Yoshizawa's cross-helicity effect and its quenching

TL;DR

This paper investigates the Yoshizawa cross-helicity effect in rotating turbulent fluids, examining how it influences the mean electromotive force and interacts with the alpha effect to generate large-scale magnetic fields and flows.

Contribution

It provides a detailed analysis of the Yoshizawa effect's role and its quenching in the presence of helical forcing and rotation, expanding understanding of magnetic field generation mechanisms.

Findings

Yoshizawa's contribution to EMF is reduced with alpha effect presence.

Large-scale magnetic fields can be generated in the studied system.

Large-scale flows are also produced under certain conditions.

Abstract

A central quantity in mean-field magnetohydrodynamics is the mean electromotive force EMF, which in general depends on the mean magnetic field. It may however have a part independent of the mean magnetic field. Here we study an example of a rotating conducting body of turbulent fluid with non-zero cross-helicity, in which a contribution to the EMF proportional to the angular velocity occurs (Yoshizawa 1990). If the forcing is helical, it also leads to an alpha effect, and large-scale magnetic fields can be generated. For not too rapid rotation, the field configuration is such that Yoshizawa's contribution to the EMF is considerably reduced compared to the case without alpha effect. In that case, large-scale flows are also found to be generated.