Thermal Effects on Buneman Instability: A Vlasov-Poisson Study

TL;DR

This study investigates how thermal effects influence the growth rate of Buneman instability using Vlasov-Poisson simulations, revealing significant differences from fluid and kinetic models and highlighting the role of ion density inhomogeneity.

Contribution

It provides a detailed numerical analysis of thermal effects on Buneman instability growth rates, emphasizing differences from existing models and the impact of ion density inhomogeneity.

Findings

Growth rate differs significantly from fluid and kinetic models.

Maximum growth rate depends on mass ratio but not on temperature ratio.

Ion density inhomogeneity controls electron energy transfer to plasma.

Abstract

Buneman instability has been extensively studied, and related aspects, namely anomalous resistivity, have been explored in detail using analytical theory as well as numerical simulations based on Particle-in-Cell and Vlasov solvers. Most numerical studies have focused on understanding the nonlinear evolution of the instability. In the present study, the growth rate of the Buneman instability in the presence of thermal effects of the constituent species (i.e., ions and electrons) is investigated. It is observed that the growth rate differs significantly from that obtained using fluid models (both cold and warm) as well as from linearized kinetic models. While the well-known result of $(m/M)^{1/3}$ dependence of the maximum growth rate is recovered, it is shown that the maximum growth rate is essentially independent of the temperature ratio of the constituent species. It is further demonstrated numerically that the amplitude of ion density inhomogeneity self-consistently controls the transfer of electron beam energy into the bulk plasma temperature. In particular, as one moves from the cold to the warm plasma limit, the decrease in ion density inhomogeneity reduces the generation of sidebands and thus lowers the transfer efficiency.