Turbulent Cascades and the alpha Dynamo

TL;DR

This paper reviews the mean-field turbulence-driven dynamo model in laboratory experiments, arguing that the alpha-effect is too weak compared to the beta-effect to sustain a dynamo, supported by recent experimental measurements.

Contribution

It provides a critical analysis of the mean-field dynamo model in laboratory settings, highlighting the dominance of the beta-effect over the alpha-effect and supporting this with experimental data.

Findings

Alpha-effect is much less than beta-effect in experiments.

Mean field dynamo cannot be sustained under these conditions.

Recent measurements confirm the dominance of the beta-effect.

Abstract

The well known mean-field model of a turbulence driven dynamo is reviewed in relation to Laboratory experiments in which a turbulent cascade is created by a pair of large rotors. It is argued that in such experiments the alpha-effect, driving a dynamo field, will be much less than the dissipative beta-effect. Consequently a mean field dynamo cannot be sustained. This conclusion is supported by recent measurements of the alpha and beta effects in the Madison Dynamo Experiment.