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Session 74 - The Quiet & Active Sun.
Display session, Friday, January 09
Exhibit Hall,

[74.05] A Two-Layer \alphaømega Dynamo Model with Dynamic Feedback on the ømega Effect

C. Roald (U. Rochester, HAO/NCAR)

I examine an interface dynamo model composed of two 1D (radially-averaged) pseudo-spherical layers, one in the convection zone and possessing an \alpha effect, and the other in the tachocline and possessing an ømega 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 ømega is provided. Extensive bifurcation diagrams are calculated for three separate values of \eta, the ratio of magnetic diffusivities of the two layers. The two-layer model does not produce a stable solar-like (dipole) butterfly diagram within the range of parameters looked at here. It does however succeed in producing distinct convection-zone and tachocline fields in a ratio proportional to \sqrt\eta, as expected for diffusion across a discontinuity in diffusivity, and the tachocline fields are generally of an acceptably large magnitude. This result seems to hold generally, across a wide range of dynamo numbers. These results are compared to the behaviour of a full 2D interface dynamo, wherein the toroidal Lorentz force can be evaluated properly.

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