Driven ion acoustic wave nonlinearities in superthermal electron plasmas

Abstract

The fluid nonlinearities of driven ion acoustic waves (IAWs) in superthermal electron plasmas are investigated by fluid theory and one-dimensional fluid simulation. A kappa velocity distribution function is used to model superthermal electrons. Under the condition of small wave amplitudes, simulation results are presented to verify the conclusion of fluid theory, showing that the presence of superthermal electrons leads to stronger harmonic generation and larger nonlinear frequency shifts of IAWs. In addition, the growth rate and threshold of the IAW decay instability from simulations are well predicted by a simple three-wave fluid theory. It is shown that the nonlinear frequency shift has a significant effect on IAW decay, and for a larger population of superthermal electrons, the IAW decay has a smaller onset threshold and threshold range.