The “Theory and Simulation of Solar System Plasmas” session solicits presentations of the latest results from theoretical investigations and numerical simulations in space plasma-physics from microscopic to global scales, in comparison with experiments and observations in the heliosphere: at the Sun, in the solar corona, in interplanetary space and in planetary magnetospheres. There are challenging questions in fundamental solar system plasma physics which require the analyses of huge amounts of data, in particular of the particle kinetics. Machine learning techniques have to be used. We further encourage presentations of theory and simulation results relevant to current, forthcoming and proposed space missions. Each year a topic of special interest is chosen as a focus of the session. For 2021 this focus will be on synergies between observations in the solar wind made by Solar Orbiter and Parker Solar Probe with theory and simulation.

Convener: Giovanni Lapenta | Co-conveners: Philippa Browning, Jörg Büchner, Shangbin Yang
vPICO presentations
| Mon, 26 Apr, 11:00–12:30 (CEST), 13:30–15:00 (CEST)

vPICO presentations: Mon, 26 Apr

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,, 2021.

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,

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,


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,, 2021.

Lei Ni

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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.


  • 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,, 2021.

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,, 2021.

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,, 2021.

Lunch break
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,, 2021.

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,, 2021.

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,, 2021.

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.


  • 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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

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,, 2021.

Wen Liu, Jinsong Zhao, Huasheng Xie, and Dejin Wu

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,, 2021.

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,, 2021.

Gabriel Voitcu and Marius Echim
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,, 2021.

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,, 2021.

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,, 2021.

Jun Lin and Jing Ye

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,, 2021.