Fully kinetic simulations of undriven magnetic reconnection with open boundary conditions
Fully kinetic simulations of undriven magnetic reconnection with open boundary conditions
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DOI：
10.1063/1.2218817
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发表时间：
2006-07-01
影响因子：
2.2
通讯作者：
Karimabadi, Homa
中科院分区：
文献类型：
--
作者：
Daughton, William;Scudder, Jack;Karimabadi, Homa
磁重联的动力学模拟通常采用周期性的边界条件，限制结果在物理上有意义的持续时间。为了解决这个问题，提出了一个新的模型，是开放的粒子，磁通量和电磁辐射。该模型被用来检查在一个单一的x点初始化的中性表中的非驱动重联。虽然在早期的结果与以前的定期研究非常一致，但在更长的时间间隔内的演变完全不同。特别地，观察到电子扩散区域的长度随时间增加，导致形成扩展的电子电流片。结果，电子扩散区域形成瓶颈，并且重连率显著降低。周期性地，电子层变得不稳定并产生次级岛，将扩散区分成两个较短的部分。生长一段时间后，岛被弹出，扩散区再次扩大，直到形成新的岛。如果次级岛的生成仍然足够稳健，则快速重连仍然是可能的。这些结果表明，在中性片重联可能是固有的不稳定，并提出了严重的问题，霍尔介导的重联的标准模型。(c)2006年，美国物理学会。
Kinetic simulations of magnetic reconnection typically employ periodic boundary conditions that limit the duration in which the results are physically meaningful. To address this issue, a new model is proposed that is open with respect to particles, magnetic flux, and electromagnetic radiation. The model is used to examine undriven reconnection in a neutral sheet initialized with a single x-point. While at early times the results are in excellent agreement with previous periodic studies, the evolution over longer intervals is entirely different. In particular, the length of the electron diffusion region is observed to increase with time resulting in the formation of an extended electron current sheet. As a consequence, the electron diffusion region forms a bottleneck and the reconnection rate is substantially reduced. Periodically, the electron layer becomes unstable and produces a secondary island, breaking the diffusion region into two shorter segments. After growing for some period, the island is ejected and the diffusion region again expands until a new island is formed. Fast reconnection may still be possible provided that the generation of secondary islands remains sufficiently robust. These results indicate that reconnection in a neutral sheet may be inherently unsteady and raise serious questions regarding the standard model of Hall mediated reconnection. (c) 2006 American Institute of Physics.