Mean-field dynamo in partially ionized plasmas-I

TL;DR

This paper explores how nonideal effects like Hall and ambipolar diffusion influence the kinematic dynamo process in partially ionized turbulent plasmas, revealing significant modifications to classical dynamo theory.

Contribution

It introduces the effects of Hall and ambipolar diffusion into the kinematic dynamo framework for partially ionized plasmas, highlighting their impact on the alpha effect and turbulent diffusion.

Findings

Hall effect can enhance or suppress dynamo action

Ambipolar diffusion introduces a magnetic field-dependent alpha effect

New correlations emerge from charged-neutral fluid interactions

Abstract

There are several astrophysical situations where one needs to study the dynamics of magnetic flux in partially ionized turbulent plasmas. In a partially ionized plasma the magnetic induction is subjected to the ambipolar diffusion and the Hall effect in addition to the usual resistive dissipation. In this paper we initiate the study of the kinematic dynamo in a partially ionized turbulent plasma. The Hall effect arises from the treatment of the electrons and the ions as two separate fluids and the ambipolar diffusion due to the inclusion of neutrals as the third fluid. It is shown that these nonideal effects modify the so called $\alpha$ effect and the turbulent diffusion coefficient $\beta$ in a rather substantial way. The Hall effect may enhance or quench the dynamo action altogether. The ambipolar diffusion brings in an $\alpha$ which depends on the mean magnetic field. The new correlations embodying the coupling of the charged fluids and the neutral fluid appear in a decisive manner. The turbulence is necessarily magnetohydrodynamic with new spatial and time scales. The nature of the new correlations is demonstrated by taking the Alfv\'enic turbulence as an example.