Analysis of the Effect of a Mean Velocity Field on Mean Field Dynamo

Abstract

We study semi-analytically and in a consistent manner, the generation of a mean velocity field $\bar{\mathbf{U}}$ by helical MHD turbulence, and the effect that this field can have on a Mean Field Dynamo. Assuming a prescribed, maximally helical small scale velocity field, we show that large scale flows can be generated in MHD turbulent flows, via small scale Lorentz force. These flows back-react on the mean electromotive force of a Mean Field Dynamo through new terms, leaving the original $\alpha$ and $\beta$ terms explicitly unmodified. Cross-helicity plays the key role in interconnecting all the effects. In the minimal $\tau$ closure that we chose to work with, the effects are stronger for large relaxation times.

9 pages, 10 figures, accepted for publication in MNRAS

References in corpus (2)

• Minimal tau approximation and simulations of the alpha effect
• On the mean field dynamo with Hall effect

Cited by in corpus (1)

• The role of the Yoshizawa effect in the Archontis dynamo