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Axisymmetric dynamo action produced by differential rotation, with anisotropic electrical conductivity and anisotropic magnetic permeability

Published online by Cambridge University Press:  08 February 2021

Franck Plunian Open the ORCID record for Franck Plunian [Opens in a new window]  and
Thierry Alboussière Open the ORCID record for Thierry Alboussière [Opens in a new window]
Franck Plunian*
Affiliation:
Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000Grenoble, France
Thierry Alboussière
Affiliation:
Univ. Lyon, Univ. Lyon 1, ENSL, CNRS, LGL-TPE, F-69622, Villeurbanne, France
*
†Email address for correspondence: Franck.Plunian@univ-grenoble-alpes.fr
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Abstract

The effect on dynamo action of an anisotropic electrical conductivity conjugated to an anisotropic magnetic permeability is considered. Not only is the dynamo fully axisymmetric, but it requires only a simple differential rotation, which twice challenges the well-established dynamo theory. Stability analysis is conducted entirely analytically, leading to an explicit expression of the dynamo threshold. The results show a competition between the anisotropy of electrical conductivity and that of magnetic permeability, the dynamo effect becoming impossible if the two anisotropies are identical. For isotropic electrical conductivity, Cowling's neutral point argument does imply the absence of an azimuthal component of current density, but does not prevent the dynamo effect as long as the magnetic permeability is anisotropic.

Keywords

plasma instabilities
Type
Research Article
Information
Journal of Plasma Physics , Volume 87 , Issue 1 , February 2021 , 905870110
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Copyright
Copyright © The Author(s), 2021. Published by Cambridge University Press

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