Turbulent mixing and transport of collisionless plasmas across a stratified velocity shear layer

Abstract

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.