Electron Heating in Magnetosheath Turbulence: Dominant Role of the Parallel Electric Field Within Coherent Structures

Xu, Qianyun; Zhou, Meng; Ma, Wenqing; He, Jiansen; Huang, S. Y.; Zhong, Zhihong; Pang, Y.; Deng, Xiaohua

doi:10.1029/2022gl102523

Cited by 5 publications

(5 citation statements)

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“…The contribution by E || (Figure 6b) has a slight decreasing trend over time, where the median value is above 50% at the early time and below 50% later. The dominant role of E || energization is consistent with recent observations in magnetosheath turbulence where the pdf of the work done by E || to electrons is found (Xu et al, 2023), and kinetic simulations of turbulence where T e|| enhancements are found to be significant around the reconnection onset (Franci et al, 2022). For the decomposition of j e⊥ • E ⊥ , at the later time, the relative importance is consistent with the laminar reconnection studies (e.g., Dahlin et al, 2014Dahlin et al, , 2015Dahlin et al, , 2016Li et al, 2015Li et al, , 2017: the Fermi term (Figure 6c) dominates the positive contribution, and the Betatron term (Figure 6d) is negative.…”

Section: Electron Energizationsupporting

confidence: 90%

Electron Heating Associated With Magnetic Reconnection in Foreshock Waves: Particle‐In‐Cell Simulation Analysis

Wang,

Yang

2023

JGR Space Physics

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Magnetic reconnection occurs in turbulent plasmas like shock transition regions, while its role in energy dissipation therein is not yet clear. We perform a 2D particle‐in‐cell simulation of foreshock waves and study electron heating associated with reconnection. The probability distribution of Te exhibits a shift to higher values near reconnection X‐lines compared to elsewhere. By examining the Te evolution using the superposed epoch analysis, we find that Te is higher in reconnection than in non‐reconnecting current sheets, and Te increases over the ion cyclotron time scale. The heating rate of Te is 10%–40% miVA2, where VA is the average ion Alfvén speed in reconnection regions, which demonstrates the importance of reconnection in heating electrons. We further investigate the bulk electron energization mechanisms by decomposing je · E under guiding center approximations. Around the reconnection onset, E|| dominates the total energization partly contributed by electron holes, and the perpendicular energization is dominated by the magnetization term associated with the gyro‐motion in inhomogeneous fields. The Fermi mechanism contributes negative energization at early time mainly due to Hall effects, and later the outflow in the reconnection plane contributes more dominant positive values. After a couple of ion cyclotron periods from reconnection onset, the Fermi mechanism dominates the energization. A critical factor for initiating reconnection is to drive current sheets to the de‐scale thickness. The reconnection structures can be complicated due to flows originated from the ion‐scale waves, and interactions between multiple reconnection sites. Visualizing such complicated features in simulations may assist future analysis of observation data.

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Section: Electron Energizationsupporting

confidence: 90%

Electron Heating Associated With Magnetic Reconnection in Foreshock Waves: Particle‐In‐Cell Simulation Analysis

Wang,

Yang

2023

JGR Space Physics

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“…Figure 3b exhibits the κ value of electrons with 1 keV energy, encompassing the energy range of most electrons (Ma et al, 2020;Xu et al, 2023). Throughout the entire interval, the κ value consistently exceeds 3, indicating that electrons satisfy the guiding center approximation within the three MFRs, allowing for the quantification of the power densities of the three acceleration mechanisms using Equations 1-3.…”

Section: 1029/2023ja032270mentioning

confidence: 96%

“…In principle, the first-order acceleration of a well-magnetized particle includes Fermi, betatron mechanism, and direct acceleration by parallel electric field (e.g., Northrop, 1963). The power densities of the first-order Fermi, betatron, and E || mechanism can be estimated using the following formulas (Akhavan-Tafti et al, 2019;Dahlin et al, 2014;Ma et al, 2020Ma et al, , 2022Xu et al, 2023;Zhong et al, 2020):…”

Section: 1029/2023ja032270mentioning

confidence: 99%

Quantitative Analysis of Electron Heating and Acceleration in Coalescing Magnetic Flux Ropes at Earth's Magnetopause

Ma,

Zhou,

Zhong

et al. 2024

JGR Space Physics

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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/heated via MFR coalescence is not fully understood. In this paper, we quantitatively analyze electron heating and 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 process cooled 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 mechanism for energizing electrons is the E|| acceleration. Our results further consolidate the important role of MFR coalescence in electron heating/acceleration in space plasma.

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“…Retino et al (2007) reported the first reconnection event in the magnetosheath with Cluster observations, where an ion diffusion region is identified, and they proposed that magnetic reconnection occurs in the current sheet formed due to plasma turbulence. More reconnection events have recently been observed with the high-resolution measurements provided by the Magnetospheric Multiscale spacecraft, and the width of the associated current sheets ranges from the ion kinetic scale to the electron kinetic scale (Yordanova et al 2016;Vörös et al 2017;Phan et al 2018;Gingell et al 2019Gingell et al , 2020Stawarz et al 2019;Wang et al , 2021Xu et al 2023). Most of these reconnection events have been observed downstream of a quasi-parallel shock, which indicates that magnetic reconnection may occur ubiquitously in the quasi-parallel-shocked magnetosheath.…”

Section: Introductionmentioning

confidence: 98%

Upstream Plasma Waves and Downstream Magnetic Reconnection at a Reforming Quasi-parallel Shock

Lu,

Guo,

Yang

et al. 2024

ApJ

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With the help of a two-dimensional particle-in-cell simulation model, we investigate the long-time evolution (near 100 Ω i 0 − 1 , where Ω i0 is the ion gyrofrequency in the upstream) of a quasi-parallel shock. Some of the upstream ions are reflected by the shock front, and their interactions with the incident ions excite low-frequency magnetosonic waves in the upstream. Detailed analyses have shown that the dominant wave mode is caused by the resonant ion–ion beam instability, and the wavelength can reach tens of ion inertial lengths. Although these plasma waves are directed toward the upstream in the upstream plasma frame, they are brought by the incident plasma flow toward the shock front, and their amplitude is enhanced during the approaching. The interaction of the upstream plasma waves with the shock leads to the cyclic reformation of the shock front, and the reformation period is slightly larger than 10 Ω i 0 − 1 . When crossing the shock front, these large-amplitude plasma waves are compressed and evolve into current sheets in the transition region of the shock. At last, magnetic reconnection occurs in these current sheets, accompanying the generation of magnetic islands. Simultaneously, there still exist plasma waves of another kind, with the wavelength of several ion inertial lengths in the ramp of the shock, which are excited by the nonresonant ion–ion beam instability. The current sheets in the transition region are distorted and broken into several segments when the plasma waves of this kind are transmitted into the downstream, where magnetic reconnection and the generated islands have a much smaller size. No obvious ion flow can be observed around some X-lines produced in the magnetic reconnection, and this implies that electron-only reconnection may occur.

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Electron Heating in Magnetosheath Turbulence: Dominant Role of the Parallel Electric Field Within Coherent Structures

Cited by 5 publications

References 50 publications

Electron Heating Associated With Magnetic Reconnection in Foreshock Waves: Particle‐In‐Cell Simulation Analysis

Electron Heating Associated With Magnetic Reconnection in Foreshock Waves: Particle‐In‐Cell Simulation Analysis

Quantitative Analysis of Electron Heating and Acceleration in Coalescing Magnetic Flux Ropes at Earth's Magnetopause

Upstream Plasma Waves and Downstream Magnetic Reconnection at a Reforming Quasi-parallel Shock

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