Beam-Plasma Dynamics in Finite-Length, Collisionless Inhomogeneous Systems

TL;DR

This paper explores how finite system length and inhomogeneity influence beam-plasma instabilities, revealing boundary effects and kinetic resonances through numerical simulations of collisionless plasmas.

Contribution

It provides new insights into the effects of finite length and inhomogeneity on beam-plasma dynamics, combining PIC simulations with kinetic analysis.

Findings

Steady ion flow modifies ion sound waves via boundary reflections.

Boundary effects can induce hydrodynamic instabilities.

Kinetic resonances significantly contribute to beam-driven ion sound instability.

Abstract

This study investigates the streaming instability triggered by ion motion in a plasma system that is finite in length, collisionless, and inhomogeneous. Employing numerical simulations using Particle-In-Cell (PIC) techniques and kinetic equations, the study examines how inhomogeneity emerges from integrating a cold ion beam with a background plasma within a confined system. The findings suggest that steady ion flow can modify ion sound waves through acoustic reflections from system boundaries, leading to instability. Such phenomena are known to be a hydrodynamic effect. However, there are also signatures of the beam-driven ion sound instability where kinetic resonances play a pivotal role. The main objective is to understand the impact of a finite-length system on beam-plasma instability and to identify the wave modes supported in such configurations.