A two-layer αω-dynamo model with dynamic feedback on the ω-effect |
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| Authors: | Colin B Roald |
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| Institution: | Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA,;High Altitude Observatory, National Center for Atmospheric Research, Box 3000, Boulder, CO 80307-3000, USA |
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| Abstract: | In an attempt to produce a simple representation of an interface dynamo, I examine a dynamo model composed of two one-dimensional (radially averaged) pseudo-spherical layers, one in the convection zone and possessing an α-effect, and the other in the tachocline and possessing an ω-effect. The two layers communicate by means of an analogue of Newton's law of cooling, and a dynamical back-reaction of the magnetic field on ω is provided. Extensive bifurcation diagrams are calculated for three separate values of η, the ratio of magnetic diffusivities of the two layers. I find recognizable similarities to, but also dramatic differences from, the comparable one-layer model examined by Roald &38; Thomas. In particular, the solar-like dynamo mode found previously is no longer stable in the two-layer version; in its place there is a sequence of periodic, quasi-periodic and chaotic modes probably created in a homoclinic bifurcation. These differences are important enough to provide support for the view that the solar dynamo cannot be meaningfully modelled in one dimension. |
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| Keywords: | chaos MHD Sun: activity Sun: magnetic fields stars: magnetic fields |
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