A Two-dimensional Numerical Study of Ion-Acoustic Turbulence

TL;DR

This study uses 2D Vlasov-Poisson simulations to explore the evolution of ion-acoustic turbulence in collisionless plasma, revealing transient behavior and the emergence of electron-acoustic waves due to particle distribution modifications.

Contribution

It provides a detailed nonlinear analysis of ion-acoustic turbulence evolution, emphasizing the transient nature of anomalous resistivity and the role of particle heating and wave interactions.

Findings

No steady saturated state is reached; ion heating suppresses the instability.

Ion-acoustic turbulence causes transient anomalous resistivity.

Electron-acoustic waves are triggered during nonlinear evolution.

Abstract

We investigate the linear and nonlinear evolution of the ion-acoustic instability in a collisionless plasma via two-dimensional (2D2V) Vlasov-Poisson numerical simulations. We initialize the system in a stable state and gradually drive it towards instability with an imposed, weak external electric field, thus avoiding super-critical initial conditions that are physically unrealizable. The nonlinear evolution of ion-acoustic turbulence (IAT) is characterized in detail, including the particles' distribution functions, particle heating, (two-dimensional) wave spectrum, and the resulting anomalous resistivity. An important result is that no steady saturated nonlinear state is ever reached in our simulations: strong ion heating suppresses the instability, which implies that the anomalous resistivity associated with IAT is transient and short-lived. Electron-acoustic waves (EAWs) are triggered during the late nonlinear evolution of the system, caused by strong modifications to the particle distribution induced by IAT.