Onset of dynamo action in an axisymmetric flow.
Peffley, Cawthorne, and Lathrop [Phys. Rev. E 61, 5287 (2000)] have reported on an experiment using liquid sodium, which studies the approach toward a self-generating dynamo. Their results challenge the traditional views of kinematic dynamo theory because (i) the modes of the magnetic field with the smallest decay rates appear to be nearly axisymmetric and (ii) the observed decay rates vary spatially. This report shows how these observations can be reconciled with kinematic dynamo theory.
Tilgner
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Institute of Geophysics, University of Göttingen, Herzberger Landstrasse 180, 37075 Göttingen, Germany.