Isolated unstable Weibel modes in unmagnetized plasmas with tunable asymmetry

TL;DR

This paper investigates isolated unstable Weibel modes in unmagnetized plasmas with tunable asymmetry, revealing that such modes can be excited with finite growth rates even as asymmetry approaches zero, for both non-relativistic and relativistic distributions.

Contribution

It demonstrates the existence of isolated Weibel modes in asymmetric plasmas and analyzes their behavior across different relativistic regimes.

Findings

Isolated modes are excited in asymmetric plasmas.

Growth rates remain finite as asymmetry tends to zero.

Modes are discrete with specific growth rates and wavenumbers.

Abstract

In this letter, an initially unmagnetized pair plasma with asymmetric velocity distributions is investigated where any unstable Weibel mode must be isolated, with discrete values for the growth rates and the unstable wavenumbers. For both a non-relativistic distribution with thermal spread and a high-relativistic two-stream distribution it is shown that isolated modes are excited and that, as the asymmetry tends to zero, the growth rate remains finite, as long as the distribution function is not precisely symmetric.