Content:

ST – Solar-Terrestrial Sciences

ST1.1 – Open Session on the Sun and Heliosphere

Solar activity is an essential factor for the study of many aspects of the geophysical and astronomical sciences. A very simple measure of solar activity is counting sunspots using telescopes. This task can be done even with small telescopes since the Sun is apparently a very large and luminous star. For this reason, it is possible to rescue the ancient observations of sunspots made in the past centuries to obtain an image of the evolution of solar activity during the last four centuries.

The first attempt to reconstruct solar activity from these records was made by Rudolf Wolf, who defined the Sunspot Number index in the 19th century. The Zurich Observatory (and later the Brussels Observatory) was in charge of continuing Wolf's work to the present day. In 1998, Hoyt and Schatten presented a new reconstruction of solar activity that was very different from Wolf's reconstruction (Vaquero and Vázquez, 2009). Many of these differences were solved by Clette et al. (2014).

Currently, research to improve the Sunspot Number is focused on (i) improving the database by reviewing old observations, and (ii) improving the methodologies to convert raw data into the Sunspot Number index. In this work, we try to present the latest advances in this task (Muñoz-Jaramillo and Vaquero, 2019; Arlt and Vaquero, 2020).

 

References

Arlt, R., Vaquero, J.M. (2020) Living Reviews in Solar Physics 17, 1.

Clette, F. et al. (2014) Space Science Reviews 186, 35.

Muñoz-Jaramillo, A., Vaquero, J.M. (2019) Nature Astronomy 3, 205.

Vaquero, J.M. and Vázquez, M. (2009) The Sun recorded through history (Springer).

How to cite: Vaquero, J. M.: A long-term geophysical and astronomical dataset: sunspot counting from 1610 to 2021, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15499, https://doi.org/10.5194/egusphere-egu21-15499, 2021.

EGU21-2555 | vPICO presentations | ST1.1

A clock for the Sun's magnetic Hale cycle and 27 day recurrences in the aa geomagnetic index

Sandra Chapman, Scott McIntosh, Robert Leamon, and Nicholas Watkins

We construct a new solar cycle phase clock which maps each of the last 18 solar cycles onto a single normalized epoch for the approximately 22 year Hale (magnetic polarity) cycle, using the Hilbert transform of daily sunspot numbers (SSN) since 1818. We use the clock to study solar and geomagnetic climatology as seen in datasets available over multiple solar cycles. The occurrence of solar maxima on the clock shows almost no Hale cycle dependence, confirming that the clock is synchronized with polarity reversals.  The odd cycle minima lead the even cycle minima by ~ 1.1 normalized years, whereas the odd cycle terminators (when sunspot bands from opposite hemispheres have moved to the equator and coincide, thus terminating the cycle, McIntosh(2019)) lag the even cycle terminators  by ~ 2.3 normalized years.  The average interval between each minimum and terminator  is thus relatively extended for odd cycles and shortened for even ones. We re-engineer the R27 index that was orignally proposed by Sargent(1985) to parameterize 27 day recurrences in the aa index. We perform an epoch analysis of autocovariance in the aa index using the Hale cycle clock to obtain a high time resolution parameter for 27 day recurrence, <acv(27)>. This reveals that the transition to recurrence, that is, to an ordered solar wind dominated by high speed streams, is fast, occurring within 2-3 solar rotations or less. It resolves an extended late declining phase which is approximately twice as long on even Schwabe cycles as odd ones. We find that Galactic Cosmic Ray flux rises in step with <acv(27)> but then stays high. Our analysis also identifies a slow timescale trend in SSN that simply tracks the Gleissberg cycle. We find that this trend is in phase with the slow timescale trend in the modulus of sunspot latitudes, and in antiphase with that of the R27 index.

How to cite: Chapman, S., McIntosh, S., Leamon, R., and Watkins, N.: A clock for the Sun's magnetic Hale cycle and 27 day recurrences in the aa geomagnetic index, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2555, https://doi.org/10.5194/egusphere-egu21-2555, 2021.

EGU21-14168 | vPICO presentations | ST1.1

 First radio evidence for ubiquitous magnetic reconnections and impulsive heating in the quiet solar corona 

Surajit Mondal, Divya Oberoi, Ayan Biswas, Shabbir Bawaji, Ujjaini Alam, Arpit Behera, Devojyoti Kansabanik, Nick Swainston, Ramesh Bhat, and John Morgan

It has been a long standing problem as to how the solar corona can maintain its million K temperature, while the photosphere, which is the lowest layer of the solar atmosphere, is only at a temperature of 5800 K. A very promising theory to explain this is the “nanoflare” hypothesis, which suggests that numerous flares of energies ~1024 ergs are always happening in the solar corona, and maintain its million K temperature. However, detecting these nanoflares directly is challenging with the current instrumentation as they are hypothesised to occur at very small spatial, temporal and energy scales. These nanoflares are expected to produce nonthermal electrons, which are expected to emit in the radio band. These nonthermal emissions are often brighter than their thermal counterparts and might be detectable with current radio instruments. Due to their importance multiple searches for these nonthermal emissions have been done, but thus far they have been  limited to active regions. The quiet corona is also hot, and often comprises the bulk of the coronal region, so it is equally important to understand the physical processes which maintain this medium at MK temperatures. We describe the results from our effort to use the data from the Murchison Widefield Array (MWA) to search for impulsive radio emissions in the quiet solar corona. By pushing the detection threshold of nonthermal emission by about two orders of magnitude lower than previous studies, we have uncovered ubiquitous very impulsive nonthermal emissions from the quiet sun. We refer to these emissions as Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs). Using independent observations spanning very different solar conditions we show that WINQSEs are present throughout the quiet corona at all times. Their occurrence rate lies in the range of many hundreds to about a thousand per minute, implying that on average order 10 or so WINQSEs are present in every 0.5 s MWA image. Preliminary estimates suggest that WINQSEs have a bandwidth of ~2 MHz. Buoyed by  their possible connection to the hypothesised “nanoflares”, we are pursuing several projects to characterise and understand them. These include developing machine learning algorithms to identify WINQSEs in radio images and characterise their morphologies; exploring the ability of the present generation EUV and X-ray instruments to estimate the energy corresponding to the brightest of WINQSEs; and attempting very high time resolution imaging to explore their temporal structure. In this talk, I will present the results from the past and ongoing projects about WINQSEs and argue that these might be a key step towards detecting “nanoflares” and the resolution of the coronal heating problem.

 

 

How to cite: Mondal, S., Oberoi, D., Biswas, A., Bawaji, S., Alam, U., Behera, A., Kansabanik, D., Swainston, N., Bhat, R., and Morgan, J.:  First radio evidence for ubiquitous magnetic reconnections and impulsive heating in the quiet solar corona , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14168, https://doi.org/10.5194/egusphere-egu21-14168, 2021.

EGU21-14293 | vPICO presentations | ST1.1

Radio and X-ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare   

Rohit Sharma, Marina Battaglia, Yingjie Luo, Bin Chen, and Sijie Yu

Solar flares release enormous magnetic energy into the corona, producing the heating of ambient plasma and acceleration of particles. The flaring process is complex and often shows multiple spatially separated temporal individual episodes of energy releases, which can be hard to resolve based on the instrument capability. We analysed the multi-wavelength imaging and spectroscopy observations of multiple electron acceleration episodes during a GOES B1.7-class two-ribbon flare observed simultaneously with the Karl G. Jansky Very Large Array (VLA) at 1--2 GHz, the Reuven Ramatay High Energy Solar Spectroscopic Imager (RHESSI) in X-rays, and the Solar Dynamics Observatory in extreme ultraviolet (EUV).
We observed a total of six radio bursts. First three bursts were co-temporal, but not co-spatial nonthermal X-ray source and represent multiple electron acceleration episodes. We model the radio spectra by optically thick gyrosynchrotron emission and estimate the magnetic field strength and nonthermal electron spectral parameters in each acceleration episode. We note that the nonthermal parameters derived from X-rays differ considerably from the nonthermal parameters inferred from the radio and originates in the lower corona. Although co-temporal, our multi-wavelength analysis shows that different electron populations produce multiple acceleration episodes in radio and X-rays wavelengths. 

How to cite: Sharma, R., Battaglia, M., Luo, Y., Chen, B., and Yu, S.: Radio and X-ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare   , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14293, https://doi.org/10.5194/egusphere-egu21-14293, 2021.

EGU21-4954 | vPICO presentations | ST1.1

Surges of the weak magnetic field in the photosphere of the Sun

Dmitrii Baranov, Elena Vernova, and Marta Tyasto

The properties of the magnetic fields of the solar photosphere are investigated, in particular, the distribution of fields of different polarity over the solar surface. As primary data, synoptic maps of the photospheric magnetic field of the Kitt Peak National Solar Observatory for 1978-2016 were used. Using the vector summation method, the non-axisymmetric component of the magnetic field is determined. It was found that the nonaxisymmetric component of weak magnetic fields B < 5 G changes in antiphase with the flux of these fields. Magnetic fields of B < 5 G constitute a significant part of the total magnetic field of the Sun, since they occupy more than 60% of the area of the photosphere. The fine structure of the distribution of weak fields can  be observed by setting the upper limit to the strength of the  fields  included in the time–latitude diagram. This allows to eliminate the contribution of the strong fields of sunspots.

On the time-latitude diagram for weak magnetic fields (B < 5 G), bands of differing colors correspond to the streams of the magnetic fields moving in the direction to the Sun’s poles.. These streams or surges show the alternation of the dominant polarity - positive or negative - which is clearly seen in all four cycles. The slopes of the bands indicate the velocity of the fields movement towards the poles. The surges can be divided into two groups. The surges of the first group belong to the so-called Rush-to-the-Poles. These are bands with the width of about three years, which begin at approximately 40° of latitude and have the same polarity as the trailing sunspots. They reach high latitudes and cause the polarity reversal of the polar field. However, in addition to these surges, for most of the solar  cycle (the descending phase, the minimum and the ascending phase), there are narrower surges of both polarities (with the width less than one year), which extend from the equator almost to the poles. These surges are most clearly visible in the southern hemisphere when the southern pole is positive. Consideration of the latitude-time diagrams separately for positive and negative polarities showed that the alternating dominance of one of the polarities is associated with the antiphase development  of the positive and negative fields of the surges. The widths of surges and the periodicity of their appearance vary significantly for the two hemispheres and from one solar cycle to the other. The mean period of the polarity alternation is about 1.5 years.

How to cite: Baranov, D., Vernova, E., and Tyasto, M.: Surges of the weak magnetic field in the photosphere of the Sun, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4954, https://doi.org/10.5194/egusphere-egu21-4954, 2021.

EGU21-2445 | vPICO presentations | ST1.1

Prominence Formation by Levitation-Condensation at Extreme Resolutions

Jack Jenkins and Rony Keppens

We revisit the so-called levitation-condensation mechanism for the ab-inito formation of solar prominences: cool and dense clouds in the million-degree solar atmosphere. Levitation-condensation occurs following the formation of a flux rope in response to the deformation of a force-free coronal arcade by controlled magnetic footpoint motions and subsequent reconnection. Existing coronal plasma gets lifted within the forming rope, therein isolating a collection of matter now more dense than its immediate surroundings. This denser region ultimately suffers a thermal instability driven by radiative losses, and a prominence forms. We improve on various aspects that were left unanswered in the early work, by revisiting this model with our modern open-source grid- adaptive simulation code [amrvac.org]. Most notably, this tool enables a resolution of 5.6 km within a 24 Mm x 25 Mm domain size; the full global flux rope dynamics and local plasma dynamics are captured in unprecedented detail. Our 2.5D simulation (where the flux rope has realistic helical magnetic field lines) demonstrates that the thermal runaway condensation can happen at any location, not solely in the bottom part of the flux rope where the majority of prominence material is assumed to reside. Intricate thermodynamic evolution and shearing flows develop spontaneously, themselves inducing further fine-scale (magneto)hydrodynamic instabilities. Our analysis touches base with advanced linear magnetohydrodynamic stability theory, e.g. with the Convective Continuum Instability or CCI process as well as with in-situ thermal instability studies. We find that condensing prominence plasma evolves according to the internal pressure and density gradients as found previously for coronal rain condensations, but also misalignments therein suggesting the relevance of the Rayleigh-Taylor instability or RTI process in 3D. We also find evidence for resistively-driven dynamics in the prominence body, in close analogy with analytical predictions. These findings are relevant for modern studies of full 3D prominence formation and structuring. Most notably, we anticipate obtaining similar resolutions within a fully 3D setup. Such an achievement will afford us the exciting opportunity to offer crucial explanations as to the persistent discrepancy in prominence appearance when projected off- or on-disk.

How to cite: Jenkins, J. and Keppens, R.: Prominence Formation by Levitation-Condensation at Extreme Resolutions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2445, https://doi.org/10.5194/egusphere-egu21-2445, 2021.

EGU21-3616 | vPICO presentations | ST1.1

Direct Observation of A Large-scale CME Flux Rope Event Arising from an Unwinding Coronal Jet 

Hechao Chen, Jiayan Yang, Junchao Hong, Haidong Li, and Yadan Duan

Increasing observations show that coronal jets may result in bubble-shaped coronal mass ejections (CMEs), but the genesis of jet-driven CMEs and their nature are not fully understood. Here, we report a direct stereoscopic observation on the magnetic coupling from a coronal blowout jet to a stellar-sized CME.  Observations in the EUV passbands of SDO/AIA show that this whole event starts with a small-scale active-region filament whose eruption occurs at a coronal geyser site due to flux emergence and cancellation. By interacting with an overlying null-point configuration, this erupting filament first breaks one of its legs and triggers an unwinding blowout jet. The release of magnetic twist in its jet spire is estimated at around 1.5−2.0 turns. This prominent twist transport in jet spire rapidly creates a newborn large-scale flux rope from the jet base to a remote site. As a result, the newborn large-scale flux rope erupts into the outer coronae causing an Earth-directed bubble-shaped CME. In particular, two sets of distinct flare post-flare loops form in its source region in sequence, indicating this eruptive event couples with twice flare reconnection. This observation highlights a real pathway for jet-CME magnetic coupling and provides a new hint for the buildup of large-scale CME flux ropes. 

How to cite: Chen, H., Yang, J., Hong, J., Li, H., and Duan, Y.: Direct Observation of A Large-scale CME Flux Rope Event Arising from an Unwinding Coronal Jet , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3616, https://doi.org/10.5194/egusphere-egu21-3616, 2021.

EGU21-1461 | vPICO presentations | ST1.1

Characteristics of Sunquake Events Observed in Solar Cycle 24

Alexander Kosovichev and Ivan Sharykin

Helioseismic response to solar flares ("sunquakes") occurs due to localized force or/and momentum impacts observed during the flare impulsive phase in the lower atmosphere. Such impacts may be caused by precipitation of high-energy particles, downward shocks, or magnetic Lorentz force. Understanding the mechanism of sunquakes is a key problem of the flare energy release and transport. Our statistical analysis of M-X class flares observed by the Solar Dynamics Observatory during Solar Cycle 24 has shown that contrary to expectations, many relatively weak M-class flares produced strong sunquakes, while for some powerful X-class flares, helioseismic waves were not observed or were weak. The analysis also revealed that there were active regions characterized by the most efficient generation of sunquakes during the solar cycle. We found that the sunquake power correlates with maximal values of the X-ray flux derivative better than with the X-ray class. The sunquake data challenge the current theories of solar flares.

How to cite: Kosovichev, A. and Sharykin, I.: Characteristics of Sunquake Events Observed in Solar Cycle 24, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1461, https://doi.org/10.5194/egusphere-egu21-1461, 2021.

EGU21-13091 | vPICO presentations | ST1.1

Coronal loops in a box: 3D models of their internal structure, dynamics and heating

Cosima Breu, Hardi Peter, Robert Cameron, Sami Solanki, Pradeep Chitta, and Damien Przybylski

The corona of the Sun, and probably also of other stars, is built up by loops defined through the magnetic field. They vividly appear in solar observations in the extreme UV and X-rays. High-resolution observations show individual strands with diameters down to a few 100 km, and so far it remains open what defines these strands, in particular their width, and where the energy to heat them is generated.

The aim of our study is to understand how the magnetic field couples the different layers of the solar atmosphere, how the energy generated by magnetoconvection is transported into the upper atmosphere and dissipated, and how this process determines the scales of observed bright strands in the loop.

To this end, we conduct 3D resistive MHD simulations with the MURaM code. We include the effects of heat conduction, radiative transfer and optically thin radiative losses.
We study an isolated coronal loop that is rooted with both footpoints in a shallow convection zone layer. To properly resolve the internal structure of the loop while limiting the size of the computational box, the coronal loop is modelled as a straightened magnetic flux tube. By including part of the convection zone, we drive the evolution of the corona self-consistently by magnetoconvection.

We find that the energy injected into the loop is generated by internal coherent motions within strong magnetic elements. 
The resulting Poynting flux is channelled into the loop in vortex tubes forming a magnetic connection between the photosphere and corona, where it is dissipated and heats the upper atmosphere.

The coronal emission as it would be observed in solar extreme UV or X-ray observations, e.g. with AIA or XRT, shows transient bright strands.
The widths of these strands are consistent with observations. From our model we find that the width of the strands is governed by the size of the individual photospheric magnetic field concentrations where the field lines through these strands are rooted. Essentially, each coronal strand is mainly rooted in a single magnetic patch in the photosphere, and the energy to heat the strand is generated by internal motions within this magnetic concentration.

With this model we can build a coherent picture of how energy and matter are transported into the upper solar atmosphere and how these processes structure the interior of coronal loops.

How to cite: Breu, C., Peter, H., Cameron, R., Solanki, S., Chitta, P., and Przybylski, D.: Coronal loops in a box: 3D models of their internal structure, dynamics and heating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13091, https://doi.org/10.5194/egusphere-egu21-13091, 2021.

EGU21-1013 | vPICO presentations | ST1.1

Formation of solar coronal loops through magnetic reconnection in an emerging active region

Zhenyong Hou, Hui Tian, Hechao Chen, Xiaoshuai Zhu, Jiansen He, Xianyong Bai, Zhenghua Huang, and Lidong Xia

Coronal loops are building blocks of solar active regions (ARs). However, their formation is not well understood. Here we present direct observational evidence for the formation of coronal loops through magnetic reconnection as new magnetic fluxes emerge to the solar atmosphere. Observations in the EUV passbands of SDO/AIA clearly show the newly formed loops following magnetic reconnection within a vertical current sheet. Formation of the loops is also seen in the Hα images taken by NVST. The SDO/HMI observations show that a positive-polarity flux concentration moves toward a negative-polarity one with a speed of ~0.5 km s-1 before the apparent formation of coronal loops. During the formation of coronal loops, we found signatures of flux cancellation and subsequent enhancement of the transverse field between the two polarities. We have reconstructed the three-dimensional magnetic field structure through a magnetohydrostatic model, which shows field lines consistent with the loops in AIA images. Numerous bright blobs with a width of ~1.5 Mm appear intermittently in the current sheet and move upward with apparent velocities of ~80 km s-1. We have also identified plasma blobs moving to the footpoints of the newly formed large loops, with apparent velocities ranging from 30 to 50 km s-1. A differential emission measure analysis shows that the temperature, emission measure and density of the bright blobs are 2.5-3.5 MK, 1.1-2.3×1028 cm-5 and 8.9-12.9×109 cm-3, respectively. Power spectral analysis of these blobs indicates that the magnetic reconnection is inconsistent with the turbulent reconnection scenario.

How to cite: Hou, Z., Tian, H., Chen, H., Zhu, X., He, J., Bai, X., Huang, Z., and Xia, L.: Formation of solar coronal loops through magnetic reconnection in an emerging active region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1013, https://doi.org/10.5194/egusphere-egu21-1013, 2021.

EGU21-3134 | vPICO presentations | ST1.1

Coronal dimmings associated with coronal mass ejections on the solar limb

Galina Chikunova, Karin Dissauer, Tatiana Podladchikova, and Astrid Veronig

We studied 43 coronal dimming events associated with Earth-directed coronal mass ejections (CMEs) that were observed in quasi-quadrature by the SDO and STEREO satellites. We derived the properties of the dimmings as observed above the limb by STEREO EUVI, and compared them with the mass and speed of the associated CMEs. The unique satellite constellation allowed us to compare our findings with the results from Dissauer et al. (2018, 2019), who studied these events observed against the solar disk by SDO AIA. Such statistics is done for the first time and confirms the close relation between characteristic dimming and CME parameters for the off-limb viewpoint. We find that the dimming areas are typically larger for off-limb observations (mean value of 1.24±1.23×1011 km2 against 3.51±0.71×1010 km2 for on-disk), while the decrease in the total extreme ultraviolet intensity is similar (c=0.60±0.14). The off-limb dimming areas and brightnesses are strongly correlated with the CME mass (c=0.82±0.06 and 0.75±0.08), whereas the dimming area and brightness change rate correlate with the CME speed (c∼0.6). Our findings suggest that coronal dimmings have the potential to provide early estimates of the Earth-directed CMEs parameters, relevant for space weather forecasts, for satellite locations at both L1 and L5.

How to cite: Chikunova, G., Dissauer, K., Podladchikova, T., and Veronig, A.: Coronal dimmings associated with coronal mass ejections on the solar limb, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3134, https://doi.org/10.5194/egusphere-egu21-3134, 2021.

EGU21-31 | vPICO presentations | ST1.1

The Source Locations of Major Flares and CMEs in the Emerging Active Regions

Lijuan Liu, Yuming Wang, Zhenjuan Zhou, and Jun Cui

Major flares and coronal mass ejections (CMEs) tend to originate from the compact polarity inversion lines (PILs) in the solar active regions (ARs). Recently, a scenario named as “collisional shearing” is proposed by Chintzoglou et al. (2019) to explain the phenomenon, which suggests that the collision between different emerging bipoles is able to form the compact PIL, driving the shearing and flux cancellation that are responsible to the subsequent large activities. In this work, through tracking the evolution of 19 emerging ARs from their birth until they produce the first major flares or CMEs, we investigated the source PILs of the activities, i.e., the active PILs, to explore the generality of “collisional shearing”. We find that none of the active PILs is the self PIL (sPIL) of a single bipole. We further find that 11 eruptions originate from the collisional PILs (cPILs) formed due to the collision between different bipoles, 6 from the conjoined systems of sPIL and cPIL, and 2 from the conjoined systems of sPIL and ePIL (external  PIL between the AR and the nearby preexisting polarities). Collision accompanied by shearing and flux cancellation is found developing at all PILs prior to the eruptions, with 84% (16/19) cases having collisional length longer than 18 Mm. Moreover, we find that the magnitude of the flares is positively correlated with the collisional length of the active PILs, indicating that the intenser activities tend to originate from the PILs with severer collision. The results suggest that the “collisional shearing”, i.e., bipole-bipole interaction during the flux emergence is a common process in driving the major activities in emerging ARs.

How to cite: Liu, L., Wang, Y., Zhou, Z., and Cui, J.: The Source Locations of Major Flares and CMEs in the Emerging Active Regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-31, https://doi.org/10.5194/egusphere-egu21-31, 2021.

We present a novel method to derive the shock density compression ratio of coronal shock waves that are occasionally observed as halo coronal mass ejections (CMEs). Our method uses the three-dimensional (3-D) geometry and enables us to access the reliable shock density compression ratio. We show the 3-D properties of coronal shock waves seen from multiple vantage point observations, i.e., geometry, kinematics, and compression ratio (Mach number). The significant findings are as follows: (1) Halo CMEs are the manifestation of spherically shaped fast-mode waves/shocks, rather than a matter of the projection of expanding flux ropes. The footprints of halo CMEs on the coronal base are the so-called EIT/EUV waves. (2) These spherical fronts arise from a driven shock (bow- or piston-type) close to the CME nose, and it is gradually becoming a freely propagating (decaying) fast-mode shock wave at the flank. (3) The shock density compressions peak around the CME nose and decrease at larger position angles (flank). (4) Finally, the supercritical region extends over a large area of the shock and lasts longer than past reports.  These results offer a simple unified picture of the different manifestations for CME-associated (shock) waves, such as EUV waves and SEP events observed in various regimes and heliocentric distances. We conclude that CME shocks can accelerate energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere.

How to cite: Kwon, R. Y.: The three-dimensional density compression ratio of shock fronts observed as halo coronal mass ejections , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10578, https://doi.org/10.5194/egusphere-egu21-10578, 2021.

EGU21-642 | vPICO presentations | ST1.1

Mapping the global magnetic field in the solar corona through magnetoseismology

Zihao Yang, Christian Bethge, Hui Tian, Steven Tomczyk, Richard Morton, Giulio Del Zanna, Scott McIntosh, Bidya Binay Karak, Sarah Gibson, Tanmoy Samanta, Jiansen He, Yajie Chen, Linghua Wang, and Xianyong Bai

Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

How to cite: Yang, Z., Bethge, C., Tian, H., Tomczyk, S., Morton, R., Del Zanna, G., McIntosh, S., Binay Karak, B., Gibson, S., Samanta, T., He, J., Chen, Y., Wang, L., and Bai, X.: Mapping the global magnetic field in the solar corona through magnetoseismology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-642, https://doi.org/10.5194/egusphere-egu21-642, 2021.

EGU21-3990 | vPICO presentations | ST1.1

Clustering of Fast Coronal Mass Ejections during Solar Cycles 23 and 24 and Implications for CME–CME Interactions

Jenny Marcela Rodriguez Gomez, Tatiana Podlachikova, Astrid Veronig, Alexander Ruzmaikin, Joan Feynman, and Anatoly Petrukovich

Coronal Mass Ejections (CMEs) and their interplanetary counterparts (ICMEs) are the major sources for strong space weather disturbances. We present a study of statistical properties of fast CMEs (v≥1000 km/s) that occurred during solar cycles 23 and 24. We apply the Max Spectrum and the declustering threshold time methods. The Max Spectrum can detect the predominant clusters, and the declustering threshold time method provides details on the typical clustering properties and timescales. Our analysis shows that during the different phases of solar cycles 23 and 24, fast CMEs preferentially occur as isolated events and in clusters with, on average, two members. However, clusters with more members appear, particularly during the maximum phases of the solar cycles. During different solar cycle phases, the typical declustering timescales of fast CMEs are τc =28-32 hrs, irrespective of the very different occurrence frequencies of CMEs during a solar minimum and maximum. These findings suggest that  τc   for extreme events may reflect the characteristic energy build-up time for large flare and CME-prolific active regions. Statistically associating the clustering properties of fast CMEs with the disturbance storm time index at Earth suggests that fast CMEs occurring in clusters tend to produce larger geomagnetic storms than isolated fast CMEs. Our results highlight the importance of CME-CME interaction and their impact on Space Weather.

How to cite: Rodriguez Gomez, J. M., Podlachikova, T., Veronig, A., Ruzmaikin, A., Feynman, J., and Petrukovich, A.: Clustering of Fast Coronal Mass Ejections during Solar Cycles 23 and 24 and Implications for CME–CME Interactions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3990, https://doi.org/10.5194/egusphere-egu21-3990, 2021.

EGU21-7602 | vPICO presentations | ST1.1

LOFAR observations of a jet-driven piston shock in the low solar corona

Ciara Maguire, Eoin Carley, Pietro Zucca, Nicole Vilmer, and Peter Gallagher

The Sun produces highly dynamic and eruptive events that can drive shocks through the corona. These shocks can accelerate electrons, which result in plasma emission in the form of a type II radio burst. Despite a large number of type II radio bursts observations, the precise origin of coronal shocks is still subject to investigation. Here we present a well-observed solar eruptive event that occurred on 16 October 2015, focusing on a jet observed in the extreme ultraviolet by the SDO Atmospheric Imaging Assembly, a streamer observed in white-light by the Large Angle and  Spectrometric Coronagraph, and a metric type II radio burst observed by the LOw-Frequency Array (LOFAR) radio telescope. For the first time, LOFAR has interferometrically imaged the fundamental and harmonic sources of a type II radio burst and revealed that the sources did not appear to be co-spatial, as would be expected from the plasma emission mechanism. We correct for the separation between the fundamental and harmonic using a model which accounts for the scattering of radio waves by electron density fluctuations in a turbulent plasma. This allows us to show the type II radio sources were located ∼0.5 Rsun above the jet and propagated at a speed of ∼1000 km s−1, which was significantly faster than the jet speed of ∼200 km s−1. This suggests that the type II burst was generated by a piston shock driven by the jet in the low corona.

How to cite: Maguire, C., Carley, E., Zucca, P., Vilmer, N., and Gallagher, P.: LOFAR observations of a jet-driven piston shock in the low solar corona, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7602, https://doi.org/10.5194/egusphere-egu21-7602, 2021.

EGU21-11089 | vPICO presentations | ST1.1

High fidelity spectroscopic imaging at low radio frequencies to estimate plasma parameters of solar coronal mass ejections at higher coronal heights

Devojyoti Kansabanik, Surajit Mondal, Divya Oberoi, and Angelos Vourlidas

Coronal Mass Ejections (CMEs) are large-scale explosive eruptions of magnetised plasma from the Sun into the Heliosphere. Measuring the physical parameters of CMEs is crucial for understanding their physics and for assessing their geo-effectiveness. Radio observations offer the most direct means for estimating these plasma parameters when gyrosynchrotron (GS) emission is detected from the CME plasma. However, since the first detection by Bastian et al.2001, only a handful of studies have successfully detected GS emission from CME plasma. This is usually attributed to the challenges involved in obtaining the high dynamic range imaging required for observing this faint gyrosynchrotron emission in the vicinity of active solar emissions.

The newly developed imaging pipeline (Mondal et al., 2019) designed for the data from Murchison Widefield Array (MWA) marks a significant improvement in metrewave solar radio imaging. Our work suggests that we should now be able to routinely detect GS emission from CME plasma. We present an example where we have successfully detected radio emission from CME plasma and modelled it as GS emission, leading to reliable estimates of CME magnetic field as well as the distribution of energetic electrons (Mondal et al. 2020). In a different example we are able to detect the radio emission from the CME plasma out to as far as 8.3 solar radii. We find that the observed spectra are not always consistent with simple GS models. This highlights that more complicated physics might be at play and points to the need for building more detailed models for interpreting these emissions. We hope that with the availability of polarimetric imaging capability, which we are in the process of developing, this technique will provide a robust way to routinely measure CME magnetic fields along with its other physical parameters. We note that these are the weakest detections of GS emissions from CME plasma reported yet.

How to cite: Kansabanik, D., Mondal, S., Oberoi, D., and Vourlidas, A.: High fidelity spectroscopic imaging at low radio frequencies to estimate plasma parameters of solar coronal mass ejections at higher coronal heights, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11089, https://doi.org/10.5194/egusphere-egu21-11089, 2021.

EGU21-13004 | vPICO presentations | ST1.1

Detailed Calibration of the Off-Axis Optical Characteristics for the X-Ray Telescope onboard Hinode

Junho Shin, Ryouhei Kano, Takashi Sakurai, Yeon-Han Kim, and Yong-Jae Moon

The X-Ray Telescope (XRT) onboard the Hinode satellite has a specially designed Wolter type grazing-incidence (GI) optics with a paraboloid-hyperboloid mirror assembly to measure the solar coronal plasma of temperatures up to 10 MK with a resolution of about one arc sec. One of the main purposes of this scientific mission is to investigate the detailed mechanism of energy transfer processes from the photosphere to the upper coronal region leading to its heating and the solar wind acceleration. An astronomical telescope is in general designed such that the best-focused image of an object is achieved at or very close to the optical axis, and inevitably the optical performance deteriorates away from the on-axis position. The Sun is, however, a large astronomical object and thus targets near the limb of full-disk images are placed at the outskirt of the field of view. The design of a solar telescope should thus consider the uniformity of imaging quality over a wide FOV, and it is particularly so for X-ray telescopes whose targets can be in the corona high above the limb.

 

We will explain in this presentation the importance of detailed calibration of the off-axis optical characteristics for Hinode/XRT. It have been revealed that the scattered light caused by the GI mirror surface has a power-law distribution and shows an energy dependence. We will also introduce the basic scheme of how the level of scattering wing is determined and connected to the core from the analysis of highly saturated in-flight data. Vignetting is another important optical characteristics for describing the telescope's performance, which reflects the ability to collect incoming light at different locations and photon energies. We have evaluated the vignetting effect in Hinode/XRT by analyzing the ground experimental data and found that the degree of vignetting varies linearly from the optical center and its pattern shows an energy dependence. Many interesting results on the calibration of Hinode/XRT optical characteristics will be introduced and discussed thoroughly. 

How to cite: Shin, J., Kano, R., Sakurai, T., Kim, Y.-H., and Moon, Y.-J.: Detailed Calibration of the Off-Axis Optical Characteristics for the X-Ray Telescope onboard Hinode, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13004, https://doi.org/10.5194/egusphere-egu21-13004, 2021.

EGU21-6760 | vPICO presentations | ST1.1

Two classes of eruptive events during Solar Minimum

Prantika Bhowmik and Anthony Yeates

During Solar Minimum, the Sun is perceived to be quite inactive with barely any spots emerging on the solar surface. Consequently, we observe a drop in the number of highly energetic events such as solar flares and coronal mass ejections (CMEs), which are often associated with active regions on the photosphere. However, our magnetofrictional simulations during the minimum period suggest that the solar corona could still be significantly dynamic while evolving in response to the large-scale shearing velocities on the solar surface. The non-potential evolution of the corona leads to the accumulation of magnetic free energy and helicity, which is periodically lost through eruptive events. Our study shows that these events can be categorised into two distinct classes. One set of events are caused due to full-scale eruption of low-lying coronal flux ropes and could be associated with occasional filament erupting CMEs observed during Solar Minimum. The other set of events are not driven by destabilisation of low-lying structures but rather by eruption from overlying sheared arcades. These could be linked with streamer blowouts or stealth CMEs. The two classes differ considerably in the amount of magnetic flux and helicity shed through the outer coronal boundary. We additionally investigate how other measurables such as current, open magnetic flux, free energy, coronal holes area, and the horizontal component of the magnetic field on the outer model boundary vary during the two classes of event. This study demonstrates and emphasises the importance and necessity of understanding the dynamics of the coronal magnetic field during Solar Minimum.

How to cite: Bhowmik, P. and Yeates, A.: Two classes of eruptive events during Solar Minimum, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6760, https://doi.org/10.5194/egusphere-egu21-6760, 2021.

EGU21-2076 | vPICO presentations | ST1.1

Extreme event theory applied to the solar wind

Carlos Larrodera, Lidia Nikitina, and Consuelo Cid

Society’s dependence on technology has increased during the past years. Therefore, understanding the hazardous events including space weather events that lead to technological problems is now critical. As solar wind is the driver of space weather, identifying extreme solar wind is important. In this work extreme value theory is used to characterize the solar wind parameters most relevant to space weather: interplanetary magnetic field strength and proton speed. This is done using an extreme value distribution for all data above a certain threshold for each parameter. Analysis demonstrates that these thresholds are around 900 km/s for the proton speed and around 95 nT for the interplanetary magnetic field. Based on 20 years of solar wind data, we made an estimation for the interplanetary magnetic field and solar wind proton speed with return periods corresponding to 4 and 6 solar cycles with a 99% confidence interval.

How to cite: Larrodera, C., Nikitina, L., and Cid, C.: Extreme event theory applied to the solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2076, https://doi.org/10.5194/egusphere-egu21-2076, 2021.

EGU21-14653 | vPICO presentations | ST1.1

Probing the solar corona magnetic field with sungrazing comets

Giuseppe Nisticò, Valery M. Nakariakov, Timothy Duckenfield, Miloslav Druckmüller, and Gaetano Zimbardo

Space telescopes of the SoHO, STEREO and SDO missions have occasionally acquired observations of comets, providing an interesting opportunity to investigate the structure and dynamics of the heliospheric plasma.  Cometary plasma tails exhibit a wave-like motion, which is believed to be a response to the physical conditions of the local interplanetary medium. Furthermore, sungrazing comets diving in the solar atmosphere provide us with an unprecedented way to diagnose the coronal plasma at distances which are unaccessible from the current spacecraft. Here, we present observations of Comet Lovejoy C/2011 W3 from SDO/AIA, which was seen to cross the EUV solar corona in December 2011. The cometary ions produced by the sublimation of the comet nucleus were channelled along the magnetic field lines forming some filamented structures. Such structures appear to show small amplitude kink oscillations, which are used to determine the magnitude of the coronal magnetic field by coronal seismology.

How to cite: Nisticò, G., Nakariakov, V. M., Duckenfield, T., Druckmüller, M., and Zimbardo, G.: Probing the solar corona magnetic field with sungrazing comets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14653, https://doi.org/10.5194/egusphere-egu21-14653, 2021.

EGU21-11094 | vPICO presentations | ST1.1

LOFAR Imaging of the Solar Corona during the 2015 March 20 Solar Eclipse

Aoife Maria Ryan, Peter T. Gallagher, Eoin P. Carley, Michiel A. Brentjens, Pearse C. Murphy, Christian Vocks, Diana E. Morosan, Hamish Reid, Jasmina Magdalenic, Frank Breitling, Pietro Zucca, Richard Fallows, Gottfried Mann, Alain Kerdraon, and Ronald Halfwerk

The solar corona is a highly-structured plasma which can reach temperatures of more than 2 MK. At low frequencies (decimetric and metric wavelengths), scattering and refraction of electromagnetic waves are thought to considerably increase the imaged radio source sizes (up to a few arcminutes). However, exactly how source size relates to scattering due to turbulence is still subject to investigation. The theoretical predictions relating source broadening to propagation effects have not been fully confirmed by observations, due to the rarity of high spatial resolution observations of the solar corona at low frequencies. Here, the LOw Frequency ARray (LOFAR) was used to observe the solar corona at 120–180 MHz using baselines of up to 3.5 km (corresponding to a resolution of 1–2’) during the partial solar eclipse of 2015 March 20. A lunar de-occultation technique was used to achieve higher spatial resolution (0.6’) than that attainable via standard interferometric imaging (2.4’). This provides a means of studying the contribution of scattering to apparent source size broadening. This study shows that the de-occultation technique can reveal a more structured quiet corona that is not resolved from standard imaging, implying scattering may be overestimated in this region when using standard imaging techniques. However, an active region source was measured to be 4’ using both de-occultation and standard imaging. This may be explained by increased scattering of radio waves by turbulent density fluctuations in active regions, which is more severe than in the quiet Sun.



How to cite: Ryan, A. M., Gallagher, P. T., Carley, E. P., Brentjens, M. A., Murphy, P. C., Vocks, C., Morosan, D. E., Reid, H., Magdalenic, J., Breitling, F., Zucca, P., Fallows, R., Mann, G., Kerdraon, A., and Halfwerk, R.: LOFAR Imaging of the Solar Corona during the 2015 March 20 Solar Eclipse, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11094, https://doi.org/10.5194/egusphere-egu21-11094, 2021.

EGU21-4795 | vPICO presentations | ST1.1

Quality assessment for objective inter-comparison of coronal models

Andreas Wagner, Manuela Temmer, and Eleanna Asvestari

With the increasing amount of space weather forecasting simulation codes being developed, assessing their performance becomes crucial. Especially the errors resulting from coronal magnetic field models are a critical factor, because these will get propagated further by various solar wind models. We present a first result for a benchmarking system that allows a rather easy-to-implement  assessment of the performance quality of any coronal magnetic field model. This will allow for a standardized comparison between different models. The benchmarking system is based on stepwise visual and semi-automatized comparisons between model output and EUV on-disk and coronograph white-light data. We are using various viewpoints and instrumental data provided by STEREO, SOHO and SDO. 
In our work we exemplarily apply this scheme to the coronal model currently implemented in EUHFORIA, an adaption of the Wang-Sheeley-Arge (WSA) model, with varying input parameters. Furthermore, with this system we also show its possible usage for the derivation of an ideal parameter set. 

How to cite: Wagner, A., Temmer, M., and Asvestari, E.: Quality assessment for objective inter-comparison of coronal models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4795, https://doi.org/10.5194/egusphere-egu21-4795, 2021.

EGU21-2864 | vPICO presentations | ST1.1

Study of alpha particle properties across rarefaction regions

Tereza Durovcova, Jana Šafránková, and Zdeněk Němeček

Two large-scale interaction regions between the fast solar wind emanating from coronal holes and the slow solar wind coming from streamer belt are usually distinguished. When the fast stream pushes up against the slow solar wind ahead of it, a compressed interaction region that co-rotates with the Sun (CIR) is created. It was already shown that the relative abundance of alpha particles, which usually serve as one of solar wind source identifiers can change within this region. By symmetry, when the fast stream outruns the slow stream, a corotating rarefaction region (CRR) is formed. CRRs are characterized by a monotonic decrease of the solar wind speed, and they are associated with the regions of small longitudinal extent on the Sun. In our study, we use near-Earth measurements complemented by observations at different heliocentric distances, and focus on the behavior of alpha particles in the CRRs because we found that the large variations of the relative helium abundance (AHe) can also be observed there. Unlike in the CIRs, these variations are usually not connected with the solar wind speed and alpha-proton relative drift changes. We thus apply a superposed-epoch analysis of identified CRRs with a motivation to determine the global profile of alpha particle parameters through these regions. Next, we concentrate on the cases with largest AHe variations and investigate whether they can be associated with the changes of the solar wind source region or whether there is a relation between the AHe variations and the non-thermal features in the proton velocity distribution functions like the temperature anisotropy and/or presence of the proton beam.

How to cite: Durovcova, T., Šafránková, J., and Němeček, Z.: Study of alpha particle properties across rarefaction regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2864, https://doi.org/10.5194/egusphere-egu21-2864, 2021.

EGU21-12772 | vPICO presentations | ST1.1

3He rich periods measured by the Suprathermal Ion Telescope (SIT) on STEREO-A during solar cycle 24

Marlon Köberle, Radoslav Bucik, Nina Dresing, Bernd Heber, Andreas Klassen, and Linghua Wang

3He-rich solar energetic particle (SEP) events are characterized by a peculiar elemental composition with rare species like 3He or ultra-heavy ions tremendously enhanced over the solar system abundances.
We report on 3He rich SEP periods measured by the Suprathermal Ion Telescope (SIT) onboard STEREO-A beginning in 2007 until 2020, covering the whole solar cycle 24.
The mass resolution capabilities of SIT do not allow to easily distinguish between 3He and 4He especially in cases of a low 3He to 4He ratio.
We therefore developed a semi-automatic detection algorithm to find time periods during which a 3He enhancement can be statistically determined.
Using this method we found 112 3He rich periods.
These periods were further examined in regards of their 3He/4He and Fe/O ratio. 
Previously about ten 3He-rich SEP periods measured by SIT on STEREO-A have been reported.
An association with in-situ electron measurements by STEREO-SEPT and STEREO-STE showed that ~60% of the 112 periods are accompanied with electron events.
The here presented catalogue of 3He rich periods is intended to serve as a reference for the community.

How to cite: Köberle, M., Bucik, R., Dresing, N., Heber, B., Klassen, A., and Wang, L.: 3He rich periods measured by the Suprathermal Ion Telescope (SIT) on STEREO-A during solar cycle 24, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12772, https://doi.org/10.5194/egusphere-egu21-12772, 2021.

EGU21-11921 | vPICO presentations | ST1.1

Evolution of solar wind flows from the inner corona to 1 AU: constraints provided by SOHO UVCS and SWAN data

Alessandro Bemporad, Olga Katushkina, Vladislav Izmodenov, Dimitra Koutroumpa, and Eric Quemerais

The Sun modulates with the solar wind flow the shape of the whole Heliosphere interacting with the surrounding interstellar medium. Recent results from IBEX and INCA experiments, as well as recent measurements from Voyager 1 and 2, demonstrated that this interaction is much more complex and subject to temporal and heliolatitudinal variations than previously thought. These variations could be also related with the evolution of solar wind during its journey through the Heliosphere. Hence, understanding how the solar wind evolves from its acceleration region in the inner corona to the Heliospheric boundaries is very important.

In this work, SWAN Lyman-α full-sky observations from SOHO are combined for the very first time with measurements acquired in the inner corona by SOHO UVCS and LASCO instruments, to trace the solar wind expansion from the Sun to 1 AU. The solar wind mass flux in the inner corona was derived over one full solar rotation period in 1997, based on LASCO polarized brightness measurements, and on the Doppler dimming technique applied to UVCS Lyman-α emission from neutral H coronal atoms due to resonant scattering of chromospheric radiation. On the other hand, the SWAN Lyman-α emission (due to back-scattering from neutral H atoms in the interstellar medium) was analyzed based on numerical models of the interstellar hydrogen distribution in the heliosphere and the radiation transfer. The SWAN full-sky Lyman-α intensity maps are used for solving of the inverse problem and deriving of the solar wind mass flux at 1 AU from the Sun as a function of heliolatitude. First results from this comparison for a chosen time period in 1997 are described here, and possible future applications for Solar Orbiter data are discussed.

How to cite: Bemporad, A., Katushkina, O., Izmodenov, V., Koutroumpa, D., and Quemerais, E.: Evolution of solar wind flows from the inner corona to 1 AU: constraints provided by SOHO UVCS and SWAN data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11921, https://doi.org/10.5194/egusphere-egu21-11921, 2021.

We study the 27-day variations of galactic cosmic rays (GCRs) based on neutron monitor (NM), ACE/CRIS, STEREO and SOHO/EPHIN measurements, in solar minima 23/24 and 24/25 characterized by the opposite polarities of solar magnetic cycle. Now there is an opportunity to re-analyze the polarity dependence of the amplitudes of the recurrent GCR variations in 2007-2009 for negative A < 0 solar magnetic polarity and to compare it with the clear periodic variations related to solar rotation in 2017-2019 for positive A > 0. We use the Fourier analysis method to study the periodicity in the GCR fluxes. Since the GCR recurrence is a consequence of solar rotation, we analyze not only GCR fluxes, but also solar and heliospheric parameters examining the relationships between the 27-day GCR variations and heliospheric, as well as, solar wind parameters. We find that the polarity dependence of the amplitudes of the 27-day variations of the GCR intensity and anisotropy for NMs data is kept for the last two solar minima: 23/24 (2007-2009) and 24/25 (2017-2019) with greater amplitudes in positive A > 0 solar magnetic polarity. ACE/CRIS, SOHO/EPHIN and STEREO measurements are not governed by this principle of greater amplitudes in positive A > 0 polarity. GCR recurrence caused by the solar rotation for low energy (< 1GeV) cosmic rays is more sensitive to the enhanced diffusion effects, resulting in the same level of the 27-day amplitudes for positive and negative polarities. While high energy (> 1GeV) cosmic rays registered by NMs, are more sensitive to the large-scale drift effect leading to the 22-year Hale cycle in the 27-day GCR variation, with the larger amplitudes in the A > 0 polarity than in the A < 0.

How to cite: Modzelewska, R. and Gil, A.: 27-day variations of the galactic cosmic rays intensity and anisotropy in solar minima 23/24 and 24/25 by ACE/CRIS, STEREO, SOHO/EPHIN and neutron monitors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13185, https://doi.org/10.5194/egusphere-egu21-13185, 2021.

EGU21-13829 | vPICO presentations | ST1.1

Statistical analysis of flow direction and its variations in different types of solar wind streams

Anastasiia Moskaleva, Maria Riazantseva, Yuri Yermolaev, and Irina Lodkina

The efficiency of the solar wind interaction with the Earth's magnetosphere is determined not only by the values of solar wind parameters, but also by the direction of its flow.  As a rule, the slow quiet and uniform solar wind extends radially, but at the same time there are different large-scale solar wind streams, that differ in the values of the plasma parameters and in the flow direction. The most significant changes of solar wind flow direction can be observed in areas of stream interaction, for example Sheath (compression regions before the fast interplanetary coronal mass ejections) and CIR (corotating interaction regions, that are predate high-speed flows from coronal holes) [1]. In the present study, using plasma measurements on the WIND spacecraft, the statistical distributions of the values and fluctuations of flow direction angles in the solar wind were analyzed.  The angles variations were considered on temporal scales from several ten seconds to an hour. The statistical distributions in the quiet solar wind and in various large-scale solar wind streams using the catalog of large-scale solar wind phenomena from the ftp://ftp.iki.rssi.ru/pub/omni/catalog were compared [2].

At the result of this work, it was shown , that maximum values of modules longitude (φ) and latitude (θ) angles, and of their variations are observed for Sheath and CIR regions, the probability of large deviations from the radial direction (>5 degrees)  also increases. Meanwhile the dependence on the solar wind type reduces with decreasing scale. The relation of the values and fluctuations of the direction angles on the values of the plasma parameters in the solar wind were also analyzed.

The work was supported by the RFBR, grant № 19-02-00177а.

1.Yermolaev Y. I., Lodkina I. G., Nikolaeva N. S., Yermolaev M. Y. 2017, Solar Physics, 292 (12),193, https://doi.org/10.1007/s11207-017-1205-1
2. Yermolaev, Yu.I., Nikolaeva, N.S., Lodkina, I.G., Yermolaev, M.Yu.: 2009, Catalog of large-scale solar wind phenomena during 1976 – 2000. Cosm. Res. 47(2),81;Eng.transl.Kosm.Issled.47(2),99, https://doi.org/10.1134/S0010952509020014

How to cite: Moskaleva, A., Riazantseva, M., Yermolaev, Y., and Lodkina, I.: Statistical analysis of flow direction and its variations in different types of solar wind streams, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13829, https://doi.org/10.5194/egusphere-egu21-13829, 2021.

EGU21-14937 | vPICO presentations | ST1.1

Sampling the heliosphere through low-frequency observations of pulsars

Caterina Tiburzi, Golam Shaifullah, and Pietro Zucca

Pulsars are highly-magnetized, fast-rotating neutron stars whose radiation is mainly detected at radio frequencies. Their clock-like emission and high degree of linear polarization make them ideal background sources to probe the electron density and magnetic field of the interplanetary medium.
The Soltrack project is a cutting-edge experiment that combines high-quality pulsar observations carried out with LOFAR with the study of the heliosphere and its phenomena. It recently confirmed the first evidence of the Solar cycle's impact on pulsar data, developed a new software to detect pulsar occultations by coronal mass ejections, identified the influence of Solar streamers on pulsar observations and applied pulsar-derived measurements to the validation efforts of the EUHFORIA magneto-hydrodynamic software, that simulate the Solar wind properties for Space weather purposes.
Here I will describe the fundamental concepts at the basis of the Soltrack experiments, and describe the results reached while paving the road for the application of pulsar data to heliospheric analyses.

How to cite: Tiburzi, C., Shaifullah, G., and Zucca, P.: Sampling the heliosphere through low-frequency observations of pulsars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14937, https://doi.org/10.5194/egusphere-egu21-14937, 2021.

The Nancay Radioheliograph is dedicated to imaging the solar corona at decimetre-to-metre wavelengths. The imaged structures are the quiet corona, through thermal bremsstrahlung, and bright collective emissions due to electrons accelerated in quiescent, flaring and eruptive active regions. The instrument produced nearly daily maps of the Sun between 1996 and 2015, at several frequencies in the 150-450 MHz range with sub-second cadence. The observations were stopped in 2015 for a major technical upgrade through the replacement of the correlator and the data acquisition system. They were resumed in November 2020, and at the time of writing the commissioning of the instrument is well underway. This contribution will give a brief overview of the technical changes and present observations at eight frequencies of solar activity since November 2020, including the coronal mass ejection (CME) of December 14 seen in some images of the total solar eclipse, observations conducted during the present perihelion passage of the Parker Solar Probe mission, as well as during periods of interest to the Solar Orbiter mission. The data are freely available, and special products of common visualisation with the space missions will be illustrated.

How to cite: Klein, K.-L. and the NRH team: Solar observations with the Nancay Radioheliograph in support of the Solar Orbiter and Parker Solar Probe missions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7107, https://doi.org/10.5194/egusphere-egu21-7107, 2021.

TianQin is a proposed space-borne gravitational wave (GW) observatory composed of three identical satellites orbiting around the geocenter with a distance of 105 km. It aims at detecting GWs in 0.1 mHz – 1 Hz. The detection of GW relies on the high precision measurement of optical path length at 10−12 m level. The dispersion of space plasma can lead to the optical path difference (OPD, ∆l) along the propagation of laser beams between a pair of satellites. Here, we study the OPD noises for TianQin. The Space Weather Modeling Framework is used to simulate the interaction between the Earth magnetosphere and solar wind. From the simulations, we extract the magnetic field and plasma parameters on the orbits of TianQin at four relative positions of the satellite constellation in the Earth magnetosphere. We calculate the OPD noise for single link, Michelson, and Time-Delay Interferometry (TDI) data combinations (α and X). For single link and Michelson interferometer, the maxima of ∆l are on the order of 1 pm. For the TDI combinations, these can be suppressed to about 0.05 pm. The OPD noise of Michelson combination is colored in the concerned frequency range; while the ones for the TDI combinations are roughly white. Furthermore, we calculate the ratio of the equivalent strain of the OPD noise to that of TQ, and find that the OPD noises for the TDI combinations can be neglected in the most sensitive frequency range of f < 0.1 Hz.

How to cite: Wei, S.: Analyses of Laser Propagation Noise for TianQin Gravitational Wave Observatory Based on the Global Magnetosphere MHD Simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10868, https://doi.org/10.5194/egusphere-egu21-10868, 2021.

Understanding and modelling the complex state of the Sun-solar wind-heliosphere system, requires a comprehensive set of multiwavelength observations. LOFAR has unique capabilities in the radio domain. Some examples of these include: a) the ability to take high-resolution solar dynamic spectra and radio images of the Sun; b) observing the scintillation (interplanetary scintillation - IPS) of distant, compact, astronomical radio sources to determine the density, velocity and turbulence structure of the solar wind; and c) the use of Faraday rotation as a tool to probe the interplanetary magnetic-field strength and direction. However, to better understand and predict how the Sun, its atmosphere, and more in general the Heliosphere works and impacts Earth, the combination of in-situ spacecraft measurements and ground-based remote-sensing observations of coronal and heliospheric plasma parameters is extremely useful. Ground-based observations can be used to infer a global picture of the inner heliosphere, providing the essential context into which in-situ measurements from spacecraft can be placed. Conversely, remote-sensing observations usually contain information from extended lines of sight, with some deconvolution and modelling necessary to build up a three-dimensional (3-D) picture. Precise spacecraft measurements, when calibrated, can provide ground truth to constrain these models. The PSP mission is observing the solar corona and near-Sun interplanetary space. It has a highly-elliptical orbit taking the spacecraft as close as nearly 36 sola radii from the Sun centre on its first perihelion passage, and subsequent passages ultimately reaching as close as 9.8 solar radii. Four instruments are on the spacecraft’s payload: FIELDS measuring the radio emission, electric and magnetic fields, Poynting flux, and plasma waves as well as the electron density and temperature; ISOIS measuring energetic electrons, protons, and heavy ions in the energy range 10 keV-100 MeV; SWEAP measuring the density, temperature, and flow speed of electrons, protons, and alphas in the solar wind; and finally, WISPR imaging coronal streamers, coronal mass ejections (CMEs), their associated shocks, and other solar wind structures in the corona and near-Sun interplanetary space, and provide context for the other three in-situ instruments. In this talk, the different observing modes of LOFAR and several results of the joint LOFAR/PSP campaign will be presented, including fine structures of radio bursts, localization and kinematics of propagating radio sources in the heliosphere, and the challenges and plans for future observing campaigns including PSP and Solar Orbiter.

 

How to cite: Zucca, P.: Observing the Sun with LOFAR: an overview of the telescope capabilities and the recent results from the PSP groud base support campaign., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15048, https://doi.org/10.5194/egusphere-egu21-15048, 2021.

EGU21-9506 | vPICO presentations | ST1.1

Response of the interplanetary hydrogen population to global changes of solar activity: a quantitative analysis based on SOHO/SWAN and SOHO/LASCO-C2 data comparison.

Dimitra Koutroumpa, Eric Quémerais, Lucile Conan, Philippe Lamy, Stéphane Ferron, and Hugo Gilardy

For more than two decades the SOHO/SWAN instrument has been monitoring the full-sky hydrogen backscattered Lyman-α emission, and the derived three-dimensional solar wind proton flux. We present a comparison of the time series of the latitude-integrated hydrogen ionization rates (β) derived from the inversion of the SWAN full-sky maps with the integrated coronal electron density derived from the inversion of SOHO/LASCO-C2 white light images. The analysis shows a variable time lag of the SWAN β of a few Carrington rotations, correlated with the solar cycle phase (larger delay during solar maxima compared to minima). This is a direct consequence of the variation of the size of the hydrogen ionization cavity and the time it takes for hydrogen atoms to propagate in the inner heliosphere. This effect should be taken into account in studies of the interstellar neutral populations in interplanetary space.

How to cite: Koutroumpa, D., Quémerais, E., Conan, L., Lamy, P., Ferron, S., and Gilardy, H.: Response of the interplanetary hydrogen population to global changes of solar activity: a quantitative analysis based on SOHO/SWAN and SOHO/LASCO-C2 data comparison., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9506, https://doi.org/10.5194/egusphere-egu21-9506, 2021.

EGU21-14279 | vPICO presentations | ST1.1

Shock Acceleration of ~1-100 Kev Electrons at Earth's Bow Shock

Zixuan Liu, Linghua Wang, Liu Yang, Wimmer-Schweingruber Robert, Quanqi Shi, and Bale Stuart

We present a statistical study of in-situ shock acceleration of ~1-100 keV solar wind suprathermal electrons at Earth’s bow shock, by using Wind 3D plasma and energetic particle measurements in ambient solar wind and MMS measurements in shock downstream. We pick out 74 shock cases (1 quasi-parallel shock, 73 quasi-perpendicular shocks) during 2015 October - 2017 January, and classify them into 4 types according to their energy spectra in downstream: type 0 (23 cases) without significant electron acceleration after shock passage, type 1 (24 cases) with power-law spectrum, J ∝εβ1_dn, at ~0.8-10 keV, type 2 (16 cases) with power-law-spectrum at ~0.8-10 keV and significant flux enhancement above 30 keV, and type 3 (11 cases) with a clear double-power-law spectrum, J ∝ εβ1_dn (J ∝ εβ2_dn) when ε « εdntr  (ε » εdntr), bending down at εdntr ~20-90 keV. The spectral indexes at lower energies for type 1, type 2 and type 3, β1dn, range from 2.5 to 5, while the spectral indexes at higher energies for type 3, β2dn, range from 4 to 9, and all the spectral indexes have no significant correlation with those in ambient solar wind. Among the 4 types, type 3 is the strongest acceleration with the largest flux enhancement and the lowest β1dn. Besides, we find that the flux ratio between downstream and ambient solar wind Jdn/Jab is field-perpendicular for most cases in both low and high energies, and Jdn/Jab1dn) has positive (negative) correlations with θBn and magnetic field compression ratio, rB, which favor the shock drift acceleration (SDA) mechanism. However, Jdn/Jab has no correlation with the drift electric field Ed, while the normalized drift time, Td/Ttr, has a positive correlation with θBn, it suggests that θBn can influence electron drift time and thus influence the acceleration efficiency.

How to cite: Liu, Z., Wang, L., Yang, L., Robert, W.-S., Shi, Q., and Stuart, B.: Shock Acceleration of ~1-100 Kev Electrons at Earth's Bow Shock, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14279, https://doi.org/10.5194/egusphere-egu21-14279, 2021.

EGU21-10504 | vPICO presentations | ST1.1

Unique heliophysics science opportunities along the Interstellar Probe journey up to 1000 AU from the Sun

Elena Provornikova, Pontus C. Brandt, Ralph L. McNutt, Jr., Robert DeMajistre, Edmond C. Roelof, Parisa Mostafavi, Drew Turner, Matthew E. Hill, Jeffrey L. Linsky, Seth Redfield, Andre Galli, Carey Lisse, Kathleen Mandt, Abigail Rymer, and Kirby Runyon

The Interstellar Probe is a space mission to discover physical interactions shaping globally the boundary of our Sun`s heliosphere and its dynamics and for the first time directly sample the properties of the local interstellar medium (LISM). Interstellar Probe will go through the boundary of the heliosphere to the LISM enabling for the first time to explore the boundary with a dedicated instrumentation, to take the image of the global heliosphere by looking back and explore in-situ the unknown LISM. The pragmatic concept study of such mission with a lifetime 50 years that can be implemented by 2030 was funded by NASA and has been led by the Johns Hopkins University Applied Physics Laboratory (APL). The study brought together a diverse community of more than 400 scientists and engineers spanning a wide range of science disciplines across the world.

Compelling science questions for the Interstellar Probe mission have been with us for many decades. Recent discoveries from a number of space missions exploring the heliosphere raised new questions strengthening the science case. The very shape of the heliosphere, a manifestation of complex global interactions between the solar wind and the LISM, remains the biggest mystery. Interpretations of imaging the heliosphere in energetic neutral atoms (ENAs) in different energy ranges on IBEX and Cassini/INCA from inside show contradictory pictures. Global physics-based models also do not agree on the global shape. Interstellar Probe on outbound trajectory will image the heliosphere from outside for the first time and will provide a unique determination of the global shape.

The LISM is a completely new area for exploration and discovery. We have a crude understanding of the LISM inferred from in-situ measurements inside the heliosphere of interstellar helium, pick-up-ions, ENAs, remote observations of solar backscattered Lyman-alpha emission and absorption line spectroscopy in the lines of sight of stars. We have no in-situ measurements of most LISM properties, e.g. ionization, plasma and neutral gas, magnetic field, composition, dust, and scales of possible inhomogeneities. Voyagers with limited capabilities have explored 30 AU beyond the heliosphere which appeared to be a region of significant heliospheric influence. The LISM properties are among the key unknowns to understand the Sun`s galactic neighborhood and how it shapes our heliosphere. Interstellar Probe will be the first NASA mission to discover the very nature of the LISM and shed light on whether the Sun enters a new region in the LISM in the near future.

In this presentation we give an overview of heliophysics science for the Interstellar Probe mission focusing on the critical science questions of the three objectives for the mission. We will discuss in more details a need for direct measurements in the LISM uniquely enabled by the Interstellar Probe.

How to cite: Provornikova, E., Brandt, P. C., McNutt, Jr., R. L., DeMajistre, R., Roelof, E. C., Mostafavi, P., Turner, D., Hill, M. E., Linsky, J. L., Redfield, S., Galli, A., Lisse, C., Mandt, K., Rymer, A., and Runyon, K.: Unique heliophysics science opportunities along the Interstellar Probe journey up to 1000 AU from the Sun, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10504, https://doi.org/10.5194/egusphere-egu21-10504, 2021.

EGU21-3308 | vPICO presentations | ST1.1

Interstellar Probe: A Mission to the Heliospheric Boundary and Interstellar Medium for the Next Decade

Pontus Brandt, Ralph McNutt, Elena Provornikova, Carey Lisse, Kathleen Mandt, Kirby Runyon, Abigail Rymer, Parisa Mostafavi, Robert DeMajistre, Edmond Roelof, Drew Turner, Matthew Hill, James Kinnison, Gabe Rogers, Clayton Smith, Glen Fountain, David Copeland, Peter Kollmann, Reza Ashtari, and Robert Stough and the The Interstellar Probe Study Team

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 unexplored Local Interstellar Clouds that our Sun is moving through in relatively short galactic timescales. As such, it would represent Humanity's first explicit step in to the galaxy and become perhaps NASA's boldest step in space exploration. Such a mission has been discussed and studied since 1960, but the stumbling block has often been propulsion. Now this hurdle has been overcome by the availability of new and larger launch vehicles. An international team of scientists and experts are now progressing towards the final year of 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. Together with the Space Launch System (SLS) Office at the NASA Marshall Space Flight Center, the team has analyzed dozens of launch configurations and demonstrate 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 and update 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., McNutt, R., Provornikova, E., Lisse, C., Mandt, K., Runyon, K., Rymer, A., Mostafavi, P., DeMajistre, R., Roelof, E., Turner, D., Hill, M., Kinnison, J., Rogers, G., Smith, C., Fountain, G., Copeland, D., Kollmann, P., Ashtari, R., and Stough, R. and the The Interstellar Probe Study Team: Interstellar Probe: A Mission to the Heliospheric Boundary and Interstellar Medium for the Next Decade, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3308, https://doi.org/10.5194/egusphere-egu21-3308, 2021.

ST1.2 – Energetic Particles in the Heliosphere and their influence on the Atmosphere

EGU21-6212 | vPICO presentations | ST1.2

Cosmic rays at ground level; a brief introduction

Du Toit Strauss

Galactic cosmic rays, and sporadic high energy solar energetic particles, are energetic enough to pierce the Earth’s protective magnetosphere and interact with the atmosphere. Here, a secondary particle cascade leads to enhanced radiation levels which is of importance, for instance, to aviation dosimetry and related studies. At ground level, these secondary particles can be observed (indirectly) by means of neutron monitors, and this has been done for more than 70 years, providing a valuable long-term cosmic ray record. In this talk, we introduce the different primary particle populations, discuss their acceleration and modulation, and connect this with long-term neutron monitor measurements.

How to cite: Strauss, D. T.: Cosmic rays at ground level; a brief introduction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6212, https://doi.org/10.5194/egusphere-egu21-6212, 2021.

EGU21-6394 | vPICO presentations | ST1.2

Energetic particles and the solar cycle: Impact of solar magnetic field amplitude and geometry on SEPs and GCRs diffusion coefficients

Barbara Perri, Allan Sacha Brun, Antoine Strugarek, and Victor Réville

SEPs are correlated with the 11-year solar cycle due to their production by flares and interaction with the inner heliosphere, while GCRs are anti-correlated with it due to the modulation of the heliospheric magnetic field. The solar magnetic field along the cycle varies in amplitude but also in geometry, causing diffusion of the particles along and across the field lines; the solar wind distribution also evolves, and its turbulence affects particle trajectories.

We combine 3D MHD compressible numerical simulations to compute the configuration of the magnetic field and the associated polytropic solar wind up to 1 AU, with analytical prescriptions of the corresponding parallel and perpendicular diffusion coefficients for SEPs and GCRs. First, we analyze separately the impact of the magnetic field amplitude and geometry for a 100 MeV proton. By varying the amplitude, we change the amplitude of the diffusion by the same factor, and the radial gradients by changing the spread of the current sheet. By varying the geometry, we change the latitudinal gradients of diffusion by changing the position of the current sheets. We also vary the energy, and show that the statistical distribution of parallel diffusion is different for SEPs and GCRs. Then, we use realistic solar configurations, showing that diffusion is highly non-axisymmetric due to the configuration of the current sheets, and that the distribution varies a lot with the distance to the Sun, especially at minimum of activity. With this model, we are thus able to study the direct influence of the Sun on Earth spatial environment in terms of energetic particles. 

How to cite: Perri, B., Brun, A. S., Strugarek, A., and Réville, V.: Energetic particles and the solar cycle: Impact of solar magnetic field amplitude and geometry on SEPs and GCRs diffusion coefficients, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6394, https://doi.org/10.5194/egusphere-egu21-6394, 2021.

EGU21-3719 | vPICO presentations | ST1.2

Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles

David Ruffolo, Rohit Chhiber, William H. Matthaeus, Arcadi V. Usmanov, Paisan Tooprakai, Piyanate Chuychai, and Melvyn L. Goldstein

The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles (SEPs) propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. We develop a formalism in which the differential equation describing the field line random walk contains both effects due to localized magnetic displacements and a non-stochastic contribution from the large-scale expansion. We use this formalism together with a global magnetohydrodynamic simulation of the inner-heliospheric solar wind, which includes a turbulence transport model, to estimate the diffusive spreading of magnetic field lines that originate in different regions of the solar atmosphere. We first use this model to quantify field line spreading at 1 au, starting from a localized solar source region, and find rms angular spreads of about 20 – 60 degrees. In the second instance, we use the model to estimate the size of the source regions from which field lines observed at 1 au may have originated, thus quantifying the uncertainty in calculations of magnetic connectivity; the angular uncertainty is estimated to be about 20 degrees. Finally, we estimate the filamentation distance, i.e., the heliocentric distance up to which field lines originating in magnetic islands can remain strongly trapped in filamentary structures. We emphasize the key role of slab-like fluctuations in the transition from filamentary to more diffusive transport at greater heliocentric distances. This research has been supported in part by grant RTA6280002 from Thailand Science Research and Innovation and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165).  MLG acknowledges support from the Parker Solar Probe FIELDS MAG team.  Additional support is acknowledged from the  NASA LWS program  (NNX17AB79G) and the HSR program (80NSSC18K1210 & 80NSSC18K1648).

How to cite: Ruffolo, D., Chhiber, R., Matthaeus, W. H., Usmanov, A. V., Tooprakai, P., Chuychai, P., and Goldstein, M. L.: Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3719, https://doi.org/10.5194/egusphere-egu21-3719, 2021.

EGU21-134 | vPICO presentations | ST1.2

The Unusual Widespread Solar Energetic Particle Event on 2013 August 19: Solar origin, CME-driven shock evolution and particle longitudinal distribution

Laura Rodríguez-García, Raúl Gómez-Herrero, Yannis Zouganelis, Laura Balmaceda, Teresa Nieves-Chinchilla, Nina Dresing, Mateja Dumbovic, Nariaki Nitta, Fernando Carcaboso, Luiz Fernando Guedes dos Santos, Lan Jian, Leila Mays, David Williams, and Javier Rodríguez-Pacheco

Context: Late on 2013 August 19, STEREO-A, STEREO-B, MESSENGER, Mars Odyssey, and L1 spacecraft, spanning a longitudinal range of 222° in the ecliptic plane, observed an energetic particle flux increase. The widespread solar energetic particle (SEP) event was associated with a coronal mass ejection (CME) that came from a region located near the far-side central meridian from Earth's perspective. The CME appeared to consist of two eruptions, and was accompanied by a ~M3 flare as a post-eruption arcade, and low-frequency (interplanetary) type II and shock-accelerated type III radio bursts.

Aims: The main objectives of this study are two, disentangling the reasons of the different intensity-time profiles observed by MESSENGER and STEREO-A, longitudinally separated by only 15°, and unravelling the single solar source related with the SEP event.

Results: The solar source associated with the widespread SEP event is the shock driven by the two-stages CME, as the flare observed as a posteruptive arcade is too late to explain the estimated particle onset. The different intensity-time profiles observed by STEREO-A, located at 0.97 au, and MESSENGER, at 0.33 au, can be interpreted as enhanced particle scattering beyond Mercury's orbit. The longitudinal extent of the shock does not explain by itself the wide spread of particles in the heliosphere. The particle increase observed at L1 may be attributed to cross-field diffusion transport, and this is also the case for STEREO-B, at least until the spacecraft is eventually magnetically connected to the shock at ~0.6 au. The CME-driven shock may have suffered distortion in its evolution in the heliosphere, such that the shock flank overtakes the shock nose at 1 au.

How to cite: Rodríguez-García, L., Gómez-Herrero, R., Zouganelis, Y., Balmaceda, L., Nieves-Chinchilla, T., Dresing, N., Dumbovic, M., Nitta, N., Carcaboso, F., dos Santos, L. F. G., Jian, L., Mays, L., Williams, D., and Rodríguez-Pacheco, J.: The Unusual Widespread Solar Energetic Particle Event on 2013 August 19: Solar origin, CME-driven shock evolution and particle longitudinal distribution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-134, https://doi.org/10.5194/egusphere-egu21-134, 2021.

The influence of the heliospheric current sheet (HCS) on the propagation of high energy solar protons is explored using 3D test particle modelling. The test particle model, which includes drift effects, is used to simulate specific past ground level enhancement (GLE) events which cover a range of HCS configurations. For example, the effects of a source location close to and far from the HCS for events both poorly and well-connected to Earth are examined. Similarly, the effect of the Earth’s location relative to the HCS is explored. The modelling is performed for high energy (300-1200 MeV) protons to represent the energetic conditions under which GLEs occur. The derived intensity profiles at 1AU are compared to observations from HEPAD onboard GOES, as well as STEREO (at locations away from Earth) and neutron monitor data. 

How to cite: Waterfall, C. and Dalla, S.: Role of the heliospheric current sheet in high energy proton transport through modelling of historic GLE events , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6223, https://doi.org/10.5194/egusphere-egu21-6223, 2021.

EGU21-8189 | vPICO presentations | ST1.2

A self-consistent simulation of proton acceleration and transport near a high-speed solar wind stream

Nicolas Wijsen, Evangelia Samara, Àngels Aran, David Lario, Jens Pomoell, and Stefaan Poedts

Solar wind stream interaction regions (SIRs)  are often characterised by energetic ion enhancements. The mechanisms accelerating these particles as well as the locations where the acceleration occurs, remains debated. Here, we report the findings of a simulation of a SIR-event observed by Parker Solar Probe at 0.56 au and the Solar Terrestrial Relations Observatory-Ahead at 0.96 au in September 2019 when both spacecraft were approximately radially aligned with the Sun. The simulation reproduces the solar wind configuration and the energetic particle enhancements observed by both spacecraft. Our results show that the energetic particles are produced at the compression waves associated with the SIR and that the suprathermal tail of the solar wind is a good candidate to provide the seed population for particle acceleration. The simulation confirms that the acceleration process does not require shock waves and can already commence within Earth's orbit, with an energy dependence on the precise location where particles are accelerated. The three-dimensional configuration  of the solar wind streams strongly modulates the energetic particle distributions, illustrating the necessity of advanced models to understand  these particle events.

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., Samara, E., Aran, À., Lario, D., Pomoell, J., and Poedts, S.: A self-consistent simulation of proton acceleration and transport near a high-speed solar wind stream, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8189, https://doi.org/10.5194/egusphere-egu21-8189, 2021.

EGU21-10734 | vPICO presentations | ST1.2

Solar Energetic Electron Events Associated with Hard X-ray Flares 

Wen Wang, Linghua Wang, Sam Krucker, Glenn M. Mason, Yang Su, and Radoslav Bucik

We investigate 16 solar energetic electron (SEE) events measured by WIND/3DP with a double power-law spectrum and the associated western hard X-ray (HXR) flares measured by RHESSI with good count statistics, from 2002 February to 2016 December. In all 16 cases, the presence of an SEE power-law spectrum extending down to 65 keV at 1 AU implies that the SEE source would be high in the corona, at a heliocentric distance of >1.3 solar radii, while the footpoint or footpoint-like emissions shown in HXR images suggest that the observed HXRs are likely produced mainly by thick target bremsstrahlung processes very low in the corona. We find that in 8 cases (the other 8 cases), the power-law spectral index of HXR-producing electrons, estimated under the relativistic thick-target bremsstrahlung model, is significantly larger than (similar to) the observed high-energy spectral index of SEEs, with a positive correlation. In addition, the estimated number of SEEs is only 10-4 - 10-2 of the estimated number of HXRproducing electrons at energies above 30 keV, but also with a positive correlation. These results suggest that in these cases, SEEs are likely formed by upward-traveling electrons from an acceleration source high in the corona, while their downward-traveling counterparts may undergo a secondary acceleration before producing HXRs via thick-target bremsstrahlung processes. In addition, the associated 3He=4He ratio is positively correlated with the observed high-energy spectral index of SEEs, indicating a possible relation of the 3He ion acceleration with high-energy SEEs

How to cite: Wang, W., Wang, L., Krucker, S., Mason, G. M., Su, Y., and Bucik, R.: Solar Energetic Electron Events Associated with Hard X-ray Flares , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10734, https://doi.org/10.5194/egusphere-egu21-10734, 2021.

EGU21-9543 | vPICO presentations | ST1.2

Connecting solar flare hard X-ray spectra to in-situ electron spectra using RHESSI and STEREO/SEPT observations

Nina Dresing, Alexander Warmuth, Frederic Effenberger, Ludwig Klein, Lindsay Glesener, Sophie Musset, and Maximilian Bruedern

In-situ observations of solar energetic particle events are determined by a combination of acceleration, injection, and transport processes which are often hard to disentangle. However, the energy spectrum of impulsive electron events is believed to carry the imprint of the flare acceleration process which can be studied by analyzing the hard X-ray (HXR) spectrum of the flare.

Using STEREO/SEPT electron data of the whole STEREO mission we have identified 64 solar energetic electron event candidates where the HXR solar counterpart of the event was observed by RHESSI. After cleaning of the data set and an independent verification by the timing of associated interplanetary type III radio bursts, we find 17 events which lend themselves for a comparison of the spectral indices observed in situ and at the Sun.

Special attention is paid to the choice of the in-situ electron spectral index used for comparison as most of the events show spectral transitions (breaks) in the measurement range of SEPT. We find that both the lower and higher spectral indices correlate similarly well with the HXR spectra yielding correlation coefficients of 0.8 but indicating opposite relations with the flare spectrum in terms of the thin- or thick target model. The correlations show no dependence on the electron onset delay, nor on the longitudinal separation between flare and spacecraft magnetic footpoint at the Sun. However, the correlations increase, if only events with significant anisotropy are used indicating that transport effects play a role in shaping the spectra observed in-situ. We will discuss the different transport effects that need to be taken into account and which may even lead to a vanishing imprint of the flare acceleration.

How to cite: Dresing, N., Warmuth, A., Effenberger, F., Klein, L., Glesener, L., Musset, S., and Bruedern, M.: Connecting solar flare hard X-ray spectra to in-situ electron spectra using RHESSI and STEREO/SEPT observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9543, https://doi.org/10.5194/egusphere-egu21-9543, 2021.

Solar type III radio bursts contain a wealth of information about the dynamics of near-relativistic electron beams in the solar corona and the inner heliosphere; this information is currently unobtainable through other means.  Whilst electron beams expand along their trajectory, the motion of different regions of an electron beam (front, middle, and back) had never been systematically analysed before.  Using LOw Frequency ARray (LOFAR) observations between 30-70 MHz of type III radio bursts, and kinetic simulations of electron beams producing derived type III radio brightness temperatures, we explored the expansion as electrons propagate away from the Sun.  From relatively moderate intensity type III bursts, we found mean electron beam speeds for the front, middle and back of 0.2, 0.17 and 0.15 c, respectively.  Simulations demonstrated that the electron beam energy density, controlled by the initial beam density and energy distribution have a significant effect on the beam speeds, with high energy density beams reaching front and back velocities of 0.7 and 0.35 c, respectively.  Both observations and simulations found that higher inferred velocities correlated with shorter FWHM durations of radio emission at individual frequencies.  Our radial predictions of electron beam speed and expansion can be tested by the upcoming in situ electron beam measurements made by Solar Orbiter and Parker Solar Probe.

How to cite: Reid, H. and Kontar, E.: Nonrelativistic electron beam expansion in the solar corona/wind  and their type III radio bursts observed with LOFAR, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11109, https://doi.org/10.5194/egusphere-egu21-11109, 2021.

EGU21-10101 | vPICO presentations | ST1.2

Detection of stratospheric X-rays with a novel microscintillator sensor

Karen Aplin, Graeme Marlton, Victoria Race, and Clare Watt

A new energetic particle detector based on a 1 cm3 CsI(Tl) scintillator crystal responds to both particle count and energy. This offers increased measurement capability over the long-established Geiger counter technology for investigating the role of energetic particles in the atmosphere during meteorological radiosonde flights. Here we present results from three flights over the UK in 2017-18 where the detector was flown alongside Geiger counters to test its capability for measuring ionising radiation in the atmosphere. Operation of the microscintillator detector was verified by both it and the Geiger counters showing the anticipated Regener-Pfotzer maximum at around 17km. Unexpectedly however, two of the flights also detected lower energy signals at 10-100 keV. Laboratory experiments investigating the thermal response of the microscintillator, in combination with careful error analysis, can be used to show that the signals detected do not originate from instrument artefacts, and are statistically significant. These are most likely to be stratospheric X rays, usually associated with bremsstrahlung radiation generated by precipitating electrons from the radiation belts.

How to cite: Aplin, K., Marlton, G., Race, V., and Watt, C.: Detection of stratospheric X-rays with a novel microscintillator sensor, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10101, https://doi.org/10.5194/egusphere-egu21-10101, 2021.

EGU21-7498 | vPICO presentations | ST1.2

The effect of Forbush decreases on the polar-night HOx concentration

Irina Mironova

It is well-known that energetic particle precipitations during solar proton events increase ionization rates in the middle atmosphere enhancing the production of hydrogen oxide radicals (HOx) involved in the catalytic ozone destruction cycle. There are many studies where the contribution of energetic particles to the formation of hydrogen oxide radicals and ozone loss has been widely investigated. However, until now, there was no solid evidence that the reduction in galactic cosmic ray fluxes during a magnetic storm, known as Forbush-effect, directly and noticeably affects the polar-night stratospheric chemistry.
Here, the impact of the Forbush decrease on the behaviour of hydrogen oxide radicals was explored using the chemistry-climate model SOCOL.
We found that hydrogen oxide radical lost about half of its concentration over the polar boreal night stratosphere owing to a reduction in ionization rates caused by Forbush decreases after solar proton events occurred on 17 and 20 of January 2005. A robust response in ozone was not found. There is not any statistically significant response in (NOx) on Forbush decrease events as well as over summertime in the southern polar region.
The results of this study can be used to increase the veracity of ozone loss estimation if stronger Forbush events can have a place.

Reference: Mironova I, Karagodin-Doyennel A and Rozanov E (2021) , The effect of Forbush decreases on the polar-night HOx concentration affecting stratospheric ozone. Front. Earth Sci. 8:618583. doi: 10.3389/feart.2020.618583

https://www.frontiersin.org/articles/10.3389/feart.2020.618583/full

The study was supported by the Russian Science Foundation grant (RSF project No. 20-67-46016).

How to cite: Mironova, I.: The effect of Forbush decreases on the polar-night HOx concentration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7498, https://doi.org/10.5194/egusphere-egu21-7498, 2021.

EGU21-858 | vPICO presentations | ST1.2

The Effect of Forbush Decreases on Atmospheric Aerosols and Clouds from The PATMOS-x Satellite from 1978 to 2018

Haruka Matsumoto, Henrik Svensmark, and Martin Enghoff

The solar system is constantly changing, and it is important for us to understand how our climate and weather changes in response to the solar activity during both long-time scales (e.g. the 11-year solar cycle) and short time scales (e.g. days to weeks during For-bush Decreases (FDs)). Solar variability causes a corresponding modulation of the incident number of cosmic rays in Earth's atmosphere. Previous work by [Veretenenko and Pudovkin, 1997], [Svensmark and Friis-Christensen, 1997], [Palle Bago and Butler, 2000], [Svensmark et al., 2016], [Harrison and Ambaum, 2010], and other researchers have discussed this cause-effect relationship from an experimental and theoretical approach. Since the 1970s, global observations of the Earth's system by satellites are offering an invaluable source of information about cloud parameters.

In this study, we used the newly calibrated PATMOS-x (Pathfinder Atmospheres Extended) data set during the period from 1978 to the present. A method for capturing the connection between cosmic rays and meteorological measurements has been conducted by superposition analysis of FD events for time series (36 days) and the Monte Carlo bootstrap test to evaluate significance level of the integrated signal for 9 days after the minimum in FD. We have reviewed results, primarily about cloud emissivity (Achieved Significance Level (ASL >99%), surface brightness temperature (ASL >99%), and cloud fraction (ASL >99%). Some of the results support the proposed relationship between solar activity and temperature. This result indicates that the amount of incident cosmic rays decreases due to FDs, global average temperature increases [Friis-Christensen and Lassen, 1991], [Harrison and Ambaum, 2010]. In addition, PATMOS-x parameters of cloud probability, cloud mask, and cloud fraction, which all means cloud coverage on the Earth shows statistically significant signals following FDs. In some previous research, IR-detected cloud fraction from International Satellite Cloud Climate Project (ISCCP) and combined liquid and ice cloud fraction, effective emissivity from the Moderate Resolution Imaging Spectroradiometer (MODIS) also show connection with FDs, see [Svensmark et al., 2009], [Svensmark et al., 2016], [Marsh and Svensmark, 2000a], Todd and Kniveton [2004]. The relationship between the observed changes in cloud amount and the resulting solar forcing is discussed. On the other hand, “Cloud water content" from Special Sensor Microwave Imager (SSM/I), “Liquid water path", and “Optical thickness" from MODIS also showed as significant signals by FDs, see [Svensmark et al., 2009], [Svensmark et al., 2016], however a similar parameter about “optical thickness" and “integrated total cloud water over whole column g/m2" from PATMOS-x dataset does not have high significant signals by a bootstrap test with ASL of 77.03 and 92.51% respectively. Moreover, significant results are reported for several new cloud parameters from the PATMOS-x dataset (e.g. cloud type, brightness temperature, measurements by different wavelength 0.65, 0.86, 3.75, 11.0, and 12.0 μm and others) and Fu-Liou model is used for estimation of changed radiations in the atmosphere. An interaction between CCN and radiation has not been investigated well yet. It is necessary to still more to learn about these results for further understanding of Earth’s atmosphere.

How to cite: Matsumoto, H., Svensmark, H., and Enghoff, M.: The Effect of Forbush Decreases on Atmospheric Aerosols and Clouds from The PATMOS-x Satellite from 1978 to 2018, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-858, https://doi.org/10.5194/egusphere-egu21-858, 2021.

EGU21-3376 | vPICO presentations | ST1.2

Influence of energetic particle precipitation on polar vortex mediated by planetary wave activity

Timo Asikainen, Antti Salminen, Ville Maliniemi, and Kalevi Mursula

The northern polar vortex experiences considerable inter-annual variability, which is also reflected to tropospheric weather. Recent research has established a link between polar vortex variations and energetic electron precipitation (EEP) from the near-Earth space into the polar atmosphere, which is mediated by EEP-induced chemical changes causing ozone loss in the mesosphere and stratosphere. However, the most dramatic changes in the polar vortex are due to strong enhancements of planetary wave activity, which typically result in a sudden stratospheric warming (SSW), a momentary breakdown of the polar vortex. Here we use the SSWs as an indicator of high planetary wave activity and consider their influence of SSWs on the atmospheric response to EEP in 1957-2017 using combined ERA-40 and ERA-Interim re-analysis data and geomagnetic activity as a proxy of EEP. We find that the EEP-related enhancement of the polar vortex and other associated dynamical responses are seen only during winters when a SSW occurs, and that the EEP-related changes take place slightly before the SSW onset. We show that the atmospheric conditions preceding SSWs favor enhanced wave-mean-flow interaction, which can dynamically amplify the initial polar vortex enhancement caused by ozone loss. These results highlight the importance of considering SSWs and sufficient level of planetary wave activity as a necessary condition for observing the effects of EEP on the polar vortex dynamics.

How to cite: Asikainen, T., Salminen, A., Maliniemi, V., and Mursula, K.: Influence of energetic particle precipitation on polar vortex mediated by planetary wave activity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3376, https://doi.org/10.5194/egusphere-egu21-3376, 2021.

EGU21-15895 | vPICO presentations | ST1.2

The Atmospheric Ionization during Substorm Model

Olesya Yakovchuk and Jan Maik Wissing

The Atmospheric Ionization during Substorm Model (AISstorm) is the successor of the Atmospheric Ionization Module Osnabrück (AIMOS) and thus may also be considered as AIMOS 2.0 - AISStorm.

The overall structure was kept mostly unaltered and splits up into an empirical model that determines the 2D precipitating particle flux and a numerical model that determines the ionization profile of single particles. The combination of these two results in a high resolution 3D particle ionization pattern.

The internal structure of the model has been completely revised with the main aspects being: a) an internal magnetic coordinate system, b) including substorms characteristics, c) higher time resolution, d) higher spatial resolution, e) energy specific separate handling of drift loss cone, auroal precipitation and polar cap precipitation, partly even in separate coordinate systems, f) better MLT resolution and g) covering a longer time period. All these tasks have been matched while keeping the output data format identical, allowing easy transition to the new version.

How to cite: Yakovchuk, O. and Wissing, J. M.: The Atmospheric Ionization during Substorm Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15895, https://doi.org/10.5194/egusphere-egu21-15895, 2021.

EGU21-2362 | vPICO presentations | ST1.2

The Mansurov Effect: Real or a statistical artefact?

Jone Edvartsen, Ville Maliniemi, Hilde Tyssøy, Timo Asikainen, and Spencer Hatch

The Mansurov Effect is related to the interplanetary magnetic field (IMF) and its ability to modulate the global electric circuit, which is further hypothesized to impact the polar troposphere through cloud generation processes. In this paper we investigate the connection between IMF By-component and polar surface pressure by using daily ERA5 reanalysis for geopotential height since 1980. Previous studies have shown to produce a significant 27-day cyclic response during solar cycle 23. However, when appropriate statistical tests are applied, the correlation is not significant at the 95% level. Our results also show that data from three other solar cycles, which have not been investigated before, produce similar cyclic responses as during solar cycle 23, but with seemingly random offset in the timing of the signal. We examine the origin of the cyclic pattern occurring in the super epoch/lead lag regression methods commonly used to support the Mansurov hypothesis in all recent papers, as well as other phenomena in this community. By generating random normally distributed noise with different levels of temporal autocorrelation, and using the real IMF By-index as forcing, we show that the methods applied to support the Mansurov hypothesis up to now, are highly susceptible, as cyclic patterns always occurs as artefacts of the methods. This, in addition to the lack of significance, suggests that there is no adequate evidence in support of the Mansurov Effect.

How to cite: Edvartsen, J., Maliniemi, V., Tyssøy, H., Asikainen, T., and Hatch, S.: The Mansurov Effect: Real or a statistical artefact?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2362, https://doi.org/10.5194/egusphere-egu21-2362, 2021.

ST1.3 – First results from the Solar Orbiter mission

EGU21-2981 | vPICO presentations | ST1.3 | Highlight

The Solar Orbiter mission – Exploring the Sun and heliosphere

Daniel Mueller, Yannis Zouganelis, Teresa Nieves-Chinchilla, and Chris St. Cyr

Solar Orbiter, launched on 10 February 2020, is a space mission of international collaboration between ESA and NASA. It is exploring the linkage between the Sun and the heliosphere and has started to collect unique data at solar distances down to 0.49 AU. By ultimately approaching as close as 0.28 AU, Solar Orbiter will view the Sun with very high spatial resolution and combine this with in-situ measurements of the surrounding heliosphere. Over the course of the mission, the highly elliptical orbit will get progressively more inclined to the ecliptic plane. Thanks to this new perspective, Solar Orbiter will deliver images and comprehensive data of the unexplored Sun’s polar regions and the side of the Sun not visible from Earth. This talk will highlight first science results from Solar Orbiter and provide a mission status update.

How to cite: Mueller, D., Zouganelis, Y., Nieves-Chinchilla, T., and St. Cyr, C.: The Solar Orbiter mission – Exploring the Sun and heliosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2981, https://doi.org/10.5194/egusphere-egu21-2981, 2021.

EGU21-15792 | vPICO presentations | ST1.3 | Highlight

First Results from Solar Orbiter’s Energetic Particle Detector

Javier Rodriguez-Pacheco and the EPD Team

In this presentation, we will show the first measurements performed by EPD since the end of the commissioning phase until the latest results obtained. During these months EPD has been scanning the inner heliosphere at different heliocentric distances and heliolongitues allowing - together with other spacecraft - to investigate the spatio-temporal behavior of the particle populations in the inner heliosphere during solar minimum conditions. Solar Orbiter was launched from Cape Canaveral on February 10th, 2020, thus beginning the journey to its encounter with the Sun. Solar Orbiter carries ten scientific instruments, six remote sensing and four in situ, that will allow the mission main goal: how the Sun creates and controls the heliosphere. Among the in situ instruments, the Energetic Particle Detector (EPD) measures electrons, protons and heavy ions with high temporal resolution over a wide energy range, from suprathermal energies up to several hundreds of MeV/nucleon.

How to cite: Rodriguez-Pacheco, J. and the EPD Team: First Results from Solar Orbiter’s Energetic Particle Detector, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15792, https://doi.org/10.5194/egusphere-egu21-15792, 2021.

EGU21-5927 | vPICO presentations | ST1.3

The Energetic Particle Detector (EPD) Electron-Proton Telescope (EPT) on Solar Orbiter: In-flight calibration and background correction of science data.

Daniel Pacheco, Alexander Kollhoff, Robert F. Wimmer-Schweingruber, Johan L. Freiherr von Forstner, Christoph Terasa, Robert Elftmann, Sebastian Boden, Lars Berger, Sandra Eldrum, Zigong Xu, Javier Rodríguez-Pacheco, George Ho, and Raúl Gómez-Herrero and the The EPD Team

Solar Orbiter was launched in February 2020 carrying the most complete set of in-situ and remote sensing instruments, for the study of the Sun and the heliosphere. The Energetic Particle Detector (EPD) on board of Solar Orbiter was switched on on 28 February 2020 and, since then, it has provided us with measurements of the energetic particles traveling through the inner heliosphere. The EPD suite is composed of a set of different sensors measuring electrons, protons and ions in a wide range of energies.

The Electron-Proton Telescope (EPT) was designed to measure electrons and ions with energies of 35-4000keV and 45-7000keV respectively. By utilizing the so-called magnet/foil-technique, EPT is capable of measuring energetic particles with a high temporal and energy resolution while obtaining directional information from its four different fields of view. Although EPT is well suited for the study of solar energetic particle events, instrumental effects such as the contamination of EPT data products by GCR particles need to be understood for a correct interpretation of the data.

We will present our current understanding of the background and calibration of EPT based on the data gathered during the first year of Solar Orbiter’s mission.

How to cite: Pacheco, D., Kollhoff, A., Wimmer-Schweingruber, R. F., von Forstner, J. L. F., Terasa, C., Elftmann, R., Boden, S., Berger, L., Eldrum, S., Xu, Z., Rodríguez-Pacheco, J., Ho, G., and Gómez-Herrero, R. and the The EPD Team: The Energetic Particle Detector (EPD) Electron-Proton Telescope (EPT) on Solar Orbiter: In-flight calibration and background correction of science data., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5927, https://doi.org/10.5194/egusphere-egu21-5927, 2021.

EGU21-15152 | vPICO presentations | ST1.3

The Energetic Particle Detector (EPD) Electron-Proton Telescope (EPT) on Solar Orbiter: First Data

Alexander Kollhoff, Daniel Pacheco, Robert F. Wimmer-Schweingruber, Johan von Forstner, Lars Berger, Sandra Eldrum, Zigong Xu, Bernd Heber, Javier Rodriguez-Pacheco, and George Ho and the EPD team

Solar Orbiter’s Energetic Particle Detector (EPD) was commissioned in early 2020 and has since been returning data from the inner heliosphere. Despite the low activity in the current deep and extended solar minimum, EPD has observed a number of solar particle events and numerous other enhancements of energetic particles. As one of the four complementary EPD sensors, the Electron-Proton Telescope (EPT) covers the gap between the high and low particle-energy measurements of HET and STEP. With four double-ended telescopes, EPT is capable of measuring electrons and ions in an energy range of 35-400keV and 45-7000keV respectively, while providing anisotropy information from four different viewing directions.

We will present a first overview of EPT measurements, exhibiting some of the EPT data products which are made available by the European Space Agency (ESA).

In order to provide the community a deep insight into the data, we will go through different aspects of the measurements, including the current status of the intercalibration with the other EPD instruments.

How to cite: Kollhoff, A., Pacheco, D., Wimmer-Schweingruber, R. F., von Forstner, J., Berger, L., Eldrum, S., Xu, Z., Heber, B., Rodriguez-Pacheco, J., and Ho, G. and the EPD team: The Energetic Particle Detector (EPD) Electron-Proton Telescope (EPT) on Solar Orbiter: First Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15152, https://doi.org/10.5194/egusphere-egu21-15152, 2021.

EGU21-6776 | vPICO presentations | ST1.3

The High Energy Telescope (HET) on the SolarOrbiter Mission: Overview and First Data

Zigong Xu, Johan L. Freiherr von Forstner, Patrick Kühl, Nils Janitzek, César Martín, Shrinivasrao R. Kulkarni, Stephan I. Böttcher, Robert F. Wimmer-Schweingruber, Javier Rodríguez-Pacheco, Glenn M. Mason, and George C. Ho and the Solar Orbiter EPD team

As part of the Energetic Particle Detector (EPD) suite onboard Solar Orbiter, the High Energy Telescope has been launched on its mission to the Sun on February 9, 2020, and has been measuring energetic particles since it was first switched on about two weeks after launch. Using their double-ended telescopes, the two HET units provide measurements of ions above 7 MeV/nuc and electrons above 300 keV in four viewing directions. HET observed several Solar Energetic Particle (SEPs) events during the cruise phase, including the first one with a broad energy coverage (up to ~100MeV) on 29 Nov 2020. Being the first larger SEP event in a phase of rising solar activity, these measurements have already attracted extensive attention of the community. Apart from the SEPs, the HET can be used to observe the Galactic cosmic radiation (GCR) and its temporal variation. The GCR measurements can be also utilized for the validation of the energy response of HET. The overall spectra observed by HET are as expected, except for calibration issues in some specific energy bins that we are still investigating. Finally, the HET also observed several Forbush Decreases (FD), i.e. cosmic ray decreases caused by CMEs and their embedded magnetic field. Here, the capabilities and data products of HET, as well as first measurements of SEPs, GCR and FDs are presented. 

How to cite: Xu, Z., Freiherr von Forstner, J. L., Kühl, P., Janitzek, N., Martín, C., Kulkarni, S. R., Böttcher, S. I., Wimmer-Schweingruber, R. F., Rodríguez-Pacheco, J., Mason, G. M., and Ho, G. C. and the Solar Orbiter EPD team: The High Energy Telescope (HET) on the SolarOrbiter Mission: Overview and First Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6776, https://doi.org/10.5194/egusphere-egu21-6776, 2021.

EGU21-13329 | vPICO presentations | ST1.3

First solar electron events observed by EPD aboard Solar Orbiter

Raúl Gómez-Herrero, Daniel Pacheco, Alexander Kollhoff, Francisco Espinosa Lara, Johan L. Freiherr von Forstner, Nina Dresing, David Lario, Laura Balmaceda, Vratislav Krupar, Olga E. Malandraki, Angels Aran, Radoslav Bucik, Andreas Klassen, Karl-Ludwig Klein, Ignacio Cernuda, Sandra Eldrum, Hamish Reid, John G. Mitchell, Glenn M. Mason, and George C. Ho and the Solar Orbiter EPD/RPW/MAG/SWA Teams

The first solar electron events detected by Solar Orbiter were observed by the Energetic Particle Detector (EPD) suite during July 11-23, 2020, when the spacecraft was at heliocentric distances between 0.61 and 0.69 au. We combined EPD electron observations from 4 keV to the relativistic range (few MeV), radio dynamic spectra and extreme ultraviolet (EUV) observations from multiple spacecraft in order to identify the solar origin of these electron events. Electron anisotropies and timing as well as the plasma and magnetic field environment were evaluated to characterize the interplanetary transport conditions. We found that all the electron events were clearly associated with type III radio bursts. EUV jets were also found in association with all of them except one. A diversity of time profiles and pitch-angle distributions (ranging from almost isotropic to beam-like) was observed. These observations indicate that different source locations and different magnetic connectivity and transport conditions were likely involved. The broad spectral range covered by EPD with excellent energy resolution and the high time cadence ensure that future observations close to the Sun will contribute to the understanding of the acceleration, release, and transport processes of energetic particles. EPD observations will play a key role in the identification of the sources of impulsive events and the links between the near-relativistic electrons and the ion populations enriched in 3He and heavy ions

 

How to cite: Gómez-Herrero, R., Pacheco, D., Kollhoff, A., Espinosa Lara, F., Freiherr von Forstner, J. L., Dresing, N., Lario, D., Balmaceda, L., Krupar, V., Malandraki, O. E., Aran, A., Bucik, R., Klassen, A., Klein, K.-L., Cernuda, I., Eldrum, S., Reid, H., Mitchell, J. G., Mason, G. M., and Ho, G. C. and the Solar Orbiter EPD/RPW/MAG/SWA Teams: First solar electron events observed by EPD aboard Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13329, https://doi.org/10.5194/egusphere-egu21-13329, 2021.

EGU21-15864 | vPICO presentations | ST1.3

The low-energy ion event on 2020 June 19 measured by Solar Orbiter

Angels Aran, Daniel Pacheco, Monica Laurenza, Nicolas Wijsen, Evangelia Samara, David Lario, Laura Balmaceda, Johan L. Freiherr von Forstner, Simone Benella, Luciano Rodriguez, and Raúl Gómez-Herrero and the The low-energy ion event on 2020 June 19 study Team

Shortly after reaching the first perihelion, the Energetic Particle Detector (EPD) onboard Solar Orbiter measured a low-energy (<1 MeV/nuc) ion event whose duration varied with the energy of the particles. The increase above pre-event intensity levels was detected early on June 19 for ions in the energy range from ~50 keV to ~1 MeV and lasted up to ~12:00 UT on June 20. In the energy range from ~10 keV to < 40 keV, the ion event spanned from June 18 to 21. This latter low-energy ion intensity enhancement coincided with a two-step Forbush decrease (FD) as displayed in the EPD > 17 MeV/nuc ion measurements. On the other hand, no electron increases were detected. As seen from 1 au, there is no clear evidence of solar activity from the visible disk that could be associated with the origin of this ion event. We hypothesize about the origin of this event as due to either a possible solar eruption occurring behind the visible part of the Sun or to an interplanetary spatial structure. We use interplanetary magnetic field data from the Solar Orbiter Magnetometer (MAG), solar wind electron density derived from measurements of the Solar Orbiter Radio and Plasma Waves (RPW) instrument to specify the in-situ solar wind conditions where the ion event was observed. In addition, we use solar wind plasma measurements from the Solar Orbiter Solar Wind Analyser (SWA) suite gathered during the following solar rotation, for comparison purposes. In order to seek for possible associated solar sources, we use images from the Extreme Ultraviolet Imager (EUI) instrument onboard Solar Orbiter. Together with the lack of electron observations and Type III radio bursts, the simultaneous response of the ion intensity-time profiles at various energies indicates an interplanetary source for the particles. The two-step FD shape observed during this event suggests that the first step early on June 18 was due to a transient structure, whereas the second step on June 19, together with the ~50 –1000 keV/nuc ion enhancement, was due to a solar wind stream interaction region. The observation of a similar FD in the next solar rotation favours this interpretation, although a more complex structure cannot be discarded due to the lack of concurrent solar wind temperature and velocity observations.

Different parts of this research have received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) and grant agreement No 01004159 (SERPENTINE).

How to cite: Aran, A., Pacheco, D., Laurenza, M., Wijsen, N., Samara, E., Lario, D., Balmaceda, L., von Forstner, J. L. F., Benella, S., Rodriguez, L., and Gómez-Herrero, R. and the The low-energy ion event on 2020 June 19 study Team: The low-energy ion event on 2020 June 19 measured by Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15864, https://doi.org/10.5194/egusphere-egu21-15864, 2021.

EGU21-12501 | vPICO presentations | ST1.3 | Highlight

Early Observations from the Solar Orbiter SWA/Electron Analyser System

Christopher Owen and the the International SWA, MAG and RPW teams.

Solar Orbiter carries a total of 10 instrument suites making up the payload for the mission.  One of these, the Solar Wind Analyser (SWA) instrument, is comprised of 3 sensor units which are together served by a central DPU unit.  Of particular focus in this presentation are the early measurements from one of these sensors, the Electron Analyser System (EAS).  EAS is a dual-head, top-hat electrostatic analyser system that is capable of making 3D measurements of solar wind electrons at energies below ~5 keV from a vantage point at the end of a 4-metre boom extending into the shadow of the spacecraft.  The sensor was accommodated in this location to both maximise the unobstructed field of view and to minimise the effect of spacecraft related disturbances on the low-energy (less than a few tens of eV) electrons expected the core population of the solar wind.

To date the SWA instrument sensors have operated sporadically during the mission cruise phase, which began in June 2020.  This is due to a number of operational issues faced by the SWA team, which mean we have not been able to take data in a continuous manner.  However, the data that has been taken shows the clear promise of the SWA measurements, in general, once these issues can be overcome.  For example, EAS is using a novel sample steering mechanism in burst mode which, with reference to a magnetic field vector shared onboard by the MAG instrument, allows the capture of the electron pitch angle distribution at unusually high time resolution.  We discuss these observations here, and illustrate the potential science returns from the burst mode.  We also present results from the new EAS observations in the vicinity of reconnecting current sheets in the solar wind, to more generally illustrate the capability of the sensor. 

How to cite: Owen, C. and the the International SWA, MAG and RPW teams.: Early Observations from the Solar Orbiter SWA/Electron Analyser System, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12501, https://doi.org/10.5194/egusphere-egu21-12501, 2021.

EGU21-12435 | vPICO presentations | ST1.3

Updates and Early Results from the Heavy Ion Sensor on Solar Orbiter

Susan T. Lepri, Stefano A. Livi, Jim M. Raines, Antoinette B. Galvin, Lynn M. Kistler, Ryan M. Dewey, Benjamin L. Alterman, Frederic Allegrini, Michael R. Collier, and Christopher J. Owen

 

The Solar Orbiter mission was launched in 2020 into an orbit that will explore the inner heliosphere. During its orbit, periods of quasi-corotation with the Sun will enable determination of the source regions on the Sun for solar wind structures.  The Solar Wind Analyser (SWA) is a suite of instruments that provide in-situ measurements of solar wind electrons, protons, alpha particles, and heavy ions.  The SWA-Heavy Ion Sensor (HIS) is optimized to measure heavy ions in the solar wind, pickup ions, and suprathermal ions in an energy range spanning from 0.5- 75keV/e.  We present measurements of heavy ion composition from SWA-HIS taken during the cruise phase of the mission to highlight the capabilities of the instrument and the observations we expect to collect over the next 10 years. We discuss how SWA-HIS will enable linkages between the Sun and the solar wind to reveal the nature of the acceleration and release of the solar wind and the sources and structure of the solar wind.  We will also provide an overview of the available data and accessibility of the public datasets. 

How to cite: Lepri, S. T., Livi, S. A., Raines, J. M., Galvin, A. B., Kistler, L. M., Dewey, R. M., Alterman, B. L., Allegrini, F., Collier, M. R., and Owen, C. J.: Updates and Early Results from the Heavy Ion Sensor on Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12435, https://doi.org/10.5194/egusphere-egu21-12435, 2021.

EGU21-592 | vPICO presentations | ST1.3 | Highlight

Overview of interplanetary coronal mass ejections observed by Solar Orbiter, Parker Solar Probe, Bepi Colombo, Wind and STEREO-A

Christian Möstl, Andreas J. Weiss, Rachel L. Bailey, Martin A. Reiss, Tanja Amerstorfer, Jürgen Hinterreiter, Maike Bauer, Ute V. Amerstorfer, Emma E. Davies, Tim Horbury, David Barnes, Jackie A. Davies, Richard A. Harrison, Daniel Heyner, Ingo Richter, Hans-Ulrich Auster, Werner Magnes, and Wolfgang Baumjohann

We show in situ observations of ICMEs during the first year of Solar Orbiter observations based on magnetic field data from the MAG instrument in conjunction with in situ and imaging observations from the Heliospheric System Observatory. The in situ magnetic field data from four other currently active spacecraft - Parker Solar Probe, BepiColombo, STEREO-Ahead and Wind -  are also searched for ICME signatures, and all clear ICME events that could be identified by classic signatures such as elevated and rotating magnetic fields of sufficiently long durations are included in a living online catalog. Furthermore, we provide a visualization of the in situ magnetic field data alongside spacecraft positions and propagating CME fronts, which are based on modeling of STEREO-A heliospheric imager data. This allows us to identify ICME events that could be unambiguously followed from their inception on the Sun to their impact at the aforementioned spacecraft, and highlights sought-after lineup events, in which the same ICME is observed at multiple points in space, such as the well-studied 2020 April 15-20 ICME. We discuss the ICME rate observed so far, and provide an outlook on the expected ICME rate in solar cycle 25 based on different forecasts for the cycle amplitude (see Möstl et al. 2020, https://doi.org/10.3847/1538-4357/abb9a1).

How to cite: Möstl, C., Weiss, A. J., Bailey, R. L., Reiss, M. A., Amerstorfer, T., Hinterreiter, J., Bauer, M., Amerstorfer, U. V., Davies, E. E., Horbury, T., Barnes, D., Davies, J. A., Harrison, R. A., Heyner, D., Richter, I., Auster, H.-U., Magnes, W., and Baumjohann, W.: Overview of interplanetary coronal mass ejections observed by Solar Orbiter, Parker Solar Probe, Bepi Colombo, Wind and STEREO-A, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-592, https://doi.org/10.5194/egusphere-egu21-592, 2021.

EGU21-8878 | vPICO presentations | ST1.3

Triple-point magnetic flux rope analysis for the 2020 April 19 CME observed in situ by Solar Orbiter, Bepi Colombo, and WIND

Andreas J. Weiss, Christian Möstl, Emma Davies, Matthew J. Owens, Tanja Amerstorfer, Maike Bauer, Jürgen Hinterreiter, Rachel L. Bailey, Martin A. Reiss, Tim Horbury, Helen O'Brien, Vincent Evans, Virginia Angelini, Daniel Heyner, Ingo Richter, Uli Auster, Werner Magnes, and Wolfgang Baumjohann

We present initial results for a triple-point analysis for the in situ magnetic field measurements of a CME observed at three independent locations. On the 19th of April 2020, Solar Orbiter observed a CME in situ at a radial distance of around 0.8 au. This CME was subsequently also detected by the Wind and Bepi Colombo satellites closer to Earth. This triple in situ measurement of a CME provides us the unique opportunity to test the consistency of the measurements with our own 3D Coronal Rope Ejection (3DCORE) model. A triple measurement allows for up to seven different data combinations to be analyzed (three single-point, three dual-point, and one single triple-point combination) which gives us information on how our analysis pipeline responds to multi-point measurements and how the results change with measurements at differing radial and longitudinal distances. The goal of this study is to test whether all three in situ measurements can still be described by a slightly bent flux rope geometry and how adding additional measurements can improve the accuracy of inferred model parameters.

How to cite: Weiss, A. J., Möstl, C., Davies, E., Owens, M. J., Amerstorfer, T., Bauer, M., Hinterreiter, J., Bailey, R. L., Reiss, M. A., Horbury, T., O'Brien, H., Evans, V., Angelini, V., Heyner, D., Richter, I., Auster, U., Magnes, W., and Baumjohann, W.: Triple-point magnetic flux rope analysis for the 2020 April 19 CME observed in situ by Solar Orbiter, Bepi Colombo, and WIND, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8878, https://doi.org/10.5194/egusphere-egu21-8878, 2021.

EGU21-4996 | vPICO presentations | ST1.3

Switchback-like structures observed by Solar Orbiter

Andrey Fedorov, Philippe Louarn, Christopher Owen, Lubomir Prech, Timothy Horbury, Alain Barthe, Alexis Rouillard, Justin Kasper, Stuart Bale, Roberto Bruno, Helen O’Brien, Vincent Evans, Virginia Angelini, Davin Larson, and Roberto Livi and the SWA-PAS, MAG, SWEAP, and FIELDS teams

During 27th September 2020 NASA Parker Solar Probe (PSP) and ESA-NASA Solar Orbiter (SolO) have been located around the same Carrington longitude and their latitudinal separation was very small as well. Solar wind plasma and magnetic field data obtained throughout this time interval  allows to consider that sometimes the solar wind, observed by both spacecrafts, originates from the same coronal hole region. Inside these time intervals the SolO radial magnetic field experiences several short variations similar to the "switchbacks" regularly observed by PSP. We used the SolO SWA-PAS proton analyzer data to analyze the ion distribution function variations inside such switchback-like events to understand if such events are really "remains" of the alfvenic structures observed below 60 Rs.

How to cite: Fedorov, A., Louarn, P., Owen, C., Prech, L., Horbury, T., Barthe, A., Rouillard, A., Kasper, J., Bale, S., Bruno, R., O’Brien, H., Evans, V., Angelini, V., Larson, D., and Livi, R. and the SWA-PAS, MAG, SWEAP, and FIELDS teams: Switchback-like structures observed by Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4996, https://doi.org/10.5194/egusphere-egu21-4996, 2021.

EGU21-6306 | vPICO presentations | ST1.3

The solar wind angular-momentum flux observed during Solar Orbiter's first orbit

Daniel Verscharen, David Stansby, Adam Finley, Christopher Owen, Timothy Horbury, Marco Velli, Stuart Bale, Philippe Louarn, Andrei Fedorov, Roberto Bruno, Stefano Livi, Gethyn Lewis, Chandrasekhar Anekallu, Christopher Kelly, Gillian Watson, Dhiren Kataria, Helen O'Brien, Vincent Evans, and Virginia Angelini

The Solar Orbiter mission is currently in its cruise phase, during which the spacecraft's in-situ instrumentation measures the solar wind and the electromagnetic fields at different heliocentric distances. 

We evaluate the solar wind angular-momentum flux by combining proton data from the Solar Wind Analyser (SWA) Proton-Alpha Sensor (PAS) and magnetic-field data from the Magnetometer (MAG) instruments on board Solar Orbiter during its first orbit. This allows us to evaluate the angular momentum in the protons in addition to that stored in magnetic-field stresses, and compare these to previous observations from other spacecraft. We discuss the statistical properties of the angular-momentum flux and its dependence on solar-wind properties. 

Our results largely agree with previous measurements of the solar wind’s angular-momentum flux in the inner heliosphere and demonstrate the potential for future detailed studies of large-scale properties of the solar wind with the data from Solar Orbiter.

How to cite: Verscharen, D., Stansby, D., Finley, A., Owen, C., Horbury, T., Velli, M., Bale, S., Louarn, P., Fedorov, A., Bruno, R., Livi, S., Lewis, G., Anekallu, C., Kelly, C., Watson, G., Kataria, D., O'Brien, H., Evans, V., and Angelini, V.: The solar wind angular-momentum flux observed during Solar Orbiter's first orbit, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6306, https://doi.org/10.5194/egusphere-egu21-6306, 2021.

EGU21-5247 | vPICO presentations | ST1.3

Solar Orbiter observations of magnetic Kelvin-Helmholtz waves in the solar wind

Rungployphan Kieokaew, Benoit Lavraud, David Ruffolo, William Matthaeus, Yan Yang, Julia Stawarz, Sae Aizawa, Philippe Louarn, Alexis Rouillard, Vincent Génot, Andrey Fedorov, Rui Pinto, Claire Foullon, Christopher Owen, and Timothy Horbury

The Kelvin-Helmholtz instability (KHI) is a nonlinear shear-driven instability that develops at the interfaces between shear flows in plasmas. KHI is ubiquitous in plasmas and has been observed in situ at planetary interfaces and at the boundaries of coronal mass ejections in remote-sensing observations. KHI is also expected to develop at flow shear interfaces in the solar wind, but while it was hypothesized to play an important role in the mixing of plasmas and exciting solar wind fluctuations, its direct observation in the solar wind was still lacking. We report first in-situ observations of ongoing KHI in the solar wind using Solar Orbiter during its cruise phase. The KHI is found in a shear layer in the slow solar wind near the Heliospheric Current Sheet. We find that the observed conditions satisfy the KHI onset criterion from linear theory and the steepening of the shear boundary layer is consistent with the development of KH vortices. We further investigate the solar wind source of this event to understand the conditions that support KH growth. In addition, we set up a local MHD simulation using the empirical values to reproduce the observed KHI. This observed KHI in the solar wind provides robust evidence that shear instability develops in the solar wind, with obvious implications in the driving of solar wind fluctuations and turbulence. The reasons for the lack of previous such measurements are also discussed.

How to cite: Kieokaew, R., Lavraud, B., Ruffolo, D., Matthaeus, W., Yang, Y., Stawarz, J., Aizawa, S., Louarn, P., Rouillard, A., Génot, V., Fedorov, A., Pinto, R., Foullon, C., Owen, C., and Horbury, T.: Solar Orbiter observations of magnetic Kelvin-Helmholtz waves in the solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5247, https://doi.org/10.5194/egusphere-egu21-5247, 2021.

EGU21-9288 | vPICO presentations | ST1.3

The sheath region of April 2020 magnetic cloud and the associated energetic ions 

Emilia Kilpua, Simon Good, Nina Dresing, Rami Vainio, Emma Davies, Robert Forsyth, Benoit Lavraud, Daniel Heyner, Tim Horbury, Virginia Angeli, Helen O'Brien, Vincent Evans, Bob Wimmer, Javier Rodriguez-Pacheco, Raul Gomez-Herrero, and George Ho

Acceleration of energetic particles is a fundamental and ubiquitous mechanism in space and astrophysical plasmas. One of the open questions is the role of the sheath region behind the shock in the acceleration process. We analyze observations by Solar Orbiter, BepiColombo and the L1 spacecraft to explore the structure of a coronal mass ejection (CME)-driven sheath and its relation to enhancements of energetic ions that occurred on April 19-20, 2020. Our detailed analysis of the magnetic field, plasma and particle observations show that the enhancements were related to the Heliospheric Current Sheet crossings related to the reconnecting current sheets in the vicinity of the shock and a mini flux rope that was compressed at the leading edge of the CME ejecta. This study highlights the importance of smaller-scale sheath structures for the energization process. These structures likely formed already closer to the Sun and were swept and compressed from the upstream wind past the shock into the sheath. The upcoming observations by the recent missions (Solar Orbiter, Parker Solar Probe and BepiColombo) provide an excellent opportunity to explore further their role.  

How to cite: Kilpua, E., Good, S., Dresing, N., Vainio, R., Davies, E., Forsyth, R., Lavraud, B., Heyner, D., Horbury, T., Angeli, V., O'Brien, H., Evans, V., Wimmer, B., Rodriguez-Pacheco, J., Gomez-Herrero, R., and Ho, G.: The sheath region of April 2020 magnetic cloud and the associated energetic ions , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9288, https://doi.org/10.5194/egusphere-egu21-9288, 2021.

EGU21-9712 | vPICO presentations | ST1.3

Turbulence and intermittency of electron density fluctuations in the inner heliosphere: Solar Orbiter first data.

Luca Sorriso-Valvo, Francesco Carbone, Yuri Yuri Khotyaintsev, Daniel Graham, Konrad Steinvall, and Daniele Telloni and the The Solar Orbiter RPW and MAG Teams

The recently released spacecraft potential measured by the RPW instrument onboard Solar Orbiter has been used to estimate the solar wind electron density in the inner heliosphere. Selected intervals have been extracted to study and quantify the properties of turbulence. Empirical Mode Decomposition was used to obtain the generalized marginal Hilbert spectrum, equivalent to the structure functions analysis, additionally reducing issues typical of nonstationary time series. Results show the presence of a well defined inertial range with Kolmogorov scaling. However, the turbulence shows intermittency only in part of the samples, while other intervals have homogeneous scale-dependent fluctuations. These are observed predominantly during intervals of ion-frequency wave activity. Comparisons with compressible magnetic field intermittency (from the MAG instrument) and with an estimate of the solar wind velocity (using electric and magnetic field) are also provided to provide general context and help determine the cause for the absence of intermittency.

How to cite: Sorriso-Valvo, L., Carbone, F., Yuri Khotyaintsev, Y., Graham, D., Steinvall, K., and Telloni, D. and the The Solar Orbiter RPW and MAG Teams: Turbulence and intermittency of electron density fluctuations in the inner heliosphere: Solar Orbiter first data., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9712, https://doi.org/10.5194/egusphere-egu21-9712, 2021.

EGU21-10023 | vPICO presentations | ST1.3

Large amplitude ion-acoustic waves observed in the solar wind by the Solar Orbiter

David Pisa, Jan Soucek, Ondrej Santolik, Milan Maksimovic, Timothy Horbury, and Christopher Owen and the SolO RPW, MAG, and SWA instrument teams

Electric field observations of the Time Domain Sampler (TDS) receiver, a part of the Radio and Plasma Waves (RPW) instrument onboard Solar Orbiter, often exhibit very intense broadband emissions at frequencies below 10 kHz in the spacecraft frame. The RPW instrument has been operating almost continuously during the commissioning phase of the mission from March to May, the first perihelion in June, and through the first flyby of Venus in late December 2020. Nearly a year of observations allow us to perform a statistical study of ion-acoustic waves in the solar wind covering an interval of heliocentric distances between 0.5 AU to 1 AU. The occurrence of low-frequency waves peaks around perihelion in June at distances of 0.5 AU and decreases with increasing distances, with only a few waves detected per day in late September at ~1 AU. A more detailed analysis of triggered waveform snapshots shows the typical wave frequency at about 3 kHz and wave power about 5e-2 mV2/m2. The distribution of the relative phase between two components of the projected E-field in the Spacecraft Reference Frame (SRF) shows a mostly linear wave polarization. These waves are interpreted as strongly Doppler-shifted ion-acoustic waves, generated by solar wind ion beams and often accompany large-scale solar wind structures. A detailed analysis of the Doppler-shift using solar wind data from a Proton and Alpha particle Sensor (PAS), a part of Solar Wind Analyzer (SWA), is done for several examples.

How to cite: Pisa, D., Soucek, J., Santolik, O., Maksimovic, M., Horbury, T., and Owen, C. and the SolO RPW, MAG, and SWA instrument teams: Large amplitude ion-acoustic waves observed in the solar wind by the Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10023, https://doi.org/10.5194/egusphere-egu21-10023, 2021.

EGU21-10238 | vPICO presentations | ST1.3

Analysis of Alfvénic flows with Solar Orbiter: particle and magnetic observations down to kinetic scales.

Philippe Louarn, Andrei fedorov, alexis Rouillard, Benoit Lavraud, Vincent Génot, Christopher J Owen, Roberto Bruno, Lubomir Prech, Stephano Livi, Timothy S Horbury, and Milan Maksimovic and the SWA and MAG Solar Orbiter

The magnetic and velocity fluctuations of the solar wind may be strongly correlated. This characterizes the  ‘Alfvenic’ flows. Using the observations of the Proton Alfa sensor (PAS/SWA) and the magnetometer (MAG) onboard Solar Orbiter, we analyze a period of 100 hours of such alfvenic flows, at different scales. Several parameters of the turbulence are computed (V-B correlation, various spectral indexes, cross-helicity, residual energy). We explore how these parameters may vary with time and characterize different turbulent states of the flow. More specifically, using the unprecedented time resolution of PAS during burst mode, especially its capability to measure 3D distribution functions at time scale below the proton gyroperiod, we study the connection of the turbulence to the dissipation domain and analyze the fine structure of the distribution functions and their evolutions at sub-second scales. The goal is to investigate whether some characteristics of the distributions, as their more or less pronounced temperature anisotropy, may be related to the turbulence parameters and the degree of V-B correlation.

How to cite: Louarn, P., fedorov, A., Rouillard, A., Lavraud, B., Génot, V., Owen, C. J., Bruno, R., Prech, L., Livi, S., Horbury, T. S., and Maksimovic, M. and the SWA and MAG Solar Orbiter: Analysis of Alfvénic flows with Solar Orbiter: particle and magnetic observations down to kinetic scales., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10238, https://doi.org/10.5194/egusphere-egu21-10238, 2021.

EGU21-10630 | vPICO presentations | ST1.3

Solar Orbiter observations of solar wind current sheets and their deHoffman-Teller frames

Konrad Steinvall, Yuri Khotyaintsev, Giulia Cozzani, Andris Vaivads, Christopher Owen, Andrey Fedorov, and Philippe Louarn and the RPW Team, SWA Team, MAG Team

Solar wind current sheets have been extensively studied at 1 AU. The recent advent of Parker Solar Probe and Solar Orbiter (SolO) has enabled us to study these structures at a range of heliocentric distances.

We present SolO observations of current sheets in the solar wind at heliocentric distances between 0.55 and 0.85 AU, some of which show signatures of ongoing magnetic reconnection. We develop a method to find the deHoffman-Teller frame which minimizes the Y-component (the component tangential to the spacecraft orbit) of the electric field. Using the electric field measurements from RPW and magnetic field measurements from MAG, we use our method to determine the deHoffman-Teller frame of solar wind current sheets. The same method can also be used on the Alfvénic turbulence and structures found in the solar wind to obtain a measure of the solar wind velocity.

Our preliminary results show a good agreement between our modified deHoffmann-Teller analysis based on the single component E-field, and the conventional deHoffman-Teller analysis based on 3D plasma velocity measurements from PAS. This opens up the possibility to use the RPW and MAG data to obtain an estimate of the solar wind velocity when particle data is unavailable.

How to cite: Steinvall, K., Khotyaintsev, Y., Cozzani, G., Vaivads, A., Owen, C., Fedorov, A., and Louarn, P. and the RPW Team, SWA Team, MAG Team: Solar Orbiter observations of solar wind current sheets and their deHoffman-Teller frames, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10630, https://doi.org/10.5194/egusphere-egu21-10630, 2021.

EGU21-12941 | vPICO presentations | ST1.3

Ripples in the Heliospheric Current Sheet: Dependence on Latitude and Transient Outflows

Ronan Laker, Timothy Horbury, Lorenzo Matteini, Thomas Woolley, Lloyd Woodham, Julia Stawarz, Stuart Bale, Emma Davies, Jonathan Eastwood, Helen O'Brien, Vincent Evans, Virginia Angelini, Ingo Richter, Daniel Heyner, Chris Owen, Philippe Louarn, and Andrei Fedorov

The recent launches of Parker Solar Probe (PSP), Solar Orbiter (SO) and BepiColombo, along with several legacy spacecraft, have provided the opportunity to study the solar wind at multiple latitudes and distances from the Sun simultaneously. We take advantage of this unique spacecraft constellation, along with low solar activity between May and July 2020, to investigate how latitude affects the solar wind and Heliospheric Current Sheet (HCS) structure. We use ballistic mapping to compare polarity and solar wind velocity between several spacecraft, showing that fine scale ripples in the HCS can be resolved down to several degrees in longitude. We show that considering solar wind velocity is also useful when investigating the HCS structure, as it can reveal times when the spacecraft is within slow, dense streamer belt wind without changing magnetic polarity. We measured the local orientation of planar magnetic structures associated with HCS crossings, finding that these were broadly consistent with the shape of the HCS but at much steeper angles due to compression from stream interaction regions. We identified several transient magnetic clouds associated with HCS crossings, and have shown that these can disrupt the local HCS orientation up to four days after their passage, but did not significantly affect the position of the HCS. This work highlights that the heliosphere should always be treated as three-dimensional, especially at solar minimum, where a few degrees in latitude can create a considerable difference in solar wind conditions.

How to cite: Laker, R., Horbury, T., Matteini, L., Woolley, T., Woodham, L., Stawarz, J., Bale, S., Davies, E., Eastwood, J., O'Brien, H., Evans, V., Angelini, V., Richter, I., Heyner, D., Owen, C., Louarn, P., and Fedorov, A.: Ripples in the Heliospheric Current Sheet: Dependence on Latitude and Transient Outflows, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12941, https://doi.org/10.5194/egusphere-egu21-12941, 2021.

EGU21-11899 | vPICO presentations | ST1.3 | Highlight

The Radio and Plasma Waves (RPW) Instrument on Solar Orbiter: latest observations and results

Milan Maksimovic and the RPW, MAG, SWA and EPD teams

We will review the very latest observations and results obtained by the Radio and Plasma Waves (RPW) Instrument on the recently launched Solar Orbiter mission. RPW is designed to measure in-situ magnetic and electric fields and waves from 'DC' to a few hundreds of kHz. RPW is also capable of measuring solar radio emissions up to 16 MHz and link them to solar flares observed by the onboard remote sensing instruments. The latest results we will present concern a wide range of phenomena including: Langmuir and Whistler Waves, dust impacts, Solar Type III bursts and observations during the recently visited Venus environment.

How to cite: Maksimovic, M. and the RPW, MAG, SWA and EPD teams: The Radio and Plasma Waves (RPW) Instrument on Solar Orbiter: latest observations and results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11899, https://doi.org/10.5194/egusphere-egu21-11899, 2021.

EGU21-4482 | vPICO presentations | ST1.3

Interplanetary dust observations with the Solar Orbiter RPW instrument: a first year of data.

Arnaud Zaslavsky, Ingrid Mann, Stuart Bale, Andrzej Czechowski, Karine Issautier, Eric Lorfèvre, Milan Maksimovic, Nicole Meyer-Vernet, David Pisa, Kristina Rackovic-Babic, Jan Soucek, and Jakub Vaverka

Impacts of dust grains on spacecraft are known to produce typical impulsive signals in the voltage waveform recorded at the terminals of electric antennas. Such signals are, as could be expected, routinely detected by the radio and plasma waves (RPW) instrument aboard Solar Orbiter, therefore providing in-situ measurements of the interplanetary dust density along the spacecraft trajectory.

We present a statistical analysis of the first year and half of dust impact data recorded by Solar Orbiter RPW between 1 AU and 0.5 AU. We discuss the results in terms of constraints that can be put on beta-meteoroids and interstellar dust fluxes, and compare them to results obtained by STEREO at 1 AU and more recently by Parker Solar Probe at 0.5 AU.

How to cite: Zaslavsky, A., Mann, I., Bale, S., Czechowski, A., Issautier, K., Lorfèvre, E., Maksimovic, M., Meyer-Vernet, N., Pisa, D., Rackovic-Babic, K., Soucek, J., and Vaverka, J.: Interplanetary dust observations with the Solar Orbiter RPW instrument: a first year of data., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4482, https://doi.org/10.5194/egusphere-egu21-4482, 2021.

EGU21-12198 | vPICO presentations | ST1.3

Solar Orbiter/Radio and Plasma Wave observations during the first Venus flyby

Niklas J. T. Edberg, Lina Hadid, Milan Maksimovic, Stuart D. Bale, Thomas Chust, Yuri Khotyaintsev, Volodya Krasnoselskikh, Matthieu Kretzschmar, Eric Lorfèvre, Dirk Plettemeier, Jan Souček, Manfred Steller, Štěpán Štverák, Pavel Trávníček, Andris Vaivads, Antonio Vecchio, and Tim Horbury and the RPW team & MAG team

We present measurements from the Radio and Plasma Wave (RPW) instrument suite onboard the Solar Orbiter mission during the first Venus encounter. RPW consists of several units and is capable of measuring both the electric and magnetic field fluctuations with three electric antennas and a search-coil magnetometer: The Low Frequency Receiver (LFR) cover the range from DC up to 10kHz when measuring the electric and magnetic waveform and spectra; the Thermal Noise and High Frequency Receiver (TNR-HFR) determines the electric power spectra and magnetic power spectra from 4kHz-20MHz, and 4kHz to 500kHz, respectively, to determine properties of the electron population; the Time Domain Sampler (TDS) measures and digitizes onboard the electric and magnetic field waveforms from 100 Hz to 250 kHz. The BIAS subunit measures DC and LF electric fields as well as the spacecraft potential, which gives a high cadence measure of the local plasma density when calibrated to the low-cadence tracking of the plasma peak from the TNR. Solar Orbiter approached Venus from the induced magnetotail and had its closest approach at an altitude of 7500 km over the north pole of Venus on 27 Dec 2020. The RPW instruments observed a tail region that extended several 10’s of Venus radii downstream of the planet. The induced magnetosphere was characterized to be a highly dynamic environment as Solar Orbiter traversed the downstream tail and magnetosheath before it crossed the Bow Shock outbound at ~12:40 UT. Polarized whistler waves, high frequency electrostatic waves, narrow-banded emissions, possible electron double layers were observed. The fine structure of the bow shock could also be investigated in detail. Solar Orbiter could hence enhance the knowledge of the structure of the solar wind-Venus interaction.

How to cite: Edberg, N. J. T., Hadid, L., Maksimovic, M., Bale, S. D., Chust, T., Khotyaintsev, Y., Krasnoselskikh, V., Kretzschmar, M., Lorfèvre, E., Plettemeier, D., Souček, J., Steller, M., Štverák, Š., Trávníček, P., Vaivads, A., Vecchio, A., and Horbury, T. and the RPW team & MAG team: Solar Orbiter/Radio and Plasma Wave observations during the first Venus flyby, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12198, https://doi.org/10.5194/egusphere-egu21-12198, 2021.

EGU21-13801 | vPICO presentations | ST1.3

Impact induced electric field signals observed by the Solar Orbiter/RPW

Michiko Morooka, Yuri Khotyaintsev, Anders Eriksson, Niklas Edberg, Erik Johansson, Milan Maksimovic, Stuart Bale, Thomas Chust, Volodya Krasnoselskikh, Matthieu Kretzschmar, Eric Lorfèvre, Dirk Plettemeier, Jan Souček, Manfred Steller, Štěpán Štverák, Pavel Trávníček, Andris Vaivads, and Antonio Vecchio

A large-amplitude impact-induced like electric field signal is often observed by the Radio and Plasma Wave (RPW) Instrument onboard Solar Orbiter. The signal has a sharp increase followed by an exponential decay, typically observed when spacecraft experiences a dust impact. The amplitude can reach several V/m. The impact dust size can be estimated from the electric field amplitude and is similar to the characteristic dust size near the sun expected from the zodiacal-light observations. On the other hand, the signal's decay time is the order of second, unusually long compared to the dust impact signals previously reported by the other spacecraft. We will show the characteristics of these signals and discuss the origin.

How to cite: Morooka, M., Khotyaintsev, Y., Eriksson, A., Edberg, N., Johansson, E., Maksimovic, M., Bale, S., Chust, T., Krasnoselskikh, V., Kretzschmar, M., Lorfèvre, E., Plettemeier, D., Souček, J., Steller, M., Štverák, Š., Trávníček, P., Vaivads, A., and Vecchio, A.: Impact induced electric field signals observed by the Solar Orbiter/RPW, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13801, https://doi.org/10.5194/egusphere-egu21-13801, 2021.

EGU21-15195 | vPICO presentations | ST1.3

Whistler waves observed by Solar Orbiter during its first orbit

Matthieu Kretschmar, Thomas Chust, Daniel Graham, Volodya Krasnosekskikh, Lucas Colomban, Milan Maksimovic, Timothy Horbury, Christofer Owen, and Philippe Louarn

Plasma waves can play an important role in the evolution of the solar wind and the particle velocity distribution functions in particular. We analyzed the electromagnetic waves observed above a few Hz by the Radio Plasma Waves (RPW) instrument suite onboard Solar Orbiter, during its first orbit, which covered a distance from the Sun between 1 AU and 0.5 AU.  We identified the majority of the detected waves as whistler waves with frequency around  0.1 f_ce and right handed circular polarisation. We found these waves to be mostly aligned or anti aligned with the ambient magnetic field, and rarely oblique. We also present and discuss their direction of propagation and the variation of the waves' properties with heliocentric distance.

How to cite: Kretschmar, M., Chust, T., Graham, D., Krasnosekskikh, V., Colomban, L., Maksimovic, M., Horbury, T., Owen, C., and Louarn, P.: Whistler waves observed by Solar Orbiter during its first orbit, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15195, https://doi.org/10.5194/egusphere-egu21-15195, 2021.

EGU21-15746 | vPICO presentations | ST1.3

Using Compressibility and Electric Field to Characterize Circularly-Polarized Waves Near the Proton Cyclotron Frequency Observed by Solar Orbiter

Yuri Khotyaintsev, Daniel B Graham, Konrad Steinvall, Andris Vaivads, Milan Maksimovic, Niklas J. T. Edberg, Erik P.G. Johansson, and Anders I. Eriksson and the RPW, MAG and SWA Teams

We report Solar Orbiter observations of electromagnetic waves near the proton cyclotron frequency during the first perihelion. The waves have polarization close to circular and have wave vectors closely aligned with the background magnetic field. Such waves are potentially important for heating of the solar wind as their frequency and polarization allows effective energy exchange with solar wind protons. The Radio and Plasma Waves (RPW) instrument provides a high-cadence measurement of plasma density and electric field which we use together with the magnetic field measured by MAG to characterize these waves. In particular we compute the compressibility and the phase between the density fluctuations and the parallel component of the magnetic field, and show that these have a distinct behavior for the waves compared to the Alfvénic turbulence. We compare the observations to multi-fluid plasma dispersion and identify the waves modes corresponding to the observed waves. We discuss the importance of the waves for solar wind heating.

How to cite: Khotyaintsev, Y., Graham, D. B., Steinvall, K., Vaivads, A., Maksimovic, M., Edberg, N. J. T., Johansson, E. P. G., and Eriksson, A. I. and the RPW, MAG and SWA Teams: Using Compressibility and Electric Field to Characterize Circularly-Polarized Waves Near the Proton Cyclotron Frequency Observed by Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15746, https://doi.org/10.5194/egusphere-egu21-15746, 2021.

EGU21-15860 | vPICO presentations | ST1.3

Thin current sheets and the associated wave activity observed by Solar Orbiter

Daniel Graham, Yuri Khotyaintsev, Konrad Steinvall, Andris Vaivads, Milan Maksimovic, Niklas Edberg, Erik Johansson, Anders Eriksson, Matthieu Kretzschmar, and Thomas Chust and the RPW, MAG and SWA Solar Orbiter teams

Thin current sheets are routinely observed in the solar wind. Here we report observations of thin current sheets and the associated plasma waves using the Solar Orbiter spacecraft. The Radio and Plasma Waves (RPW) instrument provides high-resolution measurements of the electric field, number density perturbations, and magnetic field fluctuations, which we use to identify and characterise the observed waves, while the magnetic field provided by the MAG instrument is used to characterise the current sheets. We discuss the role of current sheets in the generation of the observed waves and the effects of the waves on the current sheets. 

How to cite: Graham, D., Khotyaintsev, Y., Steinvall, K., Vaivads, A., Maksimovic, M., Edberg, N., Johansson, E., Eriksson, A., Kretzschmar, M., and Chust, T. and the RPW, MAG and SWA Solar Orbiter teams: Thin current sheets and the associated wave activity observed by Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15860, https://doi.org/10.5194/egusphere-egu21-15860, 2021.

EGU21-16006 | vPICO presentations | ST1.3

Search for oblique Whistler waves using solar orbiter data

Lucas Colomban, Matthieu Kretzschmar, Volodya Krasnoselskikh, Laura Bercic, Chris Owen, and Milan Maksimovic

Whistler waves are thought to play an important role on the evolution of the electron distribution function as a function of distance. In particular, oblique whistler waves may diffuse the Strahl electrons  into the halo population.  Using AC magnetic field from the RPW/SCM (search coil magnetometer) of Solar Orbiter, we search for the presence of oblique Whistler waves in the frequency range between 3 Hz and 128 Hz .  We perform a minimum variance analysis of the SCM data in combination with the MAG (magnetometer) data to determine the inclination of the waves with respect to the ambiant magnetic field. As the emphasis is placed on the search for oblique whistler, we also analyze the RPW electric field data and the evolution of the electron distribution function during these Whistler events.

How to cite: Colomban, L., Kretzschmar, M., Krasnoselskikh, V., Bercic, L., Owen, C., and Maksimovic, M.: Search for oblique Whistler waves using solar orbiter data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16006, https://doi.org/10.5194/egusphere-egu21-16006, 2021.

The solar coronal plasma which escapes the Sun’s gravity and expands through our solar system is called the solar wind. It consists mainly of electrons and protons, carries the Sun’s magnetic field and, at most heliocentric distances, remains weakly-collisional. Due to their small mass, the solar wind electrons have much higher thermal velocity than their positively charged counterpart, and play an important role in the solar wind energetics by carrying the heat flux away from the Sun. Their velocity distribution functions (VDFs) are complex, usually modeled by three components. While the majority of electrons belong to the low-energetic thermal Maxwellian core population, some reach higher velocities, forming either the magnetic field aligned strahl population, or an isotropic high-energy halo population. This shape of the electron VDF is a product of the interplay between
Coulomb collisions, adiabatic expansion, global and local electro-magnetic fields and turbulence.
In this work we focus on the effects of local electro-magnetic wave activity on electron VDF, taking advantage of the early measurements made by the novel heliospheric Solar Orbiter mission. The high- cadence sampling of 2-dimensional electron VDFs by the electrostatic analyser SWA-EAS, together with the EM wave data collected by the seach-coil magnetometers and electric-field antennas, part of

the RPW instrument suit, allow a direct investigation of the wave-particle energy and momentum exchange. We present the evolution of the electron VDF in the presence of quasi-parallel and oblique whistler waves, believed to be responsible for scattering the strahl and creating the halo population (Verscharen et al. 2019; Micera et al. 2020).

How to cite: Bercic, L. and the et al.: Evolution of the electron velocity distribution under the presence of whistler waves in the solar wind (high-cadence Solar Orbiter observations), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16455, https://doi.org/10.5194/egusphere-egu21-16455, 2021.

EGU21-5061 | vPICO presentations | ST1.3

Transient small-scale brightenings in the quiet Sun corona: a model for "campfires" observed with Solar Orbiter

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

Recent observations by the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter have revealed prevalent small-scale transient brightenings in the quiet solar corona termed campfires. To understand the generation mechanism of these coronal brightenings, we constructed a self- consistent and time-dependent quiet-Sun model extending from the upper convection zone to the lower corona using a realistic 3D radiation MHD simulation. From the model we have synthesized the coronal emission in the EUI 174 Å passband. We identified several transient coronal brightenings similar to those in EUI observations. The size and lifetime of these coronal brightenings are 2–4 Mm and ∼2 min, respectively. These brightenings are located at a height of 2–4 Mm above the photosphere, and the surrounding plasma is often heated above 1 MK. These findings are consistent with the observational characterisation of the campfires. Through a comparison of the magnetic field structures before and after the occurrence of brightenings, we conclude that these coronal brightenings are generated by component magnetic reconnection between interacting bundles of field lines or the relaxation of highly twisted flux ropes. Occurring in the coronal part of the atmosphere, these events show no measurable signature in the photosphere. These transient coronal brightenings may play an important role in heating of the local coronal plasma.

How to cite: Chen, Y., Przybylski, D., Peter, H., and Tian, H.: Transient small-scale brightenings in the quiet Sun corona: a model for "campfires" observed with Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5061, https://doi.org/10.5194/egusphere-egu21-5061, 2021.

EGU21-14801 | vPICO presentations | ST1.3

First results from combined EUI and SPICE observations of Lyman lines of Hydrogen and He II

Luca Teriaca and the EUI and SPICE Teams

The Solar Orbiter spacecraft carries a powerful set of remote sensing instruments that allow studying the solar atmosphere with unprecedented diagnostic capabilities. Many such diagnostics require the simultaneous usage of more than one instrument. One example of that is the capability, for the first time, to obtain (near) simultaneous spatially resolved observations of the emission from the first three lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact, the SPectral Imaging of the Coronal Environment (SPICE) spectrometer can observe the Lyman beta and gamma lines in its long wavelength (SPICE-LW) channel, the High Resolution Lyman Alpha (HRILYA) telescope of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take images dominated by the Lyman alpha line of ionized Helium at 30.4 nm (FSI-304). Being hydrogen and helium the main components of our star, these very bright transitions play an important role in the energy budget of the outer atmosphere via radiative losses and the measurement of their profiles and radiance ratios is a fundamental constraint to any comprehensive modelization effort of the upper solar chromosphere and transition region. Additionally, monitoring their average ratios can serve as a check out for the relative radiometric performance of the two instruments throughout the mission.

Although the engineering data acquired so far are far from ideal in terms of time simultaneity (often only within about 1 h) and line coverage (often only Lyman beta was acquired by SPICE and not always near simultaneous images from all three telescopes are available) the analysis we present here still offers a great opportunity to have a first look at the potential of this diagnostic from the two instruments.

In fact, we have identified a series of datasets obtained at disk center and at various positions at the solar limb that allow studying the Lyman alpha to beta radiance ratio and their relation to He II 30.4 as a function of the position on the Sun (disk center versus limb and quiet Sun versus coronal holes).

How to cite: Teriaca, L. and the EUI and SPICE Teams: First results from combined EUI and SPICE observations of Lyman lines of Hydrogen and He II, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14801, https://doi.org/10.5194/egusphere-egu21-14801, 2021.

EGU21-5577 | vPICO presentations | ST1.3

First Results From SPICE EUV Spectrometer on Solar Orbiter

Andrzej Fludra and the SPICE Team

SPICE (Spectral Imaging of Coronal Environment) is an EUV imaging spectrometer onboard Solar Orbiter. SPICE observes the Sun in two wavelength bands: 69.6-79.4 nm and 96.6-105.1 nm and is capable of recording full spectra in these bands with exposures as short as 1s. SPICE can measure spectra from the disk and low corona, and records all spectral lines simultaneously, using one of three narrow slits: 2”x11’, 4’’x11’, 6’’x11’, or a wide slit 30’’x14’. The primary mirror can be scanned in a direction perpendicular to the slit, allowing raster images of up to 16’ in size.

The first SPICE data were taken during the instrument commissioning carried out by the RAL Space team between 2020 April 21 and 2020 June 14, and at the first Solar Orbiter perihelion at 0.52AU between June 16-21.  We give examples of full spectra from the quiet Sun near disk centre and provide a list of key spectral lines from neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur and magnesium. These lines cover the temperature range between 10,000 K and 1 million K (10MK in flares), providing slices of the Sun’s atmosphere in narrow temperature intervals. We show examples of raster images in several strong lines, obtained with different slits and a range of exposure times between 5s and 180s.

We have found several unusually bright, compact structures (named “beacons”) in the quiet Sun network, with extreme intensities up to 22 times greater than the average intensity across the image. The lifetimes of these sources are longer than 1 hour. We will derive plasma velocities in the beacon area, and co-align the SPICE rasters with the SDO/AIA 304 and 171 images and the HMI magnetic field to better understand the origin and properties of beacons.

We also show the first above-limb measurements with SPICE in Mg IX, Ne VIII and O VI lines, as obtained when the spacecraft pointed at the limb. Maps of Mg/Ne abundance ratios on disk can be derived and compared with in situ measurements to help confirm the magnetic connection between the spacecraft location and the Sun’s surface, and locate the sources of the solar wind.

How to cite: Fludra, A. and the SPICE Team: First Results From SPICE EUV Spectrometer on Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5577, https://doi.org/10.5194/egusphere-egu21-5577, 2021.

EGU21-15555 | vPICO presentations | ST1.3

First data for abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter

Natalia Zambrana Prado, Éric Buchlin, and Hardi Peter and the SPICE consortium team

Linking solar activity on the surface and in the corona to the heliosphere is one of Solar Orbiter’s main goals. Its EUV spectrometer SPICE (SPectral Imaging of the Coronal Environment) will provide relative abundance measurements which will be key in this quest, as different structures on the Sun have different abundances as a consequence of the FIP (First Ionization Potential) effect. From the 16th to the 22nd of November 2020,  the Solar Orbiter remote sensing checkout window STP-122 was carried out. During this period of observations, SPICE was lucky to catch a small AR in its field of view. We carried out abundance specific observations in order to provide relative FIP bias measurements with SPICE. Furthermore, data from other types of observations carried out during that same week allow us to identify the spectral lines that could be used for abundance diagnostics. We take the SPICE instrument characteristics into account to give recommendations regarding the types of studies to carry out to obtain such abundance measurements.

How to cite: Zambrana Prado, N., Buchlin, É., and Peter, H. and the SPICE consortium team: First data for abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15555, https://doi.org/10.5194/egusphere-egu21-15555, 2021.

EGU21-4390 | vPICO presentations | ST1.3

First results of the STIX hard X-ray telescope onboard Solar Orbiter

Andrea Francesco Battaglia, Jonas Saqri, Ewan Dickson, Hualin Xiao, Astrid Veronig, Alexander Warmuth, Marina Battaglia, and Säm Krucker and the STIX Team

With the launch and commissioning of Solar Orbiter, the Spectrometer/Telescope for Imaging X-rays (STIX) is the latest hard X-ray telescope to study solar flares over a large range of flare sizes. STIX uses hard X-ray imaging spectroscopy in the range from 4 to 150 keV to diagnose the hottest temperature of solar flare plasma and the related nonthermal accelerated electrons. The unique orbit away from the Earth-Sun line in combination with the opportunity of joint observations with other Solar Orbiter instruments, STIX will provide new inputs into understanding the magnetic energy release and particle acceleration in solar flares. Commissioning observations showed that STIX is working as designed and therefore we report on the first solar microflare observations recorded on June 2020, when the spacecraft was at 0.52 AU from the Sun. STIX’s measurements are compared with Earth-orbiting observatories, such as GOES and SDO/AIA, for which we investigate and interpret the different temporal evolution. The detected early peak of the STIX profiles relative to GOES is due either by nonthermal X-ray emission of accelerated particles interacting with the dense chromosphere or the higher sensitivity of STIX toward hotter plasma.

How to cite: Battaglia, A. F., Saqri, J., Dickson, E., Xiao, H., Veronig, A., Warmuth, A., Battaglia, M., and Krucker, S. and the STIX Team: First results of the STIX hard X-ray telescope onboard Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4390, https://doi.org/10.5194/egusphere-egu21-4390, 2021.

EGU21-16460 | vPICO presentations | ST1.3

The First STIX Coarse Flare Locations

Ewan Dickson and the STIX team

The Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter (Krucker et al., 2020) uses an indirect imaging system to measure flare location, size and morphology. Pairs of tungsten grids create Moiré fringes on its coarsely pixelated CdTe detectors. Images are then reconstructed on the ground, using sophisticated imaging algorithms, after the data containing the counts in each pixel for 30 imaging detectors has been download. 

STIX therefore uses a dedicated sub-collimator to estimate a rough (within a few arcminutes), but unambiguous, flare location on board in near real time. The Coarse Flare Locator (CFL) consists of a single grid with a specific pattern which selectively illuminates pixels of a dedicated detector based on the source location. The correlation between the counts in the pixels of this detector, combined with sums of counts from the other detectors, and a look up table of pre-caculated expectations allows the location to be estimated promptly, within the constraints of on board processing. 

Using the downloaded measured counts in each pixel the coarse flare location can also be reconstructed on the ground. This allows for more sophisticated algorithms which require greater computational power than is available on board; greater flexibility as to which time and energy intervals are combined; and more careful background subtraction possible. 

The first estimates of STIX flare locations calculated using the STIX Ground Processing Software (GSW) from data taken during commissioning and subsequent Remote Sensing Checkout Windows are presented here. Comparisons are made to the expected active region and source locations, using data from several other instruments. 

References 

Krucker, S et al. The Spectrometer/Telescope for Imaging X-rays (STIX). Astronomy and Astrophysics, v. 642, Oct. 2020. DOI: 10.1051/0004-6361/201937362.

How to cite: Dickson, E. and the STIX team: The First STIX Coarse Flare Locations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16460, https://doi.org/10.5194/egusphere-egu21-16460, 2021.

EGU21-9422 | vPICO presentations | ST1.3

Early results for the STIX image reconstruction problem: imaging from visibility amplitudes

michele piana, paolo massa, emma perracchione, andrea francesco battaglia, federico benvenuto, anna maria massone, gordon hurford, and sam krucker

The Spectrometer/Telescope for Imaging X-rays (STIX) is the instrument of the Solar Orbiter mission conceived for the observation of the hard X-ray flaring emission, with the objective of providing insights on the diagnosis of thermal and non-thermal accelerated electrons at the Sun. The STIX imaging system is composed of 30 pairs of tungsten grids, each one placed in front of a four-pixel detector, and produces as many Fourier components of the angular distribution of the flaring source, via Moiré pattern modulation. Therefore, the data recorded by STIX, named visibilities, can be interpreted as a sparse sampling of the Fourier transform of the X-ray signal and the corresponding image reconstruction problem requires the inversion of the Fourier transform from limited data, usually addressed with regularization techniques. Since the current calibration status of STIX measurements still prevents the use of visibility phases for imaging purposes, here we propose a parameter identification process based on forward fitting  just the amplitude of the experimental visibilities. Specifically, we have parameterized the flaring source by means of pre-assigned source shapes (e.g., circular and elliptical bi-variate Gaussian functions), and we relied on several approaches to non-linear optimization in order to estimating the shape parameters. In particular, we have implemented a forward-fit method based on deterministic chi-squared minimization, a stochastic optimization algorithm and a deep neural approach based on ensemble learning, also equipping them with an ad hoc statistical technique for uncertainty quantification. The performances of the three approaches are compared in the case of both microflares and M class events recorded by STIX during its commissioning phase and the validation of results is realized also exploiting the EUV information provided by the Atmospheric Imaging Assembly within the Solar Dynamics Observatory.

How to cite: piana, M., massa, P., perracchione, E., battaglia, A. F., benvenuto, F., massone, A. M., hurford, G., and krucker, S.: Early results for the STIX image reconstruction problem: imaging from visibility amplitudes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9422, https://doi.org/10.5194/egusphere-egu21-9422, 2021.

EGU21-7966 | vPICO presentations | ST1.3

Plasma Diagnostics of Microflares observed by STIX and AIA

Jonas Saqri, Astrid Veronig, Ewan Dickson, Säm Krucker, Andrea Francesco Battaglia, Marina Battaglia, Hualin Xiao, Alexander Warmuth, and the STIX Team

Solar flares are generally thought to be the impulsive release of magnetic energy giving rise to a wide range of solar phenomena that influence the heliosphere and in some cases even conditions of earth. Part of this liberated energy is used for particle acceleration and to heat up the solar plasma. The Spectrometer/Telescope for Imaging X-rays (STIX) instrument onboard the Solar Orbiter mission launched on February 10th 2020 promises advances in the study of solar flares of various sizes. It is capable of measuring X-ray spectra from 4 to 150 keV with 1 keV resolution binned into 32 energy bins before downlinking. With this energy range and sensitivity, STIX is capable of sampling thermal plasma with temperatures of≳10 MK, and to diagnose the nonthermal bremsstrahlung emission of flare-accelerated electrons. During the spacecraft commissioning phase in the first half of the year 2020, STIX observed 68 microflares. Of this set, 26 events could clearly be identified in at least two energy channels, all of which originated in an active region that was also visible from earth. These events provided a great opportunity to combine the STIX observations with the multi-band EUV imagery from the Atmospheric Imaging Assembly (AIA) instrument on board the earth orbiting Solar Dynamics Observatory (SDO). For the microflares that could be identified in two STIX science energy bands, it was possible to derive the temperature and emission measure (EM) of the flaring plasma assuming an isothermal source. For larger events where more detailed spectra could be derived, a more accurate analysis was performed by fitting the spectra assuming various thermal and nonthermal sources. These results are compared to the diagnostics derived from AIA images. To this aim, the Differential EmissionMeasure (DEM) was reconstructed from AIA observations to infer plasma temperatures and EM in the flaring regions. Combined with the the relative timing between the emission seen by STIX and AIA, this allows us to get deeper insight into the flare energy release and transport processes.

How to cite: Saqri, J., Veronig, A., Dickson, E., Krucker, S., Battaglia, A. F., Battaglia, M., Xiao, H., Warmuth, A., and STIX Team, T.: Plasma Diagnostics of Microflares observed by STIX and AIA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7966, https://doi.org/10.5194/egusphere-egu21-7966, 2021.

ST1.4 – Pioneering exploration of the solar corona and near-Sun environment – Latest results from Parker Solar Probe

EGU21-13400 | vPICO presentations | ST1.4

Theory and observations of switchbacks’ evolution in the solar wind

Anna Tenerani, Marco Velli, and Lorenzo Matteini

Alfvénic fluctuations represent the dominant contributions to turbulent fluctuations in the solar wind, especially, but not limited to, the fastest streams with velocity of the order of 600-700 km/s. Alfvénic fluctuations can contribute to solar wind heating and acceleration via wave pressure and turbulent heating. Observations show that such fluctuations are characterized by a nearly constant magnetic field amplitude, a condition which remains largely to be understood and that may be an indication of how fluctuations evolve and relax in the expanding solar wind. Interestingly, measurements from Parker Solar Probe have shown the ubiquitous and persistent presence of the so-called switchbacks. These are magnetic field lines which are strongly perturbed to the point that they produce local inversions of the radial magnetic field. The corresponding signature of switchbacks in the velocity field is that of local enhancements in the radial speed (or jets) that display the typical velocity-magnetic field correlation that characterizes Alfvén waves propagating away from the Sun. While there is not yet a general consensus on what is the origin of switchbacks and their connection to coronal activity, a first necessary step to answer these important questions is to understand how they evolve and how long they can persist in the solar wind. Here we investigate the evolution of switchbacks. We address how their evolution is affected by parametric instabilities and the possible role of expansion, by comparing models with the observed radial evolution of the fluctuations’ amplitude. We finally discuss what are the implications of our results for models of switchback generation and related open questions.

How to cite: Tenerani, A., Velli, M., and Matteini, L.: Theory and observations of switchbacks’ evolution in the solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13400, https://doi.org/10.5194/egusphere-egu21-13400, 2021.

EGU21-2865 | vPICO presentations | ST1.4

Magnetic Reconnection in the Corona as a Source of Switchbacks in the Solar Wind

James Drake, Oleksiy Agapitov, Marc Swisdak, Sam Badman, Stuart Bale, Timothy Horbury, Justin Kasper, Robert MacDowal, Forrest Mozer, Tai Phan, Marc Pulupa, Adam Szabo, and Marco Velli

The observations from the Parker Solar Probe during the first
perihelion revealed large numbers of local reversals in the radial
component of the magnetic field with associated velocity spikes. Since
the spacecraft was magnetically connected to a coronal hole during the
closest approach to the sun, one possible source of these spikes is
magnetic reconnection between the open field lines in the coronal hole
and an adjacent region of closed flux. Reconnection in a low beta
environment characteristic of the corona is expected to be bursty
rather than steady and is therefore capable of producing large numbers
of magnetic flux ropes with local reversals of the radial magnetic
field that can propagate outward large radial distances from the
sun. Flux ropes with a strong guide field produce signatures
consistent with the PSP observations. We have carried out simulations
of "interchange" reconnection in the corona and have explored the
local structure of flux ropes embedded within the expanding solar
wind. We have first established that traditional interchange
reconnection cannot produce the switchbacks since bent field lines
generated in the corona quickly straighten. The simulations have been
extended to the regime dominated by the production of multiple flux
ropes and we have established that flux ropes are injected into the
local solar wind. Local simulations of reconnection are also being
carried out to explore the structure of flux ropes embedded in the
solar wind for comparison with observations. Evidence is presented
that flux rope merging may be ongoing and might lead to the high
aspect ratio of the switchback structures measured in the solar wind.

How to cite: Drake, J., Agapitov, O., Swisdak, M., Badman, S., Bale, S., Horbury, T., Kasper, J., MacDowal, R., Mozer, F., Phan, T., Pulupa, M., Szabo, A., and Velli, M.: Magnetic Reconnection in the Corona as a Source of Switchbacks in the Solar Wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2865, https://doi.org/10.5194/egusphere-egu21-2865, 2021.

EGU21-15707 | vPICO presentations | ST1.4

Why switchbacks may be related to solar granulation 

Naïs Fargette, Benoit Lavraud, Alexis Rouillard, Victor Réville, Tai Phan, Stuart D. Bale, Thierry Dudok De Wit, Clara Froment, Justin Kasper, Jasper S. Halekas, Philippe Louarn, Anthony W. Case, Kelly E. Korreck, Davin E. Larson, David Malaspina, Marc Pulupa, Michael L. Stevens, Phyllis L. Whittlesey, and Matthieu Berthomier

Parker Solar Probe data below 0.3 AU have revealed a near-Sun magnetic field dominated by Alfvénic structures that display back and forth reversals of the radial magnetic field. They are called magnetic switchbacks, they display no electron strahl variation consistent with magnetic field foldings within the same magnetic sector, and are associated with velocity spikes during an otherwise calmer background. They are thought to originate either at the photosphere through magnetic reconnection processes, or higher up in the corona and solar wind through turbulent processes.

In this work, we analyze the spatial and temporal characteristic scales of these magnetic switchbacks. We define switchbacks as a deviation from the parker spiral direction and detect them automatically through perihelia encounters 1 to 6. We analyze the solid angle between the magnetic field and the parker spiral both over time and space. We perform a fast Fourier transformation to the obtained angle and find a periodical spatial variation with scales consistent with solar granulation. This suggests that switchbacks form near the photosphere and may be caused, or at least modulated, by solar convection.

How to cite: Fargette, N., Lavraud, B., Rouillard, A., Réville, V., Phan, T., Bale, S. D., Dudok De Wit, T., Froment, C., Kasper, J., Halekas, J. S., Louarn, P., Case, A. W., Korreck, K. E., Larson, D. E., Malaspina, D., Pulupa, M., Stevens, M. L., Whittlesey, P. L., and Berthomier, M.: Why switchbacks may be related to solar granulation , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15707, https://doi.org/10.5194/egusphere-egu21-15707, 2021.

EGU21-7879 | vPICO presentations | ST1.4

Discontinuity analysis and evolution of magnetic switchbacks

Mojtaba Akhavan-Tafti, Justin Kasper, Jia Huang, and Stuart Bale

Magnetic switchbacks are Alfvénic structures characterized as intervals of intermittent reversals in the radial componentof magnetic field. Switchbacks comprise of magnetic spikes preceded/succeeded by quiet, pristine solar wind. Determining switch-back generation and evolution mechanisms will further our understanding of the global circulation and transportation of Sun’s openmagnetic flux. Here, we investigate switchback transition regions using measurements from fields and plasma suites aboard the Parker SolarProbe (PSP). Minimum variance analysis (MVA) is applied on switchback transition region magnetic signatures. Discontinuity analysesare performed on 273 switchback transition regions with robust MVA solutions. Our results indicate that switchbacks are rotational discontinuities (RD) in 214 (or 78%) of the cases. 21% of the switchbacktransition regions are categorized as "either" discontinuity (ED), defined as small relative changes in both magnitude and the normalcomponent of magnetic field. RD-to-ED event count is found to reduce with increasing distance from the Sun. On average, plasmabeta falls by −28% across RD-type switchback transition regions and magnetic shear angle is 60 [deg], therefore making switchbacktransition regions theoretically favorable to local magnetic reconnection. The evolution of switchbacks away from the Sun may involve increasing mass flux across RD-type switchback transition regions. The evolution mechanism(s) remain to be discovered. Our results indicate negligible magnetic curvature across switchback transition regions which may inhibit local magnetic reconnection.

How to cite: Akhavan-Tafti, M., Kasper, J., Huang, J., and Bale, S.: Discontinuity analysis and evolution of magnetic switchbacks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7879, https://doi.org/10.5194/egusphere-egu21-7879, 2021.

EGU21-6686 | vPICO presentations | ST1.4

Multiscale Solar Wind Turbulence Properties inside and near Switchbacks measured by Parker Solar Probe

Mihailo Martinović, Kristopher Klein, Jia Huang, Benjamin Chandran, Justin Kasper, Emily Lichko, Trevor Bowen, Christopher Chen, Lorenzo Matteini, Michael Stevens, Anthony Case, and Stuart Bale

Parker Solar Probe (PSP) routinely observes magnetic field deflections in the solar wind at distances less than 0.3 au from the Sun. These deflections are related to structures commonly called 'switchbacks' (SBs), whose origins and characteristic properties are currently debated. Here, we use a database of visually selected SB intervals - and regions of solar wind plasma measured just before and after each SB - to examine plasma parameters, turbulent spectra from inertial to dissipation scales, and intermittency effects in these intervals. We find that many features, such as perpendicular stochastic heating rates and turbulence spectral slopes are fairly similar inside and outside of SBs. However, important kinetic properties, such as the characteristic break scale between the inertial to dissipation ranges differ inside and outside these intervals, as does the level of intermittency, which is notably enhanced inside SBs and in their close proximity, most likely due to magnetic field and velocity shears observed at the edges. We conclude that the plasma inside and outside of a SB, in most of the observed cases, belongs to the same stream, and that the evolution of these structures is most likely regulated by kinetic processes, which dominate small scale structures at the SB edges. 

How to cite: Martinović, M., Klein, K., Huang, J., Chandran, B., Kasper, J., Lichko, E., Bowen, T., Chen, C., Matteini, L., Stevens, M., Case, A., and Bale, S.: Multiscale Solar Wind Turbulence Properties inside and near Switchbacks measured by Parker Solar Probe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6686, https://doi.org/10.5194/egusphere-egu21-6686, 2021.

EGU21-15180 | vPICO presentations | ST1.4

Decomposition of the switchback boundary on MHD wave modes.

Vladimir Krasnoselskikh, Andrea Larosa, Thierry Dudok de Wit, Oleksiy Agapitov, Clara Froment, Matthieu Kretzschmar, Vamsee Jagarlamudi, Marco Velli, Stuart D. Bale, Keith Goetz, Peter Harvey, Justin Kasper, Kelly Korreck, Davin Larson, Robert MacDowall, David Malaspina, Forrest Mozer, Marc Pulupa, Claire Reveillet, and Michael Stevens

Switchback boundaries separate two plasmas moving with different velocities, that may have different temperatures and densities and typically manifest sharp magnetic field deflections through the boundary. They may be analyzed similarly to MHD discontinuities. The first step of their characterization consists of analysis in terms of MHD discontinuities. Such an analysis was performed by Larosa et al., (2021) who has found that 32% of them may be attributed to rotational discontinuities, 17% to tangential, about 42% to the group of discontinuities that are difficult to unambiguously define whether they are tangential or rotational, and 9% that do not belong to any of these two groups. We describe and apply hereafter for two events another approach for the characterization of the boundaries based on classification of the general type discontinuity in MHD approximation. It is based on the problem of the decay of the general type of discontinuity. It is well known [Kulikovsky and Lyubimov, 1962, Gogosov, 1959} that general type MHD discontinuity decays on 7 separate discontinuities belonging to different types of MHD waves, namely, entropic wave, two slow mode waves, two Alfvenic waves, and two fast mode waves. Entropic wave is standing in the reference frame of the discontinuity; other wave modes are supposed to run in the opposite directions from the initial discontinuity with their characteristic velocities. Making use of plasma parameters from two sides of the boundary one can evaluate the fraction of each wave mode present in the discontinuity. We apply this method to two boundary crossings. This repartition of the discontinuity allows characterizing the deviation from Alfvenicity quantitatively.

References

Larosa, A., et al., A&A, 2021, (accepted)

Kulikovsky, Lyubimov, Magnetohydrodynamics, (1962)

Gogosov, V.V., Decay of the MHD discontinuity, (1959)

How to cite: Krasnoselskikh, V., Larosa, A., Dudok de Wit, T., Agapitov, O., Froment, C., Kretzschmar, M., Jagarlamudi, V., Velli, M., Bale, S. D., Goetz, K., Harvey, P., Kasper, J., Korreck, K., Larson, D., MacDowall, R., Malaspina, D., Mozer, F., Pulupa, M., Reveillet, C., and Stevens, M.: Decomposition of the switchback boundary on MHD wave modes., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15180, https://doi.org/10.5194/egusphere-egu21-15180, 2021.

EGU21-13552 | vPICO presentations | ST1.4

Solar wind speed and rotational shear at coronal hole boundaries, impacts on magnetic field inversions

Rui Pinto, Nicolas Poirier, Athanasis Kouloumvakos, Alexis Rouillard, Léa Griton, Naïs Fargette, Rungployphan Kieokaew, Benoît Lavraud, and Allan Sacha Brun

The solar wind is frequently perturbed by transient structures such as magnetic folds, jets, waves and flux-ropes that propagate rapidly away from the Sun over a large range of heliocentric distances. Parker Solar Probe has revealed that rotations of the magnetic field vector occur repeatedly at small heliocentric distances, on regions that also display surprisingly large solar wind rotation rates. Sun-to-spacecraft connectivity analysis shows that a large fraction of the solar wind flows probed so far by Parker Solar Probe were formed and accelerated in the vicinity of coronal hole boundaries.
We show by means of of global MHD simulations that coronal rotation is highly structured in proximity to those boundary regions (in agreement with preceding SoHO/UVCS observations), and that enhanced poloidal and toroidal flow shear and magnetic field gradients also develop there. We identified regions of the solar corona for which solar wind speed and rotational shear are significant, that can be associated with field-aligned and/or transverse vorticity, and that can be favourable to the development of magnetic deflections. Some of these wind flow shears are driven through large radial extensions, being noticeable tens of solar radii away from the surface, and therefore have a potential impact on the propagation of such magnetic perturbations across extended heights in the solar wind. We conclude that these regions of persistent shears are undoubtedly sources of complex solar wind structures, and suggest that they can trigger instabilities capable of creating magnetic field reversals detected in-situ in the heliosphere.
Our simulations furthermore indicate that the spatial structure of the solar wind shear will become more complex as the solar cycle progresses, with strong and extended shears appearing at heliographic latitudes that will be probed by Solar Orbiter in the near future.

How to cite: Pinto, R., Poirier, N., Kouloumvakos, A., Rouillard, A., Griton, L., Fargette, N., Kieokaew, R., Lavraud, B., and Brun, A. S.: Solar wind speed and rotational shear at coronal hole boundaries, impacts on magnetic field inversions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13552, https://doi.org/10.5194/egusphere-egu21-13552, 2021.

EGU21-955 | vPICO presentations | ST1.4

Plasma Waves Near the Electron Cyclotron Frequency in the Near Sun Solar Wind: Wave Mode Identification and Driving Instabilities

David Malaspina, Lynn Wilson, Robert Ergun, Stuart Bale, John Bonnell, Thierry Dudok de Wit, Keith Goetz, Katherine Goodrich, Peter Harvey, Robert MacDowall, Marc Pulupa, Jasper Halekas, Anthony Case, Davin Larson, Michael Stevens, and Phyllis Whittlesey

Recent studies of the solar wind sunward of 0.25 AU using the Parker Solar Probe spacecraft reveal that that solar wind can be bimodal, alternating between near quiescent regions with low turbulent fluctuation amplitudes and Parker-like magnetic field direction and regions of highly turbulent plasma and magnetic field fluctuations associated with ‘switchbacks’ of the radial magnetic field.  

The quiescent solar wind regions are highly unstable to the formation of plasma waves near the electron cyclotron frequency (fce), possibly driven by strahl electrons, which carry the solar wind heat flux, and may provide one of the most direct particle diagnostics of the solar corona at the source of the solar wind.  These waves are most intense near ~0.7 fce and ~fce. The near-fce waves are found to become more intense and more frequent closer to the Sun, and statistical evidence indicates that their occurrence rate is related to the sunward drift of the core electron population.  

In this study, we examine high time resolution burst captures of these waves, demonstrating that each wave burst contains several distinct wave types, including electron Bernstein waves and extremely narrow band waves that are highly sensitive to the magnetic field orientation. Using properties of these waves we provide evidence to support the identification of their likely plasma wave modes and the instabilities responsible for generating these waves.  By understanding the driving instabilities responsible for these waves, we infer their ability to modify electron distribution functions in the quiescent near-Sun solar wind.  

How to cite: Malaspina, D., Wilson, L., Ergun, R., Bale, S., Bonnell, J., Dudok de Wit, T., Goetz, K., Goodrich, K., Harvey, P., MacDowall, R., Pulupa, M., Halekas, J., Case, A., Larson, D., Stevens, M., and Whittlesey, P.: Plasma Waves Near the Electron Cyclotron Frequency in the Near Sun Solar Wind: Wave Mode Identification and Driving Instabilities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-955, https://doi.org/10.5194/egusphere-egu21-955, 2021.

EGU21-16103 | vPICO presentations | ST1.4

Electrostatic Waves with Rapid Frequency Shifts in the Solar Wind Sunward of 1/3 AU

Lily Kromyda, David M. Malaspina, Robert E. Ergun, Jasper Halekas, Michael L. Stevens, Jennifer L. Verniero, Daniel Vech, Alexandros Chasapis, Stuart D. Bale, John W. Bonnell, Thierry Dudok de Wit, Keith Goetz, Katherine Goodrich, Peter R. Harvey, Robert J. MacDowall, Marc Pulupa, Anthony W. Case, Justin C. Kasper, Kelly E. Korreck, and Davin E. Larson and the Lily Kromyda

During its first five orbits, the FIELDS plasma wave investigation on board Parker Solar Probe (PSP)  has observed a multitude of plasma waves, including electrostatic whistler and electron Bernstein waves (Malaspina et al. 2020), sunward propagating whistlers (Agapitov et al. 2020), ion-scale electromagnetic waves (Verniero et al. 2020, Bowen et al. 2020) and Alfven, slow and fast mode waves (Chaston et al. 2020).

The importance of these waves lies in their potential to redistribute the energy of the solar wind among different particles species (wave-particle interactions) or different types of waves (wave-wave interactions). The abundance of waves and instabilities observed with PSP points to their central role in the regulation of this energy exchange.

Here we present first observations of an intermittent, electrostatic and broadband plasma wave that is ubiquitous in the range of distances that PSP has probed so far. A unique feature of these waves (FDWs) is a frequency shift that occurs on millisecond timescales. In the frame of the spacecraft, FDWs usually appear between the electron cyclotron and electron plasma frequencies.

We develop a detection algorithm that identifies the FDWs in low cadence spectra. We analyze them using various statistical techniques. We establish their phenomenology and compare the magnetic fluctuations of the background magnetic field at times of FDWs and at times without FDWs. We establish their polarization with respect to the background magnetic field and search for correlations with various plasma parameters and features in the electron, proton and alpha particle distribution moments. We also investigate possible plasma wave modes that could be responsible for the growth of FDWs and the instability mechanisms that could be generating them.

 

Lily Kromyda*(1), David M. Malaspina (1,2), Robert E. Ergun(1,2) , Jasper Halekas(3), Michael L. Stevens(4) , Jennifer Verniero(5), Alexandros Chasapis(2) , Daniel Vech(2) , Stuart D. Bale(5,6) , John W. Bonnell(5) , Thierry Dudok de Wit(7) , Keith Goetz(8) , Katherine Goodrich(5) , Peter R. Harvey(5) , Robert J. MacDowall(9) , Marc Pulupa(5) , Anthony W. Case(4) , Justin C. Kasper(10) , Kelly E. Korreck(4) , Davin Larson(5) , Roberto Livi(5) , Phyllis Whittlesey(5)

(1) Astrophysical and Planetary Sciences Department, University of Colorado, Boulder, CO, USA

(2) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA

(3)  University of Iowa, Iowa City, IA, USA

(4) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA

(5)  Space Sciences Laboratory, University of California, Berkeley, CA, USA

(6) Physics Department, University of California, Berkeley, CA, USA

(7)  LPC2E, CNRS, and University of Orleans, Orleans, France

(8)  School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA

(9)  NASA Goddard Space Flight Center, Greenbelt, MD, USA

(10) University of Michigan, Ann Arbor, MI, USA

How to cite: Kromyda, L., Malaspina, D. M., Ergun, R. E., Halekas, J., Stevens, M. L., Verniero, J. L., Vech, D., Chasapis, A., Bale, S. D., Bonnell, J. W., Dudok de Wit, T., Goetz, K., Goodrich, K., Harvey, P. R., MacDowall, R. J., Pulupa, M., Case, A. W., Kasper, J. C., Korreck, K. E., and Larson, D. E. and the Lily Kromyda: Electrostatic Waves with Rapid Frequency Shifts in the Solar Wind Sunward of 1/3 AU, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16103, https://doi.org/10.5194/egusphere-egu21-16103, 2021.

EGU21-12726 | vPICO presentations | ST1.4

Large-scale Structure and Turbulence Transport in the Young Solar Wind – Comparison of Parker Solar Probe Observations with a Global 3D Reynolds-averaged MHD Model

Rohit Chhiber, Arcadi Usmanov, William Matthaeus, Melvyn Goldstein, and Riddhi Bandyopadhyay
Simulation results from a global magnetohydrodynamic model of the solar corona and the solar wind are compared with Parker Solar Probe's (PSP) observations during its first several orbits. The fully three-dimensional model (Usmanov et al., 2018, ApJ, 865, 25) is based on Reynolds-averaged mean-flow equations coupled with turbulence transport equations. The model accounts for effects of electron heat conduction, Coulomb collisions, Reynolds stresses, and heating of protons and electrons via nonlinear turbulent cascade. Turbulence transport equations for turbulence energy, cross helicity, and correlation length are solved concurrently with the mean-flow equations. We specify boundary conditions at the coronal base using solar synoptic magnetograms and calculate plasma, magnetic field, and turbulence parameters along the PSP trajectory. We also accumulate data from all orbits considered, to obtain the trends observed as a function of heliocentric distance. Comparison of simulation results with PSP data show general agreement. Finally, we generate synthetic fluctuations constrained by the local rms turbulence amplitude given by the model, and compare properties of this synthetic turbulence with PSP observations.

How to cite: Chhiber, R., Usmanov, A., Matthaeus, W., Goldstein, M., and Bandyopadhyay, R.: Large-scale Structure and Turbulence Transport in the Young Solar Wind – Comparison of Parker Solar Probe Observations with a Global 3D Reynolds-averaged MHD Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12726, https://doi.org/10.5194/egusphere-egu21-12726, 2021.

EGU21-3426 | vPICO presentations | ST1.4

The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration

Christopher Chen, Benjamin Chandran, Lloyd Woodham, Shaela Jones, Jean Perez, Sofiane Bourouaine, Trevor Bowen, Kris Klein, Michel Moncuquet, Justin Kasper, and Stuart Bale

The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 Rs, allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP's fourth solar encounter, likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with spectral index close to -5/3 rather than -3/2), a lower Alfvenicity, and a "1/f" break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ~4 degrees from the HCS, suggesting ~8 degrees as the full-width of the streamer belt wind at these distances. While the majority of the Alfvenic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind.

How to cite: Chen, C., Chandran, B., Woodham, L., Jones, S., Perez, J., Bourouaine, S., Bowen, T., Klein, K., Moncuquet, M., Kasper, J., and Bale, S.: The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3426, https://doi.org/10.5194/egusphere-egu21-3426, 2021.

EGU21-12876 | vPICO presentations | ST1.4

Alfvénic versus non-Alfvénic turbulence in the inner heliosphere as observed by Parker Solar Probe

Marco Velli, Chen Shi, Olga Panasenco, Anna Tenerani, Victor Reville, and the PSP* Team

Parker Solar Probe (PSP) measures the magnetic field and plasma parameters of the solar wind at unprecedentedly close distances to the Sun, providing a great opportunity to study the early-stage evolution of magnetohydrodynamic (MHD) turbulence in the solar wind. Here we use PSP data to explore the nature of solar wind turbulence focusing on the Alfvénic character and power spectra of the fluctuations and their dependence on heliocentric distance and context (i.e., large-scale solar wind properties), aiming to understand the role that different effects such as source properties, solar wind expansion, and stream interaction might play in determining the turbulent state. We carried out a statistical survey of the data from the first five orbits of PSP with a focus on how the fluctuation properties at the large MHD scales vary with different solar wind streams and the distance from the Sun. A more in-depth analysis from several selected periods is also presented. Our results show that as fluctuations are transported outward by the solar wind, the magnetic field spectrum steepens while the shape of the velocity spectrum remains unchanged. The steepening process is controlled by the age of the turbulence, which is determined by the wind speed together with the radial distance. Statistically, faster solar wind has higher Alfvénicity with a more dominant outward propagating wave component and more balanced magnetic and kinetic energies. The outward wave dominance gradually weakens with radial distance, while the excess of magnetic energy is found to be stronger as we move closer toward the Sun. We show that the turbulence properties can significantly vary from stream to stream even if these streams are of a similar speed, indicating very different origins of these streams. Especially, the slow wind that originates near the polar coronal holes has much lower Alfvénicity compared with the slow wind that originates from the active regions and pseudostreamers. We show that structures such as the heliospheric current sheet and wind stream velocity shears can play an important role in modifying the properties of the turbulence.

*The PSP Team: Stuart D.Bale,  Justin Kasper, Kelly Korreck, J. W. Bonnell, Thierry Dudok de Wit, Keith Goetz, Peter R. Harvey, Robert J. MacDowall, David Malaspina, Marc Pulupa, Anthony W.Case, Davin Larson,  Jenny Verniero, Roberto Livi, Michael Stevens, PhyllisWhittlesey, Milan Maksimovic, and Michel Moncuquet

How to cite: Velli, M., Shi, C., Panasenco, O., Tenerani, A., Reville, V., and Team, T. P.: Alfvénic versus non-Alfvénic turbulence in the inner heliosphere as observed by Parker Solar Probe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12876, https://doi.org/10.5194/egusphere-egu21-12876, 2021.

EGU21-15512 | vPICO presentations | ST1.4

Characterisation and comparison of slow coronal hole wind intervals at 0.13au

Thomas Woolley, Lorenzo Matteini, Timothy S Horbury, Ronan Laker, Lloyd D Woodham, Stuart D Bale, Julia E Stawarz, Laura Berčič, Michael D McManus, and Samuel T Badman

The slow solar wind is thought to consist of a component originating close to the Heliospheric Current Sheet (HCS) in the streamer belt and a component from over-expanded coronal hole boundaries. In order to understand the roles of these contributions with different origin, it is important to separate and characterise them. By exploiting the fact that Parker Solar Probe’s fourth and fifth orbits were the same and the solar conditions were similar, we identify intervals of slow polar coronal hole wind sampled at approximately the same heliocentric distance and latitude. Here, solar wind properties are compared, highlighting typical conditions of the slow coronal hole wind closer to the Sun than ever before. We explore different properties of the plasma, including composition, spectra and microphysics, and discuss possible origins for the features that are observed.

How to cite: Woolley, T., Matteini, L., Horbury, T. S., Laker, R., Woodham, L. D., Bale, S. D., Stawarz, J. E., Berčič, L., McManus, M. D., and Badman, S. T.: Characterisation and comparison of slow coronal hole wind intervals at 0.13au, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15512, https://doi.org/10.5194/egusphere-egu21-15512, 2021.

EGU21-14779 | vPICO presentations | ST1.4

Source-dependent properties of the background slow solar wind encountered by Parker Solar Probe

Léa Griton, Sarah Watson, Nicolas Poirier, Alexis Rouillard, Karine Issautier, Michel Moncuquet, Rui Pinto, Stuart Bale, and Justin Kasper

Different states of the slow solar wind are identified from in-situ measurements by Parker Solar Probe (PSP) inside 50 solar radii from the Sun (Encounters 1, 2, 4, 5 and 6). At such distances the wind measured at PSP has not yet undergone significant transformation related to the expansion and propagation of the wind. We focus in this study on the properties of the quiet solar wind with no magnetic switchbacks. The Slow Solar Wind (SSW) states differ by their density, flux, plasma beta and magnetic pressure. PSP's magnetic connectivity established with Potential Field Source Surface (PFSS) reconstructions, tested against extreme ultraviolet (EUV) and white-light imaging, reveals the different states under study generally correspond to transitions from streamers to equatorial coronal holes. Solar wind simulations run along these differing flux tubes reproduce the slower and denser wind measured in the streamer and the more tenuous wind measured in the coronal hole. Plasma heating is more intense at the base of the streamer field lines rooted near the boundary of the equatorial hole than those rooted closer to the center of the hole. This results in a higher wind flux driven inside the streamer than deeper inside the equatorial hole. 

How to cite: Griton, L., Watson, S., Poirier, N., Rouillard, A., Issautier, K., Moncuquet, M., Pinto, R., Bale, S., and Kasper, J.: Source-dependent properties of the background slow solar wind encountered by Parker Solar Probe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14779, https://doi.org/10.5194/egusphere-egu21-14779, 2021.

EGU21-2877 | vPICO presentations | ST1.4

Evolution of the Solar Wind Direction through the Heliosphere

Zdeněk Němeček, Tereza Ďurovcová, Jana Šafránková, John D. Richardson, Jiří Šimůnek, and Michael L. Stevens

The solar wind non-radial velocity components observed beyond the Alfvén point are usually attributed to waves, the interaction of different streams, or other transient phenomena. However, Earth-orbiting spacecraft as well as monitors at L1 indicate systematic deviations of the wind velocity from the radial direction. Since these deviations are of the order of several degrees, the calibration of the instruments is often questioned. This paper investigates for the first time the evolution of non-radial components of the solar wind flow along the path from ≈ 0.17 to 10 AU. A comparison of observations at 1 AU with those closer to or farther from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Parker Solar Probe, Helios 1 and 2, Wind, ACE, Spektr-R, ARTEMIS probes, MAVEN, Voyagers 1and 2) shows that (i) the average values of non-radial components are not zero and vary in a systematic manner with the distance from the Sun, (ii) their values significantly depend on the solar wind radial velocity, (iii) the deviation from radial direction well correlates with the cross-helicity, and (iv) the values of non-radial components peaks at 0.25 AU and gradually decreases toward zero in the outer heliosphere. Our results suggest that the difference in the propagation direction between the faster and slower winds is already established in the solar corona and is connected with the forces emitting solar wind plasma from the coronal magnetic field. The correlation with cross-helicity probably points to outward propagating Alfven waves generated in outer corona as the most probable source of observed deviations.

How to cite: Němeček, Z., Ďurovcová, T., Šafránková, J., Richardson, J. D., Šimůnek, J., and Stevens, M. L.: Evolution of the Solar Wind Direction through the Heliosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2877, https://doi.org/10.5194/egusphere-egu21-2877, 2021.

EGU21-15718 | vPICO presentations | ST1.4

Radial Evolution of the Solar Wind and Associating Turbulence Based on the Synergetic Measurement from Parker Solar Probe and 1 au Observations

Die Duan, Jiansen He, Xingyu Zhu, Daniel Verscharen, Trevor Bowen, Samuel Badman, and Stuart Bale
The 4th encounter (~30 Rs away from the sun) of the Parker Solar Probe (PSP) is a great opportunity to observe the radial evolution of the solar wind from the inner heliosphere to the near-earth environment when the sun, PSP, and the earth are quasi-radial aligned. Similar features of the solar wind are observed from both PSP and Wind (at 1 au) measurements. The accelerating-solar-wind model could be more suitable than the constant speed model for the observation, which means the solar wind is still accelerating from 30 Rs to 1 au. Both PSP and Wind measure the co-existence of the Alfvenic and compressive fluctuations in the solar wind. The correlated radial velocity (dVR), proton density (dn) and temperature (dT) fluctuations indicate the nature of the compressive fluctuations are outward-propagating slow waves. However, dn and dB is not correlated from PSP, but correlated from Wind, which indicates the propagating direction of the slow waves is changed. Comparing the radial evolution of the energies of both Alfvenic and compressive fluctuations with the WKB model, we find the observed energy decays slower than the theoretical prediction, which indicates an extra energy injection during the solar wind propagation.

How to cite: Duan, D., He, J., Zhu, X., Verscharen, D., Bowen, T., Badman, S., and Bale, S.: Radial Evolution of the Solar Wind and Associating Turbulence Based on the Synergetic Measurement from Parker Solar Probe and 1 au Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15718, https://doi.org/10.5194/egusphere-egu21-15718, 2021.

EGU21-14696 | vPICO presentations | ST1.4

Statistical Differences of Magnetic Field Kinks Observed by PSP and WIND

Chuanpeng Hou, Xingyu Zhu, Rui Zhuo, and Jiansen He

Parker Solar Probe’s (PSP) observations near the sun show the extensive presence of magnetic field kinks (switchback for large kinks) in the slow solar wind. These kinks are usually accompanied by the enhancement of radial solar wind velocity and ion temperature, increasing or decreasing of number density. The magnetic field kinks have also been observed by WIND and Ulysses to exist near and beyond 1 AU, respectively. In this study, we statistically analyze the property difference of magnetic field kinks observed by PSP and WIND. We obtain the following four points of results. (1) Inside the PSP-kinks, the radial velocity and protons’ temperature increase while density shows enhancement or descent. However, inside the WIND-kinks, besides the slight enhancement of radial velocity, the density and temperature show no obvious change compared with the outside plasma. (2) By employing the Walen-test of kinks, we find that, R components of some PSP-kinks but not all satisfy the rotational discontinuity (RD) features, while the three components of most WIND-kinks well match the RD features. (3) The correlation between magnetic field and velocity inside the PSP-kinks and WIND-kinks does not show significant differences. (4) Both the PSP-kinks and WIND-kinks can be divided into two groups based on the histograms of θBn, where B is the background magnetic field, and n is the normal direction of kink. The first group (group-I) has θBn concentrating around 20° for PSP-kinks and 30° for WIND-kinks, indicating that the satellites were crossing the same kinked interplanetary magnetic field (IMF) from the upstream to the downstream. The second group (group-II) has θBn concentrating around 90° for PSP-kinks and WIND-kinks, suggesting that the satellites were crossing an interface between the unkinked and kinked IMF regions. Our findings help better understanding the nature of kinks and provide the observational basis for testifying models about radial propagation and evolution of magnetic field kinks.

How to cite: Hou, C., Zhu, X., Zhuo, R., and He, J.: Statistical Differences of Magnetic Field Kinks Observed by PSP and WIND, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14696, https://doi.org/10.5194/egusphere-egu21-14696, 2021.

EGU21-6303 | vPICO presentations | ST1.4

The influence of the dust-free zone on F-corona brightness

Saliha Eren and Ingrid Mann

This presentation is related to model calculations of the circumsolar dust brightness that is seen in the F-corona and inner Zodiacal light. We calculate the brightness integral that includes the size distribution of the interplanetary dust, the spatial distribution, and the scattering properties. The scattering properties are estimated with Mie calculations of spherical particles consisting of astronomical silicate. We consider different size distributions of the dust particles with sizes between 1 nanometre - 100 micrometre. It was recently discussed that the extension of the dust-free zone can be inferred from the slope of the F-corona brightness seen in new observations received from the WISPR instrument on the NASA Parker Solar Probe (Stenborg et al., 2020). We, therefore, investigate the influence of the dust-free zone on the brightness and compare it to the influence that the dust size distribution has.

References

1. G. Stenborg, R. A. Howard, P. Hess, B. Gallagher, PSP/WISPR observations of dust density depletion near the Sun I. Remote observations to 8 Rsol from an observer between 0.13-0.35 AU, A&A, Forthcoming article, 2020. DOI: 10.1051/0004-6361/202039284

How to cite: Eren, S. and Mann, I.: The influence of the dust-free zone on F-corona brightness, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6303, https://doi.org/10.5194/egusphere-egu21-6303, 2021.

EGU21-8043 | vPICO presentations | ST1.4

Small-scale Magnetic Flux Ropes with Field-aligned Flows via the PSP In-situ Observations

Yu Chen, Qiang Hu, and Lingling Zhao

Magnetic flux rope, formed by the helical magnetic field lines, can sometimes remain its shape while carrying significant plasma flow that is aligned with the local magnetic field. We report the existence of such structures and static flux ropes by applying the Grad-Shafranov-based algorithm to the Parker Solar Probe (PSP) in-situ measurements in the first five encounters. These structures are detected at heliocentric distances, ranging from 0.13 to 0.66 au, in a total of 4-month time period. We find that flux ropes with field-aligned flows have certain properties similar to those of static flux ropes, such as the decaying relations of the magnetic fields within structures with respect to heliocentric distances. Moreover, these events are more likely with magnetic pressure dominating over the thermal pressure and occurring more frequently in the relatively fast-speed solar wind. Taking into account the high Alfvenicity, we also compare these events with switchbacks and present the cross-section maps via the new Grad-Shafranov type reconstruction. Finally, the possible evolution and relaxation of the magnetic flux rope structures are discussed.

How to cite: Chen, Y., Hu, Q., and Zhao, L.: Small-scale Magnetic Flux Ropes with Field-aligned Flows via the PSP In-situ Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8043, https://doi.org/10.5194/egusphere-egu21-8043, 2021.

EGU21-14934 | vPICO presentations | ST1.4

Parker Solar Probe Observations of Alfvénic Waves and Ion-cyclotron Waves in a Small-scale Flux Rope

Chen Shi, Jinsong Zhao, Jia Huang, Tieyan Wang, Dejin Wu, Yu Chen, Qiang Hu, Justin C. Kasper, and Stuart D. Bale

Magnetic flux ropes can play important roles in transferring the mass, momentum, and energy in the interplanetary environment and in affecting space weather. Small-scale flux ropes (SFRs) are common in the interplanetary environment. However, SFRs with medium and high Alfvénicity are generally discarded in previous identification procedures. Using Parker Solar Probe measurements, we identify an SFR event with medium Alfvénicity in the inner heliosphere (at ~ 0.2 au). Based on high correlations between the magnetic field and velocity fluctuations, we show Alfvénic waves arising inside such SFR. We also show occurrence of quasi-monochromatic electromagnetic waves at the leading and trailing edges of this SFR. These waves are well explained by the outward-propagating ion-cyclotron waves, which have wave frequencies ~ 0.03 - 0.3 Hz and wavelengths ~ 60 - 2000 km in the plasma frame. Furthermore, we show that the power spectral density of the magnetic field in SFR middle region follows the power-law distribution, where the spectral index changes from -1.5 (f <~ 1 Hz) to -3.3 (f >~ 1 Hz). These findings would motivate developing an automated program to identify SFRs with medium and high Alfvénicity from Alfvénic waves structures.

How to cite: Shi, C., Zhao, J., Huang, J., Wang, T., Wu, D., Chen, Y., Hu, Q., Kasper, J. C., and Bale, S. D.: Parker Solar Probe Observations of Alfvénic Waves and Ion-cyclotron Waves in a Small-scale Flux Rope, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14934, https://doi.org/10.5194/egusphere-egu21-14934, 2021.

EGU21-9911 | vPICO presentations | ST1.4

Flux tubes and energetic particles in Parker Solar Probe orbit 5: magnetic helicity - PVI method and ISOIS observations

Francesco Pecora, Sergio Servidio, Antonella Greco, Stuart D. Bale, David J. McComas, Colin J. Joyce, and William H. Matthaeus

Plasma turbulence can be viewed as a magnetic landscape populated by large- and small-scale coherent structures, consisting notionally of magnetic flux tubes and their boundaries. Such structures exist over a wide range of scales and exhibit diverse morphology and plasma properties.  Moreover, interactions of particles with turbulence may involve temporary trapping in, as well as exclusion from, certain regions of space, generally controlled by the topology and connectivity of the magnetic field.  In some cases, such as SEP "dropouts'' the influence of the magnetic structure is dramatic; in other cases, it is more subtle, as in edge effects in SEP confinement. With Parker Solar Probe now closer to the sun than any previous mission, novel opportunities are available for examination of the relationship between magnetic flux structures and energetic particle populations. 

We present a method that is able to characterize both the large- and small-scale structures of the turbulent solar wind, based on the combined use of a filtered magnetic helicity (Hm) and the partial variance of increments (PVI). The synergistic combination with energetic particle measurements suggests whether these populations are either trapped within or excluded from the helical structure.

This simple, single-spacecraft technique exploits the natural tendency of flux tubes to assume a cylindrical symmetry of the magnetic field about a central axis. Moreover, large helical magnetic tubes might be separated by small-scale magnetic reconnection events (current sheets) and present magnetic discontinuity with the ambient solar wind. The method was first validated via direct numerical simulations of plasma turbulence and then applied to data from the Parker Solar Probe (PSP) mission. In particular, ISOIS energetic particle (EP) measurements along with FIELDS magnetic field measurements and SWEAP plasma moments, are enabling characterization of observations of EPs closer to their sources than ever before.
 
This novel analysis, combining Hm and PVI methods, reveals that a large number of flux tubes populate the solar wind and continuously merge in contact regions where magnetic reconnection and particle acceleration may occur. Moreover, the detection of boundaries, correlated with high-energy particle measurements, gives more insights into the nature of such helical structures as "excluding barriers'' suggesting a strong link between particle properties and fields topology. This research is partially supported by the Parker Solar Probe project. 

How to cite: Pecora, F., Servidio, S., Greco, A., Bale, S. D., McComas, D. J., Joyce, C. J., and Matthaeus, W. H.: Flux tubes and energetic particles in Parker Solar Probe orbit 5: magnetic helicity - PVI method and ISOIS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9911, https://doi.org/10.5194/egusphere-egu21-9911, 2021.

EGU21-13959 | vPICO presentations | ST1.4

Magnetic Field Line Random Walk and Solar Energetic Particle Path Lengths

William Matthaeus, Rohit Chhiber, Christina M. S. Cohen, David Ruffolo, Wirin Sonsrettee, Paisan Tooprakai, Achara Seripienlert, Piyanate Chuychai, Arcadi V. Usmanov, Melvyn . L. Goldstein, and David J. McComas and the PSP/ISOIS Team

In 2020 May-June, six solar energetic ion events were observed by the Parker Solar Probe/ISoIS instrument suite at ~0.35 AU from the Sun.  From standard velocity-dispersion analysis, the apparent ion path length is ~0.625 AU at the onset of each event. We develop a formalism for estimating the path length of random-walking magnetic field lines, to explain why the apparent ion path length at event onset greatly exceeds the radial distance from the Sun for these events. We developed analytical estimates of the average increase in path length of random-walking magnetic field lines, relative to the unperturbed mean field. Both a simple estimate and a rigorous theoretical formulation are obtained for field-lines' path length increase as a function of path length along the large-scale field. Monte Carlo simulations of field line and particle trajectories in a model of solar wind turbulence are used to validate the formalism and study the path lengths of particle guiding-center and full-orbital trajectories. From these simulated trajectories, we find that particle guiding centers can have path lengths somewhat shorter than the average field line path length, while particle orbits can have substantially larger path lengths due to their gyromotion with a nonzero effective pitch angle. The formalism is also implemented in a global solar wind model, and results are compared with ion path lengths inferred from ISoIS observations. The long apparent pathlength during these solar energetic ion events can be explained by 1) a magnetic field line path length increase due to the field line random walk, and 2) particle transport about the guiding center with nonzero effective pitch angle due to pitch angle scattering. This research partially supported by the PSP /ISOIS project.

How to cite: Matthaeus, W., Chhiber, R., Cohen, C. M. S., Ruffolo, D., Sonsrettee, W., Tooprakai, P., Seripienlert, A., Chuychai, P., Usmanov, A. V., Goldstein, M. L., and McComas, D. J. and the PSP/ISOIS Team: Magnetic Field Line Random Walk and Solar Energetic Particle Path Lengths, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13959, https://doi.org/10.5194/egusphere-egu21-13959, 2021.

ST1.5 – Turbulence and Waves in Space Plasmas

EGU21-77 | vPICO presentations | ST1.5

Measurement of the effective mean-free-path of the solar wind protons

Jesse Coburn, Christopher Chen, and Jonathan Squire

The solar corona is heated and accelerated sufficiently to escape the gravitational bound of the sun into the interplanetary medium as a super-Alfvénic turbulent plasma called the solar wind. The Spitzer-Härm particle mean-free-path and relaxation time (i.e. to an isotropic Maxwellian distribution function) for typical solar wind proton parameters are large compared to the system size and therefore a non-collisional treatment of the plasma can be argued to be appropriate. Despite the long mean-free-path, large scales of the solar wind are fluid-like: density-pressure polarizations follow a polytropic equation of state. These observations suggest effective collisional processes (e.g. quasi-linear relaxation, plasma wave echo) are active, altering the equation of state from a non-collisional (or kinetic) to a polytropic equation of state (e.g. fluid magnetohydrodynamics [MHD]). We employ 13 years of high cadence onboard 0th-2nd moments of the proton velocity distribution function recorded by the Wind spacecraft to study the equation of state via compressive fluctuations. Upon comparison with a collisional kinetic-MHD dispersion relation solver, our analysis indicates an effective mean-free-path (collision frequency) that is [∼102] smaller (larger) than the typical Spitzer-Härm estimate. This effect is scale dependent justifying a fluid approach to large scales which breaks down at smaller scales where a more complex equation of state is necessary.

How to cite: Coburn, J., Chen, C., and Squire, J.: Measurement of the effective mean-free-path of the solar wind protons, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-77, https://doi.org/10.5194/egusphere-egu21-77, 2021.

EGU21-990 | vPICO presentations | ST1.5

Slow electrostatic solitary waves in the Earth's magnetosphere

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

Slow electron holes, that are electrostatic solitary waves propagating with velocities comparable to the ion thermal velocity, can contribute to plasma heating and provide an anomalous resistivity in various space plasma systems. In addition, the analysis of electron holes allows revealing instabilities operating on time scales not resolved by plasma instruments. We present experimental analysis of more than 100 slow electron holes in the Earth’s bow shock and more than 1000 slow electron holes in the Earth’s nightside magnetosphere. We show that in both regions, the electron holes have similar parameters. The spatial scales are in the range from 1 to 10 Debye lengths, amplitudes of the electrostatic potential are typically below 0.1 of local electron temperature, velocities in the plasma rest frame are of the order of local ion-acoustic velocity. We show that in both regions the electron holes are most likely produced by Buneman-type instabilities. We develop theoretical models of the electron holes and compare them to MMS observations. The lifetime and the transverse instability of the electron holes are discussed.

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

How to cite: Kamaletdinov, S., Vasko, I., Yushkov, E., Artemyev, A., and Wang, R.: Slow electrostatic solitary waves in the Earth's magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-990, https://doi.org/10.5194/egusphere-egu21-990, 2021.

EGU21-2032 | vPICO presentations | ST1.5

Higher-Order Statistics in Compressive Solar Wind Plasma Turbulence: High-Resolution Density Observations From the Magnetospheric MultiScale Mission

Owen Roberts, Jessica Thwaites, Luca Sorriso-Valvo, Rumi Nakamura, and Zoltan Voros

Turbulent density fluctuations are investigated in the solar wind at sub-ion scales using calibrated spacecraft potential. The measurement technique using the spacecraft potential allows for a much higher time resolution and sensitivity when compared to direct measurements using plasma instruments. Using this novel method, density fluctuations can be measured with unprecedentedly high time resolutions for in situ measurements of solar wind plasma at 1 a.u. By investigating 1 h of high-time resolution data, the scale dependant kurtosis is calculated by varying the time lag τ to calculate increments between observations. The scale-dependent kurtosis is found to increase towards ion scales but then plateaus and remains fairly constant through the sub-ion range in a similar fashion to magnetic field measurements. The sub-ion range is also found to exhibit self-similar monofractal behavior contrasting sharply with the multi-fractal behavior at large scales. The scale-dependent kurtosis is also calculated using increments between two different spacecraft. When the time lags are converted using the ion bulk velocity to a comparable spatial lag, a discrepancy is observed between the two measurement techniques. Several different possibilities are discussed including a breakdown of Taylor’s hypothesis, high-frequency plasma waves, or intrinsic differences between sampling directions.

How to cite: Roberts, O., Thwaites, J., Sorriso-Valvo, L., Nakamura, R., and Voros, Z.: Higher-Order Statistics in Compressive Solar Wind Plasma Turbulence: High-Resolution Density Observations From the Magnetospheric MultiScale Mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2032, https://doi.org/10.5194/egusphere-egu21-2032, 2021.

EGU21-2837 | vPICO presentations | ST1.5

Power spectral density of magnetic field and ion velocity fluctuations from inertial to kinetic ranges

Jana Šafránková, Zdeněk Němeček, František Němec, Luca Franci, and Alexander Pitňa

The solar wind is a unique laboratory to study the turbulent processes occurring in a collisionless plasma with high Reynolds numbers. A turbulent cascade—the process that transfers the free energy contained within the large scale fluctuations into the smaller ones—is believed to be one of the most important mechanisms responsible for heating of the solar corona and solar wind. The paper analyzes power spectra of solar wind velocity, density and magnetic field fluctuations that are computed in the frequency range around the break between inertial and kinetic scales. The study uses measurements of the Bright Monitor of the Solar Wind (BMSW) on board the Spektr-R spacecraft with a time resolution of 32 ms complemented with 10 Hz magnetic field observations from the Wind spacecraft propagated to the Spektr-R location. The statistics based on more than 42,000 individual spectra show that: (1) the spectra of both quantities can be fitted by two (three in the case of the density) power-law segments; (2) the median slopes of parallel and perpendicular fluctuation velocity and magnetic field components are different; (3) the break between MHD and kinetic scales as well as the slopes are mainly controlled by the ion beta parameter. These experimental results are compared with high-resolution 2D hybrid particle-in-cell simulations, where the electrons are considered to be a massless, charge-neutralizing fluid with a constant temperature, whereas the ions are described as macroparticles representing portions of their distribution function. In spite of several limitations (lack of the electron kinetics, lower dimensionality), the model results agree well with the experimental findings. Finally, we discuss differences between observations and simulations in relation to the role of important physical parameters in determining the properties of the turbulent cascade.

How to cite: Šafránková, J., Němeček, Z., Němec, F., Franci, L., and Pitňa, A.: Power spectral density of magnetic field and ion velocity fluctuations from inertial to kinetic ranges, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2837, https://doi.org/10.5194/egusphere-egu21-2837, 2021.

The space between the Sun and our planet is not empty. It is filled with the expanding plasma of the solar corona called the Solar Wind, which is a tenuous weakly collisional plasma composed mainly by protons and electrons. Due to the lack of sufficient collisions, the electron velocity distribution function in the Solar Wind usually exhibits a variety of non-thermal characteristics that deviate from the thermodynamic equilibrium. These deviations from equilibrium provide a local source for electromagnetic fluctuations, intimately related to the shape of the distribution function, and associated with the commonly observed kinetic instabilities such as the whistler-cyclotron for T/ T>1, and firehose for T/ T<1 and large enough plasma beta. In this work we carry out systematic statistical study of correlations of various plasma moments and interplanetary magnetic fluctuations as a function of time, in order to describe the role and evolution of these parameters in the solar plasma through the solar cycle. We consider a large time interval during solar cycle 23, ranging from solar minimum (1995-1996) to solar maximum (2000-2001). Using NASA's Wind space mission and its SWE and High-Resolution MFI instruments with resolutions of 6-15 sec and 11 vectors/sec, respectively, we show that collisionless kinetic instabilities can regulate the electron distribution as the whistler-cyclotron and firehose instability thresholds bound the temperature and plasma beta electron distributions, and such regulation is more effective during solar minimum. Subsequently, the magnetic fluctuations level increases as the electron VDF acquires a configuration close to the thresholds. In addition, we note that there is a high difference between the fast and slow wind regimes given a greater tendency towards larger collisionallity and isotropization for low speeds streams, and magnetic fluctuations amplitude decreases as collisional age increases. In summary, our results indicate that collisionless plasma processes and Coulomb collisions effects coexist and both seem to play relevant roles in shaping the observed electron distributions.

How to cite: Silva, J., Moya, P., and Viñas, A.: Study of the relationship between the observations of electron distributions in the solar wind and interplanetary magnetic field fluctuations , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3332, https://doi.org/10.5194/egusphere-egu21-3332, 2021.

EGU21-3464 | vPICO presentations | ST1.5

Skew-Kappa distribution functions & whistler-heat flux instability in the solar wind

Bea Zenteno-Quinteros, Adolfo F. Viñas, and Pablo S. Moya

Electron velocity distributions in the solar wind are known to have field-aligned skewness, which has been observationally characterized by the presence of secondary populations such as the halo and strahl electron components. This non-thermal feature provides energy for the excitation of electromagnetic instabilities that may play a role in regulating the electron heat flux in the solar wind by wave-particle interactions. Among the wave modes excited in regulating the electron non-thermal features is the whistler-mode and its so-called whistler heat-flux instability (WHFI). In this work, we use kinetic linear theory to analyze the stability of the WHFI in a solar wind like plasma where the electrons are described as a single population modeled by a Kappa distribution to which an asymmetry term has been added. We solve the dispersion relation numerically for the parallel propagating whistler-mode and study its linear stability for different plasma parameters. We also show the marginal stability thresholds for this instability as a function of the electron beta and the parallel electron heat flux and present a threshold condition for instability that can be modeled to compare with observational data. The principal result is that the WHFI can develop in this system; however, the heat flux parameter is not a good predictor of how unstable this wave mode will be. This is because different plasma states, with different stability to WHFI, can have the same initial heat flux. Thus, systems with high can be stable enough to WHFI so that it cannot effectively modify the heat flux values through wave-particle interactions

How to cite: Zenteno-Quinteros, B., F. Viñas, A., and Moya, P. S.: Skew-Kappa distribution functions & whistler-heat flux instability in the solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3464, https://doi.org/10.5194/egusphere-egu21-3464, 2021.

EGU21-3597 | vPICO presentations | ST1.5

Effects of the Background Turbulence on the Relaxation of Ion Temperature Anisotropy in Space Plasmas

Pablo S Moya and Roberto E Navarro

Turbulence in space plasmas usually exhibits two regimes separated by a spectral break that divides the so called inertial and kinetic ranges. Large scale magnetic fluctuations are dominated by MHD non-linear wave-wave interactions following a -5/3 or -3/2 slope power-law spectrum. After the break, at scales in which kinetic effects take place, the magnetic spectrum follows a steeper power-law k- α shape given by a spectral index α > 5/3. The location of the break and the particular value of α, depend on plasma conditions, and different space environments can exhibit different spectral indices. Despite its ubiquitousness, the possible effects of a turbulent background spectrum in the quasilinear relaxation of solar wind temperatures are usually not considered. In this work, a quasilinear kinetic theory is used to study the evolution of the proton temperatures in a solar wind-like plasma composed by cold electrons and bi-Maxwellian protons, in which electromagnetic waves propagate along a background magnetic field. Four wave spectrum shapes are compared with different levels of wave intensity. We show that a sufficient turbulent magnetic power can drive stable protons to transverse heating, resulting in an increase in the temperature anisotropy and the reduction of the parallel proton beta. Thus, stable proton velocity distribution can evolve in such a way as to develop kinetic instabilities. This may explain why the constituents of the solar wind can be observed far from thermodynamic equilibrium and near the instability thresholds.

How to cite: Moya, P. S. and Navarro, R. E.: Effects of the Background Turbulence on the Relaxation of Ion Temperature Anisotropy in Space Plasmas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3597, https://doi.org/10.5194/egusphere-egu21-3597, 2021.

The zeroth law of turbulence is one of the oldest conjecture in turbulence that is still unproven. We consider weak solutions of one-dimensional (1D) compressible magnetohydrodynamics (MHD) and demonstrate that the lack of smoothness of the fields introduces a new dissipative term, named inertial dissipation, into the expression of energy conservation that is neither viscous nor resistive in nature. We propose exact solutions assuming that the kinematic viscosity and the magnetic diffusivity are equal, and we demonstrate that the associated inertial dissipation is, on average, positive and equal to the mean viscous dissipation rate in the limit of small viscosity, proving the conjecture of the zeroth law of turbulence.

We show that discontinuities commonly de- tected by Voyager 1 & 2 in the solar wind at 2–10AU can be fitted by the inviscid analytical profiles. We deduce a heating rate of ∼ 10−18 Jm−3s−1 , which is significantly higher than the value obtained from the turbulent fluctuations. This suggests that collisionless shocks are a dominant source of heating in the outer solar wind.

How to cite: David, V. and Galtier, S.: Proof of the zeroth law of turbulence in one-dimensional compressible magnetohydrodynamics and heating of the sawtooth solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7768, https://doi.org/10.5194/egusphere-egu21-7768, 2021.

EGU21-8566 | vPICO presentations | ST1.5

Electromagnetic ion-cyclotron instability in low beta plasma with intrinsic Alfven waves

GuanShan Pu, ChuanBing Wang, PeiJin Zhang, and Lin Ye

Intrinsic Alfven waves (IAWs) exist pervasively in the solar-terrestrial plasma, which can preferentially heat newborn ions in the direction perpendicular to the ambient magnetic field via non-resonant interactions when the plasma beta is low. The anisotropized newborn ion populations can excite electromagnetic ion-cyclotron (EMIC) instability. Parametric calculations indicate that the lower the plasma beta is, the higher the growth rate, while the growth rate increases with the number density of newborn ions and the intensity of IAWs. The marginal stable surface in three-dimensional parameter space is also calculated, which provides a qualitative description of parametric conditions for instability. We propose that the coupled effects of non-resonant heating by IAWs and EMIC instability could be an effective mechanism for transferring the energy from low-frequency IAWs to EMIC waves with a frequency below the gyrofrequency of the corresponding ion species. Furthermore, the temperature anisotropy of background ions with the same sense has positive effects on the growth of EMIC waves excited by newborn ions.

How to cite: Pu, G., Wang, C., Zhang, P., and Ye, L.: Electromagnetic ion-cyclotron instability in low beta plasma with intrinsic Alfven waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8566, https://doi.org/10.5194/egusphere-egu21-8566, 2021.

EGU21-8898 | vPICO presentations | ST1.5

Turbulent energy transfer in bidimensional numerical models of plasma

Rocio Manobanda, Christian Vasconez, Denise Perrone, Raffaele Marino, Dimitri Laveder, Francesco Valentini, Sergio Servidio, Pablo Minini, and Luca Sorriso-Valvo

Structured, highly variable and virtually collision-free. Space plasma is an unique laboratory for studying the transfer of energy in a highly turbulent environment. This turbulent medium plays an important role in various aspects of the Solar--Wind generation, particles acceleration and heating, and even in the propagation of cosmic rays. Moreover, the Solar Wind continuous expansion develops a strong turbulent character, which evolves towards a state that resembles the well-known hydrodynamic turbulence (Bruno and Carbone). This turbulence is then dissipated from magnetohydrodynamic (MHD) through kinetic scales by different -not yet well understood- mechanisms. In the MHD approach, Kolmogorov-like behaviour is supported by power-law spectra and intermittency measured in observations of magnetic and velocity fluctuations. In this regime, the intermittent cross-scale energy transfer has been extensively described by the Politano--Pouquet (global) law, which is based on conservation laws of the MHD invariants, and was recently expanded to take into account the physics at the bottom of the inertial (or Hall) range, e.g. (Ferrand et al., 2019). Following the 'Turbulence Dissipation Challenge', we study the properties of the turbulent energy transfer using three different bi-dimensional numerical models of space plasma. The models, Hall-MHD (HMHD), Landau Fluid (LF) and Hybrid Vlasov-Maxwell (HVM), were ran in collisionless-plasma conditions, with an out-of-plane ambient magnetic field, and with magnetic diffusivity carefully calibrated in the fluid models. As each model has its own range of validity, it allows us to explore a long-enough range of scales at a period of maximal turbulence activity. Here, we estimate the local and global scaling properties of different energy channels using a, recently introduced, proxy of the local turbulent energy transfer (LET) rate (Sorriso-Valvo et al., 2018). This study provides information on the structure of the energy fluxes that transfers (and dissipates) most of the energy at small scales throughout the turbulent cascade. 

How to cite: Manobanda, R., Vasconez, C., Perrone, D., Marino, R., Laveder, D., Valentini, F., Servidio, S., Minini, P., and Sorriso-Valvo, L.: Turbulent energy transfer in bidimensional numerical models of plasma, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8898, https://doi.org/10.5194/egusphere-egu21-8898, 2021.

EGU21-9861 | vPICO presentations | ST1.5

Spectral evolution of Alfvénic turbulence

Roland Grappin, Andrea Verdini, and Wolf-Christian Müller

Alfvénic turbulence denotes a regime of MHD turbulence in which Alfvén waves propagating in a given direction along the mean field are dominant, as commonly found in polar regions/coronal holes/fast solar wind. 

Generalization to Alfvénic turbulence of the Iroshnikov-Kraichnan (IK) weak theory concluded that one should observe a time increase of the imbalance between both Alfvén species and observe the so-called “spectral pinning”, i.e., steep spectra (with spectral index m+>3/2) for the dominant energy E+ and flat spectra (with index m-<3/2) for the sub-dominant energy E-.

Since then, observations in the inner heliosphere have shown on the contrary a decrease of imbalance with time, with both species showing the same flat spectra (m± → -3/2) when imbalance is large.

We show here using direct MHD simulations that both behaviors may occur, the control parameters being the solar wind expansion rate as well as initial conditions of the plasma close to the Sun.

How to cite: Grappin, R., Verdini, A., and Müller, W.-C.: Spectral evolution of Alfvénic turbulence, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9861, https://doi.org/10.5194/egusphere-egu21-9861, 2021.

EGU21-11106 | vPICO presentations | ST1.5

Karman-Howarth-Monin equation for compressible Hall MHD  turbulence: 2D and 3D Hall MHD simulations

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

Turbulence in the solar wind is developed along a vast range of scales, generally under weakly compressible and strong magnetic field plasma conditions.
The effects of weakly and moderate compressibility (Mach ≤1) and turbulence anisotropy on the energy transfer rate are investigated at MHD and Hall MHD scales. For this purpose, the results of two and three-dimensional compressible Hall MHD simulations are analyzed using a new form of the Karman-Howarth-Monin (KHM) equations that accounts for compressible effects down to Hall MHD scales.
The KHM are dynamic equations directly derived from the basic fluid equations that describe the plasma, such as the Hall MHD equations. They provide a relation between the two-point cross-correlations in real space or II-order structure functions, the III-order structure functions and the energy cascade rate of turbulence. These relations depend upon turbulence anisotropy. The effects of compressibility and the Hall term on anisotropy and the estimation of the energy cascade rate via the KHM equations are discussed.

How to cite: Montagud-Camps, V., Hellinger, P., Verdini, A., Landi, S., Papini, E., Franci, L., and Matteini, L.: Karman-Howarth-Monin equation for compressible Hall MHD  turbulence: 2D and 3D Hall MHD simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11106, https://doi.org/10.5194/egusphere-egu21-11106, 2021.

EGU21-11561 | vPICO presentations | ST1.5

Young solar wind coherent structures from inertial to sub-ion range

Alexander Vinogradov, Olga Alexandrova, Anton Artemyev, Milan Maksimovic, Vasiliev Alexei, Anatoly Petrukovich, Stuart Bale, Karine Issautier, and Michel Moncuquet

We study intermittency of turbulence in the young solar wind at 0.17 au with NASA/Parker Solar Probe during the first perihelion. We use a merged FIELDS/Search Coil and Fluxgate Magnetometers data for magnetic field, SWEAP/SPC instrument for ions and RFS/FIELDS quasi thermal noise data for electrons to characterize the plasma environment. The merged magnetic waveforms have 3.4 ms time resolution, which allows us to resolve a wide range of scales, going from MHD inertial range to sub-ion range. We apply a wavelet transform to the magnetic waveforms and we observe localized enhancements in power density that form corresponding peaks in Local Intermittency Measure (LIM) going from MHD to kinetic scales. These LIM peaks are not present in the random-phase signal with the same Fourier amplitudes. This indicates the presence of coherent structures in the observed signal. To detect coherent structures at a given timescale, we use the maximum of the random-phase signal LIM at the same scale as a threshold. We observe a variety of coherent events from MHD to kinetic scales. We estimate the filling factor of the structures as well as their minimum variance properties and local topology. The physical connections between intermittency and solar wind heating are discussed.

How to cite: Vinogradov, A., Alexandrova, O., Artemyev, A., Maksimovic, M., Alexei, V., Petrukovich, A., Bale, S., Issautier, K., and Moncuquet, M.: Young solar wind coherent structures from inertial to sub-ion range, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11561, https://doi.org/10.5194/egusphere-egu21-11561, 2021.

EGU21-11968 | vPICO presentations | ST1.5

Scale dependent anisotropy of electric field fluctuations in solar wind turbulence

Deepali Deepali and Supratik Banerjee

We study the variation of average powers and spectral indices of electric field fluctuations with respect to the angle between average flow direction and the mean magnetic field in solar wind turbulence. Cluster spacecraft data from the years 2002 and 2007 are used for the present analysis. We perform a scale dependent study with respect to the local mean magnetic field using wavelet analysis technique. Prominent anisotropies are found for both the spectral index and power levels of the electric power spectra. Similar to the magnetic field fluctuations, the parallel (or antiparallel) electric fluctuation spectrum is found to be steeper than the perpendicular spectrum. However the parallel (or antiparallel) electric power is found to be greater than the perpendicular one. Below 0.1 Hz, the slope of the parallel electric power spectra deviates substantially from that of the total magnetic power spectra, supporting the existence of Alfvénic turbulence.

How to cite: Deepali, D. and Banerjee, S.: Scale dependent anisotropy of electric field fluctuations in solar wind turbulence, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11968, https://doi.org/10.5194/egusphere-egu21-11968, 2021.

EGU21-12013 | vPICO presentations | ST1.5

Solar type III radio burst fine structure from Langmuir wave motion through turbulent plasma

Eduard Kontar and Hamish Reid
The Sun frequently accelerates near-relativistic electron beams that travel out through the solar corona and interplanetary space. Interacting with their plasma environment, these beams produce type III radio bursts, the brightest astrophysical radio sources detected by humans. The formation and motion of type III fine frequency structures is a puzzle but is commonly believed to be related to plasma turbulence in the solar corona and solar wind. Combining a theoretical framework with kinetic simulations and high-resolution radio type III observations, we quantitatively show that the fine structures are caused by the moving intense clumps of Langmuir waves in a turbulent medium. Our results show how type III fine structure can be used to remotely analyse the intensity and spectrum of compressive density fluctuations, and can infer ambient temperatures in astrophysical plasma, both significantly expanding the current diagnostic potential of solar radio emission.
 

How to cite: Kontar, E. and Reid, H.: Solar type III radio burst fine structure from Langmuir wave motion through turbulent plasma, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12013, https://doi.org/10.5194/egusphere-egu21-12013, 2021.

EGU21-12072 | vPICO presentations | ST1.5

Spectrum of kinetic plasma turbulence at 0.3-0.9 AU from the Sun

Olga Alexandrova, Vamsee Krishna Jagarlamudi, Petr Hellinger, Milan Maksimovic, Yuri Shprits, and Andre Mangeney

We investigate the spectral properties of the turbulence in the solar wind which is a weakly collisional astrophysical plasma, accessible by in-situ observations. Using the Helios search coil magnetometer measurements in the fast solar wind, in the inner heliosphere, we focus on properties of the turbulent magnetic fluctuations at scales smaller than the ion characteristic scales, the so-called kinetic plasma turbulence. At such small scales, we show that the magnetic power spectra between 0.3 and 0.9 AU from the Sun have a generic shape ~f-8/3exp(-f/fd) where the dissipation frequency fd is correlated with the Doppler shifted frequency fρe of the electron Larmor radius. This behavior is statistically significant: all the observed kinetic spectra are well described by this model, with fd=fρe/1.8. These results provide important constraints on the dissipation mechanism in nearly collisionless space plasmas.

How to cite: Alexandrova, O., Krishna Jagarlamudi, V., Hellinger, P., Maksimovic, M., Shprits, Y., and Mangeney, A.: Spectrum of kinetic plasma turbulence at 0.3-0.9 AU from the Sun, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12072, https://doi.org/10.5194/egusphere-egu21-12072, 2021.

EGU21-12092 | vPICO presentations | ST1.5

HelioSwarm: The Nature of Turbulence in Space Plasmas

Harlan Spence, Kristopher Klein, and HelioSwarm Science Team

Recently selected for phase A study for NASA’s Heliophysics MidEx Announcement of Opportunity, the HelioSwarm Observatory proposes to transform our understanding of the physics of turbulence in space and astrophysical plasmas by deploying nine spacecraft to measure the local plasma and magnetic field conditions at many points, with separations between the spacecraft spanning MHD and ion scales.  HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly-collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi-point, multi-scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large-scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind. 

How to cite: Spence, H., Klein, K., and Science Team, H.: HelioSwarm: The Nature of Turbulence in Space Plasmas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12092, https://doi.org/10.5194/egusphere-egu21-12092, 2021.

EGU21-13569 | vPICO presentations | ST1.5

Ion-scale break of the plasma fluctuation spectra in different large-scale solar wind streams

Maria Riazantseva, Liudmila Rakhmanova, Yuri Yermolaev, Irina Lodkina, Georgy Zastenker, Jana Safrankova, Zdenek Nemecek, and Lubomir Prech

Appearance of measurements of the interplanetary medium parameters with high temporal resolution gave rise to a variety of investigations of turbulent cascade at ion kinetic scales at which processes of plasma heating was believed to operate. Our recent studies based on high frequency plasma measurements at Spektr-R spacecraft have shown that the turbulent cascade was not stable and dynamically changed depending on the plasma conditions in different large-scale solar wind structures. These changes was most significant at the kinetic scales of the turbulent cascade. Slow undisturbed solar wind was characterized by the consistency of the spectra to the predictions of the kinetic Alfven wave turbulence model. On the other hand, the discrepancy between the model predictions and registered spectra were found in stream interaction regions characterized by crucial steepening of spectra at the kinetic scales with slopes having values up to -(4-5). This discrepancy was clearly shown for plasma compression region Sheath in front of the magnetic clouds and CIR in front of high speed streams associated with coronal holes. Present study is focused on the break preceding the kinetic scales. Currently the characteristic plasma parameters associated with the formation of the break is still debated. Number of studies demonstrated that the break was consistent with distinct characteristic frequencies for different values ​​of the plasma proton parameter beta βp. Present study consider the ratio between the break frequency determined for ion flux fluctuation spectra according to Spektr-R data and several characteristic plasma frequencies used traditionally in such cases. The value of this ratio is statistically compared for different large-scale solar wind streams. We analyze both the classical spectrum view with two slopes and one break and the spectrum with flattening between magnetohydrodynamic and kinetic scales.  Our results show that for the Sheath and CIR regions characterized typically by βp ≤1 the break corresponds statistically to the frequency determined by the proton gyroradius. At the same time such correspondence are not observed either for the undisturbed slow solar wind with similar βp value or for disturbed flows associated with interplanetary manifestations of coronal mass ejections, where βp << 1. The results also shows that in slow undisturbed solar wind the break is closer to the frequency determined by the inertial proton length. Thus, apparently the transition between streams of different speeds may result in the change of dissipation regimes and plays role in plasma heating at these areas. This work was supported by the RFBR grant No. 19-02-00177a

How to cite: Riazantseva, M., Rakhmanova, L., Yermolaev, Y., Lodkina, I., Zastenker, G., Safrankova, J., Nemecek, Z., and Prech, L.: Ion-scale break of the plasma fluctuation spectra in different large-scale solar wind streams, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13569, https://doi.org/10.5194/egusphere-egu21-13569, 2021.

EGU21-14180 | vPICO presentations | ST1.5

Observing solar wind turbulence in the corona with ground-based radio telescopes

Du Toit Strauss, Gert Botha, James Chibueze, Eduard Kontar, Eugene Engelbrecht, Stefan Lotz, Robert Wicks, Vratislav Krupar, Stuart Bale, Shimul Maharaj, Natasha Jeffrey, Amore Nel, Ruhann Steyn, and Jabus van den Berg

When point-like galactic and extragalactic radio sources are observed through the solar corona by ground-based radio telescopes, plasma density fluctuations in the turbulent solar wind scatter these photons, leading to an observed broadening and/or elongation of such sources. By observing this broadening for several sources, over several days, we can get information about e.g. the wavenumber and radial dependence of solar wind density fluctuations at very small scales (~30m - 8km) inside the Alfven radius, thereby capturing details of the turbulence dissipation range. Here, we present very initial results of such a study with the MeerKAT radio telescope in South Africa (being, of course, a precursor to the much larger Square Kilometer Array, SKA), discuss the preliminary results, and compare these with theoretical estimates and previous observations.

How to cite: Strauss, D. T., Botha, G., Chibueze, J., Kontar, E., Engelbrecht, E., Lotz, S., Wicks, R., Krupar, V., Bale, S., Maharaj, S., Jeffrey, N., Nel, A., Steyn, R., and van den Berg, J.: Observing solar wind turbulence in the corona with ground-based radio telescopes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14180, https://doi.org/10.5194/egusphere-egu21-14180, 2021.

EGU21-14329 | vPICO presentations | ST1.5

Power Anisotropy, Dispersion Signature and Diffusion Region in the 3D Wavenumber Domain of Space Plasma Turbulence

Rong Lin, Jiansen He, Xingyu Zhu, Lei Zhang, Die Duan, Fouad Sahraoui, and Daniel Verscharen

We explore the multi-faceted important features of turbulence (e.g., anisotropy, dispersion, diffusion) in the three-dimensional (3D) wavenumber domain (k, kperp1, kperp2), by employing the k-filtering technique to the high-quality measurements of fields and plasmas from multi-spacecraft constellation (i.e., MMS). We compute the 3D power spectral densities (PSDs) of magnetic and electric fluctuations (marked as PSD(δB(k)) and PSD(δE′‹vi›(k))), both of which show prominent spectral anisotropy in the sub-ion range. We calculate the ratio between PSD(δE′‹vi›(k)) and PSD(δB(k)), the distribution of which is related with nonlinear dispersion relation. We also compute the ratio between electric spectra in different frames of ion flow, that is PSD(δE′local vi)/PSD(δE′‹vi›), to demonstrate the turbulence ion diffusion region (T- IDR) in the wavenumber space. The T-IDR has an anisotropy and a preferential direction of wavevectors, which is generally consistent with the plasma wave theory prediction based on the dominance of kinetic Alfvén wave (KAW). This work manifests the worth of the k-filtering technique in diagnosing turbulence comprehensively, especially when the electric field is involved.

How to cite: Lin, R., He, J., Zhu, X., Zhang, L., Duan, D., Sahraoui, F., and Verscharen, D.: Power Anisotropy, Dispersion Signature and Diffusion Region in the 3D Wavenumber Domain of Space Plasma Turbulence, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14329, https://doi.org/10.5194/egusphere-egu21-14329, 2021.

EGU21-14585 | vPICO presentations | ST1.5

Evolution of the MHD turbulence properties in the inner heliosphere with the PSP/SolO alignment data

Daniele Telloni and the PSP/FIELDS, PSP/SWEAP, SolO/MAG and SolO/SWA/PAS team

Radial alignments between pairs of spacecraft is the only way to observationally investigate the turbulent evolution of the solar wind as it expands throughout interplanetary space. On September 2020 Parker Solar Probe (PSP) and Solar Orbiter (SolO) were nearly perfectly radially aligned, with PSP orbiting around its perihelion at 0.1 au (and crossing the nominal Alfvén point) and SolO at 1 au. PSP/SolO joint observations of the same solar wind plasma allow the extraordinary and unprecedented opportunity to study how the turbulence properties of the solar wind evolve in the inner heliosphere over the wide distance of 0.9 au. The radial evolution of (i) the MHD properties (such as radial dependence of low- and high-frequency breaks, compressibility, Alfvénic content of the fluctuations), (ii) the polarization status, (iii) the presence of wave modes at kinetic scale as well as their distribution in the plasma instability-temperature anisotropy plane are just few instances of what can be addressed. Of furthest interest is the study of whether and how the cascade transfer and dissipation rates evolve with the solar distance, since this has great impact on the fundamental plasma physical processes related to the heating of the solar wind. In this talk I will present some of the results obtained by exploiting the PSP/SolO alignment data.

How to cite: Telloni, D. and the PSP/FIELDS, PSP/SWEAP, SolO/MAG and SolO/SWA/PAS team: Evolution of the MHD turbulence properties in the inner heliosphere with the PSP/SolO alignment data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14585, https://doi.org/10.5194/egusphere-egu21-14585, 2021.

EGU21-14974 | vPICO presentations | ST1.5

Cross helicity of magnetic clouds observed by Parker Solar Probe

Simon Good, Emilia Kilpua, Matti Ala-Lahti, Adnane Osmane, Stuart Bale, and Lingling Zhao

Magnetic clouds are large-scale transient structures in the solar wind with low plasma β, low-amplitude magnetic field fluctuations, and twisted field lines with both ends often connected to the Sun. We analyse the normalised cross helicity, σc, and residual energy, σr, in magnetic clouds observed by Parker Solar Probe (PSP). In the November 2018 cloud observed at 0.25 au, a low value of σc was present in the cloud core, indicating that wave power parallel and anti-parallel to the mean field was approximately balanced, while the cloud’s outer layers displayed larger amplitude Alfvénic fluctuations with high σc values and σr ~ 0. These properties are compared and contrasted to those found in clouds observed by PSP at larger heliocentric distances. We suggest that low σc is likely a common feature of magnetic clouds given their typically closed field structure, in contrast to the generally higher σc found on the open field lines of the solar wind.

How to cite: Good, S., Kilpua, E., Ala-Lahti, M., Osmane, A., Bale, S., and Zhao, L.: Cross helicity of magnetic clouds observed by Parker Solar Probe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14974, https://doi.org/10.5194/egusphere-egu21-14974, 2021.

EGU21-15525 | vPICO presentations | ST1.5

Sounding plasma turbulence at sub-ion scales with Fast Iterative Filtering in space and time.

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

We present the results from a spacetime study of Hall-MHD and Hybrid-kinetic numerical simulations of decaying turbulence. By combining Fourier analysis and Multivariate Iterative Filtering (a new technique developed for the analysis of nonstationary nonlinear signals) we calculate the kω-power spectrum of magnetic, velocity, and density fluctuations at the maximum of turbulent activity. Results show that the magnetic power spectrum at sub-ion scales is formed by localized structures and/or perturbations with temporal frequencies much smaller than the ion-cyclotron frequency Ωi. Going toward smaller ion-kinetic scales, the contribution of low-medium frequency perturbations (ω < 3Ωi) to the magnetic spectrum becomes important. Our analysis clearly indicates that such low-frequency perturbations have no kinetic-Alfvén neither Ion-cyclotron origin. At higher frequencies, we clearly identify signatures of both whistler and kinetic-Alfvén wave activity. However, their energetic contribution to the turbulent cascade is negligible. We conclude that the dynamics of turbulence at sub-ion scales is mainly shaped by localized intermittent structures, with no contribution of wavelike perturbations.

How to cite: Papini, E., Cicone, A., Franci, L., Piersanti, M., Landi, S., Verdini, A., and Hellinger, P.: Sounding plasma turbulence at sub-ion scales with Fast Iterative Filtering in space and time., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15525, https://doi.org/10.5194/egusphere-egu21-15525, 2021.

EGU21-15590 | vPICO presentations | ST1.5

Parametric instability in the expanding solar wind

Andrea Verdini, Roland Grappin, Francesco Malara, Leonardo Primavera, and Luca Del Zanna

Recent measurments of Parker Solar Probe show that alfvenic fluctuations in the solar wind often appear in the form of swithcback with constant total magnetic field. Our aim is to understand if and how such fluctuations can contribute to the heating or acceleration of the solar wind, via the Parametric Instability. The intability of one dimensional Alfvénic fluctuations has been extensively studied in both homogenoeus plasma and in the expanding solar wind, less so for the two-dimensional case which is closer to expected three-dimensional nature of switchbacks. In this work we study under which condition an Alfvén wave with a two dimensional spectrum (as introduced in Primavera et al ApJ 2019) can decay in the expanding solar wind and we will present preliminary results.

How to cite: Verdini, A., Grappin, R., Malara, F., Primavera, L., and Del Zanna, L.: Parametric instability in the expanding solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15590, https://doi.org/10.5194/egusphere-egu21-15590, 2021.

EGU21-16078 | vPICO presentations | ST1.5

Statistical Study of ICW Events and Associated Ion Velocity Distributions in the Inner Heliosphere

Xingyu Zhu, Jiansen He, Daniel Verscharen, Die Duan, Christopher Owen, and Timothy Horbury

Ion cyclotron waves (ICWs) frequently occur in the solar wind and are detected by PSP within 0.3 AU (Bowen et al. 2020), by MESSENGER from 0.3 AU to 0.7 AU (Jian et al. 2010, Boardsen et al. 2015) and by STEREO at 1 AU (Jian et al. 2009; He et al. 2011). However, the relation between the wave properties and the kinetic features of different ion components (proton core, proton beam and helium) are not widely discussed in the existing literature. We statistically analyze the polarization and propagation properties of hundreds of ICW events using measurements from the Solar Orbiter spacecraft. We find three types of ICW events in terms of their occurrence and duration: clustering ICW events with long durations; sporadic ICW events immersed in a quiet background magnetic field; and ICW events alongside discontinuities. We perform an investigation of the ion velocity distribution functions (VDFs) and draw comparisons of the kinetic behavior of each ion component during intervals with and without ICWs. The plasma parameters of the different ion components are acquired by our newly developed fitting program.

How to cite: Zhu, X., He, J., Verscharen, D., Duan, D., Owen, C., and Horbury, T.: Statistical Study of ICW Events and Associated Ion Velocity Distributions in the Inner Heliosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16078, https://doi.org/10.5194/egusphere-egu21-16078, 2021.

ST1.6 – Dynamical processes and particle acceleration associated with current sheets, magnetic islands and turbulence-borne structures in space plasmas

EGU21-421 | vPICO presentations | ST1.6

Unusual enhancement of ~30 MeV proton flux in an ICME sheath region

Mitsuo Oka, Takahiro Obara, Nariaki Nitta, Seiji Yashiro, Daikou Shiota, and Kiyoshi Ichimoto

In gradual Solar Energetic Particle (SEP) events, shock waves driven by coronal mass ejections (CMEs) play a major role in accelerating particles, and the energetic particle flux enhances substantially when the shock front passes by the observer. Such enhancements are historically referred to as Energetic Storm Particle (ESP) events, but it remains unclear why ESP time profiles vary significantly from event to event. In some cases, energetic protons are not even clearly associated with shocks. Here we report an unusual, short-duration proton event detected on 5 June 2011 in the compressed sheath region bounded by an interplanetary shock and the leading-edge of the interplanetary CME (or ICME) that was driving the shock. While <10 MeV protons were detected already at the shock front, the higher-energy (>30 MeV) protons were detected about four hours after the shock arrival, apparently correlated with a turbulent magnetic cavity embedded in the ICME sheath region.

How to cite: Oka, M., Obara, T., Nitta, N., Yashiro, S., Shiota, D., and Ichimoto, K.: Unusual enhancement of ~30 MeV proton flux in an ICME sheath region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-421, https://doi.org/10.5194/egusphere-egu21-421, 2021.

EGU21-3521 | vPICO presentations | ST1.6

Universal scaling of thin current sheets in space plasma

Helmi Malova, Lev Zelenyi, Elena Grigorenko, Victor Popov, and Eduard Dubinin

Thin current sheets (TCSs) with thicknesses about ion Larmor radii can play the key role in space; particularly they can store and then explosively release the accumulated free energy. The dynamics of ions moving along quasi-adiabatic trajectories in TCSs is different from one of magnetized electrons following guiding center drift orbits. Due to this property TCSs can be described in a frame of a hybrid approach. The thickness of the super-thin embedded electron sheet remains uncertain because of the scale-free character of magnetized electron motion. We propose a new analytical approach to describe the multilayer TCS and provide the universal expression describing the embedded electron sheet as a function of the cross-sheet transversal coordinate z characterizing TCS. We demonstrated that the unique property of the electron sheet is the nonlinear character of magnetic field profile:  B(z) ~ z 1/3 which conforms excellently with MAVEN observations in the Martian magnetotail. 

This work was supported by the Russian Science Foundation (grant # 20-42-04418).

 

How to cite: Malova, H., Zelenyi, L., Grigorenko, E., Popov, V., and Dubinin, E.: Universal scaling of thin current sheets in space plasma, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3521, https://doi.org/10.5194/egusphere-egu21-3521, 2021.

EGU21-5595 | vPICO presentations | ST1.6

Spatial evolution of turbulent regions associated with stream interaction regions in the solar wind

Roman Kislov, Timothy Sagitov, and Helmi Malova

High-speed flows from coronal holes are separated from the surrounding solar wind by stream or corotating interaction regions (SIRs/CIRs). The latter have a complex dynamic structure, which is determined by turbulence, the presence of current sheets and magnetic islands/flux ropes/blobs/plasmoids. As the Sun rotates, SIRs along with high-speed flows propagate in the heliosphere. A SIR can be considered as a single large-scale object resembling a magnetic tube with walls of varying thickness. In this case, one can think not only about the speed of the plasma flow inside and near the given object, but also about its movement around the Sun as a whole. Because of this rotation, SIRs can cross the orbits of two separated spacecraft, which may allow one to study the spatial evolution of their structure. We have chosen the events when SIRs were sequentially detected by ACE and one of the STEREO spacecraft. In each case, a position of the Stream Interface (SI) was found, relative to which the position of other structures within the SIR was determined. Using a newly developed method for identifying current sheets [Khabarova et al. 2021], the SIR fine structure and the properties of turbulent plasma flow were studied. The estimates of the angular velocity of rotation SIR around the Sun are given. A model is constructed that describes the motion of SIRs in the heliosphere and their main large-scale properties.

Khabarova O., Sagitov T., Kislov R., Li G. (2021), http://arxiv.org/abs/2101.02804

How to cite: Kislov, R., Sagitov, T., and Malova, H.: Spatial evolution of turbulent regions associated with stream interaction regions in the solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5595, https://doi.org/10.5194/egusphere-egu21-5595, 2021.

Mid-term prognoses of geomagnetic storms require an improvement since theу are known to have rather low accuracy which does not exceed 40% in solar minimum. We claim that the problem lies in the approach. Current mid-term forecasts are typically built using the same paradigm as short-term ones and suggest an analysis of the solar wind conditions typical for geomagnetic storms. According to this approach, there is a 20-60 minute delay between the arrival of a geoeffective flow/stream to L1 and the arrival of the signal from the spacecraft to Earth, which gives a necessary advance time for a short-term prognosis. For the mid-term forecast with an advance time from 3 hours to 3 days, this is not enough. Therefore, we have suggested finding precursors of geomagnetic storms observed in the solar wind. Such precursors are variations in the solar wind density and the interplanetary magnetic field in the ULF range associated with crossings of magnetic cavities in front of the arriving geoeffective high-speed streams and flows (Khabarova et al., 2015, 2016, 2018; Adhikari et al., 2019). Despite some preliminary studies have shown that this might be a perspective way to create a mid-term prognosis (Khabarova 2007; Khabarova & Yermolaev, 2007), the problem of automatization of the prognosis remained unsolved.

How to cite: Fridman, M.: A neural network-based mid-term prognosis of geomagnetic storms that uses pre-storm effects related to current sheets and magnetic islands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8087, https://doi.org/10.5194/egusphere-egu21-8087, 2021.

EGU21-8988 | vPICO presentations | ST1.6

A new multi-year database of current sheets at 1AU

Timofey Sagitov

We announce the first open access multi-year database of current sheets systematically identified with the one second cadence at 1 AU. The current sheet list comes from an automated method of current sheet identification that suggests a formalization of the long-time experience of observers in the visual finding of CSs based on the analysis of the IMF and plasma parameters that vary sharply at CSs of different origins in the solar wind (Behannon et al. 1981; Blanco et al. 2006; Zhang et al. 2008; Suess et al. 2009; Simunac et al. 2012; Zharkova and Khabarova, 2012, 2015; Khabarova et al. 2015, 2016; Khabarova and Zank 2017; Malova at al. 2017; Adhikari et al. 2019). The main features seen with a resolution not worse than one minute that may characterize a CS crossing are as follows: (i) a decrease in the IMF magnitude B, (ii) a decrease in V_A/V (V_A is the Alfvén speed and V is the solar wind speed), and (iii) an increase in the plasma beta (the ratio of the plasma pressure to the magnetic pressure). Since the automatization of the CS recognition process requires setting the same rules for CSs occurring in different plasmas under different conditions, normalization should be performed. After obtaining B, VA/V, and β with a one second cadence, we calculate their one-second derivatives. Spikes of the derivatives occurring out of the noise level indicate the CS location. Only the spikes that appear simultaneously in dB/dt and any of two other parameters are considered as pointing out the CS location. The database is available at csdb dot izmiran dot ru

How to cite: Sagitov, T.: A new multi-year database of current sheets at 1AU, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8988, https://doi.org/10.5194/egusphere-egu21-8988, 2021.

EGU21-9328 | vPICO presentations | ST1.6

The Role of Magnetic Reconnection–associated Processes in Local Particle Acceleration in the Solar Wind

Laxman Adhikari, Gary Zank, and Lingling Zhao

Recent studies of unusual or atypical energetic particle flux events (AEPEs) observed at 1 au show that another mechanism, different from diffusive shock acceleration, can energize particles locally in the solar wind. The mechanism proposed by Zank et al. is based on the stochastic energization of charged particles in regions filled with numerous small-scale magnetic islands (SMIs) dynamically contracting or merging and experiencing multiple magnetic reconnection in the super-Alfvénic solar wind flow. A first- and second-order Fermi mechanism results from compression-induced changes in the shape of SMIs and their developing dynamics. Charged particles can also be accelerated by the formation of antireconnection electric fields. Observations show that both processes often coexist in the solar wind. The occurrence of SMIs depends on the presence of strong current sheets like the heliospheric current sheet (HCS), and related AEPEs are found to occur within magnetic cavities formed by stream–stream, stream–HCS, or HCS–shock interactions that are filled with SMIs. Previous case studies comparing observations with theoretical predictions were qualitative. Here we present quantitative theoretical predictions of AEPEs based on several events, including a detailed analysis of the corresponding observations. The study illustrates the necessity of accounting for local processes of particle acceleration in the solar wind.

How to cite: Adhikari, L., Zank, G., and Zhao, L.: The Role of Magnetic Reconnection–associated Processes in Local Particle Acceleration in the Solar Wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9328, https://doi.org/10.5194/egusphere-egu21-9328, 2021.

We will overview particle motion in 3D Harris-type RCSs without and with magnetic islands using particle-in-cell (PIC) method considering the plasma feedback to electromagnetic fields. We evaluate particle energy gains and pitch angle distributions (PADs) of accelerated particles of both changes in different locations inside current sheets as seen under the different directions by a virtual spacecraft passing through. The RCS parameters are considered comparable to heliosphere and solar wind conditions. 

The energy gains and the PADs of particles are shown to change depending on a topology of magnetic fields.  We report separation of electrons from ions at acceleeration in current sheets with strong guiding fields  and formation of transit and bounced beams from the particles of the same charge. The  transit particles are shown to form  bi-directional energetic electron beams (strahls), while bounced particles are mainly account from driopout fluxes in the heliosphere. In topologies with weak guding field strahls are mainly present inside the magneticislands and located closely above/below the X-nullpoints in the inflow regions. As the guiding field becomes larger, the regions with bi-directional strahls are compressed towards small areas in the exhausts of current sheets. Mono-directional strahls with PADS along 0 or 180 degrees are found quasi-parallel to the magnetic field lines near the X-nullpoint due to the dominant Fermi-type magnetic curvature drift acceleration. Meanwhile, high-energy electrons confined inside magnetic islands create PADs about 90◦. 

How to cite: Zharkova, V. and Xia, Q.: Particle acceleration in 3D current sheets with magnetic islands: energy, density and pitch angle distributions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10352, https://doi.org/10.5194/egusphere-egu21-10352, 2021.

EGU21-10417 | vPICO presentations | ST1.6

Quasi-adiabtic particle dynamics in thin current sheets with a magnetic shear

Victor Popov, Helmi Malova, and Marina Belyalova

The dynamics of quasi-adiabatic ions in thin current sheets (TCSs) of the planetary magnetotails and solar wind is investigated, when the characteristic scale of the magnetic inhomogeneity is compared with proton gyroradii. A numerical model of TCS is constructed, taking into account the constant normal magnetic component and three kind of the shear magnetic field distributions: 1) constant, 2) bell-shaped relatively equatorial plane and 3) anti-symmetric ones. The Poincaré cross- sections characterizing quasi-adiabatic ion dynamics are considered. The jumps of the quasi-adiabatic invariant of motion are calculated and compared with the case of the absent magnetic shear. It is shown that the presence of constant and bell-shaped magnetic components in the current sheet leads to the asymmetry of particle scattering in the Northern-Southern direction and the peculiarities of the structure of phase space. It is shown that the jumps of the quasi-adiabatic Iz invariant differ are different for plasma flows located in the Northern and Southern hemispheres.  At the same time, for configurations with anti-symmetric shear component, the particle scattering near TCS neutral plane is insignificant and the scattering asymmetry is absent. The results of this study are discussed in terms of their application to explain experimental data.

This work is supported by RFBR grant 19-02-00957.

How to cite: Popov, V., Malova, H., and Belyalova, M.: Quasi-adiabtic particle dynamics in thin current sheets with a magnetic shear, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10417, https://doi.org/10.5194/egusphere-egu21-10417, 2021.

EGU21-11947 | vPICO presentations | ST1.6

Dynamics of helium abundance in magnetic clouds

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

Helium is the second most abundant ion component of the solar wind. The relative abundance of helium can differ significantly in various large-scale structures of the solar wind generated by the nonstationarity and inhomogeneity of the solar corona. For example the helium abundance is ~3% in slow streams and ~4% in fast streams. The maximum helium abundance is usually observed inside magnetic clouds and can reach >10%. The relative abundance of helium can also dynamically vary inside large-scale structures, which can be the result of local processes in plasma.

 In magnetic clouds, the distribution of the helium abundance has an axisymmetric peak with a maximum in the central region of the magnetic cloud, where the ion current flows [Yermolaev et al., 2020]. This research examines the different-scale dynamics of the relative abundance of helium in magnetic clouds. For this purpose, the dependences of the helium abundance on some plasma parameters were studied on different datasets of the OMNI database from 1976 to 2018. It is shown that the helium abundance increases with an increase in the modulus of the interplanetary magnetic field B and with a decrease in the proton plasma parameter β in the center of the magnetic cloud. The scale of this region is ~1 million kilometers. Similar relations of the helium abundance to interplanetary magnetic field direction angles and other solar wind parameters were studied.

In addition, the work studied intermediate-scale changes (at scale <1 hour) in helium abundance inside magnetic clouds and compression regions in front of them in comparison with other large-scale wind types. For this aim, a correlation analysis of the time series of density and relative abundance of helium was carried out on base of measurements on SPEKTR-R and WIND spacecraft located at a considerable distance from each other. The dependences of the local correlation coefficients (at scale ~1 hour or less) between measurements at two points on the solar wind plasma parameters are considered. Meanwhile these dependencies are compared with the same for other types of solar wind. It is shown that the median values of the local correlation coefficient in the regions of compressed plasma ahead of magnetic clouds exceed the values in other types of wind by about 15%. In addition, the local correlation coefficient increases with an increase in the amplitude of fluctuations of the investigated parameter and the proton velocity. Thus, intermediate-scale fluctuations in the relative helium abundance observed in these structures are quite stable and apparently are formed in the corona acceleration region and then propagate without changes.
The work is supported by RFBR grant № 19-02-00177a.

References.
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, 125 (7) DOI: 10.1029/2020JA027878

How to cite: Khokhlachev, A., Riazantseva, M., Rakhmanova, L., Yermolaev, Y., and Lodkina, I.: Dynamics of helium abundance in magnetic clouds, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11947, https://doi.org/10.5194/egusphere-egu21-11947, 2021.

Turbulence is ubiquitous in solar system plasmas like those of the solar wind and Earth's magnetosheath. Current sheets can be formed out of this turbulence, and eventually magnetic reconnection can take place in them, a process that converts magnetic into particle kinetic energy. This interplay between turbulence and current sheet formation has been extensively analyzed with MHD and hybrid-kinetic models. Those models cover all the range between large Alfvénic scales down to ion-kinetic scales. The consequences of current sheet formation in plasma turbulence that includes electron dynamics has, however, received comparatively less attention. For this sake we carry out 2.5D fully kinetic Particle-in-Cell simulations of kinetic plasma turbulence including both ion and electron spectral ranges. In order to further assess the electron kinetic effects, we also compare our results with hybrid-kinetic simulations including electron inertia in the generalized Ohm's law. We analyze and discuss the electron and ion energization processes in the current sheets and magnetic islands formed in the turbulence. We focus on the electron and ion distribution functions formed in and around those current sheets and their stability properties that are relevant for the micro-instabilities feeding back into the turbulence cascade. We also compare pitch angle distributions and non-Maxwellian features such as heat fluxes with recent in-situ solar wind observations, which demonstrated local particle acceleration processes in reconnecting solar wind current sheets [Khabarova et al., ApJ, 2020].

How to cite: Munoz, P. A., Büchner, J., and Jain, N.: Fully kinetic PIC simulations of particle acceleration and non-Maxwellian distribution functions due to current sheets in solar wind turbulence, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12010, https://doi.org/10.5194/egusphere-egu21-12010, 2021.

EGU21-12984 | vPICO presentations | ST1.6

Energy Dissipation at Filamentary Structures Downstream of the Earth’s Parallel Bow Shock

Harald Kucharek, Imogen Gingell, Steven Schwartz, Charles Farrugia, and Karlheinz Trattner

While the Earth’s bow shock marks the location at which the solar wind is thermalized, recent publications provided evidence that filamentary structures such as reconnecting current sheets at the shock ramp region may participate in the thermalization process.  Small scale filamentary structures are distinct features that are abundant at the shock and inside the magnetosheath. These structures are not limited to current sheets but include electric and magnetic field enhancements. They may consist of a single or multiple filaments.  They originate from energy dissipation at and downstream of the bow shock, in particular the parallel bow shock. 

We have studied several crossings of the magnetosheath made by the MMS spacecraft, characterising and quantifying the occurrence and consequences of current sheets and field enhancements in terms of local plasma heating and ion acceleration far downstream of the shock. These observations suggest that a combination of current sheet formation, and electric field and magnetic field gradients can contribute to local downstream ion acceleration, and heating. The associated turbulence is likely a consequence of solar wind input parameters. These observations provide evidence that under certain plasma conditions these filamentary structures can play a significant role in thermalizing of the magnetosheath plasma as it propagates further downstream toward the magnetopause, thus augmenting the effect due to the bow shock itself.

How to cite: Kucharek, H., Gingell, I., Schwartz, S., Farrugia, C., and Trattner, K.: Energy Dissipation at Filamentary Structures Downstream of the Earth’s Parallel Bow Shock, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12984, https://doi.org/10.5194/egusphere-egu21-12984, 2021.

EGU21-14838 | vPICO presentations | ST1.6

Spectra of temperature fluctuations in the solar wind

Zdenek Nemecek, Jana Šafránková, Alexander Pitňa, and František Němec

Turbulent cascade transferring the free energy contained within the large scale fluctuations of the magnetic field, velocity and density into the smaller ones is probably one of the most important mechanisms responsible for heating of the solar corona and solar wind and thus the turbulent behavior of these quantities is intensively studied. However, the temperature is also highly fluctuating quantity but behavior of its variations is studied only rarely. There are probably two reasons, first the temperature is tensor and, second, an experimental determination of the temperature variations requires knowledge of the full velocity distribution with a time resolution and such measurements are scarce. To overcome this problem, the Bright Monitor of the Solar Wind (BMSW) on board the Spektr-R spacecraft uses the Maxwellian approximation and provides the thermal velocity with 32 ms time resolution. We use these measurements and complement them with 10 Hz magnetic field observations from the Wind spacecraft propagated to the Spektr-R location and analyze factors influencing the shape of the temperature power spectral density. A special attention is devoted to mutual relations of power spectral densities of different quantities like parallel and perpendicular temperature, magnetic field and velocity fluctuations and their evolution in course of solar wind expansion.

How to cite: Nemecek, Z., Šafránková, J., Pitňa, A., and Němec, F.: Spectra of temperature fluctuations in the solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14838, https://doi.org/10.5194/egusphere-egu21-14838, 2021.

EGU21-14920 | vPICO presentations | ST1.6

Сharged particle acceleration in the CS of the Mercury magnetosphere: comparison of different mechanisms

Elena Zhukova, Victor Popov, Helmi Malova, and Lev Zelenyi

The mechanisms of particle acceleration in the CS of the Mercury magnetosphere were investigated. The numerical model is developed that allows evaluating the acceleration of ions H+, He+, O+ in two possible mechanisms of particle acceleration: (1) by multiple dipolarizations during substorm activity passage of fronts; (2) by the turbulent electromagnetic field in the magnetosphere. Our simulation show that all kinds of charged plasma particles can be efficiently accelerated during multiple dipolarizations processes of the type (2) to maximum energies about 100-200keV. The gain of energies of ions under the (2) process of magnetospheric perturbations is about 10% higher than in the second case. The shapes of obtained in the model energy spectra were shown to be in agreement with experimental spectra. We conclude that the role of these mechanisms is more important near Mercury in comparison with plasma processes in the Earth’s magnetosphere.

How to cite: Zhukova, E., Popov, V., Malova, H., and Zelenyi, L.: Сharged particle acceleration in the CS of the Mercury magnetosphere: comparison of different mechanisms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14920, https://doi.org/10.5194/egusphere-egu21-14920, 2021.

Efficient electron (and ion) acceleration is produced in association with solar flares. Energetic particles play a major role in the active Sun since they contain a large amount of the magnetic energy released during flares. Energetic electrons (and ions) interact with the solar atmosphere and produce high-energy X-rays and γ-rays. Energetic electrons also produce radio emission in a large frequency band through gyrosynchrotron emission processes in the magnetic fields of flaring active regions and conversion of plasma waves when e.g. propagating to the high corona towards the interplanetary medium. It is currently admitted that solar flares are powered by magnetic energy previously stored in the coronal magnetic field and that magnetic energy release is likely to occur on coronal currents sheets along regions of strong gradient of magnetic connectivity. However, understanding the connection between particle acceleration processes and the topology of the complex magnetic structures present in the corona is still a challenging issue. In this talk, we shall review some recent results derived from X-ray and radio imaging spectroscopy of solar flares bringing some new observational constraints on the localization of HXR/radio sources with respect to current sheets, termination shocks in the corona derived from EUV observations.

How to cite: Vilmer, N. and Musset, S.: Energetic electrons in solar flares: observational support for acceleration processes linked to magnetic reconnection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15019, https://doi.org/10.5194/egusphere-egu21-15019, 2021.

EGU21-15163 | vPICO presentations | ST1.6

Transport of energetic particles from reconnecting current sheets in flaring corona to the heliosphere

Philippa Browning, Mykola Gordovskyy, Satashi Inoue, Eduard Kontar, Kanya Kusano, and Gregory Vekstein

In this study, we inverstigate the acceleration of electrons and ions at current sheets in the flaring solar corona, and their transport into the heliosphere. We consider both generic solar flare models and specific flaring events with a data-driven approach. The aim is to answer two questions: (a) what fraction of particles accelerated in different flares can escape into the heliosphere?; and (b) what are the characteristics of the particle populations propagating towards the chromosphere and into the heliosphere?

We use a combination of data-driven 3D magnetohydrodynamics simulations with drift-kinetic particle simulations to model the evolution of the magnetic field and both thermal and non-thermal plasma and to forward-model observable characteristics. Particles are accelerated in current sheets associated with flaring reconnection. When applied to a specific flare, the model successfully predicts observed features such as the location and relative intensity of hard X-ray sources and helioseismic source locations. This confirms the viability of the approach.

Using these MHD-particle models, we will show how the magnetic field evolution and particle transport processes affect the characteristics of both energetic electrons and ions in the the inner corona and the heliosphere. The implications for interpretation of in situ measurements of energetic particles by Solar Orbiter and Parker Solar Probe will be discussed.

 

 

How to cite: Browning, P., Gordovskyy, M., Inoue, S., Kontar, E., Kusano, K., and Vekstein, G.: Transport of energetic particles from reconnecting current sheets in flaring corona to the heliosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15163, https://doi.org/10.5194/egusphere-egu21-15163, 2021.

EGU21-15488 | vPICO presentations | ST1.6

Particle energization inside plasmoids: numerical and analytical investigations

Xiaozhou Zhao, Rony Keppens, and Fabio Bacchini

In an idealized system where four magnetic islands interact in a two-dimensional periodic setting, we follow the detailed evolution of current sheets forming in between the islands, as a result of an enforced large-scale merging by magnetohydrodynamic (MHD) simulation. The large-scale island merging is triggered by a perturbation to the velocity field, which drives one pair of islands move towards each other while the other pair of islands are pushed away from one another. The "X"-point located in the midst of the four islands is locally unstable to the perturbation and collapses, producing a current sheet in between with enhanced current and mass density. Using grid-adaptive resistive magnetohydrodynamic (MHD) simulations, we establish that slow near-steady Sweet-Parker reconnection transits to a chaotic, multi-plasmoid fragmented state, when the Lundquist number exceeds about 3×104, well in the range of previous studies on plasmoid instability. The extreme resolution employed in the MHD study shows significant magnetic island substructures. Turbulent and chaotic flow patters are also observed inside the islands. We set forth to explore how charged particles can be accelerated in embedded mini-islands within larger (monster)-islands on the sheet. We study the motion of the particles in a MHD snapshot at a fixed instant of time by the Test-Particle Module incorporated in AMRVAC (). The planar MHD setting artificially causes the largest acceleration in the ignored third direction, but does allow for full analytic study of all aspects leading to the acceleration and the in-plane, projected trapping of particles within embedded mini-islands. The analytic result uses a decomposition of the test particle velocity in slow and fast changing components, akin to the Reynolds decomposition in turbulence studies. The analytic results allow a complete fit to representative proton test particle simulations, which after initial non-relativistic motion throughout the monster island, show the potential of acceleration within a mini-island beyond (√2/2)c≈0.7c, at which speed the acceleration is at its highest efficiency. Acceleration to several hundreds of GeVs can happen within several tens of seconds, for upward traveling protons in counterclockwise mini-islands of sizes smaller than the proton gyroradius.

How to cite: Zhao, X., Keppens, R., and Bacchini, F.: Particle energization inside plasmoids: numerical and analytical investigations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15488, https://doi.org/10.5194/egusphere-egu21-15488, 2021.

ST1.7 – Theory and Simulation of Solar System Plasmas

EGU21-368 | vPICO presentations | ST1.7

A stochastic solar wind magnetic field model and probing its meandering nature by Energetic Electrons

Gang Li, Nicolas Bian, and Lulu Zhao

Energetic electrons in impulsive events can serve as an ideal probe of solar wind magnetic field. Using a recently developed Fractonal Velocity Dispersion Analysis (FVDA), the release time at the Sun and the path length of interplanetary magnetic field can be obtained with very small uncertainties in many impulsive events. Further knowing the source location, one can examine how much do the field lines deviate from the Parker spiral.  In this work, we present an analytic model for the angular dispersion of magnetic field lines that results from the turbulence in the solar wind and at the solar source surface. The heliospheric magnetic field lines in this  model is derived from a Hamiltonian $H_{\rm m}(\mu, \phi, r)$ in which the pair of canonically conjugated variables the cosine of the heliographic colatitude $\mu$ and the longitude $\phi$. This model naturally incorporates the effect of a random footpoint motion on the source surface since such a motion is due to the zero-frequency component of the solar wind turbulence. Assuming the footpoint motion is also diffusive, it is shown that the angular diffusivity of the stochastic Parker spirals is given by the angular diffusivity of the footpoints divided by the solar wind speed and is controlled by a unique parameter which is the Kubo number. We also present some model calculations of meandering field lines resulting from stochastic footpoint motion and statistical results of the field line path length from observations. Our model and statistical results can shed lights on observations made by Parker Solar Probe and Solar Orbiter.

 

 

How to cite: Li, G., Bian, N., and Zhao, L.: A stochastic solar wind magnetic field model and probing its meandering nature by Energetic Electrons, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-368, https://doi.org/10.5194/egusphere-egu21-368, 2021.

EGU21-662 | vPICO presentations | ST1.7

Hunting for reconnection and energy exchange sites in 3D turbulent outflows

Giovanni Lapenta

Plasma turbulence is typically characterized by a preferred directon, that of teh magnetic field. Most plasmas have a coherent average field component and turbulence develop over it. Tokamaks are teh archetypical case with their strong toroidal field. But also solar arcades, solr wind, magnetospheres and ionospheres have that same property. We consider here turbulence in 3D reconnection outflows. Reconnection often has a gudie field to begin with, but even without it, in the outflow there is a significant field residual from the process of reconnection. This macroscopic field organizes the plasma turbulence to form a very anistotropic state. We recenlty, investigted the properties of turbulence at different locations [1]. We deploy now innovative machine learning tools to investigate the outflows and detect the presence of secondary reconnection sites and regions of energy exchange.

[1] Lapenta, G., et al. "Local regimes of turbulence in 3D magnetic reconnection." The Astrophysical Journal 888.2 (2020): 104.

Work supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 776262 (AIDA, www.aida-space.eu).

How to cite: Lapenta, G.: Hunting for reconnection and energy exchange sites in 3D turbulent outflows, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-662, https://doi.org/10.5194/egusphere-egu21-662, 2021.

EGU21-1973 | vPICO presentations | ST1.7

Preprocessing of magnetograms for magnetohydrostatic extrapolations

Xiaoshuai Zhu, Thomas Wiegelmann, and Bernd Inhester

Magnetohydrostatic (MHS) extrapolations are developed to model 3D magnetic fields and plasma structures in the solar low atmosphere by using measured vector magnetic fields on the photosphere. However, the photospheric magnetogram may be inconsistent with the MHS assumption. By applying Gauss‘ theorem to an isolated active region, we obtain a set of surface integrals of the magnetogram as criteria for a MHS system. The integrals are a subset of Aly’s criteria for a force-free field (FFF). Based on the new criteria, we preprocess the magnetogram to make it more consistent with the MHS assumption and, at the same time, close to the original data. As a byproduct, we also find the boundary integral that is used to compute the energy of a FFF usually underestimates the magnetic energy of an active region.

How to cite: Zhu, X., Wiegelmann, T., and Inhester, B.: Preprocessing of magnetograms for magnetohydrostatic extrapolations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1973, https://doi.org/10.5194/egusphere-egu21-1973, 2021.

EGU21-4713 | vPICO presentations | ST1.7

Vortices evolution in ideal (M)HD

José Roberto Canivete Cuissa and Oskar Steiner

Vortices and vortex tubes are ubiquitous in the solar atmosphere and space plasma. In order to identify vortices and to study their evolution, we seek a suitable mathematical criterium for which a dynamical equation exists. So far, the only option available is given by the vorticity, which however is not the optimal criterion since it can be biased by shear flows. Therefore, we look at another criterion, the swirling strength, for which we found an evolution equation, which we suggest as a novel tool for the analysis of vortex dynamics in (magneto-)hydrodynamics. We highlight a few results obtained by applying the swirling strength and its dynamical equation to simulations of the solar atmosphere.

How to cite: Canivete Cuissa, J. R. and Steiner, O.: Vortices evolution in ideal (M)HD, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4713, https://doi.org/10.5194/egusphere-egu21-4713, 2021.

EGU21-5152 | vPICO presentations | ST1.7

The formation and evolution of the electron strahl in the inner heliosphere

Seong-Yeop Jeong, Daniel Verscharen, Vocks Christian, Christopher Owen, Robert Wicks, and Andrew Fazakerley

The electrons in the solar wind exhibit an interesting kinetic substructure with many important implications for the overall energetics of the plasma in the heliosphere. We are especially interested in the formation and evolution of the electron strahl, a field-aligned beam of superthermal electrons, in the heliosphere. We develop a kinetic transport equation for typical heliospheric conditions based on a Parker-spiral geometry of the magnetic field. We present the results of our theoretical model for the radial evolution of the electron velocity distribution function (VDF) in the solar wind. We study the effects of the adiabatic focusing of energetic electrons, wave-particle interactions, and Coulomb collisions through a generalized kinetic equation for the electron VDF. We compare and contrast our results with the observed effects in the electron VDFs from space missions that explore the radial evolution of electrons in the inner heliosphere such as Helios, Parker Solar Probe, and Solar Orbiter.

How to cite: Jeong, S.-Y., Verscharen, D., Christian, V., Owen, C., Wicks, R., and Fazakerley, A.: The formation and evolution of the electron strahl in the inner heliosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5152, https://doi.org/10.5194/egusphere-egu21-5152, 2021.

EGU21-6858 | vPICO presentations | ST1.7

Feasibility of Ion-cyclotron Resonant Heating in the Solar Wind

Roberto E. Navarro, Victor Muñoz, Juan A. Valdivia, and Pablo S. Moya

Wave-particle interactions are believed to be one of the most important kinetic processes regulating the heating and acceleration of Solar Wind plasma. One possible explanation to the observed preferential heating of alpha (He+2) ions relies on a process similar to a second order Fermi acceleration mechanism. In this model, heavy ions are able to resonate with multiple counter-propagating ion-cyclotron waves, while protons can encounter only single resonances, resulting in the subsequent preferential energization of minor ions. In this work, we address and test this idea by calculating the number of plasma particles that are resonating with ion-cyclotron waves propagating parallel and anti-parallel to an ambient magnetic field in a proton/alpha plasma with cold electrons. Resonances are calculated through the proper kinetic multi-species dispersion relation of Alfven waves. We show that 100% of the alpha population can resonate with counter-propagating waves below a threshold ΔUαp/vA<U0+a(β+β0)b in the differential streaming between protons and alpha particles, where U0=-0.532, a=1.211, β0=0.0275, and b=0.348 for isotropic ions. This threshold seems to match with constraints of the observed ΔUαp in the Solar Wind for low values of the proton plasma beta. Finally, it is also shown that this process is limited by the growth of plasma kinetic instabilities, a constraint that could explain alpha-to-proton temperature ratio observations in the Solar Wind at 1 AU.

How to cite: Navarro, R. E., Muñoz, V., Valdivia, J. A., and Moya, P. S.: Feasibility of Ion-cyclotron Resonant Heating in the Solar Wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6858, https://doi.org/10.5194/egusphere-egu21-6858, 2021.

EGU21-7156 | vPICO presentations | ST1.7

Fluid model of the plasma flow in the magnetic tail of a planet

Filippo Pantellini

All planets of the solar system with an active internal dynamo have a their magnetic dipole oriented perpendicularly or nearly perpendicularly to the solar wind during all or part of their orbit  around the Sun. If, in addition, the planetary rotation is slow, or if the angle between dipole and rotation axis is large, planetary field lines crossing the antisolar axis can become stretched to large distances downstream of the planet. Examples where this may occur are Mercury and Uranus at solstice time, respectively. 

Inspired by these examples, we present a tentative one-dimensional magnetohydrodynamic model of the plasma flowing along the antisolar direction. 

Assuming that the radius of curvature R(z) of the planetary field lines is defined locally as R=D/D', where D(z) is a characteristic  transverse scale of the magnetosphere at a distance z downstream of the planet,  we obtain that the plasma velocity u(z) obeys to a Hugoniot type equation  (M2-1) u'/u =  D'/D,  where M=u/vA is the Alfvén Mach number. 

The solution for a typical profile D(z) will be discussed. 

How to cite: Pantellini, F.: Fluid model of the plasma flow in the magnetic tail of a planet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7156, https://doi.org/10.5194/egusphere-egu21-7156, 2021.

EGU21-7565 | vPICO presentations | ST1.7

Cumulative instabilities of anisotropic protons and electrons in the solar wind: New insights from a quasilinear approach

Shaaban Mohammed Shaaban Hamd, Marian Lazar, Rodrigo R. López, Robert F. Wimmer-Schweingruber, and Horst Fichtner

In collision-poor space plasmas the main physical processes are governed by fluctuations and their interactions with plasma particles. An important source of waves and coherent fluctuations are kinetic instabilities driven by, e.g., protons and electrons exhibiting temperature anisotropies. Unfortunately, such instabilities are generally investigated independently of each other, thereby ignoring their interplay and preventing a realistic treatment of their implications. Here we present the first results of an extended quasilinear approach, which not only confirms linear predictions but also unveils new regimes triggered by cumulative effects of the proton and electron instabilities (e.g., electromagnetic cyclotron, firehose). By comparison to individual excitations combined proton- and electron-induced fluctuations grow and saturate at different intensities as well as different temporal scales in the quasilinear phase. Moreover, the enhanced wave fluctuations can markedly stimulate or inhibit the relaxation of temperature anisotropies, this way highly conditioning the evolution and saturation of instabilities.

How to cite: Hamd, S. M. S., Lazar, M., López, R. R., Wimmer-Schweingruber, R. F., and Fichtner, H.: Cumulative instabilities of anisotropic protons and electrons in the solar wind: New insights from a quasilinear approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7565, https://doi.org/10.5194/egusphere-egu21-7565, 2021.

EGU21-7970 | vPICO presentations | ST1.7

ULF wave transmission across collisionless shocks: 2.5D local hybrid simulations

Primož Kajdič, Yann Pfau-Kempf, Lucile Turc, Andrew Dimmock, and Minna Palmroth

We study the interaction of upstream ultra-low frequency (ULF) waves with collisionless shocks by analyzing the outputs of eleven 2.5D local hybrid simulation models. Our simulated shocks have Alfvénic Mach numbers between 4.29-7.42 and their θBN angles are 15º, 30º, 45º and 50º. Thus all are quasi-parallel or marginally quasi-perpendicular shocks. Upstream of all of the shocks the ULF wave foreshock develops. It is populated by transverse and compressive ULF magnetic field fluctuations that propagate upstream in the rest frame of upstream plasma. We show that the properties of the upstream waves reflect on the properties of the shock ripples. We also show that due to these ripples, as different portions of upstream waves reach the shocks, they encounter shock sections with different properties, such as the downstream magnetic field and the orientation of the local shock normals. This means that the waves are not simply transmitted into the downstream region but are heavily processed by the shocks. The identity of upstream fluctuations is largely lost, since the downstream fluctuations do not resemble the upstream waves in their shape, waveform extension, orientation nor in their wavelength. However some features are conserved. For example, the Fourier spectra of upstream waves present a bump or flattening at wavelengths corresponding to those of the upstream ULF waves. Most of the corresponding compressive downstream spectra also exhibit these features, while transverse downstream spectra are largely featureless.

How to cite: Kajdič, P., Pfau-Kempf, Y., Turc, L., Dimmock, A., and Palmroth, M.: ULF wave transmission across collisionless shocks: 2.5D local hybrid simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7970, https://doi.org/10.5194/egusphere-egu21-7970, 2021.

EGU21-8369 | vPICO presentations | ST1.7

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

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

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 force and of the 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 heavy ions are heated by Alfvén waves, which then heat up the electrons via collision processes. We show preliminary results on composition distribution along a typical coronal loop and compare with typical 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., Indurain, M., Blelly, P.-L., Réville, V., Verdini, A., Velli, M., and Buchlin, E.: Simulating the FIP effect in coronal loops using a multi-species kinetic-fluid model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8369, https://doi.org/10.5194/egusphere-egu21-8369, 2021.

EGU21-8671 | vPICO presentations | ST1.7

The Dispersion Diagram for Magnetoacoustic Waves in Arbitrarily Structured Solar Waveguides

Samuel Skirvin, Viktor Fedun, and Gary Verth

The observation of large scale stable solar magnetic configurations, e.g. sunspots have been done over centuries. But only recently, thanks to modern high-resolution observations solar physicists were able to observe small scale solar features and associated plasma processes, i.e. magnetic bright points, spicules, plasma flows, structure of magnetic fields etc. in great detail. Therefore, advanced theoretical modelling becomes essential to explain observational results, allowing magneto-seismology to be conducted and provide more accurate information about MHD wave propagation and solar atmospheric plasma properties. In this work, we discuss a variety of theoretically constructed 2-3D MHD equilibria obtained by considering different magnetic field configurations and internal flow profiles. The dispersion diagrams and eigenfunctions were obtained numerically for the case where the equilibrium plasma density is modelled as a Gaussian profile with a varying inhomogeneous width and also as a sinc(x) function. The analytic dispersion relation is not required, making this numerical approach a very powerful tool. The proposed numerical approach allows the dispersion diagram and eigenfunctions to be obtained for any inhomogeneous magnetic hydrostatic equilibrium with or without plasma flow. To obtain the numerical solution, the shooting method has been used to match necessary boundary conditions on continuity of displacement and total pressure of the waveguide. The proposed methodology has been successfully tested against well-known analytical results obtained for uniform slab and uniform cylinder geometry. We have found that under coronal conditions, with increasing inhomogeneity in the equilibrium, an additional node appears in the resulting eigenfunctions for the slow body sausage mode, which could be misinterpreted by observers as the existence of an entirely different mode.

How to cite: Skirvin, S., Fedun, V., and Verth, G.: The Dispersion Diagram for Magnetoacoustic Waves in Arbitrarily Structured Solar Waveguides, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8671, https://doi.org/10.5194/egusphere-egu21-8671, 2021.

EGU21-9050 | vPICO presentations | ST1.7

Structure functions analysis of sub-ion scale turbulent fluctuations and dissipation range in a magnetized plasma

Giuseppe Arrò, Francesco Califano, and Giovanni Lapenta

Turbulence in collisionless magnetized plasmas is a complex multi-scale process involving many decades of scales ranging from large magnetohydrodynamic (MHD) scales down to small ion and electron kinetic scales, associated with different physical regimes. It is well know that the MHD turbulent cascade is driven by the nonlinear interaction of low-frequency Alfvén waves but, on the other hand, the properties of plasma turbulence at sub-ion scales are not yet fully understood. In addition to a great variety of relatively high frequency modes such as kinetic Alfvén waves and whistler waves, magnetic reconnection has been suggested to be a key element in the development of kinetic scale turbulence because it allows for energy to be transferred from large scales directly into sub-ion scales through currents sheets disruption. In this context, an unusual reconnection mechanism driven exclusively by the electrons (with ions being demagnetized), called "electron-only reconnection", has been recently observed for the first time in the Earth’s magnetosheath and its role in plasma turbulence is still a matter of great debate.

Using 2D-3V hybrid Vlasov-Maxwell (HVM) simulations of freely decaying plasma turbulence, we investigate and compare the properties of the turbulence associated with standard ion-coupled reconnection and of the turbulence associated with electron-only reconnection [Califano et al., 2018]. By analyzing the structure functions of the turbulent magnetic field and ion fluid velocity fluctuations, we find that the turbulence associated with electron-only reconnection shows the same statistical features as the turbulence associated with standard ion-coupled reconnection and no peculiar signature related to electron-only reconnection is found in the turbulence statistics. This result suggests that the properties of the turbulent cascade in a magnetized plasma are independent of the specific mechanism associated with magnetic reconnection but depend only on the coupling between the magnetic field and the different particle species present in the system. Finally, the properties of the magnetic field dissipation range are discussed as well and we claim that its formation, and thus the dissipation of magnetic energy, is driven only by the small scale electron dynamics since ions are demagnetized in this range [Arró et al., 2020].

This work has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement No 776262 (AIDA, www.aida-space.eu).

References:

G. Arró, F. Califano, and G. Lapenta. Statistical properties of turbulent fluctuations associated with electron-only magnetic reconnection. , 642:A45, Oct. 2020. doi: 10.1051/0004-6361/202038696.

F. Califano, S. S. Cerri, M. Faganello, D. Laveder, M. Sisti, and M. W. Kunz. Electron-only magnetic reconnection in plasma turbulence. arXiv e-prints, art. arXiv:1810.03957, Oct. 2018.

How to cite: Arrò, G., Califano, F., and Lapenta, G.: Structure functions analysis of sub-ion scale turbulent fluctuations and dissipation range in a magnetized plasma, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9050, https://doi.org/10.5194/egusphere-egu21-9050, 2021.

UV bursts and Ellerman bombs are transient brightenings observed in the low solar atmospheres of emerging flux regions. Observations have discovered the cospatial and cotemporal EBs and UV bursts, and their formation mechanisms are still not clear. The multi-thermal components with a large temperature span in these events challenge our understanding of magnetic reconnection and heating mechanisms in the low solar atmosphere. We have studied magnetic reconnection between the emerging and background magnetic fields. The initial plasma parameters are based on the C7 atmosphere model. After the current sheet with dense photosphere plasma is emerged to 0.5 Mm above the solar surface, plasmoid instability appears. The plasmoids collide and coalesce with each other, which makes the plasmas with different densities and temperatures mixed up in the turbulent reconnection region. Therefore, the hot plasmas corresponding to the UV emissions and colder plasmas corresponding to the emissions from other wavelenghts can move together and occur at about the same height. In the meantime, the hot turbulent structures basically concentrate above 0.4 Mm, whereas the cool plasmas extend to much lower heights to the bottom of the current sheet. These phenomena are consistent with the observations of Chen et al. 2019, ApJL. The synthesized Si IV line profiles are similar to the observed one in UV bursts, the enhanced wing of the line profiles can extend to about 100 km s1. The differences are significant among the numerical results with different resolutions, which indicate that the realistic magnetic diffusivity is crucial to reveal the fine structures and realistic plasmas heating in these reconnection events. Our results also show that the reconnection heating contributed by ambipolar diffusion in the low chromosphere around the temperature minimum region is not efficient.

How to cite: Ni, L.: A magnetic reconnection model for hot explosions in the cool atmosphere of the Sun, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9153, https://doi.org/10.5194/egusphere-egu21-9153, 2021.

EGU21-9193 | vPICO presentations | ST1.7

Improving CME evolution and arrival predictions with AMR and grid stretching in EUHFORIA

Tinatin Baratashvili, Christine Verbeke, Nicolas Wijsen, Emmanuel Chané, and Stefaan Poedts

Coronal Mass Ejections (CMEs) are the main drivers of interplanetary shocks and space weather disturbances. Strong CMEs directed towards Earth can cause severe damage to our planet. Predicting the arrival time and impact of such CMEs can enable to mitigate the damage on various technological systems on Earth. 

We model the inner heliospheric solar wind and the CME propagation and evolution within a new heliospheric model based on the MPI-AMRVAC code. It is crucial for such a numerical tool to be highly optimized and efficient, in order to produce timely forecasts. Our model solves the ideal MHD equations to obtain a steady state solar wind configuration in a reference frame corotating with the Sun. In addition, CMEs can be modelled by injecting a cone CME from the inner boundary (0.1 AU).

Advanced techniques, such as grid stretching and Adaptive Mesh Refinement (AMR) are employed in the simulation. Such methods allow for high(er) spatial resolution in the numerical domain, but only where necessary or wanted. As a result, we can obtain a detailed, highly resolved image at the (propagating) shock areas, without refining the whole domain.

These techniques guarantee more efficient simulations, resulting in optimised computer memory usage and a significant speed-up. The obtained speed-up, compared to the original approach with a high-resolution grid everywhere, varies between a factor of 45 - 100 depending on the domain configuration. Such efficiency gain is momentous for the mitigation of the possible damage and allows for multiple simulations with different input parameters configurations to account for the uncertainties in the measurements to determine them. The goal of the project is to reproduce the observed results, therefore, the observable variables, such as speed, density, etc., are compared to the same type of results produced by the existing (non-stretched, single grid) EUropean Heliospheric FORecasting Information Asset (EUHFORIA) model and observational data for a particular event on 12th of July, 2012. The shock features are analyzed and the results produced with the new heliospheric model are in agreement with the existing model and observations, but with a significantly better performance. 

 

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Baratashvili, T., Verbeke, C., Wijsen, N., Chané, E., and Poedts, S.: Improving CME evolution and arrival predictions with AMR and grid stretching in EUHFORIA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9193, https://doi.org/10.5194/egusphere-egu21-9193, 2021.

EGU21-9219 | vPICO presentations | ST1.7

Thin current sheets as key structures in space plasma

Helmi Malova, Lev Zelenyi, Victor Popov, and Elena Grigorenko

Plasma structures with extremely small transverse size (named thin current sheets or TCSs) have been discovered and investigated by spacecraft observations in the Earth's magnetotail, then in other planetary magnetospheres and the solar wind. Their formation is related with complicated dynamic processes in collisionless space plasma near the magnetic reconnection regions. The proposed models describing TCSs in space plasma, based on the assumption of a quasi-adiabatic proton dynamics and magnetized electrons were successful. Various modifications of the initial equilibrium allowed describing such current sheets as the system of current sheets where the central sheet is supported by magnetized electron drifts, and the external sheets are supported by quasi-adiabatic protons and sometimes oxygen ions. Such current configurations are shown to have properties that are completely different from the well-known Harris model, particularly the multiscale structure, embedding and metastability. The structure and evolution of TCSs under the tearing mode as well as the related paradox of complete tearing mode stabilization in configurations with a nonzero normal magnetic field component is highlighted.

This work is supported by the Russian Science Foundation grant № 20-42-04418.

How to cite: Malova, H., Zelenyi, L., Popov, V., and Grigorenko, E.: Thin current sheets as key structures in space plasma, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9219, https://doi.org/10.5194/egusphere-egu21-9219, 2021.

EGU21-9329 | vPICO presentations | ST1.7

Plasma instabilities driven by pickup ions of ring-beam velocity distributions in the outer heliosheath 

Ameneh Mousavi, Kaijun Liu, and Sina Sadeghzadeh

The stability of the pickup ions in the outer heliosheath has been studied by many researchers because of its relevance to the energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary EXplorer. However, previous studies are primarily limited to pickup ions of near 90° pickup angles, the angle between the pickup ion injection velocity and the background, local interstellar magnetic field. Investigations on pickup ions of smaller pickup angles are still lacking. In this paper, linear kinetic dispersion analysis and hybrid simulations are carried out to examine the plasma instabilities driven by pickup ions of ring-beam velocity distributions at various pickup angles between zero and 90°. Parallel propagating waves are studied in the parameter regime where the parallel thermal spread of the pickup ions falls into the Alfvén cyclotron stability gap. The linear analysis results and hybrid simulations both show that the fastest growing modes are the right-hand helicity waves propagating in the direction of the background magnetic field, and the maximum growth rate occurs at the pickup angle of 82°. The simulation results further reveal that the saturation level of the fluctuating magnetic fields for pickup angles below 45° is higher than that for pickup angles above 45°. So, the scattering of pickup ions at near zero pickup angles is likely more pronounced than that at near 90° pickup angles .

How to cite: Mousavi, A., Liu, K., and Sadeghzadeh, S.: Plasma instabilities driven by pickup ions of ring-beam velocity distributions in the outer heliosheath , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9329, https://doi.org/10.5194/egusphere-egu21-9329, 2021.

EGU21-9368 | vPICO presentations | ST1.7

Multiple Boris solvers for particle-in-cell (PIC) simulation

Seiji Zenitani and Tsunehiko Kato

 Particle-in-cell (PIC) simulation has long been used in theoretical plasma physics. In PIC simulation, the Boris solver is the de-facto standard for solving particle motion, and it has been used over a half century. Meanwhile, there is a continuous demand for better particle solvers. In this contribution, we introduce a family of Boris-type schemes for integrating the motion of charged particles. We call the new solvers the multiple Boris solvers. The new solvers essentially repeat the standard two-step procedure multiple times in the Lorentz-force part, and we derive a single-step form for arbitrary subcycle number n. The new solvers give n2 times smaller errors, allow larger timesteps, but they are computationally affordable for moderate n. The multiple Boris solvers also reduce a numerical error in long-term plasma motion in a relativistic magnetized flow.

Reference:

  • S. Zenitani & T. N. Kato, Multiple Boris integrators for particle-in-cell simulation, Comput. Phys. Commun. 247, 106954, doi:10.1016/j.cpc.2019.106954 (2020)

How to cite: Zenitani, S. and Kato, T.: Multiple Boris solvers for particle-in-cell (PIC) simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9368, https://doi.org/10.5194/egusphere-egu21-9368, 2021.

EGU21-10464 | vPICO presentations | ST1.7

Structure of current sheets formed in collisionless plasma turbulence

Neeraj Jain, Joerg Buechner, Patricio Munoz, and Lev M. Zelenyi

Plasma turbulence is ubiquitous in space and astrophysical environments and believed to play important role in a variety of space and astrophysical phenomena ranging from the entry of  energetic particles in Earth's magnetic environment and non-adiabatic heating of the solar wind plasma to star formation in inter stellar medium. Space and astrophysical plasmas are usually magnetized and collisionless. An unsolved problem in turbulent collisionless plasmas, e.g., the solar wind, is the mechanism of dissipation of macroscopic energy into heat without collisional dissipation. A number of observational and simulation studies show that kinetic sale current sheets formed self-consistently in collisionless plasma turbulence are the sites of the dissipation. Mechanisms of dissipation in current sheets are, however,  not well understood. Free energy sources in and equilibrium structure of current sheets are important factors in the determination of the dissipation mechanism. Recent PIC hybrid simulations (with mass-less electrons) of collisionless plasma turbulence show that current sheets thin down to below ion inertial length with current carried mainly by electrons. This can lead  to embedded current sheet structure which was recently studied analytically.  We carry out 2-D PIC-hybrid simulations (with finite-mass electrons) using a recently developed code CHIEF to study the free energy sources and structure of current sheets formed in turbulence. In this paper, we focus on  the spatial gradient driven free energy sources and embedded structure of current sheets.  The results are compared to the results obtained from hybrid simulations with mass-less electrons. 

How to cite: Jain, N., Buechner, J., Munoz, P., and Zelenyi, L. M.: Structure of current sheets formed in collisionless plasma turbulence, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10464, https://doi.org/10.5194/egusphere-egu21-10464, 2021.

EGU21-10493 | vPICO presentations | ST1.7

A Fundamental Mechanism of Solar Eruption Initiation

Chaowei Jiang, Xueshang Feng, Rui Liu, Xiaoli Yan, Qiang Hu, and Ronald L. Moore

Solar eruptions are spectacular magnetic explosions in the Sun's corona and how they are initiated remains unclear. Prevailing theories often rely on special magnetic topologies, such as magnetic flux rope and magnetic null point, which, however, may not generally exist in the pre-eruption source region of corona. Here using fully three-dimensional magnetohydrodynamic simulations with high accuracy, we show that solar eruption can be initiated in a single bipolar configuration with no additional special topology. Through photospheric shearing motion alone, an electric current sheet forms in the highly sheared core field of the magnetic arcade during its quasi-static evolution. Once magnetic reconnection sets in, the whole arcade is expelled impulsively, forming a fast-expanding twisted flux rope with a highly turbulent reconnecting region underneath. The simplicity and efficacy of this scenario argue strongly for its fundamental importance in the initiation of solar eruptions.

How to cite: Jiang, C., Feng, X., Liu, R., Yan, X., Hu, Q., and Moore, R. L.: A Fundamental Mechanism of Solar Eruption Initiation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10493, https://doi.org/10.5194/egusphere-egu21-10493, 2021.

EGU21-10978 | vPICO presentations | ST1.7

Thin current sheets of sub-ion scales observed in planetary magnetotails

Elena Grigorenko, Makar Leonenko, Lev Zelenyi, Helmi Malova, and Victor Popov

Current sheets (CSs) play a crucial role in the storage and conversion of magnetic energy in planetary magnetotails. Spacecraft observations in the terrestrial magnetotail reported that the CS thinning and intensification can result in formation of multiscale current structure in which a very thin and intense current layer at the center of the CS is embedded into a thicker sheet. To describe such CSs fully kinetic description taking into account all peculiarities of non-adiabatic particle dynamics is required. Kinetic description brings kinetic scales to the CS models. Ion scales are controlled by thermal ion Larmor radius, while scales of sub-ion embedded CS are controlled by the topology of magnetic field lines until the electron motion is magnetized by a small component of the magnetic field existing in a very center of the CS. MMS observations in the Earth magnetotail as well as MAVEN observations in the Martian magnetotail with high time resolution revealed the formation of similar multiscale structure of the cross-tail CS in spite of very different local plasma characteristics. We revealed that the typical half‐thickness of the embedded Super Thin Current Sheet (STCSs) observed at the center of the CS in the magnetotails of both planets is much less than the gyroradius of thermal protons. The formation of STCS does not depend on ion composition, density and temperature,  but it is controlled by the small value of the normal component of the magnetic field at the neutral plane. Our analysis showed that there is a good agreement between the spatial scaling of multiscale CSs observed in both magnetotails and the scaling predicted by the quasi-adiabatic model of thin anisotropic CS taking into account the coupling between ion and electron currents. Thus, in spite of the significant differences in the CS formation, ion composition, and plasma characteristics in the Earth’s and Martian magnetotails, similar kinetic features are observed in the CS structures in the magnetotails of both planets. This phenomenon can be explained by the universal principles of nature. The CS once has been formed, then it should be self-consistently supported by the internal coupling of the total current carried by particles in the CS and its magnetic configuration, and as soon as the system achieved the quasi-equilibrium state, it “forgets” the mechanisms of its formation, and its following existence is ruled by the general principles of plasma kinetic described by Vlasov–Maxwell equations.

This work is supported by the Russian Science Foundation grant № 20-42-04418

How to cite: Grigorenko, E., Leonenko, M., Zelenyi, L., Malova, H., and Popov, V.: Thin current sheets of sub-ion scales observed in planetary magnetotails, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10978, https://doi.org/10.5194/egusphere-egu21-10978, 2021.

EGU21-11005 | vPICO presentations | ST1.7

Global coronal and heliospheric magnetic field modelling for Solar Orbiter

Thomas Wiegelmann, Thomas Neukirch, Iulia Chifu, and Bernd Inhester

Computing the solar coronal magnetic field and plasma
environment is an important research topic on it's own right
and also important for space missions like Solar Orbiter to
guide the analysis of remote sensing and in-situ instruments.
In the inner solar corona plasma forces can be neglected and
the field is modelled under the assumption of a vanishing
Lorentz-force. Further outwards (above about two solar radii)
plasma forces and the solar wind flow has to be considered.
Finally in the heliosphere one has to consider that the Sun
is rotating and the well known Parker-spiral forms.
We have developed codes based on optimization principles
to solve nonlinear force-free, magneto-hydro-static and
stationary MHD-equilibria. In the present work we want to
extend these methods by taking the solar rotation into account.

How to cite: Wiegelmann, T., Neukirch, T., Chifu, I., and Inhester, B.: Global coronal and heliospheric magnetic field modelling for Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11005, https://doi.org/10.5194/egusphere-egu21-11005, 2021.

EGU21-11065 | vPICO presentations | ST1.7

Turbulence driven by chromospheric evaporations in solar flares

Wenzhi Ruan, Chun Xia, and Rony Keppens

Chromospheric evaporations are frequently observed at the footpoints of flare loops in flare events. The evaporations flows driven by thermal conduction or fast electron deposition often have high speed of hundreds km/s. Since the speed of the observed evaporation flows is comparable to the local Alfven speed, it is reasonable to consider the triggering of Kelvin-Helmholtz instabilities. Here we revisit a scenario which stresses the importance of the Kelvin-Helmholtz instability (KHI) proposed by Fang et al. (2016). This scenario suggests that evaporations flows from two footpoints of a flare loop can meet each other at the looptop and produce turbulence there via KHI. The produced KHI turbulence can play important roles in particle accelerations and generation of strong looptop hard X-ray sources. We investigate whether evaporation flows can produce turbulence inside the flare loop with the help of numerical simulation. KHI turbulence is successfully produced in our simulation. The synthesized soft X-ray curve demonstrating a clear quasi-periodic pulsation (QPP) with period of 26 s. The QPP is caused by a locally trapped, fast standing wave that resonates in between KHI vortices.

How to cite: Ruan, W., Xia, C., and Keppens, R.: Turbulence driven by chromospheric evaporations in solar flares, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11065, https://doi.org/10.5194/egusphere-egu21-11065, 2021.

EGU21-11078 | vPICO presentations | ST1.7

Electromagnetic electron hole generation: theory and PIC simulations

Gaetan Gauthier, Thomas Chust, Olivier Le Contel, and Philippe Savoini

Recent MMS observations (e.g. [Holmes et al, 2018, Steinvall et al., 2019]) exploring various regions of the magnetosphere have found solitary potential structures call Electron phase-space Hole (EH). These structures have kinetic scale (dozens of Debye lengths) and persist during long time (dozens of plasma frequency periods). EH are characterized by a bipolar electric field parallel to ambient magnetic field and fastly propagate along this latter (a few tenths of speed light). We have created a 3D Bernstein-Greene-Kruskal (BGK) model (as [Chen et al, 2004]) adapted to various magnetospheric ambient magnetic fields. BGK model results depend on choice of potential shape and passing distribution function at infinity (before EH potential interaction).

2D-3V Particle-In-Cell simulations have been developed with the fully kinetic code Smilei [Derouillat et al, 2017], using real magnetosphere plasma parameters. Solitary waves in the magnetotail are three-dimensional potentials which can be generated through nonlinear evolution of an electron beam instability (or bump on tail). The simulated EH are comparable to the EH observed in the magnetosphere with the same parameters.

We have also investigated the EH formation with density inhomogeneities using a BGK stability model we have developed. Indeed, density inhomogeneities exist notably in interplanetary plasmas. As a result taking into account the background density inhomogeneities, significantly alters the stability criteria. We have performed 2D-3V PIC simulations with realistic inhomogeneous density background (smaller than 10% of mean density) to understand such a type of EH formation.

References:

  • Holmes et al., J. Geophys. Res. Space Phys. 123, 9963, 2018
  • Steinvall et al., Phys. Rev. Lett. 123, 255101, 2019
  • Chen et al., Phys. Rev. E 69, 055401, 2004
  • Derouillat et al., Comput. Phys. Commun. 222, 351, 2017
 

How to cite: Gauthier, G., Chust, T., Le Contel, O., and Savoini, P.: Electromagnetic electron hole generation: theory and PIC simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11078, https://doi.org/10.5194/egusphere-egu21-11078, 2021.

EGU21-11164 | vPICO presentations | ST1.7

Formation of non-thermal electron velocity distribution functions in kinetic magnetic reconnection

Xin Yao, Patricio A. Muñoz, and Jörg Büchner
Magnetic reconnection can convert magnetic energy into non-thermal particle energy in the form of electron beams. Those accelerated electrons can, in turn, cause radio emission in environments such as solar flares. The actual properties of those electron velocity distribution functions (EVDFs) generated by reconnection are still not well understood. In particular the properties that are relevant for the micro-instabilities responsible for radio emission. We aim thus at characterizing the electron distributions functions generated by 3D magnetic reconnection by means of fully kinetic particle-in-cell (PIC) code simulations. Our goal is to characterize the possible sources of free energy of the generated EVDFs in dependence on an external (guide) magnetic field strength. We find that: (1) electron beams with positive gradients in their parallel (to the local magnetic field direction) distribution functions are observed in both diffusion region (parallel crescent-shaped EVDFs) and separatrices (bump-on-tail EVDFs). These non-thermal EVDFs cause counterstreaming and bump-on-tail instabilities. These electrons are adiabatic and preferentially accelerated by a parallel electric field in regions where the magnetic moment is conserved. (2) electron beams with positive gradients in their perpendicular distribution functions are observed in regions with weak magnetic field strength near the current sheet midplane. The characteristic crescent-shaped EVDFs (in perpendicular velocity space) are observed in the diffusion region. These non-thermal EVDFs can cause electron cyclotron maser instabilities. These non-thermal electrons in perpendicular velocity space are mainly non-adiabatic. Their EVDFs are attributed to electrons experiencing an E×B drift and meandering motion. (3) As the guide field strength increases, the number of locations in the current sheet with distributions functions featuring a perpendicular source of free energy significantly decreases.

How to cite: Yao, X., Muñoz, P. A., and Büchner, J.: Formation of non-thermal electron velocity distribution functions in kinetic magnetic reconnection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11164, https://doi.org/10.5194/egusphere-egu21-11164, 2021.

EGU21-11588 | vPICO presentations | ST1.7

In situ observation of three-dimensional anisotropies and scalings of space plasma turbulence at kinetic scales

Tieyan Wang, Jiansen He, Olga Alexandrova, Malcolm Dunlop, and Denise Perrone

The energy distribution at wave number space is known to be anisotropic in space plasmas. At kinetic scales, the standard Kinetic Alfven Wave model predicts anisotropy scaling of kpar ∝ kperp(1/3), whereas the latest models considering the intermittency, or tearing instabilities, predict scalings such as kpar ∝ kperp(2/3) and kpar ∝ kperp(3/3). Recent numerical simulations also payed considerable attention to this issue. Based on a unified analysis of five-point structure functions of the turbulence in three kinetic simulations, Cerri et al. 2019 obtained a converging result of lpar ∝ lperp(3/3). To enrich our knowledge of the anisotropic scaling relation from an observational point of view, we conducted a statistical survey for the turbulence measured by MMS in the magnetosheath. For the 349 intervals with burst mode data, abundant evidence of 3D anisotropy at the sub-proton scale (1-100 km) is revealed by five-point second order structure functions. In particular, the eddies are mostly elongated along background magnetic field B0 and shortened in the two perpendicular directions. The ratio between eddies’ parallel and perpendicular lengths features a trend of rise then fall toward small scales, whereas the anisotropy in the perpendicular plane appears scale invariant. Moreover, over 30% of the events exhibit scaling relations close to lpar ∝ lperp(2/3). In order to explain such signature, additional factors such as intermittency caused by different coherent structures may be required in addition to the critical balance premise.

How to cite: Wang, T., He, J., Alexandrova, O., Dunlop, M., and Perrone, D.: In situ observation of three-dimensional anisotropies and scalings of space plasma turbulence at kinetic scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11588, https://doi.org/10.5194/egusphere-egu21-11588, 2021.

EGU21-11962 | vPICO presentations | ST1.7

Expansion of hot plasma with Kappa distribution in coronal flare sources

Jan Benáček and Marian Karlický

We study how hot plasma that is released during a solar flare can be confined in its source and interact with surrounding colder plasma. The X-ray emission of coronal flare sources is well explained using Kappa velocity distribution. Therefore, we compare the difference in the confinement of plasma with Kappa and Maxwellian distribution. We use a 3D Particle-in-Cell code, which is large along magnetic field lines, effectively one-dimensional, but contains all electromagnetic effects. In the case with Kappa distribution, contrary to Maxwellian distribution, we found formation of several thermal fronts associated with double-layers that suppress particle fluxes. As the Kappa distribution of electrons forms an extended tail, more electrons are not confined by the first front and cause formation of multiple fronts. A beam of electrons from the hot part is formed at each front; it generates return current, Langmuir wave density depressions, and a double layer with a higher potential step than in the Maxwellian case. We compare the Kappa and Maxwellian cases and discuss how these processes could be observed.

How to cite: Benáček, J. and Karlický, M.: Expansion of hot plasma with Kappa distribution in coronal flare sources, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11962, https://doi.org/10.5194/egusphere-egu21-11962, 2021.

EGU21-13774 | vPICO presentations | ST1.7

Modeling the formation and eruption of coronal structures by linking data-driven magnetofrictional and MHD simulations

Farhad Daei, Jens Pomoell, Emilia Kilpua, Daniel Price, Anshu Kumari, and Simon Good

The time-dependent magnetofrictional model (TMFM) is a prevalent approach that has proven to be a very useful tool in the study of the formation of unstable structures in the solar corona. In particular, it is capable of incorporating observational data as initial and boundary conditions and requires shorter computational time compared to MHD simulations. To leverage the efficiency of data-driven TMFM and also to simulate eruptive events in the MHD framework, one can apply TMFM up to a certain time before the expected eruption(s) and then go on with simulation in the full or ideal MHD regime in order to more accurately capture the eruption process. However, due to the different evolution processes in these two models, using TMFM snapshots in an MHD simulation is non-trivial with several issues that need to be addressed, both physically and numerically.

 

In this study, we showcase our progress in using magnetofrictional model results as input to dynamical MHD simulations. In particular, we discuss the incompatibility of the TMFM output to serve as the initial condition in MHD, and show our methods of mitigating this.

As our benchmark test-case, we study the evolution of NOAA active region 12673, which was previously studied using data-driven TMFM by Price et al. (2019).

How to cite: Daei, F., Pomoell, J., Kilpua, E., Price, D., Kumari, A., and Good, S.: Modeling the formation and eruption of coronal structures by linking data-driven magnetofrictional and MHD simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13774, https://doi.org/10.5194/egusphere-egu21-13774, 2021.

EGU21-13908 | vPICO presentations | ST1.7

Scaling of magnetic reconnection with a limited x-line extent

Kai Huang, Yi-Hsin Liu, Quanming Lu, and Michael Hesse

Magnetic reconnection is a fundamental physical process that is responsible for releasing the magnetic energy during substorms of planetary magnetotails. Previous studies of magnetic reconnection usually take the two-dimensional (2D) approach, which assumes that reconnection is uniform in the 3rd direction out of the 2D reconnection plane. However, observations suggest that reconnection can be limited in the 3rd direction, such as reconnection at Mercury's magnetotail. It turns out that reconnection can be suppressed when reconnection region is very limited in the 3rd direction. An internal x-line asymmetry along the current direction develops because of the transport of reconnected magnetic flux by electrons beneath the ion kinetic scale, resulting in a suppression region identified in Liu et al., 2019. Under the guidance of a series of 3D kinetic simulations, in this work, we incorporate the length-scale of this suppression region ~10di to quantitatively model the reduction of the reconnection rate and the maximum outflow speed observed in the short x-line limit. The average reconnection rate drops because of the limited active region (where the current sheet thins down to the electron inertial scale) within an x-line. The outflow speed reduction correlates with the decrease of the J×B force, that can be modeled by the phase shift between the J and B profiles, also as a consequence of the flux transport. Notably, these two quantities are most essential in defining the well-being of magnetic reconnection, which can tell us when reconnection shall be suppressed.

How to cite: Huang, K., Liu, Y.-H., Lu, Q., and Hesse, M.: Scaling of magnetic reconnection with a limited x-line extent, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13908, https://doi.org/10.5194/egusphere-egu21-13908, 2021.

EGU21-14083 | vPICO presentations | ST1.7

Structure and Coalescence of Magnetopause Flux Ropes and Their Dependence on IMF Clock Angle: Three-Dimensional Global Hybrid Simulations

Jin Guo, San Lu, Quanming Lu, Yu Lin, Xueyi Wang, Kai Huang, Rongsheng Wang, and Shui Wang

Flux ropes are ubiquitous at Earth’s magnetopause and play important roles in energy transport between the solar wind and Earth’s magnetosphere. In this paper, structure and coalescence of the magnetopause flux ropes formed by multiple X line reconnection in cases with different southward interplanetary magnetic field (IMF) clock angles are investigated by using three-dimensional global hybrid simulations. As the IMF clock angle decreases from 180°, the axial direction of the flux ropes becomes tilted relative to the equatorial plane, the length of the flux ropes gradually increases, and core field within flux ropes is formed by the increase in the guide field. The flux ropes are formed mostly near the subsolar point and then move poleward towards cusps. The flux ropes can eventually enter the cusps, during which their helical structure collapses, their core field weakens gradually, and their axial length decreases. When the IMF clock angle is large (i.e., the IMF is predominantly southward), the flux ropes can coalesce and form new ones with larger diameter. The coalescence between flux ropes can occur both near the subsolar point when they are newly formed and away from the subsolar point (e.g., in the southern hemisphere) when they move towards cusps. However, when the IMF clock angle is small (≤ 135° ), we do not find coalescence between flux ropes.

How to cite: Guo, J., Lu, S., Lu, Q., Lin, Y., Wang, X., Huang, K., Wang, R., and Wang, S.: Structure and Coalescence of Magnetopause Flux Ropes and Their Dependence on IMF Clock Angle: Three-Dimensional Global Hybrid Simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14083, https://doi.org/10.5194/egusphere-egu21-14083, 2021.

EGU21-14112 | vPICO presentations | ST1.7

Progress towards small-scale field trials of coastal enhanced weathering of olivine

Stephen Romaniello, Shanee Stopnitzky, Tom Green, Francesc Montserrat, Eric Matzner, Cheyenne Moreau, Drew Syverson, Paloma Lopez, Matthew Hayden, Olivier Sulpis, and Brian Ley

Slow progress towards achieving global greenhouse gas emissions targets significantly increases the likelihood that future climate efforts may require not only emissions cuts but also direct climate mitigation via negative emissions technologies (IPCC AR5). Currently, such technologies exist at only a nascent stage of development, with significant uncertainties regarding their feasibility, cost, and potential unintended consequences and/or co-benefits.

Coastal enhanced weathering of olivine (CEWO) has been suggested as one potential pathway for achieving net negative CO2 emissions at scale. CEWO involves the mining of olivine-rich ultramafic rocks (such as dunite) for incorporation during beach augmentation and restoration work. While grinding this rock into increasingly fine particle sizes is essential for increasing its surface area and reactivity, this step is also costly and energetically expensive. CEWO attempts to minimize this cost and energy penalty by relying on wave and tidal action to provide ongoing physical weathering of olivine grains once distributed on beaches. Laboratory experiments and carbon emissions assessments of CEWO suggest that these approaches may be technically feasible and carbon negative, but significant uncertainties remain regarding the real-world kinetics of coastal olivine dissolution. Furthermore, concerns about the fate and ecological impact of nickel (Ni) and chromium (Cr)—potentially toxic trace metals found in olivine—require careful evaluation.

In 2019, Project Vesta was established as a nonprofit, philanthropically funded effort to evaluate the technical feasibility and ecological impacts of CEWO through a dedicated research program ultimately culminating in small-scale, real-world field trials of CEWO. This presentation will provide an overview and discussion of our overall research strategy, share insights from interim modeling and mesocosm experiments designed to ensure the practicality and safety of future field experiments, and explain our approach for ensuring transparent, responsible, and ethical research oversight and governance.

How to cite: Romaniello, S., Stopnitzky, S., Green, T., Montserrat, F., Matzner, E., Moreau, C., Syverson, D., Lopez, P., Hayden, M., Sulpis, O., and Ley, B.: Progress towards small-scale field trials of coastal enhanced weathering of olivine, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14112, https://doi.org/10.5194/egusphere-egu21-14112, 2021.

EGU21-14686 | vPICO presentations | ST1.7

Encounter of Parker Solar Probe and a Comet-like Object During Their Perihelia: Simulations and Measurements

Jiansen He, Bo Cui, Liping Yang, Chuanpeng Hou, Lei Zhang, Wing-Huen Ip, Yingdong Jia, Chuanfei Dong, Die Duan, Qiugang Zong, Stuart Bale, Marc Pulupa, John Bonnell, Thierry Dudok de Wit, Keith Goetz, Peter Harvey, Robert MacDowall, and David Malaspina
Parker Solar Probe (PSP) aims at exploring the nascent solar wind close to the Sun. Meanwhile, PSP is also expected to encounter small objects like comets and asteroids. In this work, we survey the ephemerides to find a chance of recent encounter, and then model the interaction between released dusty plasmas and solar wind plasmas. On 2019 September 2, a comet-like object 322P/SOHO just passed its perihelion flying to a heliocentric distance of 0.12 au, and swept by PSP at a relative distance as close as 0.025 au. We present the dynamics of dust particles released from 322P, forming a curved dust tail. Along the PSP path in the simulated inner heliosphere, the states of plasma and magnetic field are sampled and illustrated, with the magnetic field sequences from simulation results being compared directly with the in-situ measurements from PSP. Through comparison, we suggest that 322P might be at a deficient activity level releasing limited dusty plasmas during its way to becoming a “rock comet”. We also present images of solar wind streamers as recorded by WISPR, showing an indication of dust bombardment for the images superposed with messy trails. We observe from LASCO coronagraph that 322P was transiting from a dimming region to a relatively bright streamer during its perihelion passage, and simulate to confirm that 322P was flying from relatively faster to slower solar wind streams, modifying local plasma states of the streams.

How to cite: He, J., Cui, B., Yang, L., Hou, C., Zhang, L., Ip, W.-H., Jia, Y., Dong, C., Duan, D., Zong, Q., Bale, S., Pulupa, M., Bonnell, J., Dudok de Wit, T., Goetz, K., Harvey, P., MacDowall, R., and Malaspina, D.: Encounter of Parker Solar Probe and a Comet-like Object During Their Perihelia: Simulations and Measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14686, https://doi.org/10.5194/egusphere-egu21-14686, 2021.

Differential flow among different ion species are always observed in the solar wind, and such ion differential flow can provide a free energy to drive the Alfven/ion-cyclotron and fast-magnetosonic/whistler instabilities. Previous works on the ion beam instability are mainly focused on the solar wind parameters at 1 au. We extend this study using the radial model of the magnetic field and plasma parameters in the inner heliosphere. We present the distributions of the energy transfer rate among the unstable waves and the particles, which would be useful to predict the change of parallel and perpendicular temperatures during the instability evolution. Moreover, we propose an effective growth length to estimate the effective growth in each instability, and we explore that the oblique Alfven/ion-cyclotron instability, the oblique fast-magnetosonic/whistler instability and the oblique Alfven/ion-beam instability can be effectively driven by proton beams having speed of 500-2000 km/s in the solar atmosphere. We also show that the unstable waves driven by the proton beam instability would be responsible for the solar corona heating. These predictions can be checked by in situ satellite measurements in the inner heliosphere.

How to cite: Liu, W., Zhao, J., Xie, H., and Wu, D.: Electromagnetic Proton Beam Instabilities in the Inner Heliosphere: Energy Transfer Rate, Radial Distribution and Effective Excitation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14978, https://doi.org/10.5194/egusphere-egu21-14978, 2021.

EGU21-15168 | vPICO presentations | ST1.7

Direct Measurement of Ion Cyclotron Resonance Between Wave Fields and Protons in Space Plasmas

Qiaowen Luo, Xingyu Zhu, Jiansen He, Jun Cui, Hairong Lai, Daniel Verscharen, and Die Duan

Ion cyclotron resonance is one of the fundamental energy conversion processes through wave field-particle interaction in collisionless plasma. However, the key evidence for cyclotron resonance (i.e., the coherence between wave field and ion phase space density pertaining to the ion cyclotron resonance and responsible for the dissipation of ion cyclotron waves (ICWs)) has yet to be directly observed. Based on the high-quality measurements of space plasma by the Magnetospheric Multiscale (MMS) satellites, we observe that both the wave electromagnetic field vectors and the disturbed ion velocity distribution rotate around the background magnetic field. Moreover, we find that the gyrophase angle difference between the fluctuations in the ion velocity distribution functions and the wave electric field vectors are always in the range of (0, 90) degrees, clearly suggesting the ongoing energy conversion from wave fields to particles. By invoking plasma kinetic theory, we find that the field-particle correlation for the dissipative ion cyclotron waves in the theoretical model matches well with our observations. Furthermore, all the wave electric field vectors (Ewave), the ion current (Ji) and the energy transfer rate (Ji ·Ewave) exhibit quasi-periodic oscillations, and the frequency of Ji ·Ewave is about twice the frequency of Ewave and Ji, consistent with plasma kinetic theory. Therefore, our combined analysis of MMS observations and kinetic theory provides direct, thorough, and comprehensive evidence for ICW dissipation in space plasmas.

How to cite: Luo, Q., Zhu, X., He, J., Cui, J., Lai, H., Verscharen, D., and Duan, D.: Direct Measurement of Ion Cyclotron Resonance Between Wave Fields and Protons in Space Plasmas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15168, https://doi.org/10.5194/egusphere-egu21-15168, 2021.

Tangential discontinuities are finite-width current sheets separating two magnetized plasmas with different macroscopic properties. Such structures have been measured in-situ in the solar wind plasma by various space missions. Also, under certain conditions, the terrestrial magnetopause can be approximated with a tangential discontinuity. Studying the microstructure of tangential discontinuities is fundamentally important to understand the transfer of mass, momentum and energy in space plasmas. The propagation of solar wind discontinuities and their interaction with the terrestrial magnetosphere play a significant role for space weather science. In this paper we use 1d3v electromagnetic particle-in-cell simulations to study the kinetic structure and stability of one-dimensional tangential discontinuities. The simulation setup corresponds to a plasma slab configuration which allows the simultaneous investigation of two discontinuities at the interface between the slab population and the background plasma. The initial discontinuities are infinitesimal and evolve rapidly towards finite-width transition layers. We focus on tangential discontinuities with and without perpendicular velocity shear. Three-dimensional velocity distribution functions are computed in different locations across the discontinuities, at different time instances, for both electrons and ions. We emphasize the space and time evolution of the velocity distribution functions inside the transition layers and discuss their deviation from the initial Maxwellian distributions. The simulated distributions show similar features with the theoretical solutions provided by Vlasov equilibrium models.

How to cite: Voitcu, G. and Echim, M.: Electron and ion velocity distribution functions across one-dimensional tangential discontinuities: particle-in-cell simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15565, https://doi.org/10.5194/egusphere-egu21-15565, 2021.

EGU21-15658 | vPICO presentations | ST1.7

Fully kinetic simulations of electron-scale plasma turbulence in the inner heliosphere: a pathfinder for future spacecraft missions

Luca Franci, Emanuele Papini, Alfredo Micera, Daniele Del Sarto, Giovanni Lapenta, David Burgess, and Simone Landi

We present numerical results from high-resolution fully kinetic simulations of plasma turbulence under the near-Sun conditions encountered by Parker Solar Probe during its first perihelion, characterized by a low plasma beta and a large level of turbulent fluctuations. The recovered spectral properties are in agreement with those from PSP observations and recent high-resolution hybrid simulations just below the ion characteristic scales, i.e., the spectrum of the magnetic field exhibits a steep transition region with a spectral index compatible with -11/3. When the electron scales are reached a spectral break is observed and the spectrum steepens while still showing a clear power law. We discuss theoretical predictions for such a spectral behavior, based on a two-fluid model which assumes that a self-similar energy transfer across scales is occurring, without the need to include any kinetic process. We also analyse the role of magnetic reconnection and the statistics of reconnection events, as well as signatures in the proton and electron distribution functions hinting at mechanisms for energy dissipation. The results of this work represent a step forward in understanding the processes responsible for particle heating and acceleration and therefore on the origin of the solar wind and coronal heating. Furthermore, they allow for reliable predictions for future spacecraft missions investigating electron-scale physics in low-beta plasmas.

How to cite: Franci, L., Papini, E., Micera, A., Del Sarto, D., Lapenta, G., Burgess, D., and Landi, S.: Fully kinetic simulations of electron-scale plasma turbulence in the inner heliosphere: a pathfinder for future spacecraft missions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15658, https://doi.org/10.5194/egusphere-egu21-15658, 2021.

EGU21-16137 | vPICO presentations | ST1.7

Gap formation around 0.5Ωe of whistler-mode waves excited by electron temperature anisotropy

Huayue Chen, Xinliang Gao, Quanming Lu, and Konrad Sauer

With a 1-D PIC simulation model, we have investigated the gap formation around 0.5Ωe of the quasi-parallel whistler-mode waves excited by an electron temperature anisotropy. When the frequencies of excited waves in the linear stage cross 0.5Ωe, or when they are slightly larger than 0.5Ωe but then drift to lower values, the Landau resonance can make the electron distribution form a beam-like/plateau population. Such an electron distribution only slightly changes the dispersion relation of whistler-mode waves, but can cause severe damping around 0.5Ωe via cyclotron resonance. At last, the wave spectrum is separated into two bands with a power gap around 0.5Ωe. The condition under different electron temperature anisotropy and plasma beta is also surveyed for such kind of power gap. Besides, when only the waves with frequencies lower than 0.5Ωe are excited in the linear stage, a power gap can also be formed due to the wave-wave interactions, i.e., lower band cascade. Our study provides a clue to reveal the well-known 0.5Ωe power gap of whistler-mode waves ubiquitously observed in the inner magnetosphere.

How to cite: Chen, H., Gao, X., Lu, Q., and Sauer, K.: Gap formation around 0.5Ωe of whistler-mode waves excited by electron temperature anisotropy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16137, https://doi.org/10.5194/egusphere-egu21-16137, 2021.

Magnetic reconnection plays a crucial role in the process of solar flares and coronal mass ejections, in which large amounts of magnetic energy (10^29-10^32 ergs) are converted into kinetic energy and thermal energy, even allowing for particle acceleration. On the platform of the Computational Solar Physics Laboratory of Yunnan Observatories, we have performed a series of numerical experiments on magnetic reconnection related to solar eruption events as well as numerical method developments both in 2D and 3D. In this talk, we will present some recent studies on the topic of plasma heating by reconnection, MHD turbulence, wave structures and complicate structures of CMEs, etc. Our numerical results have great potentials to explain and predict many related solar activities in the corona. 

How to cite: Lin, J. and Ye, J.: Recent progress made in numerical experiments on magnetic reconnection and the related solar activities , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16423, https://doi.org/10.5194/egusphere-egu21-16423, 2021.

ST1.8 – Any way the wind blows: Observing and modelling the solar wind and its transients (CMEs and SIRs) through the heliosphere

EGU21-6200 | vPICO presentations | ST1.8

Understanding Solar Wind Formation by Identifying the Origins of In Situ Observations 

Samantha Wallace, Nicholeen M. Viall, and Charles N. Arge

Solar wind formation can be separated into three physical steps – source, release, and acceleration – that each leave distinct observational signatures on plasma parcels.  The Wang-Sheeley-Arge (WSA) model driven by Air Force Data Assimilative Photospheric Flux Transport (ADAPT) time-dependent photospheric field maps now has the ability to connect in situ observations more rigorously to their precise source at the Sun, allowing us to investigate the physical processes involved in solar wind formation.   In this talk, I will highlight my PhD dissertation research in which we use the ADAPT-WSA model to either characterize the solar wind emerging from specific sources, or investigate the formation process of various solar wind populations.  In the first study, we test the well-known inverse relationship between expansion factor (fs) and observed solar wind speed (vobs) for solar wind that emerges from a large sampling of pseudostreamers, to investigate if field line expansion plays a physical role in accelerating the solar wind from this source region.  We find that there is no correlation between fs and vobs at pseudostreamer cusps. In the second study, we determine the source locations of the first identified quasiperiodic density structures (PDSs) inside 0.6 au. Our modeling provides confirmation of these events forming via magnetic reconnection both near to and far from the heliospheric current sheet (HCS) – a direct test of the Separatrix-web (S-web) theory of slow solar wind formation.  In the final study, we use our methodology to identify the source regions of the first observations from the Parker Solar Probe (PSP) mission.  Our modeling enabled us to characterize the closest to the Sun observed coronal mass ejection (CME) to date as a streamer blowout.  We close with future ways that ADAPT-WSA can be used to test outstanding questions of solar wind formation.

How to cite: Wallace, S., Viall, N. M., and Arge, C. N.: Understanding Solar Wind Formation by Identifying the Origins of In Situ Observations , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6200, https://doi.org/10.5194/egusphere-egu21-6200, 2021.

To date, the inner boundary conditions for solar wind models are either directly or indirectly based on magnetic field extrapolation models of the photosphere. Furthermore, between the photosphere and Earth, there are no other direct empirical constraints on models. New breakthroughs in coronal rotation tomography, applied to coronagraph observations, allow maps of the coronal electron density to be made in the heliocentric height range 4-12 solar radii (Rs). We show that these maps (i) give a new empirical boundary condition for solar wind structure at a height where the coronal magnetic field has become radial, thus avoiding the need to model the complex inner coronal magnetic field, and (ii) give accurate rotation rates for the corona, of crucial importance to the accuracy of solar wind models and forecasts.

How to cite: Morgan, H.: Empirical inner boundary conditions and rotation rates for solar wind models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-782, https://doi.org/10.5194/egusphere-egu21-782, 2021.

EGU21-12459 | vPICO presentations | ST1.8

The Dynamic Time Warping as a means to assess modeled solar wind time series

Evangelia Samara, Emmanuel Chane, Brecht Laperre, Christine Verbeke, Manuela Temmer, Luciano Rodriguez, Jasmina Magdalenic, and Stefaan Poedts

In this work, the Dynamic Time Warping (DTW) technique is presented as an alternative method to assess the performance of modeled solar wind time series at Earth (or at any other point in the heliosphere). This method can quantify how similar two time series are by providing a temporal alignment between them, in an optimal way and under certain restrictions. It eventually estimates the optimal alignment between an observed and a modeled series, which we call the warping path, by providing a single number, the so-called DTW cost. A description on the reasons why DTW should be applied as a metric for the assessment of solar wind time series, is presented. Furthermore, examples on how exactly the technique is applied to our modeled solar wind datasets with EUHFORIA, are shown and discussed.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 (SafeSpace).

How to cite: Samara, E., Chane, E., Laperre, B., Verbeke, C., Temmer, M., Rodriguez, L., Magdalenic, J., and Poedts, S.: The Dynamic Time Warping as a means to assess modeled solar wind time series, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12459, https://doi.org/10.5194/egusphere-egu21-12459, 2021.

EGU21-7536 | vPICO presentations | ST1.8

Long-term correlations in solar proxies and solar wind parameters

Luca Giovannelli, Raffaele Reda, Tommaso Alberti, Francesco Berrilli, Matteo Cantoresi, Dario Del Moro, Piermarco Giobbi, and Valentina Penza

The long-term behaviour of the Solar wind and its impact on the Earth are of paramount importance to understand the framework of the strong transient perturbations (CMEs, SIRs). Solar variability related to its magnetic activity can be quantified by using synthetic indices (e.g. sunspots number) or physical ones (e.g. chromospheric proxies). In order to connect the long-term solar activity variations to solar wind properties, we use Ca II K index and solar wind OMNI data in the time interval between 1965 and 2019, which almost entirely cover the last 5 solar cycles. A time lag in the correlation between the parameters is found. This time shift seems to show a temporal evolution over the different solar cycles.

 

How to cite: Giovannelli, L., Reda, R., Alberti, T., Berrilli, F., Cantoresi, M., Del Moro, D., Giobbi, P., and Penza, V.: Long-term correlations in solar proxies and solar wind parameters, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7536, https://doi.org/10.5194/egusphere-egu21-7536, 2021.

EGU21-15803 | vPICO presentations | ST1.8

Using Gradient Boosting Regressors to forecast the ambient solar wind from coronal magnetic models

Rachel Bailey, Martin A. Reiss, Christian Möstl, C. Nick Arge, Carl Henney, Matt Owens, Ute Amerstorfer, Tanja Amerstorfer, Andreas Weiss, and Jürgen Hinterreiter

In this study we present a method for forecasting the ambient solar wind at L1 from coronal magnetic models. Ambient solar wind flows in interplanetary space determine how solar storms evolve through the heliosphere before reaching Earth, and accurately modelling and forecasting the ambient solar wind flow is therefore imperative to space weather awareness. We describe a novel machine learning approach in which solutions from models of the solar corona based on 12 different ADAPT magnetic maps are used to output the solar wind conditions some days later at the Earth. A feature analysis is carried out to determine which input variables are most important. The results of the forecasting model are compared to observations and existing models for one whole solar cycle in a comprehensive validation analysis. We find that the new model outperforms existing models and 27-day persistence in almost all metrics. The final model discussed here represents an extremely fast, well-validated and open-source approach to the forecasting of ambient solar wind at Earth, and is specifically well-suited for ensemble modelling or for application with other coronal models.

How to cite: Bailey, R., Reiss, M. A., Möstl, C., Arge, C. N., Henney, C., Owens, M., Amerstorfer, U., Amerstorfer, T., Weiss, A., and Hinterreiter, J.: Using Gradient Boosting Regressors to forecast the ambient solar wind from coronal magnetic models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15803, https://doi.org/10.5194/egusphere-egu21-15803, 2021.

EGU21-13510 | vPICO presentations | ST1.8

Multi-year statistical analysis of properties of current sheets at 1 AU

Olga Khabarova, Timothy Sagitov, Roman Kislov, and Gang Li

We use the multi-year open acees database of current sheets identified at 1 AU with the one-second resolution from ACE data (https://csdb.izmiran.ru ) to study properties of current sheets in the solar wind. We find that the CS daily rate (the number of CSs per day) R correlates with the solar wind temperature T rather than with the solar wind speed V and is proportional to the sum of the kinetic and thermal energy density. The main statistical results preliminary obtained in the study are as follows:

  • There is clustering of CSs.
  • Maxima of R are associated with stream/corotating interaction regions (SIRs/CIRs) and interplanetary mass ejection (ICME) sheaths.
  • On average, one-three thousands of CSs are detected daily at the Earth’s orbit. The best-fit parameter is (V 2 (N+5 N ' ) + 10( N+ N ' )T )/5000 if V is given in km/s, T - in K, N is given in cm-3,  and N ' =2 cm-3 is the background level of the solar wind density. The correlation coefficient between the parameter and R  is ~0.8.
  • There is no obvious connection between the daily CS rate and the solar cycle. However, this preliminary conclusion should be reconsidered after the expansion of the CS database to several solar cycles.

O.K. and R.K. are supported by Russian Science Foundation grant No. 20-42-04418. T.S. acknowledges the HSE’s general support and encouragement of student’s scientific activity.

How to cite: Khabarova, O., Sagitov, T., Kislov, R., and Li, G.: Multi-year statistical analysis of properties of current sheets at 1 AU, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13510, https://doi.org/10.5194/egusphere-egu21-13510, 2021.

EGU21-13048 | vPICO presentations | ST1.8

Modeling the magnetic structure of CMEs in the inner heliosphere based on data-driven time-dependent simulations of active region evolution

Jens Pomoell, Emilia Kilpua, Daniel Price, Eleanna Asvestari, Ranadeep Sarkar, Simon Good, Anshu Kumari, Sanchita Pal, and Farhad Daei

Characterizing the detailed structure of the magnetic field in the active corona is of crucial importance for determining the chain of events from the formation to the destabilisation and subsequent eruption and propagation of coronal structures in the heliosphere. A comprehensive methodology to address these dynamic processes is needed in order to advance our capabilities to predict the properties of coronal mass ejections (CMEs) in interplanetary space and thereby for increasing the accuracy of space weather predictions. A promising toolset to provide the key missing information on the magnetic structure of CMEs are time-dependent data-driven simulations of active region magnetic fields. This methodology permits self-consistent modeling of the evolution of the coronal magnetic field from the emergence of flux to the birth of the eruption and beyond. 

In this presentation, we discuss our modeling efforts in which time-dependent data-driven coronal modeling together with heliospheric physics-based modeling are employed to study and characterize CMEs, in particular their magnetic structure, at various stages in their evolution from the Sun to Earth. 

How to cite: Pomoell, J., Kilpua, E., Price, D., Asvestari, E., Sarkar, R., Good, S., Kumari, A., Pal, S., and Daei, F.: Modeling the magnetic structure of CMEs in the inner heliosphere based on data-driven time-dependent simulations of active region evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13048, https://doi.org/10.5194/egusphere-egu21-13048, 2021.

EGU21-10416 | vPICO presentations | ST1.8

A Model for Coronal Inflows and In/Out Pairs

Benjamin Lynch

We present a three-dimensional (3D) numerical magnetohydrodynamics (MHD) model of the white-light coronagraph observational phenomena known as coronal inflows and in/out pairs. Coronal inflows in the LASCO/C2 field of view (approximately 2–6 Rs) were thought to arise from the dynamic and intermittent release of solar wind plasma associated with the helmet streamer belt as the counterpart to outward-propagating streamer blobs, formed by magnetic reconnection. The MHD simulation results show relatively narrow lanes of density depletion form high in the corona and propagate inward with sinuous motion that has been characterized as "tadpole-like" in coronagraph imagery. The height–time evolution and velocity profiles of the simulation inflows and in/out pairs are compared to their corresponding observations and a detailed analysis of the underlying magnetic field structure associated with the synthetic white-light and mass density evolution is presented. Understanding the physical origin of this structured component of the slow solar wind’s intrinsic variability could make a significant contribution to solar wind modeling and the interpretation of remote and in situ observations from Parker Solar Probe and Solar Orbiter.

How to cite: Lynch, B.: A Model for Coronal Inflows and In/Out Pairs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10416, https://doi.org/10.5194/egusphere-egu21-10416, 2021.

EGU21-2535 | vPICO presentations | ST1.8

Deriving CME volume and density from remote sensing data

Manuela Temmer, Lukas Holzknecht, Mateja Dumbovic, Bojan Vrsnak, Nishtha Sachdeva, Stephan G. Heinemann, Karin Dissauer, Camilla Scolini, Eleanna Asvestari, Astrid M. Veronig, and Stefan Hofmeister

Using combined STEREO-SOHO white-light data, we present a method to determine the volume and density of a coronal mass ejection (CME) by applying the graduated cylindrical shell model (GCS) and deprojected mass derivation. Under the assumption that the CME  mass is roughly equally distributed within a specific volume, we expand the CME self-similarly and calculate the CME density for distances close to the Sun (15–30 Rs) and at 1 AU. The procedure is applied on a sample of 29 well-observed CMEs and compared to their interplanetary counterparts (ICMEs). Specific trends are derived comparing calculated and in-situ measured proton densities at 1 AU, though large uncertainties are revealed due to the unknown mass and geometry evolution: i) a moderate correlation for the magnetic structure having a mass that stays rather constant and ii) a weak correlation for the sheath density by assuming the sheath region is an extra mass - as expected for a mass pile-up process - that is in its amount comparable to the initial CME deprojected mass. High correlations are derived between in-situ measured sheath density and the solar wind density and solar wind speed as measured 24 hours ahead of the arrival of the disturbance. This gives additional confirmation that the sheath-plasma indeed stems from piled-up solar wind material. While the CME interplanetary propagation speed is not related to the sheath density, the size of the CME may play some role in how much material is piled up.

How to cite: Temmer, M., Holzknecht, L., Dumbovic, M., Vrsnak, B., Sachdeva, N., Heinemann, S. G., Dissauer, K., Scolini, C., Asvestari, E., Veronig, A. M., and Hofmeister, S.: Deriving CME volume and density from remote sensing data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2535, https://doi.org/10.5194/egusphere-egu21-2535, 2021.

EGU21-9500 | vPICO presentations | ST1.8

Effects of optimisation parameters on data-driven magnetofrictional modelling 

Anshu Kumari, Daniel Price, Emilia Kilpua, Jens Pomoell, and Farhad Daei

The solar coronal magnetic field plays an important role in the formation, evolution, and dynamics of small and large-scale structures in the corona. Estimation of the coronal magnetic field, the ultimate driver of space weather, particularly in the ‘low’ and ‘middle’ corona, is presently limited due to practical difficulties. Data-driven time-dependent magnetofrictional modelling (TMFM) of active region magnetic fields has been proven as a tool to observe and study the corona. In this work, we present a detailed study of data-driven TMFM of active region 12473 to trace the early evolution of the flux rope related to the coronal mass ejection that occurred on 28 December 2015. Non-inductive electric field component in the photosphere is critical for energizing and introducing twist to the coronal magnetic field, thereby allowing unstable configurations to be formed. We estimate this component using an approach based on optimizing the injection of magnetic energy. We study the effects of these optimisation parameters on the data driven coronal simulations. By varying the free optimisation parameters, we explore the changes in flux rope formation and their early evolution, as well other parameters, e.g. axial flux, magnetic field magnitude.

How to cite: Kumari, A., Price, D., Kilpua, E., Pomoell, J., and Daei, F.: Effects of optimisation parameters on data-driven magnetofrictional modelling , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9500, https://doi.org/10.5194/egusphere-egu21-9500, 2021.

EGU21-38 | vPICO presentations | ST1.8

Relationship of EIT Waves Phenomena with Other Solar Phenomena

Virendra Verma


 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, indicate 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 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 view of the latest 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-

How to cite: Verma, V.: Relationship of EIT Waves Phenomena with Other Solar Phenomena, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-38, https://doi.org/10.5194/egusphere-egu21-38, 2021.

EGU21-2667 | vPICO presentations | ST1.8

IPSCAT: A Catalogue of Solar Transients Identified through Interplanetary Scintillation Analysis

David Barnes, Mario Bisi, Jackie Davies, and Richard Harrison

We present a catalogue, IPSCAT, of the results of Interplanetary Scintillation (IPS) analysis applied to observations that are compiled using data from three European radio networks, EISCAT, MERLIN and LOFAR, during the early science phase of the STEREO mission, from 2007 to 2012. These analyses provide a means to study the solar wind and interplanetary transients, which we complement with observations from the Heliospheric Imagers on-board STEREO. Within the IPS data set we identify transient phenomena, specifically Coronal Mass Ejections (CMEs) and Stream Interaction Regions (SIRs), via both visual inspection and an automatic feature-finding algorithm. We study the effectiveness of the automated detection algorithm and find it to be successful at classifying CMEs, whilst the identification of SIRs is less easily established. A discussion of the statistical properties of IPSCAT is presented, together with a comparison between the IPS and HI results. Finally, we present a case study of successive CMEs within the IPSCAT data set, which were also observed by the HIs on both STEREO spacecraft and analysed using the Stereoscopic Self-Similar Expansion (SSSE) method. This work was carried out as part of the EU FP7 HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service) project (http://www.helcats-fp7.eu/).

How to cite: Barnes, D., Bisi, M., Davies, J., and Harrison, R.: IPSCAT: A Catalogue of Solar Transients Identified through Interplanetary Scintillation Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2667, https://doi.org/10.5194/egusphere-egu21-2667, 2021.

EGU21-13423 | vPICO presentations | ST1.8

A century of geomagnetic storms, CMEs and HSS/SIRs

Kalevi Mursula, Timo Qvick, and Lauri Holappa

Geomagnetic storms are mainly driven by the two main solar wind transients: coronal mass ejections (CME) and high-speed solar wind streams with related (corotating) stream interaction regions (HSS/SIR). CMEs are produced by new magnetic flux emerging on solar surface as active regions, and their occurrence follows the occurrence of sunspots quite closely. HSSs are produced by coronal holes, whose occurrence at the ecliptic is maximized in the declining phase of the solar cycle.

Geomagnetic storms are defined and quantified by the Dst index that measures the intensity of the ring current and is available since 1957. We have corrected some early errors in the Dst index and extended its time interval from 1932 onwards using the same stations as the Dst index (CTO preceding HER). This extended storm index is called the Dxt index. We have also constructed Dxt3 and Dxt2 indices from three/two of the longest-operating Dst stations to extend the storm index back to 1903, covering more than a century of storms.

We divide the storms into four intensity categories (weak, moderate, intense and major), and use the classification of solar wind by Richardson et al. into CME, HSS/SIR and slow wind -related flows in order to study the drivers of storms of each intensity category since 1964. We also correct and use the list of sudden storm commencements (SSC) collected by Father P. Mayaud, and divide the storms of each category into SSC-related storms and non-SSC storms.

Studying geomagnetic storms of different intensity category and SSC relation allows us to study the occurrence of CMEs and HSS/SIR over the last century. We also use these results to derive new information on the centennial evolution of the structure of solar magnetic fields.

How to cite: Mursula, K., Qvick, T., and Holappa, L.: A century of geomagnetic storms, CMEs and HSS/SIRs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13423, https://doi.org/10.5194/egusphere-egu21-13423, 2021.

EGU21-661 | vPICO presentations | ST1.8

The effect of stream interaction regions on CME structures: observations in longitudinal conjunction at Mercury and 1 AU

Camilla Scolini, Reka M. Winslow, Noé Lugaz, and Antoinette B. Galvin

We present a study of two CMEs observed at Mercury and 1 AU by spacecraft in longitudinal conjunction. Of the two CMEs, one propagated relatively self-similarly, while the other one underwent significant changes in its properties, making them excellent case studies to investigate the following question: what causes the drastic alterations observed in some CMEs during propagation, while other CMEs remain relatively unchanged? Answering this question will also help us better understand the potential impact of CMEs on the near-Earth environment. 

In this work we focus on the presence or absence of large-scale corotating structures in the propagation space between Mercury and 1 AU, that have been shown in the past to influence  the orientation  of  CME  magnetic  structures  and  the  properties  of  CME  sheaths. At both locations, we determine the CME flux rope orientation and characteristics using different fitting and classification methods. Our analysis is complemented by solar wind plasma measurements near 1 AU, by estimates of the size evolution of the sheaths and magnetic ejecta with heliocentric distance, and by the identification of solar wind structures in the CME propagation space based on in situ data, remote-sensing observations, and numerical simulations of the solar wind conditions in the inner heliosphere.

Results indicate that the changes observed in one CME were likely caused by a stream interaction region, while the CME exhibiting little change did not interact with any large-scale structure between Mercury and 1 AU. This work provides end-member examples of CME propagation in the inner heliosphere, exemplifying how interactions  with  corotating  structures  in  the  solar  wind  can  induce  essential  changes  in  CME structures. Our findings provide new fundamental insights on the propagation and evolution of CMEs, and can help lay the foundation for improved predictions of CME properties at 1 AU.

How to cite: Scolini, C., Winslow, R. M., Lugaz, N., and Galvin, A. B.: The effect of stream interaction regions on CME structures: observations in longitudinal conjunction at Mercury and 1 AU, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-661, https://doi.org/10.5194/egusphere-egu21-661, 2021.

EGU21-1799 | vPICO presentations | ST1.8

ICMEs and low plasma density in the solar wind observed at L1

Brigitte Schmieder, Christine Verbeke, Emmanuel Chané, Pascal Démoulin, Stefaan Poedts, and Benjamin Grison

Different regimes of the solar wind have been observed at L1 during and after the passage of ICMEs, particularly anomalies with very low plasma density. From the observations at L1 (ACE) we identified different possible cases. A first case was explained by the evacuation of the plasma due over expansion of the ICME (May 2002). The second case on July 2002 is intriguing.In July 2002, three halo fast speed ICMEs, with their origin in the central part of the Sun, have surprisingly a poor impact on the magnetosphere (Dst > -28 nT).   Analyzing the characteristics of the first ICME at L1, we conclude that the spacecraft crosses the ICME with a large impact (Bx component in GSE coordinates is dominant). The plasma density is low, just behind this first ICME. Next, we explore the generic conditions of low density formation in the EUHFORIA simulations.The very low density plasma after the sheath could be explained by the spacecraft crossing, on the side of the flux rope, while behind the front shock. We investigate two possible interpretations. The shock was able to compress and accelerate so much the plasma that a lower density is left behind. This can also be due to an effect of the sheath magnetic field which extends the flux rope  effect on the sides of it,    so a decrease of plasma density could occur like behind a moving object (here the sheath field). The following ICME, with also a low density, could be an intrinsic case with the formation in the corona of a cavity. Finally, we present some runs of EUHFORIA which fit approximately these data and argue in favor of the possible interpretations detailed above.

How to cite: Schmieder, B., Verbeke, C., Chané, E., Démoulin, P., Poedts, S., and Grison, B.: ICMEs and low plasma density in the solar wind observed at L1, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1799, https://doi.org/10.5194/egusphere-egu21-1799, 2021.

EGU21-3291 | vPICO presentations | ST1.8

Constraining the CME parameters of the spheromak flux rope implemented in EUHFORIA

Eleanna Asvestari, Jens Pomoell, Emilia Kilpua, Simon Good, Theodosios Chatzistergos, Manuela Temmer, Erika Palmerio, Stefaan Poedts, and Jasmina Magdalenic

Coronal mass ejections (CMEs) are primary drivers of space weather phenomena. Modelling the evolution of the internal magnetic field configuration of CMEs as they propagate through the interplanetary space is an essential part of space weather forecasting. EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is a data-driven, physics-based model, able to trace the evolution of CMEs and CME-driven shocks through realistic background solar wind conditions. It employs a spheromak-type magnetic flux rope that is initially force-free, providing it with the advantage of modelling CME as magnetised structures. For this work we assessed the spheromak CME model employed in EUHFORIA with a test CME case study. The selected CME eruption occurred on the 6th of January 2013 and was encountered by two spacecraft, Venus Express and STEREO--A, which were radially aligned at the time of the CME passage. Our focus was to constrain the input parameters, with particular interest in: (1) translating the angular widths of the graduated cylindrical shell (GCS) fitting to the spheromak radius, and (2) matching the observed magnetic field topology at the source region. We ran EUHFORIA with three different spheromak radii. The model predicts arrival times from half to a full day ahead of the one observed in situ. We conclude that the choice of spheromak radius affected the modelled magnetic field profiles, their amplitude, arrival times, and sheath region length.

How to cite: Asvestari, E., Pomoell, J., Kilpua, E., Good, S., Chatzistergos, T., Temmer, M., Palmerio, E., Poedts, S., and Magdalenic, J.: Constraining the CME parameters of the spheromak flux rope implemented in EUHFORIA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3291, https://doi.org/10.5194/egusphere-egu21-3291, 2021.

EGU21-3605 | vPICO presentations | ST1.8

Development and Validation of CME Arrival-Time Forecasting System by MHD Simulations based on Interplanetary Scintillation Observations

Kazumasa Iwai, Daikou Shiota, Munetoshi Tokumaru, Ken’ichi Fujiki, Mitsue Den, and Yûki Kubo

Coronal mass ejections (CMEs) cause various disturbances of the space environment; therefore, forecasting their arrival time is very important. However, forecasting accuracy is hindered by limited CME observations in interplanetary space. This study developed a CME arrival-time forecasting system using a three-dimensional (3D) magnetohydrodynamic (MHD) simulations based on interplanetary scintillation (IPS) observations. The base MHD simulation is SUSANO-CME (Shiota and Kataoka 2016), in which CMEs are approximated as spheromaks. In the developed forecasting system, many MHD simulations with different CME initial speed are tested. The IPS responses of each MHD simulation run is calculated from the density distributions derived from the MHD simulation, and compared with IPS data observed by the Institute for Space-Earth Environmental Research (ISEE), Nagoya University. The CME arrival time of the simulation run that most closely agrees with the IPS data is automatically selected as the forecasted time.

We then validate the accuracy of this forecast using 12 halo CME events. The average absolute arrival-time error of the IPS-based MHD forecast is approximately 5.0 h, which is one of the most accurate predictions that ever been validated, whereas that of MHD simulations without IPS data, in which the initial CME speed is derived from white-light coronagraph images, is approximately 6.7 h. This suggests that the assimilation of IPS data into MHD simulations can improve the accuracy of CME arrival-time forecasts. The average predicted arrival times are earlier than the actual arrival times. These early predictions may be due to overestimation of the magnetic field included in the spheromak and/or underestimation of the drag force from the background solar wind, the latter of which could be related to underestimation of CME size or background solar wind density.

How to cite: Iwai, K., Shiota, D., Tokumaru, M., Fujiki, K., Den, M., and Kubo, Y.: Development and Validation of CME Arrival-Time Forecasting System by MHD Simulations based on Interplanetary Scintillation Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3605, https://doi.org/10.5194/egusphere-egu21-3605, 2021.

EGU21-8863 | vPICO presentations | ST1.8

Modelling the Impact of Magnetic Storms on Planetary Environments

Souvik Roy and Dibyendu Nandy

Coronal mass ejections (CMEs), large scale transient eruptions observed in the Sun, are thought to also be spawned by other magnetically active stars. The magnetic flux ropes intrinsic to these storms, and associated high-speed plasma ejecta perturb planetary environments creating hazardous conditions. To understand the physics of CME impact and consequent perturbations in planetary environments, we use 3D compressible magnetohydrodynamic simulation of a star-planet module (CESSI-SPIM) developed at CESSI, IISER Kolkata based on the PLUTO code architecture.  We explore magnetohydrodynamic processes such as the formation of a bow-shock, magnetopause, magnetotail, planet-bound current sheets and atmospheric mass loss as a consequence of magnetic-storm-planetary interactions. Specifically, we utilize a realistic, twisted flux rope model for our CME, which leads to interesting dynamics related to helicity injection into the magnetosphere. Such studies will help us understand how energetic magnetic storms from host stars impact magnetospheres and atmospheres with implications for planetary and exoplanetary habitability.

How to cite: Roy, S. and Nandy, D.: Modelling the Impact of Magnetic Storms on Planetary Environments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8863, https://doi.org/10.5194/egusphere-egu21-8863, 2021.

EGU21-12295 | vPICO presentations | ST1.8

Multi-Spacecraft Observations of a Unique Type of High-Latitude ICME

Megan Maunder, Claire Foullon, Robert Forsyth, Emma Davies, David Barnes, and Jackie Davies

Coronal Mass Ejections (CMEs) and their interplanetary counterparts (ICMEs) are key drivers of space weather throughout the heliosphere. Observational studies are used to understand their evolution and for developing existing models and theory in space weather forecasting. Motivated by the future exploration of the solar high-latitudes by Solar Orbiter and complimented by Parker Solar Probe, we aim to contribute to the understanding of high-latitude CMEs as they develop into ICMEs. We examine a high-latitude CME and its subsequent ICME using data from STEREO, Ulysses, and near-Earth spacecraft. We apply a triangulation method to the remote-sensing images from the twin STEREO spacecraft and conduct a multi-spacecraft analysis using the in-situ Ulysses, STEREO, and near-Earth spacecraft data. The Ulysses observations, supported by the other spacecraft, provides a clear picture of the ICME geometry and structure: a shock, followed by a sheath region, and a magnetic flux rope followed by a high-speed stream. This ICME differs from the known ‘over-expanding’ types observed in the high-latitudes by the Ulysses mission, in that it straddles a region between the slow and fast solar winds which in itself drives a shock.

How to cite: Maunder, M., Foullon, C., Forsyth, R., Davies, E., Barnes, D., and Davies, J.: Multi-Spacecraft Observations of a Unique Type of High-Latitude ICME, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12295, https://doi.org/10.5194/egusphere-egu21-12295, 2021.

ST2.1 – Open Session on the Magnetosphere

EGU21-48 | vPICO presentations | ST2.1

On the transmission of compressional fluctuations from the solar wind to the magnetosphere: an analysis of critical aspects  

Umberto Villante, Simone Di Matteo, and Dario Recchiuti

An important aspect of the interaction between the solar wind (SW) and the magnetosphere concerns the relationship between the SW structures/fluctuations and the onset/transmission of the magnetospheric wave modes. Several critical aspects may influence the results of similar analysis: for example, the frequency of fluctuations that are expected to impinge the magnetosphere may be not the same when they are observed by spacecraft at different places in front of the magnetosphere and the choice of the analytical methods adopted for the spectral analysis might influence the frequency estimate (as well as the wave identification) both in the SW and in the magnetosphere (Di Matteo and Villante, 2017, 2018). Focusing attention on these aspects, we present an analysis of SW compressional fluctuations (f ≈ 1-5 mHz), following two interplanetary shocks, as observed by two spacecraft at different places and compared them with the magnetospheric fluctuations following the corresponding sudden impulses, observed by two satellites at geostationary orbit and at several ground-based stations. Our results confirm that the comparison of different methods of spectral analysis is crucial to obtain a definite estimate of the characteristics of fluctuations in each region. For a case study, in which SW fluctuations at the same frequencies were observed by both interplanetary spacecraft, we found that all fluctuations observed in the magnetosphere were related to SW compressional fluctuations approximately at the same frequencies, with no evidence for wave activity of internal origin, or directly driven by the shock impact.

 

How to cite: Villante, U., Di Matteo, S., and Recchiuti, D.: On the transmission of compressional fluctuations from the solar wind to the magnetosphere: an analysis of critical aspects  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-48, https://doi.org/10.5194/egusphere-egu21-48, 2021.

EGU21-8039 | vPICO presentations | ST2.1

Fast Plasma Flows Downstream of the Bow Shock Using MMS: Correlations and Generation Mechanisms

Savvas Raptis, Tomas Karlsson, Ferdinand Plaschke, Anita Kullen, and Per-Arne Lindqvist

Fast plasma flows (magnetosheath jets) are localized and transient dynamic pressure enhancements found downstream of the Earth’s bow shock, in the magnetosheath region. They can be attributed to density and/or density enhancements and they are an energetic manifestation of the solar wind-magnetosphere coupling. They have been associated to several phenomena such as magnetopause reconnection, direct magnetosphere plasma inflow and the energization of the outer radiation belt electrons.

In this work, we are investigating the properties of a dataset of 9196 jets found by Magnetospheric Multiscale (MMS) from 09/2015 to 09/2020. These jets are classified into different classes based on their associated bow shock configuration. From the full dataset, about 300 jets are distinguished by being in very close proximity to a bow shock transition.

This subset of jet is then carefully pre-processed and statistically analyzed, providing information regarding the likelihood of existent (bow shock ripples, SLAMS penetration) and newly proposed (magnetic reconnection, magnetic islands) generation mechanisms for these jets. The initial results of these events support the pre-existing generation mechanism while giving indications to other possible effects that may take place.

How to cite: Raptis, S., Karlsson, T., Plaschke, F., Kullen, A., and Lindqvist, P.-A.: Fast Plasma Flows Downstream of the Bow Shock Using MMS: Correlations and Generation Mechanisms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8039, https://doi.org/10.5194/egusphere-egu21-8039, 2021.

EGU21-11963 | vPICO presentations | ST2.1

Analytical model of a magnetopause with countercurrents: multicomponent plasma with arbitrary particle energy distributions

Anton Nechaev, Vitaly Kocharovsky, and Vladimir Kocharovsky

We propose an analytical model for a distributed current sheet separating two regions of anisotropic collisionless plasma with different values of magnetization and different effective temperatures of the energy distributions of electrons and ions [1, 2]. Namely, we find a solution to the Vlasov–Maxwell equations in the form of a superposition of arbitrary isotropic distribution functions of particle energy, each multiplied by a Heaviside step function of one of the projections of the generalized momentum. This solution admits the shear of magnetic field lines and the presence of several ion components with different effective temperatures and localized countercurrents with arbitrary densities and spatial shifts.

It is shown that a certain choice of the energy distribution of particles (Maxwellian, kappa, and others) determine only the quantitative, not qualitative, properties of the constructed models. Sheets containing several fractions of particles with countercurrents, shifted relative to each other in space and having different scales, allow multiple non-monotonic changes in the magnetic field value and direction. The total thickness of the current sheet is determined by the values of shifts between the currents of the plasma fractions with the highest energy content and by the typical gyroradii of their particles.

We carried out particle-in-cell simulations of the analytically constructed magnetic transition layers in one-dimensional and two-dimensional geometries. The stability of the simplest models of the considered class is demonstrated, which is consistent with qualitative estimates of stability against Weibel-type perturbations.

The proposed models make it possible to interpret modern data of satellite observations of multicomponent current sheets in the regions of the magnetopause and the bow shock, solar wind magnetic clouds and high coronal magnetic structures, and to analyze their fine structure taking into account the observed suprathermal, nonequilibrium particle fractions.

The investigation of stability of current sheets was supported by the Russian Science Foundation under grant No. 20-12-00268.

1. Kocharovsky V. V., Kocharovsky Vl. V., Martyanov V. Yu., Nechaev A. A. An analytical model for the current structure of the magnetosheath boundary in a collisionless plasma // Astron. Lett. 2019. V. 45, No. 8. P. 551–564. doi:10.1134/S1063773719080048 .

2. Kocharovsky V. V., Kocharovsky Vl. V., Nechaev A. A. Analytical model of a magnetopause in a multicomponent collisionless plasma with a kappa energy distribution of particles // Doklady Physics. 2021. V. 496. In press.

How to cite: Nechaev, A., Kocharovsky, V., and Kocharovsky, V.: Analytical model of a magnetopause with countercurrents: multicomponent plasma with arbitrary particle energy distributions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11963, https://doi.org/10.5194/egusphere-egu21-11963, 2021.

EGU21-13054 | vPICO presentations | ST2.1 | Highlight

Hybrid-Vlasov modelling of three-dimensional dayside magnetopause reconnection

Yann Pfau-Kempf, Minna Palmroth, Andreas Johlander, Lucile Turc, Markku Alho, Markus Battarbee, Maxime Grandin, Maxime Dubart, and Urs Ganse

Dayside magnetic reconnection at the magnetopause, which is a major driver of space weather, is studied for the first time in a three-dimensional (3D) realistic setup using the Vlasiator hybrid-Vlasov kinetic model. A noon–midnight meridional plane simulation is extended in the dawn–dusk direction to cover 7 Earth radii. The southward interplanetary magnetic field causes magnetic reconnection to occur at the subsolar magnetopause. Perturbations arising from kinetic instabilities in the magnetosheath appear to modulate the reconnection. Its characteristics are consistent with multiple, bursty, and patchy magnetopause reconnection. It is shown that the kinetic behavior of the plasma, as simulated by the model, has consequences on the applicability of methods such as the four-field junction to identify and analyse magnetic reconnection in 3D kinetic simulations.

How to cite: Pfau-Kempf, Y., Palmroth, M., Johlander, A., Turc, L., Alho, M., Battarbee, M., Grandin, M., Dubart, M., and Ganse, U.: Hybrid-Vlasov modelling of three-dimensional dayside magnetopause reconnection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13054, https://doi.org/10.5194/egusphere-egu21-13054, 2021.

EGU21-530 | vPICO presentations | ST2.1

The Quadratic Magnetic Gradient and Complete Geometry of Magnetic Field Lines Deduced from Multiple Spacecraft Measurements

Chao Shen, Chi Zhang, Zhaojin Rong, Zuyin Pu, M.alcolm Dunlop, Chris Escoubet, Chris Russell, Gang Zeng, Nian Ren, James Burch, and Yufei Zhou

Topological configurations of the magnetic field play key roles in the evolution of space plasmas. This paper presents a novel algorithm that can estimate the quadratic magnetic gradient as well as the complete geometrical features of magnetic field lines, based on magnetic field and current density measurements by a multiple spacecraft constellation at 4 or more points. The explicit estimators for the linear and quadratic gradients, the apparent velocity of the magnetic structure and the curvature and torsion of the magnetic field lines can be obtained with well predicted accuracies. The feasibility and accuracy of the method have been verified with thorough tests. The algorithm has been successfully applied to exhibit the geometrical structure of a flux rope. This algorithm has wide applications for uncovering a variety of magnetic configurations in space plasmas.

How to cite: Shen, C., Zhang, C., Rong, Z., Pu, Z., Dunlop, M. A., Escoubet, C., Russell, C., Zeng, G., Ren, N., Burch, J., and Zhou, Y.: The Quadratic Magnetic Gradient and Complete Geometry of Magnetic Field Lines Deduced from Multiple Spacecraft Measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-530, https://doi.org/10.5194/egusphere-egu21-530, 2021.

EGU21-1684 | vPICO presentations | ST2.1 | Highlight

3D MHD study of the Earth magnetosphere response during extreme space weather conditions

Jacobo Varela Rodriguez, Sacha A. Brun, Antoine Strugarek, Victor Réville, Filippo Pantellini, and Philippe Zarka

The aim of the study is to analyze the response of the Earth magnetosphere for various space weather conditions and model the effect of interplanetary coronal mass ejections. The magnetopause stand off distance, open-closed field lines boundary and plasma flows towards the planet surface are investigated. We use the MHD code PLUTO in spherical coordinates to perform a parametric study regarding the dynamic pressure and temperature of the solar wind as well as the interplanetary magnetic field intensity and orientation. The range of the parameters analyzed extends from regular to extreme space weather conditions consistent with coronal mass ejections at the Earth orbit. The direct precipitation of the solar wind on the Earth day side at equatorial latitudes is extremely unlikely even during super coronal mass ejections. For example, the SW precipitation towards the Earth surface for a IMF purely oriented in the Southward direction requires a IMF intensity around 1000 nT and the SW dynamic pressure above 350 nPa, space weather conditions well above super-ICMEs. The analysis is extended to previous stages of the solar evolution considering the rotation tracks from Carolan (2019). The simulations performed indicate an efficient shielding of the Earth surface 1100 Myr after the Sun enters in the main sequence. On the other hand, for early evolution phases along the Sun main sequence once the Sun rotation rate was at least 5 times faster (< 440 Myr), the Earth surface was directly exposed to the solar wind during coronal mass ejections (assuming today´s Earth magnetic field). Regarding the satellites orbiting the Earth, Southward and Ecliptic IMF orientations are particularly adverse for Geosynchronous satellites, partially exposed to the SW if the SW dynamic pressure is 8-14 nPa and the IMF intensity 10 nT. On the other hand, Medium orbit satellites at 20000 km are directly exposed to the SW during Common ICME if the IMF orientation is Southward and during Strong ICME if the IMF orientation is Earth-Sun or Ecliptic. The same way, Medium orbit satellites at 10000 km are directly exposed to the SW if a Super ICME with Southward IMF orientation impacts the Earth.

This work was supported by the project 2019-T1/AMB-13648 founded by the Comunidad de Madrid, grants ERC WholeSun, Exoplanets A and PNP. We extend our thanks to CNES for Solar Orbiter, PLATO and Meteo Space science support and to INSU/PNST for their financial support.

How to cite: Varela Rodriguez, J., Brun, S. A., Strugarek, A., Réville, V., Pantellini, F., and Zarka, P.: 3D MHD study of the Earth magnetosphere response during extreme space weather conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1684, https://doi.org/10.5194/egusphere-egu21-1684, 2021.

EGU21-5480 | vPICO presentations | ST2.1

Variations of geomagnetic thresholds of cosmic rays and magnetospheric parameters during different phases  of the storm of November 20, 2003

Elena Vernova, Natalia Ptitsyna, Olga Danilova, and Marta Tyasto

The correlations between variations in the geomagnetic cutoff rigidity of cosmic rays and the Dst and Kp geomagnetic indices and solar-wind and IMF parameters are calculated for the three phases of the magnetic storm of November 20–21, 2003: before the storm and during its main and recovery phases. The correlations are the strongest between variations in the cutoff rigidity and the Dst index during all stages. A significant correlation was recorded with the By component of IMF and the field magnitude B; the correlation with By dominated during the main phase, and the correlation with B was dominant during the recovery phase. There is also a high correlation with the dynamic parameters of solar activity during the main phase, especially with the solar-wind speed.

As far as we know, hysteresis phenomena have been discovered for the first time in the relationship between the cosmic-ray cutoff rigidities and the parameters of the helio- and magnetosphere on the scale of the magnetic storm (with Moscow station as an example). Loop-like patterns formed, because the trajectories of variations in the cutoff rigidities versus the studied parameters during storm intensification (development of current systems) did not coincide with the trajectories during the recovery phase (decay of current systems). The correlations of the cutoff rigidities with Dst and Kp indices were characterized by a narrow hysteresis loop, and their correlations with the IMF parameters were characterized by a wide hysteresis loop. The hysteresis loops for the relationship between the cutoff rigidities and solar-wind density and pressure were disordered.

How to cite: Vernova, E., Ptitsyna, N., Danilova, O., and Tyasto, M.: Variations of geomagnetic thresholds of cosmic rays and magnetospheric parameters during different phases  of the storm of November 20, 2003 , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5480, https://doi.org/10.5194/egusphere-egu21-5480, 2021.

EGU21-3730 | vPICO presentations | ST2.1 | Highlight

The MLT distribution and detailed structure of ring current:  MMS observations

Xin Tan, Malcolm Dunlop, Xiangcheng Dong, Yanyan Yang, and Christopher Russell

The ring current is an important part of the large-scale magnetosphere-ionosphere current system; mainly concentrated in the equatorial plane, between 2-7 RE, and strongly ordered between ± 30 ° latitude. The morphology of ring current directly affects the geomagnetic field at low to middle latitudes. Rapid changes in ring current densities can occur during magnetic storms/sub-storms. Traditionally, the Dst index is used to characterize the intensity of magnetic storms and to reflect the variation of ring current intensity, but this index does not reflect the MLT distribution of ring current. In fact, the ring current has significant variations with MLT, depending on geomagnetic activity, due to the influence of multiple factors; such as, the partial ring current, region 1/region 2 field-aligned currents, the magnetopause current and sub-storm cycle (magnetotail current). The form of the ring current has been inferred from the three-dimensional distribution of ion differential fluxes from neutral atom imaging; however, this technique can not directly obtain the current density distribution (as can be obtained using multi-spacecraft in situ data). Previous in situ estimates of current density have used: Cluster, THEMIS and other spacecraft groups to study the distribution of the ring current for limited ranges of either radial profile, or MLT and MLAT variations. Here, we report on an extension to these studies using FGM data from MMS obtained during the period September 1, 2015 to December 31, 2016, when the MMS orbit and configuration provided good coverage. We employ the curlometer method to calculate the current density, statistically, to analysis the MLT distribution according to different geomagnetic conditions. Our results show the clear asymmetry of the ring current and its different characteristics under different geomagnetic conditions.

How to cite: Tan, X., Dunlop, M., Dong, X., Yang, Y., and Russell, C.: The MLT distribution and detailed structure of ring current:  MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3730, https://doi.org/10.5194/egusphere-egu21-3730, 2021.

EGU21-1780 | vPICO presentations | ST2.1

IMF BX and Dipole Tilt Dependence on Transpolar Arcs

Simon Thor, Anita Kullen, and Lei Cai

Transpolar arcs (TPAs) are predicted by many models to appear in both hemispheres, as so-called conjugate TPAs. However, some observations have suggested that this is not always the case, and that there is an IMF Bx dependence on whether TPAs appear on both hemispheres or not. Specifically, it has been suggested that TPAs only appear on the northern hemisphere for negative IMF BX and vice versa for positive IMF BX. Furthermore, a positive Earth dipole tilt is predicted to have a similar effect on TPA occurrences as a negative IMF BX and vice versa. It is also known that TPAs appear on different locations on the auroral oval, i.e., dawn-, dusk- or both sides of the oval, depending on IMF BY. However, the role of IMF BX and IMF BZ for the TPA location remains unclear, with some previous observations suggesting a correlation with IMF BX.

In this study, we investigate the influence of IMF BX and dipole tilt on TPAs by statistically analyzing observational data. We analyze TPA datasets from four previous studies, as well as our own TPA dataset, created from DMSP satellite measurements. At first glance, the data suggests that there is a strong correlation between both IMF BX and dipole tilt, and TPA observations in a specific hemisphere. However, when normalizing the data to the solar wind distribution and when taking observational bias into account, this correlation disappears. We therefore conclude that there is no clear correlation between neither IMF BX nor dipole tilt and in which hemisphere a TPA appears. We further analyze four of the five datasets with respect to dawn-dusk appearances of TPAs and its correlation to IMF BX, BY and BZ. Here, the results for the datasets mostly agree with previous observations. Finally, we discuss the potential causes for the few non-conjugate TPAs, by studying our own TPA dataset in further detail.

How to cite: Thor, S., Kullen, A., and Cai, L.: IMF BX and Dipole Tilt Dependence on Transpolar Arcs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1780, https://doi.org/10.5194/egusphere-egu21-1780, 2021.

EGU21-809 | vPICO presentations | ST2.1 | Highlight

Magnetospheric reconfiguration during the substorm cycle as inferred from the data-based modeling.

Nikolai Tsyganenko, Varvara Andreeva, Mikhail Sitnov, Jesper Gjerloev, Xiangning Chu, and Oleg Troshichev

First results are presented of reconstructing the evolution of magnetospheric configurations through the full cycle of isolated substorms. The modeling covers the low- and mid-latitude magnetosphere in the range of radial distances from 2 to 20 Re and is based on a synthesis of (1) a high-resolution representation of the magnetic field by cylindrical basis functions, (2) the ever largest pool of magnetospheric and interplanetary data spanning the last quarter century (1995-2019), (3) an archive of concurrent ground-based indices and their temporal trends, quantifying the geomagnetic activity over the full range of latitudes, including the low-latitude ring current SMR-index, the midlatitude positive bay MPB-index, the auroral SML-index, and the polar cap PC-index, (4) the data-mining nearest-neighbour (NN) technique of the data selection and weighting in the geometric and parametric spaces. The obtained successive diagrams of magnetic depression/compression, electric current, and field line maps demonstrate all the typical features of the substorm cycle: the initial relatively slow stretching of the nightside tail during the growth phase, followed by its sudden collapse associated with a dramatic disruption of the tail current at R~11-16 Re, and finally a gradual recovery of the configuration after the expansion phase is over.

How to cite: Tsyganenko, N., Andreeva, V., Sitnov, M., Gjerloev, J., Chu, X., and Troshichev, O.: Magnetospheric reconfiguration during the substorm cycle as inferred from the data-based modeling., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-809, https://doi.org/10.5194/egusphere-egu21-809, 2021.

EGU21-827 | vPICO presentations | ST2.1

Micro-scale tearing mode turbulence in the diffusion region during macro-scale evolution of turbulent reconnection

Takuma Nakamura, Hiroshi Hasegawa, Tai Phan, Kevin Genestreti, Richard Denton, and Rumi Nakamura

Magnetic reconnection is a key fundamental process in collisionless plasmas that explosively converts magnetic energy to plasma kinetic and thermal energies through a change of magnetic field topology in an electron-scale central region called the electron diffusion region. Past simulations and observations demonstrated that this process causes efficient energy conversion through the formation of multiple macro-scale or micro-scale magnetic islands/flux ropes. However, how these different spatiotemporal scale phenomena are coupled is still poorly understood. In this study, to investigate the turbulent evolution of magnetic reconnection, we perform a new large-scale fully kinetic simulation of a thin current sheet considering a power-law spectrum of initial fluctuations in the magnetic field as frequently observed in the Earth’s magnetotail. The simulation demonstrates that during a macro-scale evolution of turbulent reconnection, the merging of macro-scale islands results in reduction of the rate of reconnection as well as the aspect ratio of the electron diffusion region. This allows the repeated, quick formation of new electron-scale islands within the electron diffusion region, leading to an efficient energy cascade between macro- and micro-scales. The simulation also demonstrates that a strong electron acceleration/heating occurs during the micro-scale island evolution within the EDR. These new findings indicate the importance of non-steady features of the EDR to comprehensively understand the energy conversion and cascade processes in collisionless reconnection.

How to cite: Nakamura, T., Hasegawa, H., Phan, T., Genestreti, K., Denton, R., and Nakamura, R.: Micro-scale tearing mode turbulence in the diffusion region during macro-scale evolution of turbulent reconnection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-827, https://doi.org/10.5194/egusphere-egu21-827, 2021.

EGU21-8830 | vPICO presentations | ST2.1

Vlasov simulation of electrons in the context of hybrid global models: An eVlasiator approach

Markus Battarbee, Thiago Brito, Markku Alho, Yann Pfau-Kempf, Maxime Grandin, Urs Ganse, Konstantinos Papadakis, Andreas Johlander, Lucile Turc, Maxime Dubart, and Minna Palmroth

Modern investigations of dynamical space plasma systems such as magnetically complicated topologies within the Earth's magnetosphere make great use of supercomputer models as well as spacecraft observations. Space plasma simulations can be used to investigate energy transfer, acceleration, and plasma flows on both global and local scales. Simulation of global magnetospheric dynamics requires spatial and temporal scales achievable currently through magnetohydrodynamics or hybrid-kinetic simulations, which approximate electron dynamics as a charge-neutralizing fluid. We introduce a novel method for Vlasov-simulating electrons in the context of a hybrid-kinetic framework in order to examine the energization processes of magnetospheric electrons. Our extension of the Vlasiator hybrid-Vlasov code utilizes the global simulation dynamics of the hybrid method whilst modelling snapshots of electron dynamics on global spatial scales and temporal scales suitable for electron physics. Our eVlasiator model is shown to be stable both for single-cell and small-scale domains, and the solver successfully models Langmuir waves and Bernstein modes. We simulate a small test-case section of the near-Earth magnetotail plasma sheet region, reproducing a number of electron distribution function features found in spacecraft measurements.

How to cite: Battarbee, M., Brito, T., Alho, M., Pfau-Kempf, Y., Grandin, M., Ganse, U., Papadakis, K., Johlander, A., Turc, L., Dubart, M., and Palmroth, M.: Vlasov simulation of electrons in the context of hybrid global models: An eVlasiator approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8830, https://doi.org/10.5194/egusphere-egu21-8830, 2021.

EGU21-14350 | vPICO presentations | ST2.1

Multiscale analysis of a current sheet embedded in a fast earthward flow during a substorm event detected by MMS

Olivier Le Contel, Alessandro Retino, Alexandra Alexandrova, Rumi Nakamura, Soboh Alqeeq, Thomas Chust, Laurent Mirioni, Filomena Catapano, Christian Jacquey, Sergio Toledo, Julia Stawarz, Katherine Goodrich, Daniel J. Gershman, Stephen A. Fuselier, Joey Mukherjee, Narges Ahmadi, Daniel Graham, Matthew Argall, David Fischer, and Shiyong Huang and the MMS team

In July 2017, the MMS constellation was evolving in the magnetotail with an apogee of 25 Earth radii and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23 rd of July around 16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static state. Then, MMS
suddenly entered in the central plasma sheet and detected the local onset of a small substorm as indicated by the AE index (~400 nT). Fast earthward plasma flows were measured for about 1 hour starting with a period of quasi-steady flow and followed by a saw-tooth like series of plasma jets (“bursty bulk flows”). In the present study, we focus on a short sequence related to an ion scale current sheet crossing embedded in a fast earthward flow. We analyse in detail two other kinetic structures in the vicinity of this current sheet: an ion-scale flux rope and an electron vortex magnetic hole and discuss the Ohm’s law and conversion energy processes.

How to cite: Le Contel, O., Retino, A., Alexandrova, A., Nakamura, R., Alqeeq, S., Chust, T., Mirioni, L., Catapano, F., Jacquey, C., Toledo, S., Stawarz, J., Goodrich, K., Gershman, D. J., Fuselier, S. A., Mukherjee, J., Ahmadi, N., Graham, D., Argall, M., Fischer, D., and Huang, S. and the MMS team: Multiscale analysis of a current sheet embedded in a fast earthward flow during a substorm event detected by MMS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14350, https://doi.org/10.5194/egusphere-egu21-14350, 2021.

EGU21-11118 | vPICO presentations | ST2.1

Investigation of energy conversion processes and wave activity related to dipolarization fronts observed by MMS

Soboh Alqeeq, Olivier Le Contel, Patrick Canu, Alessandro Retino, Thomas Chust, Alexandra Alexandrova, Laurent Mirioni, Suleiman Baraka, Louis Richard, Yuri Khotyaintsev, Rumi Nakamura, Frederick Wilder, Narges Ahmadi, Hanying Wei, Matthew Argall, David Fischer, Daniel Gershman, James Burch, Roy Torbert, and Barbara Giles and the MMS Team

In the present work, we consider four dipolarization front (DF) events detected by MMS spacecraft in the Earth’s magnetotail during a substorm on 23rd of July 2017 between 16:05 and 17:19 UT. From their ion scale properties, we show that these four DF events embedded in fast Earthward plasma flows have classical signatures with increases of Bz, velocity and temperature and a decrease of density across the DF. We compute and compare current densities obtained from magnetic and particle measurements and analyse the Ohm’s law. Then we describe the wave activity related to these DFs. We investigate energy conversion processes via J.E calculations and estimate the importance of the electromagnetic energy flow by computing the divergence of the Poynting vector. Finally we discuss the electromagnetic energy conservation in the context of these DFs.

How to cite: Alqeeq, S., Le Contel, O., Canu, P., Retino, A., Chust, T., Alexandrova, A., Mirioni, L., Baraka, S., Richard, L., Khotyaintsev, Y., Nakamura, R., Wilder, F., Ahmadi, N., Wei, H., Argall, M., Fischer, D., Gershman, D., Burch, J., Torbert, R., and Giles, B. and the MMS Team: Investigation of energy conversion processes and wave activity related to dipolarization fronts observed by MMS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11118, https://doi.org/10.5194/egusphere-egu21-11118, 2021.

EGU21-8873 | vPICO presentations | ST2.1

Statistical Investigation of Fluctuations around the Lower Hybrid Frequency at the Dipolarization Front in the near-Earth Magnetotail

Martin Hosner, Rumi Nakamura, Takuma Nakamura, Evgeny Panov, Daniel Schmid, James L. Burch, Barbara L. Giles, and Roy Torbert

At the leading edges of reconnection jets in the magnetotail, commonly referred to as Dipolarization Fronts (DF), strong fluctuations in the electric field δE and the magnetic field δB are observed. Recent results from a fully kinetic PIC simulation (Nakamura et al., 2019) demonstrate that a Lower Hybrid Drift Instability-driven (LHDI) disturbance at the DF front region can be responsible for these electric and magnetic field fluctuations. These findings are well in line with an observed event (Liu at al., 2018), comparable to the simulated plasma conditions. However, a general experimental validation under a wider range of conditions yet remains absent. The present work experimentally investigates δE and δB fluctuations for a selection of DF events between July 2017 and September 2018 using Magnetospheric Multiscale (MMS) mission data. Aiming for a statistical approach, the analysis consists of a quantitative evaluation of dynamic wave power spectra of both δE and δB in the lower hybrid frequency range. Furthermore, propagation properties of associated wave structures are analyzed and related to present plasma conditions. Findings include the identification of peak wave power occurrence times relative to the magnetic DF structure and the associated density gradient.

How to cite: Hosner, M., Nakamura, R., Nakamura, T., Panov, E., Schmid, D., Burch, J. L., Giles, B. L., and Torbert, R.: Statistical Investigation of Fluctuations around the Lower Hybrid Frequency at the Dipolarization Front in the near-Earth Magnetotail, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8873, https://doi.org/10.5194/egusphere-egu21-8873, 2021.

ST2.2 – Combined session: global magnetospheric dynamics and dayside magnetosphere interaction

EGU21-8571 | vPICO presentations | ST2.2 | Highlight

A kinetic formation model of foreshock transients

Terry Zixu Liu, Xin An, Hui Zhang, and Drew Turner

Foreshock transients are ion kinetic structures in the ion foreshock. Due to their dynamic pressure perturbations, they can disturb the bow shock, magnetosheath, magnetopause, and magnetosphere-ionosphere system. Recent studies found that they can also accelerate particles through shock drift acceleration, Fermi acceleration, betatron acceleration, and magnetic reconnection. Although foreshock transients are important, how they form is still not fully understood. Using particle-in-cell simulations and MMS observations, we propose a physical formation process that the positive feedback of demagnetized foreshock ions on the varying magnetic field caused by the foreshock ion Hall current enables an “instability” and the growth of the structure.      

How to cite: Liu, T. Z., An, X., Zhang, H., and Turner, D.: A kinetic formation model of foreshock transients, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8571, https://doi.org/10.5194/egusphere-egu21-8571, 2021.

Hot flow anomalies (HFAs), which are frequently observed near the Earth’s bow shock, are phenomena resulting from the interaction between interplanetary discontinuities and the Earth’s bow shock. Such transient phenomena upstream of the bow shock can cause significant deformation of the bow shock and the magnetopause, generating traveling convection vortices, field-aligned currents, and ULF waves in the Earth’s magnetosphere. A large HFA lasting about 16 minutes was observed by MMS on November 19, 2015. In this study, energetic particle sounding method with high time resolution (150 ms) Fast Plasma Investigation (FPI) data is used to determine the deformed magnetopause distances, orientations, and structures during the interval when MMS crossed the deformed magnetopause. The estimated radius of curvature of the deformed magnetopause is 2.2 RE.

How to cite: Zhang, H.: Energetic Particle Sounding of the Magnetopause Deformed by a Hot Flow Anomaly: MMS Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1954, https://doi.org/10.5194/egusphere-egu21-1954, 2021.

EGU21-3424 | vPICO presentations | ST2.2 | Highlight

Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby

Wei-Jie Sun, James Slavin, Rumi Nakamura, Daniel Heyner, and Johannes Mieth

BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The BepiColombo mission consists of two spacecraft, which are the Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (Mio). The mission made its first planetary flyby, which is the only Earth flyby, on 10 April 2020, during which several instruments collected measurements. In this study, we analyze MPO magnetometer (MAG) observations of Flux Transfer Events (FTEs) in the magnetosheath and the structure of the subsolar magnetopause near the  flow stagnation point. The magnetosheath plasma beta was high with a value of ~ 8 and the interplanetary magnetic field (IMF) was southward with a clock angle that decreased from ~ 100 degrees to ~ 150 degrees.  As the draped IMF became increasingly southward several of the flux transfer event (FTE)-type flux ropes were observed. These FTEs traveled southward indicating that the magnetopause X-line was located northward of the spacecraft, which is consistent with a dawnward tilt of the IMF. Most of the FTE-type flux ropes were in ion-scale, <10 s duration, suggesting that they were newly formed. Only one large-scale FTE-type flux rope, ~ 20 s, was observed. It was made up of two successive bipolar signatures in the normal magnetic field component, which is evidence of coalescence at a secondary reconnection site. Further analysis demonstrated that the dimensionless reconnection rate of the re-reconnection associated with the coalescence site was ~ 0.14. While this investigation was limited to the MPO MAG observations, it strongly supports a key feature of dayside reconnection discovered in the Magnetospheric Multiscale mission, the growth of FTE-type flux ropes through coalescence at secondary reconnection sites.

How to cite: Sun, W.-J., Slavin, J., Nakamura, R., Heyner, D., and Mieth, J.: Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3424, https://doi.org/10.5194/egusphere-egu21-3424, 2021.

EGU21-4490 | vPICO presentations | ST2.2 | Highlight

Magnetosheath high speed jets and foreshock transients observed by Cluster and MMS

C.-Philippe Escoubet and the Cluster-MMS team

Magnetosheath High Speed Jets (HSJs) are regularly observed downstream of the Earth’s bow shock. Determining their origin from spacecraft observations is however a challenge since (1) L1 solar wind monitors are usually used with their inherent inaccuracy when plasma and magnetic data are propagated to the bow shock, (2) the number of measurement points around the bow shock are always limited. Various mechanisms have been proposed to explain HSJs such as bow shock ripples, solar wind discontinuities, foreshock transients, pressure pulses or nano dust clouds and it is difficult to relate these to HSJs with the lack of simultaneous measurements near the bow shock and immediately upstream.  We will use a special Cluster campaign, where one spacecraft was lagged 8 hours behind the three other spacecraft, to obtain near-Earth solar wind measurements upstream of the bow shock, together with simultaneous measurements in the magnetosheath. The event of interest is first observed by ACE on 13 January 2019 as a short 10 minutes period of IMF-Bx dominant (cone angle around 140 deg.). This IMF-Bx dominant period is also observed, one hour later, by THEMIS B and C (ARTEMIS) and Geotail, which were at 60 and 25 RE from Earth on the dawnside. Cluster 1 and Cluster 2 just upstream of the bow shock, at 17 RE from Earth, observed also such IMF-Bx dominant period together with energetic ions reflected from the bow shock and foreshock transients. Preliminary analysis indicate that these transients would be hot flow anomalies. Finally, Cluster 3 and 4 and MMS1-4, a few RE from each other downstream of the shock, observed a turbulent magnetosheath with HSJs for 15 minutes. The HSJ characteristics are investigated with the constellation of 6 spacecraft, as well as their relation to hot flows anomalies observed upstream.

How to cite: Escoubet, C.-P. and the Cluster-MMS team: Magnetosheath high speed jets and foreshock transients observed by Cluster and MMS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4490, https://doi.org/10.5194/egusphere-egu21-4490, 2021.

EGU21-7921 | vPICO presentations | ST2.2

Magnetosheath jet evolution as a function of lifetime: Global hybrid-Vlasov simulations compared to MMS observations

Minna Palmroth, Savvas Raptis, Tomas Karlsson, Jonas Suni, Lucile Turc, Andreas Johlander, Urs Ganse, Yann Pfau-Kempf, Xochitl Blanco-Cano, Mojtaba Akhavan-Tafti, Markus Battarbee, Maxime Grandin, Maxime Dubart, Vertti Tarvus, and Adnane Osmane

Magnetosheath jets are regions of high dynamic pressure, which can traverse from the bow shock towards the magnetopause. Recent modelling efforts, limited to a single jet and a single set of upstream conditions, have provided the first estimations about how the jet parameters behave as a function of position within the magnetosheath. Here we expand the earlier results by making the first statistical investigation of the jet dimensions and parameters as a function of their lifetime within the magnetosheath. To verify the simulation behaviour, we first identify jets from Magnetosphere Multi-Scale (MMS) spacecraft data (6142 in total) and confirm the Vlasiator jet general behaviour using statistics of 924 simulated individual jets. We find that the jets in the simulation are in excellent quantitative agreement with the observations, confirming earlier findings related to jets using Vlasiator. The jet density, dynamic pressure and magnetic field intensity show a sharp jump at the bow shock, which decreases towards the magnetopause. The jets appear  compressive and cooler than the magnetosheath at the bow shock, while during their propagation towards the magnetopause they thermalise. Further, the shape of the jets flatten as they progress through the magnetosheath. They are able to maintain their flow velocity and direction within the magnetosheath flow pattern, and they end up preferentially to the side of the magnetosheath behind the quasi-parallel shock. Finally, we find that Vlasiator jets during low solar wind Alfvén Mach number (MA) are shorter in duration, smaller in their extent, and weaker in terms of dynamic pressure and magnetic field intensity as compared to the jets during high MA. 

How to cite: Palmroth, M., Raptis, S., Karlsson, T., Suni, J., Turc, L., Johlander, A., Ganse, U., Pfau-Kempf, Y., Blanco-Cano, X., Akhavan-Tafti, M., Battarbee, M., Grandin, M., Dubart, M., Tarvus, V., and Osmane, A.: Magnetosheath jet evolution as a function of lifetime: Global hybrid-Vlasov simulations compared to MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7921, https://doi.org/10.5194/egusphere-egu21-7921, 2021.

EGU21-11325 | vPICO presentations | ST2.2

Foreshock compressive structure-magnetosheath jet coupling in a global hybrid-Vlasov simulation

Jonas Suni, Minna Palmroth, Lucile Turc, Markus Battarbee, Andreas Johlander, Vertti Tarvus, Markku Alho, Maxime Dubart, Urs Ganse, Maxime Grandin, Konstantinos Papadakis, and Yann Pfau-Kempf

Magnetosheath jets are a class of phenomena usually defined as pulses of high dynamic pressure in the magnetosheath, but the details of their origins are currently unclear. Many theories on the origin of magnetosheath jets have been developed, such as bow shock rippling and foreshock structures. The usefulness of spacecraft data in studying some of them is limited, due to the transient and localised nature of jets. We use the 5D global hybrid-Vlasov simulation Vlasiator in a statistical study to investigate the relationship between compressive structures in the foreshock and magnetosheath jets. Foreshock compressive structures and magnetosheath jets are identified and their evolution over time is tracked. We find that up to 75% of magnetosheath jets forming at the bow shock are associated with foreshock compressive structures impacting the bow shock at the same location. Furthermore, magnetosheath jets that are associated with foreshock compressive structures penetrate deeper into the magnetosheath than jets that are not associated with foreshock compressive structures.

How to cite: Suni, J., Palmroth, M., Turc, L., Battarbee, M., Johlander, A., Tarvus, V., Alho, M., Dubart, M., Ganse, U., Grandin, M., Papadakis, K., and Pfau-Kempf, Y.: Foreshock compressive structure-magnetosheath jet coupling in a global hybrid-Vlasov simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11325, https://doi.org/10.5194/egusphere-egu21-11325, 2021.

EGU21-5635 | vPICO presentations | ST2.2

Propagation properties of foreshock cavitons and spontaneous hot flow anomalies: Statistical results from a global hybrid-Vlasov simulation

Vertti Tarvus, Lucile Turc, Markus Battarbee, Jonas Suni, Xóchitl Blanco-Cano, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Maxime Dubart, Maxime Grandin, Andreas Johlander, Konstantinos Papadakis, and Minna Palmroth

Foreshock cavitons are transient structures forming in Earth's foreshock as a result of non-linear interaction of ultra-low frequency waves. Cavitons are characterised by simultaneous density and magnetic field depressions with sizes of the order of 1 Earth radius. These transients are advected by the solar wind towards the bow shock, where they may accumulate shock-reflected suprathermal ions and become spontaneous hot flow anomalies (SHFAs), which are characterised by an enhanced temperature and a perturbed bulk flow inside them.
    Both spacecraft measurements and hybrid simulations have shown that while cavitons and SHFAs are carried towards the bow shock by the solar wind, their motion in the solar wind rest frame is directed upstream. In this work, we have made a statistical analysis of the propagation properties of cavitons and SHFAs using Vlasiator, a hybrid-Vlasov simulation model. In agreement with previous studies, we find the transients propagating upstream in the solar wind rest frame. Our results show that the solar wind rest frame motion of cavitons is aligned with the direction of the interplanetary magnetic field, while the motion of SHFAs deviates from this direction. We find that SHFAs have a faster solar wind rest frame propagation speed than cavitons, which is due to an increase in the sound speed near the bow shock, affecting the speed of the waves in the foreshock.

How to cite: Tarvus, V., Turc, L., Battarbee, M., Suni, J., Blanco-Cano, X., Ganse, U., Pfau-Kempf, Y., Alho, M., Dubart, M., Grandin, M., Johlander, A., Papadakis, K., and Palmroth, M.: Propagation properties of foreshock cavitons and spontaneous hot flow anomalies: Statistical results from a global hybrid-Vlasov simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5635, https://doi.org/10.5194/egusphere-egu21-5635, 2021.

EGU21-14535 | vPICO presentations | ST2.2

Propagation characteristics of hot flow anomalies

Xiaoqiong Zhu, Mengmeng Wang, Quanqi Shi, Hui Zhang, Anmin Tian, Shutao Yao, Ruilong Guo, Ji Liu, Shichen Bai, Shuai Zhang, Wensai Shang, and Zhe Niu

Hot flow anomalies (HFAs), characterized by heated plasma and flow deflection, are frequently observed near Earth’s and other planetary bow shocks. There are two kinds of HFAs, classic HFAs formed by the interaction of tangential discontinuities (TD) and the bow shock, and spontaneous HFAs (SHFAs) which are not associated with discontinuties. A statistical study of the propagation characteristics of HFA edges has been performed base on 19 classic HFAs and 23 SHFAs with one-dimensional edges observed by Cluster from 2001 to 2010. The propagation velocity and normal direction of each edge are calculated using the timing method, the minimum directional difference (MDD) method, and the spatial-temporal difference (STD) method. The angle between the leading edge normal and the corresponding TD normal is less than 30 degrees for 93% of the classic HFAs. The angle between the edge normal and background magnetic field is near 90 degrees for 74% of the SHFAs. Observations indicate that the leading edge of the classic HFAs propagates along the same direction as the driving TD and the SHFAs propagate perpendicular to the background magnetic field. Furthermore, we find that all 42 HFAs propagate toward the Earth in the spacecraft frame as expected. However, in the solar wind frame HFAs have different propagation directions (i.e., toward the Earth, the Sun or be stationary in the solar wind frame).

How to cite: Zhu, X., Wang, M., Shi, Q., Zhang, H., Tian, A., Yao, S., Guo, R., Liu, J., Bai, S., Zhang, S., Shang, W., and Niu, Z.: Propagation characteristics of hot flow anomalies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14535, https://doi.org/10.5194/egusphere-egu21-14535, 2021.

EGU21-6971 | vPICO presentations | ST2.2

Global structure and properties of ULF waves in the ion foreshock observed in a Hybrid-Vlasov simulation.

Kun Zhang, Seth Dorfman, Urs Ganse, Lucile Turc, and Chen Shi

Energetic ions reflected and accelerated by the Earth’s bow shock travel back into the solar wind, forming the ion foreshock, and generate ultralow frequency (ULF) waves. Such ULF waves have been extensively studied over the past few decades using satellite measurements. However, the spatial variations of the wave properties cannot be well resolved by satellite observations due to the limited number of available spacecraft simultaneously inside the ion foreshock. Therefore, we conduct a global survey of the ULF wave properties in the ion foreshock through analysis of a Vlasiator (a hybrid-Vlasov code) simulation. Previous studies validated that this simulation well reproduced Earth’s foreshock and the ULF waves in it [e.g., Palmroth et al., 2015; Turc et al., 2018]. Here we focus on the wave properties, including frequency, ellipticity, polarization, wave normal angle and growth rate, of the well-known 30-sec wave and its multiple harmonics. We report that the ULF waves near the edge of the foreshock are very different from the waves in the center of the foreshock. We also show the related ion distribution and discuss the connection between the observed ion beams and ULF waves, aiming at understanding the cause of the observed differences in wave properties.

 

This study is supported by NASA grant 80NSSC20K0801. Vlasiator is developed by the European Research Council Starting grant 200141-QuESpace, and Consolidator grant GA682068-PRESTISSIMO received by the Vlasiator PI. Vlasiator has also received funding from the Academy of Finland. See www.helsinki.fi/vlasiator

 

Palmroth, M., et al. (2015), ULF foreshock under radial IMF: THEMIS observations and global kinetic simulation Vlasiator results compared, J. Geophys. Res. Space Physics, 120, 8782–8798, doi:10.1002/2015JA021526.

Turc, L., Ganse, U., Pfau-Kempf, Y., Hoilijoki, S., Battarbee, M., Juusola, L., et al. (2018). Foreshock properties at typical and enhanced interplanetary magnetic field strengths: results from hybrid-Vlasov simulations. Journal of Geophysical Research: Space Physics, 123, 5476–5493. doi:10.1029/2018JA025466.

How to cite: Zhang, K., Dorfman, S., Ganse, U., Turc, L., and Shi, C.: Global structure and properties of ULF waves in the ion foreshock observed in a Hybrid-Vlasov simulation., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6971, https://doi.org/10.5194/egusphere-egu21-6971, 2021.

EGU21-3433 | vPICO presentations | ST2.2 | Highlight

Shock-induced radiation belt dynamics: Coordinated observations of drift echoes and ULF modulations in the dayside magnetosphere 

Xingran Chen, Qiugang Zong, Ying Liu, Yixin Hao, Suiyan Fu, Jie Ren, and Chao Yue

We employ conjunctive observations of particle fluxes and electromagnetic fields in the solar wind, magnetosheath, and dayside magnetosphere to investigate the radiation belt dynamics in response to the impingement of a fast forward interplanetary shock on 7 September 2017. Particularly, drift echoes associated with the one-kick acceleration caused by the shock-induced magnetosonic pulse and oscillations in the Pc 4 range associated with the azimuthally localized ULF waves are identified concurrently in the in-situ particle measurements obtained by the twin Van Allen Probes in the dayside outer radiation belt. Based on this observational evidence, we demonstrate that the radiation bet can be efficiently disturbed via the two mechanisms simultaneously by the shock arrival. We also depict the characteristic features to distinguish between the two mechanisms from an observational approach.

How to cite: Chen, X., Zong, Q., Liu, Y., Hao, Y., Fu, S., Ren, J., and Yue, C.: Shock-induced radiation belt dynamics: Coordinated observations of drift echoes and ULF modulations in the dayside magnetosphere , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3433, https://doi.org/10.5194/egusphere-egu21-3433, 2021.

EGU21-14176 | vPICO presentations | ST2.2

Comparison of External ULF wave Sources in Driving Radiation Belt Electron Dynamics

Zhe Niu, Alexander Degeling, and Quanqi Shi

For the study of Earth's radiation belts, an outstanding problem is the identification and prediction of dynamic variations of Earth's trapped energetic particles, in particular during geomagnetic storms. Statistical studies indicate that different types of geomagnetic storms (e.g. CIR and CME driven storms) have differing efficiencies in their ability to cause energization, transport and loss of energetic particles. This is most likely due to differences in the dominant mechanisms by which particles are affected between the storm types, and the locations within the magnetosphere where these mechanisms operate. For example, the dominant external generation mechanism for Pc5 ULF waves during CME driven storms may be magnetopause buffeting across the dayside, while for CIR driven storms the Kelvin-Helmholtz Instability (KHI) along the morning and evening flanks is more likely dominant. This changes the location and efficiency by which ULF waves can resonantly interact with radiation belt particles in these two storm types.

In this study, we use a 2D MHD wave model to investigate how the dominant generation mechanism in the case of CIR and CME driven storms determines the ability for externally generated wave power to penetrate deeply into the magnetosphere. In order to do this, we model ideal MHD waves in a 2D box model magnetosphere with a parabolic magnetopause boundary layer. We consider how fluctuations in dynamic pressure generate magnetopause buffeting perturbations that launch MHD fast mode waves, following the approach of Degeling et al., JGR 2011. We also include in our simulation a simple model for magnetosheath flow, and calculate the local linear KHI growth rate for perturbations along the magnetopause flanks as a function of frequency to provide a KHI driven wave source.

How to cite: Niu, Z., Degeling, A., and Shi, Q.: Comparison of External ULF wave Sources in Driving Radiation Belt Electron Dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14176, https://doi.org/10.5194/egusphere-egu21-14176, 2021.

EGU21-14090 | vPICO presentations | ST2.2

Electron Pitch Angle Distributions in the Compressional Pc5 Waves

Xiao Ma, Anmin Tian, Quanqi Shi, Shichen Bai, Ji Liu, Ruilong Guo, and Shutao Yao

In the two flanks of the Earth’s magnetosphere, the compressional Pc5 waves are often observed. Previous study suggests that these waves are usually excited by plasma pressure anisotropy such as drift mirror instability. Interestingly, whistler mode waves are often observed in the magnetic trough regions of the compressional Pc5 waves. In this study, we use 10 years (2007-2016) THEMIS A data to study the electron distributions in the compressional Pc5 waves associated with the whistler mode waves. We find three typical electron pitch angle distributions (PADs) in these compressional waves: cigar-shape, donut-shape and pancake-shape. They predominantly occur at tens to hundreds eV, several keV and >10 keV, respectively. The interaction effects between the electrons and whistler waves inside the magnetic troughs are stressed in understanding the formation of these PADs.

How to cite: Ma, X., Tian, A., Shi, Q., Bai, S., Liu, J., Guo, R., and Yao, S.: Electron Pitch Angle Distributions in the Compressional Pc5 Waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14090, https://doi.org/10.5194/egusphere-egu21-14090, 2021.

EGU21-8603 | vPICO presentations | ST2.2

Study of Pc5 compressional waves by MMS observations

Anmin Tian

Pc5 compressional waves are frequently observed in the outer magnetosphere with mirror mode features. Due to the limited spatial coverage of spacecraft, their overall structure is still poorly understood. In this work, the wave structure and motion characteristics are statistically investigated based on the MMS data from September to October 2015. During this time period, the apogees of the MMS spacecraft were located in the outer dusk magnetosphere, and the spacecraft has regular tetrahedral configuration that facilitates the application of multi-spacecraft analysis techniques. The magnetic trough boundaries are identified, and their normal direction, current density and velocity of these boundaries are calculated. We found that the magnetic trough has a magnetic bottle topology along the field line. In the r-a plane, the two boundaries has an open angle toward the radial direction.The boundaries mainly move sunward in the GSE XY plane with average speed of ~26km/s. The poloidal Alfven mode is found to be coupling with the compressional mode oscillation. It suggests that our observations could be explained by the theory of drift Alfven ballooning mirror instability.

How to cite: Tian, A.: Study of Pc5 compressional waves by MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8603, https://doi.org/10.5194/egusphere-egu21-8603, 2021.

EGU21-2884 | vPICO presentations | ST2.2

Foreshock ULF fluctuations near the Moon: THEMIS observations

Anna Salohub, Jana Šafránková, and Zdeněk Němeček

The foreshock is a region filled with a turbulent plasma located upstream the Earth’s bow shock where interplanetary magnetic field (IMF) lines are connected to the bow shock surface. In this region, ultra-low frequency (ULF) waves are generated due to the interaction of the solar wind plasma with particles reflected from the bow shock back into the solar wind. It is assumed that excited waves grow and they are convected through the solar wind/foreshock, thus the inner spacecraft (close to the bow shock) would observe larger wave amplitudes than the outer (far from the bow shock) spacecraft. The paper presents a statistical analysis of excited ULF fluctuations observed simultaneously by two closely separated THEMIS spacecraft orbiting the Moon under a nearly radial IMF. We found that ULF fluctuations (in the plasma rest frame) can be characterized as a mixture of transverse and compressional modes with different properties at both locations. We discuss the growth and/or damping of ULF waves during their propagation.

How to cite: Salohub, A., Šafránková, J., and Němeček, Z.: Foreshock ULF fluctuations near the Moon: THEMIS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2884, https://doi.org/10.5194/egusphere-egu21-2884, 2021.

EGU21-7255 | vPICO presentations | ST2.2 | Highlight

Foreshock wave transmission into the magnetosheath and magnetosphere: results from global hybrid-Vlasov simulations

Lucile Turc, Markus Battarbee, Urs Ganse, Andreas Johlander, Yann Pfau-Kempf, Vertti Tarvus, Hongyang Zhou, Markku Alho, Maxime Dubart, Maxime Grandin, Kostis Papadakis, Jonas Suni, and MInna Palmroth

The foreshock, extending upstream of the quasi-parallel shock and populated with shock-reflected particles, is home to intense wave activity in the ultra-low frequency range. The most commonly observed of these waves are the “30 s” waves, fast magnetosonic waves propagating sunward in the plasma rest frame, but carried earthward by the faster solar wind flow. These waves are thought to be the main source of Pc3 magnetic pulsations (10 – 45 s) in the dayside magnetosphere. A handful of case studies with suitable spacecraft conjunctions have allowed simultaneous investigations of the wave properties in different geophysical regions, but the global picture of the wave transmission from the foreshock through the magnetosheath into the magnetosphere is still not known. In this work, we use global simulations performed with the hybrid-Vlasov model Vlasiator to study the Pc3 wave properties in the foreshock, magnetosheath and magnetosphere for different solar wind conditions. We find that in all three regions the wave power peaks at higher frequencies when the interplanetary magnetic field strength is larger, consistent with previous studies. While the transverse wave power decreases with decreasing Alfvén Mach number in the foreshock, the compressional wave power shows little variation. In contrast, in the magnetosheath and the magnetosphere, the compressional wave power decreases with decreasing Mach number. Inside the magnetosphere, the distribution of wave power varies with the IMF cone angle. We discuss the implications of these results for the propagation of foreshock waves across the different geophysical regions, and in particular their transmission through the bow shock.

How to cite: Turc, L., Battarbee, M., Ganse, U., Johlander, A., Pfau-Kempf, Y., Tarvus, V., Zhou, H., Alho, M., Dubart, M., Grandin, M., Papadakis, K., Suni, J., and Palmroth, M.: Foreshock wave transmission into the magnetosheath and magnetosphere: results from global hybrid-Vlasov simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7255, https://doi.org/10.5194/egusphere-egu21-7255, 2021.

EGU21-3643 | vPICO presentations | ST2.2 | Highlight

Kinetic Modeling of the Impact of Solar Wind Discontinuities on the Magnetopause

Jean Berchem, Giovanni Lapenta, Robert L. Richard, Philippe Escoubet, and Simon Wing

An important step in comprehending the effects of solar wind structures on the magnetosphere is to develop an understanding of their impact on the dayside magnetopause.  While most of the time global magnetohydrodynamic (MHD) models describe adequately the large-scale effects of solar wind structures on the magnetopause, recent spacecraft observations in the near Earth solar wind indicate that solar wind discontinuities have plasma features that are often not accurately described by MHD.  In this presentation, we report our progress in gaining a comprehensive understanding of kinetic processes occurring at the magnetopause as solar wind structures impact the dayside magnetosphere. Our approach combines implicit PIC simulations with global MHD simulations of the solar wind-magnetosphere-ionosphere system. The global simulation sets the overall configuration of the magnetosphere, while fields and plasma moments of a sub-domain of the global simulation are used to set initial and boundary conditions of the PIC code. Results are discussed in the context of spacecraft observations.

How to cite: Berchem, J., Lapenta, G., Richard, R. L., Escoubet, P., and Wing, S.: Kinetic Modeling of the Impact of Solar Wind Discontinuities on the Magnetopause, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3643, https://doi.org/10.5194/egusphere-egu21-3643, 2021.

EGU21-862 | vPICO presentations | ST2.2

MMS observations of the KHI during southward IMF and comparison to 2D and 3D simulations

Kevin Alexander Blasl, Rumi Nakamura, Takuma Nakamura, and Ferdinand Plaschke

The Kelvin-Helmholtz instability (KHI) is one of the main drivers of plasma transport across Earth’s magnetopause. Statistical studies have shown that it occurs much more frequently during periods of northward interplanetary magnetic field (IMF). Here we present MMS observations of the instability during southward IMF on September 23, 2017.

Two MMS intervals featuring plasma parameters fulfilling the instability criterion for KH waves are studied. A boundary normal vector analysis indicates the presence of linear waves and a magnetosheath side crossing of a vortex in these intervals. Correspondingly, clear signatures of Low Density Faster Than Sheath (LDFTS) plasma, in general located at the magnetosheath side of vortices, are found indicating a rolled-up vortex structure. Specific variations of the ion bulk velocity and the total pressure strengthen the argument for the detection of linear waves. Interestingly, the vortex-like event features a constant total pressure, which is explained by a magnetosheath side crossing of a vortex structure.

The MMS observations are compared to simulation results from 2D and 3D fully kinetic PIC simulations performed using the plasma parameters observed around the two MMS events. A linearity analysis of the fastest growing mode of the 2D simulation results suggests the detection of the vortex-like event in the early nonlinear phase.

The simulation further demonstrates that the secondary instabilities such as the lower-hybrid drift instability (LHDI) and the Rayleigh-Taylor instability (RTI) grow near the edge of the non-linearly developed KH vortex and strongly disturb the vortex structure. The elongated vortex arm due to the RTI together with disturbances of the vortex structure can also lead to the observed constant total pressure in MMS data. Given the above quantitative consistencies of the simulation and the MMS observations in the earlier growth phase of the KHI, these results suggest that the secondary modes may reduce the observation probability of KH wave/vortex structures during southward IMF.

How to cite: Blasl, K. A., Nakamura, R., Nakamura, T., and Plaschke, F.: MMS observations of the KHI during southward IMF and comparison to 2D and 3D simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-862, https://doi.org/10.5194/egusphere-egu21-862, 2021.

EGU21-13992 | vPICO presentations | ST2.2

Unusual Location of the Geotail Magnetopause Near Lunar Orbit: A Case Study

Wensai Shang, Binbin Tang, Quanqi Shi, and Et al

The Earth's magnetopause is highly variable in location and shape and is modulated by solar wind conditions. On 8 March 2012, the ARTEMIS probes were located near the tail current sheet when an interplanetary shock arrived under northward interplanetary magnetic field conditions and recorded an abrupt tail compression at ∼(-60, 0, -5) Re in Geocentric Solar Ecliptic coordinate in the deep magnetotail. ~ 10 minutes later, the probes crossed the magnetopause many times within an hour after the oblique interplanetary shock passed by. The solar wind velocity vector downstream from the shock was not directed along the Sun-Earth line but had a significant Y component. We propose that the compressed tail was pushed aside by the appreciable solar wind flow in the Y direction. Using a virtual spacecraft in a global magnetohydrodynamic (MHD) simulation, we reproduce the sequence of magnetopause crossings in the X-Y plane observed by ARTEMIS under oblique shock conditions, demonstrating that the compressed magnetopause is sharply deflected at lunar distances in response to the shock and solar wind Vy effects. The results from two global MHD simulations show that the shocked magnetotail at lunar distances is mainly controlled by the solar wind direction with a timescale of about a quarter hour, which appears to be consistent with the windsock effect. The results also provide some references for investigating interactions between the solar wind/magnetosheath and lunar nearside surface during full moon time intervals, which should not happen in general.

How to cite: Shang, W., Tang, B., Shi, Q., and al, E.: Unusual Location of the Geotail Magnetopause Near Lunar Orbit: A Case Study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13992, https://doi.org/10.5194/egusphere-egu21-13992, 2021.

EGU21-10648 | vPICO presentations | ST2.2

On the Bow-Shock dynamics in response to a Quasi-Perpendicular interaction with different Solar Wind conditions

Emanuele Cazzola, Dominique Fontaine, and Philippe Savoini

This work will be giving new insights into the global Quasi-Perpendicular interaction effects of the Solar Wind with a realistic three-dimensional terrestrial-like curved Bow Shock (BS) by means of hybrid computer simulations.
The Bow-Shock profoundly changes its behavior for different incoming Solar Wind conditions. For Alfvénic Mach numbers greater than a specific threshold, the Bow-Shock shows an intense rippling phenomenon propagating along its surface, as well as the formation of a set of waves in the near-Earth flanks.
A similar rippling has been observed from different independent in-situ satellite crossings, as well as studied with ad-hoc computer simulations configured with 2D-planar shocks, conclusively confirming the highly kinetic nature of this phenomenon. Yet, the possible effects of a global three-dimensional curved interaction are still poorly described.
As such, we have performed a series of 3D simulations at different Alfvénic Mach numbers, different plasma beta - ratio between the thermal to the magnetic pressures - and different incoming Interplanetary Magnetic Field (IMF) configurations with the hybrid code LatHyS, which was already successfully used for similar past analyses.
Particularly, we have found that the ripples follow a pattern not directly driven by the IMF direction as initially expected, but rather a Nose-to-Flanks propagation with the rippling onset region  being significantly displaced from the nose position. Additionally, this phenomenon seems to be mainly confined to the plane on where the IMF direction lies, with the perpendicular cross-sections showing only a slight oscillation.
Finally, we have observes a significant ions acceleration in the local perpendicular directions along the flanks modulations, which is most likely related to the local IMF-BS normal fluctuations occurring in the ripples boundary.

How to cite: Cazzola, E., Fontaine, D., and Savoini, P.: On the Bow-Shock dynamics in response to a Quasi-Perpendicular interaction with different Solar Wind conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10648, https://doi.org/10.5194/egusphere-egu21-10648, 2021.

EGU21-15357 | vPICO presentations | ST2.2

MMS observations of explosive filamentary current within two adjacent ion scale flux ropes

Yuchen Xiao, Shutao Yao, Ruilong Guo, Quanqi Shi, Anmin Tian, Shichen Bai, and Ji Liu

Flux ropes have attracted extensive attention due to their importance in studying instantaneous magnetic reconnection over the past years. Recently, with the improvement of high spatio-temporal resolution measurements, kinetic-scale flux ropes have been detected. However, their generation and energy energization are still unclear. In this study, electron-scale filamentary currents within two adjacent ion scale flux ropes are observed using MMS data. We find that:

1. Intense and explosive filamentary currents in parallel and perpendicular directions are found inside the flux ropes.

2. The electron pitch angle distribution appears "X" like shape, and could be caused by the electron acceleration.

3. The filamentary current appears in the center of the "X" distribution.

The filamentary currents are important and are considered to be the evidence of secondary reconnection [Wang et al., 2020]. The observations in our study are important to reveal the particle acceleration and energy dissipation in magnetic reconnection.

How to cite: Xiao, Y., Yao, S., Guo, R., Shi, Q., Tian, A., Bai, S., and Liu, J.: MMS observations of explosive filamentary current within two adjacent ion scale flux ropes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15357, https://doi.org/10.5194/egusphere-egu21-15357, 2021.

EGU21-14077 | vPICO presentations | ST2.2

The statistical research on the Kinetic- scale magnetic hole in magnetosheath

Zongshun Yue, Ji Liu, Shutao Yao, Quanqi Shi, Ruilong Guo, Anmin Tian, and Shichen Bai

Kinetic- scale magnetic hole (KSMH) is a kind of structure whose spatial scale is only or smaller than the ion gyroradius and the magnetic field intensity shows rapid decrease in the observation. Recently, with the improvement of high spatio-temporal resolution measurements, previous studies have revealed some physical processes at the small scale, like electron energization, energy dissipation, wave-particle interaction and the turbulence. However, these studies on KSMHs have not touched on the generation and evolution of these structures due to limitations in the analysis methods used. In this work, using a series of KSMHs events observed by MMS and a new method to analyze the size of the hole, we are studying the relationship between the size of KSMHs and their spatial position in the magnetosheath statistically, and try to find the headstream of this type of structures and reveal their evolution process when they propagate with plasma flow.

How to cite: Yue, Z., Liu, J., Yao, S., Shi, Q., Guo, R., Tian, A., and Bai, S.: The statistical research on the Kinetic- scale magnetic hole in magnetosheath, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14077, https://doi.org/10.5194/egusphere-egu21-14077, 2021.

EGU21-8905 | vPICO presentations | ST2.2 | Highlight

Helical Magnetic Cavities: Kinetic Model and Comparison with MMS Observations

Jinghuan Li, Xuzhi Zhou, Fan Yang, Anton V. Artemyev, and Qiugang Zong

Magnetic cavities are sudden depressions of magnetic field strength widely observed in the space plasma environments, which are often accompanied by plasma density and pressure enhancement. To describe these cavities, a self-consistent kinetic model has been proposed as an equilibrium solution to the Vlasov-Maxwell equations. However, observations from the Magnetospheric Multi-Scale (MMS) constellation have shown the existence of helical magnetic cavities characterized by the presence of azimuthal magnetic field, which could not be reconstructed by the aforementioned model. Here, we take into account another invariant of motion, the canonical axial momentum, to construct the particle distributions and accordingly modify the equilibrium model. The reconstructed magnetic cavity shows excellent agreement with the MMS1 observations not only in the electromagnetic field and plasma moment profiles but also in electron pitch-angle distributions. With the same set of parameters, the model also predicts signatures of the neighboring MMS3 spacecraft, matching its observations satisfactorily.

How to cite: Li, J., Zhou, X., Yang, F., Artemyev, A. V., and Zong, Q.: Helical Magnetic Cavities: Kinetic Model and Comparison with MMS Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8905, https://doi.org/10.5194/egusphere-egu21-8905, 2021.

EGU21-14044 | vPICO presentations | ST2.2

Properties of the whistler precursor upstream of the foreshock bubble shock: MMS observations

Mengmeng Wang, Terry Z. Liu, Hui Zhang, Shichen Bai, Quanqi Shi, and Xiaoqiong Zhu

Foreshock bubbles (FBs) are kinetic phenomena that can form when a rotational discontinuity or a tangential discontinuity interacts with backstreaming ions in the Earth’s foreshock region. The scale of FBs can be up to 10 RE and the expansion speeds can be more than 100 km/s. The expansion of the hot ions contributes to the formation of a new shock on the trailing edge of an FB. Using MMS data, we analyze properties of the FB shock and the whistler precursor upstream of it. For the twelve FBs we analyzed, the FB shock normal has a strong X component in GSE coordinates and the quasi-parallel FB shocks are in favor of the generation of the whistler precursor. When the Mach number is larger than 3.5, the whistler precursor disappears. The wave forms are not phase standing since the angle of the wave vector and shock normal is larger than 9 degrees. They have frequencies near fLH and right-hand polarization with respect to the ambient magnetic field (in the spacecraft frame). The properties of the whistler precursor upstream of the FB shock are similar to those at interplanetary shocks.

How to cite: Wang, M., Liu, T. Z., Zhang, H., Bai, S., Shi, Q., and Zhu, X.: Properties of the whistler precursor upstream of the foreshock bubble shock: MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14044, https://doi.org/10.5194/egusphere-egu21-14044, 2021.

EGU21-12053 | vPICO presentations | ST2.2 | Highlight

Solar wind and bow shock parameters affecting turbulence development inside the magnetosheath

Liudmila Rakhmanova, Maria Riazantseva, Georgy Zastenker, and Yuri Yermolaev

Development of the turbulent cascade inside the magnetosheath is known to be affected by the bow shock. Recently a number of studies showed various scenario of turbulent cascade modification at the bow shock including deviation from Kolmogorov scaling and additional damping of the kinetic-scale compressive fluctuations. Also, properties of probability distribution function may be modified behind the bow shock. However, factors which govern turbulence development in the magnetosheath remain unclear. Present study focuses on experimental analysis of the solar wind parameters which influence turbulence inside the magnetosheath. Analyzed data involves the combination of the solar wind parameters measured in L1 point by WIND spacecraft and Themis, Cluster and Spektr-R measurements behind the bow shock. Parameters of the frequency spectra of ion flux and/or magnetic field magnitude at frequency band from 0.01 to 2-10 Hz are considered such as slopes at magnetohydrodynamic and kinetic scales and the break frequency. Parameters of spectra are considered behind the bow shock of various topology i.e. for different mutual orientation of the interplanetary magnetic field and the local bow shock normal. Also, distance from the analyzed point to the bow shock nose is taken to the account. Obtained results point out that modification of the turbulent cascade at the bow shock is controlled not only by the bow shock topology but also by variability of the upstream solar wind plasma parameters and direction of the interplanetary magnetic field. In particular, Kolmogorov scaling often survives across the bow shock during periods of high-amplitude variations of plasma density and magnetic field magnitude in the solar wind. Also, increasing amplitude of northern interplanetary magnetic field results in steepening of spectra behind the bow shock.  

How to cite: Rakhmanova, L., Riazantseva, M., Zastenker, G., and Yermolaev, Y.: Solar wind and bow shock parameters affecting turbulence development inside the magnetosheath, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12053, https://doi.org/10.5194/egusphere-egu21-12053, 2021.

EGU21-14451 | vPICO presentations | ST2.2

Dusk side clockwise vortex generation and aurora intensity decrease after Solar Wind Dynamic Pressure Decrease

Jinyan Zhao, Quanqi Shi, Anmin Tian, Ruilong Guo, and Xiao-Chen Shen

A solar wind dynamic pressure increase/decrease leads to the compression/expansion of the Earth’s magnetosphere. In response, field-aligned currents, which are carried by precipitating or escaping plasma particles, are generated in the magnetosphere and in lead to variations in the auroral intensity. In this study, we investigate magnetospheric and ionospheric responses (including magnetospheric plasma vortex, ionospheric currents and aurorae) to a sudden decrease in solar wind dynamic pressure (SW Pdyn), which is critical for further understanding of the solar wind-magnetosphere-ionosphere coupling. We focused on a SW Pdyn decrease event that monitored by OMNI. A counter-clockwise plasma vortex was generated in the dusk side magnetosphere uncovered by using MHD simulation method and a clockwise equivalent ionospheric currents (EIC) vortex was generated in the dusk side ionosphere within about ten minutes after the pressure pulse arrival. Simultaneously, the observation results of Spherical Elementary Currents (SECs) showed that the EIC vortex region is dominated by downward field-aligned currents and the ground-based All-Sky Imager (ASI) observations in the vicinity of this EIC vortex showed that the aurorae diminished. These observations are consistent with the scenario proposed by Shi et al. (2014) that flow vortices in the magnetosphere generated by SW Pdyn sudden decrease carry downward field-aligned currents into the dusk side ionosphere, generating ionospheric current vortex and thereby modulating auroral activity on the dusk side.

How to cite: Zhao, J., Shi, Q., Tian, A., Guo, R., and Shen, X.-C.: Dusk side clockwise vortex generation and aurora intensity decrease after Solar Wind Dynamic Pressure Decrease, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14451, https://doi.org/10.5194/egusphere-egu21-14451, 2021.

EGU21-12045 | vPICO presentations | ST2.2

Dayside ionospheric electrodynamics in association with high-latitude dayside aurora (HiLDA)

Lei Cai, Anita Kullen, Tomas Karlson, Andris Vaivads, and Yongliang Zhang

The Defense Meteorological Satellite Program (DMSP) Special Sensor Ultraviolet Spectrographic Imager (SSUSI) has observed the large-scale high-latitude dayside aurora (HiLDA) during its long lifetime of hours. HiLDA has dynamical changes in form, size, location, and development of fine structures. However, the associated electrodynamics is not fully understood. In general, HiLDA occurs in the dayside polar cap during IMF By+ (By-) prevailing conditions in the sunlit northern (southern) hemisphere.  The prevailing conditions drive strong upward field-aligned current in the polar cap. Within the upward field-aligned current region, the field-aligned potential drop can be set up and accelerate the electrons, forming the monoenergetic electron precipitation (up to 10s keV) and producing HiLDA.

 

This study investigates the ionospheric flows, currents, and auroral precipitation in association with HiLDA, benified from the simultaneous measurements from the DMSP satellites, the AMPERE project, and ground-based magnetometers and SuperDARN coherent radars. We will show HiLDA interacts with duskside oval-aligned arcs or transpolar arcs. The interactions are associated with the cusp and the dayside reconnection at the duskside flank/high latitudes. The reconnection produces strong dusk-dawn convection with flow shears in the polar cap, which generates the upward Region 0 current. We find that HiLDA is formed in the high-latitude part of the upward Region 0 current. We apply the Knight relation and identify the lobe electrons (< 0.3 cm-3) as the source of HiLDA. The fine structures revealed in the emission intensity of HiLDA may suggest the uneven distribution of the electron density in the high-latitude lobe.

How to cite: Cai, L., Kullen, A., Karlson, T., Vaivads, A., and Zhang, Y.: Dayside ionospheric electrodynamics in association with high-latitude dayside aurora (HiLDA), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12045, https://doi.org/10.5194/egusphere-egu21-12045, 2021.

EGU21-13879 | vPICO presentations | ST2.2

Determining the global coherence of chorus waves in the magnetosphere

Shuai Zhang, Jonathan Rae, Clare Watt, Alexander Degeling, Anmin Tian, Quanqi Shi, and Xiao-Chen Shen

Whistler mode chorus waves play a vital role in the Earth’s outer radiation belt dynamics through the cyclotron resonant pitch angle diffusion.     Recent numerical studies have shown that the temporal and spatial variability of wave growth parameters have universal importance for the diffusion process, which should be much larger than those in the traditional averaged diffusion model.       In the present study, we analyzed both the temporal and spatial coherence of chorus wave in a statistical method using data from the EMFISIS instrument onboard the Van Allen Probes A&B from November 2012 to July 2019. In total, we find 3,875 chorus wave events to calculate the correlation of wave amplitudes between Van Allen Probes A&B.      The results show that both the spatial and temporal correlation of chorus waves decrease significantly with increasing spacecraft separation and time lag, and the spatial and temporal coherence of chorus wave only last ~433 km and ~12 s. We also find that the spatial coherence of chorus waves is higher at L>6, on the dayside, or with a lower geomagnetic index (AL*), while the temporal coherence of chorus waves does not depend on the L-shell, geomagnetic index (AL*) or magnetic local time (MLT). Our results will increase the accuracy of modeling wave-particle interactions due to chorus waves.

How to cite: Zhang, S., Rae, J., Watt, C., Degeling, A., Tian, A., Shi, Q., and Shen, X.-C.: Determining the global coherence of chorus waves in the magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13879, https://doi.org/10.5194/egusphere-egu21-13879, 2021.

EGU21-7933 | vPICO presentations | ST2.2 | Highlight

Ripples going against the flow: How energy propagation determines the global structure of magnetopause surface waves

Martin Archer, Michael Hartinger, Ferdinand Plaschke, David Southwood, and Lutz Rastaetter

Impulsive solar wind transients, such as pressure pulses and shocks, excite surface waves on the magnetopause. While much of this surface wave energy is advected downtail by the magnetosheath flow, recently it has been shown that some of these waves can be trapped locally forming a standing wave between the northern and southern ionospheres. It appears that this process can occur across most of the dayside magnetopause, however, it is not clear how these surface waves can resist the advective effect of the tailward flow. Through multispacecraft observations, global MHD simulations, and analytic MHD theory we show that azimuthally standing magnetopause surface waves are possible between 9-15h MLT. In this region, surface waves with Poynting vectors directed towards the subsolar point can exactly balance the advective effect of the magnetosheath flow, leading to no overall energy flow. Further downtail, however, the wave’s propagation cannot overcome advection and the usual tailward energy flow occurs. This trapping of magnetopause surface wave energy following the drivers of intense space weather may in turn have important implications on radiation belt, ionospheric, and auroral dynamics.

How to cite: Archer, M., Hartinger, M., Plaschke, F., Southwood, D., and Rastaetter, L.: Ripples going against the flow: How energy propagation determines the global structure of magnetopause surface waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7933, https://doi.org/10.5194/egusphere-egu21-7933, 2021.

EGU21-5122 | vPICO presentations | ST2.2

MMS Observation of Intermittent Energy Dissipation in Magnetic Reconnection Diffusion Region

Xiangcheng Dong, Malcolm Dunlop, Tieyan Wang, Jinsong Zhao, Huishan Fu, Zuzheng Chen, and Christopher Russell

Magnetospheric Multiscale (MMS) data are used to investigate the energy dissipation in a  reconnection diffusion region at the magnetopause. The four MMS spacecraft were separated by about 10 km such that comparative study between each spacecraft within the diffusion region can be implemented. Similar magnetic field and electric current behavior between each spacecraft indicates the formation of a quasi-homogeneous diffusion region structure. However, we find that the energy dissipation results between each spacecraft are different due to the temporal or spatial effect of the out-of-plane merging electric field (EM) during the dissipation region. Our study suggests that the intermittent energy dissipation in the reconnection dissipation region can be a common phenomenon, even under a stable diffusion region structure.

How to cite: Dong, X., Dunlop, M., Wang, T., Zhao, J., Fu, H., Chen, Z., and Russell, C.: MMS Observation of Intermittent Energy Dissipation in Magnetic Reconnection Diffusion Region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5122, https://doi.org/10.5194/egusphere-egu21-5122, 2021.

EGU21-1401 | vPICO presentations | ST2.2

Investigating magnetopause dynamics using global magnetosphere simulation 

Austin Brenner and Tuija Pulkkinen

Detailed 3D magnetopause surface is identified using field line and flow line tracing techniques on Space Weather Modeling Framework (SWMF) global magnetosphere simulation results. A total energy flux vector dominated by poynting flux is dotted with area element surface normals and integrated to determine energy transfer into the closed volume. Magnetopause characteristics, power and energy terms are compared with space weather indices such as Disturbance Storm-Time (Dst), Auroral Electrojet (AE), Cross Polar Cap Potential (CPCP) and emperical models such as Shue et al (1997) and Shue et al (1998) to investigate magnetopause dynamics. The storm event of Feb 18, 2014  is simulated with SWMF and analyzed. This event starts in the middle of a multi-CME impact, during a delay between the first and second CME's. While some preconditioning may have occured, it provides an excellent case for observing magnetopause variations. Results show close agreement with empirical models of integrated energy transfer through magnetopause surface. Energy accumulation inside magnetopause volume cuttoff at x=-20Re shows similar behavior to Dst.

How to cite: Brenner, A. and Pulkkinen, T.: Investigating magnetopause dynamics using global magnetosphere simulation , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1401, https://doi.org/10.5194/egusphere-egu21-1401, 2021.

EGU21-5699 | vPICO presentations | ST2.2

Interplanetary Shock-driven Magnetopause Compressions in Gorgon Global-MHD Simulations

Ravindra Desai, Jonathan Eastwood, Joseph Eggington, Mervyn Freeman, Martin Archer, Yuri Shprits, Nigel Meredith, Heli Hietala, Lars Mejnertsen, Jeremy Chittenden, and Richard Horne

Fast-forward interplanetary interplanetary shocks, as occur at the forefront of interplanetary coronal mass ejections and at corotating interaction regions, can rapidly compress the magnetopause inside the drift paths of electrons and protons, and expose geosynchonous satellites directly to the solar wind.  Here, we use Gorgon Global-MHD simulations to study the response of the magnetopause to different fast-forward interplanetary shocks, with strengths extending from the median shocks observed during solar minimum up to that representing an extreme space weather event. The subsequent magnetopause response can be characterised by three distinct phases; an initial acceleration as inertial forces are overcome, a rapid compression well-represented by a power law, and large-scale damped oscillatory motion of the order of an Earth radius, prior to reaching pressure-balance equilibrium. The subsolar magnetopause is found to oscillate with notable frequencies in the range of 2–13 mHz over several periods of diminishing amplitudes.  These results provide an explanation for similar large-scale magnetopause oscillations observed previously during the extreme events of August 1972 and March 1991 and highlight why static magnetopause models break down during periods of strong solar wind driving.

How to cite: Desai, R., Eastwood, J., Eggington, J., Freeman, M., Archer, M., Shprits, Y., Meredith, N., Hietala, H., Mejnertsen, L., Chittenden, J., and Horne, R.: Interplanetary Shock-driven Magnetopause Compressions in Gorgon Global-MHD Simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5699, https://doi.org/10.5194/egusphere-egu21-5699, 2021.

EGU21-7632 | vPICO presentations | ST2.2

The asymmetric geospace response to rapid changes in solar wind pressure

Michael Madelaire, Karl Laundal, Jone Reistad, Spencer Hatch, Anders Ohma, Stein Haaland, and Reham Elhawary

The geospace response to rapid changes in solar wind pressure results in a perturbation of the magnetospheric-ionospheric system. Ground magnetometer stations located at polar latitudes have long been known to measure a sudden impulse only minutes after a solar wind structure reaches the magnetopause.
Here a list of events associated with a step-like feature in the solar wind dynamic pressure between 1994 and 2020 is compiled based on in situ observations from ACE and Wind. Arrival time estimates are calculated using a simple propagation method and validated with a correlation analysis using SYM-H from low/mid latitude stations. A superposed epoch analysis is carried out to investigate the impact of season, interplanetary magnetic field orientation and other attributes pertaining to the interplanetary shock. All available ground magnetometer stations in SuperMAG, during each event, are used allowing for global coverage. 
Global data coverage is important for this kind of comparative analysis as it is needed to determine changes in the systems response due to e.g. season, which might lead to an improved understanding of the magnetospheric-ionospheric-thermospheric coupling.

How to cite: Madelaire, M., Laundal, K., Reistad, J., Hatch, S., Ohma, A., Haaland, S., and Elhawary, R.: The asymmetric geospace response to rapid changes in solar wind pressure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7632, https://doi.org/10.5194/egusphere-egu21-7632, 2021.

EGU21-8953 | vPICO presentations | ST2.2

Pressure Profiles in the Magnetosheath under Different Solar Wind Conditions 

Gilbert Pi, Zdeněk Němeček, and Jana Šafránková

Magnetosheath is a major interface region between the solar wind and magnetosphere. The changes of solar wind parameters after the bow shock crossing and the phenomena near the magnetopause are intensively studied. However, spatial profiles of different pressure components across the magnetosheath are not comprehensively studied yet, especially in observations. The highly fluctuating sheath, variations of upstream conditions, and permanent motion of the magnetopause and bow shock complicate observational studies. In the present contribution, we use two different methods to obtain a typical magnetosheath profile under specific upstream conditions. One is the superposed epoch analysis of complete crossing events observed by the THEMIS mission. The second method is relocated the THEMIS observations into a normalized magnetosheath coordinate. By contrast to the result of MHD modeling, we found only a very weak difference between pressure profiles for southward and northward IMF. Our results show that the thermal pressure exhibits a peak near the magnetopause that is more pronounced under southward than under northward IMF. The magnetic pressures have a similar trend for both IMF polarities but the magnetic pressure increases faster toward the magnetopause for northward IMF than it does for southward IMF.

How to cite: Pi, G., Němeček, Z., and Šafránková, J.: Pressure Profiles in the Magnetosheath under Different Solar Wind Conditions , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8953, https://doi.org/10.5194/egusphere-egu21-8953, 2021.

The boundary between the solar wind (SW) and the Earth’s magnetosphere, named the magnetopause (MP), is highly dynamic. Its location and shape can vary as a function of different SW parameters such as density, velocity, and interplanetary magnetic field (IMF) orientations. We employ a 3D kinetic Particle-In-Cell (IAPIC) code to simulate these effects.  We investigate the impact of radial (B = Bx) and quasi-radial (Bz < Bx, By) IMF on the shape and size of Earth’s MP for a dipole tilt of 31o using both maximum density steepening and pressure system balance methods for identifying the boundary. We find that, compared with northward or southward-dominant IMF conditions, the MP position expands asymmetrically by 8 to 22% under radial IMF. In addition, we construct the MP shape along the tilted magnetic equator and the OX axes showing that the expansion is asymmetric, not global, stronger on the MP flanks, and is sensitive to the ambient IMF. Finally, we investigate the contribution of SW backstreaming ions by the bow shock to the MP expansion, the temperature anisotropy in the magnetosheath, and a strong dawn-dusk asymmetry in MP location.

How to cite: Baraka, S., Le Contel, O., Ben-Jaffel, L., and Moore, B.: How radial and quasi radial IMF impact the Earth's magnetopause's size, location, and shape. Does this impact generate Dawn-Dusk asymmetry in the magnetosheath?: Global 3D Kinetic Simulations. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9675, https://doi.org/10.5194/egusphere-egu21-9675, 2021.

EGU21-8153 | vPICO presentations | ST2.2 | Highlight

Global 6-dimensional hybrid-Vlasov modelling of the magnetosphere: First Vlasiator results

Minna Palmroth, Urs Ganse, Markus Battarbee, Lucile Turc, Yann Pfau-Kempf, Maarja Bussov, Maxime Grandin, Andreas Johlander, Jonas Suni, Maxime Dubart, Kostis Papadakis, and Markku Alho

Numerical simulations are key in modern space physics, as they can be used as 1) context to data, 2) predict future behaviour of the system, 3) understand the system using unforeseen boundary conditions, and increasingly also in 4) discovering new phenomena that are hard to be observed using point-wise satellite measurements. Especially, the discovery of new phenomena pertains to global systems, where phenomena of interest may be initiated far away from the point of observations. The most typical method of simulating the global solar wind - magnetosphere - ionosphere system is based on magnetohydrodynamics (MHD), which is however not representing the actual plasma behaviour in locations where kinetic physics becomes important. Such regions are e.g., the foreshock - magnetosheath interaction, reconnection, and the inner magnetosphere.

Vlasiator is the world’s first and so far the only global simulation based on the hybrid-Vlasov approach that simulates the ion distributions accurately without noise. The simulation has, for computational reasons, been so far executed in 2D real space. Even so, the global 5D Vlasiator results have shown without a doubt that ion-kinetic effects cannot be neglected from the large scales, as small-scale phenomena affect large scales and vice versa. This scale coupling leads to phenomena that are not predicted using local simulations without proper boundary conditions, or with spacecraft measurements lacking the global context.

Here, we present the world’s first global 6-dimensional ion-kinetic global magnetospheric simulation run, accurate both locally and globally. The simulation box extends from the dayside to the nightside, and includes global dynamics and both dayside and nightside reconnection regions. We will investigate unambiguously for the first time the dayside magnetopause reconnection as driven by the kinetic variations in the magnetosheath, and tail reconnection as driven by magnetic flux from the dayside.

How to cite: Palmroth, M., Ganse, U., Battarbee, M., Turc, L., Pfau-Kempf, Y., Bussov, M., Grandin, M., Johlander, A., Suni, J., Dubart, M., Papadakis, K., and Alho, M.: Global 6-dimensional hybrid-Vlasov modelling of the magnetosphere: First Vlasiator results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8153, https://doi.org/10.5194/egusphere-egu21-8153, 2021.

EGU21-9370 | vPICO presentations | ST2.2

Subgrid modelling of ion pitch-angle scattering for magnetosheath waves in a global hybrid-Vlasov simulation

Maxime Dubart, Urs Ganse, Adnane Osmane, Andreas Johlander, Markus Battarbee, Markku Alho, Maarja Bussov, Harriet George, Maxime Grandin, Kostis Papadakis, Yann Pfau-Kempf, Jonas Suni, Lucile Turc, and Minna Palmroth

Numerical simulations are widely used in modern space physics and are an essential tool to understand or discover new phenomena which cannot be observed using spacecraft measurements. However, numerical simulations are limited by the space grid resolution of the system and the computational costs of having a high spatial resolution. Therefore, some physics may be unresolved in part of the system due to its low spatial resolution. We have previously identified, using Vlasiator, that the proton cyclotron instability is not resolved for grid cell sizes larger than four times the inertial length in the solar wind, for waves in the downstream of the quasi-perpendicular shock in the magnetosheath of a global hybrid-Vlasov simulation. This leads to unphysically high perpendicular temperature and a dominance of the mirror mode waves. In this study, we use high-resolution simulations to measure and quantify how the proton cyclotron instability diffuses and isotropizes the velocity distribution functions. We investigate the process of pitch-angle scattering during the development of the instability and propose a method for the sub-grid modelling of the diffusion process of the instability at low resolution. This allows us to model the isotropization of the velocity distribution functions and to reduce the temperature anisotropy in the plasma while saving computational resources.

How to cite: Dubart, M., Ganse, U., Osmane, A., Johlander, A., Battarbee, M., Alho, M., Bussov, M., George, H., Grandin, M., Papadakis, K., Pfau-Kempf, Y., Suni, J., Turc, L., and Palmroth, M.: Subgrid modelling of ion pitch-angle scattering for magnetosheath waves in a global hybrid-Vlasov simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9370, https://doi.org/10.5194/egusphere-egu21-9370, 2021.

EGU21-10638 | vPICO presentations | ST2.2 | Highlight

A Global Survey of Geospace Electrons with eVlasiator: First Results

Markku Alho, Markus Battarbee, Yann Pfau-Kempf, Urs Ganse, Lucile Turc, Andreas Johlander, Vertti Tarvus, Hongyang Zhou, Maxime Dubart, Maxime Grandin, Konstantinos Papadakis, Jonas Suni, Harriet George, Maarja Bussov, and Minna Palmroth

Models of the geospace plasma environment have been proceeding towards more realistic descriptions of the solar wind—magnetosphere interaction, from gas-dynamic to MHD and hybrid ion-kinetic models such as the state-of-the-art Vlasiator model. Advances in computational capabilities have enabled global simulations of detailed physics, but the electron scale has so far been out of reach in a truly global setting. 

In this work we present results from eVlasiator, an offshoot of the Vlasiator model, showing first results from a global 2D+3V kinetic electron geospace simulation. Despite truncation of some electron physics and use of ion-scale spatial resolution, we show that realistic electron distribution functions are obtainable within the magnetosphere and describe these in relation to MMS observations. Electron precipitation to the upper atmosphere from these velocity distributions is estimated.

How to cite: Alho, M., Battarbee, M., Pfau-Kempf, Y., Ganse, U., Turc, L., Johlander, A., Tarvus, V., Zhou, H., Dubart, M., Grandin, M., Papadakis, K., Suni, J., George, H., Bussov, M., and Palmroth, M.: A Global Survey of Geospace Electrons with eVlasiator: First Results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10638, https://doi.org/10.5194/egusphere-egu21-10638, 2021.

EGU21-3230 | vPICO presentations | ST2.2 | Highlight

Imaging solar-terrestrial interactions on the global scale: The SMILE mission

Graziella Branduardi-Raymont, Chi Wang, C. Philippe Escoubet, Steve Sembay, Eric Donovan, Lei Dai, Lei Li, Jing Li, David Agnolon, Walfried Raab, Colin Forsyth, Andy Read, Emma L. Spanswick, Jenny A. Carter, Hyunju Connor, Tianran Sun, Andrey Samsonov, and David G. Sibeck

A key link in the Sun – Earth connection is the solar wind coupling with the terrestrial magnetosphere. Mass and energy enter geospace via dayside magnetic reconnection; reconnection in the tail leads to release of energy and particle injection deep into the magnetosphere, causing geomagnetic substorms. The end product of these processes is the visual manifestation of variable auroral emissions. These have been observed both from the ground and from space, the latter for relatively short continuous periods of time. In situ measurements by a fleet of solar wind and magnetospheric missions, current and planned, can provide the most detailed observations of the plasma conditions both in the incoming solar wind and magnetospheric plasma. However, we are still unable to quantify the global effects of the drivers of Sun - Earth connections, and to monitor their evolution with time. This information is the key missing link for developing a comprehensive understanding of how the Sun gives rise to and controls the Earth's plasma environment and space weather. We are now able to take a novel approach to global monitoring of geospace: X-ray imaging of the magnetosheath and cusps is made possible by the X-ray emission produced in the process of solar wind charge exchange, first observed at comets, and subsequently found to occur in the vicinity of solar system planets, including the Earth's magnetosphere. This is where SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) comes in.

SMILE is a novel self-standing mission dedicated to observing the solar wind – magnetosphere coupling at Earth via simultaneous X-ray imaging of the magnetosheath and polar cusps (large spatial scales at the magnetopause), UV imaging of global auroral distributions (mesoscale structures in the ionosphere) and in situ solar wind/magnetosheath plasma and magnetic field measurements. SMILE will provide scientific data on solar wind – magnetosphere interaction at the global level while monitoring it continuously for long, uninterrupted periods of time from a highly elliptical northern polar orbit.

SMILE is a collaborative mission between ESA and the Chinese Academy of Sciences that was selected in Nov. 2015, adopted into ESA’s Cosmic Vision Programme in March 2019, and is due for launch at the end of 2024. The novel science that SMILE will deliver, the ongoing technical developments and scientific preparations, and the current status of the mission, will be presented.

How to cite: Branduardi-Raymont, G., Wang, C., Escoubet, C. P., Sembay, S., Donovan, E., Dai, L., Li, L., Li, J., Agnolon, D., Raab, W., Forsyth, C., Read, A., Spanswick, E. L., Carter, J. A., Connor, H., Sun, T., Samsonov, A., and Sibeck, D. G.: Imaging solar-terrestrial interactions on the global scale: The SMILE mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3230, https://doi.org/10.5194/egusphere-egu21-3230, 2021.

EGU21-2860 | vPICO presentations | ST2.2 | Highlight

Prediction and understanding of soft proton contamination in XMM-Newton: a machine learning approach

Elena Kronberg, Fabio Gastaldello, Stein Haaland, Artem Smirnov, Max Berrendorf, Simona Ghizzardi, Kip Kuntz, Nithin Sivadas, Robert Allen, Andrea Tiengo, Raluca llie, Yu Huang, and Lynn Kistler

One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes flying mainly in the magnetosphere are soft protons with few tens to hundreds of keV concentrated. One such telescope is the X-ray Multi-Mirror Mission (XMM-Newton) by ESA. Its observing time lost due to the contamination is  about 40%. This affects all the major broad science goals of XMM, ranging from cosmology to astrophysics of neutron stars and black holes. The soft proton background could dramatically impact future X-ray missions such Athena and SMILE missions. Magnetopsheric processes that trigger this background are still poorly understood. We use a machine learning approach to delineate related important parameters and to develop a model to predict the background contamination using 12 years of XMM observations. As predictors we use the location of XMM, solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in southern direction, ZGSE, (XMM observations were in the southern hemisphere), the solar wind velocity and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the best two individual predictors and a machine learning model which utilizes an ensemble of the predictors (Extra Trees Regressor) and gives better performance. Based on our analysis, future X-Ray missions in the magnetosphere should minimize observations during  times  associated with high solar wind speed  and avoid closed magnetic field lines, especially at the dusk flank region at least in the southern hemisphere. 

How to cite: Kronberg, E., Gastaldello, F., Haaland, S., Smirnov, A., Berrendorf, M., Ghizzardi, S., Kuntz, K., Sivadas, N., Allen, R., Tiengo, A., llie, R., Huang, Y., and Kistler, L.: Prediction and understanding of soft proton contamination in XMM-Newton: a machine learning approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2860, https://doi.org/10.5194/egusphere-egu21-2860, 2021.

EGU21-8329 | vPICO presentations | ST2.2

MHD simulations of magnetospheric response to a strong solar wind density pulse

Andrey Samsonov, Jennifer A. Carter, Graziella Branduardi-Raymont, and Steven Sembay

On 16-17 June 2012, an interplanetary coronal mass ejection with an extremely high solar wind density (~100 cm-3) and mostly strong northward (or eastward) interplanetary magnetic field (IMF) interacted with the Earth’s magnetosphere. We have simulated this event using global MHD models. We study the magnetospheric response to two solar wind discontinuities. The first is characterized by a fast drop of the solar wind dynamic pressure resulting in rapid magnetospheric expansion. The second is a northward IMF turning which causes reconfiguration of the magnetospheric-ionospheric currents. We discuss variations of the magnetopause position and locations of the magnetopause reconnection in response to the solar wind variations. In the second part of our presentation, we present simulation results for the forthcoming SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) mission. SMILE is scheduled for launch in 2024. We produce two-dimensional images that derive from the MHD results of the expected X-ray emission as observed by the SMILE Soft X-ray Imager (SXI). We discuss how SMILE observations may help to study events like the one presented in this work.

How to cite: Samsonov, A., Carter, J. A., Branduardi-Raymont, G., and Sembay, S.: MHD simulations of magnetospheric response to a strong solar wind density pulse, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8329, https://doi.org/10.5194/egusphere-egu21-8329, 2021.

EGU21-15314 | vPICO presentations | ST2.2

Identifying the plasmapause location from global auroral image data

Michaela Mooney, Colin Forsyth, Mike Marsh, and Jonathan Rae

Identifying the plasmapause location is crucial for forecasting and modelling the radiation belts, as well as larger scale models of the magnetosphere. The ionospheric footpoints of the plasmapause are thought to map to the equatorward edge of the diffuse aurora, with the first direct observation of an undulation of the plasmapause boundary and corresponding auroral features reported by He et al. (2020). Despite the importance of the plasmapause location, we do not have global observations of the plasmapause location.

We provide a new statistical model of the plasmapause location determined from mapping the equatorward boundary of the observed auroral oval out to the inner magnetosphere. The model uses the equatorward boundary of the auroral oval determined from far-ultraviolet observations from the IMAGE spacecraft from Longden et al. (2010) to provide a statistical estimate of the plasmapause location for different levels of geomagnetic activity. Comparing the results of the statistical plasmapause model to other more direct measurements of the plasmapause shows a good agreement in the nightside local time sectors. 

The results of this analysis show that the equatorward boundary of the auroral oval statistically maps closely to the plasmapause boundary the nightside sectors and provides an alternative use for global auroral image data from the upcoming SMILE mission. 

How to cite: Mooney, M., Forsyth, C., Marsh, M., and Rae, J.: Identifying the plasmapause location from global auroral image data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15314, https://doi.org/10.5194/egusphere-egu21-15314, 2021.

EGU21-9070 | vPICO presentations | ST2.2 | Highlight

Dual-lobe reconnection and horse-collar auroras

Steve Milan, Jenny Carter, Gemma Bower, Suzie Imber, Larry Paxton, Brian Anderson, Marc Hairston, and Benoit Hubert

We propose a mechanism for the formation of the horse-collar auroral configuration common during periods of strongly northwards interplanetary magnetic field, invoking the action of dual-lobe reconnection (DLR).  Auroral observations are provided by the Imager for Magnetopause-to-Auroras Global Exploration (IMAGE) satellite and spacecraft of the Defense Meteorological Satellite Program (DMSP).  We also use ionospheric flow measurements from DMSP and polar maps of field-aligned currents (FACs) derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE).  Sunward convection is observed within the dark polar cap, with antisunwards flows within the horse-collar auroral region, together with the NBZ FAC distribution expected to be associated with DLR.  We suggest that newly-closed flux is transported antisunwards and to dawn and dusk within the reverse lobe cell convection pattern associated with DLR, causing the polar cap to acquire a teardrop shape and weak auroras to form at high latitudes.  Horse-collar auroras are a common feature of the quiet magnetosphere, and this model provides a first understanding of their formation, resolving several outstanding questions regarding the nature of DLR and the magnetospheric structure and dynamics during northwards IMF.  The model can also provide insights into the trapping of solar wind plasma by the magnetosphere and the formation of a low-latitude boundary layer and cold, dense plasma sheet.  We speculate that prolonged DLR could lead to a fully closed magnetosphere, with the formation of horse-collar auroras being an intermediate step.

How to cite: Milan, S., Carter, J., Bower, G., Imber, S., Paxton, L., Anderson, B., Hairston, M., and Hubert, B.: Dual-lobe reconnection and horse-collar auroras, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9070, https://doi.org/10.5194/egusphere-egu21-9070, 2021.

EGU21-10704 | vPICO presentations | ST2.2

Quantifying the lobe reconnection rate during dominant IMF By periods

Jone Peter Reistad, Karl Magnus Laundal, Anders Ohma, Nikolai Østgaard, Spencer Hatch, Stein Haaland, and Evan Thomas

Lobe reconnection is usually considered to play an important role in geospace dynamics only when the Interplanetary Magnetic Field (IMF) is mainly northward. This is because the most common signature of lobe reconnection is the strong sunward convection in the polar cap ionosphere observed during these conditions. During more typical conditions, when the IMF is mainly in a dawn-dusk direction, plasma flows initiated by dayside as well as lobe reconnection map to high latitude ionospheric locations in close proximity to each other. This has been emphasized in the literature earlier, mainly on a conceptual level, but quantifying the relative importance of lobe reconnection to the observed ionospheric convection is highly challenging during these IMF By dominated conditions, since one has to identify and distinguish these regions. By normalizing the ionospheric convection (observed by SuperDARN) to the polar cap boundary (inferred from simultaneous AMPERE observations), we are able to do this separation, allowing us to quantify the relative contribution of both lobe reconnection and dayside/nightisde reconnection to the ionospheric convection pattern. Using this segmentation technique we can get new quantitative insights into the importance of the various mechanisms that affect the lobe reconnection rate. In this presentation we will describe the technique and show results of analysis of periods when the IMF is mainly in the dawn-dusk direction. Our quantification of the average lobe reconnection rate during various conditions yields quantitative knowledge of the importance of the lobe reconnection process, which can act independently in the two hemispheres. We will specifically constrain the influence from parameters such as the dipole tilt angle and the product of IMF transverse component and solar wind velocity.

How to cite: Reistad, J. P., Laundal, K. M., Ohma, A., Østgaard, N., Hatch, S., Haaland, S., and Thomas, E.: Quantifying the lobe reconnection rate during dominant IMF By periods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10704, https://doi.org/10.5194/egusphere-egu21-10704, 2021.

EGU21-13768 | vPICO presentations | ST2.2

Formation and decay of a transpolar arc during a major magnetic storm onset

Tuija Pulkkinen, Shannon Hill, Qusai Al Shidi, Austin Brenner, and Shasha Zou

EGU21-7493 | vPICO presentations | ST2.2

Electrodynamics surrounding polar cap auroral arcs

Amalie Ø. Hovland, Kjellmar Oksavik, Jone P. Reistad, and Marc R. Hairston

This multi-instrument case study investigates the electrodynamics surrounding polar cap auroral arcs. A long-lasting auroral arc is observed in the high latitude dusk-sector at ~80° Apex latitude in the northern hemisphere. Ion drift measurements from the SSIES system on the DMSP spacecraft have been combined with multiple ground-based observations. Line of sight velocity data from three polar latitude high-frequency Super Dual Auroral Radar Network (SuperDARN) radars show mesoscale structure in the ionospheric convection in the region surrounding the arc. The convection electric field in this region is modelled using a Spherical Elementary Convection Systems (SECS) technique, using curl-free basis functions only. The result is a regional model of the ionospheric convection based on the fairly dense and distributed flow observations and the curl-free constraint. The model is compared to optical data of the auroral arc from two high latitude Redline Emission Geospace Observatory (REGO) all-sky imagers as well as UV images and particle measurements from the DMSP spacecraft to describe the local electrodynamics in the vicinity of the high latitude arc throughout the event.

How to cite: Hovland, A. Ø., Oksavik, K., Reistad, J. P., and Hairston, M. R.: Electrodynamics surrounding polar cap auroral arcs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7493, https://doi.org/10.5194/egusphere-egu21-7493, 2021.

EGU21-9117 | vPICO presentations | ST2.2

Substorm evolution of the auroral zone boundaries on the dawn and dusk flanks: DMSP and POES/MetOp observations

Margot Decotte, Karl M. Laundal, Spencer Hatch, and Jone Reistad

We present a method for tracking the evolution of the auroral boundaries on the dawn and dusk flanks during magnetospheric substorms by using a combined database of auroral zone boundaries derived from DMSP and POES/MetOp satellite particle measurements. Auroral boundaries can be identified by the Kilcommons et al. (2017) algorithm which use electron energy fluxes from the DMSP spectrometer (SSJ instrument). We show how auroral boundaries may also be obtained from precipitating electron observations from the POES/MetOp Total Energy Detector (TED) instrument by subjecting the TED electron measurements to an algorithm similar to that presented by Kilcommons et al. (2017). Boundaries derived from the two satellite missions are similar, suggesting that the technique for auroral oval boundary identification is physically meaningful.

How to cite: Decotte, M., Laundal, K. M., Hatch, S., and Reistad, J.: Substorm evolution of the auroral zone boundaries on the dawn and dusk flanks: DMSP and POES/MetOp observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9117, https://doi.org/10.5194/egusphere-egu21-9117, 2021.

EGU21-11400 | vPICO presentations | ST2.2

Empirical relationship between nightside reconnection rate and solar wind / geomagnetic measurements

Andreas Lysaker Kvernhaug, Karl M. Laundal, and Jone P. Reistad

According to the expanding-contracting polar cap paradigm, dayside and nightside reconnection control magnetosphere-ionosphere dynamics at high latitudes by increasing or decreasing the open flux respectively. The dayside reconnection rate can be estimated using parameters measured in the solar wind, but there is no reliable and available proxy for the nightside reconnection rate. We want to remedy this by using AMPERE to estimate a time series of open flux content. The AMPERE data set originates from the global Iridium satellite system, enabling continuous measurements of the field-aligned Birkeland currents, from which the open magnetic flux of the polar caps can be derived. These estimates will be used to derive empirical relationships with available measurements on the ground and in the solar wind. This work can also help improve estimates of dayside reconnection rates.

How to cite: Kvernhaug, A. L., Laundal, K. M., and Reistad, J. P.: Empirical relationship between nightside reconnection rate and solar wind / geomagnetic measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11400, https://doi.org/10.5194/egusphere-egu21-11400, 2021.

EGU21-3372 | vPICO presentations | ST2.2 | Highlight

Parameters controlling the substorm onset location

Reham Elhawary, Karl Laundal, Jone Reistad, Anders Ohma, Spencer Hatch, and Michael Madelaire

Substorm onset location varies over a range of magnetic local time (MLT) and magnetic latitudes (MLat). It is well known that about 5% of the variation in onset MLT can be explained by variations in interplanetary magnetic field orientation and dipole tilt angle. Both parameters introduce an azimuthal component in the magnetic field in the magnetosphere such that the projection of the onset MLT in the ionosphere is shifted. The MLT of the onset near the magnetopsheric equatorial plane is even less predictable. Recent studies have suggested that gradients in the ionospheric Hall conductance lead to a duskward shift of tail dynamics, which could also influence the location of substorm onset. Our goal is to test these ideas by quantifying the dependence of the spatial variation of the onset location on external and internal conditions. We focus on the correlation between the substorm onset location with conditions prior to the onset, such as the interplanetary magnetic field By component, dipole tilt angle, and estimates of the Hall conductance. Linear regression analysis is used to determine the substorm onset location dependence on the proposed variables.

How to cite: Elhawary, R., Laundal, K., Reistad, J., Ohma, A., Hatch, S., and Madelaire, M.: Parameters controlling the substorm onset location, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3372, https://doi.org/10.5194/egusphere-egu21-3372, 2021.

EGU21-10541 | vPICO presentations | ST2.2

Spatial variation of the kappa index in the Earth’s plasma sheet: RCMI results

Sina Sadeghzadeh, Jian Yang, and Ameneh Mousavi

Astrophysical plasmas are collisionless and correlated systems in which particles are out of thermal equilibrium and can be characterized by non-Maxwellian distribution functions. Amongst those nonthermal distribution functions, the kappa distribution has been widely used and satisfactorily modeled numerous space plasma environments such as ring current and plasma sheet. The particles spectra observed by detector measurements onboard the satellites (e.g., Time History of Events and Macroscale Interactions during Substorms (THEMIS)) indicate that the energy fluxes of plasma sheet particles can be fitted well by the kappa distribution (or combinations thereof). Besides, many empirical models have also used such distributions to estimate fluxes at different energies. Statistically, in the RCM simulations, at all times, even geomagnetically quiet conditions, the initial plasma distribution is assumed to be a kappa function with κ≈6. However, based on the flux spectra constructed by THEMIS data, the kappa index has a significant dawn-dusk asymmetry and a clear dependency on the geocentric distance (R) and the magnetic local time (MLT). Using the averaged RCMI calculated energy fluxes in the equatorial plane we intend to analyze the spatial distribution of the spectral index both for ions (κi) and electrons (κe) in this region and compare the simulation results with observations.

How to cite: Sadeghzadeh, S., Yang, J., and Mousavi, A.: Spatial variation of the kappa index in the Earth’s plasma sheet: RCMI results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10541, https://doi.org/10.5194/egusphere-egu21-10541, 2021.

EGU21-14489 | vPICO presentations | ST2.2

Turbulent Plasma Jet Fronts and Related Ion Acceleration

Louis Richard, Yuri Khotyaintsev, Daniel Graham, Olivier Le Contel, Ian Cohen, Drew Turner, Barbara Giles, Per-Arne Lindqvist, and Christopher Russell

We investigate an earthward bursty bulk flow (BBF) observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth’s magnetotail (XGSM ~ -23.88 RE, YGSM ~ 6.72 RE, ZGSM ~ 4.06 RE). At  the leading edge of the BBF we observe a complex magnetic field structure. In particular, within this region we identify multiple dipolarization fronts (DFs) and large amplitude oscillations of the magnetic field BX, which correspond to a long wavelength current sheet flapping motion. Within the DFs, we observe increased fluxes of energetic ions and electrons. We investigate the trapping of the ions between two consecutive DFs. We discuss the ion acceleration mechanism and the adiabaticity of the ion energisation process.

How to cite: Richard, L., Khotyaintsev, Y., Graham, D., Le Contel, O., Cohen, I., Turner, D., Giles, B., Lindqvist, P.-A., and Russell, C.: Turbulent Plasma Jet Fronts and Related Ion Acceleration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14489, https://doi.org/10.5194/egusphere-egu21-14489, 2021.

EGU21-13957 | vPICO presentations | ST2.2

Photoelectron transport and associated Far Ultraviolet emissions: Model simulation and comparison with observations

Jun Liang, Dmytro Sydorenko, Eric Donovan, and Robert Rankin

Photoelectrons are produced by solar Extreme Ultraviolet radiation and contribute significantly to the ionization and heat balances in planetary upper atmospheres. They are also the source of dayglow emissions, whose intensities may become comparable to weak or moderate dayside auroras. Proper modeling of photoelectrons and dayglow components is desirable for global auroral imaging, one of the core objectives of the SMILE mission. In many previous studies and model simulations, the transport effects of photoelectrons are neglected, so that the photoelectron distribution is controlled by a balance between local production and energy degradation. However, photoelectrons, when generated, can move along the magnetic field line. In particular, some of the photoelectrons may precipitate into the conjugate dark hemisphere and induce auroral-like emissions there, which was reported in realistic observations [Kil et al., 2020]. As a part of the SMILE Ultraviolet imager (UVI) model platform, we have recently developed an auroral/dayglow model that takes into account the interhemispheric transport of photoelectrons and/or secondary electrons, as well as their interaction with the ionosphere/thermosphere. In this study, we report the model simulation of the photoelectron generation and transport, and their induced UV emissions in both the dayside and nightside atmosphere. The simulation results are found to be in reasonable agreement with the realistic SSUSI/GUVI observations.

How to cite: Liang, J., Sydorenko, D., Donovan, E., and Rankin, R.: Photoelectron transport and associated Far Ultraviolet emissions: Model simulation and comparison with observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13957, https://doi.org/10.5194/egusphere-egu21-13957, 2021.

EGU21-7607 | vPICO presentations | ST2.2

Electrojet poleward boundary variations with IMF By and season

Simon Walker, Margot Decotte, Karl Laundal, Jone Reistad, Anders Ohma, and Spencer Hatch

By utilising measurements from twenty ground magnetometer stations in Fennoscandia, divergence-free ionospheric currents above this region are modelled using spherical elementary currents (SECS). New modelling techniques are implemented that coerce the model to find a solution that resembles the resolvable ionospheric currents. The divergence-free currents are evaluated along the 105o magnetic meridian covering a period of almost 20 years with a resolution of 1 minute, as a result of the magnetometers chosen. From these sheet current density latitude profiles, the boundaries of the auroral electrojet are identified. After performing a large statistical analysis it is found that there is a significant IMF By effect on the poleward boundary of the electrojets during the Summer but not during the Winter. We suggest that this seasonal effect can be attributed to the effects of lobe reconnection on the extent of currents in the auroral electrojets. Further work is done to compare the SECS derived electrojet boundaries with particle precipitation data from low orbit satellites.

How to cite: Walker, S., Decotte, M., Laundal, K., Reistad, J., Ohma, A., and Hatch, S.: Electrojet poleward boundary variations with IMF By and season, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7607, https://doi.org/10.5194/egusphere-egu21-7607, 2021.

EGU21-5298 | vPICO presentations | ST2.2

Intense dB/dt variations driven by near-Earth Bursty Bulk Flows (BBFs): A case study

Dong Wei, Malcolm Dunlop, Junying Yang, Xiangcheng Dong, Yiqun Yu, and Tieyan Wang

During geomagnetically disturbed times the surface geomagnetic field often changes abruptly, producing geomagnetically induced currents (GICs) in a number of ground based systems. There are, however, few studies reporting GIC effects which are driven directly by bursty bulk flows (BBFs) in the inner magnetosphere. In this study, we investigate the characteristics and responses of the magnetosphere-ionosphere-ground system during the 7 January 2015 storm by using a multi-point approach which combines space-borne measurements and ground magnetic observations. During the event, multiple BBFs are detected in the inner magnetosphere while the magnetic footprints of both magnetospheric and ionospheric satellites map to the same conjugate region surrounded by a group of magnetometer ground stations. It is suggested that the observed, localized substorm currents are caused by the observed magnetospheric BBFs, giving rise to intense geomagnetic perturbations. Our results provide direct evidence that the wide-range of intense dB/dt (and dH/dt) variations are associated with a large-scale, substorm current system, driven by multiple BBFs.

How to cite: Wei, D., Dunlop, M., Yang, J., Dong, X., Yu, Y., and Wang, T.: Intense dB/dt variations driven by near-Earth Bursty Bulk Flows (BBFs): A case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5298, https://doi.org/10.5194/egusphere-egu21-5298, 2021.

ST2.4 – Wave-particle interactions in the Earth's inner magnetosphere, radiation belt dynamics, ionospheric plasma sources, and coupling

EGU21-2042 | vPICO presentations | ST2.4 | Highlight

The Magnetospheric “Zebra Stripes”: A Tracer of Near-Earth Space Dynamics

Solène Lejosne and Forrest S. Mozer

High-energy resolution measurements of energetic (tens to hundreds of keV) electron fluxes in the Earth’s inner radiation belt and slot region (below L~ 3) revealed the presence of drift-periodic structures named the “zebra stripes”.

We show that analyzing the characteristics of the zebra stripes provides a new tool to shed light on important, yet mostly uncharted drivers of the Earth’s inner magnetosphere, namely, (a) radial displacements of geomagnetically trapped particles in the inner belt and slot region, and (b) electric field variations in the subauroral region.

With the large database of high-quality observations provided by the NASA Van Allen Probes mission, it is for the first time possible to perform long-term statistical analysis of the zebra stripe pattern.

Because Earth-like zebra stripes were also recently discovered at Saturn, the analysis of the zebra stripes present at Earth could constitute a benchmark to determine the electric fields and associated radiation belt dynamics at other magnetized planets.

How to cite: Lejosne, S. and Mozer, F. S.: The Magnetospheric “Zebra Stripes”: A Tracer of Near-Earth Space Dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2042, https://doi.org/10.5194/egusphere-egu21-2042, 2021.

EGU21-15124 | vPICO presentations | ST2.4

On the origin of Ultra-Low Frequency (ULF) waves in sudden and quasiperiodic solar wind dynamic pressure variations penetrating into Earth’s magnetosphere

Marina Georgiou, Christos Katsavrias, Ioannis Daglis, Georgios Balasis, and Alexander Hillaris

Several observational studies have shown that external (i.e. solar wind and magnetosheath) dynamic pressure variations can drive quasi-periodic perturbations of the geomagnetic field. In this study, we utilise multi-spacecraft (ARTEMIS, Cluster, GOES, and THEMIS) mission measurements and investigate step-like increases and quasi-periodic variations of solar wind dynamic pressure as the source mechanism of geomagnetic pulsations with frequencies between ~0.5 to 15 mHz. During intervals of slow solar wind and low geomagnetic activity — to exclude waves generated by velocity shear at the magnetopause and substorm contributions — common periodicities in electromagnetic field oscillations inside the magnetosphere and the solar wind driver are detected in Lomb-Scargle periodograms. The causal relationship is examined in frequency and polarisation signatures of waves detected at the various probes using continuous wavelet transform, cross-wavelet spectra and wavelet transform coherence. The observed dependence of wave properties on their localisation offers excellent source verification for ULF Pc4-5  waves originating in dynamic pressure variations in the upstream solar wind and propagating in the dayside magnetosphere through the field line resonance process.

This research is co-financed by Greece and the European Union (European Social Fund - ESF) through the Operational Programme “Human Resources Development, Education and Lifelong Learning 2014-2020” in the context of the project ULFpulse (MIS: 5048130).

How to cite: Georgiou, M., Katsavrias, C., Daglis, I., Balasis, G., and Hillaris, A.: On the origin of Ultra-Low Frequency (ULF) waves in sudden and quasiperiodic solar wind dynamic pressure variations penetrating into Earth’s magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15124, https://doi.org/10.5194/egusphere-egu21-15124, 2021.

EGU21-15528 | vPICO presentations | ST2.4

The magnetospheric interactions of predicted ULF wave power

Sarah Bentley, Rhys Thompson, Clare Watt, Jennifer Stout, and Teo Bloch

We present and analyse a freely-available model of the power found in ultra-low frequency waves (ULF, 1-15 mHz) throughout Earth’s magnetosphere. Predictions can be used to test our understanding of magnetospheric dynamics, while accurate models of these waves are required to characterise the energisation and transport of radiation belt electrons in space weather.

This model is constructed using decision tree ensembles, which iteratively partition the given parameter space into variable size bins. Wave power is determined by physical driving parameters (e.g. solar wind properties) and spatial parameters of interest (magnetic local time MLT, magnetic latitude and frequency). As a parameterised model, there is no guarantee that individual physical processes can be extracted and analysed. However, by iteratively considering smaller scale driving processes, we identify predominant wave drivers and find that solar wind driving of ULF waves are moderated by internal magnetospheric conditions. Significant remaining uncertainty occurs with mild solar wind driving, suggesting that the internal state of the magnetosphere should be included in future.

Models such as this may be used to create global magnetospheric “maps” of predicted wave power which may then be used to create radial diffusion coefficients determining the effect of ULF waves on radiation belt electrons.

How to cite: Bentley, S., Thompson, R., Watt, C., Stout, J., and Bloch, T.: The magnetospheric interactions of predicted ULF wave power, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15528, https://doi.org/10.5194/egusphere-egu21-15528, 2021.

EGU21-5977 | vPICO presentations | ST2.4

On the effect of ULF waves on the outer radiation belt during geomagnetic storms

Christopher Lara, Pablo S. Moya, Victor Pinto, Javier Silva, and Beatriz Zenteno

The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.

How to cite: Lara, C., Moya, P. S., Pinto, V., Silva, J., and Zenteno, B.: On the effect of ULF waves on the outer radiation belt during geomagnetic storms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5977, https://doi.org/10.5194/egusphere-egu21-5977, 2021.

EGU21-11203 | vPICO presentations | ST2.4

ULF Wave Power During Geomagnetic Storms and Implications for Radial Diffusion Processes

Jasmine Sandhu, Jonathan Rae, John Wygant, Aaron Breneman, Sheng Tian, Frances Staples, Maria-Theresia Walach, David Hartley, Clare Watt, Kyle Murphy, Tom Elsden, Richard Horne, Louis Ozeke, and Marina Georgiou

Ultra Low Frequency (ULF) waves drive radial diffusion of radiation belt electrons, where this process contributes to and, at times, dominates energisation, loss, and large scale transport of the outer radiation belt. In this study we quantify the changes and variability in ULF wave power during geomagnetic storms, through a statistical analysis of Van Allen Probes data for the time period spanning 2012 – 2019. The results show that global wave power enhancements occur during the main phase, and continue into the recovery phase of storms. Local time asymmetries show sources of ULF wave power are both external solar wind driving as well as internal sources from coupling with ring current ions and substorms.

The statistical analysis demonstrates that storm time ULF waves are able to access lower L values compared to pre-storm conditions, with enhancements observed within L = 4. We assess how magnetospheric compressions and cold plasma distributions shape how ULF wave power propagates through the magnetosphere. Results show that the Earthward displacement of the magnetopause is a key factor in the low L enhancements. Furthermore, the presence of plasmaspheric plumes during geomagnetic storms plays a crucial role in trapping ULF wave power, and contributes significantly to large storm time enhancements in ULF wave power.

The results have clear implications for enhanced radial diffusion of the outer radiation belt during geomagnetic storms. Estimates of storm time radial diffusion coefficients are derived from the ULF wave power observations, and compared to existing empirical models of radial diffusion coefficients. We show that current Kp-parameterised models, such as the Ozeke et al. [2014] model, do not fully capture the large variability in storm time radial diffusion coefficients or the extent of enhancements in the magnetic field diffusion coefficients.

How to cite: Sandhu, J., Rae, J., Wygant, J., Breneman, A., Tian, S., Staples, F., Walach, M.-T., Hartley, D., Watt, C., Murphy, K., Elsden, T., Horne, R., Ozeke, L., and Georgiou, M.: ULF Wave Power During Geomagnetic Storms and Implications for Radial Diffusion Processes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11203, https://doi.org/10.5194/egusphere-egu21-11203, 2021.

EGU21-9850 | vPICO presentations | ST2.4

Methodology for calculation of radial diffusion coefficients for a relativistic electron population from hybrid-Vlasov simulation

Harriet George, Emilia Kilpua, Adnane Osmane, Urs Ganse, Solene Lejosne, Milla Kalliokoski, Lucile Turc, Markus Battarbee, Yann Pfau-Kempf, Maarja Bussov, Maxime Grandin, Andreas Johlander, Jonas Suni, Maxime Dubart, Konstantinos Papadakis, Markku Alho, Hongyang Zhou, and Minna Palmroth

The relative importance of radial diffusion and local acceleration to the dynamics of outer radiation belt electron populations is an open question in radiation belt physics. A key component of this discussion is the calculation of the radial diffusion coefficients, which quantify the effect of radial diffusion on an electron population. However, there is currently a broad range of radial diffusion coefficient values in the literature, which presents difficulties when determining the dominant process governing radiation belt energisation. Here we develop a methodology for the calculation of radial diffusion coefficients using Vlasiator, a 5D hybrid-Vlasov simulation of near-Earth space, and calculate the radial diffusion coefficients for a 10 MeV electron population at multiple locations within the outer radiation belt.

 

Vlasiator currently models ions as velocity distribution functions and electrons as a magnetohydrodynamic fluid, so the drift motion of the electron population can not be directly studied. However, the ion dynamics accurately determine the magnetic field in the inner magnetosphere, and the spatial and temporal magnetic field variations can be used to calculate the radial diffusion coefficient of a population according to principles outlined in Lejosne et. al. 2020.  Four magnetic field isocontours in the outer radiation belt are used to model the guiding centre drift contours of an electron population, and the corresponding Roederer L-star coordinates are calculated from the magnetic flux through each of these drift contours. The variation of the L-stars over time are calculated from population-specific variables and the Lagrangian magnetic field time derivative along the magnetic isocontours. The radial diffusion coefficients for the 10 MeV electron population are then calculated at each of these L-stars and compared to the literature. This methodology produces radial diffusion coefficients from Vlasiator that have the expected L-shell dependence and are consistent with the literature, including studies based on satellite measurements of radiation belt electrons. These results indicate that this is a valid methodology for the calculation of radial diffusion coefficients, and can therefore be extended to evaluate the radial diffusion coefficients in different solar wind conditions and at more L-stars.

How to cite: George, H., Kilpua, E., Osmane, A., Ganse, U., Lejosne, S., Kalliokoski, M., Turc, L., Battarbee, M., Pfau-Kempf, Y., Bussov, M., Grandin, M., Johlander, A., Suni, J., Dubart, M., Papadakis, K., Alho, M., Zhou, H., and Palmroth, M.: Methodology for calculation of radial diffusion coefficients for a relativistic electron population from hybrid-Vlasov simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9850, https://doi.org/10.5194/egusphere-egu21-9850, 2021.

EGU21-10563 | vPICO presentations | ST2.4

Radial diffusion coefficients database in the frame of SafeSpace project

Christos Katsavrias, Ioannis A. Daglis, Afroditi Nasi, Constantinos Papadimitriou, and Marina Georgiou

Radial diffusion has been established as one of the most important mechanisms contributing the acceleration and loss of relativistic electrons in the outer radiation belt. Over the past few years efforts have been devoted to provide empirical relationships of radial diffusion coefficients (DLL) for radiation belt simulations yet several studies have suggested that the difference between the various models can be orders of magnitude different at high levels of geomagnetic activity as the observed DLL have been shown to be highly event-specific. In the frame of SafeSpace project we have used 12 years (2009 – 2020) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of calculated DLL. In this work we present the first statistics on the evolution of DLL during the various phases of Solar cycle 24 with respect to the various solar wind parameters and geomagnetic indices.

This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437.

How to cite: Katsavrias, C., Daglis, I. A., Nasi, A., Papadimitriou, C., and Georgiou, M.: Radial diffusion coefficients database in the frame of SafeSpace project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10563, https://doi.org/10.5194/egusphere-egu21-10563, 2021.

EGU21-11390 | vPICO presentations | ST2.4

Quantifying the dependence of electron fluxes in the Earth’s radiation belts with radial diffusion drivers through the use of information theory.

Adnane Osmane, Mikko Savola, Emilia Kilpua, Hannu Koskinen, Joe Borovsky, and Milla Kalliokoski

We describe the use of information-theoretic methodologies to characterise statistical dependencies of energetic electron fluxes (130 keV and >1 MeV) with a wide range of solar wind and magnetospheric drivers. We focus specifically on drivers associated with radial diffusion processes and revisit the events studied by Rostoker et al. Geophys. Res. Lett. (1998) in terms of mutual information. The main benefit of mutual information, in comparison to the Pearson correlation and other linear measures, lies in the capacity to distinguish nonlinear statistical dependencies from linear ones.  We find that observed enhancement in relativistic electron fluxes correlate weakly, both linearly and nonlinearly, with the ULF power spectrum, whereas less energetic electron fluxes show stronger statistical dependency with both ground and in situ ULF wave power. Our results are indicative of the need to incorporate data analysis tools that can distinguish between interdependencies of various solar wind drivers.

How to cite: Osmane, A., Savola, M., Kilpua, E., Koskinen, H., Borovsky, J., and Kalliokoski, M.: Quantifying the dependence of electron fluxes in the Earth’s radiation belts with radial diffusion drivers through the use of information theory., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11390, https://doi.org/10.5194/egusphere-egu21-11390, 2021.

EGU21-7342 | vPICO presentations | ST2.4

A Proton Flux Model Dedicated to Solar Arrays Degradations on Electric Orbit Raising Missions

Antoine Brunet, Angélica Sicard, Constantinos Papadimitriou, and Didier Lazaro

Electric Orbit Raising (EOR) for telecommunication satellites has allowed significant reduction in onboard fuel mass, at the price of extended transfer durations. These relatively long orbital transfers, which can take up to a few months, equatorially cross most of the radiation belts, resulting in significant exposure of the spacecraft to space radiations. Since there are not covered by many spacecrafts, the radiation environment of intermediate regions of the radiation belts is less known than on popular orbits such as LEO or GEO. In particular, there is a need for more specific models for the MeV energy range proton fluxes, responsible for solar arrays degradations. We present a model of proton fluxes dedicated for EOR missions that was developped as part of the ESA ARTES program. This model is able to estimate the average proton fluxes between 60 keV and 10MeV on arbitrary trajectories on the typical durations of EOR transfers. A global statistical model of the radiation belts was extracted from the Van Allen Probes (RBSP) RBSPICE data and enriched by simulation results from the Salammbô radiation belt model were used. A special care was taken to model the temporal dynamics of the proton belt, allowing to compute analytically the distribution of the average fluxes on arbitrary EOR missions.

How to cite: Brunet, A., Sicard, A., Papadimitriou, C., and Lazaro, D.: A Proton Flux Model Dedicated to Solar Arrays Degradations on Electric Orbit Raising Missions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7342, https://doi.org/10.5194/egusphere-egu21-7342, 2021.

EGU21-5780 | vPICO presentations | ST2.4

A real time forecast of the electron fluxes measured by GOES 16

Richard Boynton, Michael Balikhin, and Hualiang Wei

A real time system is developed to forecast the electron fluxes measured by GOES R spacecraft. Forecast models are developed using the system identification/machine learning methodology based on Nonlinear Autoregressive Moving Average exogenous (NARMAX) models. NARMAX algorithms use past input-output data to automatically deduce a model of the system. Here, the solar wind parameters are used as inputs and the electron fluxes measured by GOES 16 are used as the outputs to deduce the models. The models are then implemented in a real time forecasting system. The forecasting system uses real time solar wind data from ACE, DSCOVR, and ENLIL, which are then processed into the correct format for the NARMAX models to provide a forecast of the electron fluxes at geostationary orbit. 

How to cite: Boynton, R., Balikhin, M., and Wei, H.: A real time forecast of the electron fluxes measured by GOES 16, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5780, https://doi.org/10.5194/egusphere-egu21-5780, 2021.

EGU21-12599 | vPICO presentations | ST2.4

Magnetopause Shadowing Characteristics in Phase Space Density Measurements

Frances Staples, Jonathan Rae, Adam Kellerman, Kyle Murphy, Jasmine Sandhu, and Colin Forsyth

Loss mechanisms act independently or in unison to drive rapid loss of electrons in the radiation belts. Electrons may be lost by precipitation into the Earth’s atmosphere, or through the magnetopause into interplanetary space. Whilst this magnetopause shadowing is well understood to produce dropouts in electron flux, it is less clear if shadowing continues to remove particles in tandem with electron acceleration processes, limiting the overall flux increase. 

We investigate the contribution of shadowing to overall radiation belt fluxes throughout a geomagnetic storm in early September 2017. We use new, multi-spacecraft phase space density calculations to decipher electron dynamics during each storm phase and identify features of magnetopause shadowing during both the net-loss and the net-acceleration storm phases. We also highlight two distinct types of shadowing; ‘Indirect’, where electrons are lost through ULF wave driven radial transport towards the magnetopause boundary, and ‘direct’, where electrons are lost as their orbit intersects the magnetopause. 

How to cite: Staples, F., Rae, J., Kellerman, A., Murphy, K., Sandhu, J., and Forsyth, C.: Magnetopause Shadowing Characteristics in Phase Space Density Measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12599, https://doi.org/10.5194/egusphere-egu21-12599, 2021.

We analyze variations of energetic particle fluxes measured by low altitude spacecraft after interplanetary shock arrivals and around the times of significant geomagnetic storms. Data from two different spacecraft and energetic particle detectors are used and compared. First, we use data measured by the energetic particle detector (IDP) onboard the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft. The spacecraft operated between 2004 and 2010 on a circular Sun-synchronous orbit at an altitude of initially 710 km, which was decreased to 660 km in December 2005. The IDP instrument measured electron flux close to the loss cone at energies between about 70 keV and 2.3 MeV (128 energy channels). Second, we use data measured by the Space Application of Timepix Radiation Monitor (SATRAM) onboard the Proba-V satellite operating since May 2013 on a circular Sun-synchronous orbit at an altitude of 820 km. The semi-conductor based pixelated radiation detector called Timepix is capable of detecting all charged particles and X-rays with sufficiently high energies. Electron energies higher than about 2 MeV and proton energies higher than about 20 MeV are detected. We identify the times of interplanetary shock arrivals and significant (Dst < –100 nT) geomagnetic storms during the mission durations. Then we perform a superposed epoch analysis to reveal characteristic particle flux variations around these times at different energies and L-shells. Although the used satellite missions do not overlap in time, we aim to compare the revealed flux variation signatures between these two independent data sets.

How to cite: Gohl, S., Němec, F., and Parrot, M.: Variations of energetic particle fluxes after interplanetary shock arrivals and around significant geomagnetic storms observed by low altitude spacecraft, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2817, https://doi.org/10.5194/egusphere-egu21-2817, 2021.

EGU21-9742 | vPICO presentations | ST2.4

Phase space density analysis of outer radiation belt electron energization and loss during geoeffective and non-geoeffective sheath regions

Milla Kalliokoski, Emilia Kilpua, Adnane Osmane, Allison Jaynes, Drew Turner, Harriet George, Lucile Turc, and Minna Palmroth

The energetic electron content in the Van Allen radiation belts surrounding the Earth can vary dramatically on timescales from minutes to days, and these electrons present a hazard for spacecraft traversing the belts. The outer belt response to solar wind driving is however yet largely unpredictable. Here we investigate the driving of the belts by sheath regions preceding interplanetary coronal mass ejections. Electron dynamics in the belts is governed by various competing acceleration, transport and loss processes. We analyzed electron phase space density to compare the energization and loss mechanisms during a geoeffective and a non-geoeffective sheath region. These two case studies indicate that ULF-driven inward and outward radial transport, together with the incursions of the magnetopause, play a key role in causing the outer belt electron flux variations. Chorus waves also likely contribute to energization during the geoeffective event. A global picture of the wave activity is achieved through a chorus proxy utilizing POES measurements. We highlight that also the non-geoeffective sheath presented distinct changes in outer belt electron fluxes, which is also evidenced by our statistical study of outer belt electron fluxes during sheath events. While not as intense as during geoeffective sheaths, significant changes in outer belt electron fluxes occur also during sheaths that do not cause major geomagnetic disturbances.

How to cite: Kalliokoski, M., Kilpua, E., Osmane, A., Jaynes, A., Turner, D., George, H., Turc, L., and Palmroth, M.: Phase space density analysis of outer radiation belt electron energization and loss during geoeffective and non-geoeffective sheath regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9742, https://doi.org/10.5194/egusphere-egu21-9742, 2021.

EGU21-10061 | vPICO presentations | ST2.4

Radiation belt electron acceleration during periods of low plasma density

Hayley Allison, Yuri Shprits, Irina Zhelavskaya, Dedong Wang, and Artem Smirnov

Electrons in the Van Allen radiation belts can have energies in excess of 7 MeV. We present a unique way of analyzing phase space density data which demonstrates that local acceleration is capable of heating electrons up to 7 MeV. The Van Allen Probes mission not only provided unique measurements of ultra-relativistic radiation belt electrons, but also simultaneous observations of plasma waves that allowed for the routine inference of total plasma number density. Based on long-term observations, we show that the underlying plasma density has a controlling effect over local acceleration to ultra-relativistic energies, which occurs only when the plasma number density drops down to very low values (~10 cm-3). The VERB-2D model is used to simulate ultra-relativistic electron acceleration during an event which exhibits an extreme cold plasma depletion. The results show that a reduced electron plasma density allows chorus waves to efficiently resonate with electrons up to ultra-relativistic energies, producing enhancements from 100s of keV up to >7 MeV via local diffusive acceleration. We analyse statistically the observed chorus wave power during ultra-relativistic enhancement events, considering the contribution from both upper and lower band chorus waves. The PINE density model allows for the investigation of global magnetospheric density changes. We analyze the how the global cold plasma density changes during ultra-relativistic enhancement events and compare to in-situ point measurements of the plasma density.

How to cite: Allison, H., Shprits, Y., Zhelavskaya, I., Wang, D., and Smirnov, A.: Radiation belt electron acceleration during periods of low plasma density, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10061, https://doi.org/10.5194/egusphere-egu21-10061, 2021.

EGU21-11753 | vPICO presentations | ST2.4

Coordinated observations of relativistic electron enhancements following an HSS period 

Afroditi Nasi, Ioannis A. Daglis, Christos Katsavrias, Ingmar Sandberg, Wen Li, Yoshizumi Miyoshi, Shun Imajo, Takefumi Mitani, Tomo Hori, Satoshi Kasahara, Shoichiro Yokota, Kunihiro Keika, Iku Shinohara, Ayako Matsuoka, and Yoshiya Kasahara

During the second half of 2019, a sequence of solar wind high-speed streams (VSW ≥ 600 km/s)  impacted the magnetosphere, resulting in a series of recurrent, relatively weak, geomagnetic storms (Dstmin ≥ - 80 nT). During one of these storms, a longer-lasting solar wind pressure pulse and intense substorm activity were also recorded (AL ≤ - 1600 nT on August 31 and September 1).

We use particle measurements from the Van Allen Probes, Arase and Galileo 207, 215 satellites, to investigate this event; all spacecraft observed a significant enhancement of relativistic electron fluxes. We also use ULF and chorus wave measurements, as well as interplanetary parameters, for a detailed investigation of this event and of the acceleration mechanisms involved.

This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace project.

How to cite: Nasi, A., Daglis, I. A., Katsavrias, C., Sandberg, I., Li, W., Miyoshi, Y., Imajo, S., Mitani, T., Hori, T., Kasahara, S., Yokota, S., Keika, K., Shinohara, I., Matsuoka, A., and Kasahara, Y.: Coordinated observations of relativistic electron enhancements following an HSS period , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11753, https://doi.org/10.5194/egusphere-egu21-11753, 2021.

EGU21-6508 | vPICO presentations | ST2.4

Stochastic differential equations for modeling of nonlinear wave-particle interaction

Alexander Lukin, Anton Artemyev, and Anatoly Petrukovich

The charged particle resonant interaction with electromagnetic waves propagating in an inhomogeneous plasma determines the dynamics of plasma populations in various space plasma systems, such as shock waves, radiation belts, and plasma injection regions. For systems with small wave amplitudes and a broad wave spectrum, such resonant interaction is well described within a framework of the quasi-linear theory, which is based on the Fokker-Planck diffusion equation. However, in systems with intense waves, this approach is inapplicable, because nonlinear resonant effects (such as phase bunching and phase trapping) and non-diffusive processes play an essential role in the acceleration and scattering of charged particles. In this work we consider a generalized approach for modelling of wave-particle resonant interaction for intense coherent waves. This approach is based on application of stochastic differential equations for simulation resonant scattering and trapping. To test and verify an applicability of this approach, we use a simple model system with high-amplitude electrostatic whistler waves and energetic electrons propagating in the Earth radiation belts. We show that the proper determination of the model parameters allows us to describe the dynamics of the electron distribution function evolutions dominated by nonlinear resonant effects. Moreover, the proposed approach significantly reduces the calculation time in comparison with test particles methods generally used for simulations of nonlinear wave-particle interactions.

How to cite: Lukin, A., Artemyev, A., and Petrukovich, A.: Stochastic differential equations for modeling of nonlinear wave-particle interaction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6508, https://doi.org/10.5194/egusphere-egu21-6508, 2021.

EGU21-5398 | vPICO presentations | ST2.4

Electron pitch angle diffusion and rapid transport/advection during nonlinear interactions with whistler-mode waves

Oliver Allanson, Clare Watt, Hayley Allison, and Heather Ratcliffe

Radiation belt numerical models utilize diffusion codes that evolve electron dynamics due to resonant wave-particle interactions. It is not known how to best incorporate electron dynamics in the case of a wave power spectrum that varies considerably on a 'sub-grid' timescale shorter than the computational time-step Δt, particularly if the wave amplitude reaches high values. Timescales associated with the growth rate, γ, of thermal instabilities are very short, and typically Δt>>1/γ. We use a kinetic code to study electron interactions with whistler-mode waves in the presence of a background plasma with thermally anisotropic components, as frequently occur within the magnetosphere. For low values of anisotropy, thermal instabilities are not triggered and we observe similar results to those obtained in Allanson et al. (2020, https://doi.org/10.1029/2020JA027949), for which the diffusion matched the quasilinear theory over short timescales inversely proportional to wave power. For high levels of anisotropy, wave growth via instability is triggered. Dynamics are not well described by the quasilinear theory when calculated using the average wave power. During the growth phase (~0.1s) we observe strong diffusive and advective components, which both saturate as the wave power saturates at ~ 1nT. The advective motions dominate over the diffusive processes. The growth phase facilitates significant transport in electron pitch angle space via successive resonant interactions with waves of different frequencies. This motivates future work on the longer-time impact of very short timescale processes in radiation belt modelling, and on the indirect effects of anisotropic background plasma components on electron scattering. We suggest that this rapid advective transport during nonlinear wave growth phase may have a role to play in the electron microburst mechanism.

[Allanson et al, JGR Space Physics, 2021 (under review)]

How to cite: Allanson, O., Watt, C., Allison, H., and Ratcliffe, H.: Electron pitch angle diffusion and rapid transport/advection during nonlinear interactions with whistler-mode waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5398, https://doi.org/10.5194/egusphere-egu21-5398, 2021.

EGU21-13086 | vPICO presentations | ST2.4

Chorus and hiss scales in the inner magnetosphere: statistics from high-resolution filter bank (FBK) Van Allen Proves multi-point measurements

Oleksiy Agapitov, Didier Mourenas, Anton Artemyev, Aaron Breneman, John Bonnell, George Hospodarsky, and John Wygant

The spatial scales of whistler-mode waves, determined by their generation process, propagation, and damping, are important for assessing the scaling and efficiency of wave-particle interactions affecting the dynamics of the radiation belts. We use multi-point wave measurements in 2013-2019 by two identically equipped Van Allen Probes spacecraft covering all MLTs at L=2-6 near the geomagnetic equator to investigate the spatial extent of active regions of chorus and hiss waves, their wave amplitude distribution in the source/generation region, and the scales of chorus wave packets, employing a time-domain correlation technique to the spacecraft approaches closer than 1000 km, which happened every 70 days in 2012-2018 and every 35 days in 2018-2019. The correlation of chorus wave power dynamics using two spacecraft measurements is found to remain significant up to inter-spacecraft separations of 400 km to 750 km transverse to the background magnetic field direction, consistent with previous estimates of the chorus wave packet extent, but indicating the likely presence of two different scales of about 400 km and 750 km. Our results further suggest that the chorus source region can be slightly asymmetrical, more elongated in either the azimuthal or radial direction, which could also explain the aforementioned two different scales. An analysis of average chorus and hiss wave amplitudes at separate locations similarly reveals different radial and azimuthal extents of the corresponding wave active regions, complementing previous results based on THEMIS spacecraft statistics mainly at larger L>6. Both the chorus source region scale and the chorus active region size appear smaller inside the outer radiation belt (at L< 6) than at higher L-shells.

How to cite: Agapitov, O., Mourenas, D., Artemyev, A., Breneman, A., Bonnell, J., Hospodarsky, G., and Wygant, J.: Chorus and hiss scales in the inner magnetosphere: statistics from high-resolution filter bank (FBK) Van Allen Proves multi-point measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13086, https://doi.org/10.5194/egusphere-egu21-13086, 2021.

EGU21-10390 | vPICO presentations | ST2.4

Conjugate pulsating aurora and chorus waves: case study at high temporal resolution 

Shannon Hill, Robert Michell, Marilia Samara, Tuija Pulkkinen, Donald Hampton, John Bonnell, Oleksiy Agapitov, Aaron Breneman, and Sheng Tian

EGU21-14307 | vPICO presentations | ST2.4

On Resonant Interaction of Electrons with Falling-Tone Chorus Waves

Ilya Kuzichev and Angel Rualdo Soto-Chavez

Whistler-mode chorus waves are one of the most intense wave phenomena in the Earth’s inner magnetosphere. They are considered to be a major driver of the outer radiation belt dynamics, as they can efficiently scatter and energize electrons via resonant wave-particle interaction. These waves are observed as series of discrete coherent structures with rising or falling frequencies in the whistler frequency range (below local electron cyclotron frequency).

Such frequency variation results in a correction to the resonance Hamiltonian which describes particle dynamics in the given wave field. For a monochromatic wave, the effective potential in the resonance Hamiltonian consists of two terms. The first one corresponds to the nonlinear pendulum and describes the direct interaction of a particle with the wave. The second term accounts for plasma inhomogeneity, describing the effects of spatial gradients of plasma and wave parameters on the particle. Frequency chirping contributes to this effective inhomogeneity, producing a correction to this second term. The inhomogeneity term is of particular importance for the trapped particles that remain in resonance with the wave, this term defines their acceleration. And, as spatial inhomogeneity becomes zero at the equator (for dipole magnetic field), the wave frequency variation contribution might be the dominant one close to this region.

In this report, we present the results of test particle simulations of the electron dynamics in the field of a chirped wave. A general curvilinear relativistic code is developed to address the particle dynamics in the wave field, pre-determined from the simplified wave equations. We demonstrate that particle acceleration is affected by the competition between the effective inhomogeneity related to the wave frequency chirping and spatial inhomogeneity of the Earth’s magnetic field.

The work is supported by the National Science Foundation (NSF) grant No. 1502923. We would like to acknowledge high-performance computing support from Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR’s Computational and Information Systems Laboratory, sponsored by NSF

How to cite: Kuzichev, I. and Soto-Chavez, A. R.: On Resonant Interaction of Electrons with Falling-Tone Chorus Waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14307, https://doi.org/10.5194/egusphere-egu21-14307, 2021.

EGU21-12877 | vPICO presentations | ST2.4

Sub-ion magnetic holes in the plasma injection region: origins and dynamics

Pavel Shustov, Anton Artemyev, Alexander Volokitin, Ivan Vasko, Xiao-Jia Zhang, and Anatoliy Petrukovich

Recent spacecraft observations of plasma injections reveal abundance of small-scale nonlinear magnetic structures – sub-ion magnetic holes. These structures contribute to magnetosphere-ionosphere coupling and likely responsible for energetic electron scattering. Sub-ion magnetic holes propagate in plasma of two electron components with very different temperatures. Properties of such holes resemble properties of classical magnetosonic solitary waves propagating across the ambient magnetic field, but observations suggest that these holes do not disturb background ions. This study aims to generalize the linear theory of magnetosonic waves by including two electron components. In analog to the electron acoustic mode, cold electrons can act as ions for the generation of magnetosonic mode waves. This unstable electron magnetosonic mode can explain all properties of sub-ion holes in observations. We suggest that sub-ion holes can form during the nonlinear evolution this electron magnetosonic mode. We consider an adiabatic model for investigation of such nonlinear evolution and electron dynamical response to evolving hole electromagnetic field. This model describes slow formation of sub-ion magnetic holes from low-amplitude limit. The adiabatic electron response to such formation can include both electron colling and heating, for populations with different pitch-angles.

The work was supported by the Russian Scientific Foundation, project 19-12-00313.

How to cite: Shustov, P., Artemyev, A., Volokitin, A., Vasko, I., Zhang, X.-J., and Petrukovich, A.: Sub-ion magnetic holes in the plasma injection region: origins and dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12877, https://doi.org/10.5194/egusphere-egu21-12877, 2021.

EGU21-7203 | vPICO presentations | ST2.4

Comparison of different techniques to estimate the direction of the Poynting vector of EMIC emissions

Benjamin Grison and Ondrej Santolik

Electromagnetic Ion Cyclotron (EMIC) waves usually grow in the inner magnetosphere from hot ion temperature anisotropy. The main source region is located close to the magnetic equator and there is a secondary EMIC source region off the magnetic equator in the dayside magnetosphere. The source region can be identified using measurements of the Poynting vector direction.

The Poynting vector is ideally derived from the measurement of 3 components of the wave electric field and 3 components of components of the wave magnetic field. However, spinning spacecraft often have only two long mutually perpendicular electric antennas in the spin plane, deployed by the centrifugal force. The third antenna, when present, is usually shorter owing to difficulties of deploying a antenna along the spin axis.

Estimations of the Poynting vector from measurements of three magnetic field components and two electric field components can be obtained assuming the presence of a single plane wave (and thus perpendicularity of the electric field and the magnetic field vectors, according to the Faraday’s law), following the method developed by Loto'aniu et al. (2005). Applying this method to Cluster data, Allen et al. (2013) found the presence of bidirectional EMIC emissions off the magnetic equatorial region.

Another technique proposed earlier by Santolík et al. (2001) considers the phase shift estimation between the electric signals from each antenna and synthetic perpendicular magnetic field components obtained from the three-dimensional measurements. The method is based on cross-spectral estimates in the frequency domain and can be used to estimate sign of each component of the Poynting vector. Using this technique Grison et al. (2016) showed the importance of the transverse component of the EMIC emissions far from the source region.

We compare these methods for different events to check how the results of these two techniques differ. We also discuss what we can learn about the EMIC source region from these measurements.

How to cite: Grison, B. and Santolik, O.: Comparison of different techniques to estimate the direction of the Poynting vector of EMIC emissions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7203, https://doi.org/10.5194/egusphere-egu21-7203, 2021.

EGU21-621 | vPICO presentations | ST2.4

Direct measurements of cold and hot plasma composition and EMIC waves in the outer magnetosphere: Implications for inner magnetosphere wave-particle interactions

Justin Lee, Drew Turner, Sarah Vines, Robert Allen, and Sergio Toledo-Redondo

Although thorough characterization of magnetospheric ion composition is rare for EMIC wave studies, convective processes that occur more frequently in Earth’s outer magnetosphere have allowed the Magnetospheric Multiscale (MMS) satellites to make direct measurements of the cold and hot plasma composition during EMIC wave activity. We will present an observation and linear wave modeling case study conducted on EMIC waves observed during a perturbed activity period in the outer dusk-side magnetosphere. During the two intervals investigated for the case study, the MMS satellites made direct measurements of cold plasmaspheric plasma in addition to multiple hot ion components at the same time as EMIC wave emissions were observed. Applying the in-situ plasma composition data to wave modeling, we find that wave growth rate is impacted by the complex interactions between the cold as well as the hot ion components and ambient plasma conditions. In addition, we observe that linear wave properties (unstable wave numbers and band structure) can significantly evolve with changes in cold and hot ion composition. Although the modeling showed the presence of dense cold ions can broaden the range of unstable wave numbers, consistent with previous work, the hot heavy ions that were more abundant nearer storm main phase could limit the growth of EMIC waves to smaller wave numbers. In the inner magnetosphere, where higher cold ion density is expected, the ring current heavy ions could also be more intense near storm-time, possibly resulting in conditions that limit the interactions of EMIC waves with trapped radiation belt electrons to multi-MeV energies. Additional investigation when direct measurements of cold and hot plasma composition are available could improve understanding of EMIC waves and their interactions with trapped energetic particles in the inner magnetosphere.

How to cite: Lee, J., Turner, D., Vines, S., Allen, R., and Toledo-Redondo, S.: Direct measurements of cold and hot plasma composition and EMIC waves in the outer magnetosphere: Implications for inner magnetosphere wave-particle interactions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-621, https://doi.org/10.5194/egusphere-egu21-621, 2021.

EGU21-7351 | vPICO presentations | ST2.4

Kinetic interaction of cold and hot protons with an oblique EMIC wave near the dayside reconnecting magnetopause

Sergio Toledo-Redondo, Justin H. Lee, Sarah K. Vines, Drew L. Turner, Robert C. Allen, Mats André, Scott A. Boardsen, James L. Burch, Richard E. Denton, Huishan Fu, Stephen A. Fuselier, Barbara Giles, Naritoshi Kitamura, Yuri V. Khotyaintsev, Benoit Lavraud, Olivier LeContel, Wenya Li, Enrique A. Navarro, Jorge Portí, and Alfonso Salinas

We report observations of the ion dynamics inside an Alfven branch wave that propagates near the reconnecting dayside magnetopause. The measured frequency, wave normal angle and polarization are within 1% with the predictions of a dispersion solver, and indicate that the wave is an electromagnetic ion cyclotron wave with very oblique wave vector. The magnetospheric plasma contains hot protons (keV), cold protons (eV), plus some heavy ions. The cold protons follow the magnetic field fluctuations and remain frozen-in, while the hot protons are at the limit of magnetization.

The cold proton velocity fluctuations contribute to balance the Hall term in Ohm's law, allowing the wave polarization to be highly-elliptical and right-handed, a necessary condition for propagation at oblique wave normal angles. The dispersion solver indicates that increasing the cold proton density facilitates generation and propagation of these waves at oblique angles, as it occurs for the observed wave.

How to cite: Toledo-Redondo, S., Lee, J. H., Vines, S. K., Turner, D. L., Allen, R. C., André, M., Boardsen, S. A., Burch, J. L., Denton, R. E., Fu, H., Fuselier, S. A., Giles, B., Kitamura, N., Khotyaintsev, Y. V., Lavraud, B., LeContel, O., Li, W., Navarro, E. A., Portí, J., and Salinas, A.: Kinetic interaction of cold and hot protons with an oblique EMIC wave near the dayside reconnecting magnetopause, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7351, https://doi.org/10.5194/egusphere-egu21-7351, 2021.

EGU21-12858 | vPICO presentations | ST2.4 | Highlight

Properties of molecular ions in the ring current and their supply mechanism from the low-altitude ionosphere

Kanako Seki, Masayoshi Takada, Kunihiro Keika, Satoshi Kasahara, Shoichiro Yokota, Tomoaki Hori, Kazushi Asamura, Nana Higashio, Yasunobu Ogawa, Ayako Matsuoka, Mariko Teramoto, Yoshizumi Miyoshi, and Iku Shinohara

Molecular ions usually exist only in the low-altitude (< 300 km) ionosphere and cannot escape to space without a fast ion upflow/outflow to overcome a rapid loss due to dissociative recombination (e.g., Peterson et al., 1994). Thus, molecular ion escape from the terrestrial atmosphere to space can be used as a tracer of effective ion loss from the deep ionosphere. Reports on molecular ion observations in the ring current are limited to some event studies (e.g., Klecker et al., 1986) and their statistical properties are far from understood. Here we report observations by the Arase (ERG) satellite which enables definitive identification of molecular ions (O2+/NO+/N2+) by frequent TOF (time-of-flight) mode observations (Seki et al., 2019) and a simultaneous observation by the EISCAT radar and Arase to investigate the mechanisms to cause the fast upward ion transport in the deep ionosphere (Takada et al., submitted, 2021).

Statistical properties of molecular ions in the ring current are investigated based on ion composition measurements (<180 keV/q) by MEPi and LEPi instruments onboard Arase. The investigated period from late March to December 2017 includes 11 geomagnetic storms with the minimum Dst index less than -40 nT. The molecular ions are observed in association with geomagnetic disturbances with Dst < -30 nT. During quiet times, molecular ions are not observed. The tendency is consistent with previous observations. The molecular ions are observed mainly in the region of L=3.5-6.6 and clearly identified at energies above ~14 keV with molecularto O+ ion energy density ratio of the order of 1 percent. Detection probability of molecular ions in the ring current becomes higher with increasing size of geomagnetic storms (minimum Dst index). Their detection probability also tends to be higher during substorms as well as during high-speed solar wind period. The observation probability of the molecular ions in the ring current is comparable or higher than that in the high-altitude auroral regions, suggesting the importance of the subauroral zone. Existence of molecular ions even during small magnetic storms suggests that the fast ion outflow from the deep ionosphere occurs frequently during geomagnetically active periods. In order to understand the mechanism of the molecular ion supply to the magnetosphere, we will also briefly report on an event study of the ion upflow in the low-altitude (250-350 km) ionosphere observed by EISCAT during the storm main phase on September 8, 2017, when Arase observed molecular ions in the ring current.

 

References:

  • Klecker et al., Geophys. Res. Lett., 13, 632-635, 1986.
  • Peterson et al., J. Geophys. Res., 99, 23257-23274, 1994.
  • Seki et al., Geophys. Re. Lett., 46, doi:10.1029/2019GL084163, 2019.

How to cite: Seki, K., Takada, M., Keika, K., Kasahara, S., Yokota, S., Hori, T., Asamura, K., Higashio, N., Ogawa, Y., Matsuoka, A., Teramoto, M., Miyoshi, Y., and Shinohara, I.: Properties of molecular ions in the ring current and their supply mechanism from the low-altitude ionosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12858, https://doi.org/10.5194/egusphere-egu21-12858, 2021.

EGU21-13927 | vPICO presentations | ST2.4

The Ionospheric Source of the Plasma Sheet During Storm Main Phase

Lynn M. Kistler, Christopher G. Mouikis, Kazushi Asamura, Satoshi Kasahara, Yoshizumi Miyoshi, Kunihiro Keika, Steven M. Petrinic, Tomoaki Hori, Shoichiro Yokota, and Iku Shinohara

The ionospheric and solar wind contributions to the magnetosphere can be distinguished by their composition.  While both sources contain significant H+, the heavy ion species from the ionospheric source are generally singly ionized, while the solar wind consists of highly ionized ions. Both the solar wind and the ionosphere contribute to the plasma sheet.  It has been shown that with both enhanced geomagnetic activity and enhanced solar EUV, the ionospheric contribution, and particularly the ionospheric heavy ions contribution increases.  However, the details of this transition from a solar wind dominated to more ionospheric dominated plasma sheet are not well understood.  An initial study using AMPTE/CHEM data, a data set that includes the full charge state distributions of the major species, shows that the transition can occur quite sharply during storms, with the ionospheric contribution becoming dominant during the storm main phase.  However, during the AMPTE time-period, there were no continuous measurements of the upstream solar wind, and so both the simultaneous solar wind composition and the driving solar wind and IMF parameters were not known.  The HPCA instrument on MMS and both the LEPi and MEPi instruments on Arase are able to measure He++.   With these data sets, the He++/H+ ratio can be compared to the simultaneous He++/H+ ratios in the solar wind to more definitively identify the solar wind contribution to the plasma sheet.  This allows the ionospheric contribution to the H+ population to be determined, so that the full ionospheric population is known. We find that when the IMF turns southward during the storm main phase, the dominant source of the hot plasma sheet becomes ionospheric.  This composition change explains why the storm time ring current also has a high ionospheric contribution.

How to cite: Kistler, L. M., Mouikis, C. G., Asamura, K., Kasahara, S., Miyoshi, Y., Keika, K., Petrinic, S. M., Hori, T., Yokota, S., and Shinohara, I.: The Ionospheric Source of the Plasma Sheet During Storm Main Phase, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13927, https://doi.org/10.5194/egusphere-egu21-13927, 2021.

EGU21-13991 | vPICO presentations | ST2.4

The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations

Niloufar Nowrouzi, Lynn Kistler, Eric Lund, and Kai Zhao

Sawtooth events are repeated injections of energetic particles at geosynchronous orbit. Although studies have shown that 94% of sawtooth events occur during  magnetic storm times, the main factor that causes a sawtooth event is unknown. Simulations have suggested that heavy ions like O+ may play a role in driving the sawtooth mode by increasing the magnetotail pressure and causing the magnetic tail to stretch. O+ ions located in the nightside auroral region have a direct access to the near-earth plasma-sheet. O+ in the dayside cusp can reach to the midtail plasma-sheet when the convection velocity is sufficiently strong. Whether the dayside or nightside source is more important is not known.

We show results of a statistical study of the variation of the O+ and H+ outflow flux during sawtooth events for SIR and ICME sawtooth events. We perform a superposed epoch analysis of the ion outflow using the TEAMS (Time-of-Flight Energy Angle Mass Spectrograph) instrument on the FAST spacecraft. TEAMS measures the ion composition over the energy range of 1 eV e-1 to 12 keV e-1.  We have done major corrections and calibrations (producing 3D data set, anode calibration, mass classification, removing ram effect and incorporating dead time corrections) on TEAMS data and produced a data set for four data species (H+, O+, and He+). From 1996 to 2007, we have data for 133 orbits of CME-driven and for 103 orbits of SIR-driven sawtooth events with an altitude above 1500 km. We found that:

  • the averaged O+ outflow flux is more intense in the cusp dayside than in the nightside, before and after onset time.
  • Before onset, an intense averaged outflow flux in the dawnside of CME events is seen. This outflow decreases after onset time.
  • In both CME-driven and SIR-driven, the averaged O+ outflow increases after onset time, in the nightside, cusp dayside. This increase is greater on the nightside than in the cusp.

We will develop this study by performing a similar statistical study for H+ outflow and finally will compare the H+ result with the O+ result.

How to cite: Nowrouzi, N., Kistler, L., Lund, E., and Zhao, K.: The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13991, https://doi.org/10.5194/egusphere-egu21-13991, 2021.

EGU21-12 | vPICO presentations | ST2.4

Plasma injections arising out of dynamic ionosphere

Osuke Saka

We propose ionospheric plasma injections to the magnetosphere (ionospheric injection) as a new plasma process in the polar ionosphere. The ionospheric injection is first triggered by westward electric fields transmitted from the convection surge in the magnetosphere in association with dipolarization onset. Localized westward electric fields yield electrostatic potential in the ionosphere as a result of differing electron and ion mobility in the E-layer. To ensure quasi-neutrality of ionospheric plasmas, excess charges are released as injections out of the ionosphere, specifically electrons from positive potential region in higher latitudes and ions from negative potentials in lower latitudes. Potential difference on the order of 10 kV in north-south directions produces southward electric fields (100mv/m) at the footprint of the convection surge in both northern and southern hemispheres. Resultant geomagnetic field lines are not in equipotential equilibrium during ionospheric injections but instead develop downward electric fields in positive potential regions in higher latitudes to extract electrons and upward electric fields in negative potential regions in lower latitudes to extract ions. Parallel electric fields can exist in the magnetic mirror geometry of auroral field lines if the magnetospheric plasma follows quasi-neutral equilibrium. Because ionospheric injection has inherent dynamo processes as well as load, we term the polar ionosphere “dynamic ionosphere”.

Cold plasmas injected out of the dynamic ionosphere are transported along the dynamical trajectories to the magnetosphere conserving the total energy (including electrostatic potentials) and first adiabatic invariant. Electrons/ions traveling in downward/upward electric fields lose perpendicular and lower velocities in parallel component, leaving only the energetic part of ionospheric plasmas collimated along the field lines. Steady-state and one-dimensional dynamical trajectory shows that ion and electron temperatures at the ionosphere initially at 1 eV increased parallel temperatures to 202 eV and decreased perpendicular temperatures to 0.001 eV at geosynchronous altitudes where the electrostatic potential difference between ionosphere and magnetosphere was assumed to be 200 V. When potential difference increased to 600 V, the parallel temperatures increased to 602 eV, while perpendicular temperatures remain unchanged. Parallel potentials preferentially heated the ionospheric cold plasmas in parallel directions and transported tailward to feed the magnetosphere.

How to cite: Saka, O.: Plasma injections arising out of dynamic ionosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12, https://doi.org/10.5194/egusphere-egu21-12, 2021.

EGU21-13612 | vPICO presentations | ST2.4 | Highlight

On the Low Energy (< keV) O+ Ion Outflow directly into the Inner Magnetosphere

Matina Gkioulidou, Shin Ohtani, Don Mitchell, and Harlan Spence

The development of low energy (< keV) O+ ions in the inner magnetosphere is a crucial issue for various aspects of magnetospheric dynamics: i) Recent studies have suggested that low energy O+ can be locally accelerated to few keV energies inside geosynchronous orbit, and thus can constitute a significant source of the storm-time ring current O+ that could dominate the energy density during storms, ii) Mass loaded densities are important for accurate location of the plasmapause, which, in turn, is necessary for meaningful calculation of the field line resonance radial frequency profiles of ULF hydromagnetic waves in plasmasphere, iii) since O+ is only of ionospheric origin, its outflow from ionosphere into the magnetosphere is a manifestation of fundamental processes concerning energy and mass flow within the coupled Magnetosphere – Ionosphere system. Although a lot of progress has been made on O+ outflow at high latitudes and its subsequent transport and acceleration within the magnetotail and plasma sheet, the source of low-energy O+ within the inner magnetosphere remains a compelling open question. The Helium Oxygen Proton and Electron (HOPE) mass spectrometer instrument aboard Van Allen Probes, which move in highly elliptical, low inclination orbits with apogee of 5.8 RE, has repeatedly detected field aligned flux enhancements of eV to hundreds of eV O+ ions, which indicate O+ outflow directly into the inner magnetosphere. We systematically investigate, throughout the duration of the Van Allen Probes mission (2012 – 2019), the occurrence of such events with respect to L and MLT, the dependence of their directionality (bi-directional or unidirectional) and the lowest and highest energies involved on L, MLT and MLAT. We categorize the outflow events with respect to plasmapause location (when its determination is possible) and identify whether there is enhancement of O+ density. This categorization is important because if the outflows occur close to the plasmapause location, and depending on the density enhancement they cause, they could be responsible for the formation of O+ torus, whose source has been under debate for years. Finally, in order to identify the physical processes that lead to the ionospheric outflow, we also examine whether there are dipolarizations and/or enhancements of the field-aligned poynting flux associated with these outflow events.

How to cite: Gkioulidou, M., Ohtani, S., Mitchell, D., and Spence, H.: On the Low Energy (< keV) O+ Ion Outflow directly into the Inner Magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13612, https://doi.org/10.5194/egusphere-egu21-13612, 2021.

EGU21-15733 | vPICO presentations | ST2.4

Monitoring the plasmapause dynamics at LEO

Balázs Heilig, Claudia Stolle, Jan Rauberg, and Guram Kervalishvili

In the past decades researchers have revealed links between a series of sub-auroral ionospheric phenomena and the plasmapause (PP) dynamics, such as the mid-latitude ionospheric trough (MIT) and the associated sub-auroral temperature enhancement (SETE), the light-ion trough (LIT), the sub-auroral ion drift (SAID) or the more intense sub-auroral polarisation stream (SAPS), and most recently, the inner boundary of small-scale field-aligned currents (SSFACs). Most of these phenomena can be directly observed by the Swarm constellation of ESA at LEO. Thus, Swarm presents a unique opportunity to study the relations between them and also their relation to the PP dynamics.

In a recent Swarm DISC project, PRISM (Plasmapause Related boundaries in the topside Ionosphere as derived from Swarm Measurements), three new products have been developed. Two products characterise the MIT (and the associated SETE). The MITx_LP utilises the Langmuir probe measurements of electron density and temperature, while the MITxTEC product derives the MIT properties from GPS TEC observations. The third product, PPIxFAC provides information on the location and the main characteristics of the equatorial boundary of SSFACs, and it also includes a proxy for the location of the PP at MLT midnight.

In this presentation we introduce the above Swarm L2 products, present the results of a comparative study aiming at revealing their mutual relations and also their dynamic coupling to the PP. Then we demonstrate how the observations of all these ionospheric phenomena combined can be used to develop an improved proxy for monitoring the PP dynamics at LEO as one of the goals of our new ESA-funded project PLASMA.

How to cite: Heilig, B., Stolle, C., Rauberg, J., and Kervalishvili, G.: Monitoring the plasmapause dynamics at LEO, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15733, https://doi.org/10.5194/egusphere-egu21-15733, 2021.

EGU21-2332 | vPICO presentations | ST2.4

The spacecraft wake as a tool to detect cold ions: Turning a problem into a feature

Mats André, Anders I. Eriksson, Yuri V. Khotyaintsev, and Sergio Toledo-Redondo

Wakes behind scientific spacecraft caused by supersonic drifting ions is common in collisionless plasmas. Such wakes change the local plasma conditions and disturb in situ observations of the geophysical plasma parameters. We concentrate on observations of the electric field with double-probe instruments. Sometimes the wake effects are caused by the spacecraft body, are minor and easy to detect, and can be compensated for in a reasonable way. We show an example from the Cluster spacecraft in the solar wind. Sometimes the effects are caused by an electrostatic structure around a positively charged spacecraft causing an enhanced wake and major effects on the local plasma. Here observations of the geophysical electric field with the double-probe technique becomes impossible. Rather, the wake can be used to detect the presence of cold positive ions. Together with other instruments, also the cold ion flux can be estimated. We discuss such examples from the Cluster spacecraft in the magnetospheric lobes. For an intermediate range of parameters, when the drift energy of the ions is comparable to the equivalent charge of the spacecraft, also the charged wire booms of a double-probe instrument must be taken into account to extract useful information from the observations. We show an example from the MMS spacecraft near the magnetopause. With understanding of the physics causing wakes behind spacecraft, the local effects can sometimes be compensated for. When this is not possible, sometimes entirely new geophysical parameters can be estimated. An example is the flux of cold positive ions, constituting a major part of the mass outflow from planet Earth, using electric and magnetic field instruments on a spacecraft charged due to photoionization

 

How to cite: André, M., Eriksson, A. I., Khotyaintsev, Y. V., and Toledo-Redondo, S.: The spacecraft wake as a tool to detect cold ions: Turning a problem into a feature, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2332, https://doi.org/10.5194/egusphere-egu21-2332, 2021.

EGU21-13267 | vPICO presentations | ST2.4

On ion temperature dependence of symmetric magnetic reconnection

Ivan Zaitsev, Andrey Divin, Vladimir Semenov, Daniil Korovinskiy, Jan Deca, Yuri Khotyaintsev, and Stefano Markidis

Various simulations of collisionless magnetic reconnection reveal that the process is typically fast, with the reconnection rate being of the order of 0.1. Systematic numerical and observational studies of upstream parameters dependence (density, magnetic field) concord the basic Sweet-Parker-like predictions that the dynamical properties scale globally with the Alfven speed, with particle heating scaling as the Alfven speed squared. In this study, we perform a set of symmetric 2D PIC simulations starting from Harris current sheet but differ in upstream background plasma ion temperature. The exhaust velocity in such a setup is known to have explicit temperature dependence, leading to a reduction of the jet velocity at high temperatures. We suggest that the global reconnection rate is controlled by this outflow velocity since the reconnection electric field in the quasi-steady stage is the motional (convective) electric field of the ion bulk flow within the exhaust. Consequently, if the upstream thermal speed is above the Alfven velocity, then the reconnection rate drops. On top of that, the electron-ion temperature partition in the exhaust depends strongly on the upstream ion temperature, which we attribute to the scaling in plasma compression and development of the parallel electrostatic potential in the exhaust. 

How to cite: Zaitsev, I., Divin, A., Semenov, V., Korovinskiy, D., Deca, J., Khotyaintsev, Y., and Markidis, S.: On ion temperature dependence of symmetric magnetic reconnection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13267, https://doi.org/10.5194/egusphere-egu21-13267, 2021.

ST2.5 – Inner-magnetosphere Interactions and Coupling

EGU21-380 | vPICO presentations | ST2.5 | Highlight

Generation of two-band chorus waves in the Earth's outer radiation belt

Jinxing Li, Jacob Bortnik, Xin An, Wen Li, Vassilis Angelopoulos, and Christopher Russell

Naturally occurring chorus emissions are a class of electromagnetic waves found in the space environments of the Earth and other magnetized planets. They play an essential role in accelerating high-energy electrons forming the hazardous radiation belt environment. Chorus typically occurs in two distinct frequency bands separated by a gap. The origin of this two-band structure remains a 50-year old question. Using measurements from NASA’s Van Allen Probes we report that banded chorus waves are commonly accompanied by two separate anisotropic electron components. We demonstrate, using numerical simulations, that the initially excited single-band chorus waves alter the electron distribution immediately via Landau resonance, and suppresses the electron anisotropy at medium energies. This naturally divides the electron anisotropy into a low and a high energy components which excite the upper-band and lower-band chorus waves, respectively. This mechanism may also apply to the generation of chorus waves in other magnetized planetary magnetospheres.

How to cite: Li, J., Bortnik, J., An, X., Li, W., Angelopoulos, V., and Russell, C.: Generation of two-band chorus waves in the Earth's outer radiation belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-380, https://doi.org/10.5194/egusphere-egu21-380, 2021.

EGU21-6342 | vPICO presentations | ST2.5

Diffuse electron precipitation in magnetosphere-ionosphere-thermosphere coupling

Dong Lin, Wenbin Wang, Viacheslav Merkin, Kevin Pham, Shanshan Bao, Kareem Sorathia, Frank Toffoletto, Xueling Shi, Oppenheim Meers, George Khazanov, Adam Michael, John Lyon, Jeffrey Garretson, and Brian Anderson

Auroral precipitation plays an important role in magnetosphere-ionosphere-thermosphere (MIT) coupling by enhancing ionospheric ionization and conductivity at high latitudes. Diffuse electron precipitation refers to scattered electrons from the plasma sheet that are lost in the ionosphere. Diffuse precipitation makes the largest contribution to the total precipitation energy flux and is expected to have substantial impacts on the ionospheric conductance and affect the electrodynamic coupling between the magnetosphere and ionosphere-thermosphere. Kinetic theory and observational analysis also demonstrate that diffuse precipitation is subject to multiple reflection effects, i.e. secondary electrons produced by the primary precipitation are reflected between the north and south hemispheres multiple times before they are fully lost in the atmosphere. In this study, we make use of the newly developed Multiscale Atmosphere-Geospace Environment (MAGE) model developed at the NASA DRIVE Science Center for Geospace Storms (CGS) to explore the role of diffuse electron precipitation in MIT coupling. Diffuse precipitation in MAGE is derived from the electron distribution in the Rice Convection Model (RCM), a ring current model that solves for energy dependent drifts of electrons and ions. Diffuse precipitation, together with mono-energetic electron precipitation based on parameterization of the magnetohydrodynamic (MHD) parameters from the Grid Agnostic MHD with Extended Research Applications (GAMERA) magnetosphere model, are input to the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM) to calculate the ionospheric ionization rate and conductivity and height-integrated conductance. With controlled numerical experiments, we investigate 1. how the diffuse precipitation affects the location and structure of a mesoscale ionospheric convection process, i.e., subauroral polarization streams (SAPS); 2. How multiple reflection effects impact the ionosphere-thermosphere and their coupling with the magnetosphere. Our study demonstrates that diffuse electron precipitation plays a critical role in determining the location and structure of SAPS. The multiple reflection effects make diffuse precipitation number flux and energy flux a few times higher than the unmodified precipitation, resulting in a greatly enhanced auroral ionospheric conductance, lower cross polar cap potential,  higher total field-aligned currents, and changes in global thermospheric winds and temperature. Therefore, diffuse electron precipitation has both local and global impacts on MIT coupling.

How to cite: Lin, D., Wang, W., Merkin, V., Pham, K., Bao, S., Sorathia, K., Toffoletto, F., Shi, X., Meers, O., Khazanov, G., Michael, A., Lyon, J., Garretson, J., and Anderson, B.: Diffuse electron precipitation in magnetosphere-ionosphere-thermosphere coupling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6342, https://doi.org/10.5194/egusphere-egu21-6342, 2021.

EGU21-2071 | vPICO presentations | ST2.5 | Highlight

Thermospheric Neutral Winds: A Driver of the Earth’s Inner Radiation Belt to Be Reckoned With

Solène Lejosne, Naomi Maruyama, Richard S. Selesnick, and Mariangel Fedrizzi

Neutral winds have long been viewed as a driver of Jupiter’s radiation belts. On the other hand, the impact of thermospheric neutral winds in driving plasma dynamics in the Earth’s inner magnetosphere is yet to be quantified. We now have the appropriate combination of data and physics-based model to address this fundamental science question.

In this work, we revisit the local time asymmetry of the equatorial electron intensity observed in the innermost radiation belt (L=1.30). We combine in-situ field and particle observations, together with a physics-based coupled model, RCM-CTIPe, to determine whether the dynamo electric fields produced by tidal motion of upper atmospheric winds flowing across the Earth’s magnetic field lines are the main drivers of the drift-shell distortion observed in the Earth’s inner radiation belt.

Our results provide a first quantification of the contribution of the neutral wind in transporting the trapped energetic particles of the Earth’s inner radiation belt.

How to cite: Lejosne, S., Maruyama, N., Selesnick, R. S., and Fedrizzi, M.: Thermospheric Neutral Winds: A Driver of the Earth’s Inner Radiation Belt to Be Reckoned With, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2071, https://doi.org/10.5194/egusphere-egu21-2071, 2021.

EGU21-9315 | vPICO presentations | ST2.5

Superposed Epoch Analyses of electron-driven and proton-driven magnetic dips

Hui Zhu and Lunjin Chen

In this study, we use the Van Allen Probes data statistically to investigate the features of magnetic dips by the means of superposed epoch analysis. Based on the different max values of electron and proton plasma betas, we categorize the dips into two types: electron-driven dips and proton-driven dips. Superposed epoch analysis on two types of magnetic dips suggests the correlation between the magnetic fluctuations and plasma betas. Moreover, the occurrence of the butterfly distributions of relativistic electrons driven by the magnetic dips is confirmed by the statistical results. Our results reveal the statistical characteristics of magnetic dips and build up the relationship among the magnetic fluctuations and several parameters, indicating the potentially important role of magnetic dips in the dynamics of the inner magnetosphere.

How to cite: Zhu, H. and Chen, L.: Superposed Epoch Analyses of electron-driven and proton-driven magnetic dips, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9315, https://doi.org/10.5194/egusphere-egu21-9315, 2021.

Whistler mode chorus emissions in the Earth’s magnetosphere cause energetic electron precipitation and the associated pulsating aurora. First-order cyclotron resonance in parallel whistler mode wave-particle interactions is the main mechanism of the precipitation. Not only cyclotron resonance but also Landau resonance and higher-order cyclotron resonances occur in the oblique whistler mode wave-particle interactions. Especially, electrons can be accelerated and scattered to lower equatorial pitch angles rapidly via Landau resonance. We apply test particle simulation and the Green’s function method to check the energetic electron precipitation caused by oblique chorus emissions. We simulate the wave-particle interactions around L=4.5 for electron ranges from 10 keV to a few MeV. We further compare the precipitation fluxes between parallel and oblique chorus emissions. Our simulation result reveals that oblique chorus emissions lead to more electron precipitation than parallel chorus emissions. At kinetic energy E < 100 keV, the electron precipitation ratio (oblique case/parallel case) is about 1.3. At 100 keV < E < 0.5 MeV, the ratio is greater than 2. At E > 0.5 MeV, the ratio is greater than 2 orders. Multiple resonances effect in the oblique whistler mode wave-particle interactions is the reason for the greater precipitation.

How to cite: Hsieh, Y. and Omura, Y.: Energetic electron precipitation via oblique whistler mode chorus emissions in the outer radiation belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15306, https://doi.org/10.5194/egusphere-egu21-15306, 2021.

EGU21-6779 | vPICO presentations | ST2.5

Simulating the Effects of Lower-Energy (<30 keV) Electrons on the Inner Magnetosphere Satellite Surface Charging Environment

Yiqun Yu, Shengjun Su, Jinbin Cao, Michael Denton, and Vania Jordanova

Satellite surface charging often occurs in the inner magnetosphere from the pre-midnight to the dawn sector when electron fluxes of  hundreds of eV to tens of keV are largely enhanced. Inner magnetosphere ring current models can be used to simulate/predict the satellite surface charging environment, with their flux outer boundary conditions specified either based on observations or provided by other models, such as MHD models. In the latter approach, the flux spectrum at the outer boundary is usually assumed to follow a Kappa or Maxwellian distribution, which however often departs greatly from, or underestimates, the realistic distribution below tens of keV, the energy range that is crucial in the spacecraft surface charging anomaly. This study aims to optimize the electron flux boundary condition of the inner magnetosphere ring current model to achieve a better representation of the surface charging environment. The MHD-parameterized flux spectrum is combined with an empirical electron flux model that specifies the < 40 keV electron flux spectrum. New simulation results indicate that the surface charging environment, monitored by an integrated electron flux between 10<E<50 keV, is significantly enhanced by 1-2 orders of magnitude as opposed to the case in which Kappa/Maxwellian distribution is used at the outer boundary. The new results therefore show better agreement with Van Allen Probes measurements. The improved boundary condition also impacts the auroral precipitation, which may change the conductivity and circulated dynamics. 

How to cite: Yu, Y., Su, S., Cao, J., Denton, M., and Jordanova, V.: Simulating the Effects of Lower-Energy (<30 keV) Electrons on the Inner Magnetosphere Satellite Surface Charging Environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6779, https://doi.org/10.5194/egusphere-egu21-6779, 2021.

EGU21-532 | vPICO presentations | ST2.5

Solar wind compression induced ULF-modulation of whistler-mode waves in the deep inner magnetosphere

Xiongjun Shang, Si Liu, and Fuliang Xiao

With observations of Van Allen Probes, we report a rare event of quasiperiodic whistler-mode waves in the dayside magnetosphere on 20 February 2014 as a response to the enhancement of solar wind dynamic pressure (Psw). The intensities of whistler-mode waves and anisotropy distributions of energetic electrons exhibit a ~5 mins quasi-periodic pattern, which is consistent with the period of synchronously observed compressional ULF waves. Based on the wave growth rates calculation, we suggest that the quasiperiodic whistler-mode waves could be generated by the energetic electrons with modulated anisotropy. The Poynting vectors of the whistler-mode waves alternate between northward and southward direction with a period twice the compressional ULF wave's near the equator, also exhibiting a clear modulated feature. This is probably because the intense ULF waves slightly altered the location of the local magnetic minimum, and thus modulated the relative direction of the wave source region respect to the spacecraft. Current results provide a direct evidence that the Psw play an important role in the generation and propagation of whistler-mode waves in the Earth's magnetosphere.

How to cite: Shang, X., Liu, S., and Xiao, F.: Solar wind compression induced ULF-modulation of whistler-mode waves in the deep inner magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-532, https://doi.org/10.5194/egusphere-egu21-532, 2021.

Interplanetary (IP) shock driven sudden compression produces disturbances in the polar ionosphere. Various studies have investigated the effects of IP shock using imagers and radars. However, very few studies have reported the plasma flow reversal and a sudden vertical plasma drift motion following a CME driven IP shock. We report on the cusp ionospheric features following an IP shock impingement on 16 June 2012, using SuperDARN radar and digisonde from the Antarctic Zhongshan Station (ZHO). SuperDARN ZHO radar observed instant strong plasma flow reversal during the IP shock driven sudden impulse (SI) with a suppression in the number of backscatter echoes. Besides, we also report on a “Doppler Impulse” phenomenon, an instant and brief downward plasma motion, were observed by the digisonde in response to the SI and discuss the possible physical causes. Geomagnetic disturbance and convection patterns indicate the flow reversal was generated by the downward field-aligned current (FAC). We speculate that sudden enhancement in ionization associated with SI is responsible for generating the Doppler Impulse phenomenon.

How to cite: Liu, J.: Transient cusp ionospheric disturbances caused by a solar wind dynamic pressure enhancement, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-634, https://doi.org/10.5194/egusphere-egu21-634, 2021.

EGU21-821 | vPICO presentations | ST2.5 | Highlight

Local time and longitudinal differences in the occurrence frequency of ionospheric EMIC waves during magnetic storm periods

Hui Wang, Yangfan He, and Hermann Luehr
The spatial and temporal distributions of ionospheric electromagnetic ion cyclotron (EMIC) waves during magnetic storms from 2014 to 2018 were studied using Swarm observations. Ionospheric EMIC waves preferably occurred during storms and their recovery phases at subauroral regions within an average magnetic latitude of 40°-55°. There were more wave events during more intense and longer period storms. However, the correlation between event number and storm duration was not good. This might be due to the effect of heavy oxygen ions on EMIC wave generation and the loss of ring current high-energy ions by the EMIC waves. There are obvious magnetic local time (MLT) differences in the peak occurrence frequency of EMIC waves during storm phases. The enhanced solar wind dynamic pressure was favorable for duskside EMIC waves. With an increased substorm activity the wave occurrence rate peak shifted from the morning side to the dusk-premidnight sector. During the recovery phase of a storm, EMIC waves in the 12-24 MLT sector appeare preferably in the earlier part than those in the 00-12 MLT sector. This shift in local time is related to the eastward rotation of the plasmaspheric plume towards morning during the late storm recovery phase and its overlap with the ring current.  Highest occurrence frequency of the storm time EMIC waves could be found in the South Atlantic Anomaly region, which might be related to the drift shell splitting
and the wave propagation effect in the weak magnetic field region
.

How to cite: Wang, H., He, Y., and Luehr, H.: Local time and longitudinal differences in the occurrence frequency of ionospheric EMIC waves during magnetic storm periods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-821, https://doi.org/10.5194/egusphere-egu21-821, 2021.

EGU21-1156 | vPICO presentations | ST2.5

Storm Time EMIC Waves Observed by Swarm and Van Allen Probe Satellites

Yangfan He, Hui Wang, Lühr Hermann, Kistler Lynn, Saikin Anthony, Lund Eric, and Shuying Ma

The temporal and spatial evolution of electromagnetic ion cyclotron (EMIC) waves during
the magnetic storm of 21–29 June 2015 was investigated using high-resolution magnetic field observations
from Swarm constellation in the ionosphere and Van Allen Probes in the magnetosphere. Magnetospheric
EMIC waves had a maximum occurrence frequency in the afternoon sector and shifted equatorward during
the expansion phase and poleward during the recovery phase. However, ionospheric waves in subauroral
regions occurred more frequently in the nighttime than during the day and exhibited less obvious
latitudinal movements. During the main phase, dayside EMIC waves occurred in both the ionosphere
and magnetosphere in response to the dramatic increase in the solar wind dynamic pressure. Waves were
absent in the magnetosphere and ionosphere around the minimum SYM-H. During the early recovery
phase, He+ band EMIC waves were observed in the ionosphere and magnetosphere. During the late
recovery phase, H+ band EMIC waves emerged in response to enhanced earthward convection during
substorms in the premidnight sector. The occurrence of EMIC waves in the noon sector was affected by
the intensity of substorm activity. Both ionospheric wave frequency and power were higher in the summer
hemisphere than in the winter hemisphere. Waves were confined to an MLT interval of less than 5 hr with a
duration of less than 186 min from coordinated observations. The results could provide additional insights
into the spatial characteristics and propagation features of EMIC waves during storm periods

How to cite: He, Y., Wang, H., Hermann, L., Lynn, K., Anthony, S., Eric, L., and Ma, S.: Storm Time EMIC Waves Observed by Swarm and Van Allen Probe Satellites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1156, https://doi.org/10.5194/egusphere-egu21-1156, 2021.

EGU21-1444 | vPICO presentations | ST2.5 | Highlight

Unexpected frequency-sweep reverse of subelements in chorus rising tone

Si Liu and Zhonglei Gao

Nonlinear resonance between energetic electrons and chorus waves is widely used to explain the frequency sweep of chorus, which predicts that rising tone elements are comprised by multiple subpackets with the frequency gradually increasing. Here we report two events that subelements with their frequencies downward chirping occur in rising tone chorus. The duration of those subelements is comparable with the regular subpackets, and their frequency sweep rates 6-12 kHz/s are consistent with previous theory and observations. Waveform of the subelement shows similar morphology to regular chorus element, consisting several finer structures "hyper-subpackets". We propose a possible scenario that the falling tone subelements are formed by nonlinear process with much shorter timescale. The starting frequency of each subelement controlled by the linear growth phase increases may because the electron distribution varies fast. This study provides new insight on chorus generation and also brings challenges.

How to cite: Liu, S. and Gao, Z.: Unexpected frequency-sweep reverse of subelements in chorus rising tone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1444, https://doi.org/10.5194/egusphere-egu21-1444, 2021.

EGU21-4595 | vPICO presentations | ST2.5

Excitation of Oxygen Ion Cyclotron Harmonic Waves in the Inner Magnetosphere

Kaijun Liu, Kyungguk Min, Bolu Feng, and Yan Wang

Oxygen ion cyclotron harmonic waves, with discrete spectral peaks at multiple harmonics of the oxygen ion cyclotron frequency, have been observed in the inner magnetosphere. Their excitation mechanism has remained unclear, because the singular value decomposition (SVD) method commonly used in satellite wave data analysis suggests that the waves have quasi-parallel propagation, whereas plasma theory reveals unstable modes at nearly perpendicular propagation. Hybrid simulations are carried out to investigate the excitation of these waves. The simulation results show that waves at multiple harmonics of the oxygen ion cyclotron frequency can be excited by energetic oxygen ions of a ring-like velocity distribution. More importantly, analyzing the simulated waves in a three-dimensional simulation using the common SVD method demonstrates that, while the excited waves have quasi-perpendicular propagation, the superposition of multiple waves with different azimuthal angles causes the SVD method to yield incorrectly small wave normal angles. In addition, the scattering of oxygen ions by the excited waves is examined in the simulations. The waves can cause significant transverse heating of the relatively cool background oxygen ions, through cyclotron resonance. The waves may also scatter energetic radiation belt electrons through bounce resonance and transit time scattering, like fast magnetosonic waves.

How to cite: Liu, K., Min, K., Feng, B., and Wang, Y.: Excitation of Oxygen Ion Cyclotron Harmonic Waves in the Inner Magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4595, https://doi.org/10.5194/egusphere-egu21-4595, 2021.

Van Allen Probes observations of ion spectra often show a sustained gap within a very narrow energy range throughout the full orbit. To understand their formation mechanism, we statistically investigate the characteristics of the narrow gaps for oxygen ions and find that they are most frequently observed near the noon sector with a peak occurrence rate of over 30%. The magnetic moment (μ) of the oxygen ions in the gap shows a strong dependence on magnetic local time (MLT), with higher and lower μ in the morning and afternoon sectors, respectively. Moreover, we find through superposed epoch analysis that the gap formation also depends on geomagnetic conditions. Those gaps formed at lower magnetic moments (μ < 3000 keV/G) are associated with stable convection electric fields, which enable magnetospheric ions to follow a steady drift pattern that facilitates the gap formation by corotational drift resonance. On the other hand, gaps with higher μ values are statistically preceded by a gradual increase of geomagnetic activity. We suggest that ions within the gap were originally located inside the Alfven layer following closed drift paths, before they were transitioned into open drift paths as the convection electric field was enhanced. The sunward drift of these ions, with very low fluxes, forms a drainage void in the dayside magnetosphere manifested as the sustained gap in the oxygen spectrum. This scenario is supported by particle-tracing simulations, which reproduce most of the observed characteristics and therefore provide new insights into inner magnetospheric dynamics.

How to cite: Yue, C.: Sustained oxygen spectral gaps and their dynamic evolution in the inner magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1456, https://doi.org/10.5194/egusphere-egu21-1456, 2021.

EGU21-1492 | vPICO presentations | ST2.5

Direct Observational Evidence of the Simultaneous Excitation of Electromagnetic Ion Cyclotron Waves and Magnetosonic Waves by an Anisotropic Proton Ring Distribution

Shangchun Teng, Nigang Liu, Qianli Ma, Xin Tao, and Wen Li

Based on data from the ZH-1 satellites, companied with Van Allen Probes and NOAA observations, we analyze the high energy particle evolutions in radiation belts, slot region and SAA during August 2018 major geomagnetic storm (minimum Dst ≈ −190 nT). 

  1) Relativistic electron enhancements in extremely low L-shell regions (reaching L ∼ 3) were observed during storm. Contrary to what occurs in the outer belt, such an intense and deep electron penetration event is rare and more interesting. Strong whistler-mode (chorus and hiss) waves, with amplitudes 81–126 pT, were also observed in the extremely low L-shell simultaneously (reaching L ∼ 2.5) where the plasmapause was suppressed. The bounce-averaged diffusion coefficient calculations support that the chorus waves can play a significantly important role in diffusing and accelerating the 1–3 MeV electrons even in such low L-shells during storms.

2) A robust evidence is clearly demonstrated that the energetic electron flux with energy 30∼600 keV are increased by 2∼3 times in the inner radiation belt near equator and SAA region on dayside during the major geomagnetic storm. This is the first time that the 100s keV electron flux enhancement is reported to be potentially induced by the interaction with magnetosonic waves in extremely low L-shells (L<2) observed by Van Allen Probes. Proton loss in outer boundary of inner radiation belt takes place in energy of 2~220 MeV extensively during the occurrence of this storm but the loss mechanism is energy dependence which is consistent with some previous studies. It is confirmed that the magnetic field line curvature scattering plays a significant role in the proton loss phenomenon in energy 30-100 MeV during this storm. This work provides a beneficial help to comprehensively understand the charged particles trapping and loss in SAA region and inner radiation belt dynamic physics.

How to cite: Zhang, Z.: Electron filling and proton loss in radiation belts and SAA during 2018 storm based on ZH-1 satellite observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1529, https://doi.org/10.5194/egusphere-egu21-1529, 2021.

EGU21-2149 | vPICO presentations | ST2.5 | Highlight

Increase in seismic activity near the footprints of new radiation belts forming after geomagnetic storms

Nursultan Toyshiev, Galina Khachikyan, and Beibit Zhumabayev

Recently, attention was drawn [1] that after geomagnetic storms that cause formation of new radiation belts in slot region or in the inner magnetosphere, after about 2 months, there is an increase in seismic activity near the footprints of geomagnetic lines of new radiation belts. More detailed studies showed [2] that on May 30, 1991, an earthquake M=7.0 occurred in Alaska with (54.57N, 161.61E) near the footprint of geomagnetic line L = 2.69 belonging to new radiation belt, which was observed by the CRRES satellite [3] around geomagnetic lines 2<L<3 after geomagnetic storm on March 24, 1991. After geomagnetic storm on September 3, 2012, the Van Allen Probes satellites observed new radiation belt around 3.0≤L≤3.5 [4], and about 2 months later, on October 28, 2012, earthquake M=7.8 occurred off the coast of Canada (52.79N, 132.1W) near the footprint of geomagnetic line L=3.32 belonging to the new radiation belt. Also, Van Allen Probes observed new radiation belt around L=1.5-1.8 after geomagnetic storm on June 23, 2015 [5], and ~2 months later, in September 2015, seismic activity noticeably increased near the footprint of these geomagnetic lines. We consider variations in seismic activity in connection with the strongest geomagnetic storms in 2003 with Dst~- 400 nT (Halloween Storm) and the formation of a belt of relativistic electrons in the inner magnetosphere around L~1.5 existed until the end of 2005 as observed SAMPEX [6]. Analysis of data from the USGS global seismological catalog showed that near the footprint of geomagnetic lines L=1.4-1.6 the number of earthquakes with M≥4.5 increased in 2003-2004 by ~70% compared with their number in two previous years. On the Northern Tien Shan, on December 1, 2003 a strong for the region earthquake M=6.0 occurred on the border of Kazakhstan and China (42.9N, 80.5E) near the footprint of L = 1.63, adjacent to the new radiation belt.

How to cite: Toyshiev, N., Khachikyan, G., and Zhumabayev, B.: Increase in seismic activity near the footprints of new radiation belts forming after geomagnetic storms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2149, https://doi.org/10.5194/egusphere-egu21-2149, 2021.

Electron cyclotron harmonic (ECH) and whistler-mode chorus waves can contribute significantly to the magnetospheric dynamics. In the frequency-time spectrogram, ECH usually appears as a series of harmonic structureless bands, while chorus often exhibits successive discrete elements. Here, we present surprising observations by Van Allen Probes of lag-correlated rising tones of ECH and upper-band chorus waves. The time lags of ECH elements with respect to chorus elements range from 0.05 to 0.28 s, negatively correlated with the chorus peak amplitudes. The ECH elements seemingly emerge only when the chorus elements are sufficiently intense (peak amplitude >3 mV/m), and their peak amplitudes are positively correlated. Our data and modeling suggest that upper-band chorus may promote the generation of ECH through rapidly precipitating the ~keV electrons near the loss cone. This phenomenon implies that ECH and chorus may not grow independently but competitively or collaboratively gain energy from hot electrons.

How to cite: Gao, Z.: Lag-correlated rising tones of electron cyclotron harmonic and whistler-mode upper-band chorus waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2459, https://doi.org/10.5194/egusphere-egu21-2459, 2021.

EGU21-2775 | vPICO presentations | ST2.5

Quasiperiodic emissions and related particle precipitation bursts observed by the DEMETER spacecraft

Frantisek Nemec, Mychajlo Hajoš, Barbora Bezděková, Ondřej Santolík, and Michel Parrot

Electromagnetic waves observed in the inner magnetosphere at frequencies between about 0.5 and 4 kHz sometimes exhibit a quasiperiodic (QP) time modulation of the wave intensity with modulation periods from tens of seconds up to a few minutes. Such waves are typically termed “QP emissions” and their origin is still not fully understood. We use a large set of more than 2,000 of these events identified in the low-altitude DEMETER spacecraft data to analyze how the wave properties (modulation period, intensity) depend on relevant controlling factors. Moreover, in-situ measurements of energetic electron precipitation are used to check for precipitation peaks matching the individual QP elements. We successfully identified several such events and we perform their detailed analysis. Most importantly, while the waves may propagate unducted across L-shells, the precipitating particles follow magnetic field lines from the interaction region down to the observation point. They can thus be used to deduce important information about the location and spatial extent of the anticipated generation region of the emissions.

How to cite: Nemec, F., Hajoš, M., Bezděková, B., Santolík, O., and Parrot, M.: Quasiperiodic emissions and related particle precipitation bursts observed by the DEMETER spacecraft, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2775, https://doi.org/10.5194/egusphere-egu21-2775, 2021.

EGU21-2805 | vPICO presentations | ST2.5

Variations of VLF Wave Intensity Analyzed via Principal Component Analysis

Barbora Bezděková, František Němec, Michel Parrot, Jyrki Manninen, Oksana Krupařová, and Vratislav Krupař

Wave intensity measured in the very low frequency (VLF) range (up to 20 kHz) is typically represented using frequency-time spectrograms. Since the characterization of spectrogram main features and/or their direct comparison is a challenging task, we transform the measurements of the low-altitude DEMETER spacecraft using the principal component analysis (PCA). The present study is focused on both the physical interpretation of the first two principal components and their application to real physical problems. To understand the physical meaning of the first principal components, their scatter plot is constructed and discussed. Moreover, the dependence of the first principal component (PC1) coefficients on the geomagnetic activity and their seasonal/longitudinal variations are analyzed. The obtained distributions are well comparable with those obtained by previous studies for average wave intensities, indicating that the PC1 coefficients are directly related to the overall wave intensity. Furthermore, the variations of PC1 coefficients around interplanetary (IP) shock arrivals are analyzed, suggesting that the fast forward shock occurrence has the most significant effect. It is shown that the wave intensity variations depend on the wave intensity detected before the shock arrival. The shock strength and interplanetary magnetic field orientation are also important. To further demonstrate the adaptability of PCA, we use a similar method to analyze also ground-based VLF measurements performed by the Kannuslehto station located in northern Finland.

How to cite: Bezděková, B., Němec, F., Parrot, M., Manninen, J., Krupařová, O., and Krupař, V.: Variations of VLF Wave Intensity Analyzed via Principal Component Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2805, https://doi.org/10.5194/egusphere-egu21-2805, 2021.

EGU21-8779 | vPICO presentations | ST2.5

The Formation of Saturn’s and Jupiter’s Electron Radiation Belts by Magnetospheric Electric Fields

Yixin Hao, Yixin Sun, Elias Roussos, Ying Liu, Peter Kollmann, Chongjing Yuan, Norbert Krupp, Chris Paranicas, Xuzhi Zhou, Go Murakami, Hajime Kita, and Qiugang Zong

The existence of planetary radiation belts with relativistic electron components means that powerful acceleration mechanisms are operating within their volume. Mechanisms that bring charged particles planetward toward stronger magnetic fields can cause their heating. On the basis that electron fluxes in Saturn’s radiation belts are enhanced over discrete energy intervals, previous studies have suggested that rapid inward plasma flows may be controlling the production of their most energetic electrons. However, rapid plasma inflows languish in the planet’s inner magnetosphere, and they are not spatially appealing as a mechanism to form the belts. Here we show that slow, global-scale flows resulting from transient noon-to-midnight electric fields successfully explain the discretized flux spectra at quasi- and fully relativistic energies, and that they are ultimately responsible for the bulk of the highest energy electrons trapped at Saturn. This finding is surprising, given that plasma flows at Saturn are dominated by the planetary rotation; these weak electric field perturbations were previously considered impactful only over a very narrow electron energy range where the magnetic drifts of electrons cancel out with corotation. We also find quantitative evidence that ultrarelativistic electrons in Jupiterʼs radiation belts are accelerated by the same mechanism. Given that similar processes at Earth drive a less efficient electron transport compared to Saturn and Jupiter, the conclusion is emerging that global-scale electric fields can provide powerful relativistic electron acceleration, especially at strongly magnetized and fast-rotating astrophysical objects.

How to cite: Hao, Y., Sun, Y., Roussos, E., Liu, Y., Kollmann, P., Yuan, C., Krupp, N., Paranicas, C., Zhou, X., Murakami, G., Kita, H., and Zong, Q.: The Formation of Saturn’s and Jupiter’s Electron Radiation Belts by Magnetospheric Electric Fields, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8779, https://doi.org/10.5194/egusphere-egu21-8779, 2021.

EGU21-3120 | vPICO presentations | ST2.5 | Highlight

Acceleration and Loss of Ultra-relativistic Electrons in the Earth Van Allen Radiation Belts

Yuri Shprits, Hayley Allison, Alexander Drozdov, Dedong Wang, Nikita Aseev, Irina Zhelavskaya, and Maria Usanova

Measurements from the Van Allen Probes mission clearly demonstrated that the radiation belts cannot be considered as a bulk population above approximately electron rest mass. Ultra-relativistic electrons (~>4Mev) form a new population that shows a very different morphology (e.g. very narrow remnant belts) and slow but sporadic acceleration.

We show that acceleration to multi-MeV energies can not only result of a two-step processes consisting of local heating and radial diffusion but occurs locally due to energy diffusion by whistler mode waves. Local heating appears to be able to transport electrons in energy space from 100s of keV all the way to ultra-relativistic energies (>7MeV). Acceleration to such high energies occurs only for the conditions when cold plasma in the trough region is extremely depleted down to the values typical for the plasma sheet.

There is also a clear difference between the loss mechanisms at MeV and multi MeV energies The difference between the loss mechanisms at MeV and multi-MeV energies is due to EMIC waves that can very efficiently scatter ultra-relativistic electrons, but leave MeV electrons unaffected.

We also present how the new understanding gained from the Van Allen Probes mission can be used to produce the most accurate data assimilative forecast. Under the recently funded EU Horizon 2020 Project Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER) we will study how ensemble forecasting from the Sun can produce long-term probabilistic forecasts of the radiation environment in the inner magnetosphere.

How to cite: Shprits, Y., Allison, H., Drozdov, A., Wang, D., Aseev, N., Zhelavskaya, I., and Usanova, M.: Acceleration and Loss of Ultra-relativistic Electrons in the Earth Van Allen Radiation Belts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3120, https://doi.org/10.5194/egusphere-egu21-3120, 2021.

EGU21-3802 | vPICO presentations | ST2.5

Simulations of the Relativistic Radiation Belt Electrons Using the VERB-3D Code

Dedong Wang, Yuri Shprits, Alexander Drozdov, Nikita Aseev, Irina Zhelavskaya, Angelica Castillo, Hayley Allison, Sebastian Cervantes, and Frederic Effenberger

Using the three-dimensional Versatile Electron Radiation Belt (VERB-3D) code, we perform simulations to investigate the dynamic evolution of relativistic electrons in the Earth’s outer radiation belt. In our simulations, we use data from the Geostationary Operational Environmental Satellites (GOES) to set up the outer boundary condition, which is the only data input for simulations. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high $L^*$. We validate our simulation results against measurements from Van Allen Probes. In long-term simulations, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high‐latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high‐latitude waves can result in a net loss of MeV electrons. Variations in high‐latitude chorus may account for some of the variability of MeV electrons. 

Our simulation results for the NSF GEM Challenge Events show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. We also perform simulations for the COSPAR International Space Weather Action Team (ISWAT) Challenge for the year 2017. The COSPAR ISWAT is a global hub for collaborations addressing challenges across the field of space weather. One of the objectives of the G3-04 team “Internal Charging Effects and the Relevant Space Environment” is model performance assessment and improvement. One of the expected outputs is a more systematic assessment of model performance under different conditions. The G3-04 team proposed performing benchmarking challenge runs. We ‘fly’ a virtual satellite through our simulation results and compare the simulated differential electron fluxes at 0.9 MeV and 57.27 degrees local pitch-angle with the fluxes measured by the Van Allen Probes. In general, our simulation results show good agreement with observations. We calculated several different matrices to validate our simulation results against satellite observations.

How to cite: Wang, D., Shprits, Y., Drozdov, A., Aseev, N., Zhelavskaya, I., Castillo, A., Allison, H., Cervantes, S., and Effenberger, F.: Simulations of the Relativistic Radiation Belt Electrons Using the VERB-3D Code, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3802, https://doi.org/10.5194/egusphere-egu21-3802, 2021.

EGU21-12763 | vPICO presentations | ST2.5

Statistical EMIC diffusion models calculated by averaging observation specific diffusion coefficients

Johnathan Ross, Sarah Glauert, Richard Horne, Nigel Meredith, and Clare Watt

Electromagnetic ion cyclotron (EMIC) waves play an important role in relativistic electron losses in the radiation belts through diffusion via resonant wave-particle interactions. We present a new statistical model of electron diffusion by EMIC waves calculated, using Van Allen Probe observations, by averaging observation specific diffusion coefficients. The resulting diffusion coefficients therefore capture a wider range of wave-particle interactions than previous average models which are calculated using average observations. These calculations, and their role in radiation belt simulations, are then compared against existing diffusion models. The new diffusion coefficients are found to significantly improve the agreement between the calculated decay of relativistic electrons and Van Allen Probes data.

 

How to cite: Ross, J., Glauert, S., Horne, R., Meredith, N., and Watt, C.: Statistical EMIC diffusion models calculated by averaging observation specific diffusion coefficients, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12763, https://doi.org/10.5194/egusphere-egu21-12763, 2021.

Large-amplitude electromagnetic ion cyclotron (EMIC) waves induce unique dynamics of charged particle movement in the magnetosphere. In a recent study, modulation of the ion pitch angle in the presence of large-amplitude EMIC waves is observed, and there lacks a good explanation for this phenomenon. We investigate this modulation primarily via a 1-D hybrid simulation model and find that the modulation is caused by the bulk velocity triggered by large-amplitude EMIC waves. Affected by the bulk velocity, the number density of ions will enhance around pitch angle . Beyond that, the ion pitch angle is also modulated by the EMIC waves, and the modulation period is half of the EMIC waves' period. In addition, parameters that affect ion pitch angle modulation, including the wave amplitude, ion energy, ion species, and wave normal angle, are studied in our work.

How to cite: Ti, S., Chen, T., and Yao, J.: Modulation of Ion Pitch Angle in the Presence of Large-amplitude, Electromagnetic Ion Cyclotron (EMIC) Waves: 1-D Hybrid Simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5211, https://doi.org/10.5194/egusphere-egu21-5211, 2021.

EGU21-6003 | vPICO presentations | ST2.5

Statistical Distribution of Bifurcation of Earth's Inner Energetic Electron Belt at tens of keV

Man Hua, Binbin Ni, Wen Li, Qianli Ma, Xudong Gu, Song Fu, Xing Cao, Yingjie Guo, and Yangxizi Liu

The Earth’s inner energetic electron belt typically exhibits one-peak radial structure with high flux intensities at radial distances < ~2.5 Earth radii. Recent studies suggested that human-made very-low-frequency (VLF) transmitters leaked into the inner magnetosphere can efficiently scatter energetic electrons, bifurcating the inner electron belt. In this study, we use 6-year electron flux data from Van Allen Probes to comprehensively analyze the statistical distributions of the bifurcated inner electron belt and their dependence on electron energy, season, and geomagnetic activity, which is crucial to understand when and where VLF transmitters can efficiently scatter electrons in addition to other naturally occurring waves. We reveal that bifurcation can be frequently observed for tens of keV electrons under relatively quiet geomagnetic conditions, typically after significant flux enhancements that elevate fluxes at L = 2.0 – ~2.5 providing the prerequisite for the bifurcation. The bifurcation typically lasts for a few days until interrupted by substorm injections or inward radial diffusion. The L-shells of bifurcation dip decrease with increasing electron energy, and the occurrence of bifurcation is higher during northern hemisphere winter than summer, supporting the important role of VLF transmitter waves in energetic electron loss in near-Earth space.

How to cite: Hua, M., Ni, B., Li, W., Ma, Q., Gu, X., Fu, S., Cao, X., Guo, Y., and Liu, Y.: Statistical Distribution of Bifurcation of Earth's Inner Energetic Electron Belt at tens of keV, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6003, https://doi.org/10.5194/egusphere-egu21-6003, 2021.

EGU21-6074 | vPICO presentations | ST2.5 | Highlight

The nature of the variability of wave particle interactions in the inner magnetosphere and consequences for diffusion models

Clare Watt, Hayley Allison, Rhys Thompson, Sarah Bentley, Jonathan Rae, Nigel Meredith, Sarah Glauert, RIchard Horne, Shuai Zhang, Alex Degeling, Anmin Tian, and Quanqi Shi

It is important to understand the variability of plasma processes across many different timescales in order to successfully model plasma in the inner magnetosphere. In this presentation, we focus on the interplay between the variability cold plasmaspheric plasma, whistler-mode wave activity, and the efficacy of wave-particle interactions in the inner magnetosphere. We use in-situ observations to quantify the amount and timescales of variability in pitch-angle diffusion due to plasmaspheric hiss in Earth’s inner magnetosphere, and suggest reasons for the variability. We then use a stochastic parameterization scheme to investigate the consequences of that variability in a numerical diffusion model. The results from the stochastic parameterization are contrasted with the standard approach of constructing averaged diffusion coefficients. We demonstrate that even when the average diffusion rates are the same, different timescales of variability in the wave-particle interactions lead to different end results in numerical diffusion models. We discuss the implications of our results for the modelling of wave-particle interactions in magnetospheres, and suggest quantifications that are vital for accurate modelling.

How to cite: Watt, C., Allison, H., Thompson, R., Bentley, S., Rae, J., Meredith, N., Glauert, S., Horne, R., Zhang, S., Degeling, A., Tian, A., and Shi, Q.: The nature of the variability of wave particle interactions in the inner magnetosphere and consequences for diffusion models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6074, https://doi.org/10.5194/egusphere-egu21-6074, 2021.

EGU21-10735 | vPICO presentations | ST2.5 | Highlight

Variability of natural whistler-mode emissions in the inner magnetosphere

Ondrej Santolik, William S. Kurth, and Craig A. Kletzing

Whistler-mode electromagnetic waves, especially natural emissions of chorus and hiss, have been shown to transfer energy between different electron populations in the inner magnetosphere via quasi-linear or nonlinear wave particle interactions. Average or median intensities of chorus and hiss emissions have been found to increase with increasing levels of geomagnetic activity but their stochastic variations in individual spacecraft measurements at the same location are usually comparable to these large-scale temporal effects. Statistical properties of variations of wave power directly influence results of quasi-linear diffusion models.

We use the survey measurements of the Waves instruments of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard two Van Allen Probes to asses the probability distribution function of these stochastic variations. We take advantage of the entire data set of these measurements with a nearly 100% coverage from August 31, 2012 till October 13, 2019 (2600 days) for spacecraft A, and from  September 1, 2012 till July 16, 2019 (2510 days) for spacecraft B. 

How to cite: Santolik, O., Kurth, W. S., and Kletzing, C. A.: Variability of natural whistler-mode emissions in the inner magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10735, https://doi.org/10.5194/egusphere-egu21-10735, 2021.

Chorus waves with extremely low frequency (ELF) below 0.1 fce are proposed to be a potential mechanism of scattering losses of relativistic electrons in the radiation belt. However, the generation of ELF chorus is still an open question. Here we report three interesting events that the occurrence of ELF chorus waves shows evident correlation with the increase of background plasma density while the disturbance of ambient magnetic field is negligible. We calculate the growth rate of chorus waves by using the correlated data of waves and particles form the Van Allen Probes. The calculated growth rates agree well with the wave along the satellite orbit. The current study suggests that the plasma density may play an important role on controlling the wave frequency during the chorus generation process.

How to cite: He, Q. and Liu, S.: The generatin of extremely low-frequency chorus waves associated with plasma density enhancement, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7748, https://doi.org/10.5194/egusphere-egu21-7748, 2021.

We investigate the statistical distribution of energetic electron precipitation from the equatorial magnetosphere due to hiss waves in the plasmasphere and plumes. Using Van Allen Probes measurements, we calculate the pitch angle diffusion coefficients at the pitch angle of bounce loss cone, and evaluate the energy spectrum of precipitating electron flux using quasi-linear theory. Our ~6.5 years survey shows that, during disturbed times, the plasmaspheric hiss mostly causes the electron precipitation at L > 3 near the dayside in the plasmasphere, and hiss waves in plume cause the precipitation at L > 5 near dayside and L > 3.5 near the dusk side. The precipitating energy flux increases with increasing geomagnetic index, and is typically higher in the plasmaspheric plume than the plasmasphere. The characteristic energy of precipitation increases from ~20 keV at L = 6 to ~100 keV at L = 3, potentially causing the loss of electrons at several hundred keV. Although the total precipitating energy flux due to hiss waves is generally lower than the precipitation due to whistler mode chorus waves, the characteristic energy of precipitation due to hiss is higher, and the precipitation extends closer to the Earth.

How to cite: Ma, Q.: Statistical Distribution of Energetic Electron Precipitation due to Hiss Waves In the Earth’s Inner Magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9131, https://doi.org/10.5194/egusphere-egu21-9131, 2021.

EGU21-13458 | vPICO presentations | ST2.5

On the semi-annual variation of relativistic electrons in the outer radiation belt

Sigiava Aminalragia-Giamini, Christos Katsavrias, Constantinos Papadimitriou, Ioannis A. Daglis, Ingmar Sandberg, and Piers Jiggens

The nature of the semi-annual variation in the relativistic electron fluxes in the Earth’s outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and GOES (EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship with the axial, equinoctial and Russell-McPherron mechanisms. It is found that the semi-annual variation in the relativistic electron fluxes exhibits pronounced power in the 0.3 – 4.2 MeV energy range at L-shells higher than 3.5 and, moreover, it exhibits an in-phase relationship with the Russell-McPherron effect indicating the former is primarily driven by the latter. Furthermore, the analysis of the past 3 solar cycles with GOES/EPS indicates that the semi-annual variation at geosynchronous orbit is evident during the descending phases and coincides with periods of a higher (lower) HSS (ICME) occurrence.

This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437 and from the European Space Agency under the “European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System” activity under ESA Contract No 4000127282/19/NL/IB/gg.

How to cite: Aminalragia-Giamini, S., Katsavrias, C., Papadimitriou, C., A. Daglis, I., Sandberg, I., and Jiggens, P.: On the semi-annual variation of relativistic electrons in the outer radiation belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13458, https://doi.org/10.5194/egusphere-egu21-13458, 2021.

ST3.1 – Open Session on Ionosphere and Thermosphere

EGU21-5986 | vPICO presentations | ST3.1 | Highlight

Large-scale dune aurora event investigation combining Citizen Scientists' photographs and spacecraft observations

Maxime Grandin, Minna Palmroth, Graeme Whipps, Milla Kalliokoski, Mark Ferrier, Larry J. Paxton, Martin G. Mlynczak, Jukka Hilska, Knut Holmseth, Kjetil Vinorum, and Barry Whenman

Recently, citizen scientist photographs led to the discovery of a new auroral form called "the dune aurora" which exhibits parallel stripes of brighter emission in the green diffuse aurora at about 100 km altitude. This discovery raised several questions, such as (i) whether the dunes are associated with particle precipitation, (ii) whether their structure arises from spatial inhomogeneities in the precipitating fluxes or in the underlying neutral atmosphere, and (iii) whether they are the auroral manifestation of an atmospheric wave called a mesospheric bore. This study investigates a large-scale dune aurora event on 20 January 2016 above Northern Europe. The dunes were observed from Finland to Scotland, spanning over 1500 km for at least four hours. Spacecraft observations confirm that the dunes are associated with electron precipitation and reveal the presence of a temperature inversion layer below the mesopause during the event, creating suitable conditions for mesospheric bore formation. The analysis of a time lapse of pictures by a citizen scientist from Scotland leads to the estimate that, during this event, the dunes propagate toward the west-southwest direction at about 200 m/s, presumably indicating strong horizontal winds near the mesopause. These results show that citizen science and dune aurora studies can fill observational gaps and be powerful tools to investigate the least-known region of near-Earth space at altitudes near 100 km.

How to cite: Grandin, M., Palmroth, M., Whipps, G., Kalliokoski, M., Ferrier, M., Paxton, L. J., Mlynczak, M. G., Hilska, J., Holmseth, K., Vinorum, K., and Whenman, B.: Large-scale dune aurora event investigation combining Citizen Scientists' photographs and spacecraft observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5986, https://doi.org/10.5194/egusphere-egu21-5986, 2021.

EGU21-4130 | vPICO presentations | ST3.1

Westward travelling surge driven by the polar cap flow channels

Yuzhang Ma, Qing-He Zhang, Larry R. Lyons, Jiang Liu, Zan-Yang Xing, Ashton Reimer, Yukitoshi Nishimura, and Don Hanpton

Following substorm auroral onset, the active aurora region usually expands poleward toward the poleward auroral boundary. Such poleward expansion is often associated with a bulge region that expands westward and forms the westward travelling surge (WTS). In this paper we show all-sky imager and Poker Flat Advanced Modular Incoherent Scatter Radar (PFISR) radar observations of two surge events to investigate the relationship between the surge and flow from the polar cap. For both events, we observe auroral streamers, with an adjacent flow channel consisting of decreased density and cool electron temperature plasma flowing equatorward. This flow channel appears to impinge and lead/feed surge formation, and to stay connected to the surge as it moves westward. Also, for both events, streamer observations indicate that, following initial surge development, similar flows led to explosive surge enhancements. The observation that the streamers connected to the auroral polar boundary and that the flow channels consisted of low density, low electron temperature plasma indicates that the impinging plasma came from the polar cap. For both events, the altitude variations of F region plasma within the surges are related with aurora emission and the poleward/equatorward flow, and the surges develop strong auroral streamers that initiate along the poleward auroral boundary when contacted with flow from the polar cap. These results suggest that the polar cap flow channels play a crucial role in auroral surges by feeding low entropy plasma into surge initiation and development, and also playing an important role in the dynamics within a surge.

How to cite: Ma, Y., Zhang, Q.-H., Lyons, L. R., Liu, J., Xing, Z.-Y., Reimer, A., Nishimura, Y., and Hanpton, D.: Westward travelling surge driven by the polar cap flow channels, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4130, https://doi.org/10.5194/egusphere-egu21-4130, 2021.

EGU21-8530 | vPICO presentations | ST3.1

Detection of geomagnetic disturbances with ionospheric calibration solutions of LOFAR astronomical observations

Katarzyna Budzińska, Maaijke Mevius, Marcin Grzesiak, Mariusz Pożoga, Barbara Matyjasiak, and Hanna Rothkaehl

Perturbation of an electromagnetic signal due to its passing through the Earth’s ionosphere is one of the limiting factors in obtaining high quality astronomical observations at low frequencies. Since the establishment of the Low Frequency Array (LOFAR) radio interferometer, which is operating  in the frequency range between 10  and 240 MHz, effort has been made in order to properly remove this effect during the calibration routine.

In this study we use differential TEC solutions obtained from calibration of Epoch of Reionization project’s observations and investigate their sensitivity to weak geomagnetic disturbances with wavelet transform analysis. Comparison to the different geomagnetic indices allows us to study the possible origin of medium scale ionospheric structures that have been detected.

How to cite: Budzińska, K., Mevius, M., Grzesiak, M., Pożoga, M., Matyjasiak, B., and Rothkaehl, H.: Detection of geomagnetic disturbances with ionospheric calibration solutions of LOFAR astronomical observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8530, https://doi.org/10.5194/egusphere-egu21-8530, 2021.

EGU21-7293 | vPICO presentations | ST3.1

Ionospheric plasma irregularities inside the mid-latitude trough by using Swarm observations

Yiwen Liu, Chao Xiong, and Xin Wan

The mid-latitude ionospheric trough (MIT) is a well-known feature in the topside ionosphere and plasmasphere. In this report, we investigated the plasma irregularities inside the MIT region based on the high-resolution (2 Hz) measurements of electron density and temperature from the Swarm satellite. We developed a method to automatically identify the mid-latitude trough from Swarm in-situ density measurements, and the small-scale irregularities inside MIT region can also be well determined by considering appropriate thresholds of both the relative (∆Ne/Ne) and absolute (∆Ne) density fluctuations. Further statistics has been performed based-on the multi-years database of identified MITs and irregularities from Swarm. Finally, we provided for the first time the seasonal and magnetic local time distributions of irregularities within the MIT region, and the involved plasma instabilities that cause the irregularities at the MIT region have been discussed.

How to cite: Liu, Y., Xiong, C., and Wan, X.: Ionospheric plasma irregularities inside the mid-latitude trough by using Swarm observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7293, https://doi.org/10.5194/egusphere-egu21-7293, 2021.

EGU21-6457 | vPICO presentations | ST3.1

Solar activity and its impact on the mid-latitude trough during geomagnetic storms

Dorota Przepiórka, Barbara Matyjasiak, Agata Chuchra, and Hanna Rothkaehl

Mid-latitude trough (MIT) is the distinct structure observed in Earth’s ionosphere at high latitudes especially at the nighttimes. The phenomenon is observed at both hemispheres. As it resides at the topside ionosphere in the sub-auroral region, its behaviour and properties are highly sensitive to the solar and geomagnetic activity. Generally as the geomagnetic activity is more pronounced the MIT is observed at lower latitudes, it also deepens and becomes much more distinct in comparison to the low magnetic activity periods. MIT responds as well to the rapid changes in geomagnetic conditions, as are the geomagnetic storms, mainly caused by the CMEs. 

Based on the observations gathered by DEMETER data between 2005 and 2010 years  we present a set of geomagnetic storm cases and how the MIT properties has been changing as the storm evolves. We also discuss how it corresponds to the current solar activity and their evolutionary history  described by a set of different parameters.

How to cite: Przepiórka, D., Matyjasiak, B., Chuchra, A., and Rothkaehl, H.: Solar activity and its impact on the mid-latitude trough during geomagnetic storms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6457, https://doi.org/10.5194/egusphere-egu21-6457, 2021.

EGU21-6764 | vPICO presentations | ST3.1

Low and middle latitude thermosphere and ionosphere responses to geomagnetic activity

Wenbin Wang, Qian Wu, and Dong Ling

Solar wind and its embedded interplanetary magnetic field (IMF) affects Earth’s upper atmosphere by changing high-latitude ionospheric convection patter, producing auroral precipitation and depositing energy and momentum at high latitudes. These processes are greatly enhanced during geomagnetically active periods.  The geomagnetic activity induced changes at high latitudes are then transmitted to middle and low latitudes. In this work we employ the recently developed Multiscale Atmosphere-Geospace Environment (MAGE) model to simulate the non-linear electrodynamic and dynamic processes by which solar wind and IMF affect low and middle latitude thermosphere and ionosphere during geomagnetically active periods, including the stream interaction region event that happened in September 2020.  We examine the changes in ionospheric electric fields caused by penetration electric fields and neutral wind dynamo, as well as changes in neutral winds, temperature, composition  and ionospheric plasma densities. Model results are compared with  data from recent satellite mission, including COSMIC 2, GOLD and ICON to obtain new insight in the physical processes in the global thermosphere ionosphere responses to disturbed solar wind and IMF driving conditions.

How to cite: Wang, W., Wu, Q., and Ling, D.: Low and middle latitude thermosphere and ionosphere responses to geomagnetic activity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6764, https://doi.org/10.5194/egusphere-egu21-6764, 2021.

EGU21-802 | vPICO presentations | ST3.1

Dynamics of the tongue of ionizations during the geomagnetic storm on September 7, 2015

Kedeng Zhang, Hui Wang, Jing Liu, Zhichao Zheng, Yangfan He, Jie Gao, Luyuan Sun, and Yunfang Zheng

The dynamic evolution of the double tongue of ionization (TOI) into a single TOI at 400 km during the geomagnetic storm on September 7, 2015 was studied using the Defense Meteorological Satellite Program observations and Thermosphere Ionosphere Electrodynamic General Circulation model simulations. The double TOIs occurred in the presence of increased southward Bz and weak positive By, while the single TOI occurred in the presence of northward turning of Bz and duskward turning of By. In both double and single TOI events, the plasma at middle latitudes in the afternoon (prenoon) sector was greatly enhanced due to the local upward (upward) and zonal (meridional) E × B. The transition process is due to both the northward and duskward turning of IMF. The northward turning of IMF Bz weakens the SED and the TOI in both afternoon and morning sectors, while the increasing duskward IMF By strengthens the morning TOI.

How to cite: Zhang, K., Wang, H., Liu, J., Zheng, Z., He, Y., Gao, J., Sun, L., and Zheng, Y.: Dynamics of the tongue of ionizations during the geomagnetic storm on September 7, 2015, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-802, https://doi.org/10.5194/egusphere-egu21-802, 2021.

During the geomagnetic storm on 8~9 September 2017, a new kind of ionospheric irregularity is persistently captured in lower-middle latitudes at multiple local times, based on Swarm and DMSP satellites observations. This irregularity is observed as the conjugate strip-like bulge, which extends larger than 150° in longitude but only 1°~5° in latitude. The strip-like bulges can be categorized into sharp and blunt types depending on the sharpness of the density peaks. The blunt type is short-lived and appears earlier than the sharp type in the afternoon-sunset sector. The sharp type is long-lived and appears at all the observed local times. Both two types of strip-like bulges are dominated by the ion composition of the H+ /He+. This is the first evidence that the plasmaspheric particles are involved in forming the ionospheric structure at such low latitude. Moreover, the latitude/L-shell of the bulges decreased synchronously with the plasmaspheric compression. Also, these two types of strip-like bulges show different longitudinal dependencies controlled by the magnetic declination. We suggest that the combined effect from the plasmaspheric downwelling and disturbance neutral wind is responsible for the appearance of the strip-like bulges.

How to cite: Wan, X., Zhong, J., and Xiong, C.: Strip-like plasma bulges at lower-middle latitudes over a wide range of longitude during 8~9 September 2017 geomagnetic storm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2125, https://doi.org/10.5194/egusphere-egu21-2125, 2021.

EGU21-4611 | vPICO presentations | ST3.1

Differences in regular and storm time ionospheric variability at magnetically conjugated locations of the Northern and Southern Hemisphere 

Dalia Buresova, John Bosco Habarulema, Eduardo Araujo-Pradere, Mpho Tshisaphungo, Jurgen Watermann, and Jan Lastovicka

The paper is focused on differences/similarities in regular daily ionospheric variability and in the ionospheric response to CME- and CIR/CHSS-related magnetic disturbances above magnetically conjugated ionospheric stations located at Northern and Southern Hemisphere. We analysed variability of critical frequency foF2 and the F2 layer peak height hmF2 obtained for European-African sector for initial, main and recovery phases of magnetic storms of different intensity, which occurred within the last two solar cycles. We also used exclusively GPS-based detection methods, specifically information on TEC, TEC deviations in space and time from a background reference (dTEC), and the Rate of TEC change in time (ROT), all inferred from GPS receiver networks in Europe and Africa to compare behavior of Large Scale Traveling Ionospheric Disturbances (LSTIDs) at both hemispheres. We conclude that hemispheric conjugacy of LSTID is highly probable during both CME- and CIR/CHSS-related storms while interhemispheric circulation rather unlikely but still occurring during some periods.

How to cite: Buresova, D., Habarulema, J. B., Araujo-Pradere, E., Tshisaphungo, M., Watermann, J., and Lastovicka, J.: Differences in regular and storm time ionospheric variability at magnetically conjugated locations of the Northern and Southern Hemisphere , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4611, https://doi.org/10.5194/egusphere-egu21-4611, 2021.

EGU21-12569 | vPICO presentations | ST3.1

Statistical estimates of auroral Pedersen conductance using electric and magnetic measurements by the Swarm spacecraft

Heikki Vanhamäki, Anita Aikio, Kirsti Kauristie, Sebastian Käki, and David Knudsen

Height-integrated ionospheric Pedersen and Hall conductances play a major role in ionospheric electrodynamics and Magnetosphere-Ionosphere coupling. Especially the Pedersen conductance is a crucial parameter in estimating ionospheric energy dissipation via Joule heating. Unfortunately, the conductances are rather difficult to measure directly in extended regions, so statistical models and various proxies are often used.

We discuss a method for estimating the Pedersen Conductance from magnetic and electric field data provided by the Swarm satellites. We need to assume that the height-integrated Pedersen current is identical to the curl-free part of the height integrated ionospheric horizontal current density, which is strictly valid only if the conductance gradients are parallel to the electric field. This may not be a valid assumption in individual cases but could be a good approximation in a statistical sense. Further assuming that the cross-track magnetic disturbance measured by Swarm is mostly produced by field-aligned currents and not affected by ionospheric electrojets, we can use the cross-track ion velocity and the magnetic perturbation to directly estimate the height-integrated Pedersen conductance.

We present initial results of a statistical study utilizing 5 years of data from the Swarm-A and Swarm-B spacecraft, and discuss possible applications of the results and limitations of the method.

How to cite: Vanhamäki, H., Aikio, A., Kauristie, K., Käki, S., and Knudsen, D.: Statistical estimates of auroral Pedersen conductance using electric and magnetic measurements by the Swarm spacecraft, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12569, https://doi.org/10.5194/egusphere-egu21-12569, 2021.

EGU21-1389 | vPICO presentations | ST3.1

Large scale thermospheric density enhancements in relation to downward Poynting fluxes: Statistics from CHAMP, AMPERE and SuperDARN

Daniel Billett, Gareth Perry, Lasse Clausen, William Archer, Kathryn McWilliams, Stein Haaland, and Johnathan Burchill

Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The CHAMP satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists on statistical timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine-scale Poynting fluxes are associated with the density perturbations on a case-by-case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically.

In this study, we use nearly 8 years of the overlapping SuperDARN and AMPERE datasets to generate global-scale patterns of the high-latitude and height-integrated Poynting flux into the ionosphere, with a time resolution of two minutes. From these, average patterns are generated based on the IMF orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Mesoscale height-integrated Poynting fluxes thus cannot fully account for the cusp neutral mass density enhancement, meaning energy deposition in the F-region or on fine-scales, which is not captured by our analysis, could be the primary driver.

How to cite: Billett, D., Perry, G., Clausen, L., Archer, W., McWilliams, K., Haaland, S., and Burchill, J.: Large scale thermospheric density enhancements in relation to downward Poynting fluxes: Statistics from CHAMP, AMPERE and SuperDARN, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1389, https://doi.org/10.5194/egusphere-egu21-1389, 2021.

EGU21-6625 | vPICO presentations | ST3.1

Energy Flux and Conductance from Meso-Scale Auroral Features Observed by All-Sky-Imagers

Christine Gabrielse, Toshi Nishimura, Margaret Chen, James Hecht, Stephen Kaeppler, Larry Lyons, and Yue Deng

Earth’s Magnetosphere-Ionosphere-Thermosphere system is inseparably coupled, with driving from above and below by various terrestrial and space weather phenomena. Global models have done well at capturing large-scale effects, but currently do not capture the meso-scale (~10s-500 km) phenomena which often are locally more intense. As computing power improves, and modeling meso-scales now becomes possible, it is vital to provide data-informed inputs of the relevant drivers. In this presentation, we focus on the energy flux deposited into the ionosphere from the magnetosphere by precipitating particles that result in the aurora, specifically at meso-scales, and the resulting conductance. Thanks to NASA’s THEMIS mission, an array of all-sky-imagers (ASIs) across Canada monitors the majority of the nightside auroral oval at a 3 second cadence, providing a global view at temporal & spatial resolutions required to study the aurora on meso-scales. Thus, we present 2-D maps over time of the energy flux, energy, and conductance that result from the aurora during solar storms and substorms, including those features at meso-scales. We determine conductance using the ASI-determined eflux and energy as inputs to the Boltzman Three Constituent (B3C) auroral transport code, compare values with Poker Flat ISR observations, and find a good comparison. We find that meso-scale aurora contributes at least 60-70% of the total precipitated energy flux during the first ten minutes of a substorm. Our results can be utilized by the broad community, for example, as inputs to atmospheric models or as the resulting conductance from precipitation inferred by magnetospheric models or satellite observations.

How to cite: Gabrielse, C., Nishimura, T., Chen, M., Hecht, J., Kaeppler, S., Lyons, L., and Deng, Y.: Energy Flux and Conductance from Meso-Scale Auroral Features Observed by All-Sky-Imagers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6625, https://doi.org/10.5194/egusphere-egu21-6625, 2021.

EGU21-794 | vPICO presentations | ST3.1

Seasonal and local time variations of auroral electrojet: CHAMP observation

Yunfang Zhong, Hui Wang, Zhichao Zheng, Yangfan He, Luyuan Sun, Jie Gao, and Kedeng Zhang

The auroral electrojet is an important element of the polar current system and an essential subject in space weather research. Based on the scalar magnetic field data from CHAMP satellite, we studied the influences of solar illumination and the dipole tilt angle (DTA) on the auroral electrojet as well as its seasonal variations. Furthermore, the auroral electrojet measured by satellite was compared with the auroral electrojet indices derived from the ground stations. It is shown that on the dayside, the auroral electrojet is more intense at a smaller solar zenith angle (SZA), whereas it’s more intense on the nightside when the SZA is larger. The daytime current is mainly controlled by the solar illumination, while the nighttime current is affected by the substorm. Compared with the solar illumination, the dipole tilt angle plays a minor role. The auroral electrojet shows an obvious annual and semiannual variation. The eastward electrojet and the dayside westward electrojet are more intense in summer than in winter, while the nightside westward electrojet is more intense in winter than in summer. The daytime westward electrojet is more intense at solstices, whereas the nighttime westward electrojet is more intense at equinoxes. The westward electrojet shows a good correlation with AL and SML indices. The eastward electrojet correlates well with the SMU index, but shows obvious difference with the AU index. The discrepancy can be attributed to the fact that the peak eastward electrojet is located outside the detection range of the auroral electrojet stations.

How to cite: Zhong, Y., Wang, H., Zheng, Z., He, Y., Sun, L., Gao, J., and Zhang, K.: Seasonal and local time variations of auroral electrojet: CHAMP observation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-794, https://doi.org/10.5194/egusphere-egu21-794, 2021.

EGU21-1084 | vPICO presentations | ST3.1

Solar wind structures and their effects on energetic electron precipitation

Josephine Alessandra Salice, Hilde Nesse Tyssøy, Christine Smith-Johnsen, and Eldho Midhun Babu

Energetic electron precipitation (EEP) into the Earth's atmosphere can collide with gases and deposit their energy there. The collisions between electrons and atmospheric gasses initiate several chemical reactions which can reduce the ozone concentration. Ozone is critically important in the middle atmosphere energy budget as changes in the ozone concentration impact temperature and winds. EEP is not fully understood in terms of how much energy is being deposited and what the associated drivers are. An accurate quantification of EEP has limitations due to instrumental challenges and therefore imposes limitations of the associated EEP parameterization into climate models. A solution to this problem is a better understanding of the driver processes of energetic electron acceleration and precipitation, alongside optimized data handling. In this study the bounce loss cone fluxes are inferred from EEP 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 relativistic energies. It investigates EEP in contexts of different solar wind structures: high-speed solar wind streams (HSSs) and coronal mass ejections (CMEs), during an eleven-year period from 2004 – 2014. While today's chemistry climate models only provide snapshots of EEP, independent of context, this study aims to understand the context EEP is created in, which will allow a more accurate estimate of the EEP to be applied in atmospheric climate models.

How to cite: Salice, J. A., Tyssøy, H. N., Smith-Johnsen, C., and Babu, E. M.: Solar wind structures and their effects on energetic electron precipitation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1084, https://doi.org/10.5194/egusphere-egu21-1084, 2021.

EGU21-15738 | vPICO presentations | ST3.1

Temporal variation of particle precipitation in Erath's polar cap from DMSP observations

Yanshi Huang and Shan Liang

Previous observations and simulations have shown that the low-energy electron precipitation in the cusp plays an important role in ionosphere and thermosphere through particle impact ionization and heating. In this study, we investigate the precipitating particles in the Earth's polar cap region, which is also an open-field line region as the cusp. In many numerical simulations of the upper atmosphere, the polar cap region is described as a uniform area with no spatial and temporal variations of the particle energy and fluxes. We analyze years of the particle observations from DMSP satellites to show the temporal variations of particle characteristics in the region poleward of 80 degree magnetic latitudes in this study. The results show the solar cycle, annual and seasonal variations of particle (electrons, ions) energy, number flux and energy flux in the polar cap. The results will be useful to improve the polar-latitude precipitating particle description in upper atmosphere modeling.

How to cite: Huang, Y. and Liang, S.: Temporal variation of particle precipitation in Erath's polar cap from DMSP observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15738, https://doi.org/10.5194/egusphere-egu21-15738, 2021.

EGU21-1240 | vPICO presentations | ST3.1

Determining latitudinal extent of energetic electron precipitation  using MEPED on-board NOAA POES

Eldho Midhun Babu, Hilde Nesse Tyssøy, Christine Smith-Johnsen, Ville Maliniemi, Josephine Alessandra Salice, and Robyn Millan

Energetic electron precipitation (EEP) from the plasma sheet and the radiation belts, can collide with gases in the atmosphere and deposit their energy. EEP increase the production of NOx and HOx, which will catalytically destroy stratospheric ozone, an important element of atmospheric dynamics. Therefore, measurement of latitudinal extent of the precipitation boundaries is important in quantifying atmospheric effects of Sun-Earth interaction and threats to spacecrafts and astronauts in the Earth's radiation belt.
This study uses measurements by MEPED detectors of six NOAA/POES and EUMETSAT/METOP satellites from 2004 to 2014 to determine the latitudinal boundaries of EEP and its variability with geomagnetic activity and solar wind drivers. Variation of the boundaries with respect to different particle energies and magnetic local time is studied. Regression analyses are applied to determine the best predictor variable based on solar wind parameters and geomagnetic indices. The result will be a key element for constructing a model of EEP variability to be applied in atmosphere climate models.

How to cite: Babu, E. M., Tyssøy, H. N., Smith-Johnsen, C., Maliniemi, V., Salice, J. A., and Millan, R.: Determining latitudinal extent of energetic electron precipitation  using MEPED on-board NOAA POES, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1240, https://doi.org/10.5194/egusphere-egu21-1240, 2021.

EGU21-10211 | vPICO presentations | ST3.1

Climatology of very high ionospheric electron temperature occurrences as observed by Swarm constellation

Igino Coco, Giuseppe Consolini, Paola De Michelis, Fabio Giannattasio, Michael Pezzopane, Alessio Pignalberi, and Roberta Tozzi

After more than seven years in orbit, the ESA Swarm satellites have provided an already large statistics of measurements of several important physical parameters of the ionosphere. In particular, electron density and temperature are measured by pairs of Langmuir Probes, and the quality of such data is now considered good enough for many studies, either science cases or climatological characterisations. Concerning specifically the electron temperature, a rather elusive parameter which is quite difficult to correctly characterize “in situ”, and for which the past literature is not so abundant with respect to other ionospheric physical quantities, the overall distributions observed by Swarm are qualitatively consistent with expectations from theory and past observations. However, a non-negligible amount of high and very high electron temperature values is regularly observed, whose distributions and properties are not trivial. In this study we aim at characterizing such features statistically as a function of latitude, local time, and season.

How to cite: Coco, I., Consolini, G., De Michelis, P., Giannattasio, F., Pezzopane, M., Pignalberi, A., and Tozzi, R.: Climatology of very high ionospheric electron temperature occurrences as observed by Swarm constellation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10211, https://doi.org/10.5194/egusphere-egu21-10211, 2021.

EGU21-2354 | vPICO presentations | ST3.1

Applying Solar Wind Observations to the IPIM Ionospheric Model

Simon Thomas, Pierre-Louis Blelly, Aurélie Marchaudon, Julian Eisenbeis, and Samuel Bird

The IRAP Plasmasphere Ionosphere Model (IPIM) is an ionospheric model which describes the transport equations of ionospheric plasma species along magnetic closed field lines. The previous iteration of IPIM used some basic models to provide estimations of the solar wind conditions and associated motions of plasma and precipitation within the ionosphere as input. In this presentation, we discuss developments to IPIM as part of the EUHFORIA project, to consistently observe space weather conditions from the Sun to the Earth’s surface. The developments of the model include using in-situ solar wind observations from the OMNI data set, ionospheric radar data of plasma motions from the Super Dual Auroral Radar Network (SuperDARN), and the Ovation model of auroral precipitation, as inputs to the model. We compare the new version with the former version and ionospheric observations to explore the differences observed by including these data within the model. We present some new results using this new version of the model to explore the ionosphere’s response to solar wind transient events such as high-speed streams and coronal mass ejections.

How to cite: Thomas, S., Blelly, P.-L., Marchaudon, A., Eisenbeis, J., and Bird, S.: Applying Solar Wind Observations to the IPIM Ionospheric Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2354, https://doi.org/10.5194/egusphere-egu21-2354, 2021.

EGU21-6883 | vPICO presentations | ST3.1

Comparative Analysis of the Measured and Modeled Equatorial Thermospheric Wind Climatology 

Sovit Khadka, Andrew Gerrard, Mariangel Fedrizzi, Patrick Dandenault, and John Meriwether

The thermospheric winds play an important role in the vertical and horizontal couplings of the upper atmosphere by modulating neutral and plasma dynamics. A large variety of observation techniques and numerical as well as empirical models have been developed to understand the behavior of thermospheric winds. The Fabry-Perot interferometer (FPI) is a widely used ground- and satellite-based optical instrument for the thermospheric winds observations in the upper atmosphere. Due to solar contamination of the fainter airglow emission during the daytime, most of the ground-based interferometric wind measurements are limited to the nighttime period only. Despite these constraints, the Second‐generation, Optimized, Fabry‐Perot Doppler Imager (SOFDI) is designed for both daytime and nighttime measurements of thermospheric winds from OI 630‐nm emission and is currently operating at the Huancayo, Peru, near the geomagnetic equator. In this study, we present a comparative analysis of the observed SOFDI wind climatological data and several other modeled results including, but not limited to, Horizontal Wind Model 2014 (HWM-14), Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model with and without implementing Prompt Penetration Electric Field (PPEF), Whole Atmosphere Model (WAM), SAMI3 model, and Magnetic mEridional NeuTrAl Thermospheric (MENTAT) model. We examine the relative performances of these models in the context of the direct-measured thermospheric winds. The day and nighttime modeled winds show an excellent agreement with the SOFDI wind data at the equatorial latitude, except for the daytime zonal winds. Further, this analysis gives a comprehensive picture of how well the measured winds provided by the SOFDI instrument and various models represent the features of the equatorial thermosphere. We also investigate and give an overview of the sources, drivers, effects, and possible mechanisms of the wind variability in the low-latitude thermosphere.

How to cite: Khadka, S., Gerrard, A., Fedrizzi, M., Dandenault, P., and Meriwether, J.: Comparative Analysis of the Measured and Modeled Equatorial Thermospheric Wind Climatology , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6883, https://doi.org/10.5194/egusphere-egu21-6883, 2021.

EGU21-9697 | vPICO presentations | ST3.1

Seasonal, Kp and IMF dependence of hemispheric asymmetry in ionospheric horizontal and field-aligned currents 

Abiyot Workayehu, Heikki Vanhamäki, Anita Aikio, and Simon Shepherd

We present statistical investigation of the seasonal, geomagnetic activity and interplanetary magnetic field (IMF) dependence of  hemispheric asymmetry in the auroral currents. Magnetic data from the Swarm satellites has been analyzed by applying the spherical elementary current system (SECS) method. Bootstrap resampling has been used to remove the difference in the number of samples as well as activity and IMF conditions between the local seasons and the hemispheres. In general, the currents are larger in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). Asymmetry is larger during low (Kp<2) than high Kp (Kp≥2) and during local winter and local autumn than local summer and local spring. Averaging over all Kp and IMF conditions, we find larger currents flowing in the NH than in the SH with the NH/SH ratio for FACs: 17­±5%, 14±5%,7±4% and 2±4% in winter, autumn spring and summer, respectively.  When making the statistical analysis for different IMF directions, we find that the orientation of IMF By has strong influence on the hemispheric asymmetry in the auroral currents, but this influence depends on local season. When IMF By is positive in NH (negative in SH), on average FACs as well as ionospheric horizontal currents are stronger in NH than inSH in most local seasons under both signs of IMF Bz. Conversely, when IMF By is negative in NH (positive in SH), the hemispheric differences of auroral currents during most local seasons are small except in local winter. Overall, comparing the hemispheres for opposite signs of IMF By, we find larger hemispheric asymmetry when IMF By is positive in  NH (negative  in SH) than vice versa.

The factors causing the observed hemispheric asymmetries in the auroral currents are not understood at the moment. Background conductances from the IRI model and cross polar cap potential values from SuperDARN dynamic modelsuggest that solar induced ionospheric conductances and convection electric field cannot explain all the observed features of the hemispheric asymmetry in auroral currents. The role of conductance enhancements due to auroral particle precipitation and possible asymmetries in the energy  flux of precipitating particles need to be investigated in future studies.

How to cite: Workayehu, A., Vanhamäki, H., Aikio, A., and Shepherd, S.: Seasonal, Kp and IMF dependence of hemispheric asymmetry in ionospheric horizontal and field-aligned currents , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9697, https://doi.org/10.5194/egusphere-egu21-9697, 2021.

EGU21-4773 | vPICO presentations | ST3.1

Statistical relations between in-situ measured Bz component and thermospheric density variations

Sofia Kroisz, Lukas Drescher, Manuela Temmer, Sandro Krauss, Barbara Süsser-Rechberger, and Torsten Mayer-Gürr

Through advanced statistical investigation and evaluation of solar wind plasma and magnetic field data, we investigate the statistical relation between the magnetic field Bz component, measured at L1, and Earth’s thermospheric neutral density. We will present preliminary results of the time series analyzes using in-situ plasma and magnetic field measurements from different spacecraft in near Earth space (e.g., ACE, Wind, DSCOVR) and relate those to derived thermospheric densities from various satellites (e.g., GRACE, CHAMP). The long and short term variations and dependencies in the solar wind data are related to variations in the neutral density of the thermosphere and geomagnetic indices. Special focus is put on the specific signatures that stem from coronal mass ejections and stream or corotating interaction regions.  The results are used to develop a novel short-term forecasting model called SODA (Satellite Orbit DecAy). This is a joint study between TU Graz and University of Graz funded by the FFG Austria (project “SWEETS”).

How to cite: Kroisz, S., Drescher, L., Temmer, M., Krauss, S., Süsser-Rechberger, B., and Mayer-Gürr, T.: Statistical relations between in-situ measured Bz component and thermospheric density variations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4773, https://doi.org/10.5194/egusphere-egu21-4773, 2021.

EGU21-3163 | vPICO presentations | ST3.1

Influence of geomagnetic disturbances on midlatitude mesosphere/lower thermosphere mean winds and tides 

Christoph Jacobi, Friederike Lilienthal, Dmitry Korotyshkin, Evgeny Merzlyakov, and Gunter Stober

Observations of upper mesosphere/lower thermosphere (MLT) wind have been performed at Collm (51°N, 13°E) and Kazan (56°N, 49°E), using two SKiYMET all-sky meteor radars with similar configuration. Daily vertical profiles of mean winds and tidal amplitudes have been constructed from hourly horizontal winds. We analyze the response of mean winds and tidal amplitudes to geomagnetic disturbances. To this end we compare winds and amplitudes for very quiet (Ap ≤ 5) and unsettled/disturbed (Ap ≥ 20) geomagnetic conditions. Zonal winds in both the mesosphere and lower thermosphere are weaker during disturbed conditions for both summer and winter. The summer equatorward meridional wind jet is weaker for disturbed geomagnetic conditions. Tendencies over Collm and Kazan for geomagnetic effects on mean winds qualitatively agree during most of the year. For the diurnal tide, amplitudes in summer are smaller in the mesosphere but greater in the lower thermosphere, but no clear tendency is seen for winter. Semidiurnal tidal amplitudes increase during geomagnetic active days in summer and winter. Terdiurnal amplitudes are slightly reduced in the mesosphere during disturbed days, but no clear effect is visible for the lower thermosphere. Overall, while there is a noticeable effect of geomagnetic variability on the mean wind, the effect on tidal amplitudes, except for the semidiurnal tide, is relatively small and partly different over Collm and Kazan.

How to cite: Jacobi, C., Lilienthal, F., Korotyshkin, D., Merzlyakov, E., and Stober, G.: Influence of geomagnetic disturbances on midlatitude mesosphere/lower thermosphere mean winds and tides , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3163, https://doi.org/10.5194/egusphere-egu21-3163, 2021.

EGU21-3017 | vPICO presentations | ST3.1

What is the optimum solar proxy for long-term ionospheric studies?

Jan Laštovička

For long-term studies as ionospheric trends investigations we have to use proxies of solar activity, because homogenous and sufficiently long data series of solar ionizing radiation are not available. Here I deal with selection of the optimum solar proxy for yearly average and monthly median values near noon (11-13 LT). Six solar proxies are used, F10.7, F30, Mg II, He II, Fα (solar H Lyman alpha flux) and R (sunspot number), foF2 from European ionosondes Juliusruh, Pruhonice and Rome, and foE from Chilton and Juliusruh over the period 1976-2019. For yearly values Mg II is the optimum proxy (but it is available only since late 1978) for foF2, with F30 being the second best. For foE the optimum proxy appears to be F10.7. For monthly medians of January, April, July and October the general pattern is the same as for yearly values.

How to cite: Laštovička, J.: What is the optimum solar proxy for long-term ionospheric studies?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3017, https://doi.org/10.5194/egusphere-egu21-3017, 2021.

We investigated seasonal variations of relationships between main ionospheric characteristics and solar and geomagnetic indices in longitudinal perspective. We consider statistically significant differences in connections of ionospheric response to the F10.7cm, R, and Kp indices on seasonal time-scales during years 1975 – 2010 covering 21st – 23rd Solar Cycles. The periods of 21 days before and after Winter/Summer Solstices and Vernal/Autumnal Equinoces are considered as season. The foF2 time series in our analysis represent measurements of daily observational data which were obtained using mid-latitude (41.4°N – 54°N) ionosondes (Chilton, Slough RL052/SL051, Juliusruh/Rugen JR055, Boulder BC840). We used local time noon 5-hour foF2 averages. For the investigation, we used seasonal differences method of conditional independence graphs (CIG) models. Significant seasonal variations are visible during ascending and descending phases of Solar cycles.

How to cite: Podolská, K., Koucká Knížová, P., and Chum, J.: Seasonal Variability of Relationship between Main Ionospheric Characteristics and Solar/Geomagnetic Indices via Graphical Models of Conditional Independences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8453, https://doi.org/10.5194/egusphere-egu21-8453, 2021.

EGU21-6775 | vPICO presentations | ST3.1

Polar cap patches, GPS TEC variations, and atmospheric gravity waves

Paul Prikryl, Robert G. Gillies, David R. Themens, Bharat S. R. Kunduri, Roger Varney, and James M. Weygand

The southward pointing field of view of the Canadian component of the Resolute Bay Incoherent Scatter Radar (RISR-C) is well suited for observing the ionospheric signatures of flux transfer events and subsequent polar patch formation in the cusp.  The fast azimuthally oriented flows and associated density depletions often show an enhanced ion temperature from Joule heating caused by the sudden change in plasma flow direction. The newly formed polar patches are then observed as they propagate through the field-of-views of both RISR-C and RISR-N. In the ionosphere, the electron density gradients imposed in the cusp, and small-scale irregularities resulting from gradient-drift instability, particularly in the trailing edges of patches, cause GPS TEC and phase variations, and sometimes amplitude scintillation. The neutral atmosphere is affected by ionospheric currents resulting in Joule heating. The pulses of ionospheric currents in the cusp launch atmospheric gravity waves (AGWs) causing traveling ionospheric disturbances, as they propagate equatorward and upward. On the other hand, the downward propagating AGW packets can impact the lower atmosphere, including the troposphere. Despite significantly reduced wave amplitudes, but subject to amplification upon over-reflection in the upper troposphere, these AGWs can trigger/release existing moist instabilities, initiating convection and latent heat release, the energy leading to intensification of storms.

How to cite: Prikryl, P., Gillies, R. G., Themens, D. R., Kunduri, B. S. R., Varney, R., and Weygand, J. M.: Polar cap patches, GPS TEC variations, and atmospheric gravity waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6775, https://doi.org/10.5194/egusphere-egu21-6775, 2021.

EGU21-4250 | vPICO presentations | ST3.1

Anomalous propagation of medium scale GWs along neutral winds

Jan Rusz, Jaroslav Chum, and Jiří Baše

Azimuth of medium scale gravity waves (GWs) propagation in the thermosphere/ionosphere fundamentally depends on the daytime and day of year. Previous studies show that the GWs mostly propagate against the predominant direction of neutral winds in the ionosphere. However, several cases of propagation along the wind direction have also been identified, specifically around the equinoxes. The analysis is based on remote observation of the ionosphere using multi–frequency and multipoint continuous Doppler sounding. The network consists of at least three spatially separated sounding paths (transmitter-receiver pairs) at three frequencies, situated in the western part of the Czech Republic. The apparent horizontal velocity and azimuth of GWs are derived from the time shifts observed for different measuring paths. The HWM14 neutral wind model is used for comparison of neutral winds with the observed phase speeds of GWs. Cases of anomalous propagation of GWs along the direction of neutral winds are analyzed. It is shown that the observed GW periods can be substantially shorter than the intrinsic periods in the wind-rest frame owing to Doppler shift.

How to cite: Rusz, J., Chum, J., and Baše, J.: Anomalous propagation of medium scale GWs along neutral winds, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4250, https://doi.org/10.5194/egusphere-egu21-4250, 2021.

EGU21-866 | vPICO presentations | ST3.1

Elevation angles and attenuation of gravity waves in the ionosphere

Jaroslav Chum, Kateřina Podolska, Jiri Base, and Jan Rusz

     Characteristics of gravity waves (GWs) are studied from multi-point and multi-frequency continuous Doppler sounding in the Czech Republic. Three dimensional (3D) phase velocities of GWs are determined from phase shifts between the signals reflecting from the ionosphere at different locations that are separated both vertically and horizontally; the reflection heights are determined by a nearby ionospheric sounder located in Průhonice. Wind-rest frame (intrinsic) velocities are calculated by subtracting the neutral wind velocities, obtained by HWM-14 wind model, from the observed GW velocities. In addition, attenuation of GWs with height was estimated from the amplitudes (Doppler shifts) observed at different altitudes. A statistical analysis was performed over two one-year periods: a) from July 2014 to June 2015 representing solar maximum b) from September 2018 to August 2019 representing solar minimum.   

     The results show that the distribution of elevation angles of wave vectors in the wind–rest frame is significantly narrower than in the Earth frame (observed elevations). Possible differences were also found between the wind–rest frame elevation angles obtained for the solar maximum (mean value (around -24°) and solar minimum (mean value round -37°). However, it is demonstrated that the elevation angles partly depended on the daytime and day of year. As the distribution of the time intervals suitable for the 3D analysis in the daytime–day of year plane was partly different for solar maximum and minimum, no reliable conclusion about the possible dependence of elevation angles on the solar activity can be drawn.

     It is shown that the attenuation of GWs in the ionosphere was in average smaller at the lower heights. This is consistent with the idea that mainly viscous damping and losses due to thermal conductivity are responsible for the attenuation.

  

How to cite: Chum, J., Podolska, K., Base, J., and Rusz, J.: Elevation angles and attenuation of gravity waves in the ionosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-866, https://doi.org/10.5194/egusphere-egu21-866, 2021.

EGU21-6351 | vPICO presentations | ST3.1

Problem ot the energy transfer for radio paths near single-hop limiting distance for low solar activity

Barbara Atamaniuk, Igor V. Krasheninnikov, Alexei Popov, and Barbara Matyjasiak

Formation the feature, in a form of deep trough, in frequency dependence of the wave field strength for single-hop paths with distances near classical limiting distance 3000 km at low level of solar activity was considered. Model calculations within the framework of the extended global ionospheric IRI model show high probability for appearing such a situation in the local daytime with a developed regular E-layer of the ionosphere. Some experimental results in multifrequency radio sounding of the ionosphere with a registration of the deep trough in frequency dependence of signal-to-noise ratio (SNR) were analyzed. It is shown that the IRI model, in principle, makes it possible to reproduce this peculiarity in the wave field energy parameters, but in some cases of experimental data, to a large extent, is able to provide only a qualitative description of this effect. Possible reasons for the quantitative discrepancy between experimental and model results are discussed.

How to cite: Atamaniuk, B., Krasheninnikov, I. V., Popov, A., and Matyjasiak, B.: Problem ot the energy transfer for radio paths near single-hop limiting distance for low solar activity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6351, https://doi.org/10.5194/egusphere-egu21-6351, 2021.

EGU21-6433 | vPICO presentations | ST3.1

The influence of meteoric smoke particles on the artificial heating effect in the D-region

Margaretha Myrvang, Carsten Baumann, and Ingrid Mann

Artificial heating increases the electron temperature by transferring the energy of powerful high frequency radio waves into thermal energy of electrons. Current models most likely overestimate the effect of artificial heating in the D-region compared to observations [1, 2]. We investigate if the presence of meteoric smoke particles can explain the discrepancy between observations and model. The ionospheric D-region varies in altitude range from about 50 km to 100 km. In the D-region, the electron density is low, the neutral density is relatively high and it is here that meteors ablate. The ablated meteoric material is believed to recondense to form meteoric smoke particles (MSP). The presence of MSP in the D-region can influence plasma densities through charging of dust by electrons and ions, depending on different ionospheric conditions. Charging of dust influence the electron density mainly through electron attachment to the dust, which results in height regions with less electron density. The heating effect varies with electron density height profile [3], since the reduction in radio wave energy is due to absorption by electrons. We study artificial heating of the D-region and consider MSP by using a one-dimensional ionospheric model [4], which also includes photochemistry. In the ionospheric model, we assume that artificial heating only influences the chemical reactions that depend on electron temperature. We model the electron temperature increase during artificial heating with an electron density calculated from the ionospheric model, where we will do the modelling with and without the MSP and compare day and night condition. Our results show a difference in electron temperature increase with the MSP compared to without the MSP and between day and night condition.

References:

  • [1] Senior, A., M. T. Rietveld, M. J. Kosch and W. Singer (2010): «Diagnosing radio plasma heating in the polar summer mesosphere using cross modulation: Theory and observations». Journal of geophysical research, Vol. 115, A09318.
  • [2] Kero, A., C.-F Enell, Th. Ulich, E. Turunen, M. T. Rietveld and F. H. Honary (2007): «Statistical signature of active D-region HF heating in IRIS riometer data from 1994-2004». Ann. Geophys., 25, 407-415.
  • [3] Kassa, M., O. Havnes and E. Belova (2005): «The effect of electron bite-outs on artificial electron heating and the PMSE overshoot». Annales Geophysicae, 23, 3633-3643.
  • [4] Baumann, C., M. Rapp, A. Kero and C.-F. Enell (2013): «Meteor smoke influence on the D-region charge balance –review of recent in situ measurements and one-dimensional model results». Ann. Geophys., 31, 2049-2062.

How to cite: Myrvang, M., Baumann, C., and Mann, I.: The influence of meteoric smoke particles on the artificial heating effect in the D-region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6433, https://doi.org/10.5194/egusphere-egu21-6433, 2021.

EGU21-2148 | vPICO presentations | ST3.1

On the possibility of an intra-Earth source of Sq-variations of the Earth's magnetic field

Beibit Zhumabayev and Ivan Vassilyev

Analysis of the direction of motion of the vector of Sq-variations of the Earth's magnetic field, depending on the time of day and season of the year, shows that the observed Sq-variation is similar to the magnetic field created by a negatively charged spherical body moving in space. Transformations of the Sq-variation vector from the local coordinate system of the magnetic observatory to the ecliptic coordinate system are performed. A possible connection between the origin of the Sq-variation and the electric dipole moment of quartz molecules oriented towards the center of the Earth during the crystallization of the mineral and causing the electric and dipole magnetic fields of the Earth is considered. A scheme for conducting an experiment that allows us to separate the effects of extraterrestrial and extraterrestrial sources of Sq-variations is proposed.

How to cite: Zhumabayev, B. and Vassilyev, I.: On the possibility of an intra-Earth source of Sq-variations of the Earth's magnetic field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2148, https://doi.org/10.5194/egusphere-egu21-2148, 2021.

ST3.2 – Vertical coupling in the Atmosphere-Ionosphere system

We examine impacts of geomagnetic activity on CO2-driven trend in the Ionosphere and Thermosphere (IT) using the GAIA whole atmosphere model. The model reveals three salient features. (1) Geomagnetic activities usually weakens the CO2-driven trend at a fixed altitude. Among the IT parameters analyzed, the thermosphere mass density is the most robust indicator for CO2 cooling effect even with geomagnetic activity influences. (2) Geomagnetic activities can either strengthen or weaken the CO2-driven trend in hmF2 and NmF2, depending on local time and latitudes. This renders the widely used linear fitting methods invalid for removing geomagnetic effects from observations. (3) An interdependency exists between the efficiency of CO2 forcing and geomagnetic forcing, with the former enhances at lower geomagnetic activity level, while the latter enhances at higher CO2 concentration. This could imply that the CO2-driven trend would accelerate in periods of declining geomagnetic activity, while magnetic storms may have larger space weather impacts in the future with increasing CO2. These findings provide a preliminary model framework to understand interactions between the CO2 forcing from below and the geomagnetic forcing from above.

How to cite: Liu, H., Tao, C., and Jin, H.: Geomagnetic activity effects on CO2‐driven trend in the thermosphere and ionosphere:  ideal model experiments with GAIA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11128, https://doi.org/10.5194/egusphere-egu21-11128, 2021.

EGU21-7320 | vPICO presentations | ST3.2

The hemispheric asymmetry of ionospheric lunitidal signatures during Sudden Stratospheric Warmings in the eastern Asian and American sectors

Jing Liu, Donghe Zhang, Larisa Goncharenko, Shun-Rong Zhang, Maosheng He, Yongqiang Hao, and Zuo Xiao

During Sudden Stratospheric Warming events, the ionosphere exhibits phase-shifted semi-diurnal perturbations, which are typically attributed to vertical coupling associated with the semi-diurnal lunar tide (M2). Our understanding of ionospheric responses to M2 is limited. This study focuses on fundamental vertical coupling processes associated with the latitudinal extent and hemispheric asymmetry of ionospheric M2 signatures, using total electron content data from the eastern Asian and American sectors. Our results illustrate that the asymmetry maximizes at around 15°N and 20°S magnetic latitudes. In the southern hemisphere, the M2-like signatures extend deep into midlatitude and, in the American sector, encounter the Weddell Sea Anomaly. The M2 amplitude is larger in the northern hemisphere and such asymmetry is more distinct in the eastern Asian sector. The hemispheric asymmetry of M2 signatures in the low latitude can be primarily explained by the trans-equatorial wind modulation of the equatorial plasma fountain. Other physical processes could also be relevant, including hemispheric asymmetry of the M2 below the F region, the ambient thermospheric composition and ionospheric plasma distribution, and the geomagnetic field configuration.

How to cite: Liu, J., Zhang, D., Goncharenko, L., Zhang, S.-R., He, M., Hao, Y., and Xiao, Z.: The hemispheric asymmetry of ionospheric lunitidal signatures during Sudden Stratospheric Warmings in the eastern Asian and American sectors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7320, https://doi.org/10.5194/egusphere-egu21-7320, 2021.

EGU21-3773 | vPICO presentations | ST3.2

Ionospheric Variability: Response to Sudden Stratospheric Warming events during Solar Cycle 24

Sumedha Gupta, Arun Kumar Upadhayaya, and Devendraa Siingh

With low solar activity and unusual progression, Solar Cycle 24 lasted from December 2008 to December 2019 and is considered to be the weakest cycle in the last 100 years. During such quiet solar background conditions, the wave forcing from lower atmosphere will have a perceivable effect on the ionosphere. This study examines the ionospheric response to meteorological phenomenon of Sudden Stratospheric Warming (SSW) events during Solar Cycle 24 (Arctic winter 2008/09 to 2018/19). Ionospheric response to each of these identified warming periods is quantified by studying ground – based Global Positioning System (GPS) derived vertical Total Electron Content (VTEC) and its deviation from monthly median (ΔVTEC) for four longitudinal chains, selected from worldwide International GNSS service (IGS) stations. Each chain comprises of eight stations, chosen in such a way as to cover varied latitudes both in Northern and Southern Hemispheres. A strong latitude – dependent response of VTEC perturbations is observed after the peak stratospheric temperature anomaly (ΔTmax). The semidiurnal behaviour of VTEC, with morning increase and afternoon decrease, is mostly observed at near-equatorial stations. This vertical coupling between lower and upper atmosphere during SSW is influenced by prominent 13-14 days periodicities in VTEC observations, along with other periodicities of 7, 5, and 3 days. It is seen that the ionospheric response increases with increase in solar activity. Further, under similar ionizing conditions, quite similar ionospheric response is observed, irrespective of ΔTmax and type of SSW event being major or minor. However, under similar SSW strength (ΔTmax), no prominent pattern in ionospheric response is observed. The causative mechanism for the coupling processes in the atmosphere during these SSW events is discussed in detail.

How to cite: Gupta, S., Upadhayaya, A. K., and Siingh, D.: Ionospheric Variability: Response to Sudden Stratospheric Warming events during Solar Cycle 24, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3773, https://doi.org/10.5194/egusphere-egu21-3773, 2021.

We present an analysis of the perturbations and wave characteristics in equatorial electrojet (EEJ) and equatorial zonal winds in the mesosphere and lower thermosphere region during three sudden stratospheric warming (SSW) events, based on the wind observations by two meteor radars in Indonesia and the geomagnetic field observations in India. During three SSWs, the shifting semidiurnal perturbations are consistently observed in the EEJ and accompanied with strong 2-day periodic perturbations simultaneously. The semidiurnal lunar (L2) tidal amplitudes in the EEJ and zonal winds show the prominent enhancements during the episodes of EEJ perturbations. The time-period spectra of the L2 tidal amplitudes in both the EEJ and zonal winds present the obvious quasi-2-day wave (QTDW) amplification with good agreement during these periods. Our results firstly reveal the important contributions of QTDW to EEJ perturbations during SSWs and the semidiurnal lunar tides modulated by QTDW serve as the main forcing agent therein

How to cite: Li, Y. and Chen, G.: Effect of Semidiurnal Lunar Tides Modulated by Quasi-2-Day Wave on Equatorial Electrojet during Three Sudden Stratospheric Warming events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6985, https://doi.org/10.5194/egusphere-egu21-6985, 2021.

EGU21-645 | vPICO presentations | ST3.2

The O2 aurora observed by the TIMED/SABER satellite

Hong Gao, Jiyao Xu, and Yajun Zhu

We studied O2 aurora based on the observations of O2 emission at 1.27 μm from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument during the nighttime over 18 years. The horizontal structure and vertical profile of O2 auroral volume emission rate is obtained after removing O2 nightglow contamination. The O2 auroral intensity varies between 0.14 and 5.97 kR, and the peak volume emission rate varies between 0.97 × 102 and 41.01 × 102 photons cm−3 s−1. The O2 auroral intensity and peak volume emission rate exponentially increases with increasing Kp index, whereas the peak height decreases with increasing Kp index. The O2 auroral intensity and peak volume emission rate under solar minimum condition are larger than those under solar maximum condition. The peak height under solar minimum condition is lower than that under solar maximum condition.

How to cite: Gao, H., Xu, J., and Zhu, Y.: The O2 aurora observed by the TIMED/SABER satellite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-645, https://doi.org/10.5194/egusphere-egu21-645, 2021.

EGU21-7082 | vPICO presentations | ST3.2

Comparison of thermospheric winds measured by GOCE and ground-based FPIs at low and middle latitudes

Guoying Jiang, Chao Xiong, Claudia Stolle, Jiyao Xu, Wei Yuan, Jonathan J. Makela, Brian J. Harding, Robert B. Kerr, Günther March, and Christian Siemes

The reestimates of thermospheric winds from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) accelerometer measurements were released in April 2019. In this study, we compared the new-released GOCE crosswind (cross-track wind) data with the horizontal winds measured by four Fabry-Perot interferometers (FPIs) located at low and middle latitudes. Our results show that during magnetically quiet periods the GOCE crosswind on the dusk side has typical seasonal variations with largest speed around December and lowest speed around June, which is consistent with the ground-FPI measurements. The correlation coefficients between the four stations and GOCE crosswind data all reach around 0.6. However, the magnitude of the GOCE crosswind is somehow larger than the FPIs wind, with average ratios between 1.37-1.69. During geomagnetically active periods, the GOCE and FPI derived winds have a lower agreement, with average ratios of 0.85 for the Asian station (XL) and about 2.15 for the other three American stations (PAR, Arecibo and CAR). The discrepancies of absolute wind values from the GOCE accelerometer and ground-based FPIs should be mainly due to the different measurement principles of the two techniques. Our results also suggested that the wind measurements from the XL FPI located at the Asian sector has the same quality with the FPIs at the American sector, although with lower time resolution.

How to cite: Jiang, G., Xiong, C., Stolle, C., Xu, J., Yuan, W., Makela, J. J., Harding, B. J., Kerr, R. B., March, G., and Siemes, C.: Comparison of thermospheric winds measured by GOCE and ground-based FPIs at low and middle latitudes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7082, https://doi.org/10.5194/egusphere-egu21-7082, 2021.

EGU21-10514 | vPICO presentations | ST3.2

A simulation of the influence of DE3 tide on nitric oxide infrared cooling

Zhipeng Ren, Weixing Wan, Jiangang Xiong, and Xing Li

Using GCITEM-IGGCAS model, we simulate the influence of the eastward propagating non-migrating diurnal tide with zonal wavenumber-3 (DE3) on nitric oxide (NO) infrared cooling rate. We find that the DE3 tide can drive a DE3 signal in lower thermospheric NO cooling rate, and the simulated altitudinal and seasonal variations are according with that of DE3 signal in equatorial lower thermospheric NO cooling rate observed by Oberheide et al. [2013], which is based on the TIMED/SABER observations during the solar minimum year 2008. This signal mainly shows an annual variation, which is stronger between June and September, and weaker near November. The maximum of the absolute signal, whose value is about 0.35*10-9 W/m3, occurs near the height of 130 km, but the relative signal mainly shows its peak with a value of 40% near the height of 100 km. Due to the difference of the driving mechanism, the distribution of NO signals in different latitudinal regions shows obvious difference. The middle- and low-latitude NO signal show smooth variation, while the high-latitude signal is discontinuous. The DE3 signal in NO cooling rate is mainly controlled by DE3 temperature tide and DE3 NO tide, meanwhile, the influences of DE3 neutral density tide on the DE3 signal can be ignored. The relative contributions of the DE3 NO tide and of the DE3 temperature tide vary with geographic latitude. The DE3 cooling rates in middle- and low- latitude and in high-latitude are respectively mainly driven by the DE3 temperature tide DE3 NO tide. DE3 tide may not only drive the DE3 signal, but also affect the lower thermospheric zonal mean NO cooling rate. The maximum of the absolute influence, whose value is about 0.12*10-9 W/m3, occurs above the height of 140 km, but the relative influence mainly shows its peak with a value of 10% near the height of 100 km.

How to cite: Ren, Z., Wan, W., Xiong, J., and Li, X.: A simulation of the influence of DE3 tide on nitric oxide infrared cooling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10514, https://doi.org/10.5194/egusphere-egu21-10514, 2021.

EGU21-14705 | vPICO presentations | ST3.2

The ionospheric response to the 2019 and 2021 Northern Hemisphere SSWs

Tarique Adnan Siddiqui, Yosuke Yamazaki, and Claudia Stolle

Owing to the progress that have been made in understanding the vertical coupling mechanisms in the last decade, it is now well established that the thermosphere-ionosphere system under quiet geomagnetic conditions is highly sensitive to lower atmospheric forcing.  In this regard, the studies linking the upper atmosphere (mesosphere-lower thermosphere-ionosphere) variability and sudden stratospheric warming (SSW) events have been particularly important. The changes to atmospheric circulation due to SSW events modulate the spectrum of vertically upward propagating atmospheric waves (gravity waves, tides, and planetary waves) resulting in numerous changes in the state of the upper atmosphere. Much of our understanding about the upper atmospheric variability associated due to SSWs events have been gained by studying the 2008/2009 Northern Hemisphere (NH) SSW event, which occurred under extremely quiet geomagnetic conditions. Recently, two major NH SSW events in the winter of 2018/2019 and 2020/2021 occurred under similarly quiet geomagnetic conditions. In this work, both these SSW events have been simulated using Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) and the low- and mid-latitude ionospheric response to both these SSW events will be presented.

How to cite: Siddiqui, T. A., Yamazaki, Y., and Stolle, C.: The ionospheric response to the 2019 and 2021 Northern Hemisphere SSWs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14705, https://doi.org/10.5194/egusphere-egu21-14705, 2021.

EGU21-8857 | vPICO presentations | ST3.2

Whole Atmosphere Coupling during the September 2019 Antarctic Sudden Stratospheric Warming

Yosuke Yamazaki and Yasunobu Miyoshi

A sudden stratospheric warming (SSW) is a large-scale meteorological phenomenon, which is most commonly observed in the Arctic region during winter months. In September 2019, a rare SSW occurred in the Antarctic region, providing a unique opportunity to study its impact on the middle and upper atmosphere. Geopotential height measurements by the Microwave Limb Sounder aboard NASA's Aura satellite reveal a burst of westward-propagating quasi-6-day wave (Q6DW) with zonal wavenumber 1 in the mesosphere and lower thermosphere following the SSW. At this time, ionospheric data from ESA's Swarm satellite constellation mission show prominent 6-day variations in the daytime equatorial electrojet intensity and low-latitude plasma densities. The whole atmosphere model GAIA reproduces salient features of the middle and upper atmosphere response to the SSW. GAIA results suggest that the observed ionospheric 6-day variations are not directly driven by the Q6DW but driven indirectly through tidal modulations by the Q6DW. An analysis of global total electron content data reveals signatures of secondary waves arising from the nonlinear interaction between the Q6DW and tides.

How to cite: Yamazaki, Y. and Miyoshi, Y.: Whole Atmosphere Coupling during the September 2019 Antarctic Sudden Stratospheric Warming, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8857, https://doi.org/10.5194/egusphere-egu21-8857, 2021.

EGU21-608 | vPICO presentations | ST3.2

Planetary wave-tide nonlinear interactions increase the variety of MLT waves in summer 2019

Maosheng He, Jorge L. Chau, Jeffrey M. Forbes, Denise Thorsen, Guozhu Li, Tarique Adnan Siddiqui, Yosuke Yamazaki, Wayne K. Hocking, Christoph Jacobi, and Peter Hoffmann

Mesospheric winds collected by multiple meteor radars at mid-latitudes in the northern hemispheric are combined to investigate wave activities in June—October 2019. Dual-station approaches are developed and implemented to diagnose zonal wavenumber $m$ of spectral peaks.  In  September—October, diagnosed are quasi‐10‐ and 6‐day planetary waves (Q10DW and Q6DW, $m=$1), solar semi-diurnal tides with $m=$1, 2, 3 (SW1, SW2, and SW3), lunar semi-diurnal tide, and the upper and lower sidebands (USB and LSB, $m=$ 1 and 3) of Q10DW‐SW2 nonlinear interactions.  During June— September, diagnosed are Rossby-gravity modes ($m=$3 and 4 at periods $T=$ 2.1d and 1.7d), and their USBs and LSBs generated from interactions with diurnal, semi-diurnal, ter-diurnal, and quatra-diurnal migrating tides. These results demonstrate that the planetary wave-tide nonlinear interactions significantly increase the variety of waves in the mesosphere and lower thermosphere region (MLT).

How to cite: He, M., Chau, J. L., Forbes, J. M., Thorsen, D., Li, G., Siddiqui, T. A., Yamazaki, Y., Hocking, W. K., Jacobi, C., and Hoffmann, P.: Planetary wave-tide nonlinear interactions increase the variety of MLT waves in summer 2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-608, https://doi.org/10.5194/egusphere-egu21-608, 2021.

EGU21-7651 | vPICO presentations | ST3.2

Stratospheric jet stream as a possible source for similar seasonal variations of the short-term variability in the ionosphere, upper mesosphere and subpolar stratosphere

Anna Yasyukevich, Vera Sivtseva, Irina Medvedeva, Marina Chernigovskaya, Petr Ammosov, and Galina Gavrilyeva

Based on the data of Total Electron Content (TEC) and OH rotational temperature, we analyze temporal and spatial features of the level of short-term variability (within the periods of up to several hours) at the ionosphere and the upper mesosphere. The study is carried out at three points located at mid-latitude, subauroral, and high-latitude regions during for more than 5 years period. The dynamics of variability, both in the ionosphere and at the mesopause, have the similar pattern with a clear seasonal variation. The maximum in the variability is registered in winter, and it exceeds up to 5-6 times the variability level during the summer period. This feature is observed regularly. The revealed dynamics does not correlate with changes the in geomagnetic and solar activities. The variability within considered periods is generally related to activity of Internal Gravity Waves in the upper atmosphere. We suggest that a source of the related seasonal variations in the variability may be the stratospheric high-velocity jet stream that develops in the subauroral regions during winter months. We propose a stratosphere disturbance index based on Era-5 Reanalysis data. The index is shown to have a maximum at subpolar regions and experience the similar regular seasonal variation with a maximum during winter months. We show a clear correlation between the mesosphere/ionosphere variability indices and the stratosphere disturbance index. The obtained results indicate a strong coupling between the short-period variability in the ionosphere, in the upper mesosphere, and in the subauroral stratosphere. The study is supported by the Russian Science Foundation Grant No. 20-77-00070.

How to cite: Yasyukevich, A., Sivtseva, V., Medvedeva, I., Chernigovskaya, M., Ammosov, P., and Gavrilyeva, G.: Stratospheric jet stream as a possible source for similar seasonal variations of the short-term variability in the ionosphere, upper mesosphere and subpolar stratosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7651, https://doi.org/10.5194/egusphere-egu21-7651, 2021.

EGU21-12929 | vPICO presentations | ST3.2

Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany

Mani Sivakandan, Jorge L Chau, Carlos Martinis, Yuichi Otsuka, Jens Mielich, and Fede Conte

Northwest to southeast phase fronts with southwestward moving features are commonly observed in the nighttime midlatitude ionosphere during the solstice months at low solar activity. These features are identified as nighttime MSTIDs (medium scale traveling ionospheric disturbances). Initially, they were considered to be a manifestation of neutral atmospheric gravity waves. Later on, investigations showed that the nighttime MSTIDs are electrified in nature and mostly confined to the mid and low latitude ionosphere. Although the overall characteristics of the nighttime MSTIDs are mostly well understood, the causative mechanisms are not well known. Perkins instability mechanism was believed to be the cause of nighttime MSTIDs, however, the growth rate of the instability is too small to explain the perturbations observed. Recently, model simulations and observational studies suggest that coupling between sporadic-E layers and other type of E-region instabilities, and the F region may be relevant to explain the generation of the MSTIDs.

In the present study simultaneous observation from OI 630 nm all-sky airglow imager, GPS-TEC, ionosonde and Meteor radars, are used to investigate the role of E and F region coupling on the generation of MSTIDs .Nighttime MSTIDs observed on three nights (14 March 2020, 23 March 2020 and 28 May 2020) in the OI 630 nm airglow images over Kuehlungsborn (54°07'N; 11°46'E, 53.79N  mag latitude), Germany, are presented. Simultaneous detrended GPS-TEC measurements also shows presence of MSTIDs on these nights. In addition, simultaneous ionosonde observations over Juliusruh (54°37.7'N 13°22.5'E) show spread-F in the ionograms as well as sporadic-E layer occurrence.  Furthermore, we also investigate the MLT region wind variations during these nights. The role of Es-layers and the interplay between the winds and Es-layers role on the generation of the MSTIDs will be discussed in detail in this presentation.

 

How to cite: Sivakandan, M., Chau, J. L., Martinis, C., Otsuka, Y., Mielich, J., and Conte, F.: Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12929, https://doi.org/10.5194/egusphere-egu21-12929, 2021.

EGU21-2400 | vPICO presentations | ST3.2

Tidal Signature Detection in Midlatitude Sporadic E Occurrence Rate, Using FORMOSAT-3/COSMIC Radio Occultation Data

Sahar Sobhkhiz, Yosuke Yamazaki, and Christina Arras

Sporadic E (Es) is a transient phenomenon where thin layers of enhanced electron density appear in the ionospheric E region (90-120 km altitude). Es can influence radio propagation, and its global characteristics have been of great interest to radio communications and navigations. Atmospheric diurnal and semidiurnal tides cause horizontal wind shears at E-region heights by giving rise to ions and electrons' vertical motions. These shears will lead to the formation of Es layers. This research aims to study the role of atmospheric solar and lunar tides in Mid-latitude Es occurrence. For this purpose, radio occultation data from FORMASAT-3/COSMIC mission of 11 years (2007 to 2017), which provide complete global coverage, have been used. The results show both lunar and solar tidal signatures in Es occurrence. These tidal signatures are longitudinally dependent, which can result from non-migrating tides or modulation of migrating tidal signatures by zonally varying geomagnetic field.

How to cite: Sobhkhiz, S., Yamazaki, Y., and Arras, C.: Tidal Signature Detection in Midlatitude Sporadic E Occurrence Rate, Using FORMOSAT-3/COSMIC Radio Occultation Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2400, https://doi.org/10.5194/egusphere-egu21-2400, 2021.

EGU21-10134 | vPICO presentations | ST3.2

Timing of the VLF October effect in relation to mesospheric wind dynamics

E. Liliana Macotela, Nicholas Pedatella, Daniel Marsh, Mark Clilverd, Jorge Chau, Jyrki Manninen, Daniela Banys, and Marc Hansen

The seasonal variation of the daytime lower ionosphere, monitored using the propagation of Very Low Frequency (VLF) radio waves, shows an asymmetry when comparing the spring and autumn transitions. Considering the solar zenith angle variation, it can explain the spring transition but not the autumn one. The climatological variation exposes that the maximum of the VLF deviation is around the beginning of October. Thus, the deviation is called “the October effect”. This study aims to understand the possible atmospheric phenomena behind this effect. We use VLF signals transmitted from USA (NAA, f = 24 kHz), UK (GQD, f=19.6 kHz) and Iceland (NRK, f = 37.5 kHz) recorded in Northern Finland from 2011 to 2019. We compare our results with the Whole Atmosphere Community Climate Model with the thermosphere-ionosphere eXtension (WACCM-X) data. The October effect is separated into climatological earliest and latest effect according to WACCM-X climatological earliest and latest transitions from eastward to westward mean zonal winds

How to cite: Macotela, E. L., Pedatella, N., Marsh, D., Clilverd, M., Chau, J., Manninen, J., Banys, D., and Hansen, M.: Timing of the VLF October effect in relation to mesospheric wind dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10134, https://doi.org/10.5194/egusphere-egu21-10134, 2021.

EGU21-296 | vPICO presentations | ST3.2

Burst of Unusual Quasi-10 day Wave During the 2019 Southern Sudden Stratospheric Warming

Jack Wang, Scott Palo, Jeffrey Forbes, John Marino, and Tracy Moffat-Griffin

An unusual sudden stratospheric warming (SSW) occurred in the Southern hemisphere in September 2019. Ground-based and satellite observations show the presence of a transient westward-propagating quasi-10 day planetary wave with zonal wavenumber one during the SSW. The planetary wave activity maximizes in the MLT region approximately 10 days after the SSW onset. Analysis indicates the quasi-10 day planetary wave is symmetric about the equator which is contrary to theory for such planetary waves. 

Observations from MLS and SABER provide a unique opportunity to study the global structure and evolution of the symmetric quasi-10 day wave with observations of both geopotential height and temperature during these unusual atmospheric conditions. The space-based measurements are combined with meteor radar wind measurements from Antarctica, providing a comprehensive view of the quasi-10 day wave activity in the southern hemisphere during this SSW. We will also present the results of our mesospheric and lower thermospheric analysis along with a preliminary analysis of the ionospheric response to these wave perturbations.

How to cite: Wang, J., Palo, S., Forbes, J., Marino, J., and Moffat-Griffin, T.: Burst of Unusual Quasi-10 day Wave During the 2019 Southern Sudden Stratospheric Warming, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-296, https://doi.org/10.5194/egusphere-egu21-296, 2021.

EGU21-10289 | vPICO presentations | ST3.2

Impact of Antarctic Sudden Stratospheric Warming on Mid-Latitude Thermosphere and Ionosphere over USA and Europe

Larisa Goncharenko, V Lynn Harvey, Katelynn Greer, Shun-Rong Zhang, and Anthea Coster

Limited observational evidence indicates that ionospheric changes caused by Arctic SSWs propagate to at least the middle latitudes in the Southern Hemisphere. However, it is not known if similar ionospheric anomalies are produced by Antarctic SSWs, mostly because Antarctic SSWs occur less often than the Arctic events. The sudden stratospheric warming of September 2019 has provided a perfect opportunity to investigate whether SSW are linked to upper atmospheric anomalies at middle latitudes of the opposite hemisphere. In this study we provide an overview of thermospheric and ionospheric anomalies observed in September 2019 at middle latitudes in the Northern Hemisphere. Our results indicate persistent and strong positive anomalies in total electron content and thermospheric O/N2 ratio observed in the western region of USA. Central and eastern regions of USA do not experience similar positive perturbations and show mostly moderate suppression of TEC reaching 20-40% of the baseline. Both positive and negative anomalies are observed over the central Europe. We discuss potential mechanisms that could be responsible for the observed features and suggest that regional differences in TEC response could be related to modulation of thermospheric winds by SSW and large declination angle over Western US.

How to cite: Goncharenko, L., Harvey, V. L., Greer, K., Zhang, S.-R., and Coster, A.: Impact of Antarctic Sudden Stratospheric Warming on Mid-Latitude Thermosphere and Ionosphere over USA and Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10289, https://doi.org/10.5194/egusphere-egu21-10289, 2021.

EGU21-12567 | vPICO presentations | ST3.2

Examining and comparing observed and simulated daytime neutral wind and ionospheric drift variations

Astrid Maute, Brian Harding, Joanne Wu, Colin Triplett, Rodrick Heelis, Jeffrey M. Forbes, and Thomas Immel

The neutral wind dynamo plays an important role in generating low-latitude ionospheric variability and space weather. The characteristic equatorial ionization anomaly is generated by the daytime equatorial upward drift, which has imprinted on it the variation from upward propagating tides and waves. Observations and modeling studies have indicated large variability of the plasma drift on time scales from days to seasons associated with the wind dynamo at low and middle latitudes. The relationship of the ionospheric drift variability to the neutral wind variations is still not fully understood. The Ionospheric Connection explorer (ICON) mission is designed to focus on the low to middle latitude region and measures key parameters, such as the plasma drift and density and neutral temperatures and winds, to address the question of vertical coupling.

In this presentation, we will focus on the ICON observations and compare to Whole Atmosphere Community Climate Model-Extended (WACCM-X) simulations to examine the daytime low latitude ion drift and neutral wind variations. We investigate the day-to-day and longitudinal variation between concurrent ion drift and neutral wind variations over short time periods to quantify the contribution of the neutral wind in generating the ionospheric drift variations. Employing WACCM-X simulations, we investigate the importance of contributing factors, such as ionospheric conductivities, the geomagnetic main field, magnetosphere-ionosphere coupling, and the neutral wind, in generating the observed ionospheric drift variations. While we focus in this study on field line integrated ionospheric current density due to electric field/drift and neutral wind, we conclude by discussing our results in a more general context.

How to cite: Maute, A., Harding, B., Wu, J., Triplett, C., Heelis, R., Forbes, J. M., and Immel, T.: Examining and comparing observed and simulated daytime neutral wind and ionospheric drift variations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12567, https://doi.org/10.5194/egusphere-egu21-12567, 2021.

EGU21-10128 | vPICO presentations | ST3.2

Mesospheric Gravity Wave Momentum Flux Generated by a Thunderstorm System

Steven Smith, Martin Setvák, Yuri Yuri Beletsky, Jeffrey Baumgardner, and Michael Mendillo

An extensive and bright mesospheric gravity wave event occurred over the El Leoncito Observatory, Argentina (31.8ºS, 69.3ºW) during the night of 17–18 March 2016. The wave structures were exhibited in the nightglow and were easily visible to naked eye observers, a phenomenon known as a Bright Night. Analysis of a combination of ground-based and space-based data sources indicated that the event was generated by a large thunderstorm complex located to the south-east of the observation site. The event was associated with very large values of wave momentum flux: 150–300 m2s-2, which is over an order of magnitude larger than typical. The routine seasonality of such thunderstorm systems suggests that they may contribute significantly to the role of upward coupling to the upper atmosphere and ionosphere. 

How to cite: Smith, S., Setvák, M., Yuri Beletsky, Y., Baumgardner, J., and Mendillo, M.: Mesospheric Gravity Wave Momentum Flux Generated by a Thunderstorm System, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10128, https://doi.org/10.5194/egusphere-egu21-10128, 2021.

EGU21-14252 | vPICO presentations | ST3.2

The electrodynamic influence of thermospheric winds in the daytime ionosphere.

Thomas Immel, Brian Harding, Roderick Heelis, Astrid Maute, Jeffrey Forbes, Scott England, Stephen Mende, Christoph Englert, Russell Stoneback, Kenneth Marr, John Harlander, Jonathan Makela, and Colin Triplett

The electrodynamic influence of thermospheric winds is an effect thought to dominate the development of the daytime low-latitude ionosphere, through the generation of dynamo currents and associated vertical plasma drifts. Until recently, observations of the thermospheric and ionopsheric state variables have mainly been defined and compared on climatological time scales, due to their collection from separate observatories with disparate measurement capabilities.  These datasets are inadequate for investigation of the actual action of thermospheric drivers as they modify the ionospheric state, as the response clearly changes on 24-hour timescales, and shorter when viewed in the a constant-local-time frame of reference. New observatiions of thermospheric winds, uninterrupted over the 90-300 km altitude range, are now provided by the Ionospheric Connection Explorer along with simultaneous plasma velocity and density measurments. These observations are directly comparable to the wind measurements in crossings of the magnetic equator, where the winds are magnetically conjugate to the drift measurements. Investigation of the noon-sector drifts vs wind drivers is presented. We find that the local driver is clearly evident in the noon-time vertical plasma drifts under all conditions.

 

How to cite: Immel, T., Harding, B., Heelis, R., Maute, A., Forbes, J., England, S., Mende, S., Englert, C., Stoneback, R., Marr, K., Harlander, J., Makela, J., and Triplett, C.: The electrodynamic influence of thermospheric winds in the daytime ionosphere., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14252, https://doi.org/10.5194/egusphere-egu21-14252, 2021.

ST3.3 – Towards better understanding of the ionospheric plasma irregularities and scintillations

EGU21-9441 | vPICO presentations | ST3.3

Global Ionospheric Scintillation Model: current status and further development strategies

Dmytro Vasylyev, Yannick Beniguel, Volker Wilken, Martin Kriegel, and Jens Berdermann

When a electromagnetic wave propagates through a random inhomogeneous medium, scattering by the refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study and modelling. The Global Ionospheric Scintillation Model (GISM) is primarily intended to model the phenomena relevant for the GNSS applications and provides the amplitude and phase scintillation indices. Due to the three dimensional nature of the GISM model it is capable to describe a variety of communication geometries such as satellite-ground station or satellite-satellite communication link. Moreover, it can calculate the scintillation maps at specific altitude allowing to obtain the 3D picture of scintillation.

Recently the GISM model has been handed over to the newly established DLR Institute of Solar-Terrestrial Physics. Since then the model underwent several modernization steps. For example, the programming paradigm has been changed to the object-oriented one in order to bring more flexibility into the code.  In the present contribution we present the first results of our works and discuss strategies for further development, extension, and validation of the GISM.

How to cite: Vasylyev, D., Beniguel, Y., Wilken, V., Kriegel, M., and Berdermann, J.: Global Ionospheric Scintillation Model: current status and further development strategies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9441, https://doi.org/10.5194/egusphere-egu21-9441, 2021.

EGU21-1883 | vPICO presentations | ST3.3

Research Progresses of Ionospheric Plasma Irregularities from the Ground–Based Airglow Network in China

Jiyao Xu, Wei Yuan, Kun Wu, and Longchang Sun

China, from north to south, spans from the middle latitudes to the low latitude both in geographic latitude and geomagnetic latitude. And China has a variety of topography environment, which including high lands, plains, seas, and long coasts. To better understand topographic and latitudinal effects on the mesosphere and thermosphere and features of ionospheric plasma irregularities at various latitudes in China, we have established a ground-based airglow network in China gradually since 2010, which consists of 16 stations. This network almost cover China, which focuses on two airglow layers: the OI (~250 km) and OH (~87 km) airglow layers. The observations from OI airglow layers provide convenience to systematically investigate the morphologic feature and evolution of ionospheric plasma irregularities over China. Based on the airglow network observations, we mainly report some important research results of ionospheric plasma irregularities in recent years. These findings include (1) statistical characteristic of equatorial plasma bubble (EPB) over China, (2) the influences of severe extreme weather events on the ionosphere, (3) interaction between medium-scale traveling ionospheric disturbance (MSTIDs) and ionospheric irregularity, and (4) some new phenomena of ionospheric irregularities.

How to cite: Xu, J., Yuan, W., Wu, K., and Sun, L.: Research Progresses of Ionospheric Plasma Irregularities from the Ground–Based Airglow Network in China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1883, https://doi.org/10.5194/egusphere-egu21-1883, 2021.

EGU21-1881 | vPICO presentations | ST3.3

Equatorial Ionospheric Irregularities Observed by COSMIC 2 and GOLD Missions

Qian Wu, John Braun, William Schreiner, Sergey Sokolovskiy, Iurii Cherniak, Irina Zakharenkova, Nick Pedatella, Min-yang Chou, and Doug Hunt

Equatorial ionospheric irregularities is an important space weather phenomenon, which can disrupt GNSS and communication systems. COSMIC 2 GNSS RO observations are affected via scintillations in signal amplitudes and phases. At the same time, we can use these scintillations to monitor and geolocate the ionospheric irregularities, which are of great value to the space weather services. Geolocation of the irregularities based on the RO signals is difficult, as any irregularities along the line between the GNSS and RO satellite can cause scintillation. Several geolocation methods are known. A back propagation (BP) method to geolocate the irregularities originally developed in 2001 and applied for GPS/MET RO data is being modified and applied for COSMIC 2 scintillation data. Because the equatorial irregularities are often associated with plasma bubbles, which are visible to the NASA UV imager GOLD, we have been using the GOLD images to validate the BP geolocation method.    In this presentation, we will show the progress of recent validation effort of the BP geolocation method by comparing the COSMIC 2 geolocated irregularities with plasma bubbles in GOLD UV observations. Though, GOLD observations are only available in the American sector, COSMIC 2 observations can be used geolocate ionospheric irregularities throughout the equatorial and low latitudes

How to cite: Wu, Q., Braun, J., Schreiner, W., Sokolovskiy, S., Cherniak, I., Zakharenkova, I., Pedatella, N., Chou, M., and Hunt, D.: Equatorial Ionospheric Irregularities Observed by COSMIC 2 and GOLD Missions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1881, https://doi.org/10.5194/egusphere-egu21-1881, 2021.

EGU21-7319 | vPICO presentations | ST3.3

On the phase detrending to disentangle refraction and diffraction on GNSS signals: a case study over Antarctica

Luca Spogli, Hossein Ghobadi, Antonio Cicone, Lucilla Alfonsi, Claudio Cesaroni, Nicola Linty, Vincenzo Romano, and Massimo Cafaro

We investigate the reliability of the phase scintillation index determined by receiving Global Navigation Satellite System (GNSS) signals at ground in the high-latitudes. To the scope, we report about the capabilities of recently introduced detrending scheme based on the signal decomposition provided by the Fast Iterative Filtering (FIF) technique. This detrending scheme enables a fine tuning of the cutoff frequency for phase detrending used in the phase scintillation index definition, aimed at disentangling diffraction and refraction effects. On a single case study based on GPS and Galileo data taken by a GNSS Ionospheric Scintillation Monitor Receiver (ISMR) in Concordia Station (Antarctica), we show how the FIF-based detrending allows deriving adaptive cutoff frequencies, whose value changes minute-by-minute. They are found to range between 0.4 Hz and 1.2 Hz. This allows better accounting for diffractive effects in phase scintillation index calculation and also showing the limitations on the use of such index, being still widely used in the community, both to characterize the features of ionospheric irregularities and to adopt mitigation solutions.

How to cite: Spogli, L., Ghobadi, H., Cicone, A., Alfonsi, L., Cesaroni, C., Linty, N., Romano, V., and Cafaro, M.: On the phase detrending to disentangle refraction and diffraction on GNSS signals: a case study over Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7319, https://doi.org/10.5194/egusphere-egu21-7319, 2021.

EGU21-1897 | vPICO presentations | ST3.3

Ionospheric F-layer scintillation observations using COSMIC and COSMIC2 GPS/GNSS radio occultation data

Lung-Chih Tsai, Shin-Yi Su, and Chao-Han Liu

The FormoSat-3/ Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) has been proven a successful mission on performing active limb sounding of the ionosphere using the GPS radio occultation (RO) technique. The follow-on program called FS7/COSMIC2 is in progress with satellite launched on 25 June of 2019 and includes six low-Earth-orbit (LEO) satellites at 24°-inclination and ~720-km orbits to receive multi-channel (1.5GHz and 1.2GHz) GPS and GLONASS satellite signals. The FS7/COSMIC2 can provide about 5,000 GNSS RO observations per day which are increased by a factor of about 5 comparing to FS3/COSMIC and within the region from the geographic equator to the latitude at 40°. We process 1-Hz amplitude data and obtain complete limb-viewing profiles of the undersampling-S4 scintillation index to study global F-layer irregularity morphology. There are a few percent of FS3/COSMIC and FS7/COSMIC2 GPS/GNSS RO observations having >0.09 undersampling S4max values on average. However, seven identified areas Central Pacific Area, South American Area, African Area, European Area, Japan Sea Area, Arctic Area and Antarctic Area have been designated to have a much higher percentage of strong limb-viewing L-band scintillations. Generally, the F-layer scintillation climatology, namely, its variations with each identified zone, altitude, season, and local time have been documented. The large dataset from the FS3/COSMIC and FS7/COSMIC2 programs enable statistical studies on equatorial and low-latitude ionospheric irregularity and their models.

How to cite: Tsai, L.-C., Su, S.-Y., and Liu, C.-H.: Ionospheric F-layer scintillation observations using COSMIC and COSMIC2 GPS/GNSS radio occultation data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1897, https://doi.org/10.5194/egusphere-egu21-1897, 2021.

EGU21-3780 | vPICO presentations | ST3.3

Multiple transpolar auroral arcs reveal new insight about coupling processes in the Earth’s magnetotail

Qing-He Zhang, Yong-Liang Zhang, Chi Wang, Michael Lockwood, Hui-Gen Yang, Bin-Bin Tang, Zan-Yang Xing, Kjellmar Oksavik, Larry R. Lyons, Yu-Zhang Ma, Qiu-Gang Zong, Jøran Idar Moen, and Li-Dong Xia

A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. The formation and evolution of TPA offers clues about processes transferring energy and momentum from the solar wind to the magnetosphere and ionosphere during a northward IMF. However, their formation mechanisms remain poorly understood and controversial. We report a new mechanism identified from multiple-instrument observations of unusually bright, multiple TPAs and simulations from a high-resolution three-dimensional global MagnetoHydroDynamics (MHD) model. The observations and simulations show an excellent agreement and reveal that these multiple TPAs are generated by precipitating energetic magnetospheric electrons within field-aligned current (FAC) sheets. These FAC sheets are generated by multiple flow shear sheets in both the magnetospheric boundary produced by Kelvin-Helmholtz instability between super-sonic solar wind flow and magnetosphere plasma, and the plasma sheet generated by the interactions between the enhanced earthward plasma flows from the distant tail (less than -100 RE) and the enhanced tailward flows from the near tail (about -20 RE). The study offers a new insight into the complex solar wind-magnetosphere-ionosphere coupling processes under a northward IMF condition, and it challenges existing paradigms of the dynamics of the Earth’s magnetosphere.

How to cite: Zhang, Q.-H., Zhang, Y.-L., Wang, C., Lockwood, M., Yang, H.-G., Tang, B.-B., Xing, Z.-Y., Oksavik, K., Lyons, L. R., Ma, Y.-Z., Zong, Q.-G., Moen, J. I., and Xia, L.-D.: Multiple transpolar auroral arcs reveal new insight about coupling processes in the Earth’s magnetotail, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3780, https://doi.org/10.5194/egusphere-egu21-3780, 2021.

The magnetic and plasma observations of Low-Earth orbit (LEO) space missions represent not only the dynamical state of the ionosphere but also the physical variations of its electromagnetically connected surroundings, i.e. of the plasmasphere and magnetosphere, as well as of their driver, the solar wind. The monitoring of the ionosphere plasma variables is therefore a big asset for the study of our space environment in broad spatial region. Within the framework of the EPHEMERIS project supported by ESA, we aim at investigating two ionosphere phenomena that exhibit close relationship to global physical processes and space weather activity. We use the magnetic and plasma records of the LEO Swarm mission. First, we investigate the temporal and spatial occurrences of the mid-latitude ionosphere trough (MIT), a typical feature of the topside sub-auroral ionosphere appearing as a few degree wide depleted zone, where electron density (Ne) drops by orders of magnitude. It is shown that the locations of MITs are excellent proxies for the detection of the plasmapause position as well as of the equatorward edge of the auroral oval. Secondly, we monitor the irregular fluctuations of the magnetic field along the Swarm orbits via their intermittent behaviour. A new index called intermittency index (IMI) is introduced for the quantitative exemplification of the spatial and temporal distribution of irregular variations at the Swarm spacecraft altitudes. The paper focuses on the introduction of the methodology of IMI time-series compilation. Since IMIs are deduced via a statistical approach, we use the 50 Hz sampling frequency magnetic field records of the mission. We show that most frequently, the ionosphere magnetic field irregularities occur at low-latitudes, about the dip equator and at high latitudes, around the auroral region. It is conjectured that the equatorial events are the results of equatorial spread F (ESF) or equatorial plasma bubble (EPB) phenomena, while the auroral irregularities are related to field-aligned currents (FAC). The ionosphere plasma irregularities may result in the distortion or loss of GPS signals. Therefore our analysis also concerns the investigation of the correlation between observed intermittent events in the ionosphere and contemporary GPS signal loss events and scintillations detected both by on-board Swarm GPS receivers and ground GNSS stations.

How to cite: Kovacs, P. and Heilig, B.: Quasi real-time monitoring of the ionosphere plasma irregularities by the records of the Swarm mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16093, https://doi.org/10.5194/egusphere-egu21-16093, 2021.

EGU21-1458 | vPICO presentations | ST3.3

The influence of ionospheric neutral wind variations on the propagation of a MSTID event

Ji Luo, Jiyao Xu, Kun Wu, Wenbin Wang, Chao Xiong, and Wei Yuan

The event reports a special case of the propagation and morphology of medium scale travelling ionospheric disturbances (MSTIDs) over middle–latitude China. The MSTIDs were simultaneously observed by the all-sky imager, Swarm satellite, as well as the total electron content (TEC) from global positioning system (GPS). In addition, the MSTIDs lasted for about 6 hours of the field view of airglow imager, the continuous imagers show that the inclination angles of phase fronts were decreasing gradually during the propagation process, resulting in the propagation direction changed from southwestward to nearly westward. More interestingly, the MSTIDs began to dissipate in the airglow observation when they propagated to lower latitudes with the MSTIDs at higher latitudes still visible in the later times. The simulation results from the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) and the Fabry-Perot Interferometer (FPI) wind observations suggest that the variations of background neutral winds and the ionospheric density might play important roles in the changes of propagation direction and the dissipation of MSTIDs.

How to cite: Luo, J., Xu, J., Wu, K., Wang, W., Xiong, C., and Yuan, W.: The influence of ionospheric neutral wind variations on the propagation of a MSTID event, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1458, https://doi.org/10.5194/egusphere-egu21-1458, 2021.

EGU21-10770 | vPICO presentations | ST3.3

Spectral Properties of Kilometer-Scale Equatorial Irregularities as Seen by the Swarm Satellites

Stephan C. Buchert, Sharon Aol, and Edward Jurua

The three Swarm satellites have crossed the equator close to 80000 times each, and a large database of plasma density measurements at spatial resolution up to 500 m is available. This allows to investigate spectral properties of often seen irregularities at scale sizes of kilometers and tens of kms at heights between about 410 and 480 km above sea level. In this range of altitudes electrons are nearly completely magnetized, and ions slightly demagnetized. Therefore the irregularities could be anisotropic with a tendency to be aligned with respect to B. The satellite crossings are close to the geodetic north-south direction. Consequently the tracks of density measurement/satellite orbit have an angle with B between 0 and up to 60 deg within magnetic latitudes +/-30 degrees. Spectral properties that we have investigated are the slope of the power over wavelength, index p, and the structure function of the density. The spectral index p indicates more shallow spectra at larger angles with respect to B, in agreement with the expectation above. The spectra are also more shallow near the crests of the equatorial ionization anomaly at +/-15-20 deg magnetic latitude. This could be caused by a larger linear growth rate at these locations, which might in turn be caused by a less horizontal B.

How to cite: Buchert, S. C., Aol, S., and Jurua, E.: Spectral Properties of Kilometer-Scale Equatorial Irregularities as Seen by the Swarm Satellites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10770, https://doi.org/10.5194/egusphere-egu21-10770, 2021.

Equatorial plasma bubbles (EPBs) are typically ionospheric irregularities that frequently occur at the low latitudes and equatorial regions, which can significantly affect the propagation of radio waves. In this study, we reported a unique strong EPB that happened at middle latitudes over the Asian sector during the quiescent period. The multiple observations including total electron content (TEC) from Beidou geostationary satellites and GPS, ionosondes, in-situ electron density from SWARM and meteor radar are used to explore the characteristic and mechanism of the observed EPB. The unique strong EPB was associated with great nighttime TEC/electron density enhancement at the middle latitudes, which moves toward eastward. The potential physical processes of the observed EPB are also discussed.

How to cite: Huang, F., Lei, J., and Xiong, C.: Strong equatorial plasma bubble associated with prominent TEC enhancement observed at mid-latitude ionosphere under the quiescent condition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3832, https://doi.org/10.5194/egusphere-egu21-3832, 2021.

EGU21-6599 | vPICO presentations | ST3.3

Farley Buneman instabilities in the Auroral region: Continuous kinetic and hybrid simulations.

Enrique Rojas and David Hysell

Farley-Buneman instabilities generate a spectrum of field-aligned plasma density irregularities in the E region. Although fully kinetic particle-in-cell simulations offer a comprehensive description of the underlying physics, its computational cost for studying non-local phenomena is tremendous. New methods based on hybrid and continuous approaches have to be explored to capture non-local physics.

In this work, we present new developments on a continuous solver of Farley-Buneman waves. We compare the performance of fully kinetic (continuous), hybrid, and fluid models. Furthermore, we investigate phase speed saturation, wave turning effects, and dominant wavelengths and assess how well these correspond to radar measurements. Finally, we describe some initial attempts at constructing simple surrogate models to capture the dominant microphysics of these simulations.

How to cite: Rojas, E. and Hysell, D.: Farley Buneman instabilities in the Auroral region: Continuous kinetic and hybrid simulations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6599, https://doi.org/10.5194/egusphere-egu21-6599, 2021.

EGU21-3959 | vPICO presentations | ST3.3

The GPS Scintillations and TEC Variations in Association with A Polar Cap Arc

Yong Wang, Zheng Cao, Zan-Yang Xing, Qing-He Zhang, Periyadan T. Jayachandran, Kjellmar Oksavik, Nanan Balan, and Kazuo Shiokawa

The first example of a polar cap arc producing clear amplitude and phase scintillations in the GPS L-band is presented using observations from an all-sky imager and a GPS receiver at Resolute Bay and the SuperDARN Inuvik radar. The polar cap arc moved quickly from the dusk-side to the midnight auroral oval at a speed of ~700 m/s, as revealed by all-sky 557.7 nm and 630.0 nm images. When it intersected the ray path of GPS signals, both amplitude and phase scintillations appeared, which is very different from previous results. Moreover, the scintillations were precisely determined through power spectral analysis. We propose that the strong total electron content (TEC) enhancement (~6 TECU) and flow shears in association with the polar cap arc were causing the scintillations. It provides instructive evidence for the existence of polar cap arc scintillations that may be harmful for satellite applications even through L-band signals.

How to cite: Wang, Y., Cao, Z., Xing, Z.-Y., Zhang, Q.-H., Jayachandran, P. T., Oksavik, K., Balan, N., and Shiokawa, K.: The GPS Scintillations and TEC Variations in Association with A Polar Cap Arc, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3959, https://doi.org/10.5194/egusphere-egu21-3959, 2021.

EGU21-1864 | vPICO presentations | ST3.3

The evolution of complex Es observed by multi instruments over low-latitude China

Wenjie Sun, Baiqi Ning, Lianhuan Hu, Xiukuan Zhao, and Guozhu Li

Early and recent observations suggested that E-region field aligned irregularities (FAIs) related closely to the sporadic E (Es) layer of the ionosphere. The Sanya (18.3 ºN, 109.6 ºE) very high frequency (VHF) radar can operate at ionospheric irregularities mode for the detection of 3-m scale FAIs. The development of a portable digital ionosonde (PDI) which is collocated with the Sanya VHF radar can operate with temporal periods down to 1 minute, facilitating the capability of capturing the fast evolution of Es structures. But the low spatial resolution of the two kinds of instruments makes it difficult to depict the horizontal morphology of the Es structures and E-region FAIs. Since the capability of ground-based GNSS in strong Es detection was presented, it serves as a perfect supplement for the investigation of E region of the ionosphere. So comprehensive observation with multi kinds of instruments makes it possible to reveal the relationship and mechanisms of Es and E-region FAIs.

A complex daytime sporadic E (Es) case with extremely high critical frequency (foEs) was observed over the low latitude of China on 19 May 2018. Simultaneous observational results from two very high frequency (VHF) radars, two ionosondes, and multiple Global Navigation Satellite System total electron content and scintillation receivers are analyzed to investigate the evolution of the complex Es occurrence, which consisted of a relatively weak ambient Es layer (foEs < 8 MHz) and band-like strong Es structures (foEs > 17 MHz) drifting from higher latitude. The strong Es structures elongated more than 500 km in the northwest-southeast direction, drifted southwestward at a speed of ~65 m/s. VHF radar backscatter echoes were generated when the strong Es structures passed the radar field of view, with different echo patterns due to different radar and antenna configurations. No VHF radar backscatter echo was associated with the ambient Es layer.

How to cite: Sun, W., Ning, B., Hu, L., Zhao, X., and Li, G.: The evolution of complex Es observed by multi instruments over low-latitude China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1864, https://doi.org/10.5194/egusphere-egu21-1864, 2021.

EGU21-5554 | vPICO presentations | ST3.3

Comparisons Between E-region Coherent Scatter and Swarm-E Fast Auroral Imager Measurements

Devin Huyghebaert, Kathryn McWilliams, Glenn Hussey, Andrew Howarth, Stephanie Erion, and Paige Rutledge

The Ionospheric Continuous-wave E-region Bistatic Experimental Auroral Radar (ICEBEAR) is a VHF coherent scatter radar that makes measurements of the E-region ionosphere with a field of view centered on ≈ 58°N, 106°W.  This overlaps with the Saskatoon SuperDARN radar field of view, providing the opportunity for multi-frequency coherent scatter radar measurements in a similar region.  In conjunction with these coherent scatter radar measurements, the Swarm-E, or e-POP, satellite Fast Auroral Imager (FAI) has been used to make measurements of auroral emissions in the 650-1100 nm wavelength band over the same field of view.  The primary emission species in this wavelength range are N2, O2, and N2+, which correspond to energetic charged particle precipitation penetrating into the lower altitudes of the ionosphere.  This makes the FAI a great instrument for comparison studies with E-region coherent scatter.  In addition to this, the FAI is able to be slewed to a location allowing for extended conjunction windows between the imager and the coherent scatter radars.  With recent advances in radar hardware and processing the temporal and spatial resolutions of these different instruments are becoming comparable (~ 1 s, 1.5 km), providing an excellent opportunity to study plasma density irregularities in the E-region ionosphere in great detail.  Comparisons between the coherent scatter radar and FAI measurements are presented, providing insights into how E-region plasma density irregularities correspond to the location of auroral emissions at 650-1100 nm wavelengths.

How to cite: Huyghebaert, D., McWilliams, K., Hussey, G., Howarth, A., Erion, S., and Rutledge, P.: Comparisons Between E-region Coherent Scatter and Swarm-E Fast Auroral Imager Measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5554, https://doi.org/10.5194/egusphere-egu21-5554, 2021.

EGU21-1457 | vPICO presentations | ST3.3

Developing Equatorial Plasma Bubbles Observed by Multi-Instrument at Dawn

Kun Wu, Jiyao Xu, Xinan Yue, Chao Xiong, Wenbin Wang, Wei Yuan, Chi Wang, Yajun Zhu, and Ji luo

Previous studies have shown that equatorial plasma bubbles (EPBs) usually occur after sunset, and they usually drift eastward. Observations from an all-sky imager and the Global Navigation Satellite Systems (GNSS) network in southern China showed a special EPB event. Observational results show that the EPBs appeared near dawn and continued to develop after sunrise. They disappeared about one hour after sunrise which the life time of those EPBs exceeds 3 hours. The result provided an evidence that the EPB could develop around sunrise in optical observation. Meanwhile, those observation showed that the EPBs drifted westward, which was different from the usually eastward drifts of EPBs. The simulation from TIE-GCM model suggest that the westward drift of EPBs should be related to the enhanced westward winds at storm time. Besides, increasing in the ionospheric F region peak height was also observed near sunrise. We suggest enhance upward vertical plasma drift during geomagnetic storm plays a major role in triggering the EPBs near sunrise.

How to cite: Wu, K., Xu, J., Yue, X., Xiong, C., Wang, W., Yuan, W., Wang, C., Zhu, Y., and luo, J.: Developing Equatorial Plasma Bubbles Observed by Multi-Instrument at Dawn, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1457, https://doi.org/10.5194/egusphere-egu21-1457, 2021.

EGU21-6582 | vPICO presentations | ST3.3

Modeling and analysis of LOFAR scintillation data

Marcin Grzesiak, Mariusz Pożoga, Barbara Matyjasiak, Dorota Przepiórka, Hanna Rothkaehl, Katarzyna Budzińska, and Barbara Atamaniuk

Scintillation of beacon satellite signals or distant cosmic radio emissions can provide interesting information on the cosmic medium itself, its internal spatial structure and basic evolution characteristics. LOFAR network gives consistent scintillation data with good coverage both in time and space and for the frequency range that goes down close to the local plasma frequency (LBA) being thus sensible to ionospheric plasma irregularities. LOFAR Scintillation measurements in the LBA range exhibit very interesting morphologies. Based on scintillation simulations using the phase screen method, including multiple scattering and refraction, we try to untangle the information contained in the full range (time, space, frequency) of LOFAR data and verify a number of hypotheses about the local structure of the ionosphere and its evolution.

How to cite: Grzesiak, M., Pożoga, M., Matyjasiak, B., Przepiórka, D., Rothkaehl, H., Budzińska, K., and Atamaniuk, B.: Modeling and analysis of LOFAR scintillation data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6582, https://doi.org/10.5194/egusphere-egu21-6582, 2021.

EGU21-7964 | vPICO presentations | ST3.3

Identifying evolving/non-evolving plasma bubbles from SWARM observations

Chinmaya Nayak, Stephan Buchert, and Bharati Kakad

Equatorial plasma bubbles (EPBs) are generally caused due to the Rayleigh–Taylor instability. During the initial phase of the growth of the instability, the bubbles are associated with perturbation electric and magnetic fields. We call this the evolving (active) phase of the EPB. Over time, these electric field fluctuations decay in amplitude and the bubble, embedded in the neutral atmosphere, drifts eastward without much temporal evolution. We call this the non-evolving phase. Both phases can be distinguished in ground based VHF spaced receiver scintillation observations. In the evolving phase, the cross correlation between the signals from the two receivers is significantly less than one because of rapidly evolving perturbation electric fields. However, after some time (~2 hours) as the perturbation electric field decays, the cross correlation reaches almost 1 implying very slow temporal changes. This technique is applied to identify fresh generation of post-midnight plasma bubbles during magnetically disturbed conditions. From in situ satellite observations, the EPBs are generally identified as sudden depletion from background electron density, associated with magnetic fluctuations. In fact, the plasma bubble index produced from data of the ESA Swarm mission utilizes this same criteria of concurrent density depletions and magnetic fluctuations to identify the plasma bubbles. However, it is not so straightforward to distinguish evolving and non-evolving phases of the plasma bubbles in the SWARM plasma and magnetic observations. We look into near simultaneous in situ observations of SWARM and ground based VHF spaced receiver scintillation to identify a standard criteria for distinguishing evolving/non-evolving bubbles in SWARM observations. The results suggest that the presence/absence of magnetic fluctuations associated with the depletion in electron density can be used as a criteria for evolving/non-evolving bubbles. Ideally, the electric and magnetic field fluctuations should be present simultaneously and as a result should decay simultaneously. We have looked into one year (2014) of SWARM observations of EPBs and VHF spaced receiver scintillation data from Indian equatorial station Tirunelveli. A few case studies during both magnetically quiet and disturbed conditions are discussed.

How to cite: Nayak, C., Buchert, S., and Kakad, B.: Identifying evolving/non-evolving plasma bubbles from SWARM observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7964, https://doi.org/10.5194/egusphere-egu21-7964, 2021.

Ionospheric F‐region irregularity backscatter plumes are commonly regarded as a nighttime phenomenon at equatorial and low latitudes. At daytime, there are very few reported cases of F‐region backscatter echoes. It is still not clear what caused the daytime echoes. In order to understand the occurrence of daytime F‐region echoes, we carried out an experiment with Sanya VHF radar (18.4°N, 109.6°E, dip lat. 12.8°N) during November 2016 to August 2020. Some basic characteristics were released: (1) The daytime F‐region echoing structures have an unexpected high occurrence in June solstice of solar minimum. (2) The echoing structures could appear at any time during 0700–1800 LT, with a maximum occurrence around 0900 LT. (3) The echoing structures appeared mostly above 350 km altitude, extending up to 650 km or more (F region topside) with apparent westward drifts at times. Radar interferometry and ICON satellite in situ results show that the daytime F‐region echoes were from plume structures consisting of field‐aligned irregularities. It is suggested that the plume structures could be remnants of equatorial plasma bubble (EPB) irregularities generated on the previous night around 100–125°E. They rise to high altitudes and drift zonally together with background plasma, causing the daytime F‐region backscattering structure over Sanya. With simultaneous observations of several VHF radars at different locations, satellite in-situ measurements and/or EPB model, the dynamics of daytime F-region backscatter plume structures could be better understood in the future.

How to cite: Xie, H.: Characteristic of daytime F-region backscatter plume structures over low latitude of China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1059, https://doi.org/10.5194/egusphere-egu21-1059, 2021.

EGU21-8674 | vPICO presentations | ST3.3

TEC and Scintillations in the Ionosphere above Greenland

Sarah Beeck, Anna Jensen, and Per Knudsen

Global Navigation Satellite System (GNSS) signals are affected by the media of the ionosphere when traversing it. Therefore, near real-time monitoring of the ionosphere and its scintillation can be an advantage for GNSS users. There can be strong phase scintillation in the Arctic region, however, there is no continuous real-time monitoring of the ionosphere above Greenland at the moment. This project investigates possibilities for real-time monitoring of the ionosphere above Greenland, based on data from geodetic GNSS stations. The novelty of the work is the application of the kriging method as basis for rate of total electron content index (ROTI) maps in the Arctic.

The GNSS data analyzed in this project is from seven selected GNSS receivers that are part of the Greenland GPS Network (GNET). The data is used for computing the phase scintillation index ROTI, which is then used for mapping the scintillation activity. First the spatial data coverage was examined to investigate the possibility of visualizing the ROTI values spatially. Further, the kriging and natural neighbor methods were tested for interpolating ROTI above Greenland.

In the project there were some large spatial data gaps, caused by the sparse distribution of the GNSS receiver stations. A relation between high ROTI values and low elevation angles was shown, and this relation was more prominent at geomagnetically quiet times. This indicated that a higher elevation cut-off angle might have been useful for the mapping if more data had been available. The test of the interpolation methods lead to the conclusion that kriging provided slightly better maps than the natural neighbor method at geomagnetically active times, while natural neighbor might be preferable at geomagnetically quiet times. Finally, it was found that receivers at all of the tested latitudes were affected by ionospheric phase scintillation, this was seen as an increase in the amount of cycle slips.

The conclusions drawn from this project can help indicate what the next step should be on the path towards real-time monitoring the ionosphere above Greenland. The general recommendation for future work is to install a network of GNSS Ionospheric Scintillation and TEC Monitor (GISTM) receivers in Greenland which can provide near real-time scintillation indices.

How to cite: Beeck, S., Jensen, A., and Knudsen, P.: TEC and Scintillations in the Ionosphere above Greenland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8674, https://doi.org/10.5194/egusphere-egu21-8674, 2021.

EGU21-14374 | vPICO presentations | ST3.3

Ionospheric Scintillation observed by LOFAR PL610 station

Mariusz Pożoga, Barbara Matyjasiak, Hanna Rothkaehl, Helena Ciechowska, Marcin Grzesiak, Roman Wronowski, Katarzyna Budzińska, and Łukasz Tomasik

Due to their low intensity, ionospheric scintillations in the middle latitude region are difficult to observe. However, scintillations intensity increases at lower frequencies. Those below 90 MHz, covered by LOFAR, enable scintillation measurements in mid-latitude region. Long-term observations, with the use of PL610 station, allow the study of weak scintillation climatology, unavailable for measurement led with other methods. The developement of functional tool for the scintillation parameters analysis described in the paper enabled the study of scintillations in the mid-latitude region and future application to the data collected by LOFAR.

LOFAR PL610 station in Borowiec (23E,50N) regularly observes ionospheric scintillation using signals from the 4 strongest radio sources, members of LOFAR A-team: Cas A, Cyg A, Vir A and Tau A. The measurements are taken by LBA antennas at frequencies in the range of 10-90 MHz. Since 2018 we have collected more than 8000 hours of observations. In this work research, we present the results of the automatic s4 calculation system based on our observations. The observations are led in 4-bit mode, for 4 independent sources, with sampling of 10 Hz at 244 subbands. Sources are selected automatically depending on their visibility. Due to the fact that natural radio sources are relatively weak and beamforming is not ideal, the data are noisy. In order to improve the quality of data, the measured amplitudes are filtered and S4 index is computed for each beamlet. All processed data are stored in a database and enable in-depth analysis of scintillation behavior in the mid-latitude region.

We look at the intrinsic features of the observation: dependence on the geometry of the measurement, impact of RFI depending on the strength of the radiosource, the observation frequency then show the dependence of scintillation on the global conditions caused by space weather.

How to cite: Pożoga, M., Matyjasiak, B., Rothkaehl, H., Ciechowska, H., Grzesiak, M., Wronowski, R., Budzińska, K., and Tomasik, Ł.: Ionospheric Scintillation observed by LOFAR PL610 station, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14374, https://doi.org/10.5194/egusphere-egu21-14374, 2021.

ST4.1 – Advances in Solar Irradiance and Earth Radiation Budget Measurements

EGU21-9707 | vPICO presentations | ST4.1

The Earth energy imbalance – new advances and remaining challenges

Karina von Schuckmann

Human-induced atmospheric composition changes cause a radiative imbalance at the top of the atmosphere which is driving global warming. This simple number, the Earth energy imbalance (EEI), is the most fundamental metric that the scientific community and public must be aware of as the measure of how well the world is doing in the task of bringing climate change under control. Combining multiple measurements and approaches in an optimal way holds considerable promise for estimating EEI and continued quantification and reduced uncertainties can be best achieved through the maintenance of the current global climate observing system, its extension into areas of gaps in the sampling, advance on instrumental limitations, and the establishment of an international framework for concerted multidisciplinary research effort. This talk will provide an overview on the different approaches and their challenges for estimating the EEI. A particular emphasis will be drawn on the heat gain of the Earth system over the past half of a century – and particularly how much and where the heat is distributed – which is fundamental to understanding how this affects warming ocean, atmosphere and land; rising surface temperature; sea level; and loss of grounded and floating ice, which are critical concerns for society.

 

How to cite: von Schuckmann, K.: The Earth energy imbalance – new advances and remaining challenges, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9707, https://doi.org/10.5194/egusphere-egu21-9707, 2021.

EGU21-13183 | vPICO presentations | ST4.1

Libera and Continuity of the Earth Radiation Budget Climate Data Record

Peter Pilewskie and Maria Hakuba and the Libera Science Team

The NASA Libera Mission, named for the daughter of Ceres in Roman mythology, will provide continuity of the Clouds and the Earth’s Radiant Energy System (CERES) Earth radiation budget (ERB) observations from space. Libera’s  attributes enable a seamless extension of the ERB climate data record. Libera will acquire integrated radiance over the CERES FM6-heritage broad spectral bands in the shortwave (0.3 to 5 μm), longwave (5 to 50 μm) and total (0.3 to beyond 100 μm) and adds a split-shortwave band (0.7 to 5 μm) to provide deeper insight into shortwave energy deposition. Libera leverages advanced detector technologies using vertically aligned black-carbon nanotubes with closed-loop electrical substitution radiometry to achieve radiometric uncertainty of approximately 0.2%. Libera will also employ a wide field-of-view camera to provide scene context and explore pathways for separating future ERB missions from complex imagers.

The Libera science objectives associated with continuity and extension of the ERB data record are to identify and quantify processes responsible for ERB variability on various time scales. Beyond data continuity, Libera’s new and enhanced observational capabilities will advance our understanding of spatiotemporal variations of radiative energy flow in the visible and and near-infrared spectral regions. They will also enable the rapid development of angular distribution models to facilitate near-IR and visible radiance-to-irradiance conversion.

How to cite: Pilewskie, P. and Hakuba, M. and the Libera Science Team: Libera and Continuity of the Earth Radiation Budget Climate Data Record, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13183, https://doi.org/10.5194/egusphere-egu21-13183, 2021.

EGU21-9579 | vPICO presentations | ST4.1

Comparison Between POLDER/PARASOL and CERES/AQUA Shortwave Fluxes

Simonne Guilbert, Frédéric Parol, Céline Cornet, Nicolas Ferlay, and François Thieuleux

Radiative Budget, essential to the monitoring of climate change, can be investigated with ERB-dedicated instruments like the Clouds and the Earth Radiant Energy System (CERES) instrument (Wielicki, 1996). On the other side, non-dedicated instruments, such as POLDER-3/PARASOL measuring narrowband radiances, can also be used advantageously to obtain shortwave albedos and fluxes (Buriez et al, 2007; Viollier et al, 2002).

We present here a comparison between the shortwave fluxes and albedos derived from POLDER-3 and those derived from CERES flying aboard Aqua, chosen as a reference.

Monthly means of shortwave fluxes computed from the measurements of the two instruments are first set side by side. They show a good agreement in the all-sky case. However, after December 2009, the values from POLDER-3 display a slight drift which coincides with the lowering of the orbit of the PARASOL satellite and the modification of its overpass time in comparison to the other satellites of the A-Train mission. In clear sky situations, greater differences between POLDER and CERES shortwave fluxes are observed, especially over land regions, and the drift increases faster after 2009.

A second comparison is presented, between instantaneous albedos. For the period of coincident observations between POLDER-3 and CERES/Aqua, there is a good correlation between both products. This correlation deteriorates when the comparison is extended after 2009, as the values given by POLDER-3 increase. This result is expected, as the albedo is a function of the Solar Zenith Angle.

The slope of the increase of instantaneous albedo values is higher than for the diurnally extrapolated, monthly averaged shortwave fluxes. This tends to show that the POLDER algorithm leading to the monthly means of diurnal shortwave albedos moderates the increase of instantaneous shortwave albedo values but it doesn’t completely compensate for the effects of the drift of the instrument.

 

How to cite: Guilbert, S., Parol, F., Cornet, C., Ferlay, N., and Thieuleux, F.: Comparison Between POLDER/PARASOL and CERES/AQUA Shortwave Fluxes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9579, https://doi.org/10.5194/egusphere-egu21-9579, 2021.

EGU21-5980 | vPICO presentations | ST4.1

Preliminary results of relative radiometer to measure the Earth’s outgoing radiation on FY-3F satellite

Duo Wu, Ping Zhu, Wei Fang, Xin Ye, Kai Wang, Ruidong Jia, Zhiwei Xia, Dongjun Yang, and Cong Zhao

A space based relative radiometer has been developed and applied to the PICARD mission. It has successfully measured 37 months solar radiation, terrestrial outgoing radiation, and a comparable interannual variation in Earth Radiation Budget (ERB) is inferred from those measurements [1]. However, since the BOS (Bolometric Oscillation Sensor [2]) relative radiometer is originally designed to measure the solar irradiance with 10 seconds high cadence comparing to the absolute radiometer. The high dynamic range of BOS limits its performance to track the Earth’s outgoing radiation in terms of instantaneous field-of-view (iFOV) and the absolute radiation level. Two relative radiometers (RR) will be developed for JTSIM/FY-3F. One is the solar channel relative radiometer aimed to measure the solar irradiance side by side with the cavity solar irradiance absolute radiometer (SIAR). The second RR is acting as a non-scanner instrument to measure the Earth’s outgoing radiation. Comparing to the design of PICRD-BOS. Each RR has included an aperture, for the solar channel it limits its Unobstructed Field of View (UFOV) to about 1.5 degree and for the Earth channel to about 110 degrees, respectively. We also test the possibility to use the Carbon Nanotube coating on the main detector. In this presentation, the design of the earth channel relative radiometer (ERR) will be introduced, including the aperture design, dynamic range and the active temperature control system. The preliminary laboratory test result of the ERR will be discussed in the end.

[1] P. Zhu, M. Wild, M. van Ruymbeke, G. Thuillier, M. Meftah, and Ö. Karatekin. Interannual variation of global net radiation flux as measured from space. J. Geophys. Res. doi:10.1002/2015JD024112, 121:6877–6891, 2016.

[2] P. Zhu, M.van Ruymbeke, Ö. Karatekin, J.-P.Noël, G. Thuillier, S. Dewitte, A. Chevalier, C. Conscience, E. Janssen, M. Meftah, and A. Irbah. A high dynamic radiation measurement instrument: the bolometric oscillation sensor (bos). Geosci. Instrum. Method. Data Syst., 4,89-98,:doi:10.5194/gi–4–89–2015, 2015.

Acknowledgement: this work is partly supported by the National Natural Science Foundation of China No. 41974207 and CSC Scholarship No.202004910181

 

How to cite: Wu, D., Zhu, P., Fang, W., Ye, X., Wang, K., Jia, R., Xia, Z., Yang, D., and Zhao, C.: Preliminary results of relative radiometer to measure the Earth’s outgoing radiation on FY-3F satellite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5980, https://doi.org/10.5194/egusphere-egu21-5980, 2021.

EGU21-10348 | vPICO presentations | ST4.1

GOES High cadence Operational Total Irradiance: planned data products

Martin Snow, Stephane Beland, Odele Coddington, Steven Penton, and Don Woodraska

The GOES-R series of satellites includes a redesigned instrument for solar spectral irradiance: the Extreme ultraviolet and X-ray Irradiance Sensor (EXIS).  Our team will be using a high-cadence broadband visible light diode to construct a proxy for Total Solar Irradiance (TSI).  This will have two advantages over the existing TSI measurements:  measurements are taken at 4 Hz, so the cadence of our TSI proxy is likely faster than any existing applications, and the observations are taken from geostationary orbit, so the time series of measurements is virtually uninterrupted.  Calibration of the diode measurements will still rely on the standard TSI composites.  

The other measurement from EXIS that will be used is the Magnesium II core-to-wing ratio.  The MgII index is a proxy for chromospheric activity, and is measured by EXIS every 3 seconds.  The combination of the two proxies can be used to generate a model of the full solar spectrum similar to the NRLSSI2 empirical model.

We are in the first year of a three-year grant to develop the TSI proxy and the SSI model, so only very preliminary findings will be discussed in this presentation.

How to cite: Snow, M., Beland, S., Coddington, O., Penton, S., and Woodraska, D.: GOES High cadence Operational Total Irradiance: planned data products, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10348, https://doi.org/10.5194/egusphere-egu21-10348, 2021.

EGU21-4382 | vPICO presentations | ST4.1

Data Fusion of Total Solar Irradiance Composite Time Series Using 40 years of Satellite Measurements: First Results 

Jean-Philippe Montillet, Wolfgang Finsterle, Werner Schmutz, Margit Haberreiter, and Rok Sikonja

Since the late 70’s, successive satellite missions have been monitoring the sun’s activity, recording total solar irradiance observations. These measurements are important to estimate the Earth’s energy imbalance, i.e. the difference of energy absorbed and emitted by our planet. Climate modelers need the solar forcing time series in their models in order to study the influence of the Sun on the Earth’s climate. With this amount of TSI data, solar irradiance reconstruction models  can be better validated which can also improve studies looking at past climate reconstructions (e.g., Maunder minimum). Various algorithms have been proposed in the last decade to merge the various TSI measurements over the 40 years of recording period. We have developed a new statistical algorithm based on data fusion.  The stochastic noise processes of the measurements are modeled via a dual kernel including white and coloured noise.  We show our first results and compare it with previous releases (PMOD,ACRIM, ... ). 

How to cite: Montillet, J.-P., Finsterle, W., Schmutz, W., Haberreiter, M., and Sikonja, R.: Data Fusion of Total Solar Irradiance Composite Time Series Using 40 years of Satellite Measurements: First Results  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4382, https://doi.org/10.5194/egusphere-egu21-4382, 2021.

EGU21-12777 | vPICO presentations | ST4.1

Extending the TSIS-1 Hybrid Solar Reference Spectrum (HSRS) to Span 0.202 to 200 um

Odele Coddington, Erik Richard, Dave Harber, Peter Pilewskie, Tom Woods, Kelly Chance, Xiong Liu, and Kang Sun

Recently, we incorporated our new understanding of the absolute scale of the solar spectrum as measured by the Spectral Irradiance Monitor (SIM) on the Total and Spectral Solar Irradiance Sensor (TSIS-1) mission and the Compact SIM (CSIM) flight demonstration into a solar irradiance reference spectrum representing solar minimum conditions between solar cycles 24 and 25. This new reference spectrum, called the TSIS-1 Hybrid Solar Reference Spectrum (HSRS), is developed by re-normalizing independent, very high spectral resolution datasets to the TSIS-1 SIM absolute irradiance scale. The high-resolution data are from the Airforce Geophysical Laboratory (AFGL), the Quality Assurance of Ultraviolet Measurements In Europe (QASUME) campaign, the Kitt Peak National Observatory (KPNO) and the Jet Propulsion Laboratory’s (JPL) Solar Pseudo-Transmittance Spectrum (SPTS). The TSIS-1 HSRS spans 0.202 µm to 2.73 µm and has a spectral resolution of 0.01 nm or better. Uncertainties are 0.3% between 0.4 and 2.365 mm and 1.3% at wavelengths outside that range

Recently, we have extended the long wavelength limit of the TSIS-1 HSRS from 2.73 µm to 200 µm with JPL SPTS solar line data through ~ 16 µm and theoretical understanding as represented in a computed solar irradiance spectrum by R. Kurucz. The extension expands the utility of this new solar irradiance reference spectrum to include Earth energy budget studies because it encompasses an integrated energy in excess of 99.99% of the total solar irradiance.

In this work, we discuss the TSIS-1 HSRS, the extension and uncertainties, and demonstrate consistency with TSIS-1 SIM and CSIM solar spectral irradiance observations and TSIS-1 Total Irradiance Monitor (TIM) total solar irradiance observations. Additionally, we compare the TSIS-1 HSRS against independent measured and modeled solar reference spectra.

How to cite: Coddington, O., Richard, E., Harber, D., Pilewskie, P., Woods, T., Chance, K., Liu, X., and Sun, K.: Extending the TSIS-1 Hybrid Solar Reference Spectrum (HSRS) to Span 0.202 to 200 um, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12777, https://doi.org/10.5194/egusphere-egu21-12777, 2021.

EGU21-7263 | vPICO presentations | ST4.1

Annual Changes in the spectrally resolved global and local Earth Energy Imbalance using the Sun as a Reference Radiation Source

Gerhard Schmidtke, Wolfgang Finsterle, Gerard Thullier, Ping Zhu, Michel Ruymbeke, Raimund Brunner, and Christoph Jacobi

A new method is presented to derive spectrally resolved global and local annual changes in the Earth Energy Imbalance (ΔEEI(λ, Δλ)) from measurements of Total and Spectral Solar Irradiance (TSI and SSI) and Total Outgoing Radiation (TOR) and the Spectral Outgoing Radiation (SOR) of the Earth. Since TSI space radiometers provide data with a long-term absolute accuracy <0.1 W m-2, the Sun should be used as a TSI referenced radiation source to obtain SSI data using the method of the Solar Auto-Calibrating XUV-IR Spectrometer (SOLACER). By repeatedly calibrating the solar and Earth observation instruments, the degradation should be compensated to accurately determine the outgoing flux Φ(λ, Δλ) entering the instrument. If the instruments on a pointing device are moved within the Angular Range of Sensitivity (ARS) in two angular dimensions through the solar disk, the instruments are also regularly calibrated with regard to their dependence of the angular sensitivity. ARS is independent of the environmental conditions. To improve the accuracy of SOR data, a normalization factor Ωa / ARS is used to extend the annual averaged outgoing flux data Φ(λ, Δλ)a to the SOR(λ, Δλ)a. The strength of the method is demonstrated by describing space-evaluated instruments to be adapted for solar and/or Earth observation from a small satellite. In the spectral range from 120 nm to 3000 nm, spectrometers and highly sensitive photometers with signal-to-noise ratios >1:107 are described to generate data records with high statistical accuracy. Given the compactness of the instruments, more than 20 different data sets should be compiled to complement, verify each other and improve accuracy.

 

How to cite: Schmidtke, G., Finsterle, W., Thullier, G., Zhu, P., Ruymbeke, M., Brunner, R., and Jacobi, C.: Annual Changes in the spectrally resolved global and local Earth Energy Imbalance using the Sun as a Reference Radiation Source, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7263, https://doi.org/10.5194/egusphere-egu21-7263, 2021.

EGU21-5104 | vPICO presentations | ST4.1

Thermal simulation of cavity shape and its impact on solar and terrestrial radiation measurement in space

Xiao Tang, Ping Zhu, and Marta Goli

In order to upgrade the technology readiness lever of the solar and terrestrial radiation measurement from space, in this paper, we started detailed thermal analysis and modeling of the Bolometric Oscillation Sensor (BOS) using the finite element method (FEM) [1]. Four cavity shapes (cylindrical, conical, inverted conical and hemispherical) are tested to compare their thermal and optical characteristics under different radiation and thermal environment, which helps to gain a better understanding of the mechanisms of BOS. We examined the absorptivity and emissivity of each cavity shape by applying the same amount of radiation power. Especially, when the ambient temperature maintains at a stable and low value, such as 20K, it produces the most accurate reconstruction of the input power. In this presentation, we will introduce the detailed simulation result and how to apply it to correct the ambient thermal radiation on each type of detector.

Reference:

[1] P. Zhu, M. Wild, M. van Ruymbeke, G. Thuillier, M. Meftah, and O. Karatekin. Interannual variation of globe net radiation flux as measured from space. J. Geophys. Res. doi:10.1002/2015JD024112, 121:6877-6891, 2016.

Acknowledgement: This work has been supported by the National Natural Science Foundation of China (NO. 41904163, 41974207), Natural Science Foundation of Hunan Province (NO. 2020JJ5483), and Research Foundation of Education Bureau of Hunan Province (NO. 18C0416). We also thank the financial support from China Scholarship Council (No. 201908430058).

How to cite: Tang, X., Zhu, P., and Goli, M.: Thermal simulation of cavity shape and its impact on solar and terrestrial radiation measurement in space, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5104, https://doi.org/10.5194/egusphere-egu21-5104, 2021.

EGU21-15391 | vPICO presentations | ST4.1

How to calibrate a solar radiometer

Wolfgang Finsterle, Margit Haberreiter, and Jean-Philippe Montillet

Solar radiometers are deployed in many locations on the ground and in space. The radiometers in space are measuring the solar energy input into the Earth system per time and unit area, also known as the Total Solar Irradiance (TSI). TSI radiometers are also used to calibrate Earth Observation instruments and to measure the Total Outgoing Radiation (TOR) at the top of the atmosphere, which is a key component in the Earth Radiation Budget (ERB). Ground-based solar radiometers measure the local irradiance levels, which are used for monitoring of atmospheric properties and solar energy applications.

Traceability of the radiation measurements to SI units is crucial in all of these applications. However, calibrating and characterising a solar radiometer is a technically challenging task. Depending on the requirements for a specific application, different calibration concepts can be employed in the calibration and characterization process.

We will present the currently available calibration concepts, their advantages and disadvantages, and put special focus on recent technical developments, such as the cryogenic standard radiometers for solar irradiance on the ground and in space.

How to cite: Finsterle, W., Haberreiter, M., and Montillet, J.-P.: How to calibrate a solar radiometer, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15391, https://doi.org/10.5194/egusphere-egu21-15391, 2021.

EGU21-6437 | vPICO presentations | ST4.1

TSI and TOR measurements with CLARA onboard NorSat-1

Margit Haberreiter, Wolfgang Finsterle, Jean-Philippe Montillet, Benjamin Walter, Bo Andersen, and Werner Schmutz

Total Solar Irradiance (TSI) is one of the Essential Climate Variables (ECV) identified by the World Meteorological Organization's Global Climate System (GCOS). The Compact Lightweight Absolute RAdiometer (CLARA) experiment onboard the Norwegian micro satellite NorSat-1 is a SI traceable radiometer and was launched July 14, 2017 with the primary science goal to measure TSI from space. We present the latest status of the data and degradation correction obtained with this SI-traceable radiometer. Besides TSI, CLARA also measures the total outgoing radiation (TOR) at the top of the Earth atmosphere on the night side of Earth, which is extremely important to understand the Earth Radiation Budget. It is to our knowledge the first time that TSI and the emitted radiation from Earth are measured simultaneously with one SI-traceable absolute radiometer. We will compare the CLARA TSI and TOR time series with other available datasets. Ultimately, we aim towards determining the Earth Energy Imbalance from space. We will discuss the achievements and limitations in direction of this goal.

How to cite: Haberreiter, M., Finsterle, W., Montillet, J.-P., Walter, B., Andersen, B., and Schmutz, W.: TSI and TOR measurements with CLARA onboard NorSat-1, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6437, https://doi.org/10.5194/egusphere-egu21-6437, 2021.

ST4.2 – Nowcasting, forecasting, operational monitoring and post-event analysis of the space weather and space climate in the Sun-Earth system

EGU21-15965 | vPICO presentations | ST4.2

Global estimation of ionospheric drivers during extreme storms

Aurora Lopez Rubio, Seebany Datta-Barua, and Gary Bust

During geomagnetic storms, the space environment can be drastically altered as the plasma in the upper atmosphere, or ionosphere, moves globally. This plasma redistribution is mainly caused by storm-time electric fields, but another important driver of the velocity of the ions in the plasma is the neutral winds. These winds refer to the movement of the neutral particles that are part of the thermospheric layer of the atmosphere, that can drag the plasma. Geomagnetic storms increase the neutral winds, due to the heating of the thermosphere that comes from the storm. In this study we want to understand how these ionospheric drivers affect the ionosphere behavior because, among other reasons, during geomagnetic storms the plasma can refract and diffract trans-ionospheric signals and, consequently, can cause problems in the navigation systems such as GNSS (Global Navigation Satellite System)/GPS (Global Positioning System) that use the information from the signals.

In this work, our objective is to estimate the electric fields and neutral winds globally during a geomagnetic storm. Global GNSS TEC (total electron content) measurements are ingested by the Ionospheric Data Assimilation 4-Dimensional (IDA4D) algorithm [1], whose output is the electron density rate over a grid at different time steps during a geomagnetic storm. The density rates are treated as “observations” in EMPIRE (Estimating Model Parameters from Ionospheric Reverse Engineering), which is a data assimilation algorithm based on the plasma continuity equation [2,3,4]. Then, the EMPIRE “observations” are used to estimate corrections to the electric field and neutral winds by solving a Kalman filter. To study these drivers with EMPIRE, basis functions are used to describe them. For the global potential field, spherical harmonics are used.

To have a global estimation of the neutral winds, we introduce vector spherical harmonics as the basis function for the first time in EMPIRE. The vector spherical harmonics are used to model orthogonal components of neutral wind in the zonal (east-west) and meridional (north-south) directions. EMPIRE’s Kalman filter needs the error covariance of the vector spherical harmonics decomposition. To calculate it, the basis function is fitted to the model HWM14 (Horizonal Wind Model) values of the neutral winds and the error between the fitting and the model is studied. Later, we study the global potential field and global neutral winds over time to understand how much each driver contributes to the plasma redistribution during the geomagnetic storm on October 25th 2011. We compare the results to FPI (Fabry-Perot Interferometer) neutral winds measurements to validate the results.   

[1] G.S.Bust, G.Crowley, T.W.Garner, T.L.G.II, R.W.Meggs, C.N.Mitchell, P.S.J.Spencer, P.Yin, and B.Zapfe, Four-dimensional gps imaging of space weather storms, Space Weather, 5 (2007),  doi:10.1029/2006SW000237.

[2] D.S.Miladinovich, S.Datta-Barua, G.S.Bust, and J.J.Makela, Assimilation of thermospheric measurements for ionosphere-thermosphere state estimation, Radio Science, 51 (2016).

[3] D.S.Miladinovich, S.Datta-Barua, A.Lopez, S. Zhang, and G.S.Bust, Assimilation of gnss measurements for estimation of high-latitude convection processes, Space Weather, 18 (2020).

[4] G.S.Bust and S.Datta-Barua, Scientific investigations using ida4d and empire, in Modeling the Ionosphere-Thermosphere System, J. Huba, R. Schunk, and G. Khazanov, eds., John Wiley & Sons, Ltd, 1 ed., 2014.

How to cite: Lopez Rubio, A., Datta-Barua, S., and Bust, G.: Global estimation of ionospheric drivers during extreme storms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15965, https://doi.org/10.5194/egusphere-egu21-15965, 2021.

EGU21-5718 | vPICO presentations | ST4.2

Predictability of Ionosphere using Assimilative Empirical Model IRTAM

Ivan Galkin, Artem Vesnin, Bodo Reinisch, and Dieter Bilitza

Real-time assimilative empirical models based on the International Reference Ionosphere (IRI) [1], a 3D quiet-time climatology model of the ionospheric plasma density, provide prompt weather specification by adjusting IRI definitions into a better match with the available measurements and geospace activity indicators [2]. The IRI-based Real-Time Assimilative Model (IRTAM) [3] is one of such Real-Time IRI operational ionospheric weather models based on the low-latency sensor inputs from the Global Ionosphere Radio Observatory (GIRO) [4].

IRTAM leverages predictive properties of the underlying IRI expansion basis formalism [5] that treats dynamics of the ionospheric plasma in terms of its harmonics, both temporal and spatial. It uses Non-linear Error Compensation Technique with Associative Restoration (NECTAR) technique [6] to first detect multi-scale inherent diurnal periodicity of the differences between GIRO measurements and the underlying IRI climatology. Then, under the assumption that variations in time at periodic, planetary-scale Eigen scales (diurnal, half-diurnal, 8-hour, etc.) translate to their spatial properties, it globally interpolates and extrapolates each diurnal harmonic individually. This approach allowed NECTAR to associate observed fragments of the activity at GIRO locations with the unveiling grand-scale weather processes of the matching variability scales, as the ground observatories co-rotate with the Earth.

Predictive properties of IRTAM are discussed in order to establish the baseline predictability of the ionospheric dynamics that analyzes only the latest 24-hour history of its deviation from the expected behavior. Concepts for the next generation empirical forecast models are outlined that would leverage the same principle of associative restoration to evaluate the geospace activity timeline and its subtle associations with subsequent storm-time behavior of the ionosphere.

References

[1] Bilitza, D. (ed.) (1990), International Reference Ionosphere 1990, 155 pages, National Space Science Data Center, NSSDC/WDC-A-R&S 90-22, Greenbelt, Maryland, November 1990.

[2] Bilitza, D., D. Altadill, V. Truhlik, V. Shubin, I. Galkin, B. Reinisch, and X. Huang (2017), International Reference Ionosphere 2016: From ionospheric climate to real-time weather predictions, Space Weather, 15, 418-429, doi:10.1002/2016SW001593.

[3] Galkin, I. A., B. W. Reinisch, X. Huang, and D. Bilitza (2012), Assimilation of GIRO Data into a Real-Time IRI, Radio Sci., 47, RS0L07, doi:10.1029/2011RS004952.

[4] Reinisch, B.W. and I.A. Galkin (2011), Global Ionospheric Radio Observatory (GIRO), Earth Planets Space, vol. 63 no. 4 pp. 377-381, doi:10.5047/eps.2011.03.001

[5] International Telecommunications Union (2009), ITU-R reference ionospheric characteristics, Recommendation P.1239-2 (10/2009). Retrieved from http://www.itu.int/rec/R-REC-P.1239/en.

[6] Galkin, I. A., B. W. Reinisch, A. Vesnin, et al., (2020) Assimilation of Sparse Continuous Near-Earth Weather Measurements by NECTAR Model Morphing, Space Weather, 18, e2020SW002463, doi:10.1029/2020SW002463.

How to cite: Galkin, I., Vesnin, A., Reinisch, B., and Bilitza, D.: Predictability of Ionosphere using Assimilative Empirical Model IRTAM, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5718, https://doi.org/10.5194/egusphere-egu21-5718, 2021.

EGU21-7393 | vPICO presentations | ST4.2

Modeling of TEC over the Iberian Peninsula using PCA decomposition and multiple linear regression on space weather parameters

Anna Morozova, Tatiana Barlyaeva, and Teresa Barata

The total electron content (TEC) over the Iberian Peninsula was modeled using a three-step procedure. At the 1st step the TEC series is decomposed using the principal component analysis (PCA) into several daily modes. Then, the amplitudes of those daily modes is fitted by a multiple linear regression model (MRM) using several types of space weather parameters as regressors. Finally, the TEC series is reconstructed using the PCA daily modes and MRM fitted amplitudes.

The advantage of such approach is that seasonal variations of the TEC daily modes are automatically extracted by PCA. As space weather parameters we considered proxies for the solar UV and XR fluxes, number of the solar flares, parameters of the solar wind and the interplanetary magnetic field, and geomagnetic indices. Different time lags and combinations of the regressors are tested.

The possibility to use such TEC models for forecasting was tested. Also, a possibility to use neural networks (NN) instead of MRM is studied.

How to cite: Morozova, A., Barlyaeva, T., and Barata, T.: Modeling of TEC over the Iberian Peninsula using PCA decomposition and multiple linear regression on space weather parameters, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7393, https://doi.org/10.5194/egusphere-egu21-7393, 2021.

EGU21-721 | vPICO presentations | ST4.2

The future location of auroral zones as described by the geomagnetic field of internal origin

Stefano Maffei, Philip Livermore, and Jonathan Mound

The internal component of the geomagnetic field (generated within the Earth's core) is of crucial importance in modulating the impact of space weather events. Although primarily a dipolar field of slowly decreasing intensity, multipolar components can cause changes on interannual time-scales that are important for space weather applications. Of particular importance for space weather application is the location of the auroral oval, the region where it is most likely to see polar auroras. The auroral zone can be defined as a time-averaged auroral oval and it is possible to describe it via the internal geomagnetic field.

To be able to forecast interannual and decadal changes of the auroral oval location can benefit the design of future space missions and the planning of mitigation strategies for countries particularly exposed to severe space weather events (such as the UK).

Here we combine various future evolution scenarios for the geomagnetic field of internal origin with a definition of the auroral zones that rests on the calculation of non-orthogonal, magnetic coordinates. This methodology agrees well with calculations based on more complete magnetospheric and ionospheric physics. We apply our methodology to derive quantitative forecasts for the auroral zones' location over the next decades. 

How to cite: Maffei, S., Livermore, P., and Mound, J.: The future location of auroral zones as described by the geomagnetic field of internal origin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-721, https://doi.org/10.5194/egusphere-egu21-721, 2021.

EGU21-10501 | vPICO presentations | ST4.2

Probabilistic Geomagnetic Storm Forecasting via Deep Learning

Adrian Tasistro-Hart, Alexander Grayver, and Alexey Kuvshinov

By causing time variation in Earth's external magnetic field, geomagnetic storms can induce damaging currents in ground-based conducting infrastructure, such as power and communication lines.  The physical link between solar activity and Earth's magnetosphere, while complicated, provides the basis for attempts to forecast geomagnetic storms. Fortunately, we have abundant observational data of both the solar disk and solar wind, which are ameable to the application of data-hungry neural networks to the forecasting problem. To date, almost all neural networks trained for geomagnetic storm forecasting have utilized solar wind observations from the Earth-Sun first Lagrangian point (L1) or closer and have generated deterministic output without uncertainty estimates. Furthermore, existing models generate forecasts for indices that are also sensitive to induced internal magnetic fields, complicating the forecasting problem with another layer of non-linearity. In this work, we present neural networks trained on observations from both the solar disk and the L1 point. Our architecture generates reliable probabilistic forecasts over Est, the external component of the disturbance storm time index, showing that neural networks can learn measures of confidence in their output. 

How to cite: Tasistro-Hart, A., Grayver, A., and Kuvshinov, A.: Probabilistic Geomagnetic Storm Forecasting via Deep Learning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10501, https://doi.org/10.5194/egusphere-egu21-10501, 2021.

EGU21-2771 | vPICO presentations | ST4.2

Improving solar wind forecasting using Data Assimilation

Matthew Lang, Jake Witherington, Harriet Turner, Mathew Owens, and Pete Riley

In terrestrial weather prediction, Data Assimilation (DA) has enabled huge improvements in operational forecasting capabilities. It does this by producing more accurate initial conditions and/or model parameters for forecasting; reducing the impacts of the “butterfly effect”. However, data assimilation is still in its infancy in space weather applications and it is not quantitatively understood how DA can improve space weather forecasts.

To this effect, we have used a solar wind DA scheme to assimilate observations from STEREO A, STEREO B and ACE over the operational lifetime of STEREO-B (2007-2014). This scheme allows observational information at 1AU to update and improve the inner boundary of the solar wind model (at 30 solar radii). These improved inner boundary conditions are then input into the efficient solar wind model, HUXt, to produce forecasts of the solar wind over the next solar rotation.

In this talk, I will be showing that data assimilation is capable of improving solar wind predictions not only in near-Earth space, but in the whole model domain, and compare these forecasts to corotation of observations from STEREO-B at Earth. I will also show that the DA forecasts are capable of reducing systematic errors that occur to latitudinal offset in STEREO-B’s corotation forecast.

How to cite: Lang, M., Witherington, J., Turner, H., Owens, M., and Riley, P.: Improving solar wind forecasting using Data Assimilation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2771, https://doi.org/10.5194/egusphere-egu21-2771, 2021.

EGU21-9995 | vPICO presentations | ST4.2

Deep Neural Networks With Convolutional and LSTM Layers for SYM-H and ASY-H Forecasting

Armando Collado, Pablo Muñoz, and Consuelo Cid

Geomagnetic indices quantify the disturbance caused by the solar activity in particular regions of the Earth. Among them, the SYM-H and ASY-H indices represent the (longitudinally) symmetric and asymmetric geomagnetic disturbance of the horizontal component of the magnetic field at mid-latitude with a 1-minute resolution. Their resolution, along with their relation to the solar wind parameters, makes the forecasting of the geomagnetic indices a problem that can be addressed through the use of Deep Learning, particularly using Deep Neural Networks (DNN). In this work, we present two DNNs developed to forecast the SYM-H and ASY-H indices. Both networks have been trained using solar wind data from the last two solar cycles and they are able to accurately forecast the indices two hours in advance, considering the solar wind and indices values for the previous 16 hours. The evaluation of both networks reveals a great precision for the forecasting, including good predictions for large storms that occurred during the solar cycle 23.

How to cite: Collado, A., Muñoz, P., and Cid, C.: Deep Neural Networks With Convolutional and LSTM Layers for SYM-H and ASY-H Forecasting, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9995, https://doi.org/10.5194/egusphere-egu21-9995, 2021.

EGU21-10107 | vPICO presentations | ST4.2

Sunspot Classifications & Solar Flare Prediction: Does machine learning improve upon Poisson-based prediction models?

Aoife McCloskey, Shaun Bloomfield, and Peter Gallagher

Historically, McIntosh classifications of sunspots have been utilised for the prediction of solar flares, with modern day operational flare forecast services still reliant upon these classifications for their predictions. Here, building upon previous Poisson-based flare forecasting models that make use of Mcintosh classifications, a set of various machine learning (ML) techniques are applied to construct a set of new models to predict flares within a 24-hr period.

These ML algorithms are trained and tested using data from a range of independent solar cycle periods, cross-validation techniques are applied and the relative performance of each algorithm is compared. In order to make a direct comparison to Poisson-based forecasts, skill scores are calculated and the performance of each model is presented, results showing that the ML models perform well across multiple metrics. The implications these results have when compared with the previous Poisson-based approach are discussed as well as the problem of solar cycle dependence. Additionally, an exploration of the importance of the individual features (i.e., McIntosh components) on the performance of each prediction model and their physical implications are presented.

How to cite: McCloskey, A., Bloomfield, S., and Gallagher, P.: Sunspot Classifications & Solar Flare Prediction: Does machine learning improve upon Poisson-based prediction models?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10107, https://doi.org/10.5194/egusphere-egu21-10107, 2021.

EGU21-1393 | vPICO presentations | ST4.2

The effects of solar flare-driven ionospheric electron density change on Doppler Flash

Shibaji Chakraborty, Liying Qian, J. Michael Ruohoniemi, Joseph Baker, and Joseph McInerney

Trans–ionospheric high frequency (HF) signals experience a strong attenuation following a solar flare, commonly referred to as Short–Wave Fadeout (SWF). Although solar flare-driven HF absorption is a well-known impact of SWF, the occurrence of a frequency shift on radio wave signal traversing the lower ionosphere in the early stages of SWF, also known as "Doppler Flash", is newly reported and not well understood. Some prior investigations have suggested two possible sources that might contribute to the manifestation of Doppler Flash: first,  enhancements of plasma density in the D and lower E regions; second, the lowering of the reflection point in the F region. Observations and modeling evidence regarding the manifestation and evolution of Doppler Flash in the ionosphere are limited. This study seeks to advance our understanding of the initial impacts of solar flare-driven SWF. We use WACCM-X to estimate flare-driven enhanced ionization in D, E, and F-regions and a ray-tracing code (Pharlap) to simulate a 1-hop HF communication through the modified ionosphere. Once the ray traveling path has been identified, the model estimates the Doppler frequency shift along the ray path. Finally, the outputs are validated against observations of SWF made with SuperDARN HF radars. We find that changes in the refractive index due to the F-region's plasma density enhancement is the primary cause of Doppler Flash.

How to cite: Chakraborty, S., Qian, L., Ruohoniemi, J. M., Baker, J., and McInerney, J.: The effects of solar flare-driven ionospheric electron density change on Doppler Flash, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1393, https://doi.org/10.5194/egusphere-egu21-1393, 2021.

EGU21-8545 | vPICO presentations | ST4.2

PreMevE: A Machine-Learning Based Predictive Model for MeV Electrons inside Earth’s Outer Radiation Belt

Yue Chen, Rafael Pires de Lima, Saurabh Sinha, and Youzuo Lin

The presence of megaelectron-volt (MeV) electrons in the Earth’s outer radiation belt poses a hazardous radiation environment for spaceborne electronics through the total ionization dose effect and deep dielectric charge/discharge phenomenon. Thus, developing a reliable forecasting model for MeV electron events has long been a critical but challenging task for space community. Here we update our recent progresses on the PREdictive model for MEV Electrons (PreMevE). This model exploits the power of machine learning algorithms, takes advantage of the coherence caused by local wave‐electron resonance, and uses electron observations from NOAA POES satellites in low‐Earth orbits as inputs—along with the upstream solar wind speeds and densities and GEO measurements—to provide high‐fidelity 1- and 2-day predictions of 1 MeV, 2 MeV and > 2 MeV electron flux distributions across the whole outer radiation belt. Using near-equatorial long-term electron data from the NASA Van Allen Probes mission, we trained, validated and demonstrated that the PreMevE model has L-shell averaged performance efficiencies of ~0.6 for out-of-sample 1-day forecasts and ~0.5 for 2-day forecasts. This study adds new science significance to an existing LEO and GEO space infrastructure, provides reliable and powerful tools to the whole space community, and also suggests for the development of more future tailored space weather models driven by similar methodologies.

How to cite: Chen, Y., Pires de Lima, R., Sinha, S., and Lin, Y.: PreMevE: A Machine-Learning Based Predictive Model for MeV Electrons inside Earth’s Outer Radiation Belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8545, https://doi.org/10.5194/egusphere-egu21-8545, 2021.

EGU21-15372 | vPICO presentations | ST4.2

Machine learning model of the plasmasphere to forecast satellite charging caused by solar storms.

Stefano Bianco, Irina Zhelavskaya, and Yuri Shprits

Solar storms are hazardous events consisting of a high emission of particles and radiation from the sun that can have adverse effect both in space and on Earth. In particular, the satellites can be damaged by energetic particles through surface and deep dielectric charging. The Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER) is an EU Horizon 2020 project, which aims to provide a forecast of satellite charging through a pipeline of algorithms connecting the solar activity with the satellite charging. The plasmasphere modeling is an essential component of this pipeline, as plasma density is a crucial parameter for evaluating surface charging. Moreover, plasma density in the plasmasphere has very significant scientific applications, as it controls the growth of waves and how waves interact with particles. Successful plasmasphere machine learning models have been already developed, using as input several geomagnetic indices. However, in the context of the PAGER project one is constrained to use solar wind features and Kp index, whose forecasts are provided by other components of the pipeline. Here, we develop a machine learning model of the plasma density using solar wind features and the Kp geomagnetic index. We validate and test the model by measuring its performance in particular during geomagnetic storms on independent datasets withheld from the training set and by comparing the model predictions with global images of He+ distribution in the Earth’s plasmasphere from the IMAGE Extreme UltraViolet (EUV) instrument. Finally, we present the results of both local and global plasma density reconstruction. 

How to cite: Bianco, S., Zhelavskaya, I., and Shprits, Y.: Machine learning model of the plasmasphere to forecast satellite charging caused by solar storms., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15372, https://doi.org/10.5194/egusphere-egu21-15372, 2021.

EGU21-2469 | vPICO presentations | ST4.2

Substorm related patterns of electron density and conductance changes in the auroral zone.

Nikita Stepanov, Sergeev Victor, Shukhtina Maria, Ogava Yasunobu, and Chu Xiangning

Enhanced precipitation of magnetospheric energetic particles during substorms increases ionospheric electron density and conductance. Such enhancements, which have timescales of a few hours, are not reproduced by the current ionospheric models. We use linear prediction filter technique to reconstruct the substorm-related response of electron densities at different altitudes and ionospheric conductances from long-term observations made by the European Incoherent SCATer (EISCAT) radar located at Tromso. To characterise the intensity of substorm injection at a 5min time step we use the midlatitude positive bay (MPB) index which basically responds to the substorm current wedge variations. We build response functions (LPF filters) between T0-1h and T0+4hrs (T0 is a substorm onset time) in different MLT sectors to estimate the magnitude and delays of the ionospheric density response at different altitudes. The systematic and largest relative substorm related changes are mostly observed in the lowest part of E and in D regions. The duration of the response is about 3 hours. It starts and reaches maximum magnitude near midnight, from which it mainly propagates toward east, where it decays when passing into the noon-evening sector. Such MLT structure corresponds to the drift motion of the injected high energy electron cloud in the magnetosphere. Model performance is better at the midnight-morning sectors (CC~0.6-0.65), where the response is larger, and it is getting worse at the noon-evening sector (CC~0.3-0.5). We also discuss the changes of effective electron energy spectra with the substorm time and MLT and compare the behaviors of global ionization, auroral absorption and conductance patterns as it propagates azimuthally from midnight along the auroral zone following after T0 time. Research was supported by RFBR grants №19-35-90054 and №19-05-00072 and MON grant №2020-220-08-6949.

How to cite: Stepanov, N., Victor, S., Maria, S., Yasunobu, O., and Xiangning, C.: Substorm related patterns of electron density and conductance changes in the auroral zone., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2469, https://doi.org/10.5194/egusphere-egu21-2469, 2021.

EGU21-14395 | vPICO presentations | ST4.2

The quantification and possible sources of spatially structured and large amplitude geomagnetic depressions during strong geomagnetic storms measured by IMAGE

Andrew Dimmock, Lisa Rosenqvist, Ari Viljanen, Colin Forsyth, Mervyn Freeman, Jonathan Rae, and Emiliya Yordanova

Geomagnetically Induced Currents (GICs) are a space weather hazard that can negatively impact large ground-based infrastructures such as power lines, pipelines, and railways. They are driven by the dynamic spatiotemporal behaviour of currents flowing in geospace, which drive rapid geomagnetic disturbances on the ground. In some cases, geomagnetic disturbances are highly localised and spatially structured due to the dynamical behaviour of geospace currents and magnetosphere-ionosphere (M-I) coupling dynamics, which are complex and often unclear.

In this work, we investigate and quantify the spatial structure of large geomagnetic depressions exceeding several hundred nT according to the 10 strongest events measured over Fennoscandia by IMAGE. Using ground magnetometer measurements we connect these spatially structured geomagnetic disturbances to possible M-I coupling processes and identify their likely magnetospheric origin. In addition, the ability for these disturbances to drive large GICs is assessed by calculating their respective geoelectric fields in Sweden using the SMAP ground conductivity model. To compliment the observations, we also utilise high resolution runs (>7 million cells) of the Space Weather Modeling Framework (SWMF) to determine to what extent global MHD models can capture this behaviour.

How to cite: Dimmock, A., Rosenqvist, L., Viljanen, A., Forsyth, C., Freeman, M., Rae, J., and Yordanova, E.: The quantification and possible sources of spatially structured and large amplitude geomagnetic depressions during strong geomagnetic storms measured by IMAGE, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14395, https://doi.org/10.5194/egusphere-egu21-14395, 2021.

EGU21-2483 | vPICO presentations | ST4.2

Indices of geomagnetic activity derived from space-born magnetic data from the Swarm mission

Constantinos Papadimitriou, Georgios Balasis, Adamantia Zoe Boutsi, Ioannis A. Daglis, Omiros Giannakis, Paola de Michelis, Giuseppe Consolini, Jesper W. Gjerloev, and Lorenzo Trenchi

Ground based indices, such as the Dst and AE, have been used for decades to describe the interplay of the terrestrial magnetosphere with the solar wind and provide quantifiable indications of the state of geomagnetic activity in general. These indices have been traditionally derived from ground based observations from magnetometer stations all around the Earth. In the last 7 years though, the highly successful satellite mission Swarm has provided the scientific community with an abundance of high quality magnetic measurements at Low Earth Orbit, which can be used to produce the space-based counterparts of these indices, such the Swarm-Dst and Swarm-AE Indices. In this work, we present the first results from this endeavour, with comparisons against traditionally used parameters, and postulate on the possible usefulness of these Swarm based products for space weather monitoring and forecasting.

How to cite: Papadimitriou, C., Balasis, G., Boutsi, A. Z., Daglis, I. A., Giannakis, O., de Michelis, P., Consolini, G., Gjerloev, J. W., and Trenchi, L.: Indices of geomagnetic activity derived from space-born magnetic data from the Swarm mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2483, https://doi.org/10.5194/egusphere-egu21-2483, 2021.

EGU21-2846 | vPICO presentations | ST4.2

The open-ended, high cadence, Kp-like geomagnetic Hp30 and Hp60 indices

Guram Kervalishvili, Jürgen Matzka, Claudia Stolle, and Jan Rauberg
The new planetary open-ended Hpo index family (consisting of the half-hourly Hp30 and hourly Hp60) has been developed within the Space Weather Atmosphere Models and Indices (SWAMI) project (see http://swami-h2020.eu/) of the H2020 European Union research activity. These new indices resemble the Kp index by having a similar derivation scheme and a nearly identical frequency distribution of index values for events with values < 9. However, they have provided a better temporal resolution than the 3-hourly Kp index. Additionally, the events with values > 9- are further subdivided using an open-ended scale (9o, 9+, 10-, 10o, 10+, 11-, ...) to better represent different levels of strong geomagnetic activity. In this study, the advantages and integrity of Hp30 and Hp60 indices are analysed and discussed. The comparison of these indices with the 3-hourly Kp index in terms of frequency distribution and correlation and with other geophysical parameters are also presented.
Near real-time indices and archive indices back to 1995 are available from GFZ under the CC BY 4.0 license including linear versions of the Hp30 and Hp60 indices, the ap30 and ap60 indices (see https://www.gfz-potsdam.de/en/section/geomagnetism/data-products-services/hpo-index/). Near real-time plots of the Hp30, Hp60 and Kp indices for the current day and the previous six days are also provided.

How to cite: Kervalishvili, G., Matzka, J., Stolle, C., and Rauberg, J.: The open-ended, high cadence, Kp-like geomagnetic Hp30 and Hp60 indices, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2846, https://doi.org/10.5194/egusphere-egu21-2846, 2021.

EGU21-8488 | vPICO presentations | ST4.2 | Highlight

Observing Earth space environment with LEO multi-mission data

Claudia Stolle, Chao Xiong, and Ingo Michaelis

In situ data from satellites in Low Earth Orbit (LEO) has become indispensable to monitor and explore near-Earth space. In contrast to ground-based observations they provide global coverage, and they sense parameters at altitudes that often remain hidden when applying remote sensing techniques either ground- or space-based. 

In recent years, data derived from instruments onboard LEO missions, which were not primarily dedicated for space science application, have proven added value in deriving the spatial and temporal variations of the magnetosphere, ionosphere and thermosphere.

This presentation will discuss the benefit of calibrated data from platform magnetometers that are originally designed for spacecraft attitude control. We will put focus on the dual-satellite GRACE-FO mission, that is suitable to derive scale-lengths, e.g., for auroral field-aligned currents, and in constellation with data from other platform magnetometers to resolve the local time dependence of the magnetospheric ring current signal. We further introduce new data sets of electron density and GPS-derived topside electron content from the GRACE and GRACE-FO missions.

How to cite: Stolle, C., Xiong, C., and Michaelis, I.: Observing Earth space environment with LEO multi-mission data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8488, https://doi.org/10.5194/egusphere-egu21-8488, 2021.

EGU21-5580 | vPICO presentations | ST4.2

Thermospheric densities for the Swarm satellite mission

Jose van den IJssel, Christian Siemes, and Pieter Visser

The European Space Agency (ESA) Swarm mission was launched in November 2013 and consists of three identical satellites flying in near-polar orbits. One satellite is flying at about 515 km, while the other two satellites are flying side-by-side at lower altitudes, starting at 480 km altitude and slowly descending due to atmospheric drag to their current 445 km altitude. This coverage of altitudes, together with the satellite payload that includes an accelerometer and GPS receiver, makes the mission particularly suited for atmospheric density retrieval. Unfortunately, the Swarm accelerometers suffer from several anomalies which limits their usefulness for density retrieval. Currently, only accelerometer observations from one of the lower flying satellites (Swarm-C) can be used to generate high-resolution thermospheric densities. However, all satellites deliver high-quality GPS data and an alternative processing strategy has been developed to derive thermospheric densities from these observations as well.

This presentation describes the processing strategy that is used to derive thermospheric densities from the Swarm accelerometer and GPS observations and presents the latest results. The relatively smooth GPS-derived densities have a temporal resolution of about 20 minutes, and show variations due to solar and geomagnetic activity, as well as seasonal, latitudinal and diurnal variation. For analysis of higher-resolution phenomena, only the accelerometer-derived densities can be used. All Swarm thermospheric densities are available for users at the dedicated ESA Swarm website (ftp://swarm-diss.eo.esa.int), as well as at our thermospheric density database (http://thermosphere.tudelft.nl). This database also includes thermospheric densities for the CHAMP, GRACE and GOCE satellites. For future work, it is planned to further improve the Swarm densities, especially for low solar activity conditions, by including a more sophisticated radiation pressure modelling of the Swarm satellites. In addition, it is planned to extend our database with thermospheric densities for the GRACE-FO mission.

How to cite: van den IJssel, J., Siemes, C., and Visser, P.: Thermospheric densities for the Swarm satellite mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5580, https://doi.org/10.5194/egusphere-egu21-5580, 2021.

EGU21-8912 | vPICO presentations | ST4.2

NASA Space Weather Science Application Strategy and Activities

James Spann

The NASA Heliophysics Division Space Weather Science Application (SWxSA) program has as its strategic mission to establish a preeminent space weather capability that supports human and robotic space exploration and meets national, international, and societal needs. This is done by advancing measurement and analysis techniques and expanding knowledge and understanding that improves space weather forecasts and nowcasts. Ultimately, the SWxSA program enables space weather forecasting capability that the Agency and Nation and international community require, in partnership with NASA’s Artemis Program and other Federal agencies, and international partners. This includes the development and launch of missions/instruments that advance our knowledge of space weather and improve its prediction, and the transitioning of technology, tools, models, data, and knowledge from research to operational environments. This presentation will provide an update on NASA’s SWxSA space weather strategy and activities.

How to cite: Spann, J.: NASA Space Weather Science Application Strategy and Activities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8912, https://doi.org/10.5194/egusphere-egu21-8912, 2021.

EGU21-13466 | vPICO presentations | ST4.2

Improving nowcasting and forecasting of the Sun-to-Belts space weather chain through the H2020 SafeSpace project

Ioannis A. Daglis, Sebastien Bourdarie, Juan Cueto Rodriguez, Fabien Darrouzet, Benoit Lavraud, Stefaan Poedts, Ingmar Sandberg, and Ondrej Santolik and the SafeSpace Team

The H2020 SafeSpace project aims at advancing space weather nowcasting and forecasting capabilities and, ultimately, at contributing to the safety of space assets. This will be achieved through the synergy of five well-established space weather models covering the complete Sun – interplanetary space – Earth’s magnetosphere – radiation belts chain. The combined use of these models will enable the delivery of a sophisticated model of the Van Allen electron belt and of a prototype space weather service of tailored particle radiation indicators. Moreover, it will enable forecast capabilities with a target lead time of 2 to 4 days, which is a tremendous advance from current forecasts that are limited to lead times of a few hours. SafeSpace will improve radiation belt modelling through the incorporation into the Salammbô model of magnetospheric processes and parameters of critical importance to radiation belt dynamics. Furthermore, solar and interplanetary conditions will be used as initial conditions to drive the advanced radiation belt model and to provide the link to the solar origin and the interplanetary drivers of space weather. This approach will culminate in a prototype early warning system for detrimental space weather events, which will include indicators of particle radiation of use to space industry and spacecraft operators. Indicator values will be generated by the advanced radiation belt model and the performance of the prototype service will be evaluated in collaboration with space industry stakeholders. The work leading to this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace (Radiation Belt Environmental Indicators for the Safety of Space Assets) project.

How to cite: Daglis, I. A., Bourdarie, S., Cueto Rodriguez, J., Darrouzet, F., Lavraud, B., Poedts, S., Sandberg, I., and Santolik, O. and the SafeSpace Team: Improving nowcasting and forecasting of the Sun-to-Belts space weather chain through the H2020 SafeSpace project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13466, https://doi.org/10.5194/egusphere-egu21-13466, 2021.

EGU21-10796 | vPICO presentations | ST4.2 | Highlight

Modeling the Sun – Earth propagation of solar disturbances for the H2020 SafeSpace project

Benoit Lavraud, Rui Pinto, Rungployphan Kieokaew, Evangelia Samara, Stefaan Poedts, Vincent Génot, Alexis Rouillard, Antoine Brunet, Sebastien Bourdarie, Benjamin Grison, Jan Soucek, and Yannis Daglis

We present the solar wind forecast pipeline that is being implemented as part of the H2020 SafeSpace project. The Goal of this project is to use several tools in a modular fashion to address the physics of Sun – interplanetary space – Earth’s magnetosphere. This presentation focuses on the part of the pipeline that is dedicated to the forecasting – from solar measurements – of the solar wind properties at the Lagrangian L1 point. The modeling pipeline puts together different mature research models: determination of the background coronal magnetic field, computation of solar wind acceleration profiles (1 to 90 solar radii), propagation across the heliosphere (for regular solar wind, CIRs and CMEs), and comparison to spacecraft measurements. Different magnetogram sources (WSO, SOLIS, GONG, ADAPT) can be combined, as well as coronal field reconstruction methods (PFSS, NLFFF), wind (MULTI-VP) and heliospheric propagation models (CDPP 1D MHD, EUHFORIA). We aim at providing a web-based service that continuously supplies a full set of bulk physical parameters of the solar wind at 1 AU several days in advance, at a time cadence compatible with space weather applications. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437.

How to cite: Lavraud, B., Pinto, R., Kieokaew, R., Samara, E., Poedts, S., Génot, V., Rouillard, A., Brunet, A., Bourdarie, S., Grison, B., Soucek, J., and Daglis, Y.: Modeling the Sun – Earth propagation of solar disturbances for the H2020 SafeSpace project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10796, https://doi.org/10.5194/egusphere-egu21-10796, 2021.

EGU21-6455 | vPICO presentations | ST4.2

LOFAR4SW – Space Weather Science and Operations with LOFAR

Hanna Rothkaehl, Barbara Matyjasiak, Carla Baldovin, Mario Bisi, David Barnes, Eoin Carley, Tobia Carozzi, Richard A. Fallows, Peter T. Gallagher, Maaijke Mevius, Stuart C. Robertson, Mark Ruiter, Joris Verbiest, Renne Vermeulen, and Nicole Vilmer

Space Weather (SW) research is a very important topic from the scientific, operational and civic society point of view. Knowledge of interactions in the Sun-Earth system, the physics behind observed SW phenomena, and its direct impact on modern technologies were and will be key areas of interest.  The LOFAR for Space Weather (LOFAR4SW) project aim is to prepare a novel tool which can bring new capabilities into this domain. The project is realised in the frame of a Horizon 2020 INFRADEV call.  The base for the project is the Low Frequency Array (LOFAR) - the worlds largest low frequency radio telescope, with a dense core near Exloo in The Netherlands and many stations distributed both in the Netherlands and Europe wide with baselines up to 2000 km.  The final design of LOFAR4SW will provide a full conceptual and technical description of the LOFAR upgrade, to enable simultaneous operation as a radio telescope for astronomical research as well as an infrastructure working for Space Weather studies.  In this work we present the current status of the project, including examples of the capabilities of LOFAR4SW and the project timeline as we plan for the Critical Design Review later in 2021.

How to cite: Rothkaehl, H., Matyjasiak, B., Baldovin, C., Bisi, M., Barnes, D., Carley, E., Carozzi, T., Fallows, R. A., Gallagher, P. T., Mevius, M., Robertson, S. C., Ruiter, M., Verbiest, J., Vermeulen, R., and Vilmer, N.: LOFAR4SW – Space Weather Science and Operations with LOFAR, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6455, https://doi.org/10.5194/egusphere-egu21-6455, 2021.

EGU21-9775 | vPICO presentations | ST4.2

Acceleration of Solar Energetic Particles in CME-Driven Coronal Shocks up to 30 Rs

Kamen Kozarev, Mohamed Nedal, Rositsa Miteva, Pietro Zucca, and Momchil Dechev

The lower and middle solar corona up to about 30 solar radii is thought to be an important region for early acceleration and transport of solar energetic particles (SEPs) by coronal mass ejection-driven shock waves. There, these waves propagate into a highly variable dynamic medium with steep gradients and rapidly expanding coronal magnetic fields, which modulates the particle acceleration near the shock/wave surfaces, and the way SEPs spread into the heliosphere. We present a study modeling the acceleration of SEPs in over 50 separate global coronal shock events between 1 and 30 solar radii. As part of the SPREAdFAST framework project, we analyzed the interaction of off-limb coronal bright fronts (CBF) observed with the SDO/AIA EUV telescope with realistic model coronal plasma based on results from synoptic magnetohydrodynamic (MHD) and differential emission measure (DEM) models. We used realistic quiet-time proton spectra observed near Earth to form seed suprathermal populations accelerated in our diffusive shock acceleration model (Kozarev & Schwadron, 2016). We summarize our findings and present implications for nowcasting SEP acceleration and heliospheric connectivity.

How to cite: Kozarev, K., Nedal, M., Miteva, R., Zucca, P., and Dechev, M.: Acceleration of Solar Energetic Particles in CME-Driven Coronal Shocks up to 30 Rs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9775, https://doi.org/10.5194/egusphere-egu21-9775, 2021.

EGU21-9809 | vPICO presentations | ST4.2

Characterizing the Dynamics of CME-Driven Coronal Bright Fronts Using The SPREAdFAST Framework 

Mohamed Nedal, Kamen Kozarev, and Rositsa Miteva

In this work, we present a full characterization of over 50 historical Coronal Mass Ejection (CME)-driven compressive waves in the low solar corona, related to solar energetic particle events near Earth, using the Solar Particle Radiation Environment Analysis and Forecasting - Acceleration and Scattering Transport (SPREAdFAST) framework. SPREAdFAST is a physics-based, operational heliospheric solar energetic particle (SEP) forecasting system, which incorporates a chain of data-driven analytic and numerical models for estimating: a) coronal magnetic field from Potential Field Source Surface (PFSS) and Magnetohydrodynamics (MHD); b) dynamics of large-scale coronal (CME-driven) shock waves; c) energetic particle acceleration; d) scatter-based, time-dependent SEP propagation in the heliosphere to specific time-dependent positions. SPREAdFAST allows for producing predictions of SEP fluxes at multiple locations in the inner heliosphere, by modeling their acceleration at CMEs near the Sun, and their subsequent interplanetary transport. We used sequences of base-difference images obtained from the AIA instrument on board the SDO satellite, with 24-second cadence. We calculated time-dependent speeds in both the radial and lateral (parallel to the solar limb) directions, mean intensities and thicknesses of the fronts, and major and minor axes. This is essential for characterizing the SEP spectra near the Sun. The kinematics measurements were used to generate time-dependent 3D geometric models of the wave fronts and time-dependent plasma diagnostics using MHD and DEM model results.

 

 

How to cite: Nedal, M., Kozarev, K., and Miteva, R.: Characterizing the Dynamics of CME-Driven Coronal Bright Fronts Using The SPREAdFAST Framework , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9809, https://doi.org/10.5194/egusphere-egu21-9809, 2021.

EGU21-15520 | vPICO presentations | ST4.2

Failure to forecast: A case study in nowcasting and forecasting the eruption of a coronal mass ejection and its geomagnetic impacts on Dec 7-10, 2020. 

Peter Gallagher, Sophie Murray, John Malone-Leigh, Joan Campanyà, Alberto Cañizares, Eoin Carley, and Seán Blake

Forecasting solar flares based on while-light images and photospheric magnetograms of sunspots is notoriously challenging, while accurate forecasting of coronal mass ejections (CME) is still in its infancy. That said, the chances of a CME being launched is more likely following a flare. CMEs launched from the western hemisphere and “halo” CMEs are the most likely to be geomagnetically impactful, but forecasting their arrival and impact at Earth depends on how well their velocity is known near the Sun, the solar wind conditions between the Sun and the Earth, the accuracy of theoretical models and on the orientation of the CME magnetic field.  In this presentation, we describe a well observed active region, flare, CME, radio burst and sudden geomagnetic impulse that was observed on December 7-10, 2020 by a slew of instruments (SDO, ACE, DSCOVR, PSP, US and European magnetometers). This was a solar eruption that was not expected, but the CME and resulting geomagnetic impact should have been straight-forward to model and forecast. What can we learn from our failure to forecast this simple event and its impacts at Earth? 

How to cite: Gallagher, P., Murray, S., Malone-Leigh, J., Campanyà, J., Cañizares, A., Carley, E., and Blake, S.: Failure to forecast: A case study in nowcasting and forecasting the eruption of a coronal mass ejection and its geomagnetic impacts on Dec 7-10, 2020. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15520, https://doi.org/10.5194/egusphere-egu21-15520, 2021.

EGU21-4598 | vPICO presentations | ST4.2

Validating GIC modelling in the Spanish power grid by differential magnetometry

J. Miquel Torta, Santiago Marsal, Juan J. Curto, Oscar Cid, Miguel Ibañez, Victoria Canillas, and Alex Marcuello

A series of experiences and recommendations are presented concerning the measurement of geomagnetically induced currents (GIC) in the Spanish power transmission grid by use of the method of differential magnetometry under power lines, by which differential observations are made (one below the line and another at a few hundred meters away) using vector magnetometers to capture the magnetic effect of the GIC flowing through them. This indirect technique, aimed at obtaining observations to validate GIC computational models, is an alternative to the more common way of measuring the current flow in the transformer neutrals, as it does not rely on the involved power grid operators. In contrast, the selection of a suitable site devoid of human interferences, the need of power for the magnetometer/acquisition system, and the election of the appropriate instrumentation are difficulties that often require costly solutions. Our methodology includes the settlement of appropriate magnetometers with the correct levelling and orientation placed inside buried water-proof containers. The magnetometers are fed by solar panel-battery systems, and we have also developed low-consumption data-transmission models using Raspberry-Pi with GPRS connection technology. According to our experience, only induced currents above about 1 A give magnetic signatures that exceed the noise threshold. As we started measuring during the solar minimum and Spain is a mid-latitude country, the latter fact limited the significance of available recorded data, but we can already report and analyse the results for a number of minor geomagnetic storms.

How to cite: Torta, J. M., Marsal, S., Curto, J. J., Cid, O., Ibañez, M., Canillas, V., and Marcuello, A.: Validating GIC modelling in the Spanish power grid by differential magnetometry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4598, https://doi.org/10.5194/egusphere-egu21-4598, 2021.

EGU21-11822 | vPICO presentations | ST4.2

Geoelectric field as a GIC proxy during the intense geomagnetic storms and Polish transmission lines failures occurrence

Agnieszka Gil, Monika Berendt-Marchel, Renata Modzelewska, Szczepan Moskwa, Agnieszka Siluszyk, Marek Siluszyk, Lukasz Tomasik, Anna Wawrzaszek, and Anna Wawrzynczak

We study intense geomagnetic storms (Dst < 100nT) during the first half of the solar cycle 24. This type of storm appeared only a few times, mostly associated with southwardly directed heliospheric magnetic field  Bz . Using various methodology as self-organizing maps, statistical and superposed epoch analysis, we show that during and right after intense geomagnetic storms, growth in the number of transmission lines failures, which might be of solar origin, appeared. We also examine the temporal changes in the number of failures during 2010-2014 and found the growing linear tendency of electrical grid failures occurrence possibly connected with solar activity. We confront these results with the geoelectric field calculated for the Poland region using a 1-D layered conductivity Earth model.

How to cite: Gil, A., Berendt-Marchel, M., Modzelewska, R., Moskwa, S., Siluszyk, A., Siluszyk, M., Tomasik, L., Wawrzaszek, A., and Wawrzynczak, A.: Geoelectric field as a GIC proxy during the intense geomagnetic storms and Polish transmission lines failures occurrence, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11822, https://doi.org/10.5194/egusphere-egu21-11822, 2021.

EGU21-1863 | vPICO presentations | ST4.2

Towards the estimation of Space Weather-related corrosion on pipelines

Larisa Trichtchenko

Geomagnetically induced currents (GIC), increased during space weather events, are able to interfere with pipeline corrosion protections systems and potentially can increase corrosion of the pipeline steel.

Methods, widely used for the evaluation of annual corrosion rates, are based on exposure of steel to constant currents and voltages (DC), or alternating currents and voltages of a constant frequency (50 Hz or 60 Hz), while GIC are characterised by a continuous frequency spectrum, with the range of frequencies from 10-5 Hz to 1 Hz.

This paper introduces the methods for use in the estimation of corrosion rates on pipeline steel produced by GIC (commonly referred to as “telluric currents” in the pipeline industry) and provides results calculated for specific time periods with use of available recordings made on pipelines at the times of geomagnetic storms. As well, annual cumulative corrosion rates are estimated based on the modelling of pipeline currents and voltages.

In addition to the detailed presentation of the methods utilised, a comparison of corrosion rates produced by telluric variations on non-protected and protected pipelines located in mid- and high-latitudes is presented.

How to cite: Trichtchenko, L.: Towards the estimation of Space Weather-related corrosion on pipelines, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1863, https://doi.org/10.5194/egusphere-egu21-1863, 2021.

EGU21-282 | vPICO presentations | ST4.2

Several Populations of Sunspot Group Numbers – Resolving a Conundrum

Leif Svalgaard

The long-standing disparity between the sunspot number record and the Hoyt and Schatten (1998, H&S) Group Sunspot Number series was initially resolved by the Clette et al. (2014) revision of the sunspot number and the group number series. The revisions resulted in a flurry of dissenting group number series while the revised sunspot number series was generally accepted. Thus, the disparity persisted and confusion reigned, with the choice of solar activity dataset continuing to be a free parameter. A number of workshops and follow-up collaborative efforts by the community have not yet brought clarity. We review here several lines of evidence that validate the original revisions put forward by Clette et al. (2014) and suggest that the perceived conundrum no longer need to delay acceptance and general use of the revised series. We argue that the solar observations constitute several distinct populations with different properties which explain the various discontinuities in the series. This is supported by several proxies: diurnal variation of the geomagnetic field, geomagnetic signature of the strength of the heliomagnetic field, and variation of radionuclides. The Waldmeier effect shows that the sunspot number scale has not changed over the last 270 years and a mistaken scale factor between observers Wolf and Wolfer explains the disparity beginning in 1882 between the sunspot number and the H&S reconstruction of the group number. Observations with replica of 18th century telescopes (with similar optical flaws) validate the early sunspot number scale; while a reconstruction of the group number with monthly resolution (with many more degrees of freedom) validate the size of Solar Cycle 11 given by the revised series that the dissenting series fail to meet. Based on the evidence at hand, we urge the working groups tasked with producing community-vetted and agreed upon solar activity series to complete their work expeditiously.

How to cite: Svalgaard, L.: Several Populations of Sunspot Group Numbers – Resolving a Conundrum, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-282, https://doi.org/10.5194/egusphere-egu21-282, 2021.

EGU21-9953 | vPICO presentations | ST4.2

Multi-energy analysis of SPREAdFAST proton events

Rositsa Miteva, Kamen Kozarev, and Mohamed Nedal

We present the procedure of event selection, data analysis and interpretation of solar energetic protons during the last solar cycle 24 for the needs of the SPREAdFAST project. Data from SOHO/ERNE and ACE/EPAM instruments have been analysed for nearly 100 proton events in the available energy bands. The energy dependence of the proton peak intensities and background spectra is completed. The energy range from a few to 130 MeV has been covered. Protons from the SPREAdFAST historical event list have been selected for a detailed comparative analysis. The validation between the observed and simulated proton events is presented and discussed.

How to cite: Miteva, R., Kozarev, K., and Nedal, M.: Multi-energy analysis of SPREAdFAST proton events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9953, https://doi.org/10.5194/egusphere-egu21-9953, 2021.

EGU21-310 | vPICO presentations | ST4.2

A method for recognizing the muon flux intensity modulations using the normalized variation functions for the URAGAN hodoscope matrix data

Vladislav Chinkin, Viktor Getmanov, Roman Sidorov, Alexei Gvishiani, Mikhail Dobrovolsky, Anatoly Soloviev, Anna Dmitrieva, Anna Kovylyaeva, Natalia Osetrova, and Igor Yashin

Muon flux intensity modulation (MFIM) recognition is a relevant solar-terrestrial physics problem. The considered MFIM, recorded on the Earth's surface, are caused by extreme heliospheric events – the geoeffective solar coronal mass ejections.

The URAGAN muon hodoscope (MH), developed by NRNU MEPhI, a computerized device that measures the intensities of muon fluxes, is used. In the MH, the number of muons falling per unit time on the MH aperture is calculated for the selected system of zenith and azimuthal angles. MH matrix data time series are formed. In the MH data, there are angular modulations due to the action of the hardware function HF, temporal modulations due to atmospheric disturbances and noise: the values of these modulations significantly exceed the values of MFIM of cosmic origin. This circumstance prevents effective MFIM recognition.

A method for MFIM recognition is proposed, based on the mathematical apparatus of the introduced normalized variation functions for MH matrix data, and focused on overcoming the noted circumstance.

A two-dimensional normalized HF is defined for MH. A quite realistic hypothesis is accepted about the initialiy uniform muon flux intensity distributions on a small reference time interval, where there are no extreme heliospheric events and the corresponding reference MH data do not contain significant MFIMs. The estimation of the two-dimensional normalized HF is carried out on the basis of a multiparameter model and its optimization fit to the reference MH data. In order to reduce noise errors, the estimate of the two-dimensional normalized HF is subjected to two-dimensional filtering and subsequent threshold filtering.

Two-dimensional functions of variations of matrix MH datas with respect to two-dimensional normalized AF are calculated. The normalized variation functions are calculated by dividing the two-dimensional functions of variations of matrix MH data by the two-dimensional normalized HF. MFIM recognition method was tested on model and experimental MH data.

A time series of model matrix MH data containing model MFIM was generated. Testing led to a conclusion that it is possible to recognize MFIM with decreases of about 2-3%. A time series of experimental matrix MH data was generated, in which the model MFIM-containing areas were made. Testing led to a conclusion that it is possible to recognize MFIM with the magnitudes of the decreases almost commensurate with the decreases for the case of model MH data.

The proposed MFIM recognition method based on the normalized variation functions for matrix MH data has a favorable perspective for its application in solving problems of geomagnetic storm early diagnostics.

This work was funded by the Russian Science Foundation (project No.17-17-01215).

How to cite: Chinkin, V., Getmanov, V., Sidorov, R., Gvishiani, A., Dobrovolsky, M., Soloviev, A., Dmitrieva, A., Kovylyaeva, A., Osetrova, N., and Yashin, I.: A method for recognizing the muon flux intensity modulations using the normalized variation functions for the URAGAN hodoscope matrix data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-310, https://doi.org/10.5194/egusphere-egu21-310, 2021.

ST4.3 – Space weather prediction of solar wind transients in the heliosphere

EGU21-192 | vPICO presentations | ST4.3

Improving CME modelling with data assimilation of Heliospheric Imager observations into the HUXt solar wind numerical model.

Luke Barnard, Mat Owens, Chris Scott, and Matt Lang

Coronal Mass Ejections that impact Earth drive the most severe space weather. To better enable effective space weather mitigation plans, there is much interest in improving the quality of CME arrival time predictions, particularly by quantifying and reducing the prediction uncertainty. A limited set of observatories, challenges in interpreting observation data, and limiting assumptions in CME parameterisations all play important roles in the uncertainty of the predicted CME evolution.

Data assimilation techniques provide a path for improving the predictive skill, by integrating observations into a modelling framework in a way that returns model states that better reflect the true state of a system. Furthermore, such techniques can self-consistently account for uncertainty in the observations, and uncertainty in the models structure and parameterisations.

We present some early results from our work to build a particle filter data assimilation scheme around the HUXt solar wind model. Assimilating the time-elongation profiles of CME flanks observed by the Heliospheric Imagers on NASAs STEREO mission, we demonstrate that such methods have good potential to improve modelled CME arrival time predictions. Using a simulation study, we present an estimate of the potential CME arrival time prediction improvements gained by using this particle-filter approach with an L5 Heliospheric Imager.

How to cite: Barnard, L., Owens, M., Scott, C., and Lang, M.: Improving CME modelling with data assimilation of Heliospheric Imager observations into the HUXt solar wind numerical model., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-192, https://doi.org/10.5194/egusphere-egu21-192, 2021.

EGU21-2526 | vPICO presentations | ST4.3

Influence of the CME orientation on the ICME propagation

Karmen Martinić, Mateja Dumbović, and Bojan Vršnak

Beyond certain distance the ICME propagation becomes mostly governed by the interaction of the ICME and the ambient solar wind. Configuration of the interplanetary magnetic field and features of the related ambient solar wind in the ecliptic and meridional plane are different. Therefore, one can expect that the inclination of the CME flux rope axis i.e. tilt, influences the propagation of the ICME itself. In order to study the relation between the tilt parameter and the ICME propagation we investigated isolated Earth-impacting CME-ICME evets in the time period from 2006. to 2014. We determined the CME tilt in the “near-Sun” environment from the 3D reconstruction of the CME, obtained by the Graduated Cylindrical Shell model using coronagraphic images provided by the STEREO and SOHO missions. We determined the tilt of the ICME in the “near-Earth” environment using in-situ data. We constrained our study to CME-ICME events that show no evidence of rotation while propagating, i.e. have a similar tilt in the “near-Sun” and “near-Earth” environment. We present preliminary results of our study and discuss their implications for space-weather forecasting using the drag-based(ensemble) [DB(E)M] model of heliospheric propagation.

How to cite: Martinić, K., Dumbović, M., and Vršnak, B.: Influence of the CME orientation on the ICME propagation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2526, https://doi.org/10.5194/egusphere-egu21-2526, 2021.

EGU21-3216 | vPICO presentations | ST4.3

 Statistical study of CMEs, lateral overexpansion and SEP events

Alexandros Adamis, Astrid Veronig, Tatiana Podladchikova, Karin Dissauer, Rositsa Miteva, Jingnan Guo, Veronika Haberle, Mateja Dumbovic, Manuela Temmer, Kamen Kozarev, Jasmina Magdalenic, and Christina Kay

We present a statistical study on the early evolution of coronal mass ejections (CMEs), to better understand the effect of CME (over)- expansion and how it relates to the production of Solar Energetic Particle (SEP) events. We study the kinematic CME characteristics in terms of their radial and lateral expansion, from their early evolution in the Sun’s atmosphere as observed in EUV imagers and coronagraphs. The data covers 72 CMEs that occurred in the time range of July 2010 to September 2012, where the twin STEREO spacecraft where in quasiquadrature to the Sun-Earth line. From the STEREO point-of-view, the CMEs under study were observed close to the limb. We calculated the radial and lateral height (width) versus time profiles and derived the corresponding peak and mean velocities, accelerations, and angular expansion rates, with particular emphasis on the role of potential lateral overexpansion in the early CME evolution. We find high correlations between the radial and lateral CME velocities and accelerations. CMEs that are associated tend to be located at the high-value end of the distributions of velocities, widths, and expansion rates compared to nonSEP associated events.

How to cite: Adamis, A., Veronig, A., Podladchikova, T., Dissauer, K., Miteva, R., Guo, J., Haberle, V., Dumbovic, M., Temmer, M., Kozarev, K., Magdalenic, J., and Kay, C.:  Statistical study of CMEs, lateral overexpansion and SEP events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3216, https://doi.org/10.5194/egusphere-egu21-3216, 2021.

EGU21-5830 | vPICO presentations | ST4.3

CME arrival time predictions with a deformable front

Jürgen Hinterreiter, Tanja Amerstorfer, Martin A. Reiss, Andreas J. Weiss, Christian Möstl, Manuela Temmer, Maike Bauer, Rachel L. Bailey, and Ute V. Amerstorfer

We present the first results of our newly developed CME arrival prediction model, which allows the CME front to deform and adapt to the changing solar wind conditions. Our model is based on ELEvoHI and makes use of the WSA/HUX (Wang-Sheeley-Arge/Heliospheric Upwind eXtrapolation) model combination, which computes large-scale ambient solar wind conditions in the interplanetary space. With an estimate of the solar wind speed and density, we are able to account for the drag exerted on different parts of the CME front. Initially, our model relies on heliospheric imager observations to confine an elliptical CME front and to obtain an initial speed and drag parameter for the CME. After a certain distance, each point of the CME front is propagating based on the conditions in the heliosphere. In this case study, we compare our results to previous arrival time predictions using ELEvoHI with a rigid CME front. We find that the actual arrival time at Earth and the arrival time predicted by the new model are in very good agreement.

How to cite: Hinterreiter, J., Amerstorfer, T., Reiss, M. A., Weiss, A. J., Möstl, C., Temmer, M., Bauer, M., Bailey, R. L., and Amerstorfer, U. V.: CME arrival time predictions with a deformable front, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5830, https://doi.org/10.5194/egusphere-egu21-5830, 2021.

EGU21-7661 | vPICO presentations | ST4.3 | Highlight

Predicting arrival time for CMEs: Machine learning and ensemble methods

Ajay Tiwari, Enrico Camporeale, Jannis Teunissen, Raffaello Foldes, Gianluca Napoletano, and Dario Del Moro

Coronal mass ejections (CMEs) are arguably one of the most violent explosions in our solar system. CMEs are also one of the most important drivers for space weather. CMEs can have direct adverse effects on several human activities. Reliable and fast prediction of the CMEs arrival time is crucial to minimize such damage from a CME. We present a new pipeline combining machine learning (ML) with a physical drag-based model of CME propagation to predict the arrival time of the CME. We evaluate both standard ML approaches and a combination of ML + probabilistic drag based model (PDBM, Napoletano et al. 2018). More than 200 previously observed geo-effective partial-/full-halo CMEs make up the database for this study (with information extracted from the Richardson & Cane 2010 catalogue, the CDAW data centre CME list, the LASCO coronagraphic images, and the HEK database - Hurlburt et al. 2010). The P-DBM provides us with a reduced computation time, which is promising for space weather forecasts. We analyzed and compared various machine learning algorithms to identify the best performing algorithm for this database of the CMEs. We also examine the relative importance of various features such as mass, CME propagation speed, and height above the solar limb of the observed CMEs in the prediction of the arrival time. The model is able to accurately predict the arrival times of the CMEs with a mean square error of about 9 hours.  We also explore the differences in prediction from ML models and emblem prediction method namely P-DBM model.

How to cite: Tiwari, A., Camporeale, E., Teunissen, J., Foldes, R., Napoletano, G., and Del Moro, D.: Predicting arrival time for CMEs: Machine learning and ensemble methods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7661, https://doi.org/10.5194/egusphere-egu21-7661, 2021.

EGU21-7753 | vPICO presentations | ST4.3

Drag-Based Ensemble Model (DBEM) to predict the heliospheric propagation of CMEs

Jasa Calogovic, Mateja Dumbović, Davor Sudar, Bojan Vršnak, Karmen Martinić, Manuela Temmer, and Astrid Veronig

The Drag-based Model (DBM) is an analytical model for heliospheric propagation of Coronal Mass Ejections (CMEs) that predicts the CME arrival time and speed at Earth or any other given target in the solar system. It is based on the equation of motion and depends on initial CME parameters, background solar wind speed, w and the drag parameter γ. A very short computational time of DBM (< 0.01s) allowed us to develop the Drag-Based Ensemble Model (DBEM) that considers the variability of model input parameters by making an ensemble of n different input parameters to calculate the distribution and significance of the DBM results. Using such an approach, we apply DBEM to determine the most likely CME arrival times and speeds, quantify the prediction uncertainties and calculate the confidence intervals. Recently, a new DBEMv3 version was developed including the various improvements and Graduated Cylindrical Shell (GCS) option for the CME geometry input as well as the CME propagation visualizations. Thus, we compare the DBEMv3 with previous DBEM versions (e.g. DBEMv2), evaluate it and determine the DBEMv3 performance and errors by using various CME-ICME lists. Compared to the previous versions, the DBEMv3 provides very similar results for all calculated output parameters with slight improvement in the performance. Based on the evaluation performed for 146 CME-ICME pairs, the DBEMv3 performance with mean error (ME) of -11.3 h, mean absolute error (MAE) of 17.3 h was obtained, similar to previous DBM and DBEM evaluations. Fully operational DBEMv3 web application was integrated as one of the ESA Space Situational Awareness portal services (https://swe.ssa.esa.int/current-space-weather) providing an important tool for space weather forecasters.

How to cite: Calogovic, J., Dumbović, M., Sudar, D., Vršnak, B., Martinić, K., Temmer, M., and Veronig, A.: Drag-Based Ensemble Model (DBEM) to predict the heliospheric propagation of CMEs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7753, https://doi.org/10.5194/egusphere-egu21-7753, 2021.

EGU21-8141 | vPICO presentations | ST4.3

Structure and connectivity of CME-driven shocks and sheaths through the inner heliosphere

Erika Palmerio, Christina Lee, Dusan Odstrcil, and Leila Mays

EGU21-8932 | vPICO presentations | ST4.3

Effect of the ambient solar wind speed on drag-based CME prediction accuracy

Tanja Amerstorfer, Jürgen Hinterreiter, Martin A. Reiss, Jackie A. Davies, Christian Möstl, Andreas J. Weiss, Maike Bauer, Ute V. Amerstorfer, Rachel L. Bailey, and Richard A. Harrison

In the last years, many kinds of CME models, based on a drag-based evolution through interplanetary space, have been developed and are now widely used by the community. The unbeatable advantage of those methods is that they are computationally cheap and are therefore suitable to be used as ensemble models. Additionally, their prediction accuracy is absolutely comparable to more sophisticated models.

The ELlipse Evolution model based on heliospheric imager (HI) observations (ELEvoHI) assumes an elliptic frontal shape within the ecliptic plane and allows the CME to adjust to the ambient solar wind speed, i.e. it is drag-based. ELEvoHI is used as an ensemble simulation by varying the CME frontal shape within given boundary values. The results include a frequency distribution of predicted arrival time and arrival speed and an estimation of the arrival probability.

In this study, we investigate the possibility of not only varying the parameters related to the CME's ecliptic extent but also the ambient solar wind speed for each CME ensemle member. Although we have used a range of +/-100 km/s for possible values of the solar wind speed in the past, only the best candidate was in the end used to contribute to the prediction. We present the results of this approach by applying it to a CME propagating in a highly structured solar wind and compare the frequency distribution of the arrival time and speed predictions to those of the usual ELEvoHI approach.

How to cite: Amerstorfer, T., Hinterreiter, J., Reiss, M. A., Davies, J. A., Möstl, C., Weiss, A. J., Bauer, M., Amerstorfer, U. V., Bailey, R. L., and Harrison, R. A.: Effect of the ambient solar wind speed on drag-based CME prediction accuracy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8932, https://doi.org/10.5194/egusphere-egu21-8932, 2021.

EGU21-8951 | vPICO presentations | ST4.3

Magnetospheric response to solar wind driving

Tatiana Výbošťoková, Zdeněk Němeček, and Jana Šafránková

Interaction of solar events propagating throughout the interplanetary space with the magnetic field of the Earth may result in disruption of the magnetosphere. Disruption of the magnetic field is followed by the formation of the time-varying electric field and thus electric current is induced in Earth-bound structures such as transmission networks, pipelines or railways. In that case, it is necessary to be able to predict a future state of the magnetosphere and magnetic field of the Earth. The most straightforward way would use geomagnetic indices. Several studies are investigating the relationship of the response of the magnetosphere to changes in the solar wind with motivation to give a more accurate prediction of geomagnetic indices during geomagnetic storms. To forecast these indices, different approaches have been attempted--from simple correlation studies to neural networks.

We study the effects of interplanetary shocks observed at L1 on the Earth's magnetosphere with a database of tens of shocks between 2009 and 2019. Driving the magnetosphere is described as integral of reconnection electric field for each shock. The response of the geomagnetic field is described with the SYM-H index. We created an algorithm in Python for prediction of the magnetosphere state based on the correlation of solar wind driving and magnetospheric response and found that typical time-lags range between tens of minutes to maximum 2 hours. The results are documented by a large statistical study.

How to cite: Výbošťoková, T., Němeček, Z., and Šafránková, J.: Magnetospheric response to solar wind driving, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8951, https://doi.org/10.5194/egusphere-egu21-8951, 2021.

EGU21-9854 | vPICO presentations | ST4.3

Predicting geo-effectiveness of CMEs with EUHFORIA coupled to OpenGGCM

Anwesha Maharana, Camilla Scolini, Joachim Raeder, and Stefaan Poedts

The EUropean Heliospheric FORecasting Information Asset (EUHFORIA, Pomoell and Poedts, 2018) is a physics-based heliospheric and CME propagation model designed for space weather forecasting. Although EUHFORIA can predict the solar wind plasma and magnetic field parameters at Earth, it is not designed to evaluate indices like Disturbance-storm-time (Dst) or Auroral Electrojet (AE) that quantify the impact of the magnetized plasma encounters on Earth’s magnetosphere. To overcome this limitation, we coupled EUHFORIA with Open Geospace General Circulation Model (OpenGGCM, Raeder et al, 1996) which is a magnetohydrodynamic model of Earth’s magnetosphere. In this coupling, OpenGGCM takes the solar wind and interplanetary magnetic field obtained from EUHFORIA simulation as input to produce the magnetospheric and ionospheric parameters of Earth. We perform test runs to validate the coupling with real CME events modelled using flux rope models like Spheromak and FRi3D. We compare these simulation results with the indices obtained from OpenGGCM simulations driven by the measured solar wind data from spacecrafts like WIND. We further discuss how the choice of CME model and observationally constrained parameters influences the input parameters, and hence the geomagnetic disturbance indices estimated by OpenGGCM. We highlight limitations of the coupling and suggest improvements for future work. 

How to cite: Maharana, A., Scolini, C., Raeder, J., and Poedts, S.: Predicting geo-effectiveness of CMEs with EUHFORIA coupled to OpenGGCM, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9854, https://doi.org/10.5194/egusphere-egu21-9854, 2021.

EGU21-10254 | vPICO presentations | ST4.3

The CME arrival prediction with the Effective Acceleration Model: Further testing with heliospheric imaging observations

Evangelos Paouris, Angelos Vourlidas, Athanasios Papaioannou, and Anastasios Anastasiadis

The estimation of the Coronal Mass Ejection (CME) arrival is an open issue in the field of Space Weather. Many models have been developed to predict Time-of-Arrival (ToA). In this work, we utilize an updated version of the Effective Acceleration Model (EAM) to calculate the ToA. The EAM predicts the ToA of the CME-driven shock and the sheath's average speed at 1 AU. The model assumes that the interaction between the ambient solar wind and the interplanetary CME (ICME) results in constant acceleration or deceleration. We recently compared EAM against ENLIL and drag based models (DBEM) with a sample of 16 CMEs. We confirmed the well-known fact that the deceleration of fast ICMEs in the interplanetary medium is not captured by most models. We study further the deceleration of fast ICMEs by introducing, for the first time, wide-angle observations by the STEREO heliospheric imagers into the EAM model. The speed profiles for some test cases show deceleration in the interplanetary medium at greater distances compared with the field-of-view of the coronagraphs.

How to cite: Paouris, E., Vourlidas, A., Papaioannou, A., and Anastasiadis, A.: The CME arrival prediction with the Effective Acceleration Model: Further testing with heliospheric imaging observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10254, https://doi.org/10.5194/egusphere-egu21-10254, 2021.

EGU21-10325 | vPICO presentations | ST4.3

On the prediction of magnetic field vectors of ICME using data constrained simulation with EUHFORIA

Ranadeep Sarkar, Jens Pomoell, Eleanna Asvestari, Emilia Kilpua, Marilena Mierla, Luciano Rodriguez, and Stefaan Poedts

Coronal mass ejections (CMEs), the most violent eruptive phenomena occurring in the heliosphere, erupt in the form of gigantic clouds of magnetized plasma from the Sun and can reach Earth within several hours to days. If the magnetic field inside an Earth-directed CME or its associated sheath region has a southward directed component (Bz), then it interacts stronger with the Earth’s magnetosphere, leading to severe geomagnetic storms. Therefore, it is crucial to predict the magnitude and orientation of Bz inside an Earth impacting interplanetary CME (ICME) in order to forecast the intensity of the resulting geomagnetic storms. However, due to lack of realistic inputs and the complexity of the Sun-Earth system in a time-dependent heliospheric context, it is very difficult to perform a reliable forecast of Bz at 1 AU.  

In this work, we use recently developed observational techniques to constrain the kinematic and magnetic properties of CME flux ropes. Using those observational properties as realistic inputs, we construct an analytical force free flux rope model to mimic the magnetic structure of a CME and simulate its evolution from Sun to Earth using the “European heliospheric forecasting information asset” (EUHFORIA). In order to validate our tool, we simulate an Earth-directed CME event on 2013 April 11 and compare the simulation results with the in-situ observations at 1 AU. Further, we assess the performance of EUHFORIA in forecasting of Bz, using different flux rope models like spheromak and torus.  The results obtained from this study help to improve our understanding to build the steppingstones towards the forecasting of Bz in near real time.

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: Sarkar, R., Pomoell, J., Asvestari, E., Kilpua, E., Mierla, M., Rodriguez, L., and Poedts, S.: On the prediction of magnetic field vectors of ICME using data constrained simulation with EUHFORIA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10325, https://doi.org/10.5194/egusphere-egu21-10325, 2021.

EGU21-11605 | vPICO presentations | ST4.3

Predicting geo-effectiveness of CMEs using a novel 3D CME model FRi3D integrated into EUHFORIA 

Stefaan Poedts, Anwesha Maharana, Camilla Scolini, and Alexey Isavnin

Previous studies of Coronal Mass Ejections (CMEs) have shown the importance of understanding their geometrical structure and internal magnetic field configuration for improving forecasting at Earth. The precise prediction of the CME shock and the magnetic cloud arrival time, their magnetic field strength and the orientation upon impact at Earth is still challenging and relies on solar wind and CME evolution models and precise input parameters. In order to understand the propagation of CMEs in the interplanetary medium, we need to understand their interaction with the complex features in the magnetized background solar wind which deforms, deflects and erodes the CMEs and determines their geo-effectiveness. Hence, it is important to model the internal magnetic flux-rope structure in the CMEs as they interact with CIRs/SIRs, other CMEs and solar transients in the heliosphere. The spheromak model (Verbeke et al. 2019) in the heliospheric wind and CME evolution simulation EUHFORIA (Pomoell and Poedts, 2018), fits well with the data near the CME nose close to its axis but fails to predict the magnetic field in CME legs when these impact Earth (Scolini et al. 2019). Therefore, we implemented the FRi3D stretched flux-rope CME model (Isavnin, 2016) in EUHFORIA to model a more realistic CME geometry. Fri3D captures the three-dimensional magnetic field structure with parameters like skewing, pancaking and flattening that quantify deformations experienced by an interplanetary CME. We perform test runs of real CME events and validate the ability of FRi3D coupled with EUHFORIA in predicting the CME geo-effectiveness. We have modeled two real events with FRi3D. First, a CME event on 12 July 2012 which was a head-on encounter at Earth. Second, the flank CME encounter of 14 June 2012 which did not leave any magnetic field signature at Earth when modeled with Spheromak. We compare our results with the results from non-magnetized cone simulations and magnetized simulations employing the spheromak flux-rope model. We further discuss how constraining observational parameters using the stretched flux rope CME geometry in FRi3D affects the prediction of the magnetic field strength in our simulations, highlighting improvements and discussing future perspective.

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: Poedts, S., Maharana, A., Scolini, C., and Isavnin, A.: Predicting geo-effectiveness of CMEs using a novel 3D CME model FRi3D integrated into EUHFORIA , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11605, https://doi.org/10.5194/egusphere-egu21-11605, 2021.

EGU21-13434 | vPICO presentations | ST4.3

Investigating the drag-based model parameters through statistical methods

Gianluca Napoletano, Raffaello Foldes, Francesco Berrilli, Daniele Calchetti, Giancarlo de Gasperis, Dario Del Moro, Ajay Kumar Tiwari, Jannis Teunissen, and Enrico Camporeale

Due to their simplicity and relatively short computational time, empirical models for Solar Wind Transients, based on a restricted number of assumptions and on the values of a small set of parameters, play an important role in Space Weather forecasting. For this reason, an optimal choice of values for the model parameters is of critical importance in this approach. In this work, we compiled a list of CME events by merging and cross-referencing several databases and made use of such experimental data to evaluate statistical distributions for the model parameters of a chosen forecasting model for ICME arrivals, namely the Drag-Based model. Our results lead to several considerations and refinements to be implemented in the future in this and other forecasting models.

How to cite: Napoletano, G., Foldes, R., Berrilli, F., Calchetti, D., de Gasperis, G., Del Moro, D., Kumar Tiwari, A., Teunissen, J., and Camporeale, E.: Investigating the drag-based model parameters through statistical methods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13434, https://doi.org/10.5194/egusphere-egu21-13434, 2021.

EGU21-14187 | vPICO presentations | ST4.3

Comparative study of halo CME arrival predictions

Emiliya Yordanova, Mateja Dumbovic, Manuela Temmer, Camilla Scolini, Jasmina Magdalenic, William J. Thompson, Luca Sorriso-Valvo, Andrew P. Dimmock, and Lisa Rosenqvist

Halo coronal mass ejections (CMEs) are one of the most effective drivers of intense geomagnetic storms. Despite the recent advances in space weather forecasting, the accurate arrival prediction of halo CMEs remains a challenge.  This is because in general CMEs interact with the background solar wind during their propagation in the interplanetary space. In addition, in the case of halo CMEs, the accurate estimation of their kinematics is difficult due to projection effects in the plane-of-sky.

In this study, we are revisiting the arrival of twelve geoeffective Earth-directed fast halo CMEs using an empirical and a numerical approaches. For this purpose we refine the input to the Drag-based Model (DBM) and to the EUropean Heliospheric Forecasting Information Asset (EUHFORIA), which are recently available for users from the ESA Space Situational Awareness Portal (http://swe.ssa.esa.int).

The DBM model has been tested using different values for the input drag parameter.  On average, the predicted arrival times are confined in the range of ± 10 h. The closest arrival to the observed one has been achieved with a drag value higher than the recommended for fast CMEs. Setting a higher drag also helped to obtain a closer to the observed CME arrival speed prediction. These results suggest that the exerted solar wind drag was higher than expected. Further, we are searching for clues about the CME propagation by performing EUHFORIA runs using the same CME kinematics. Preliminary results show that both models perform poorly for CMEs that have possibly undergone CME-CME interaction, underlying again the importance of taking into account the state of the interplanetary space in the CME forecast.

How to cite: Yordanova, E., Dumbovic, M., Temmer, M., Scolini, C., Magdalenic, J., J. Thompson, W., Sorriso-Valvo, L., P. Dimmock, A., and Rosenqvist, L.: Comparative study of halo CME arrival predictions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14187, https://doi.org/10.5194/egusphere-egu21-14187, 2021.

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