Electromagnetic hybrid‐code simulation of magnetic reconnection: Velocity distribution functions of accelerated ions
Electromagnetic hybrid‐code simulation of magnetic reconnection: Velocity distribution functions of accelerated ions
复制标题
磁重联的电磁混合代码模拟：加速离子的速度分布函数
DOI：
10.1029/97gl01206
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发表时间：
1997
影响因子：
5.2
通讯作者：
S. Machida
中科院分区：
文献类型：
--
作者：
J. Nakabayashi;S. Machida
采用2 - 1/2维电磁混合方法模拟了地球磁尾磁场重联过程中的粒子加速现象。通过在初始静态Harris解的中性片上增加一个局域异常电阻率，实现了自发磁场重联。我们发现，在重联开始后，除了传统的黎明到黄昏的电场外，还产生了两种特征电场。第一种类型的电场是指向中性片在膨胀的等离子体片边界层（PSBL），导致冷离子朝下漂移。第二种类型的电场被定向为常规的黎明到黄昏的等离子体片中的组件，但具有远离扩散区域的显著大的组件。虽然没有形成发育良好的慢模式激波，但该场在等离子体射流形成中发挥了重要作用。第一类电场作用下离子与电场之间的能量传递是第二类电场作用下离子与电场之间能量传递的3倍。除了这些垂直电场之外，扩展等离子体片（早期等离子体团）前面的场对准电场引起平行离子加速。在扩展等离子体片和PSBL中的朝晨漂移产生了非零的By场，其极性相对于中心扩散区呈现八极结构。
A 2‐1/2 dimensional electromagnetic hybrid simulation was conducted to explore particle acceleration in the magnetic reconnection process in the Earth magnetotail. By adding a localized anomalous resistivity to the neutral sheet of initial static Harris solution, we realized a spontaneous magnetic reconnection. We found that two kinds of characteristic electric fields were generated in addition to the conventional dawn‐to‐dusk electric field after the reconnection commenced. The first type of the electric field is directed toward the neutral sheet in the expanded plasma sheet boundary layer (PSBL), resulting in a dawnward drift of cold ions. The second type of electric field was directed as the conventional dawn to dusk component in the plasma sheet, but with a significantly large component away from the diffusion region. Though well‐developed slow mode shocks were not formed, this field played a significant role in plasma jet formation. The energy transfer from the electric field to the ions with the first type electric field was three times higher than with that the second type field. In addition to these perpendicular electric fields, the field‐aligned electric field in front of expanding plasma sheet (early‐phase plasmoid) caused a parallel ion acceleration. The dawnward plasma drift in the expanded plasma sheet and PSBL yielded a nonzero By field whose polarity showed an octupole structure with respect to the central diffusion region.