Kelvin-Helmholtz instability of the collisionless anisotropic space plasma

TL;DR

This paper investigates the Kelvin-Helmholtz instability in collisionless anisotropic plasmas using MHD equations derived from kinetic theory, analyzing growth rates and wave propagation in shear flows relevant to solar wind turbulence.

Contribution

It provides a detailed analysis of KHI in collisionless anisotropic plasmas considering heat flux and finite transition layers, extending previous fluid models.

Findings

Growth rates depend on plasma anisotropy and shear velocity.

Finite transition layer width constrains KHI at high wavenumbers.

Instability may dissipate large-scale Alfvén wave turbulence.

Abstract

The linear MHD Kelvin-Helmholtz instability (KHI) in an anisotropic plasma concerning the direction of an external magnetic field is examined in detail. For this purpose, the MHD equations are used to describe the motion of plasma as a fluid, which is derived from 16 moments of Boltzmann-Vlasov kinetic equations for collisionless plasma. In addition, the heat flux along the magnetic field is taken into account. The growing rates of KHI are calculated as functions of the anisotropic plasma properties for a shear flow along the magnetic field at supersonic velocities. On the other hand, the quasi-transverse propagation of surface waves between flows with varying velocities is thoroughly examined for both zero-width and finite-width transition layers. In contrast to the tangential discontinuity, it is proved that the limiting breadth of the transition layer constrains the KHI excitation as the wavenumber grows. The instability under investigation could be one of the main ways of dissipation of large-scale low-frequency Alf\'en wave turbulence existing in the solar wind plasma.