Hydrodynamic and numerical modeling of a spherical homogeneous dynamo experiment

C. B. Forest - R. A. Bayliss - R. D. Kendrick - M. D. Nornberg - R. O'Connell - E. J. Spence

Department of Physics, University of Wisconsin, Madison, Wisconsin 53711, USA

Abstract
A spherical, homogeneous kinematic dynamo is investigated both experimentally and theoretically at the University of Wisconsin. Previous kinematic dynamo studies are extended by optimizations in flow geometries which lower the critical magnetic Reynolds number for self-excitation. The stretch-twist-fold dynamo model is used to describe the physical mechanism for magnetic field generation in a simple two-vortex flow. The possibility of producing such flows in liquid sodium is studied in a water experiment. Mechanically driven flows generated by rotating impellers enclosed in a spherical vessel are characterized by measurements of the velocity field using Laser Doppler Velocimetry. The mean flows studied are predicted to lead to self-excitation of magnetic eigenmodes. The sodium dynamo experiment is described. Table 1, Figs 9, Refs 14.