EGU General Assembly 2022  

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 1R_E (0.2R_E). These HSJs then converge, leading to the formation of a large-scale HSJ with a parallel (perpendicular) scale size of 6R_E (1.2R_E). 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.

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  θ_Bn 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.

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.

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(-ρ_ek), where ρ_e 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 k^-αexp(-λk) law at sub-ion scales, with an exponential range developing around kρ_e≈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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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_o . 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 B_o 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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, f_pe, 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 (f_pe 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 f_pe intensifications.  This fraction increases with B dropout size until all dropouts are associated with f_pe 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.

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.

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

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.

Near-f_ce 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-f_ce harmonic waves are strongly connected to the magnetic field direction. We express the magnetic field direction in terms of spherical angles, where θ_B is the elevation angle and φ_B is the azimuthal angle. Then, we show that near-f_ce harmonics emissions occur when the magnetic field points in a narrow angular range, bounded by 80° ≤ θ_B ≤ 100° and 10° ≤ φ_B ≤ 30°, in most of the cases. We also show that the influence of magnetic field direction on near-f_ce 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-f_ce 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.

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.

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.

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.

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.

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.

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.

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.

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 75^o. 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 V_ISN, longitude λ_ISN, and latitude β_ISN) and temperature T_ISN of interstellar He in the local cloud, which organizes V_ISN, λ_ISN, and T_ISN as a function of λ_ISN, and the local flow Mach number (V_th−ISN/V_ISN).  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.

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.

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.

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.

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.

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.

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 24^th 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 R_e­ 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.

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.

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.

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.

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.

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.

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.

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.

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.

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, σ_c, quantifying the difference in power between the counter-propagating fluxes. We have determined σ_c at inertial range frequencies in a large sample of ICME flux ropes and sheaths observed by the Wind spacecraft at 1 au. The mean σ_c 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 σ_c tends to be larger and anti-sunward fluctuations show a greater predominance. Superposed epoch profiles show σ_c 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 σ_c 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 σ_c. Coronal and interplanetary origins of low σ_c 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.

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<U_α/V_A,p<1.5 and 0.1<β_p<10 assuming quasi-perpendicular propagation of the slow mode wave, where U_α is the background alpha particle beam speed, V_A,p is the proton Alfvén velocity, and β_p 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 U_α/V_A,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 β_p.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Medium energy electron (MEE) (30-1000 keV) precipitation enhances the production of nitric (NO_x) and hydrogen oxides (HO_x) 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 NO_x 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.

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.

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.

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.

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 n_beam 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.