Quantum electrodynamic effects on counter-streaming instabilities in the whole \textbf{k} space

TL;DR

This paper extends the analysis of quantum electrodynamic effects on counter-streaming instabilities to all wave vector orientations, revealing that certain instabilities are weakly affected while others can have their growth rates increased or decreased by QED corrections.

Contribution

It provides a comprehensive 3D analysis of QED effects on instabilities, showing that the two-stream instability remains fundamentally 1D and that QED corrections variably influence oblique modes.

Findings

Two-stream instability remains 1D even with QED effects.

Filamentation instability's growth rate saturates independently of QED corrections.

QED effects can either reduce or increase growth rates of oblique modes.

Abstract

In a recent work [Bret, EPL \textbf{135} (2021) 35001], quantum electrodynamic (QED) effects were evaluated for the two-stream instability. It pertains to the growth of perturbations with a wave vector oriented along the flow in a collisionless counter-streaming system. Here, the analysis is extended to every possible orientation of the wave vector. The previous result for the two-stream instability is recovered, and it is proved that even within the framework of a 3D analysis, this instability remains fundamentally 1D even when accounting for QED effects. The filamentation instability, found for wave vectors normal to the flow, is weakly affected by QED corrections. As in the classical case, its growth rate saturates at large $k_\perp$. The saturation value is found independent of QED corrections. Also, the smallest unstable $k_\perp$ is independent of QED corrections. Surprisingly, unstable modes found for oblique wave vectors do \emph{not} follow the same pattern. For some, QED corrections do reduce the growth rate. But for others, the same corrections increase the growth rate instead. The possibility for QED effects to play a role in un-magnetized systems is evaluated. Pair production resulting from gamma emission by particles oscillating in the exponentially growing fields, is not accounting for.