Computer simulation of a Cerenkov interaction between obliquely propagating whistler mode waves and an electron beam

Abstract

A Cerenkov type wave-particle interaction between an obliquely propagating whistler mode wave and an electron beam has been investigated by a computer simulation experiment. A one-dimensional electromagnetic simulation code which is especially designed to deal with the obliquely propagating wave is used. Two cases of such a wave-particle interaction have been investigated. In the first case no initial wave is assumed to exist in the simulation model space. In the second case, an obliquely propagating whistler mode wave with a finite amplitude is initially assumed to exist. In both cases after linear wave growth, nonlinear saturation and amplitude oscillation are observed. This nonlinear behavior of the interaction can be interpreted by particle trapping in the wave potential well just as in the case of longitudinal electrostatic waves. Waves excited by Cerenkov radiation from the beam electrons develop as a coherent wave due to the instability and propagate in the magnetized plasma. By the oblique beam-plasma interaction, electromagnetic waves can be amplified. Amplification of the waves observed by this computer simulation may be closely related to VLF hiss noise occurring in the earth’s magnetosphere.