Influence of electromagnetic boundary conditions onto the onset of dynamo action in laboratory experiments.

We study the onset of dynamo action of the Riga and Karlsruhe experiments with the addition of an external wall, the electromagnetic properties of which are different from those of the fluid in motion. We consider a wall of different thickness, conductivity, and permeability. We also consider the case of a ferrofluid in motion.

Magnetic field saturation in the Riga dynamo experiment.

After the dynamo experiment in November 1999 [A. Gailitis et al., Phys.

Detection of a flow induced magnetic field eigenmode in the riga dynamo facility.

In a closed volume of molten sodium an intense single-vortex-like helical flow has been produced by an outside powered propeller. At a flow rate of 0.67 m(3)/s a slowly growing magnetic field eigenmode was detected.