Magnetic reconnection driven by a capacitor coil target is an innovative way to investigate low-β magnetic reconnection in the laboratory, where β is the ratio of particle thermal pressure to magnetic pressure. Low-β magnetic reconnection frequently occurs in the Earth’s magnetosphere, where the plasma is characterized by β ≲ 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-β reconnection 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-β magnetic reconnection driven by capacitor coil targets.

中文翻译：

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线圈目标驱动的低β磁重联仿真中的电子加速

由电容器线圈目标驱动的磁重联是在实验室中研究低β磁重联的创新方法，其中β是粒子热压力与磁压力的比率。低β磁重联经常发生在地球磁层中，其中等离子体的特征是β≲0.01。在本文中，我们通过根据实验获得的参数进行的粒子内模拟来分析磁重联过程中的电子加速及其对电子能谱的影响。我们注意到，当电流片减小到大约三个电子惯性长度时，磁​​重联开始。通过对线圈靶驱动的低β重联中电子加速的不同机制的定量比较，我们发现电子加速主要由电子感应加速器机制主导，而平行电场起冷却作用，费米加速可以忽略不计。加速的电子产生具有高能凸点的硬化幂律谱。我们发现将电子注入电流片可能对于进一步加速至关重要。此外，我们还对双线圈同向磁场和单线圈同向磁场进行了模拟，以消除线圈电流直接加速电子超过热能的可能性。两个线圈电流之间的挤压只能在重新连接之前低效地加速电子。仿真结果为指导电容器线圈目标驱动的低β磁重联的未来实验改进提供了见解。