Oscillatory Migrating Magnetic Fields in Helical Turbulence in Spherical Domains
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 timescales 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.
- Publication:
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The Astrophysical Journal
- Pub Date:
- August 2010
- DOI:
- 10.1088/2041-8205/719/1/L1
- arXiv:
- arXiv:0901.2364
- Bibcode:
- 2010ApJ...719L...1M
- Keywords:
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- Sun: dynamo;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Consistent with the published verstion (emulateapj)