Impact of super-Gaussian electron distribution on driven ion acoustic wave fluid nonlinear evolution

Abstract

In laser-produced plasmas, the electron distribution function (EDF) driven by inverse bremsstrahlung heating tends to form a super-Gaussian distribution, which significantly influences ion acoustic waves (IAWs). In this study, the effect of the super-Gaussian EDF on driven IAWs is investigated using one-dimensional fluid simulations. Distinct behaviors are observed in the nonlinear evolution of driven IAWs in such plasmas. First, under the condition of small wave amplitudes, weaker harmonic generation and smaller nonlinear frequency shifts of IAWs are observed compared to the Maxwellian EDF case, consistent with nonlinear fluid theory. Additionally, for both the Maxwellian and super-Gaussian EDF cases, three-wave fluid theory and simulations show that due to the significant nonlinear frequency shift, the occurrence of two-ion decay requires a positive frequency mismatch between the driven frequency and the IAW linear frequency. However, for the super-Gaussian EDF case, a smaller frequency mismatch is required. Finally, turbulence and multi-soliton generation induced by IAW decay are also discussed.