Different effects of suprathermal electrons and ions on drift instabilities in non-uniform plasmas

Abstract

The paper studies the drift instability in Kappa-distributed inhomogeneous plasmas. Weak inhomogeneity and local approximation are assumed. The linear dispersion relation is expressed in a novel integral representation that involves the standard plasma dispersion functions defined in Maxwellian plasmas rather than the generalized plasma dispersion function modified by the Kappa distribution. The analytical solutions of wave frequency and growth rate are derived when the wave speed is larger than the ion thermal speed but smaller than the electron thermal speed. The unstable drift mode is found to have a lower limit of wavenumber due to the suprathermal electrons, which does not exist in Maxwellian plasmas. The population of suprathermal ions affects the critical wavenumber for instability but does not determine its emergence. Moreover, the wave frequency, growth rate, and critical wavenumber are numerically solved from the dispersion relation. The results suggest that the critical wavenumber cannot be neglected with the typical parameters of space plasmas.