Orals: Fri, 2 May | Room 0.94/95
The ERC-AdG project Open SESAME (project No 101141362) aims to develop a time-evolving model for the entire solar atmosphere, including the chromosphere and transition region, based on a multifluid description. Currently, models are primarily steady, rely on a single-fluid description and include only the corona due to computational challenges. We plan to use time-evolving ion-neutral and ion-neutral-electron models. The multifluid approach will enable us to describe the intricate physics in the partially ionised chromosphere and quantify the transfer of momentum and energy between the atmospheric layers. The questions of where the solar wind originates and solar flares and coronal mass ejections are driven have fundamental scientific importance and substantial socio-economic impact. Indeed, the solar atmospheric model is the crucial missing link in the Sun-to-Earth model chain to predict the arrival and effects of CMEs on Earth.
This goal is now possible by combining our implicit numerical solver with a high-order flux-reconstruction (FR) method. The implicit solver avoids the numerical instabilities that lead to strict time-step limitations on explicit schemes. The high-order FR method enables high-fidelity simulations on very coarse grids, even in zones of high gradients. We started with this new development and will introduce three critical innovations. First, we will combine high-order FR with physics-based r-adaptive (moving) unstructured grids, redistributing grid points to regions with high gradients. Second, we will implement CPU-GPU algorithms for the new heterogeneous supercomputers advanced by HPC-Europa. Third, we will implement AI-generated magnetograms to make the model respond to the time-varying photospheric magnetic field, which is crucial for understanding important solar plasma properties and processes.
Thus, we will develop a first-in-its-kind high-order GPU-enabled 3D time-accurate solver for multifluid plasmas. If successful, we will implement the most advanced data-driven solar atmosphere model in an operational environment. The project started on 1 September 2024, and we already have interesting results on time-dependent corona modelling and high-order flux-reconstruction simulations.
How to cite: Poedts, S. and the Open SESAME: Open SESAME: status and further plans, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16188, https://doi.org/10.5194/egusphere-egu25-16188, 2025.
Combined with data assimilation methods, a three-dimensional magnetohydrodynamic (MHD) numerical model is an effective tool to explore the mechanism of space weather. As a driver of space weather, the dynamic development of stream interaction regions (SIRs) near the orbit of Mars is an area of active research. In this study, we use the interplanetary total variation diminishing (TVD) MHD model to simulate solar wind parameters and
model SIRs near Mars from 2021 November 15 to 2021 December 31. In this model, the MHD equations are solved by the conservation TVD Lax–Friedrichs scheme in a rotating spherical coordinate system with six component meshes used on the spherical shell. Solar wind velocity, density, temperature, and magnetic field strength are given at the inner boundary due to the characteristic waves propagating outward. We compared modeled results with observations from Mars Atmospheric Volatile EvolutioN (MAVEN) and Tianwen-1 (China’s first Mars exploration mission). Statistical analysis shows that the simulated results can capture SIRs and are in good agreement with observations; moreover, the assimilated results based on the Kalman filter improve the accuracy of numerical prediction compared with simulated results. This paper is the first attempt to simulate SIR events combined with MAVEN and Tianwen-1 in situ observations. Our work demonstrates that using the MHD model with the Kalman filter to reconstruct solar wind parameters can help us study the characteristics of SIRs near Mars, improve the capabilities of space weather forecasting, and understand the background solar wind environment.
How to cite: Shen, F., Zhang, H., Yang, Y., Chi, Y., Shen, C., and Tao, X.: Three-Dimensional Magnetohydrodynamic (MHD) Modeling of Solar Wind Near Mars by Combinng with data assimilation method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5598, https://doi.org/10.5194/egusphere-egu25-5598, 2025.
A series of numerical simulations of convective dynamo, with varying grid resolution, with or without explicit magnetic diffusivity and viscosity, are presented and analyzed. It is found that in the simulations, with the increase of Reynolds number, the magnitude of current helicity increases dramatically, whereas the variation of kinetic helicity is very moderate. The competition between the kinetic helicity term and the current helicity term of the alpha coefficient results in an interesting behavior of the large-scale magnetic fields that resembles the ``dynamo-disappear-and-recover" phenomena reported in Hotta et al. 2016 Science paper. Our simulation and analysis suggest that, the role of current helicity first functions to suppress the dynamo, as the convectional $\alpha$-quenching concept states, but then functions to drive the dynamo, instead of quenching it, after a critical Reynolds number is exceeded.
How to cite: Zhang, M. and Fan, Y.: The role of current helicity in driving solar dynamo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3046, https://doi.org/10.5194/egusphere-egu25-3046, 2025.
The magnetohydrodynamic model of the solar high-temperature atmosphere is an important plasma model, which can reproduce many important features in simulating solar coronal plasma and magnetic field processes. However, the assumption of the MHD model may fail during highly dynamic and transient events, such as magnetic reconnection, and plasma heating, and in partially ionised structures such as the chromosphere, sunspots, and coronal rain. Therefore, a two-fluid MHD model with ions and neutral components can simulate many new phenomena. This study considers the two- fluid effects of solar plasma, and investigates the modification to traditional MHD models by including neutral components. We simulated MHD waves, and loop top turbulences in partially ionised plasma in sunspots or chromospheric flows. We focus on the separation of ions and neutral components in energy transfer processes and the potential contribution of neutral components to the nascent solar wind. Our simulations show that two-fluid effects would contribute significantly to solar plasma heating by collisional friction, and lead to the leakage of neutral components across the magnetic field lines and escape to the corona, it completely revolutionised our understanding of the corona, in which the role of the neutral component was neglected.
How to cite: Yuan, D. and Kuzma, B.: Two-fluid magnetohydrodynamic effects in the high-temperature atmosphere of the sun and their new perspectives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2724, https://doi.org/10.5194/egusphere-egu25-2724, 2025.
We explored the origin of quasi-periodic pulsations (QPPs) in multiple wavelengths of a white-light flare, which occurred at the edge of a sunspot group. A short period at about 3 minutes is simultaneously observed in wavebands of HXR, microwave, and Lyα during the flare impulsive phase. The onset of flare QPPs is almost simultaneous with the start of magnetic cancellation between positive and negative fields, indicating that it is most likely triggered by accelerated electrons that are associated with periodic magnetic reconnections. A long period at about 8 minutes is only detected in the white-light emission, suggesting the presence of cutoff frequency. The similar periods of 3 and 8 minutes are measured at the umbra and penumbra in the adjacent sunspot. Moreover, the NLFFF extrapolation results suggest that the flare area and sunspots are connected by the magnetic field lines. Our observations support the scenario that the short-period QPP is modulated by the slow magnetoacoustic wave originating from the sunspot umbra, while the long-period QPP is probably modulated by the slow-mode magnetoacoustic gravity wave leaking from the sunspot penumbra.
How to cite: Li, D.: Exploring the origin of quasi-periodic pulsations during a white-light flare, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3997, https://doi.org/10.5194/egusphere-egu25-3997, 2025.
Solar flares, eruptive prominences (EPs), and coronal mass ejections (CMEs) significantly impact Earth's environment and human habitability, as they are different manifestations of solar storms. Sometimes, solar energetic particle events (SEPs) are associated with interplanetary shocks driven by CMEs that propagate through the turbulent solar wind. We investigate the physical mechanisms of these phenomena in a more realistic gravitationally stratified solar atmosphere using 2.5D magnetohydrodynamics (MHD) and particle simulations. Our research covers three main topics:
(1) MHD simulations of solar flux rope eruptions and prominence formation: Starting from the standard solar eruption model, we employed 2.5D MHD simulations to investigate two scenarios of flux rope and prominence eruptions within a more realistic, gravitationally stratified solar atmosphere. We developed an enhanced levitation model for prominence formation and proposed a novel mechanism involving plasmoid-fed processes in the current sheet. The former is driven by photospheric converging motions, while the latter focuses on the catastrophe model of flux rope eruption and emphasizes the crucial role of magnetic reconnection in prominence formation. These models describe the formation of flux ropes during eruption and pre-existing flux ropes beforehand, respectively. Additionally, we explored "mesoscale" phenomena during flux rope eruption and their association with Quasi-Periodic Pulsations (QPPs), reproducing multi-wavelength observational images.
(2) Shock-turbulence interactions in interplanetary space: Solar wind turbulence is ubiquitous, and when CMEs propagate through the solar wind, they drive interplanetary shocks that interact with solar wind turbulence, which is one of the sources of SEPs. These interactions result in a turbulent downstream fluid. We found that after shocks propagate across turbulence, the downstream occurrence of plasmoids (i.e., small magnetic flux ropes in the solar wind) increases, saturates to a peak value for a certain interval, and then gradually decreases away from the shock. This behavior is consistent with in-situ measurements taken by the Magnetospheric Multiscale (MMS) mission at Earth's bow shocks. These plasmoid structures are important for plasma heating and particle acceleration.
(3) Particle accelerations during solar eruptions: We investigated particle acceleration during solar eruptions, focusing on: 1) test-particle modeling of non-adiabatic motion of particles in 2D magnetic islands and 2) a combined Particle-In-Cell (PIC) and MHD approach (PIC-MHD) to study particle acceleration at interplanetary shocks. In the PIC-MHD approach, the background thermal plasma is treated as a magnetofluid, while the motion of non-thermal particles is influenced by the Lorentz force. This method accounts for electromagnetic interactions between non-thermal particles and the background magnetofluid, potentially leading to upstream self-excited turbulence that enhances particle acceleration through various mechanisms.
Overall, our research focuses on various processes in solar storms. Understanding and even predicting these phenomena are crucial for studying their impact on human habitability.
How to cite: Zhao, X.: CMEs and Interplanetary Shocks: 2.5D Numerical Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21910, https://doi.org/10.5194/egusphere-egu25-21910, 2025.
A flattop distribution is one of the most characteristic non-Maxwellian velocity distributions in space plasmas. It is often observed in collisionless shocks and reconnection sites in near-Earth space. In this contribution, we discuss a numerical approach to study a flattop plasma in particle-in-cell (PIC) simulations. Specifically, we propose two numerical methods for randomly generating flattop-distributed velocities: a piecewise rejection method and a transform method from a gamma-distributed random number. Their usability is briefly compared.
Gamma-distributed random numbers are useful for generating flattop and other distributions. However, random number generators (RNGs) for gamma distribution may not be always efficient. Here, we propose a novel RNG algorithm for gamma distribution with shape parameter less than unity, based on the generalized exponential distribution and the squeeze method [1]. Numerical tests show that the proposed method is one of the best two in this category.
[1] S. Zenitani, Economics Bulletin, 44, 1113-1122 (2024), arXiv:2411.01415
How to cite: Zenitani, S.: Random number generation in kinetic plasma simulation: flattop and gamma distributions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2192, https://doi.org/10.5194/egusphere-egu25-2192, 2025.
The solar wind is an accessible natural laboratory for investigating thermal and energetic particles in space plasmas. The particle dynamics in the solar wind has a highly multi-scale nature, covering 8 orders of magnitude of spatial scales, from the lengths characteristic of the electron gyromotion around magnetic field lines ( ~1 km) to those characteristic of particle transport from the Sun to the Earth ( ~ 1 au). Studying such dynamics is a difficult endeavour, especially due to the solar wind’s strongly turbulent nature. Current models of particle dynamics in turbulent plasmas suffer from one or more limitations, such as unrealistic plasma background (e.g., 2D modelling, lack of the correct statistical turbulent properties such as anisotropy and intermittency of structures) or limited accuracy (e.g., small computational grids, low resolution in phase space). Most importantly, they only employ one simulation at a time and thus they only model the turbulent energy cascade over three decades of scales at best.
We present our innovative solution to overcome all those limitations: the multi-scale Box-in-Box (BIB) approach. The first step is to model the turbulent energy cascade from very large to very small scales, using a portion of a large simulation as initial condition for another one with higher resolution and repeating this process multiple times in sequence while coupling different physical models, e.g., MHD at the largest scales, hybrid across the ion scales, and fully kinetic at electron ones. The second step is advancing test-particles trajectories using the turbulence simulations as an evolving background from small to large scales, starting from the fully kinetic simulation and then switching to the hybrid and finally to the MHD one as the energy (and thus the gyroradius) of the test particles increases. We will show and discuss the main technical challenges of this kind of approach, the required operations in the different steps of the procedure, and some successful results. Our innovative BIB approach makes it possible to model the large-scale propagation of energetic particles in the turbulent solar wind while retaining a realistic and self-consistent description of the microphysics responsible for particle energization. Our BIB simulations will be particularly useful for developing and testing new visualisation and analysis techniques for future multi-scale space missions such as HelioSwarm and Plasma Observatory.
How to cite: Franci, L., Papini, E., and Trotta, D.: Modelling the particle dynamics in turbulent plasmas using the innovative multi-scale Box-In-Box (BIB) approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19152, https://doi.org/10.5194/egusphere-egu25-19152, 2025.
We have used a particle-in-Cell (PIC) simulation combined with a global MHD simulation to investigate energy transport from reconnection in the magnetotail to the inner magnetosphere. Initially, we ran an MHD simulation driven by nominal solar wind parameters and southward IMF. After reconnection starts in the magnetotail, we loaded the PIC simulation with plasma based on the MHD parameters. The PIC simulation extended from the solar wind outside of the bow shock to beyond the reconnection region in the tail and was run for 1m 47s. During that time, particles from the reconnection region reached the inner magnetosphere. We evaluated the transport of energy by examining the ion and electron energy fluxes, the Poynting flux and the changes in the particle and electromagnetic power densities in the simulation box as functions of time. We evaluated the changes in the energy densities by examining the divergences of the ion and electron energy fluxes and the Poynting flux. The particles move earthward in narrow channels like bursty-bulk-flows (BBFs). The Poynting power density is smaller than the ion particle power density. The ion kinetic power density is larger than the thermal power density. The energy exchange between kinetic energy and thermal energy is determined by the off-diagonal terms in the pressure tensor.
How to cite: Walker, R. and Rusiatis, L.: A Simulation of Energy Exchange from Magnetotail Reconnection to the Inner Magnetosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5369, https://doi.org/10.5194/egusphere-egu25-5369, 2025.
Posters on site: Thu, 1 May, 16:15–18:00 | Hall X4
Ellerman bombs (EBs) and ultraviolet (UV) bursts are two of the smallest observed solar activities triggered by magnetic reconnection in the lower solar atmosphere, typically associated with flux emergence regions. Joint observations from the Interface Region Imaging Spectrograph (IRIS) satellite and ground-based solar telescopes reveal that approximately 20% of hot UV bursts are temporally and spatially connected with the cooler EBs. Using 3D radiation magnetohydrodynamic (RMHD) simulations with the MURaM code, we investigated the spontaneous emergence of a magnetic flux sheet, leading to complex magnetic field structures and diverse high-temperature activities due to magnetic reconnection. The simulations show that opposite-polarity magnetic fields converge in the lower solar atmosphere, forming thin current sheets and triggering plasmoid instability, which results in small twisted magnetic flux ropes and highly nonuniform plasma density and temperature. Hot plasmas (>20,000 K) emitting strong UV radiation coexist with cooler plasmas (<10,000 K) showing Hα wing emissions, with the former located ~700 km above the solar surface and the latter above them. Synthesized images and spectral line profiles exhibit characteristics of both EBs and UV bursts, demonstrating that turbulent reconnection mediated by plasmoid instability can occur in small-scale reconnection events in the partially ionized lower solar atmosphere. This model explains the formation mechanisms of UV bursts connected with EBs and indicates that UV bursts can form in atmospheric layers extending from the lower chromosphere to the transition region.
How to cite: Cheng, G.: Turbulent Reconnection in the Lower Solar Atmosphere Triggers UV Bursts Connecting with Ellerman Bombs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21916, https://doi.org/10.5194/egusphere-egu25-21916, 2025.
Modeling Solar magnetic field in the corona is very important to understand the solar eruption and heating mechanism. However, the direct measurements of solar magnetic field in the solar corona is still taking a great challenge not only in the high accurate measurements of solar polarization signal, but also in the inversion approach for the Optic-thin condition of corona atmosphere. Existence and uniqueness in the force-free/Non-force-free extrapolation in the solar corona is still unknown. Magnetic helicity, as a topological invariant, has become a key factor in exploring the generation of magnetic fields within the Sun, solar eruptions, and energy transfer processes in interplanetary. We firstly give a short review of modelling magnetic helicity in the solar corona from the observation to simulation. Then we introduce a new method by calculating the potential current in a magnetic-helicity-conservation-decomposed approach to derive the magnetic helicity/energy equivalence of three-dimension magnetic field only based on the photospheric vector magnetogram. We testify our method by using the given magnetic field of Low and Lou (1990) and the difference is very small. Even though, the Lorentz force caused from the calculated magnetic field well explained the strong shearing movements of polarity inversion line (PIL) in the newly emerging active region of NOAA11158. Finally, we apply our method to the observation data and it is also successfully found that the weak/strong loss ratio of magnetic helicity in the solar confined/eruptive solar events.
How to cite: Yang, S.: Modeling Solar Magnetic Field In The Solar Corona From The View Of Magnetic Helicity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14276, https://doi.org/10.5194/egusphere-egu25-14276, 2025.
We report an M9.3 flare and filaments activities from NOAA Active Region 11261 that are strongly modulated by the 3D magnetic skeleton. Magnetic field extrapolation from the vector magnetic field suggests complex magnetic connectivity and the existence of a high coronal null point southeast of the active region. A small filament over the inversed V-shaped polarity inversion line erupted and resulted in the M9.3 flare associated with a weak hot mass ejection, CME-like features, and the formation and activity of a relatively large filament. The ejection features and the eruption of the large filament were toward the southeast. Comparative analyses have disclosed the following new facts: (1) the trajectory of looptop hard X-ray emission provides solid evidence that the magnetic reconnection site propagated up toward the coronal null point as the flare and filaments erupted. (2) the EVU observations show coronal mass ejection-like eruption features in the ejection region of the magnetic skeleton. (3) the closed fan confined the west end of the large filament and the corresponding flare ribbons. We demonstrate a spatiotemporal relationship between the magnetic skeleton and the flare filament activity. We conclude that the magnetic skeleton can modulate and determine almost all the characteristics of the studied activity in the corresponding scale.
How to cite: Guo, J.: The Role of Magnetic Skeleton in Solar Flare Filaments Activities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16745, https://doi.org/10.5194/egusphere-egu25-16745, 2025.
Understanding solar eruptive phenomena requires accurate information about the coronal magnetic field. However, due to current technological limitations, direct measurement of the coronal magnetic field in three dimensions remains nearly impossible. Consequently, it is often approximated as a force-free field (FFF) using vector magnetogram data, which provide the three components of the magnetic field on the two-dimensional photospheric surface as boundary conditions.
Previously, we introduced a novel method for reconstructing coronal magnetic fields based on the poloidal-toroidal (PT) representation, which led to the development of the NFPT (Nonvariational Force-Free Field Code in Poloidal-Toroidal Formulation) in Cartesian coordinates. However, this approach did not account for the spherical geometry of the Sun's surface.
In this study, we present an improved FFF code that operates in spherical coordinates, incorporating the PT representation. This approach facilitates straightforward implementation of photospheric boundary conditions, with vector magnetogram data used as input. In our code, the source-surface top boundary is set at 2.5 solar radii, where the source surface region is believed to exist. The new code has been validated against analytic models by Low and Lou (1990) and compared with other FFF codes. This spherical-coordinate-based code aims to improve the accuracy of magnetic field information in an equilibrium state, thereby bringing qualitative enhancements to the initial conditions for global heliospheric modeling.
How to cite: Yi, S., Choe, G.-S., Kim, S., and Lee, M.: A Novel Poloidal-Toroidal Approach for Spherical Force-Free Field Reconstruction of Coronal Magnetic Fields, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3962, https://doi.org/10.5194/egusphere-egu25-3962, 2025.
Coherent radio emission mechanism of solar radio bursts is one of the most complicated and controversial topics in the solar physics. To clarify mechanism of different types of solar radio bursts, (radio) wave excitation by energetic electrons in homogeneous plasmas has been widely studied via particle-in-cell (PIC) code numerical simulations. In this study, we, however, investigate effects of inhomogeneity in plasmas of the solar coronal on wave excitation by ring-beam distributed energetic electrons utilizing 2.5-dimensional PIC simulations. Disequilibrium introduced by the inhomogeneous magnetic field is balanced by either inhomogeneous density or inhomogeneous temperature of the background plasma. Both the beam and electron cyclotron maser (ECM) instabilities could be triggered with the presence of the energetic ring-beam electrons. Onset of the ECM instability is, however, later than the beam instability to excite waves in this study. The resultant spectrum of the excited electromagnetic waves presents a zebra-stripe pattern in the frequency space. The inhomogeneous density or temperature in plasmas would, however, influence the frequency bandwidth, excitation location of these excited waves. This study will, hence, help diagnose the plasma properties at the generation sites of solar radio bursts. Applications of this study to solar radio bursts (e.g., solar type V, zebra-pattern radio burst) will be discussed.
How to cite: Zhou, X., Munoz, P., Benacek, J., Zhang, L., Wu, D., Chen, L., Ning, Z., and Buechner, J.: Coherent Wave Excitation by Energetic Ring-beam Electrons in Inhomogeneous Solar Corona, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6157, https://doi.org/10.5194/egusphere-egu25-6157, 2025.
Magnetohydrodynamic (MHD) waves interact with the solar magnetic structures and have the potential to heat solar plasma and be used as a tool for plasma diagnostics. Despite extensive research, the precise mechanisms by which waves contribute to energy transport and dissipation remain incompletely understood. Additionally, utilizing wave characteristics for accurate diagnostics of the coronal plasma structure presents a significant challenge. Here, we utilize the Goode Solar Telescope to demonstrate transverse oscillations of the dark fibrils within the umbra of a sunspot and investigate their role in plasma heating. Additionally, we use EUV observations to show a quasi-periodic fast-mode MHD wave passing through a coronal hole could serve as a tool for plasma diagnostics. Our study finds that transverse oscillations are prevalent in the umbra of sunspots and carry a wave energy flux that significantly exceeds the loss rate of the solar active regions. Furthermore, the discovery of the MHD wave lensing effect provides a new mechanism for coronal hole diagnostics, with potential application to polar regions. These findings confirm the crucial role of MHD waves in coronal heating and demonstrate their potential as diagnostic tools for coronal plasma parameters. The studies provide new perspectives for understanding the multi-scale energy conversion and wave-magnetic field interactions in the solar atmosphere.
How to cite: Fu, L., Yuan, D., Kuźma, B., and Shen, Y.: Magnetohydrodynamic wave as a tool for solar plasma diagnostics and heating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3036, https://doi.org/10.5194/egusphere-egu25-3036, 2025.
The standard flare model is in generally depicted and studied in 2D simulations with an anti-symmetrical magnetic field configuration, symmetrical in magnitude, either side of the polarity inversion line. However, flare observations confirm that most flare have a significantly asymmetrical values of the magnetic field strength.
Here we present the first multi-dimensional magnetohydrodynamic flare simulation featuring evaporation driven by energetic electron beams in an asymmetrical magnetic field configuration. The simulation conditions that we use are known to rely significantly on those beams of electrons to drive the evaporated plasma upwards from the lower atmosphere (Druett et al. 2023). We study the impact of an asymmetrical configuration on the evolution and geometry of the flare-loop system as well as the impacts on the beam-driven evaporation using the MPI-AMRVAC model.
This results in multiple Hard X-Rays deposition sites in the lower atmosphere, Hard X-Rays sources forming at the top of the flare loop, and a sustained rotating flux rope structure with associated footpoint electron deposition flux.
How to cite: Dubart, M., Druett, M., and Keppens, R.: Beam-driven evaporation in 2.5D flare simulations with an asymmetric magnetic field configuration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8769, https://doi.org/10.5194/egusphere-egu25-8769, 2025.
In collisionless plasmas such as the solar wind, the particle velocity distributions can be shaped by various wave-particle interactions, which lead to effective energy transfer between electromagnetic fields and particles. The commonly-observed quasi-monochromic waves by in-situ satellites are widely believed to be generated by plasma instabilities via wave-particle interactions. Thus, how to quantify the role(s) of wave-particle interactions in plasma instabilities is a fundamental problem in the space plasma community. Recently, we developed a theoretical method quantifying both resonant and nonresonant wave-particle interactions, and we performed the comprehensive analyses on ion temperature anisotropy instabilities in the solar wind. This report will introduce new findings.
How to cite: Zhao, J.: Quantifying wave-particle interactions in ion temperature anisotropy instabilities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13988, https://doi.org/10.5194/egusphere-egu25-13988, 2025.
Ion cyclotron waves (ICWs) are prevalent in the near-Sun solar wind and play a significant role in the nonadiabatic heating of plasma. Recent observations from the Parker Solar Probe (PSP) have revealed the simultaneous presence of anti-sunward and sunward ICWs in the vicinity of the Alfvén surface. However, single-satellite observations cannot effectively trace the generation and evolution of these observed waves. To address this limitation, we employ kinetic-hybrid simulations to replicate the generation and evolution of counter-propagating ICWs under typical plasma conditions in the near-Sun solar wind. Following the linear growth phase, the simulated waves exhibit amplitude and polarization characteristics that closely match the observations. Additionally, our simulation illustrates proton scattering and helium heating induced by the counter-propagating waves. These results underscore the significance of locally generated ICWs in influencing solar wind ion dynamics.
How to cite: Wu, Y., Shi, C., Zhao, J., and Tao, X.: Kinetic-Hybrid Simulations of Counter-Propagating Ion Cyclotron Waves and Proton Scattering in the Near-Sun Solar Wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4616, https://doi.org/10.5194/egusphere-egu25-4616, 2025.
Discoveries by Parker Solar Probe (PSP) highlight the significance of nonthermal distributions in triggering ion-scale instabilities (Verniero et al. 2020, 2022; An et al. 2024; Liu et al. 2024). In this study, we show how the electron nonthermal (kappa) distribution could change the onset threshold of the ion-acoustic instability (IAI) recently observed by PSP (Mozer et al. 2021, 2023; Kellogg et al. 2024) between 15 and 25 solar radii and modeled by Afify et al. (2024). We perform analytical studies and kinetic simulations using the Vlasov-Poisson code with a parameter regime relevant to PSP observations. A setup of kappa-distributed electrons and two counterstreaming Maxwellian ion distributions (a core and a beam) is shown to be unstable w.r.t. the IAI, however, the electron-to-core and beam-to-core temperature ratios are slightly different from those recorded by PSP. The simulated growth rates have been validated by the kinetic theory. In the saturation regime, we do observe the formation of ion holes in the beam phase-space density. With large kappa values, the ion-acoustic waves interacted substantially with the beam, for instance, κ = 20, and shifted away from the beam with lower kappa values, for instance, κ = 5 and 7. Our findings confirm that protons exhibit reduced resonance in the presence of kappa electrons, and the electron heating observed by PSP during the presence of IAI is not replicated in our simulation (Mozer et al. 2022).
References
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How to cite: Afify, M. S., Dreher, J., O'Neill, S., and Innocenti, M. E.: The role of nonthermal electron distribution in triggering electrostatic ion-acoustic instability near the Sun, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2097, https://doi.org/10.5194/egusphere-egu25-2097, 2025.
We present a new free and open source (FOSS) simulation platform under development at the Finnish Meteorological Institute. Building on top of our existing space weather models for Earth, Mercury and other planets, the aim is to enable efficient global simulations of plasma interactions in the solar system and beyond, including unmagnetized and magnetized planetary bodies with and without atmospheres and ionospheres. Our development focuses on a flexible combination of magnetohydrodynamic (MHD), hybrid particle-in-cell (PIC) and full-kinetic methods. Fast time to solution is achieved via runtime adaptive mesh refinement (AMR), temporal substepping and massively parallel implementation using the message passing interface (MPI) and open multi-processing (OpenMP). We describe our approaches to combining different physical solutions within the same simulated volume and combining AMR with substepping. We verify the implementation against a plethora of test cases in one, two and three dimensions, and also discuss initial results from simulations of Mercury and BepiColombo flybys using particle and MHD approaches and highlight the largest differences.
How to cite: Honkonen, I., Jarvinen, R., and Phillips, D.: Platform of adaptive algorithms for global simulations of planetary space weather, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1388, https://doi.org/10.5194/egusphere-egu25-1388, 2025.
We present analyses of plasma wave modes in our global hybrid particle-in-cell simulation code, RHybrid, for flowing planetary plasma interactions. The model treats ions as macroscopic particle clouds moving under the Lorentz force while electrons are a charge-neutralising, massless fluid. Magnetic field is advanced by Faraday's law and coupled self-consistently with ion dynamics (ion charge density and ion electric current density) via non-radiative Maxwell's equations. We describe analyses of several test cases, like random initial conditions and backstreaming suprathermal populations, compared against known solutions, observations and previous results from local and global modeling, including Mercury-type solar wind and interplanetary magnetic field conditions. The results show dispersion relations, parameter correlations, polarisations and more. We discuss the accuracy of modelling of theoretical results, including properties of whistler, Alfvén and magnetosonic waves, and ion-ion streaming instabilities in RHybrid. With this work, we prepare for further development of the Finnish Meteorological Institute's free and open source space weather particle simulation platforms, and for the interpretation of upcoming observations from the BepiColombo mission.
How to cite: Phillips, D., Jarvinen, R., Honkonen, I., and Kallio, E.: Plasma waves in a global ion-kinetic hybrid simulation for Mercury's space weather, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1415, https://doi.org/10.5194/egusphere-egu25-1415, 2025.
Interplanetary shocks (IPs) are ubiquitous in the Heliosphere, and are particularly relevant when associated to Stream Interaction Regions and Coronal Mass Ejections due to their great geomagnetic effectiveness on Earth. As their evolution and propagation may vary based on the different interplanetary conditions, it is crucial to study the shocks characteristics under different scenarios to gain a better understanding of the different types of interactions with the near-Earth environment.
In this work, we propose a systematic analysis of the evolution, propagation and characterization of self-consistently generated interplanetary shocks under different conditions, such as different interplanetary magnetic field intensity, direction and particles density, velocity, by means of hybrid computer simulations (fluid electrons, kinetic ions). The use of a hybrid formalism allows us to simulate large domains necessary for the shocks to form and evolve, by still retaining the kinetic information, which is fundamental to consider important kinetic effects, e.g., in supercritical shock-fronts.
In particular, upon setting up an initial steepening velocity profile between slower and faster velocities, we observe this profile to evolve in a two boundaries-structure, separated by a turbulent sheath. We first qualify these boundaries relative to the structure expected from steady shocks, we estimate their respective velocity and their compression factor. We also analyse the main characteristics of the turbulent sheath, which propages at an intermediate velocity with a enhanced magnetic field and transverse components in the magnetic field and velocity. All these features are consistent with observations of SIRs at 1 AU (e.g., Jian+, 2006). Moreover, we also discuss the effects of different IMF orientations on the shock dynamics, as the different kinetic effects between a quasi-perpendicular and quasi-parallel configuration at the shock can bring to significant differences in the shock-front propagation and the related donwstream sheath turbulence.
How to cite: Cazzola, E., Fontaine, D., and Savoini, P.: Self-consistently generated, evolving and propagating interplanetary shocks with 3D hybrid simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6853, https://doi.org/10.5194/egusphere-egu25-6853, 2025.
The next generation of numerical plasma models need to have the capacity to address multi-scale problems for which fluid-only codes miss physics and pure kinetic codes are too computationally heavy. The code PHARE, currently being developed, aims at enabling the evolution of complex plasma systems over a dynamic hierarchy of grids with different mesh resolutions and potentially different plasma formalisms as well. This Adaptive Mesh and Model Refinement (AM2R) will provide better resolution and better realism to the solution where and when assessed necessary. This work will present the ongoing progress on the project, regarding the AMR Hybrid-PIC and AMR Hall-MHD solvers.
How to cite: Caromel, U., Aunai, N., Smets, R., and Deegan, P.: Adaptive mesh and model refinement for numerical plasma models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11264, https://doi.org/10.5194/egusphere-egu25-11264, 2025.
Rotational discontinuities (RDs) are considered in magnetohydrodynamics (MHD) as a kind of stable, persistent structure. As recent observations have shown, RDs may effectively describe the boundaries of switchbacks in the solar wind, around / inside which the plasma is highly dynamic and with phase space density variations. Because of the low collisionality of the solar wind, it may be worthwhile to revisit RDs with a kinetic approach. We therefore model the the plasma in RDs representing switchbacks with the state-of-the-art full-particle simulation code ECSim, and discuss the kinetic effects occurring in RD plasmas, including proton heating, anisotropy alternation, and modification of a core-beam composition, as well as the potential implications for the nature of switchbacks.
How to cite: Lin, R., Bacchini, F., and He, J.: Kinetic Effects of Rotational Discontinuities on Maxwellian and Non-Maxwellian plasmas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13772, https://doi.org/10.5194/egusphere-egu25-13772, 2025.
Posters virtual: Thu, 1 May, 14:00–15:45 | vPoster spot 3
EGU25-8215 | Posters virtual | VPS27
Plasma Mechanisms Behind Hammerhead Proton Populations Observed by Parker Solar ProbeThu, 01 May, 14:00–15:45 (CEST) | vP3.15
The Parker Solar Probe (PSP) has provided unprecedented detailed in-situ measurements of proton velocity distributions (VDs) in the young solar wind, unveiling striking hammerhead features. The first interpretations and analyses, including PIC simulations of these unexpected shapes, suggested the involvement of more complex processes, especially kinetic instabilities. Recently, in A&A, 692, L6 (2024), we have identified a self-generated instability triggered by proton beams, whose back-reaction on the proton VDs can form the hammerhead proton population. An effective and numerically less-expensive quasi-linear approach enabled us to explore how this plasma micro-instability reshapes proton distribution, reducing beam drift and inducing a strong perpendicular temperature anisotropy, the main feature of the hammerhead structure. Our results align with PSP's in situ data and provide a fresh perspective on these distributions' dynamic and transient nature. These findings offer new insights into the role of kinetic instabilities in shaping space plasma dynamics.
How to cite: Shaaban, S. M., Lazar, M., López, R. A., Yoon, P. H., and Poedts, S.: Plasma Mechanisms Behind Hammerhead Proton Populations Observed by Parker Solar Probe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8215, https://doi.org/10.5194/egusphere-egu25-8215, 2025.
