# Simulation study of overtaking of ion-acoustic solitons in the fully kinetic regime

## TL;DR

This study uses fully kinetic simulations to analyze ion-acoustic soliton overtaking collisions, revealing their stability, long lifespan, and detailed kinetic interactions, including electron trapping effects and electron hole dynamics.

## Contribution

It provides the first comprehensive kinetic analysis of ion-acoustic soliton collisions, demonstrating their stability and detailed electron trapping interactions during overtaking events.

## Key findings

- Solitons have a long lifespan despite electron trapping effects.
- Solitons remain stable during overtaking collisions with different shapes.
- Electron populations are exchanged between solitons during collisions.

## Abstract

The overtaking collisions of ion-acoustic solitons (IASs) in presence of trapping effects of electrons are studied based on a fully kinetic simulation approach. The method is able to provide all the kinetic details of the process alongside the fluid-level quantities self consistently. Solitons are produced naturally by utilizing the chain formation phenomenon, then are arranged in a new simulation box to test different scenarios of overtaking collisions. Three achievements are reported here. Firstly, simulations prove the long-time life span of the ion-acoustic solitons in the presence of trapping effect of electrons (kinetic effects), which serves as the benchmark of the simulation code. Secondly, their stability against overtaking mutual collisions is established by creating collisions between solitons with different number and shapes of trapped electrons, i.e. different trapping parameter. Finally, details of solitons during collisions for both ions and electrons are provided on both fluid and kinetic levels. These results show that on the kinetic level, trapped electron population accompanying each of the solitons are exchanged between the solitons during the collision. Furthermore, the behavior of electron holes accompanying solitons contradicts the theory about the electron holes interaction developed based on kinetic theory. They also show behaviors much different from other electron holes witnessed in processes such as nonlinear Landau damping (Bernstein-Greene-Kruskal -BGK- modes) or beam-plasma interaction (like two-beam instability).