A note on the Weibel instability and thermal fluctuations

TL;DR

This paper recalculates the thermal fluctuation level of the Weibel instability, demonstrating that the infrared catastrophe does not occur and describing how fields penetrate and form structures within plasma.

Contribution

It provides a revised analysis of the Weibel instability's thermal fluctuations, challenging previous notions of divergence at long wavelengths.

Findings

Infrared catastrophe of the Weibel instability is avoided.

Thermal fluctuations are limited by minimal stable anisotropy.

Weibel fields penetrate only one skin depth into plasma.

Abstract

The thermal fluctuation level of the Weibel instability is recalculated. It is shown that the divergence of the fluctuations at long wavelengths, i.e. the Weibel infrared catastrophe, never occurs. At large wavelengths the thermal fluctuation level is terminated by the presence of even the smallest available stable thermal anisotropy. Weibel fields penetrate only one skin depth into the plasma. When excited inside, they cause layers of antiparallel fields of skin depth width and vortices which may be subject to reconnection.