Shear Stabilization of Drift Cyclotron Instabilities in Plasma

Abstract

Shear stabilization of low‐frequency drift modes in plasma has been studied intensively in recent years, but little if any work has been done regarding the effect of shear on the drift cyclotron instabilities. The linearized Vlasov equations are used to examine the stability of electrostatic oscillations with frequency near integral multiples of the ion cyclotron frequency, propagating in an infinite inhomogeneous collisionless plasma situated in a sheared magnetic field. A normal mode analysis is employed to investigate the stability of waves propagating nearly normal to the magnetic field, and it is found that shear has a destabilizing effect although it does not alter the over‐all condition for marginal stability obtained in the uniform field case. A wave packet approach is then utilized to investigate the stability of these high‐frequency oscillations when they propagate at an arbitrary angle to the field lines. For low‐density plasma, it is shown that the drift cyclotron modes are stabilized by approximately the same shear required to stabilize the low‐frequency modes, while at high densities, a more stringent but physically realizable shear is required for stabilization