Condensation toward large-scale fluctuations in noise-driven plasmas

Abstract

The long-time and large-scale behavior of a randomly stirred plasma due to a predominantly isotropic noise with a little flavor of a parity-nonconserving component is explored. While the isotropic noise enhances the dissipation, the directional noise is shown to make the plasma unstable. Since the dependence of the anomalous growth on the wave number k is one order lower than that of the enhanced viscous dissipation, the smaller k becomes, the less stable the modes become. For fluctuations of the largest possible scale to be unstable, the ratio of the directional noise to the isotropic noise has to be over the threshold value alpha(c) similar to In R/R, where R is the ratio Lambda/lambda of the largest wavenumber Lambda to the smallest lambda.