Vlasov simulation of Langmuir decay instability

Abstract

A parametric decay process of beam-generated Langmuir waves is examined by a one-dimensional Vlasov code simulation in the open system. It is confirmed that pump Langmuir waves decay into backscattered Langmuir and ion acoustic waves when the wave energy is higher than the thermal energy of background electrons. In the present Vlasov simulation, a large-amplitude pump Langmuir wave is excited by an electron beam. Then a backscattered Langmuir wave and a forward ion acoustic wave are excited by the parametric decay instability. When the wave energy of the backscattered Langmuir waves is also higher than the thermal energy of background electrons, backward ion acoustic waves are also excited. As a result, the wavenumber spectra of Langmuir and ion acoustic waves are broadened in both forward and backward directions, suggesting possible multiple parametric decay processes of Langmuir waves in a beam-plasma system.