Turbulence-induced transport dynamo mechanism

TL;DR

This paper reviews the transport dynamo mechanism where turbulence-induced diffusion generates magnetic fields, emphasizing its slow timescale and dependence on density inhomogeneity, with turbulence greatly enhancing diffusion.

Contribution

It provides a detailed review of the turbulence-induced transport dynamo mechanism, highlighting its unique features and the role of turbulence in magnetic field generation.

Findings

Turbulence significantly enhances cross-field diffusion.

Magnetic field generation occurs on slow timescales due to diffusion.

The mechanism is effective primarily with density inhomogeneity.

Abstract

The transport dynamo mechanism, which describes the magnetic field generation by diffusion flow is reviewed. In this mechanism, the cross-field transport caused by the random motion of fluid breaks the frozen-flux approximation, and the resulting cross-field diffusion that can generate the magnetic field. Turbulence can play an important role in inducing such random motion. Compared to the conventional dynamo mechanism, this transport mechanism has several special features that the field generation can occur on a very slow time scale because the mechanism is mediated by diffusion and that this mechanism is practically meaningful only when there is density inhomogeneity. Turbulence can significantly enhance cross-field diffusion far beyond collisional transport. The physical meanings of the diffusion-generated magnetic fields are discussed in detail.