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.

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

References in corpus (5)

• Magnetic Cycles in a Convective Dynamo Simulation of a Young Solar-type Star
• Alpha effect and turbulent diffusion from convection
• Small-scale magnetic helicity losses from a mean-field dynamo
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Cited by in corpus (6)

• Differential Rotation in Magnetized and Non-magnetized Stars
• Turbulent processes and mean-field dynamo
• Analytic solution of an oscillatory migratory alpha^2 stellar dynamo
• Compensating Faraday depolarization by magnetic helicity in the solar corona
• Shaping core dynamos in A-type stars: The role of dipolar fossil fields
• Magnetorotational instability in a solar near-surface mean-field dynamo