Laboratory experiments and numerical simulations on magnetic instabilities

摘要

Magnetic fields of planets, stars and galaxies are generated byself-excitation in moving electrically conducting fluids. Once produced,magnetic fields can play an active role in cosmic structure formation bydestabilizing rotational flows that would be otherwise hydrodynamically stable.For a long time, both hydromagnetic dynamo action as well as magneticallytriggered flow instabilities had been the subject of purely theoreticalresearch. Meanwhile, however, the dynamo effect has been observed inlarge-scale liquid sodium experiments in Riga, Karlsruhe and Cadarache. In thispaper, we summarize the results of some smaller liquid metal experimentsdevoted to various magnetic instabilities such as the helical and the azimuthalmagnetorotational instability, the Tayler instability, and the differentinstabilities that appear in a magnetized spherical Couette flow. We concludewith an outlook on a large scale Tayler-Couette experiment using liquid sodium,and on the prospects to observe magnetically triggered instabilities of flowswith positive shear.