Dynamo action and magnetorotational instability: cosmic magnetism in the liquid metal lab

It is widely known that cosmic magnetic fields are produced by the hydromagnetic dynamo effect. Yet it is less well known that cosmic magnetic fields play an active role in cosmic structure formation by means of the magnetorotational instability (MRI). The last ten years have seen tremendous efforts in studying both effects in the laboratory. In 1999, magnetic field self-excitation was observed nearly simultaneously in the liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment, although with the help of iron propellers. The helical MRI was recently studied in the ''Potsdam Rossendorf Magnetic Instability Experiment'' (PROMISE), and an improved version of this experiment (PROMISE 2) has provided sharper transitions between stable and unstable regimes. In the talk, the history of dynamo and MRI experiments is delineated, and some interesting directions of future work are discussed.