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.

中文翻译：

---

无碰撞磁重联过程中边界条件对高能电子分布的影响

我们进行了二维细胞内粒子模拟，以研究边界条件对磁重联演化的影响。结果表明，边界条件对于这种演化至关重要。具体来说，在传统周期性边界（PB）和全开边界（OB）条件下，系统达到最快重连率之前的演化非常相似。然而，随后两个案例之间出现了分歧。在PB情况下，重联电场迅速下降，甚至变为负值，表明重联过程发生逆转。相反，系统在 OB 情况下保持快速重连阶段。超热电子在两种模拟情况的分界面附近和排气区域中产生。在电子密度耗尽层和偶极前区，OB情况下产生较大比例的超热电子。在这两种情况下，中能电子主要位于 X 线附近和重联位点下游。然而，在 OB 情况下，它们也可以在沿分界线的电子空穴中产生。在反向重联阶段之前，PB 壳中不存在高能电子。相比之下，在 OB 情况下，薄而细长的电子电流层中大约 20% 的电子是高能的。