High and low frequency instabilities driven by a single electron beam in two-electron temperature space plasmas

Abstract

In an attempt to understand the excitation mechanisms of broadband electrostatic noise, beam-generated electrostatic instabilities are investigated using kinetic theory in a four-component magnetised plasma model composed of beam electrons (magnetic field-aligned), background hot and cool electrons and ions. All species are fully magnetised and considered to be Maxwellian. The dependence of the instability growth rates and real frequencies on various plasma parameters such as beam speed, particle densities and temperatures, magnetic field strength, wave propagation angle, and temperature anisotropy of the beam are examined. In this study we have found that the electron-acoustic, electron beam-resonant and ion-acoustic instabilities are excited. Our studies have focused on three velocity regimes, namely, the low (vdbz<Ch), intermediate (Ch<vdbz<2 Ch), and high velocity (vdbz>2 Ch) regimes, where vdbz (Ch) is the electron beam drift speed (thermal speed of the hot electrons). Plasma parameters from satellite measurements are used where applicable to provide realistic predictions.