Magnetic field oscillation in simulations of the Karlsruhe Dynamo

The dynamo effect is numerically simulated for a model of the Karlsruhe dynamo. A flow periodic in two directions and independent of the third coordinate is considered. Each periodicity cell contains four helical vortices. The novelty of the model is that it includes cylindrical walls enclosing each vortex. These walls mimic the mechanical constraints inside the Karlsruhe experiment. Periodic oscillations of the magnetic field appear in the course of which the magnetic field pattern in each vortex rotates. The oscillations already exist in the kinematic regime. It is shown that the oscillations found in our simulations and oscillations observed in the Karlsruhe dynamo experiment must be of different origin. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.