Electromagnetic cyclotron-loss-cone instability associated with weakly relativistic electrons

Abstract

The amplification of fast extraordinary mode waves with frequencies very close to the electron cyclotron frequency is investigated for a plasma which consists of a weakly relativistic electron component with a loss-cone type distribution and a cold background electron component. The basic mechanism of the amplification is attributed to a relativistic cyclotron resonance between the wave and the energetic electrons. The method employed in the present analysis enables us to solve the dispersion relation in a self-consistent manner for arbitrary ratio of the densities of the energetic and background electrons. It is found that the maximum growth rates occur at certain values of ω 2 pe /Ω 2 e and the angular dependence of the growth rate is sensitive to the ratios ω 2 pe /Ω 2 e and n e / n b . Here ω pe and Ω e are the electron plasma frequency and the electron cyclotron frequency, respectively, and n e and n b denote the number densities of the energetic and background electrons, respectively.