Electromagnetic electron Kelvin–Helmholtz instability
Electromagnetic electron Kelvin–Helmholtz instability
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DOI：
10.1063/5.0150895
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发表时间：
2023-06
影响因子：
2.2
通讯作者：
H. Che;G. Zank
中科院分区：
文献类型：
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作者：
H. Che;G. Zank
在电子动力学尺度上，离子和电子解耦，电子惯性长度∼de上的电子速度剪切可以触发电磁（EM）电子开尔文-亥姆霍兹不稳定性（EKHI）。在本文中，我们提出了对具有阶跃函数电子剪切流的无粘性无碰撞等离子体中的 EM EKHI 的分析研究。我们证明，在不可压缩无碰撞等离子体中，理想电子冻结条件 E+ve×B/c=0 必须被打破，EM EKHI 才会发生。在阶跃函数电子剪切流中，理想电子冻结条件被磁通量守恒取代，即∇×(E+ve×B/c)=0，产生类似于标准理想不可压缩磁流体动力学KHI的色散关系。由于磁张力，与电子流平行的磁场抑制了 EM EKHI。 EKHI的EM模式的阈值是(k·ΔUe)2>ne1+ne2ne1ne2[ne1(vAe1·k)2+ne2(vAe2·k)2]，其中vAe=B/(4πmene)1/2，ΔUe和ne分别是电子流速度剪切和密度。 EM模式的增长率为γem∼Ωce，即电子陀螺频率。
On electron kinetic scales, ions and electrons decouple, and electron velocity shear on electron inertial length ∼de can trigger electromagnetic (EM) electron Kelvin–Helmholtz instability (EKHI). In this paper, we present an analytic study of EM EKHI in an inviscid collisionless plasma with a step-function electron shear flow. We show that in incompressible collisionless plasma, the ideal electron frozen-in condition E+ve×B/c=0 must be broken for the EM EKHI to occur. In a step-function electron shear flow, the ideal electron frozen-in condition is replaced by magnetic flux conservation, i.e., ∇×(E+ve×B/c)=0, resulting in a dispersion relation similar to that of the standard ideal and incompressible magnetohydrodynamics KHI. The magnetic field parallel to the electron streaming suppresses the EM EKHI due to magnetic tension. The threshold for the EM mode of the EKHI is (k·ΔUe)2>ne1+ne2ne1ne2[ne1(vAe1·k)2+ne2(vAe2·k)2], where vAe=B/(4πmene)1/2, ΔUe, and ne are the electron streaming velocity shear and densities, respectively. The growth rate of the EM mode is γem∼Ωce, which is the electron gyro-frequency.