NP6.3

EDI
Turbulence, magnetic reconnection, shocks, and instabilities: non-linear processes in space, laboratory, and astrophysical plasmas.

This session focuses on the non-linear processes that take place in space, laboratory and astrophysical plasma. These processes are usually not separated from one another and often go "hand in hand". Just to mention a few examples, magnetic reconnection is an established ingredient of the turbulence cascade and it is also responsible for the production of turbulence in reconnection outflows; shocks may form in collisional and collisionless reconnection processes and can be responsible for turbulence formation, as for instance in the turbulent magnetosheath; magnetic and velocity-shear driven instabilities triggers plasma turbulence in their non-linear phase and can locally develop in turbulent plasmas. All these non-linear processes are responsible for particle acceleration and plasma heating in the environments where they take place.

We are now in a fortunate time for the investigation of these processes, where we can use a combined approach based on simulations and observations together. Simulations can deliver output in a temporal and spatial range of scales going from fluid to electron kinetic. On the observation side, high cadence measurements of particles and fields, high resolution 3D measurements of particle distribution functions and multipoint measurements make it easier to reconstruct the 3D space surrounding the spacecrafts. In this context, the Parker Solar Probe and the Solar Orbiter mission are opening new research scenarios in heliophysics, providing a consistent amount of new data to be analysed.

This session welcomes simulations, observational, and theoretical works relevant for the study of the above mentioned plasma processes. Particularly welcome this year, will be works focusing on how non-linear processes accelerate particles and produce heating in collisionless plasmas. We also encourage papers proposing new methods in simulation techniques and data analysis, as for example those rooted in Artificial Intelligence and Machine Learning.

Co-organized by ST1
Convener: Francesco PucciECSECS | Co-conveners: Maria Elena Innocenti, Yan YangECSECS, Giovanni Lapenta
Presentations
| Fri, 27 May, 10:20–11:50 (CEST), 13:20–16:40 (CEST)
 
Room 0.94/95

Presentations: Fri, 27 May | Room 0.94/95

Chairpersons: Francesco Pucci, Maria Elena Innocenti
10:20–10:25
Magnetic Reconnection
10:25–10:30
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EGU22-1577
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ECS
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Presentation form not yet defined
Haomin Sun, Yan Yang, Quanming Lu, San Lu, Minping Wan, and Rongsheng Wang

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

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

10:30–10:35
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EGU22-1485
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Virtual presentation
Seiji Zenitani, Momoka Yamamoto, and Takahiro Miyoshi

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

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

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

10:35–10:40
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EGU22-11807
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ECS
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Highlight
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Virtual presentation
Jeffersson Andres Agudelo Rueda, Daniel Verscharen, Robert T. Wicks, Christopher J. Owen, Andrew P. Walsh, and Kai Germaschewski
Turbulence and magnetic reconnection are at the core of the long-standing problem of energy dissipation in collisionless plasmas. More than two decades of research on magnetic reconnection have led us to understand the characteristic plasma flows and particle agyrotropy patterns present in collisionless reconnection events. However, it is still not clear what the agyrotropy patterns associated with reconnection events are that form in a turbulent cascade. In this work, we use an explicit fully kinetic particle-in-cell code to study the plasma particles’ agyrotropy associated with three-dimensional small-scale magnetic reconnection events generated by anisotropic and Alfvénic decaying turbulence. We select one reconnection event involving two reconnecting flux ropes. Although we observe similarities with agyrotropy patterns known from two-dimensional steady-state reconnection events, the agyrotropy patterns in our event are more complex. This has further implications for the energy transfer channels available in three-dimensional turbulent reconnection.
 

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

10:40–10:45
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EGU22-11524
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ECS
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Virtual presentation
Julia E. Stawarz, Jonathan P. Eastwood, Tai Phan, Imogen L. Gingell, Prayash S. Pyakurel, Michael A. Shay, Sadie L. Robertson, Christopher T. Russell, and Olivier Le Contel

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

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

10:45–10:50
10:50–10:55
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EGU22-6722
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Virtual presentation
Qiaowen Luo, Jiansen He, and Jun Cui

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

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

10:55–11:00
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EGU22-5192
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Virtual presentation
Tak Chu Li, Yi-Hsin Liu, Yi Qi, and Christopher T. Russell

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

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

11:00–11:05
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EGU22-12840
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ECS
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Virtual presentation
Igor Paramonik, Andrey Divin, Ivan Zaitsev, and Vladimir Semenov

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

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

11:05–11:10
11:10–11:15
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EGU22-6378
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ECS
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Highlight
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Virtual presentation
Ivan Zaitsev, Andrey Divin, Urs Ganse, Yann Pfau-Kempf, Markus Battarbee, Markku Alho, Jonas Suni, Maxime Grandin, Lucile Turc, Giulia Cozzani, Maarja Bussov, Maxime Dubart, Harriet George, Konstantinos Horaites, Konstantinos Papadakis, Talgat Manglayev, Vertti Tarvus, Honyang Zhou, and Minna Palmroth

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

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

11:15–11:20
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EGU22-11660
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ECS
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On-site presentation
Adrian LaMoury, Heli Hietala, Jonathan Eastwood, Laura Vuorinen, and Ferdinand Plaschke

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

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

11:20–11:25
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EGU22-8160
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ECS
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On-site presentation
Madhurjya Changmai and Rony Keppens

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

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

11:25–11:30
Particle Acceleration
11:30–11:35
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EGU22-2116
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Virtual presentation
Bojing Zhu, Yan Li, and Jun Lin

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

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

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

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

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

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

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

11:35–11:40
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EGU22-11028
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ECS
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Virtual presentation
Die Duan, Jiansen He, Xingyu Zhu, Rui Zhuo, Ziqi Wu, and Liu Yang
The acceleration and heating of solar wind particles by energy dissipation in the magnetic reconnection is an important problem in space physics. Although alpha particles are the second most abundant element in the solar wind, their dynamical behavior in the magnetic reconnection of the solar wind is not well understood. Using the high energy (1500~3000 eV) part of the SWA/PAS instrument on board the Solar Orbiter, we study the kinetic behavior of alpha particles in a magnetic-reconnetion exhaust region within a heliospheric current sheet. In this event, protons and alpha particles have similar bulk velocities. Alpha particles are accelerated and form a jet in the exhaust region. The counter-stream distribution of alpha particles is observed inside the exhuast region, which changes the direction from parallel to perpendicular to the magnetic field direction when the magnetic field is reversed. In addition, a pair of the slow shock/rotational discontinuity is observed in the exhuast region. The exhaust region is heated and bounded by the slow shocks , while the accelerated plasma jet is bounded by the rotational discontinuities.

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

11:40–11:45
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EGU22-6084
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On-site presentation
Marian Lazar, Rodrigo Lopez, Hamd Shaaban, Stefaan Poedts, Horst Fichtner, and Peter Yoon

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

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

11:45–11:50
Lunch break
Chairpersons: Maria Elena Innocenti, Francesco Pucci
Shocks
13:20–13:25
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EGU22-3546
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Presentation form not yet defined
Natalia Borodkova, Olga Sapunova, Victor Eselevich, Georgy Zastenker, and Yury Yermolaev

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

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

13:25–13:30
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EGU22-5222
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ECS
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Presentation form not yet defined
Olga Sapunova, Natalia Borodkova, Yuri Yermolaev, and Georgii Zastenker

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

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

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

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

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

13:30–13:35
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EGU22-10688
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Presentation form not yet defined
Oksana Kruparova, Vratislav Krupar, and Adam Szabo

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

 

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

13:35–13:40
13:40–13:45
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EGU22-9885
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Presentation form not yet defined
Yuri Khotyaintsev, Ahmad Lalti, Andrew P. Dimmock, Andreas Johlander, and Daniel B. Graham

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

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

13:45–13:50
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EGU22-5560
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ECS
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On-site presentation
Ajay Lotekar, Yuri Khotyaintsev, Daniel Graham, Andrew Dimmock, Ahmad Lalti, and Andreas Johlander

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

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

13:50–13:55
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EGU22-4447
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ECS
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On-site presentation
Andreas Johlander, Andrew Dimmock, Yuri Khotyaintsev, Daniel Graham, and Ahmad Lalti

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

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

13:55–14:00
14:00–14:05
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EGU22-915
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ECS
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Virtual presentation
Sergey Kamaletdinov, Ivan Vasko, Anton Artemyev, and Rachel Wang

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

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

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

14:05–14:10
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EGU22-3631
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On-site presentation
Philippe Savoini and Bertrand Lembege

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

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

14:10–14:15
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EGU22-8962
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Virtual presentation
Laurent Muschietti, Bertrand Lembege, and Viktor Decyk

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

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

14:15–14:20
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EGU22-3354
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ECS
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Virtual presentation
Jin Guo, San Lu, Quanming Lu, Yu Lin, Xueyi Wang, Yufei Hao, Kai Huang, Rongsheng Wang, and Xinliang Gao

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

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

14:20–14:25
Turbulence
14:25–14:30
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EGU22-11945
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ECS
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Highlight
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Virtual presentation
Juska Soljento, Simon Good, Adnane Osmane, and Emilia Kilpua

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

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

14:30–14:35
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EGU22-3198
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ECS
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Virtual presentation
Jonathan Tessier, Francis J. Poulin, and David W. Hughes

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

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

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

14:35–14:40
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EGU22-12159
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Presentation form not yet defined
Valentina Zharkova and Qian Xia

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

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

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

14:40–14:50
Coffee break
Chairpersons: Francesco Pucci, Maria Elena Innocenti
15:10–15:15
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EGU22-8705
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On-site presentation
Luca Franci, Emanuele Papini, Alfredo Micera, Lorenzo Matteini, Julia Stawarz, Giovanni Lapenta, David Burgess, Petr Hellinger, Simone Landi, Andrea Verdini, and Victor Montagud-Camps

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

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

15:15–15:20
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EGU22-4040
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ECS
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Virtual presentation
Giuseppe Arrò, Francesco Califano, and Giovanni Lapenta

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

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

 

References

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

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

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

15:20–15:25
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EGU22-2649
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ECS
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Virtual presentation
Thanapon Aiamsai, Peera Pongkitiwanichakul, Rungployphan Kieokaew, David Ruffolo, and Theerasarn Pianpanit

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

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

15:25–15:30
15:30–15:35
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EGU22-1740
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ECS
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On-site presentation
Alexander Pitna, Jana Safrankova, Zdenek Nemecek, Gilbert Pi, Luca Franci, and Byeongseon Park

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

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

15:35–15:40
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EGU22-1997
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On-site presentation
Otman Ben Mahjoub and Aziz Ouadoud

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

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

15:40–15:45
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EGU22-7371
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ECS
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On-site presentation
Rajab Ismayilli and Tom Van Doorsselaere

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

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

15:45–15:50
Waves and Instabilities
15:50–15:55
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EGU22-7354
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ECS
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Presentation form not yet defined
Vertti Tarvus, Lucile Turc, Hongyang Zhou, Giulia Cozzani, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Markus Battarbee, Maarja Bussov, Maxime Dubart, Harriet George, Maxime Grandin, Konstantinos Horaites, Talgat Manglayev, Konstantinos Papadakis, Jonas Suni, Ivan Zaitsev, and Minna Palmroth

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

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

15:55–16:00
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EGU22-7069
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ECS
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On-site presentation
Giulia Cozzani, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Jonas Suni, Maxime Grandin, Lucile Turc, Ivan Zaitsev, Maarja Bussov, Maxime Dubart, Harriet George, Konstantinos Horaites, Talgat Manglayev, Konstantinos Papadakis, Vertti Tarvus, Honyang Zhou, and Minna Palmroth

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

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

16:00–16:05
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EGU22-3868
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ECS
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Virtual presentation
Alexander Lukin, Anton Artemyev, and Anatoly Petrukovich

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

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

16:05–16:10
16:10–16:15
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EGU22-9788
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ECS
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Highlight
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On-site presentation
Joshua Wiggs and Chris Arridge

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

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

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

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

16:15–16:20
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EGU22-5068
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ECS
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On-site presentation
Ahmad Lalti, Yuri Khotyaintsev, Daniel Graham, Konrad Steinvall, and Andreas Johlander

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

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

16:20–16:25
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EGU22-12114
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Presentation form not yet defined
Kinetic Instabilities from Ion Beams and Differential Streaming in the Close-Sun Solar Wind: Hybrid Expanding Simulations
(withdrawn)
Lorenzo Matteini, Petr Hellinger, Simone Landi, Luca Franci, Anna Tenerani, and Marco Velli
16:25–16:30
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EGU22-10339
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Virtual presentation
Rodrigo A. López, Alfredo Micera, Marian Lazar, Shaaban M. Shaaban, Stefaan Poedts, and Giovanni Lapenta

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

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

16:30–16:40