Turbulent mixing and transport of collisionless plasmas across a stratified velocity shear layer
Turbulent mixing and transport of collisionless plasmas across a stratified velocity shear layer
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DOI：
10.1029/2004ja010988
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发表时间：
2006-05-27
影响因子：
2.8
通讯作者：
Hoshino, Masahiro
中科院分区：
文献类型：
--
作者：
Matsumoto, Yosuke;Hoshino, Masahiro
对非均匀密度介质和横向磁场中开尔文-亥姆霍兹 (K-H) 不稳定性的二维模拟表明，非线性不稳定性会导致湍流的强烈发展。理想的MHD模拟结果表明，两种介质之间的密度差异对快速湍流混合和传输起着至关重要的作用。湍流的发生不仅是由二次 K-H 不稳定性触发的，而且也是由正常 K-H 涡旋内部密度界面处的瑞利-泰勒 (R-T) 不稳定性触发的。二次 R-T 不稳定性通过将稠密流体输送到稀薄区域来改变宏观结构，而二次 K-H 不稳定性只是湍流的种子。还进行了完整的粒子模拟，并再现了与理想 MHD 类似的结果，只是二次 R-T 不稳定性引起的强静电场会散射离子并使电子密度界面变形。结果，与均匀密度情况下的结果相比，混合区域异常快速地增加并在空间上延伸。
Two-dimensional simulations of the Kelvin-Helmholtz (K-H) instability in a nonuniform density medium and with the transverse magnetic field show the strong development of turbulence through nonlinear instabilities. Ideal MHD simulation results have indicated that the difference in density between two media plays a crucial role on the fast turbulent mixing and transport. The onset of the turbulence is triggered not only by the secondary K-H instability but also by the Rayleigh-Taylor (R-T) instability at the density interface inside the normal K-H vortex. The secondary R-T instability alters macroscopic structure by transporting dense fluids to tenuous region, while the secondary K-H instability is just a seed for the turbulence. Full particle simulations are also conducted and reproduces the similar result of the ideal MHDs, except that the strong electrostatic field caused by the secondary R-T instability scatters ions and deforms the electron density interface. As a result, the mixing area increases anomalously fast and extends spatially as compared to the result in the uniform density case.