We find significant information flow from low energy electrons into high energy ones as well as from some solar wind/geomagnetic field parameters into electron fluxes of various energies. We are confident that our results provide great prospects for future targeted research on the dynamical mechanisms underlying radiation belts dynamics.

This work has benefitted from discussions within the International Space Science Institute (ISSI) Team # 455 “Complex Systems Perspectives Pertaining to the Research of the Near-Earth Electromagnetic Environment.”  P.M. and M.P. are supported by the Czech Science Foundation, Project No. GA19-16066S and by the Czech Academy of Sciences, Praemium Academiae awarded to M. Paluš.

How to cite: Manshour, P., Papadimitriou, C., Balasis, G., Palus, M., Wing, S., Daglis, I. A., Donner, R., Boutsi, A. Z., Consolini, G., Kurths, J., and Tsurutani, B. T.: Causality and information transfer in interactions of solar wind, radiation belts and geomagnetic field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10681, https://doi.org/10.5194/egusphere-egu22-10681, 2022.

EGU22-10887 | Presentations | EMRP2.15

Swarm as an EMIC Wave Monitor: Applications for Radiation Belt Modelling and Specification 

Ivan Pakhotin, Ian Mann, Louis Ozeke, Leon Olifer, and Stavros Dimitrakoudis

The outer belt electron radiation belt is highly dynamic, responding to a superposition of a variety of acceleration and loss processes imposed along the electron drift orbits to produce increases and decreases in flux on timescales from minutes, to hours, days and years. These trapped relativistic so-called ‘satellite killer’ electrons can penetrate spacecraft shielding and cause damage to internal electronics and single-event upsets. Understanding and predicting the radiation belt environment, therefore, is valuable for the understanding and mitigation of these potentially catastrophic impacts. Magnetic measurements from the constellation of Swarm satellites in low-Earth orbit (LEO) can be used to monitor the populations of electromagnetic ion cyclotron (EMIC) waves along their orbits. This is significant for radiation belt applications since these waves are believed to be potentially responsible for some fast losses of radiation from the Van Allen belts through fast scattering into the loss cone. Despite being far from the equatorial plane where most of the radiation belts are trapped, the propagation of EMIC waves along field lines allows an assessment of these wave populations from LEO, Swarm and similar satellites in LEO traversing the radiation belts four times in each approximately 90-minute orbit. Here we demonstrate how Swarm can be used to detect and characterize the EMIC wave populations, and compare the observed EMIC wave populations to simulations of two strong magnetic storms where radiation belt modeling based on radial diffusion demonstrated the likelihood of a missing fast loss process and which might be explained by EMIC wave-particle interactions. The current state-of-the-art for the incorporation of EMIC-related wave losses is based on empirical means, related for example to solar wind compressions. Here we investigate, despite the often spatio-temporally localized character of some EMIC wave populations, whether magnetic field data from the Swarm constellation could be used in an observational data-constrained approach for the inclusion of EMIC wave losses in radiation belt modelling. LEO satellites have the advantage over high-apogee near-equatorial satellites in that the latter only cross L-shells comparatively slowly; similarly, the interpretation of EMIC wave location from ground-based magnetometer networks is complicated by propagation in the ionospheric duct. Through the use of multi-spacecraft techniques, and/or those which utilise electric and magnetic data together, we demonstrate how it is possible to reliably disentangle EMIC waves from nearby field-aligned currents. Such techniques provide hitherto unprecedented observation capability for the specification of EMIC waves from LEO for use in radiation belt modelling. Future work could examine the utility of such data for both improving the accuracy of radiation belt models, and for the nowcasting and even forecasting of belt dynamics.

How to cite: Pakhotin, I., Mann, I., Ozeke, L., Olifer, L., and Dimitrakoudis, S.: Swarm as an EMIC Wave Monitor: Applications for Radiation Belt Modelling and Specification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10887, https://doi.org/10.5194/egusphere-egu22-10887, 2022.

EGU22-11323 | Presentations | EMRP2.15

Information flow within the magnetosphere-ionosphere system: insights from ensemble-based transfer entropy 

Mirko Stumpo, Giuseppe Consolini, Simone Benella, and Tommaso Alberti

When the interplanetary magnetic field is characterized by nearly-southward conditions, the near-Earth magnetospheric environment and, specifically, the plasma circulation and the magnetospheric-ionospheric current systems undergo to some dynamical changes to dissipate the excess of energy-momentum and mass transfer from interplanetary medium to the magnetosphere. Geomagnetic storms and magnetospheric substorms are the macroscopic manifestation of such a response and their relation is one of the critical issues of the magnetospheric dynamics. In this framework, a very old and widely debated topic is the storm-substorm relations, such as for instance the role of substorms in developing a storms. In recent years, some novel methods developed in the ambit of the information theory, such us the transfer entropy, have been applied to unveil the directionality of the information flow between storms and substorms (De Michelis et al., 2011, Stumpo et al, 2020). However, these results have been partially criticised suggesting that there is not a clear net transfer of information between substorms to storms. However, the use of information theory methods which relies on time averages could hide the dynamics of the information flow. Indeed, the absence of a net information exchange between storms and substorms may be due to the fact that it is enhanced only during activity periods, so that it may be canceled out if transfer entropy is computed by averaging together quiet and activity periods.Here, we attempt an instantaneous estimation of the magnetospheric internal transfer of information during the occurrence of geomagnetic storms using an ensemble-based transfer entropy analysis. In detail using some geomagnetic indices as proxies of magnetospheric-ionosphere dynamics during geomagnetic storms, we investigate the directionality of the information flow within the magnetosphere-ionosphere system during the occurrence of periods of magnetic storms and substorms.

This work received funding by Italian MIUR-PRIN grant 2017APKP7T on Circumterrestrial Environment: Impact of Sun-Earth Interaction.

How to cite: Stumpo, M., Consolini, G., Benella, S., and Alberti, T.: Information flow within the magnetosphere-ionosphere system: insights from ensemble-based transfer entropy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11323, https://doi.org/10.5194/egusphere-egu22-11323, 2022.

EGU22-11344 | Presentations | EMRP2.15

Comparing long short-term memory and convolutional neural networks in SYM-H index forecasting 

Federico Siciliano, Giuseppe Consolini, and Fabio Giannattasio

Geomagnetic indices can have a central role in the mitigation of ground effects due to space weather events, for instance when their reliable forecasting will be achieved. To this purpose, machine learning techniques represent a powerful tool. Here, we use two conceptually different neural networks to forecast the SYM-H index: the long short-term memory (LSTM) and the convolutional neural network (CNN). We build two models and train both of them using two different sets of input parameters including interplanetary magnetic field components and magnitude and differing for the presence or not of previous SYM-H values. Both models are trained, validated, and tested on a total of 42 geomagnetic storms among the most intense that occurred between 1998 and 2018. Results show that both models are able to well forecast SYM-H index 1 hour in advance. The main difference between the two stands in the better performance of the one based on LSTM when SYM-H index is included in the input parameters and, contrarily, in the better performance of the one based on CNN for predictions based only on interplanetary magnetic field data.

How to cite: Siciliano, F., Consolini, G., and Giannattasio, F.: Comparing long short-term memory and convolutional neural networks in SYM-H index forecasting, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11344, https://doi.org/10.5194/egusphere-egu22-11344, 2022.

EGU22-13154 | Presentations | EMRP2.15

Time derivative of the geomagnetic field has a short reset time 

Mirjam Kellinsalmi, Ari Viljanen, Liisa Juusola, and Sebastian Käki

Space weather, like solar eruptions, can be hazardous to Earth’s electric grids via geomagnetically induced currents (GIC). In worst cases they can even cause city-wide power outages. GIC is a complicated phenomenon, closely related to the time derivative of the geomagnetic field. However, behavior the time derivative is chaotic and has proven to be challenging to predict. In this study we look at the geomagnetic field orientations at different magnetometer stations in the Fennoscandian region during active space weather conditions.  We aim to characterize the magnetic field behavior, to better understand the drivers behind strong GIC events. One of our main findings is that the direction of time derivative of the geomagnetic field has a very short “reset time“, only a few minutes. We conclude that this result gives insight on the time scale of the ionospheric current systems, which are the primary driver behind the time derivative’s behavior.

How to cite: Kellinsalmi, M., Viljanen, A., Juusola, L., and Käki, S.: Time derivative of the geomagnetic field has a short reset time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13154, https://doi.org/10.5194/egusphere-egu22-13154, 2022.

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