Mean-Field Modeling of ${\alpha }^2$-Dynamo Coupled with Direct Numerical Simulations of Rigidly Rotating Convection

Abstract

The mechanism of large-scale dynamos in rigidly rotating stratified convection is explored by direct numerical simulations (DNS) in Cartesian geometry. A mean-field dynamo model is also constructed using turbulent velocity profiles consistently extracted from the corresponding DNS results. By quantitative comparison between the DNS and our mean-field model, it is demonstrated that the oscillatory ${\alpha }^2$ dynamo wave, excited and sustained in the convection zone, is responsible for large-scale magnetic activities such as cyclic polarity reversal and spatiotemporal migration. The results provide strong evidence that a nonuniformity of the $\alpha$-effect, which is a natural outcome of rotating stratified convection, can be an important prerequisite for large-scale stellar dynamos, even without the $\Omega$-effect.

arXiv commentAccepted for publication in ApJL (5pages, 5figures) [final version: normalization of Fig3 (horizontal axis) is corrected]

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• Robustness of oscillatory ${\alpha }^2$ dynamos in spherical wedges
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• Compensating Faraday depolarization by magnetic helicity in the solar corona
• Shaping core dynamos in A-type stars: The role of dipolar fossil fields
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