http://arxiv.org/abs/1803.08692
We discuss a solar dynamo model of the Tayler-Spruit type whose Omega-effect is traditionally produced by a solar-like differential rotation but whose alpha-effect is assumed to be periodically modulated by planetary tidal forcing. This resonance-like effect has its rationale in the tendency of the current-driven Tayler instability to undergo intrinsic helicity oscillations which, in turn, can be synchronized by periodic tidal perturbations. Specifically, we focus on the 11.07 years periodicity of the alignment of the tidally dominant planets Venus, Earth, and Jupiter. In the framework of a simple one-dimensional numerical model we prove the subcritical nature of this Tayler-Spruit type dynamo. The typically emerging dynamo modes are dipolar fields, oscillating with a 22.14 years period, but also quadrupolar fields pulsating with a 11.07 years period. Transitions between these field topologies are reminiscent of the observed behaviour during the Maunder minimum. Further interesting features of the model are the emergence of mid-term fluctuations, with periods in the order of one year, and the intermittent appearance of reversed helicities in both hemispheres. With minor model modifications, the correct direction of the butterfly diagram comes out as a robust feature, too.
F. Stefani, A. Giesecke and T. Weier
Mon, 26 Mar 18
34/43
Comments: 25 pages, 17 figures
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