Orals: Wed, 30 Apr | Room -2.15
Italy ended research on Nuclear Energy and in response, nuclear engineering faculty at Politecnico di Torino
placed selected students with established plasma physics groups. Gianni Lapenta was the first. He would spend
half a year with Bruno Coppi at MIT, and half a year with me at Los Alamos. When I met Gianni,
he said he liked Boston and Coppi and would prefer to stay there. To my surprise, he arrived in Los Alamos
the following January.
I suggested a problem to Gianni, He published his results in: G. Lapenta and J U Brackbill, Dynamic and selective control of the number
of particles in kinetic plasma simulations, J. Comput. Phys. {\bf{115} }(1994) 213. In another project with semi-conductor manufacturers, we modeled the deposition of 'dust' on large-scale integrated circuits. Our results were published in G. Lapenta, F. Iinoya and J. U. Brackbill, "Particle-in-cell simulation of glow discharges in complex geometries," in IEEE Transactions on Plasma Science, vol 23 no. 4, pp. 769-779. We modeled the interaction of a wafer assembly and the surrounding plasma self-consistently. Gianni did further work on dust charging in a flowing plasma and published the work in Physical Review Letters. He modeled particles that developed dipole moments.
Gianni became a staff member, a US citizen, and a member of the plasma physics group. He began to apply the implicit moment plasma simulation code to study magneitic reconnection. He brought students from Torino, to Los Alamos, among them Paolo Ricci, Stefano Markidis, Jean-Luc Delzanno, and Maria Elena Innocenti., and he published extensively on the lower hybrid instability, colllisionless reconnection, and , later, turbulence.
In 2008, he joined the Mathematics Department at KU Leuven as a professor in Space Weather where he remained until his death in May, 2023. He continued to visit the US to work with Maha Abdallah at UCLA and Marty Goldman at the University of Colorado. I don't know the full breadth of his work, but I know that he was excited to discover that turbulent flow generated self-sustaining magnetic reconnection. With Stefano Markidis, he developed a plasma simulation code on massively parallel computers , and with colleagues at the University of Michigan a method to couple magnetohydrodynamic and kinetic simulation. My favorite paper appeared in Ap. J. in 2021 on 'Detecting reconnection sites using the Lorentz transformations for electromagnetic fields'. His method is a simple and reliable way to identify reconnection sites in plasma simulations.
Gianni and I were friends for many years. We talked when he was diagnosed with cancer. He was upset by the grim prognosis. So many things he had looked forward to were now out of reach, including a visit with us in Los Alamos. He died 28 May 2023 at his home in Italy.
How to cite: Brackbill, J.: In Remembrance of Prof. Giovanni Lapenta, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14612, https://doi.org/10.5194/egusphere-egu25-14612, 2025.
The study of space plasmas at the kinetic scale has seen rapid growth in recent years due to the exponential increase in computational power and more accurate in-situ measurements. Both numerical simulations and observations have revealed a clear transition across ion scales from the magnetohydrodynamic (MHD) to the kinetic regime, characterized by different physical phenomena dominating the turbulent properties and the heating of plasmas. Several studies have associated the so-called ion break with magnetic reconnection, which is considered responsible for injecting energy into this range, thereby driving the sub-ion energy cascade.
In this work, we analyze a 2D3V hybrid-Vlasov simulation of forced plasma turbulence using the space-filtering (or coarse-graining) technique, which allows for a simultaneous investigation of energy transfer properties as a function of scale, space, and time. Using this approach, we quantitatively show, for the first time, that magnetic reconnection in non-collisional plasmas is associated with dual energy transfer across ion scales, bridging the MHD and kinetic regimes. The onset of reconnection events triggers the formation of sub-ion scale turbulent fluctuations and plays a crucial role in the appearance of an inverse energy transfer regime originating at these sub-ion scales.
How to cite: Foldes, R., Cerri, S. S., Marino, R., and Camporeale, E.: Evidence of dual energy transfer driven by magnetic reconnection at sub-ion scales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3117, https://doi.org/10.5194/egusphere-egu25-3117, 2025.
In quasi-parallel shock waves, turbulence occurs in the shock transition region due to instabilities such as the ion-ion beam instability, which eventually bends magnetic field lines and current sheets are produced. There are two types of current sheets in the shock turbulence region: reconnecting current sheets and non-reconnecting current sheets. In the Earth’s bow shock, NASA’s Magnetospheric Multiscale (MMS) has been observing many current sheets, some of which show evidence of magnetic reconnection and energetic accelerated particles.
We study electron acceleration in the Earth’s quasi-parallel bow shock by means of 2D particle-in-cell (PIC) simulation. We discuss differences in properties in reconnecting and non-reconnecting current sheets. Reconnecting current sheets and magnetic islands produced by reconnection show significant heating and energetic particles, and several acceleration mechanisms work in these regions: Fermi acceleration, Hall electric field acceleration, and island betatron acceleration. We also demonstrate that electrons are energized in non-reconnecting current sheets. In some regions in turbulence, an elongated, extending current sheet is formed, and electrons can be accelerated by the perpendicular electric field inside the non-reconnecting current sheet. We compare the efficiency between the acceleration mechanisms in reconnection regions and non-reconnecting current sheets.
How to cite: Bessho, N., Chen, L.-J., Hesse, M., Ng, J., Wilson III, L. B., Stawarz, J. E., and Madanian, H.: Electron acceleration in reconnecting and non-reconnecting current sheets in the Earth's quasi-parallel bow shock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4634, https://doi.org/10.5194/egusphere-egu25-4634, 2025.
Recent observations by Parker Solar Probe (PSP) suggest that protons and heavier ions are accelerated to high energies by magnetic reconnection at the heliospheric current sheet (HCS). In this work I discuss the compression acceleration of protons and heavier ions as a source of energetic particles in the reconnecting HCS, by solving the energetic particle transport equation in large-scale MHD simulations. The multi-ion acceleration results in nonthermal power-law energy distributions, whose spectral index is consistent with PSP observations. Our study shows that the high-energy cutoff of protons can reach Emax ∼ 0.1-1 MeV, depending on the particle diffusion coefficients. The high-energy cutoff of different ion species scales with the charge-to-mass ratio Emax ∝ (Q/M)α, and the particle injection energy can play a role in modifying the scaling factor α, for which we also find a match with the interval α ~ 0.6 - 1.5 observed by PSP.
How to cite: Murtas, G., Li, X., Guo, F., and Haggerty, C.: Compression Acceleration of Protons and Heavier Ions at the Heliospheric Current Sheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7607, https://doi.org/10.5194/egusphere-egu25-7607, 2025.
Turbulence in classical fluids is characterized by persistent structures that emerge from the chaotic landscape. We investigate the analogous process in fully kinetic plasma turbulence by using high-resolution, direct numerical simulations in two spatial dimensions. We observe the formation of long-lived vortices with a profile typical of macroscopic, magnetically dominated force-free states. Inspired by the Harris pinch model for inhomogeneous equilibria, we describe these metastable solutions with a self-consistent kinetic model in a cylindrical coordinate system centered on a representative vortex, starting from an explicit form of the particle velocity distribution function. Such new equilibria can be simplified to a Gold–Hoyle solution of the modified force-free state. Turbulence is mediated by the long-lived structures, accompanied by transients in which such vortices merge and form self-similarly new metastable equilibria. This process can be relevant to the comprehension of various astrophysical phenomena, going from the formation of plasmoids in the vicinity of massive compact objects to the emergence of coherent structures in the heliosphere.
M. Imbrogno et al, "Long-lived Equilibria in Kinetic Astrophysical Plasma Turbulence", The Astrophysical Journal Letters 972, L5 (2024)
How to cite: Servidio, S.: Long-lived Equilibria in Kinetic Astrophysical Plasma Turbulence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3059, https://doi.org/10.5194/egusphere-egu25-3059, 2025.
Formation of a magnetic coherent structure via the merger of two plasmoids at solar supergranular junctions
Abraham C.-L. Chian, Erico L. Rempel, Luis Bellot Rubio, Milan Gosic, and Yasuhito Narita
We discuss the formation of a large magnetic coherent structure in a vortex expansion–contraction interval, resulting from the merger of two plasmoids driven by a supergranular vortex observed by Hinode in the quiet-Sun (Chian et al., MNRAS 535, 2436, 2024). Strong vortical flows at the interior of vortex boundary are detected by the localized regions of high values of the instantaneous vorticity deviation, and intense current sheets in the merging plasmoids are detected by the localized regions of high values of the local current deviation. The spatiotemporal evolution of the line-of-sight magnetic field, the horizontal electric current density, and the horizontal electromagnetic energy flux is investigated by elucidating the relation between velocity and magnetic fields in the photospheric plasma turbulence. A local and continuous amplification of magnetic field from 286 G to 591 G is detected at the centre of one merging plasmoid during the vortex expansion–contraction interval of 60 min. During the period of vortex contraction of 22.5 min, the line-of-sight magnetic field at the centre of plasmoid-1 (2) exhibits a steady decrease (increase), respectively, indicating a steady transfer of magnetic flux from plasmoid-1 to plasmoid-2. At the end of the vortex expansion–contraction interval, the two merging plasmoids reach an equipartition of electromagnetic energy flux, leading to the formation of an elongated magnetic coherent structure encircled by a shell of intense current sheets. Evidence of the disruption of a thin current sheet at the turbulent interface boundary layers of two merging plasmoids is presented.
How to cite: Chian, A. C. L., Rempel, E. L., Bellot Rubio, L., Gosic, M., and Narita, Y.: Formation of a magnetic coherent structure via the merger of two plasmoids at solar supergranular junctions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3200, https://doi.org/10.5194/egusphere-egu25-3200, 2025.
The Kelvin-Helmholtz instability (KHI) at the Earth's magnetospheric flanks plays a critical role in driving plasma dynamics, particularly during northward interplanetary magnetic field periods, in which the KHI is active at the low latitude magnetopause. This instability arises due to the velocity shear between solar wind and magnetospheric plasma, forming vortex structures that drive plasma mixing and magnetic reconnection. These vortices generate turbulence and enable the transfer of energy, momentum, and particles across the magnetopause. As a result, the KHI significantly impacts processes like plasma transport and particle acceleration in planetary magnetospheres.
To investigate the small-scale physics of these processes, we performed high-resolution two-dimensional (2D) fully kinetic particle-in-cell (PIC) simulations using the ECsim code. ECsim stands out as a PIC code that has the unique property of conserving energy to machine precision, which is essential for accurately modeling physical systems where energy transfer is of prime importance. Our simulations focus on conditions characteristic of the Earth's magnetospheric flanks, where the KHI develops and evolves. By examining different plasma parameters, concentrating on particle velocity distribution functions and temperature anisotropies, we analyze the microphysical processes driving plasma mixing and particle energization, with a particular focus on electron physics, which is captured here in full.
How to cite: Ferro, S. and Bacchini, F.: Fully Kinetic Simulations of Plasma Transport and Particle Energization Induced by the Kelvin-Helmholtz Instability at the Earth’s Magnetopause, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6474, https://doi.org/10.5194/egusphere-egu25-6474, 2025.
Plasma systems exhibit complex multiscale dynamics that require full kinetic models for accurate representation. Explicit kinetic schemes are easy implemented but require time steps finely resolved to the plasma period and suffer from numerical heating, while implicit schemes ensure stability but at the expense of computationally intensive nonlinear solvers. Semi-implicit methods strike a balance between efficiency and stability, but struggle to conserve energy, leading to potential instabilities. While ECSIM introduced a pioneering energy-conserving semi-implicit PIC framework, developing efficient and unconditionally stable grid-based schemes with energy conservation remains a significant challenge.
We propose an inherently noise-free energy-conserving semi-Lagrangian (ECSL) scheme that retains the efficiency of explicit methods and the stability of implicit approaches. Numerical experiments validate its accuracy, efficiency, and energy conservation, demonstrating ECSL as a promising tool for multiscale plasma simulations.
How to cite: Liu, H. and Lapenta, G.: Energy-Conserving Semi-Lagrangian Scheme for Multiscale Plasma Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12735, https://doi.org/10.5194/egusphere-egu25-12735, 2025.
The study of turbulent magnetic fields is crucial in modern astrophysics due to the omnipresence of plasma in a turbulent state. The state-of-the-art approach to the study of turbulence entails the use of numerical simulations, whose high computational cost unfortunately impedes a large variety of studies. To solve this issue, synthetic turbulence models have been developed, in which turbulent fields are generated analytically at a much lower computational cost.
In the present work we focus on BxC, a Python-based toolkit that generates realistic turbulent magnetic fields through a combination of a geometric and analytical approach. Due to a relatively large set of input parameters, BxC allows for full customization of the statistical properties of the generated fields. Recent developments of the code improve on the possibility to reproduce realistic scenarios, in particular allowing for anisotropic fields and/or ‘structured’ turbulent fields as an alternative to purely turbulent ones.
In view of practical application of the BxC toolkit, the code has been coupled with the MPI-AMRVAC framework, a parallelized finite-volume solver for partial differential equations. This combined framework has then been applied to the study of cosmic rays transport by means of test particle simulations. The presentation will introduce the audience to the combined approach used, highlighting its advantages and focusing on the results obtained from this study.
How to cite: Maci, D., Keppens, R., and Bacchini, F.: Application of the BxC toolkit to the study of cosmic rays transport, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8982, https://doi.org/10.5194/egusphere-egu25-8982, 2025.
In this study, the three - dimensional global hybrid simulation method is employed to explore the magnetic reconnection phenomenon at the magnetopause and the influencing mechanism of magnetosheath (MSH) turbulence on it. The characteristics of magnetic reconnection at the magnetopause downstream of quasi - perpendicular shocks and quasi - parallel shocks are emphatically compared, covering aspects such as the occurrence frequency of magnetic reconnection, the distribution pattern of X - lines, and the energy conversion of J·E. Through the operation of the three - dimensional hybrid simulation program and detailed analysis, the differences in magnetic reconnection at the magnetopause under different shock conditions are presented.This research work provides certain insights for accurately defining the complex relationship between MSH turbulence and magnetic reconnection at the magnetopause. It is expected to enhance the understanding of space plasma physical processes to a certain extent. The research results contribute to understanding the mechanism of the effect of turbulence on the magnetic field topology and energy transfer process in the magnetosphere, and provide references for subsequent research in the field of space physics. For the interpretation of satellite observation data and the construction and improvement of relevant theoretical models of magnetospheric dynamics, this study also has certain enlightenment and reference values, hoping to play a role in promoting the coordinated development of theory and practice in this field.
How to cite: Li, Z., Zhou, M., Yi, Y., and Pang, Y.: A Three - Dimensional Hybrid Simulation Study on the Influence of Magnetosheath Turbulence on Magnetopause Reconnection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3975, https://doi.org/10.5194/egusphere-egu25-3975, 2025.
It is well known that electromagnetic (EM) processes can affect the trapped population of ionized particles in the Earth’s radiation belts and induce particle precipitations that can be measured by satellites. Moreover, in the last decades, several studies have suggested the concurrent occurrence of energetic particle flux variations (the so-called Particle Bursts, PBs) and ionospheric ELF-VLF electromagnetic activity in correspondence to (or even before) large earthquakes. However, to date, the underlying mechanisms connecting seismic-related electromagnetic processes to satellite-detected particle precipitation events remain elusive. In addition, a comprehensive model capable of explaining observed EM perturbations and PBs is still missing, especially during seismo-related phenomena. The lack of detailed investigation into these processes introduces uncertainties regarding the expected time delay between the two phenomena, which hinders the reproducibility and confirmation of reported findings across different studies, even when employing identical methodologies. Consequently, the temporal distribution of claimed seismo-related phenomena exhibits significant variability.
To address these challenges, we present novel numerical simulations investigating wave-particle interactions within a realistic topside ionospheric plasma environment. A hybrid code was successfully employed to simulate the topside ionosphere, incorporating realistic plasma parameters, including plasma beta and species composition. Simulation results demonstrate some modifications in the ion velocity distribution function, including the emergence of fast ion beams capable of inducing particle precipitation. These simulations provide, for the first time, an estimate of the time delay between the onset of EM waves and the resulting plasma modifications.
How to cite: Recchiuti, D., Matteini, L., Franci, L., Papini, E., D'Angelo, G., Diego, P., Ubertini, P., Battiston, R., and Piersanti, M.: Evolution of ion distribution functions in ionospheric plasmas perturbed by Alfvén waves, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6516, https://doi.org/10.5194/egusphere-egu25-6516, 2025.
Magnetic holes (MHs) are coherent structures typically observed in turbulent plasmas, characterized by a sharp decrease in the magnetic field magnitude. MHs exist in different sizes, from magnetohydrodynamic to kinetic scales. Magnetospheric Multiscale (MMS) observations have revealed that electron scale MHs are very common in the turbulent Earth’s magnetosheath, potentially playing an important role in the energy cascade and dissipation. Nevertheless, the origin of MHs is still unclear and debated. In this work, we use fully kinetic simulations, initialized with typical Earth's magnetosheath parameters, to investigate the role of plasma turbulence in generating electron scale MHs. We identify a new turbulent-driven mechanism capable of generating MHs at scales of the order of a few electron inertial lengths. This mechanism involves the following steps: first, large-scale turbulent velocity shears produce localized regions with strong perpendicular electron temperature anisotropy; these regions quickly become unstable, producing oblique whistler waves; then, as whistler fluctuations propagate over the inhomogeneous turbulent background, they develop a quasi-electrostatic component, evolving into Bernstein-like modes; the electric field of Bernstein-like modes produces filamentary electron currents that turn the wave into a train of current vortices; these vortices finally merge into a larger vortex that reduces the local magnetic field magnitude, ultimately evolving into a coherent electron scale MH. This work provides numerical evidence of a turbulence-driven mechanism for the generation of electron-scale MHs. Our results have potential implications for understanding the formation and occurrence of electron scale MHs in the Earth’s magnetosheath and other turbulent environments.
How to cite: Espinoza Troni, J., Arrò, G., Asenjo, F., and Moya, P.: Electron scale magnetic holes generation driven by Whistler-to-Bernstein mode conversion in fully kinetic plasma turbulence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12337, https://doi.org/10.5194/egusphere-egu25-12337, 2025.
Magnetic reconnection is often considered to be the most fundamental mechanism for the release of magnetic energy in various plasma systems. Electron current layer (ECL) in the diffusion region plays an important role on energy dispassion during collisionless magnetic reconnection. ECL splits into two sublayers and is maintained at the electron inertial scale, not long after the triggering of anti-parallel magnetic reconnection. By performing 2D particle-in-cell (PIC) simulations with high-resolution grids, we investigate the energy transfer and dissipation of electron current layer during anti-parallel magnetic reconnection. Starting from the energy equation of the two-fluid model, we examine the energy transfer and transports in the vicinity of the ECL through a point-by-point analysis of heating and acceleration, and obtain a new image of the energy conversion in the ECL sublayers. In this work, instead of determining the overall energy budget in a fixed-box, we rather chose to distinguish the diffusion into multiple variational regions to calculate the transfer of energy as the reconnection progressed. By combining calculations based on macroscopic energy equations and analysis of phase space electrodynamics, we find the mechanism of electron thermalization and acceleration in the diffusion region during anti-parallel magnetic reconnection.
How to cite: Chen, D., Huang, C., Du, A., and Ge, Y.: Energy transfer and dissipation of electron current layer during anti-parallel magnetic reconnection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14631, https://doi.org/10.5194/egusphere-egu25-14631, 2025.
Using Particle-in-Cell simulations, we analyze electron VDFs that reproduce those typically observed in the inner heliosphere and explore the potential role of the electron deficit in triggering kinetic instabilities. Prior studies and in-situ data indicate that strahl electrons can drive oblique whistler waves unstable, leading to their scattering. This process enables suprathermal electrons to access phase-space regions that satisfy resonance conditions with parallel-propagating whistler waves.
How to cite: Innocenti, M. E., Coburn, J., Verscharen, D., and Micera, A.: Whistler Waves and Electron Deficit in the Solar Wind: Insights from Particle-in-Cell Simulations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12621, https://doi.org/10.5194/egusphere-egu25-12621, 2025.
The process of deriving fluid equations from the Vlasov equation for collisionless plasmas involves a fundamental challenge known as the closure problem. This problem consists of the fact that the temporal evolution of any particle moment—such as density, current, pressure, or heat flux—includes terms that depend on the next higher-order moment. Consequently, truncating the description at the nth order necessitates approximating the contributions of the (n+1)th order moment within the evolution equation for the nth moment. The choice of truncation level and the assumptions underlying these approximations play a critical role in determining the accuracy with which the resulting fluid model captures kinetic processes.
The work presented here focuses on reconstructing higher-order moments using only lower-order moments, along with the electric and magnetic fields, as inputs. We apply supervised machine learning to train models that predict higher-order moments, specifically the divergence of the heat flux tensor, in simulations of magnetic reconnection within a Harris current sheet under varying background guide fields. All simulations we use are obtained with the muphy 2 code (Allmann-Rahn et al. 2023). Fully kinetic Vlasov simulations, which provide complete physical information, serve as the ground truth. The reconstructed moments are incorporated into fluid simulations, and their impact on the simulation dynamics is analyzed. We evaluate the models' ability to generalize across different guide field conditions and compare the performance of the machine learning-based closures with commonly used closures in fluid simulations.
How to cite: Köhne, S., Lautenbach, S., Jeß, E., Grauer, R., and Innocenti, M. E.: Reconstructing fluid closures using supervised Machine Learning , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17373, https://doi.org/10.5194/egusphere-egu25-17373, 2025.
Two-dimensional particle-in-cell (PIC) simulations explore the collisionless tearing instability from a Harris equilibrium of a pair (electron-positron) plasma, with no guide field, for a range of parameters from non-relativistic to relativistic temperatures and drift velocities. Growth rates match the predictions of Zelenyi & Krasnosel'skikh (1979) modified for relativistic drifts by Hoshino (2020) as long as the assumption holds that the thickness of the current sheet is larger than the Larmor radius. Aside from confirming these predictions, we explore the transitions from thick to thin current sheets and from classical to relativistic temperatures. We determine a limit for the minimum current thickness to which a current sheet can evolve before the tearing instability sets in. Large-scale astronomical environmental parameters imply significant reconnection of system size current sheets is most likely in regimes with relativistic temperatures, e.g. active galactic nuclei. We also explore the nonlinear evolution of the modes that move to lower wave numbers (especially for thick current sheets with low growth rates) and eventually increase to faster growth rates associated with thinner current sheets before saturating.
How to cite: Schoeffler, K., Eichmann, B., Pucci, F., and Innocenti, M. E.: Particle-in-cell study of the tearing instability for relativistic pair plasmas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17592, https://doi.org/10.5194/egusphere-egu25-17592, 2025.
In computational plasma physics kinetic models are used to simulate plasma phenomena where small scale physics is expected to be of importance. These models contain the full information of the particle velocity distribution function but are computationally expensive. Therefore, computationally cheaper models are utilized, which can then be deployed to larger scales e. g. 10-moment fluid models or magnetohydrodynamics (MHD). However, the large scale behavior is critically influenced by small scale behavior. For example, solar wind observations show that ion and electron scale instabilities constrain the solar wind temperature anisotropy over the entire heliosphere (Berčič et al., 2019; Matteini et al., 2013) and in our group we have recently demonstrated via fully kinetic numerical simulations the non-trivial link between the small and the large scales in heat flux regulation in the solar wind (Micera et al., 2021; Micera et al., 2025). Thus, models are required that can include kinetic processes, in reduced form, into large scale simulations. At the moment, analytical closures are used to close the hierarchy of fluid equations, but these closures are strictly valid only in certain regimes. For example, Landau fluid closures (Hammett & Perkins, 1990; Hunana et al., 2019) assume that the plasma is close to Local Thermodynamic Equilibrium, which is not the case for most space plasmas. Finding suitable closure equations is an ongoing research topic that gets increasingly more difficult in complex systems. In this study, we try to improve fluid models by learning a suitable symbolic closure for the heat flux by applying machine learning methods (Alves & Fiuza, 2022; Long et al., 2019) to data from kinetic simulations.
At first, these methods were tested by learning the lower moment equations using simulation data of the two stream instability.
In the long term, closure equations for more complex systems will be addressed.
How to cite: Jeß, E., Lautenbach, S., Köhne, S., and Innocenti, M. E.: Discovering heat flux closures using machine learning methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17863, https://doi.org/10.5194/egusphere-egu25-17863, 2025.
The magnetopause is the boundary where the solar wind interacts with the Earth's magnetosphere, playing a crucial role in the transfer and exchange of mass, momentum, and energy. The Kelvin-Helmholtz instability (KHI) is widely recognized as a key mechanism facilitating plasma transport across the magnetopause. However, direct observational evidence remains lacking. Using high-resolution data from the Magnetospheric Multiscale (MMS) mission, we investigated a KHI event by quantitatively analyzing the energy conversion rate, anomalous flow velocity, and anomalous diffusion coefficient associated with electromagnetic perturbations across various frequency ranges. Our results demonstrate that both the primary KHI and its internal small-scale structures contribute significantly to energy conversion, with the primary KHI producing larger anomalous flows and diffusion coefficients than its internal structures. The peak anomalous diffusion coefficient driven by the KHI (~2 × 10¹⁰ m²/s) is an order of magnitude greater than that induced by lower-hybrid drift waves in the magnetopause reconnection boundary layers. These findings provide quantitative evidence of the critical role played by the KHI and its internal small-scale structures in plasma transport and energy conversion at the flank region of magnetopause.
How to cite: Zhong, Z., Zhong, P., Zhou, M., Graham, D., Pang, Y., Tang, R., Khotyaintsev, Y., and Deng, X.: Quantitative Analysis of Energy Conversion and Anomalous Transport in Kelvin-Helmholtz Instabilities at the Magnetopause, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6399, https://doi.org/10.5194/egusphere-egu25-6399, 2025.
Understanding the interactions between the solar wind and the magnetosphere requires multi-scale modelling to resolve magnetohydrodynamic, ion and electron kinetic scales, owing to the collisionless character of plasma turbulence. This leads to computational complexity that reduced models aim to address.
In this study, we investigate decaying turbulence in the magnetosheath by performing comparisons between the ECsim (a fully-kinetic Energy Conserving PIC) model and a computationally lighter model Menura (a hybrid PIC). Menura resolves kinetic ion scales but the influence of massless electrons is provided only via the pressure closure in the generalized Ohm’s law. To ensure meaningful comparisons, we have adjusted the initial conditions using parameters consistent with magnetosheath observations.
We present a detailed analysis of the pressure-strain interaction terms, electromagnetic work and cross-scales fluxes, demonstrating relatively good agreement between the two models and validating certain turbulent characteristics for Menura. Our findings confirm several established results from fully kinetic Vlasov and PIC simulations, such as connections between coherent structures and energy conversion. Furthermore, we are extending these insights to a novel magnetosheath regime for a hybrid PIC model, which has generally received less attention in such studies. However, discrepancies were also identified, such as Zenitani measure (electromagnetic work done by the non-ideal electric field) and absolute values of energy dissipation which are model-dependent.
In the effort to further improve electron pressure closure, we train a neural network surrogate on ECsim generated data (high fidelity model). We present preliminary results showing consistent scaling for predicted pressure-strain at future simulation time steps as a function of traceless stress, vorticity and the mean square total current density in a lack of data regime.
How to cite: Miloshevich, G., Arrò, G., Pucci, F., Henri, P., Lapenta, G., and Poedts, S.: Fully kinetic and hybrid PIC modelling of magnetosheath turbulence: closure and dissipation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12278, https://doi.org/10.5194/egusphere-egu25-12278, 2025.
Magnetic reconnection, a fundamental plasma process, explosively releases energy, generates particles with high energies and plays a crucial role in space weather. This process, which is very common in space plasmas, also occurs in Earth’s magnetotail, driving particle acceleration and affecting the plasma dynamics of the near-Earth space environment.
To explore the connection between magnetic reconnection and particle acceleration, we present fully kinetic simulations of magnetic reconnection in Earth's magnetotail, including both ions and electrons. For this purpose, we employed the particle in cell (PIC) code ECsim and set up the simulation with parameters from a well-studied magnetic reconnection event observed by the Magnetospheric Multiscale (MMS) mission. This event, usually referred to as a “quiet magnetic reconnection” event, is characterized by less enhanced plasma heating and turbulence.
Our study first compares the particle energization observed in the MMS data with the results from our simulation for this specific reconnection event. By examining the differences and similarities between the two, we aim to evaluate how well the simulation captures the key features of the observed event. Afterward, we vary the initial parameters to investigate how various reconnection scenarios affect particle acceleration. This approach allows us to analyze how different environmental conditions influence the acceleration of particles during magnetic reconnection.
How to cite: Reisinger, N. and Bacchini, F.: Linking Particle Acceleration to Magnetic Reconnection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9707, https://doi.org/10.5194/egusphere-egu25-9707, 2025.
