On the mean-field theory of the Karlsruhe dynamo experiment II. Back-reaction of the magnetic field on the fluid flow

K.-H. Rädler - M. Rheinhardt - E. Apstein - H. Fuchs

Astrophysical Institute Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Abstract
In the Forschungszentrum Karlsruhe an experiment has been built up which demonstrates a homogeneous dynamo similar to that supposed to be acting in the Earth's interior. This experiment has been discussed within the framework of mean-field dynamo theory. In a preceding paper [5] kinematic aspects of this approach to the experiment have been explained. The present paper deals with the nonlinear regime of the dynamo, that is, the regime determined by the back-reaction of the magnetic field on the fluid motion. Using again the mean-field concept a simple theory describing the behaviour of the dynamo in this regime is developed. On this basis predictions are made on the dynamic behaviour of the dynamo and in particular on the magnitude of the magnetic field and the rates of the fluid flows in the saturated states. They are compared with the experimental results. Table 1, Figs 13, Refs 11.