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arXiv · 0901.2364

Oscillatory migrating magnetic fields in helical turbulence in spherical domains

Dhrubaditya Mitra·Reza Tavakol·Petri J. Käpylä·Axel Brandenburg
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Abstract

We present direct numerical simulations of the equations of compressible magnetohydrodynamics in a wedge-shaped spherical shell, without shear, but with random helical forcing which has negative (positive) helicity in the northern (southern) hemisphere. We find a large-scale magnetic field that is nearly uniform in the azimuthal direction and approximately antisymmetric about the equator. Furthermore, the large-scale field in each hemisphere oscillates on nearly dynamical time scales with reversals of polarity and equatorward migration. Corresponding mean-field models also show similar migratory oscillations with a frequency that is nearly independent of the magnetic Reynolds number. This mechanism may be relevant for understanding equatorward migration seen in the solar dynamo.

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Dhrubaditya Mitra, Reza Tavakol, Petri J. Käpylä, Axel Brandenburg. 2010-07-17. Oscillatory migrating magnetic fields in helical turbulence in spherical domains. https://doi.org/10.1088/2041-8205%2F719%2F1%2Fl1

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