Magnetohydrodynamic Kelvin–Helmholtz instabilities of supersonic shear layers with finite interface thickness and heat flux in anisotropic space plasmas

Abstract

ABSTRACTThe linear magnetohydrodynamic Kelvin–Helmholtz instability (KHI) in an anisotropic plasma is studied. The governing equations obtained as the 16 moments of Boltzmann–Vlasov kinetic equations, including the heat flow, are applied. In the case of tangential discontinuity between the supersonic flows along the magnetic field, the calculated growth rates as functions of the anisotropic plasma properties allow us to conclude that quasi-transverse modes grow faster. Then, dispersion equations for the KHI of quasi-transverse modes are derived, considering the finite width of the transition zone with different velocity profiles. For these modes, when the role of heat flow is not important, the plasma parameters are controlled so that the fundamental plasma instabilities (firehose and mirror) do not affect the KHI. The problem is solved analytically, which will be helpful in verifying numerical simulations. In contrast to the tangential discontinuity, the finite width of the transition layer confines KHI excitation as the wavenumber increases. In the general case of oblique propagation (when heat flux complicates the problem), the boundary value problem is solved to determine the spectral eigenvalues. In particular, it is observed that the fundamental plasma instabilities that arise in the transition zone between flows with a finite width can modify and considerably enhance the KHI.