Instability of Coherent Ion Acoustic Wave in a Phonon Gas

Abstract

The ion-acoustic wave propagation in a field of randomly excited low-frequency waves (phonon gas) is investigated, by obtaining the linear response function of plasmas in a turbulent phonon state. The turbulent phonons have an influence on the propagation of the coherent wave, to lead a decreased phase velocity. The coherent wave becomes unstable due to the resonant coupling with the beat wave of turbulent phonons. As the result of the instability, the coherent wave with long wavelength piles up in a plasma with turbulent phonons. The results qualitatively agree with the recent experiment.