Signatures of an energetic charge bunch moving in a plasma

TL;DR

This paper uses particle-in-cell simulations to study how energetic charge bunches moving through plasma generate various wave structures and signatures, revealing dependencies on charge and shape, with implications for plasma heating and space debris analysis.

Contribution

It provides a detailed simulation-based analysis of wave structures and plasma signatures caused by different shaped charge bunches, highlighting new effects like ion energization and trapping.

Findings

Precursor speeds depend on total charge of the ion bunch.

Local particle trapping and energization lead to energetic ion beam-lets.

Wave structures vary with the shape of the charge source.

Abstract

A charge bunch moving in a plasma can excite a variety of linear and nonlinear waves in the form of trailing wakes, fore-wake shocks and precursor solitons. These structures can further interact with the background plasma to create secondary effects that can serve as signatures of the passage of the charge bunch. Using particle-in-cell simulations we investigate in detail the dynamics of a plasma system that is being traversed by an energetic charged ion bunch. Using two different shapes of the charge source, namely, an idealized one dimensional line source and a two dimensional thin rectangular source we examine the differences in the nature of the excited wave structures and their consequent impact on the background plasma. Our simulations reveal interesting features such as the dependence of the precursor speeds on the total charge of the ion bunch, local particle trapping, and energization of the trapped ions in various regions along the traversal path leading to the formation of energetic ion beam-lets. The collective excitations and the signatures in the ambient plasma could prove useful in practical applications such as in ion beam heating of plasmas. They can also help in analysing the trajectories of charged objects like space debris orbiting in the ionosphere.