Liquid metal experiments on astrophysical magnetic fields

Cosmic magnetic fields are ubiquitous phenomena that are observed on all scales, from planets and stars to galaxies and clusters of galaxies. The origin of these fields involves the formation of electrical currents by means of complex flows of conducting fluids or plasmas. Magnetic fields may also be important for cosmic structure formation by destabilizing rotational flows that would otherwise be hydrodynamically stable with the magnetorotational instability (MRI)in accretions disks as the most prominent example. Both processes, magnetic field generation (the so called dynamo effect), and magnetic field induced instabilities have also been observed in experiments, which, however, require considerable technical efforts due to the significantly smaller scales available in the laboratory.

In my talk I will briefly summarize the essential outcome of past, present, and future liquid metal experiments on magnetohydrodynamic dynamos and instabilities. The focus will be on the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies), a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics conducted at Helmholtz-Zentrum Dresden-Rossendorf. Most ambitious experiments will be a large-scale precession driven dynamo experiment and a combined set-up for investigating different versions of the magnetorotational instability and the Tayler instability, a current driven kink-like instability. For both experiments, recent results of preparatory studies are presented, and the scientific prospects for the final set-ups are delineated.