On collisions driven negative energy waves and Weibel instability of a relativistic electron beam in a quasi-neutral plasma

TL;DR

This paper introduces a new quasi-neutral model for the Weibel instability in relativistic electron beams within resistive plasmas, revealing negative energy waves and demonstrating the persistence of instability even in collisionless conditions through PIC simulations.

Contribution

It develops a novel quasi-neutral model that accounts for negative energy waves and demonstrates the sustained Weibel instability in collisionless plasmas via simulations.

Findings

Identification of negative energy magneto-sound waves in finite-temperature beams

Persistence of Weibel instability in collisionless plasma in three dimensions

Role of two-stream instability in causing anomalous plasma resistivity

Abstract

A new quasi-neutral model describing the Weibel instability of a high-current relativistic beam propagating through a resistive plasma is developed. It treats beam electrons as kinetic particles, and ambient plasma as a non-relativistic fluid. For a finite-temperature beam, a new class of negative energy magneto-sound waves is identified, which can possess negative energy. Their growth due to collisional dissipation in the cold return current destabilizes the beam-plasma system even for high beam temperatures. We perform detailed two- and three-dimensional particle-in-cell (PIC) simulations of the thermal beam and collisional plasma. It is shown that in three dimensions, the Weibel instability persists even for physically collisionless background plasma. The anomalous plasma resistivity is then caused by the two-stream instability.