Large-scale parallel electric fields and return currents in a global simulation model
Large-scale parallel electric fields and return currents in a global simulation model
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DOI：
10.1063/1.5120373
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发表时间：
2019-07
影响因子：
2.2
通讯作者：
H. Arnold;J. Drake;M. Swisdak;J. Dahlin
中科院分区：
文献类型：
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作者：
H. Arnold;J. Drake;M. Swisdak;J. Dahlin
一个新的计算模型，kglobal，正在开发中，以探索高能电子生产通过磁重联在宏观系统。该模型基于这样的发现：重联过程中高能电子的产生是由大尺度磁场中的费米反射控制的，而不是由动力学尺度边界层中局部的平行电场控制的。因此，该模型消除了这些边界层。然而，尽管围绕磁性x线和相关的分隔线发展的平行电场在产生高能电子方面并不重要，但存在大规模电场，其启动低能电子的加热并驱动伴随着开放系统中的高能电子逃逸的冷电子返回电流。这种宏观尺度的电场是由电子压力中的磁场对准梯度产生的。我们已经升级了kglobal，以包括这种大规模的电场，同时保持节能。新的模型进行了测试，通过探索电子声学模式的动态发展作为两个电子物种的存在的后果：热动力学和冷流体电子。值得注意的是，电子声学模式的阻尼被kglobal精确地捕获。此外，已经确定kglobal正确地描述了平行电场与逃逸热电子的相互作用的动力学，这是通过使用粒子单元（PIC）代码p3d进行基准模拟来实现的。
A new computational model, kglobal, is being developed to explore energetic electron production via magnetic reconnection in macroscale systems. The model is based on the discovery that the production of energetic electrons during reconnection is controlled by Fermi reflection in large-scale magnetic fields and not by parallel electric fields localized in kinetic scale boundary layers. Thus, the model eliminates these boundary layers. However, although the parallel electric fields that develop around the magnetic x-line and associated separatrices are not important in producing energetic electrons, there is a large scale electric field that kickstarts the heating of low-energy electrons and drives the cold-electron return current that accompanies escaping energetic electrons in open systems. This macroscale electric field is produced by magnetic-field-aligned gradients in the electron pressure. We have upgraded kglobal to include this large-scale electric field while maintaining energy conservation. The new model is tested by exploring the dynamics of electron acoustic modes which develop as a consequence of the presence of two electron species: hot kinetic and cold fluid electrons. Remarkably, the damping of electron acoustic modes is accurately captured by kglobal. Additionally, it has been established that kglobal correctly describes the dynamics of the interaction of the parallel electric field with escaping hot electrons through benchmarking simulations with the Particle-In-Cell (PIC) code p3d.