Weibel instability beyond bi-Maxwellian anisotropy

TL;DR

This paper explores how non-Maxwellian velocity distributions influence the Weibel instability, revealing that the shape of the distribution affects the instability's growth and magnetic field generation.

Contribution

It demonstrates that non-Maxwellian distributions alter the direction of maximum growth rate wavevectors and suggests the need for more detailed analysis beyond temperature anisotropy.

Findings

Maximum growth rate wavevector direction depends on distribution shape

Non-Maxwellian distributions can significantly modify magnetic field generation

Standard temperature anisotropy metrics may be insufficient for characterization

Abstract

The shape of the anisotropic velocity distribution function, beyond the realm of strict Maxwellians can play a significant role in determining the evolution of the Weibel instability dictating the dynamics of self-generated magnetic fields. For non-Maxwellian distribution functions, we show that the direction of the maximum growth rate wavevector changes with shape. We investigate different laser-plasma interaction model distributions which show that their Weibel generated magnetic fields may require closer scrutiny beyond the second moment (temperature) anisotropy ratio characterization.