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Magnetic structures in a dynamo simulation

Published online by Cambridge University Press:  26 April 2006

A. Brandenburg ,
R. L. Jennings ,
Å. Nordlund ,
M. Rieutord ,
R. F. Stein  and
I. Tuominen
A. Brandenburg
Affiliation:
Nordita, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark
R. L. Jennings
Affiliation:
DAMTP, University of Cambridge, Silver St, Cambridge CB3 9EW, UK Present address: Shell Research BV, Postbus 60, 2280 AB Rijswijk, The Netherlands.
Å. Nordlund
Affiliation:
Theoretical Astrophysics Center, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark Copenhagen University Observatory, Øster Voldgade 3, DK-1350 Copenhagen, Denmark
M. Rieutord
Affiliation:
Observatoire Midi-Pyrénées, 14 av. E. Belin, F-31400 Toulouse, France CERFACS, 42, Avenue Coriolis, F-31057 Toulouse, France
R. F. Stein
Affiliation:
Dept. of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
I. Tuominen
Affiliation:
Observatory, PO Box 14, SF-00014 University of Helsinki, Finland Dept. of Geosciences and Astronomy, University of Oulu, PO Box 333, 90571 Oulu, Finland
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Abstract

We use three-dimensional simulations to study compressible convection in a rotating frame with magnetic fields and overshoot into surrounding stable layers. The, initially weak, magnetic field is amplified and maintained by dynamo action and becomes organized into flux tubes that are wrapped around vortex tubes. We also observe vortex buoyancy which causes upward flows in the cores of extended downdraughts. An analysis of the angles between various vector fields shows that there is a tendency for the magnetic field to be parallel or antiparallel to the vorticity vector, especially when the magnetic field is strong. The magnetic energy spectrum has a short inertial range with a slope compatible with k+1/3 during the early growth phase of the dynamo. During the saturated state the slope is compatible with k−1. A simple analysis based on various characteristic timescales and energy transfer rates highlights important qualitative ideas regarding the energy budget of hydromagnetic dynamos.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 306 , 10 January 1996 , pp. 325 - 352
Copyright
© 1996 Cambridge University Press

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