Laboratory experiments and numerical simulations on magnetic instabilities

TL;DR

This paper reviews laboratory experiments and simulations on magnetic instabilities in conducting fluids, highlighting recent experimental observations of various magnetorotational and Tayler instabilities relevant to cosmic magnetic field generation.

Contribution

It provides a comprehensive summary of experimental and numerical studies on magnetic instabilities, including new insights into their behavior and potential for future large-scale experiments.

Findings

Observation of helical and azimuthal magnetorotational instabilities

Identification of the Tayler instability in liquid metal experiments

Prospects for observing instabilities in flows with positive shear

Abstract

Magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both hydromagnetic dynamo action as well as magnetically triggered flow instabilities had been the subject of purely theoretical research. Meanwhile, however, the dynamo effect has been observed in large-scale liquid sodium experiments in Riga, Karlsruhe and Cadarache. In this paper, we summarize the results of some smaller liquid metal experiments devoted to various magnetic instabilities such as the helical and the azimuthal magnetorotational instability, the Tayler instability, and the different instabilities that appear in a magnetized spherical Couette flow. We conclude with an outlook on a large scale Tayler-Couette experiment using liquid sodium, and on the prospects to observe magnetically triggered instabilities of flows with positive shear.