Filamentation instability of long Alfvén waves in warm collisionless plasmas

Abstract

A criterion for filamentation instability of a circularly polarized Alfvén wave train propagating along a strong ambient field in a collisionless plasma is obtained from a transverse modulational analysis of a generalized kinetic derivative nonlinear Schrödinger equation. This equation, which retains Landau damping, results from the Vlasov–Maxwell equations via a long-wave reductive perturbative expansion. For bi-Maxwellian equilibrium distribution functions, it is shown that a moderate anisotropy of the electron temperature and/or a moderate ratio of the electron to ion temperatures can significantly broaden the existence range of this instability, making its occurrence possible in small-β plasmas.