Separatrices of magnetic reconnection host intense perpendicular Hall electric fields. The fields are produced by the decoupling of the ion and electron components and are associated with the in-plane electrostatic potential drop between the inflow and outflow regions. The width of these structures is typically less than the ion inertial length, which is small enough to demagnetize ions as they cross the layer. We investigate ion acceleration at separatrices by means of 2D particle-in-cell simulations of magnetic reconnection for two limiting cases: (1) a “GEM-like” setup (here GEM stands for geospace environmental modeling reconnection challenge) with the lobe ion thermal velocity equal to the thermal velocity of the initial current sheet ions, which is comparable to the Alfvén velocity and (2) a “cold” ion setup, in which the temperature of the background lobe ions is 1/100 of the initial current sheet temperature. The separatrix Hall electric field is balanced by the ion inertia term in the cold background simulations. The effect is indicative of the quasi-steady local perpendicular acceleration. The electric field introduces a cross field beam of unmagnetized particles, which makes the ion distribution function strongly non-gyrotropic and susceptible to sub-ion scale instabilities. This acceleration mechanism nearly vanishes in the hot ion background simulations. Our particle-in-cell simulations are complemented by one-dimensional test particle calculations. They show that the hot ion particles experience energy-scattering after crossing the accelerating layer, whereas cold ions are uniformly energized up to the energies comparable to the electrostatic potential drop between the inflow and outflow regions.

中文翻译：

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磁重新连接期间分离线上的冷离子通电

磁性重新连接的分离物承载着强烈的垂直霍尔电场。这些场是通过离子和电子成分的去耦产生的，并且与流入和流出区域之间的面内静电势下降有关。这些结构的宽度通常小于离子惯性长度，该离子惯性长度小到足以使离子在穿过层时退磁。我们通过在两个极限情况下通过磁重连接的2D单元内粒子模拟研究分离条件下的离子加速度：（1）具有叶离子热的“类GEM”设置（此处GEM代表地理空间环境建模重连接挑战）速度等于初始当前薄层离子的热速度，可以与Alfvén速度和（2）“冷”离子设置相媲美，其中背景叶离子的温度为当前当前薄板温度的1/100。在冷背景模拟中，分离层霍尔电场由离子惯性项平衡。该效果表示准稳态局部垂直加速度。电场会引入未磁化粒子的交叉场光束，这使离子分布函数具有很强的非回旋性，并且易受亚离子尺度不稳定性的影响。这种加速机制在热离子背景模拟中几乎消失了。我们的单元格粒子模拟是一维测试粒子计算的补充。他们表明，热离子粒子在穿过加速层后会发生能量散射，