A wavenumber-in-cell simulation of weak Langmuir turbulence

Abstract

A wavenumber-in-cell code was developed for simulation of a model proposed by Vedenov et al., for studying weak Langmuir turbulence. The model uses a WKB-approach for analyzing the Langmuir wavefield, which is described by a superposition of many pseudoparticles or plasmons. Theoretical results for damping of ion acoustic waves caused by resonant interaction of Langmuir waves with group velocity around the sound speed were confirmed. Simulations, with damping mechanisms included in the ion sound dynamics, demonstrated formation of localized cavities of intense wideband, self-trapped, Langmuir wavefields. Analytic solutions for these cavities are obtained in terms of trapped plasmons, without contributions from propagating waves. The interaction and coalescence of two cavities have features in common with the similar process for phase-space vortices. The damping of ion acoustic waves gives rise to a deceleration of the cavitons. Initial conditions with either uniform distribution of the high frequency waves, or alternatively with localized wave bursts, were considered.