Electron acceleration in a coil target-driven low-βmagnetic reconnection simulation  

作　　者：Jiacheng Yu Jiayong Zhong Yongli Ping Weiming An 

机构地区：[1]Department of Astronomy and Institute for Frontiers in Astronomy and Astrophysics,Beijing Normal University,Beijing 100875,China

出　　处：《Matter and Radiation at Extremes》2023年第6期30-40,共11页极端条件下的物质与辐射（英文）

基　　金：This work was supported by the National Key R&D Program of China(Grant Nos.2022YFA1603200 and 2022YFA1603203);the National Natural Science Foundation of China(Grant Nos.12325305,12175018,12135001,and 12075030);the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25030700).We express our gratitude to X.-G.Wang,K.Huang,X.-X.Yuan,and C.-Q.Xing for their discussions.Thanks to Beijing Super Cloud Computing Center for providing the computational resources.

摘　　要：Magnetic reconnection driven by a capacitor coil target is an innovative way to investigate low-βmagnetic reconnection in the laboratory,whereβis the ratio of particle thermal pressure to magnetic pressure.Low-βmagnetic reconnection frequently occurs in the Earth’s magnetosphere,where the plasma is characterized byβ≲0.01.In this paper,we analyze electron acceleration during magnetic reconnection and its effects on the electron energy spectrum via particle-in-cell simulations informed by parameters obtained from experiments.We note that magnetic reconnection starts when the current sheet is down to about three electron inertial lengths.From a quantitative comparison of the different mechanisms underlying the electron acceleration in low-βreconnection driven by coil targets,we find that the electron acceleration is dominated by the betatron mechanism,whereas the parallel electric field plays a cooling role and Fermi acceleration is negligible.The accelerated electrons produce a hardened power-law spectrum with a high-energy bump.We find that injecting electrons into the current sheet is likely to be essential for further acceleration.In addition,we perform simulations for both a double-coil co-directional magnetic field and a single-coil one to eliminate the possibility of direct acceleration of electrons beyond thermal energies by the coil current.The squeeze between the two coil currents can only accelerate electrons inefficiently before reconnection.The simulation results provide insights to guide future experimental improvements in low-βmagnetic reconnection driven by capacitor coil targets.

关 键 词：RECONNECTION ACCELERATION MAGNETIC 

分 类 号：P35[天文地球—空间物理学]