Lei Wang, Can Huang, Dongke Chen, Zhongwei Yang, A. Du, Y. Ge
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引用次数: 0
摘要
我们进行了二维粒子入胞模拟,以研究边界条件对磁重联演化的影响。结果表明,边界条件对这种演化至关重要。具体来说,在传统周期性边界条件(PB)和完全开放边界条件(OB)的情况下,系统在达到最快再连接速率之前的演化非常相似。然而,之后两种情况就出现了差异。在 PB 条件下,重连接电场迅速下降,甚至变为负值,表明重连接过程发生了逆转。相反,在 OB 情况下,系统保持着快速重连接阶段。两种模拟情况的分离矩阵附近和排气区都产生了过热电子。在电子密度耗尽层和双极化前沿区域,OB 情况下产生的超热电子比例更大。在两种情况下,中能电子主要位于 X 线附近和再连接点下游。不过,在转子情况下,中能电子也可能在沿分离矩阵的电子空穴中产生。在反向重联阶段之前,PB 情况下不存在高能电子。相反,在 OB 情况下,细长电子流层中约有 20% 的电子是高能电子。
The influence of boundary conditions on the distribution of energetic electrons during collisionless magnetic reconnection
We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolution. Specifically, in the cases of traditional periodic boundary (PB) and fully-opened boundary (OB) conditions, the evolutions are quite similar before the system achieves the fastest reconnection rate. However, differences emerge between the two cases afterward. In the PB case, the reconnection electric field experiences a rapid decline and even becomes negative, indicating a reversal of the reconnection process. In contrast, the system maintains a fast reconnection stage in the OB case. Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases. In the electron density depletion layer and the dipolarization front region, a larger proportion of suprathermal electrons are produced in the OB case. Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases. However, in the OB case, they can also be generated in the electron holes along the separatrix. Before the reverse reconnection stage, no high-energy electrons are present in the PB case. In contrast, about 20% of the electrons in the thin and elongated electron current layer are high-energy in the OB case.
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