Drift Instabilities in General Magnetic Field Configurations
Abstract
A theory of lowfrequency drift (universal) instabilities in a nonuniform collisionless plasma is developed for general magnetic field configurations including trapped particle effects, rather than the plane geometry which has previously received most attention. A type of energy principle shows that the special equilibrium distribution F(∈, μ), of interest in minimumB mirror configurations, is absolutely stable to these modes provided ∂F/∂∈ < 0 together with a second condition on ∂F/∂μ. For equilibrium distributions not of this special form, in particular for a Maxwell distribution with a density gradient, the case of axisymmetric toroidal configurations with closed poloidal field lines is considered in detail. Three unstable drift modes are found, a flutelike mode, a driftballooning mode local to the region of unfavorable curvature, and a driftuniversal mode. Stability criteria and growth rates for the modes are given. The equations also describe a recently discussed lowfrequency trappedparticle instability.
 Publication:

Physics of Fluids
 Pub Date:
 March 1968
 DOI:
 10.1063/1.1691954
 Bibcode:
 1968PhFl...11..569R