Effect of self-gravitation or finite ion mass on the stability of anisotropic plasma

Abstract

The problem of stability of an unbounded anisotropic plasma characterized by different temperatures along and transverse to the magnetic field is investigated for an arbitrary direction of propagation. Chewet al (1956) equations modified to incorporate self-gravitation, finite ion Larmor radius (FLR) and Hall current are used. Uniform rotation (of an order of interest in astrophysics) is also considered. Extensive numerical treatment of the dispersion relation leads to several interesting results.

Inclusion of FLR, or Hall current or both together introduces pulsational instability for prepagation parallel to the magnetic field. The aperiodic growth rate of the ‘mirror’ instability is only slightly altered due to FLR or Hall current effects. In the absence of rotation, self-gravitation, FLR and Hall current, the growth rate decreases for the ‘mirror’ region as the direction of propagation approaches the field direction, while the ‘fire hose’ instability persists for arbitrary propagation, even in the limiting case (the ‘mirror’ limit) where the propagation is nearly transverse to the magnetic field. Uniform rotation altogether stabilizes the ‘fire hose’ instability for a sufficiently strong pressure (or temperature) anisotropy. Pulsational instability is introduced when both ratation and self-gravitation effects are present. Either FLR or Hall current depresses the growth rate of the ‘fire hose’ instability and introduces pulsational instability for the general case of arbitrary propagation. When FLR and Hall current effects are present simultaneously, the interaction terms due to these effects may be strongly destabilizing in nature for arbitrary propagation.