Dynamics of a slow electron hole coupled to an ion-acoustic soliton

Abstract

This paper demonstrates stable embedding of an electron phase-space hole into an ion-acoustic soliton simulated using one-dimensional Particle-In-Cell simulation, forming a stable Coupled Hole-Soliton pair, which is a coupled state of a fluid soliton and a Bernstein-Green-Kruskal mode electron phase-space hole. Collision tests reveal that its collisional dynamics are a hybrid of soliton collision and electron hole merging. This hybrid state is separated from the classical free electron hole branch by a gap in their ion-frame velocities. Transition is possible from the coupled state to the free state by ion Landau damping and in the opposite direction by hole growth. Buneman instability simulation is performed, showing generation of both types of electron holes depending on the ion temperature. The results from our work can be readily applied to better understand the electrostatic solitary wave observations in space plasmas.