Parametric excitation of electron acoustic wave by Langmuir wave in the Earth’s inner magnetospheres

Abstract

A kinetic model for the parametric decay of Langmuir wave (LW) into sideband LW and electron acoustic wave (EAW) in plasmas containing hot and cold electrons is developed. The parametric instability for LW decaying into EAW in the Earth’s inner magnetosphere is numerically analyzed. The maximum growth rate and the range of wavenumber for the existence of parametric instability increase with the increase of pump wave strength and hot electron concentration. The frequency of excited EAW corresponding to the maximum grow rate goes up as the enhancement of pump wave strength, but lowers as the reduction of hot electron concentration. The frequencies of excited EAW are comparable to the observed frequencies of whistler wave in the inner magnetosphere. The growth rate will be about a few tens per second when pump LWs is strong enough. The results obtained may be helpful for the explanation of the observed electrostatic field spectrum in the inner magnetosphere.