Free energy source for flow shear driven instabilities in electron-magnetohydrodynamics

Abstract

The paper discusses the free energy source for the flow shear driven instability in the context of electron-magnetohydrodynamic (EMHD) system. In EMHD as the electron flow velocity also corresponds to the current in the system, the flow shear driven instability has often been identified both as the fluid Kelvin-Helmholtz (KH)-like mode and as the current gradient driven sausage and kinklike modes. It has been shown here that the free energy source for the flow shear driven instability is the kinetic energy of the electron flow and the instability is essentially a fluid KH mode. The manuscript also provides interpretations for certain characteristic features, such as existence of a threshold wavenumber along the flow direction, the order of magnitude estimation of the growth rate, etc., from physical considerations.