基于电子回旋动理学和离子完全动理学的电流片不稳定性的模拟研究

Investigation of Plasma Instabilities in Current Sheet Based on Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation

采用电子回旋动理学和离子完全动理学模拟程序研究了电流片中的不稳定性问题,其中考虑了自洽电流和额外激励电流两种情况.通过对电子采用回旋平均处理,该模拟方法相对于电子离子完全动理学模拟更为经济有效,同时还保留了重要的电子拉莫尔半径、波粒共振、电子的热压力非对角项等效应.该理论框架涵盖了从低频大尺度磁流体问题到高频小空间尺度例如低杂波以及哨声波等.模拟结果给出了电流片不稳定性的实空间分布结构以及线性增长率随物理参量的依赖关系.进一步分析表明,电流片中心不稳定性为静电模式,该不稳定性不足以激发快速磁场重联.此外给出了带电粒子速度各向异性的理论推导过程.

A particle simulation based on gyrokinetic electron and fully kinetic ion(GeFi)method is conducted to investigate the plasma instabilities of the current sheet in the absence and presence of an artificial particle drift along the guide field.In contrast to the fully-kinetic electron and ion simulation,Ge Fi has a great advantage in the aspect of computation efficiency by removing the rapid cyclotron electron motion while retaining the important effects of Larmor radius,wave-particle interaction and electron off-diagonal thermal pressure,thereby a wide range of spatial and temporal problems ranging from low frequency magnetohydrodynamic to lower hybrid and whistler scales is covered.The simulation results show a good agreement with the existing theories and the electrostatic lower hybrid instability is observed,which is not strong enough to excite the fast magnetic reconnection.The mode structures in real space and dependence of typical parameters are given.In addition,the temperature anisotropy of electrons and ions is discussed theoretically and the corresponding linear growth rate of the electrostatic instability is given.