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

Abstract

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.

Electron Acceleration via Secondary Reconnection in the Separatrix Region of Magnetopause Reconnection

“…The peak value of J•E ' is comparable to that observed in most magnetopause reconnection electron diffusion regions (EDRs) (Burch et al, 2016;Webster et al, 2018;Zhou et al, 2017;Zhong et al, 2019). where ρ e is the electron mass density, P e is the electron thermal pressure tensor and V e is the electron bulk velocity (Eastwood et al, 2013;2020;Wang et al, 2023). We see and +M directions at electron inflow C, but much less than H e .…”