NP6.5 | Turbulence, magnetic reconnection, shocks and particle acceleration: nonlinear processes in space, laboratory and astrophysical plasmas
EDI
Turbulence, magnetic reconnection, shocks and particle acceleration: nonlinear processes in space, laboratory and astrophysical plasmas
Convener: Francesco Pucci | Co-conveners: Maria Elena Innocenti, Giovanni Lapenta, Meng Zhou, Naïs Fargette
Orals
| Wed, 17 Apr, 10:45–12:30 (CEST)
 
Room 0.96/97
Posters on site
| Attendance Mon, 15 Apr, 10:45–12:30 (CEST) | Display Mon, 15 Apr, 08:30–12:30
 
Hall X4
Orals |
Wed, 10:45
Posters on site
Mon, 10:45
This session focuses on the non-linear processes in space, laboratory, and astrophysical plasma. In many cases, these processes are not separated but appear interlinked. For instance, magnetic reconnection is an established ingredient of the turbulence cascade, and it is also responsible for the production of turbulence in reconnection outflows; shocks can be accountable for turbulence formation, for example, in the turbulent magnetosheath, or can be efficient particle accelerators through their interaction with the ambient turbulence. All these and other non-linear processes shape plasma dynamics in the environments where they occur and govern the energy transfer between the electromagnetic field and the particles.

The study of these processes has seen significant progress in recent years thanks to a synergistic approach based on simulations and observations. On the one hand, simulations can deliver output in a temporal and spatial range of scales going from fluid to electron kinetic. That is also due to the advent of GPU facilities that contribute to increasing computational algorithms' power in plasma physics. On the observational side, high cadence measurements of particles and fields and high-resolution 3D measurements of particle distribution functions are currently provided by the missions MMS, Parker Solar Probe, and Solar Orbiter, opening new research scenarios in heliophysics and providing a consistent amount of new data to be analyzed. Furthermore, other present and future missions that will give unique plasma measurements around solar system compact objects such as Bepi Colombo, Juice, and Comet Interceptor, or multi-point measurements in the solar wind such as Helioswarm are demanding the development of new numerical tools for a successful interpretation of the observations.

This session welcomes simulation, observational, and theoretical works relevant to studying the abovementioned processes. Particularly welcome this year will be works focusing on how non-linear processes are responsible for the energy transfer between fields and species and energy partition among species. We also encourage papers proposing new methods in simulation techniques and data analysis, for example, those rooted in Artificial Intelligence and GPU algorithms or those based on multi-point satellite observations.

Session assets

Session materials

Orals: Wed, 17 Apr | Room 0.96/97

Chairpersons: Maria Elena Innocenti, Naïs Fargette, Francesco Pucci
10:45–10:50
5-minute convener introduction
10:50–11:00
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EGU24-1998
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ECS
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Virtual presentation
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On-disk Observation of Bidirectionally Propagating Plasma Blobs Near the Reconnection Site of a Solar Eruption 
Zhenyong Hou, Hui Tian, Maria Madjarska, Hechao Chen, Tanmoy Samanta, Xianyong Bai, Zhentong Li, Yang Su, Wei Chen, and Yuanyong Deng

Current sheet is a commonly observed structure involved in solar eruptions. However, the physical properties of its fine structures during a solar eruption are rarely investigated. Here, we report an on-disk observation that displays 139 compact, circular or elliptic bright structures, presumably plasma blobs, propagating bidirectionally along a plasma sheet during a period of about 24 minutes around the peak time of an eruptive flare. From extreme ultraviolet images, we distinguish a plasma sheet connecting the flare loops and the erupting filament. The average width, duration, and projected velocities of these blobs are about 1.7±0.5 Mm, 73±54 s, and 190±81 km/s, respectively. The reconnection site rises with an average velocity of about 51 km/s. We have obtained the temporal variation of the blob number during the solar eruption, which is similar to that of the GOES X-ray flux. The observational results suggest that plasmoid instability plays an important role in the energy release process of solar eruptions.

How to cite: Hou, Z., Tian, H., Madjarska, M., Chen, H., Samanta, T., Bai, X., Li, Z., Su, Y., Chen, W., and Deng, Y.: On-disk Observation of Bidirectionally Propagating Plasma Blobs Near the Reconnection Site of a Solar Eruption, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1998, https://doi.org/10.5194/egusphere-egu24-1998, 2024.

Discussion Post a comment
11:00–11:10
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EGU24-11551
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ECS
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On-site presentation
A machine learning approach to structure and energy in magnetic reconnection 
Cara Waters, Jonathan Eastwood, Naïs Fargette, Martin Goldman, David Newman, and Giovanni Lapenta

Magnetic reconnection is a fundamentally important process in space plasmas due to the release and repartition of the magnetic energy stored within the reconnecting field. As this energy transfer significantly impacts magnetospheric dynamics, understanding the partition of this energy and how this varies across the reconnection site can provide further insight into other magnetospheric processes. Although in situ spacecraft data provide direct measurements of relevant plasma properties, it can be difficult to establish the location of spacecraft relative to the reconnection site. This frustrates efforts to evaluate the way in which energy fluxes change with distance from the central reconnection X-line. Under certain circumstances, reconstruction techniques can be used to estimate the spacecraft trajectory through individual events, but these may rely on simplifying assumptions limiting their use.

This motivates new approaches to determining where a spacecraft is relative to the reconnection structure. By utilising forefront machine learning techniques, we can more accurately study individual regions associated with the reconnection process and thus understand how they individually contribute to repartitioning the overall energy budget. In this context, we present these new applications of machine learning techniques to identify the regions in both simulation and spacecraft data.

Firstly, we present the results of a robust method which utilises k-means clustering to identify different regions encountered within the overall reconnection X-line structure. This uses plasma fluid and field variables output by a 2.5-D PIC simulation with a geometry comparable to that of reconnection in Earth’s magnetotail. We then translate this model for use in spacecraft data by implementing an approach based on a recurrent neural network to account for the temporal context of the observations. We demonstrate the use of this model on MMS observations of reconnection in the Earth’s magnetotail, examining the properties of the plasma energy flux in different regions. We conclude by discussing how this approach may find use in other contexts where reconnection is observed in space plasmas.

How to cite: Waters, C., Eastwood, J., Fargette, N., Goldman, M., Newman, D., and Lapenta, G.: A machine learning approach to structure and energy in magnetic reconnection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11551, https://doi.org/10.5194/egusphere-egu24-11551, 2024.

11:10–11:20
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EGU24-2431
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ECS
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On-site presentation
The Current Tension Electric Field in the Generalized Ohm's Law 
Lei Luo, Xiaojun Xu, Liangjin Song, Meng Zhou, Zilu Zhou, Hengyan Man, Xing Wang, Yu Zhang, Peishan He, Siqi Yi, and Hui Li

Magnetic reconnection is a fundamental physical process which allows for the explosive release of magnetic energy into thermal and kinetic energy. It underlies many dynamics phenomena in the universe, including solar eruptions, geomagnetic substorms and tokamak disruptions. In collisionless plasma, the generalized Ohm's law (GOL) introduces collisionless effects which break the frozen-in constraint and enable reconnection to occur. The term, $-(m_e/e)[(\bm{J}/en)\cdot \nabla](\bm{J}/en)$, which is one of the electron inertia terms of GOL, is referred to as the current tension electric field ($\bm{E}_{CT}$) by us due to its mathematical resemblance to magnetic tension. In many classic textbooks and review papers, $\bm{E}_{CT}$ is considered as a small quantity and thus is ignored. In this study, we present solid evidence from both theoretical studies and particle-in-cell (PIC) simulations to demonstrate that $\bm{E}_{CT}$ dominates the electron inertia terms and plays important roles in providing reconnection electric field and energy dissipation in reconnection. Therefore, it should not be ignored. Based on our results, many classic textbooks in which $\bm{E}_{CT}$ has been ignored must be modified.

How to cite: Luo, L., Xu, X., Song, L., Zhou, M., Zhou, Z., Man, H., Wang, X., Zhang, Y., He, P., Yi, S., and Li, H.: The Current Tension Electric Field in the Generalized Ohm's Law, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2431, https://doi.org/10.5194/egusphere-egu24-2431, 2024.

11:20–11:30
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EGU24-10613
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ECS
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Highlight
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On-site presentation
Direct Measurements of Field-Particle Energy Exchange and Anomalous Effects Associated with Electromagnetic Turbulence in Electron Diffusion Region of Collisionless Magnetic Reconnection 
Zhihong Zhong, Meng Zhou, Daniel Graham, Yuri Khotyaintsev, Ye Pang, Rongxin Tang, and Xiaohua Deng

Magnetic reconnection and turbulence are two fundamental cross-scale processes in collisionless plasmas. Whether kinetic-scale electromagnetic (EM) turbulence can drive and support fast collisionless reconnection is an open and controversial question. In this work, we directly estimated the net field-particle energy exchange and anomalous electric fields associated with EM turbulence within the electron diffusion region, where the magnetic field lines were broken and reconnected. The results confirmed that these anomalous electric fields are mainly contributed by anomalous viscosity term. The maximum contribution of anomalous effects can be up to about 20% of the fast reconnection electric field, while that in most events is less than 5%. Furthermore, the locally generated EM turbulence is inclined to support the fast reconnection, while the locally damping EM turbulence could backfire on the fast reconnection.

How to cite: Zhong, Z., Zhou, M., Graham, D., Khotyaintsev, Y., Pang, Y., Tang, R., and Deng, X.: Direct Measurements of Field-Particle Energy Exchange and Anomalous Effects Associated with Electromagnetic Turbulence in Electron Diffusion Region of Collisionless Magnetic Reconnection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10613, https://doi.org/10.5194/egusphere-egu24-10613, 2024.

11:30–11:40
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EGU24-13478
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Highlight
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On-site presentation
Assessing the Role of Turbulence-Driven Magnetic Reconnection in the Dissipation of Plasma Turbulence in Earth’s Magnetosheath 
Julia E. Stawarz, Paulina Quijia Pilapaña, Prayash S. Pyakurel, Naoki Bessho, Imogen L. Gingell, Tai Phan, Michael A. Shay, Harry C. Lewis, Christopher T. Russell, and Olivier Le Contel

Magnetic reconnection has long been thought to play an important role in turbulent plasmas – with the nonlinear dynamics of turbulent systems being well known to self-consistently generate intense current structures and associated magnetic shears that can be sites where so-called turbulence-driven magnetic reconnection can occur. However, complex three-dimensional magnetic topologies and the small-scale nature of these magnetic reconnection events have traditionally made it challenging to assess the role of magnetic reconnection in the turbulent dynamics from either a numerical or observational perspective. Recent high-resolution observations from NASA’s Magnetospheric Multiscale (MMS) mission have provided an unprecedented new opportunity to systematically examine turbulence-driven reconnection in the region of shock-driven turbulence within Earth’s magnetosheath. These observations have provided new insight into the nature of magnetic reconnection within turbulent plasmas, revealing that under the right conditions so-called electron-only magnetic reconnection, in which ion jets are not accelerated by the newly reconnected magnetic fields, can occur. In this talk, we explore how to observationally constrain the contribution turbulence-driven magnetic reconnection makes to the energy dissipation rate of the turbulence. We then directly compare estimates of the dissipation rate associated with reconnection events observed by MMS to estimates of the turbulent energy cascade rate for the specific intervals of magnetosheath turbulence that the reconnection events are observe within. The potential implications of traditional ion-coupled reconnection versus electron-only reconnection for the energy budget of turbulent dissipation and the magnetosheath overall are then discussed in detail.

How to cite: Stawarz, J. E., Quijia Pilapaña, P., Pyakurel, P. S., Bessho, N., Gingell, I. L., Phan, T., Shay, M. A., Lewis, H. C., Russell, C. T., and Le Contel, O.: Assessing the Role of Turbulence-Driven Magnetic Reconnection in the Dissipation of Plasma Turbulence in Earth’s Magnetosheath, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13478, https://doi.org/10.5194/egusphere-egu24-13478, 2024.

11:40–11:50
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EGU24-10581
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On-site presentation
Topology of turbulence within collisionless plasma reconnection 
Bogdan Hnat, Sandra Chapman, and Nick Watkins

Magnetospheric Multi Scale four-point satellite observations are used to characterize the magnetic field line topology within a single reconnection current layer. We examine magnetopause reconnection where the spacecraft encounter the Electron Diffusion Region (EDR). We find fluctuating magnetic field with topology identical to that found for dynamically evolving vortices in hydrodynamic turbulence. The turbulence is supported by an electron-magnetohydrodynamic (EMHD) flow in which the magnetic field is effectively frozen into the electron fluid. Accelerated electrons are found in the EDR edge where we identify a departure from this turbulent topology, towards two-dimensional sheet-like structures. This is consistent with a scenario in which sub-ion scale turbulence can suppress electron acceleration within the EDR which would otherwise be possible in the electric field at the X-line.

How to cite: Hnat, B., Chapman, S., and Watkins, N.: Topology of turbulence within collisionless plasma reconnection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10581, https://doi.org/10.5194/egusphere-egu24-10581, 2024.

11:50–12:00
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EGU24-11563
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On-site presentation
Turbulent dissipation in 1D and 3D simulations of thin solar wind flux tube    
Victor Réville

Turbulence is likely to be the main source of heating of the solar corona and solar wind. The turbulent cascade transfers energy from large scale motions down to ion and electron scales, where the plasma is heated. Self-consistent simulations of the turbulent solar wind heating are however very hard to achieve as the cascade spans many scales and physical, fluid and kinetic, processes. In this talk, we focus on the inertial range of the cascade, which may be modeled with MHD. Using a 1D profile along a solar wind flux tube, we show that we can power a solar wind solution through a compressible cascade triggered by a non-linear parametric instability. The dissipation process of this simulation is, however, unlikely to be similar to 3D realistic configurations. Hence, we compare this simulation with an extremely high resolution 3D simulation of a thin flux tube, allowed by the new GPU accelerated MHD code Idefix. We compare the Politano-Pouquet law in its classical and weak formulation to assess the means of the dissipation in both simulations.

How to cite: Réville, V.: Turbulent dissipation in 1D and 3D simulations of thin solar wind flux tube   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11563, https://doi.org/10.5194/egusphere-egu24-11563, 2024.

12:00–12:10
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EGU24-15125
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ECS
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On-site presentation
Influence of Intermittency on the Energy Transfer Rate of Solar Wind Turbulence 
Honghong Wu, Shiyong Huang, Xin Wang, Liping Yang, and Zhigang Yuan

The intermittency in the solar wind turbulence influences the anisotropy of the spectral index and the scaling of multiorder structure functions. However, its influence on the energy transfer rate remains unclear. Here we identify the intermittency using the partial variance of increments method for the magnetic field data measured in the fast solar wind by the Ulysses spacecraft. We study the anisotropy by distinguishing the sampling direction using the angle θRB between the local magnetic field and radial direction. We analyze the multiorder structure function analyses  and describe the role of intermittency in the framework of log-Poisson cascade model. We find the isotropic scaling with a complete removal of intermittency. We compare explicitly the anisotropy of the energy transfer rate before and after removing the intermittency for the first time. We find a distinct anisotropy with a cascade enhancement in the direction perpendicular to the local magnetic field. The removal of the intermittency greatly weakens the anisotropy by mainly reducing the perpendicular energy transfer rate. Our findings suggest that the intermittency effectively enhances the energy transfer rate, in particular in the perpendicular direction in the solar wind turbulence.

How to cite: Wu, H., Huang, S., Wang, X., Yang, L., and Yuan, Z.: Influence of Intermittency on the Energy Transfer Rate of Solar Wind Turbulence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15125, https://doi.org/10.5194/egusphere-egu24-15125, 2024.

12:10–12:20
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EGU24-11788
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ECS
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solicited
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Highlight
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On-site presentation
Material Barriers to the Diffusion of Magnetic Field Lines 
Alex Pablo Encinas Bartos, Balint Kaszás, Sergio Servidio, and George Haller

Recent work has identified objective (frame-indifferent) material barriers that inhibit the flux of dynamically active vectorial quantities (i.e. linear momentum, angular momentum and vorticity) in Navier-Stokes flows. In the context of magnetohydrodynamics (MHD) the magnetic field vector is directly coupled to the evolution of the velocity field through the Lorentz force and therefore qualifies as a dynamically active vector field. In this work, we identify active Eulerian and Lagrangian barriers that block the diffusion of magnetic field lines in two-dimensional (2D) and three-dimensional (3D) MHD turbulence. These distinguished material surfaces provide physics-based and frame-indifferent active magnetic coherent structures that locally divide the space into two regions with minimal diffusion of magnetic field lines. In 2D, these barriers are directly connected to the electric current density. We propose an algorithm for the automated identification of such barriers from 2D and 3D numerical data of MHD turbulence simulations.

How to cite: Encinas Bartos, A. P., Kaszás, B., Servidio, S., and Haller, G.: Material Barriers to the Diffusion of Magnetic Field Lines, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11788, https://doi.org/10.5194/egusphere-egu24-11788, 2024.

12:20–12:30
Discussion

Posters on site: Mon, 15 Apr, 10:45–12:30 | Hall X4

Display time: Mon, 15 Apr 08:30–Mon, 15 Apr 12:30
Chairpersons: Naïs Fargette, Maria Elena Innocenti, Francesco Pucci
X4.35
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EGU24-924
Energy Conversion and Transport in Dayside Electron Diffusion Regions. 
Naïs Fargette, Jonathan Eastwood, Cara Waters, David Newman, Martin Goldman, and Giovanni Lapenta

The electron diffusion region (EDR) is believed to be a key region for the conversion of energy associated with magnetic reconnection from magnetic to kinetic and thermal, but the nature of energy transport and conversion in EDRs is still not well understood. In this work, we capitalise on recent studies that have increased the number of referenced EDRs observed by MMS and perform a statistical study of 80 near X-line events previously identified in the literature. Upon detailed analysis, MMS was found to be located within the inner EDR for 45 of these events, while others correspond to outer EDR or IDR crossings.
We investigate energy partition in their vicinity and find that the electron enthalpy flux dominates within the EDRs compared to the bulk kinetic and heat fluxes. We then evaluate the stationary terms of the energy conservation equation and find that large fluctuations of the electron enthalpy flux divergence tend to occur in the EDRs, suggestive of a complex energy transfer process dominated by the internal energy flux contribution. We also examine the possible role of magnetic shear/guide field, but this is somewhat limited by the fact that many events occur at relatively high shear and low guide field conditions. We conclude with considering how in future work, comparing these results to magnetotail- (symmetric) and magnetosheath- (low shear) EDR may bring further insight into how the regime in which magnetic reconnection occurs can impact the energy conversion and transport.

How to cite: Fargette, N., Eastwood, J., Waters, C., Newman, D., Goldman, M., and Lapenta, G.: Energy Conversion and Transport in Dayside Electron Diffusion Regions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-924, https://doi.org/10.5194/egusphere-egu24-924, 2024.

X4.36
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EGU24-2727
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ECS
Quantitative Analysis of Electron Acceleration in Coalescing Magnetic Flux Ropes at Earth’s Magnetopause 
Wenqing Ma, Meng Zhou, and Zhihong Zhong

Coalescence of magnetic flux ropes (MFRs) is suggested as a crucial mechanism for electron acceleration in various astrophysical plasma systems. However, how electrons are being accelerated via MFR coalescence is not fully understood. In this paper, we quantitatively analyze electron acceleration during the coalescence of three MFRs at Earth’s magnetopause using in-situ Magnetospheric Multiscale (MMS) observations. We find that suprathermal electrons are enhanced in the coalescing MFRs than those in the ambient magnetosheath and non-coalescing MFRs. Both first-order Fermi and E acceleration were responsible for this electron acceleration, while the overall effect of betatron mechanism decelerated the electrons. The most intense Fermi acceleration was observed in the trailing part of the middle MFR, while E acceleration occurred primarily at the reconnection sites between the coalescing MFRs. For non-coalescing MFRs, the dominant acceleration mechanism is the E acceleration. Our results further consolidate the important role of MFR coalescence in electron acceleration in space plasma.

How to cite: Ma, W., Zhou, M., and Zhong, Z.: Quantitative Analysis of Electron Acceleration in Coalescing Magnetic Flux Ropes at Earth’s Magnetopause, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2727, https://doi.org/10.5194/egusphere-egu24-2727, 2024.

X4.37
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EGU24-3333
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ECS
Energization of Cold Ions in Asymmetric Reconnection: Particle-in-Cell Simulation 
Liangjin Song, Meng Zhou, Yongyuan Yi, and Xiaohua Deng

Cold ions from Earth's ionosphere and plasmasphere are frequently observed at the Earth's magnetopause, impacting reconnection in ways such as altering the reconnection rate and energy budget. Despite extensive research on reconnection, the fluid properties and kinetics of cold ions in magnetopause reconnection remain unclear. Our recent 2-D particle-in-cell simulation provides new insight into cold ion dynamics in asymmetric reconnection. Our simulation shows that cold ions, initially located only in the magnetosphere, absorb 10% to 25% of the total released magnetic energy, primarily converting it into thermal energy through stochastic heating, that is, the viscous heating associated with the non-gyrotropic pressure tensor. Cold ions are step-by-step accelerated by the Hall electric field during meandering motion across the magnetopause current sheet. The velocity distribution functions of cold ions in different regions are made up of two types of particles, differentiated by their ability to penetrate into the magnetosheath. The reconnection electric field has different effects on these two types of cold ions. As reconnection continues, the velocity distribution functions of the cold ions diffuse, leading to bulking heating. These findings significantly enhance our understanding of cold ion dynamics at the Earth's magnetopause.

How to cite: Song, L., Zhou, M., Yi, Y., and Deng, X.: Energization of Cold Ions in Asymmetric Reconnection: Particle-in-Cell Simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3333, https://doi.org/10.5194/egusphere-egu24-3333, 2024.

X4.38
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EGU24-8362
Collisional effects on relativistic magnetic reconnection 
Kevin Schoeffler, Magnus Deisenhofer, Martha Finke, Emanuel Jeß, Sophia Köhne, and Maria Elena Innocenti

In extreme astrophysical environments around compact objects such as neutron stars and black holes, magnetic reconnection is expected to occur in the relativistic magnetically dominated regime, where the magnetization σ >> 1. These regimes have previously been studied using particle-in-cell (PIC) simulations showing hard power-law spectra, that can help to explain radiation spectra. While kinetic simulations are typically small-scale and collisionless, in realistic astronomical scales, collisional effects also should play a role. In this study, we reproduce the hard power-laws using 2D PIC simulations, and investigate the effects of Coulomb collisions which are taken into account self-consistently using Monte Carlo methods. A large body of research has investigated how the spectra is generated via reconnection in such relativistic systems, but the mechanism remains under debate. Understanding the differences in the energetic particle spectra at large collisional scales, may help shed light on this debate, and provide more accurate spectra to compare with astronomical observations.

How to cite: Schoeffler, K., Deisenhofer, M., Finke, M., Jeß, E., Köhne, S., and Innocenti, M. E.: Collisional effects on relativistic magnetic reconnection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8362, https://doi.org/10.5194/egusphere-egu24-8362, 2024.

X4.39
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EGU24-13599
Development of the electron streaming instability in magnetopause reconnection 
Binbin Tang, Wenya Li, and Chi Wang
The development of the electron streaming instability is usually very fast, making it difficult to be observed from spacecraft observations. However, with a separation of 10s of km, Magnetospheric Multiscale(MMS) spacecraft provide a good opportunity to resolve the spatial evolution of election beams and also the corresponding electron streaming instability. Here, we show such an event in the magnetopause reconnection, in which the accelerated electrons of the sheath origin become unstable at the magnetospheric side, and different MMS spacecraft captures significantly different wave activities. Interestingly, the scattered electrons may even form agyrotropic electron distributions as observed by one MMS spacecraft.
 

How to cite: Tang, B., Li, W., and Wang, C.: Development of the electron streaming instability in magnetopause reconnection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13599, https://doi.org/10.5194/egusphere-egu24-13599, 2024.

X4.40
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EGU24-15779
Transition from slow to fast tearing instability in the kinetic regime: theory and simulations 
Maria Elena Innocenti, Jeremy Dargent, Fulvia Pucci, Kevin Schoeffler, and Elisabetta Boella

Current sheets are ubiquitous in space and astrophysical plasmas, and may become unstable, under appropriate conditions, to the so-called tearing instability, which in turn triggers magnetic reconnection and massive magnetic to kinetic energy conversion.

Over the past decade, significant progress has been made on the initiation of fast reconnection via plasmoid instability in resistive plasmas. However, given the extremely high Lundquist numbers in most natural plasmas, the role of kinetic effects in breaking the frozen-in condition and triggering tearing instability has to be considered.

In this work, we observe by means of fully kinetic Particle In Cell simulations the onset of a fast tearing instability (e-folding time τ∼τA, with τA the Alfven time) in current sheets (CS) with thickness a>di, with di the ion skin depth.

We adopt the model for the transition from slow to fast tearing instability described in Pucci et al 2017 in the kinetic regime and in a double CS framework, where the electron inertial term replaces the resistive term as the dominant non ideal term in the generalised Ohm’s law in the vicinity of the neutral line. 

We show that the simulations verify the model predictions on the critical current sheet aspect ratio (thickness to length) below which the tearing instability growth rate is expected to approach the Alfven time (“fast tearing”).

How to cite: Innocenti, M. E., Dargent, J., Pucci, F., Schoeffler, K., and Boella, E.: Transition from slow to fast tearing instability in the kinetic regime: theory and simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15779, https://doi.org/10.5194/egusphere-egu24-15779, 2024.

X4.41
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EGU24-16388
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ECS
Behaviour of Kinetic Electron and Proton Instabilities in the Magnetosheath Modelled with Semi-Implicit Particle-In-Cell 
Stuart O'Neill, Elisabetta Boella, Alfredo Micera, Daniel Verscharen, and Maria Elena Innocenti

Temperature anisotropies are often encountered in space and astrophysical plasmas. A sufficiently large ratio between the electron temperatures perpendicular and parallel with respect to the magnetic field causes whistler and mirror instabilities to grow. Similarly, a sufficiently large perpendicular proton temperature ratio is expected to result in instabilities such as mirror and proton acoustic instabilities. In the parameter regime surrounding Earth’s magnetosheath linear theory predicts that proton cyclotron instability will have the lowest threshold of all anisotropy-driven instabilities. Despite this, unstable mirror modes are observed in apparent contradiction to linear theory. It has been suggested that an electron perpendicular to parallel temperature anisotropy can alter the relative growth rates of mirror and proton acoustic instabilities by boosting the growth rates of mirror modes. Such an anisotropy could also be consumed by (faster) electron instabilities. Given the potential for cross-species interplay, a thorough understanding of the behaviour of the electron whistler instability, which typically grows fastest compared to instabilities in the electron species, is crucial. By leveraging multidimensional kinetic simulations with the Energy Conserving Semi-Implicit Method ECSIM, this work studies the competition of electron instabilities in parameter space typical of Earth’s magnetosheath. In addition, the possibility that residual electron temperature anisotropy left over after the saturation of electron instabilities can affect the proton acoustic to mirror competition is explored. This second part of the study relies on the semi-implicit nature of the ECSIM code, which allows spatial and temporal resolution to be dimensioned on the basis of the smallest and fastest dynamics expected in the system, rather than the Courant condition that one has to respect for stability in explicit PIC codes. 

How to cite: O'Neill, S., Boella, E., Micera, A., Verscharen, D., and Innocenti, M. E.: Behaviour of Kinetic Electron and Proton Instabilities in the Magnetosheath Modelled with Semi-Implicit Particle-In-Cell, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16388, https://doi.org/10.5194/egusphere-egu24-16388, 2024.

X4.42
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EGU24-20291
Enhanced Energy Conversion by Turbulence in Collisionless Magnetic Reconnection 
Meng Zhou, Runqing Jin, Yongyuan Yi, Hengyan Man, Zhihong Zhong, Ye Pang, and Xiaohua Deng

Magnetic reconnection and turbulence are two of the most significant mechanisms for energy dissipation in collisionless plasma. The role of turbulence in magnetic reconnection poses an outstanding problem in astrophysics and plasma physics. It is still unclear whether turbulence could modify the reconnection process by enhancing the reconnection rate or energy conversion rate. In this study, utilizing unprecedented high-resolution data obtained from the Magnetospheric Multiscale spacecraft, we provide direct evidence that turbulence plays a vital role in promoting energy conversion during reconnection. We reached this conclusion by comparing magnetotail reconnection events with similar inflow Alfven speed and plasma β, but varying amplitudes of turbulence. The disparity in energy conversion was attributed to the strength of turbulence. Stronger turbulence generates more coherent structures with smaller spatial scales, which are pivotal contributors to energy conversion during reconnection. In addition, we find that turbulence has negligible impact on particle heating, but it does affect the ion bulk kinetic energy. These findings significantly advance our understanding of the relationship between turbulence and reconnection in astrophysical plasmas.

How to cite: Zhou, M., Jin, R., Yi, Y., Man, H., Zhong, Z., Pang, Y., and Deng, X.: Enhanced Energy Conversion by Turbulence in Collisionless Magnetic Reconnection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20291, https://doi.org/10.5194/egusphere-egu24-20291, 2024.

X4.43
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EGU24-21996
Comprehensive analysis of CME-driven shocks observed by multi-spacecraft observations 
Silvia Perri, Giuseppe Nisticò, Andrea Mesoraca, Federica Chiappetta, Francesco Pucci, Francesco Malara, Luca Sorriso-Valvo, Fabio Lepreti, and Gaetano Zimbardo

In this study, we aim at analyzing coronal mass ejection (CME)-driven shocks, possibly observed by a constellation of satellites, at the solar source and in the inner heliosphere. We started with the analysis of the CME detected by STEREO-A, SOHO, Parker Solar Probe, and Solar Orbiter between 5 and 6 September 2022. In particular, thanks to the remote observations from Stereo-A, SOHO, and Parker Solar Probe it has been possible to reconstruct the shock wave both in 2D and 3D and to derive shock parameters, such as the compression ratio and the Mach numbers at its source. The analysis has been supported by in-situ observations in the inner heliosphere at different radial distances and longitudes by Solar Orbiter and Parker Solar Probe. It has been found that the shock wave is strong with a high compression ratio both at the source and when detected in the interplanetary space, while the Mach numbers tend to decrease due to a deceleration of the shock. The 3D reconstruction tool setup can be further applied to other CMEs detected by multiple spacecraft. In addition, an investigation on the high-energy protons accelerated at the shock wave has been carried out in order to infer their transport properties in the heliosphere, jointly with the shape of the differential proton energy spectrum. Such an analysis has also been performed for several interplanetary CMEs.
This study is achieved in the context of the research project “Data-based predictions of solar energetic particle arrival to the Earth” funded by the Italian Ministry of Research under the grant scheme PRIN-2022-PNRR.

How to cite: Perri, S., Nisticò, G., Mesoraca, A., Chiappetta, F., Pucci, F., Malara, F., Sorriso-Valvo, L., Lepreti, F., and Zimbardo, G.: Comprehensive analysis of CME-driven shocks observed by multi-spacecraft observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21996, https://doi.org/10.5194/egusphere-egu24-21996, 2024.

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EGU24-2282
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Application of GPU-accelerated Particle-in-cell Simulations in Magnetic Reconnection Associated with Energy Conversion between Field and Particles 
Qiyang Xiong and Shiyong Huang

Magnetic reconnection is a fundamental physical process of rapidly converting magnetic energy into particles in space physics. The electron diffusion region (EDR), which can be split into the inner EDR and outer EDR, is the crucial region during magnetic reconnection. The inner EDR, where the magnetic field is dissipated, is responsible for the heating and acceleration of the electrons. The outer EDR also plays a crucial role where the electrons are decelerated and return the energy to the magnetic field in the pileup region behind the reconnection front (RF). Here we present the studies associated with energy conversions around EDR using fully kinetic particle-in-cell (PIC) simulations of advanced GPU-accelerated computing and Magnetospheric Multiscale (MMS) mission observations. It is found that part of the electrons in the outer EDR are forced backward to the inner EDR by the magnetic tension force to be accelerated again, which we name it by magnetic Marangoni effect. And we also report a novel crater structure of magnetic field behind the RF caused by the continuous impact of the high-speed outflow electron jets. Our PIC simulation scheme based on the GPU architecture can achieve high performance computing and fast accessibility to the simulation results. The scientific findings in our studies propose various approaches for the particle acceleration and energy conversion during magnetic reconnection.

How to cite: Xiong, Q. and Huang, S.: Application of GPU-accelerated Particle-in-cell Simulations in Magnetic Reconnection Associated with Energy Conversion between Field and Particles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2282, https://doi.org/10.5194/egusphere-egu24-2282, 2024.

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EGU24-3461
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Pulse of the Hall term compared to the frozen-in term and the triggering mechanism of magnetic reconnection at the reconnection point 
FuCheng Huang

 The Hall effect closely relates to the decoupling between the motion of ions and that of electrons during magnetic reconnection. It is the key to understand the triggering mechanism of magnetic reconnection. In our previous research result, the energy cascade at the reconnection point is first found (Huang et al. 2018, GRL). It leads to the pulse of the Hall term compared to the frozen-in term at the reconnection point, explaining well the motion decoupling between ions and electrons . In order to understand better the energy cascade at the reconnection point, we will study further the physical process which acts between the energy cascade at the reconnection point and the motion of plasma waves in the reconnection region. The wave-number distribution of both magnetic field and electric field is investigated by use of simulation. The role of Landau damping of KAW in the reconnection region is discussed in detail based on the simulation result. It is also provide a physical mechanism to understand the resistivity which is essential for the colisionless reconnection.

How to cite: Huang, F.: Pulse of the Hall term compared to the frozen-in term and the triggering mechanism of magnetic reconnection at the reconnection point, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3461, https://doi.org/10.5194/egusphere-egu24-3461, 2024.

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EGU24-5176
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Why cannot ions form outflow for electron-only reconnection in kinetic turbulence? 
Meng Zhang, Meng Zhou, Yongyuan Yi, Liangjin Song, Ye Pang, and Hui Xiao

Electron-only magnetic reconnection, in which ions do not couple, has recently been observed in the turbulent magnetosheath and magnetotail and is associated with magnetic flux rope coalescence. This paper reproduces the electron-only reconnection that in turbulent plasma environments via 2.5D particle-in-cell simulations. By statistical analysis and study of individual ion trajectories. We have discovered the reason why Electron-only magnetic reconnection ions cannot form an out flow in turbulence. Due to the weak magnetization effect of ions in turbulence, it is difficult for ions to enter the magnetic reconnection structure from the inflow region (only about 10% in our study). Due to the large cyclotron radius of ions in turbulence compared with the reconnection structure, it is difficult for the reconnected ions to be effectively deflected by the normal magnetic field to form an outflow. The ions are mainly affected by various electric fields generated by magnetic island motion in turbulence. We compared the results with standard magnetic reconnection and performed an energy analysis.

How to cite: Zhang, M., Zhou, M., Yi, Y., Song, L., Pang, Y., and Xiao, H.: Why cannot ions form outflow for electron-only reconnection in kinetic turbulence?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5176, https://doi.org/10.5194/egusphere-egu24-5176, 2024.

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EGU24-7364
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High-speed electron flows in the terrestrial magnetotail 
Huijie Liu, Wenya Li, Binbin Tang, and Chi Wang

High-speed electron flows play a crucial role in the energy dissipation and conversion processes within the terrestrial magnetosphere, particularly in regions associated with magnetic reconnection, such as the vicinity of electron diffusion regions (EDRs) and separatrix layers. NASA's Magnetospheric Multiscale (MMS) mission was specifically designed to reveal electron-scale kinetic processes occurring in Earth's magnetosphere. In this study, we conduct a comprehensive survey of high-speed electron flows in the terrestrial magnetotail, utilizing MMS observations spanning from 2017 to 2021. Our analysis identifies a total of 642 events characterized by electron bulk speeds exceeding 5,000 km/s. Notably, these events exhibit a clear dawn-dusk asymmetry, with 73% of them occurring in the dusk magnetotail. Along the magnetotail's normal direction, we find that 37.7%, 21.8%, and 40.5% of the events are located in the plasma sheet, plasma sheet boundary layer, and lobe region, respectively. The occurrence rate of these events peaks when the magnetic field strength is approximately 19 nT. High-speed electrons predominantly move along magnetic field lines in the plasma sheet boundary layer and lobe region, while in the plasma sheet, they traverse along arbitrary directions with respect to the magnetic field. Our study contributes to a deeper understanding of the complex electron dynamics under various plasma and magnetic field conditions within Earth's magnetotail.

How to cite: Liu, H., Li, W., Tang, B., and Wang, C.: High-speed electron flows in the terrestrial magnetotail, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7364, https://doi.org/10.5194/egusphere-egu24-7364, 2024.

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EGU24-16854
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Comparative simulations of Kelvin-Helmholtz induced magnetic reconnection at the Earth's magnetospheric flanks 
Silvia Ferro, Matteo Faganello, Francesco Califano, and Fabio Bacchini

In this work, we investigate the interaction between the solar wind and the Earth’s magnetosphere by conducting 3D Hall-MHD simulations. Specifically, we focus on the development of the Kelvin-Helmholtz instability (KHI) and its crucial role in driving magnetic reconnection and plasma transport at the magnetopause. The KHI is closely linked to plasma turbulence, as turbulent fluctuations contribute to its growth by facilitating energy transfer and mixing at smaller scales and the KHI itself is a driver for turbulence in plasma dynamics. At Earth's magnetopause, this leads to increased vortex and wave activity and the emergence of secondary KH modes. Our work involves analyzing simulation data and comparing the effects of initial magnetic shear on the development of the KHI. The results show that the presence of magnetic shear significantly influences the latitudinal distribution of vortices and magnetic reconnection events, leading to quantitative differences in the system’s evolution. Despite differences in the global magnetic topology, all simulations exhibit the formation of vortices, secondary KH instabilities, and a turbulent mixing layer during the late nonlinear phase of the instability.

How to cite: Ferro, S., Faganello, M., Califano, F., and Bacchini, F.: Comparative simulations of Kelvin-Helmholtz induced magnetic reconnection at the Earth's magnetospheric flanks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16854, https://doi.org/10.5194/egusphere-egu24-16854, 2024.

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EGU24-17358
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Detection and occurrence rate of ion-scale reconnecting current sheets using Solar Orbiter high cadence data.  
Inmaculada F. Albert, Sergio Toledo-Redondo, Víctor Montagud-Camps, Aida Castilla, Benoît Lavraud, Naïs Fargette, Philippe Louarn, Christopher Owen, and Yannis Zouganelis

Magnetic reconnection is process in which magnetic energy dissipates, turning into kinetic and thermal energy, through the reconfiguration of the magnetic field topology. It has been observed in the solar wind at multiple spatial scales and Sun distances.

The study of magnetic reconnection in large- and medium-scale structures has received closer attention than ion-scale magnetic reconnection, due to the instrumental limitations. Thanks to the Solar Orbiter data, and in particular that from the Proton- Alpha Sensor (PAS) from the Solar Wind Analyser (SWA) instrument, we can now resolve ion velocity distribution functions inside current sheets of thicknesses in the range of a few proton gyroradii. Thus, we are granted the possibility of searching for reconnection signatures at scales near the ion spectral break of the turbulent cascade, and we can investigate its prevalence and its impact in heating and accelerating the solar wind.

In this presentation introduce an algorithm we are developing to automatically identify reconnecting current sheets near the ion spectral break in the solar wind. We find that the uncertainty associated with ion bulk velocity measurements constrains the Alfvén velocities that can be resolved with the available data, resulting in a lower threshold for the detectable reconnecting component of the magnetic field.

We present preliminary results, consisting of a catalog of small-scale current sheets in the solar wind and an assessment of reconnection frequency and prevalence. We show the relative occurrence of reconnecting versus Alfvénic current sheets near ion-scales and discuss the relevance of small-scale magnetic reconnection for energy dissipation in solar wind turbulence.

How to cite: F. Albert, I., Toledo-Redondo, S., Montagud-Camps, V., Castilla, A., Lavraud, B., Fargette, N., Louarn, P., Owen, C., and Zouganelis, Y.: Detection and occurrence rate of ion-scale reconnecting current sheets using Solar Orbiter high cadence data. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17358, https://doi.org/10.5194/egusphere-egu24-17358, 2024.