Self-consistent Mean Field theory in weakly ionized media

TL;DR

This paper develops a self-consistent mean field theory for dynamo action and turbulent diffusion in weakly ionized gases, revealing enhanced dynamo efficiency and magnetic field effects compared to fully ionized media.

Contribution

It introduces a novel mean field theory that accounts for backreaction effects in weakly ionized gases, highlighting differences from fully ionized plasma behavior.

Findings

Backreaction does not affect the beta effect in 3D.

Backreaction suppresses the alpha effect beyond a critical magnetic field strength.

Turbulent diffusion in 2D is suppressed by backreaction at high magnetic fields.

Abstract

We present a self-consistent mean field theory of the dynamo in 3D and turbulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreaction does not alter the beta effect while it suppresses the alpha effect when the strength of a mean magnetic field exceeds a critical value. These results suggest that a mean field dynamo operates much more efficiently in weakly ionized gas compared to the fully ionized gas. Furthermore, we show that in 2D, the turbulent diffusion is suppressed by back reaction when a mean magnetic field reaches the same critical strength, with the upper bound on turbulent diffusion given by its kinematic value. Astrophysical implications are discussed.