Whistler anisotropy instability with a cold electron component: Linear theory

Abstract

The whistler anisotropy instability is driven by an electron temperature anisotropy T/Tk > 1 where and k denote directions perpendicular and parallel, respectively, to the background magnetic field Bo. Here kinetic linear theory in a magnetized, homogeneous, collisionless plasma model is used to study this instability when the electron velocity distribution may be represented as the sum of a hot, anisotropic bi-Maxwellian and a cold, isotropic component. The critical bke, the value at which the maximum growth rate of the instability changes from propagation parallel to Bo to oblique propagation, decreases with increasing nc/ne, where nc is the cold electron density and ne is the total electron density. At parallel propagation the maximum growth rate increases with nc/ne up to nc/ne 0.8, but then diminishes with further increases of the relative cold electron density. Introduction of a cold electron component can reduce the hot electron anisotropy necessary to excite this instability by up to a factor of 2. © 2012. American Geophysical Union.