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Small-scale dynamo action in compressible convection

Lookup NU author(s): Dr Paul Bushby

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Abstract

Motivated by observations of magnetic fields at the surface of the Sun, we consider direct numerical simulations of dynamo action in highly-stratified, three-dimensional compressible convection. Whether or not a convective flow can drive a dynamo depends crucially upon the magnetic Reynolds number. If this parameter is large enough that the inductive effects of the fluid motions outweigh the dissipative effects of magnetic diffusion, then dynamo action can occur. Simulating convection with a Reynolds number of approximately 150, we find that it is possible to excite a dynamo with computationally accessible values of the magnetic Reynolds number. In the kinematic regime, the growth rate of the dynamo has a logarithmic dependence upon the magnetic Reynolds number. Following these dynamos into the nonlinear regime, we find that intense, partially-evacuated concentrations of vertical magnetic flux form nearthe upper surface of the computational domain. This partial evacuationhas a profound influence upon the efficiency of the(explicit) numerical scheme that is used in these calculations. Theseresults can be related (in a qualitative sense) to recentobservations of magnetic fields in the quiet Sun.


Publication metadata

Author(s): Bushby PJ, Proctor MRE, Weiss NO

Editor(s): Pogorelov, N.V., Audit, E., Zank, G.P.

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: Numerical Modeling of Space Plasma Flows (ASTRONUM)

Year of Conference: 2010

Pages: 181-186

Date deposited: 06/01/2012

Publisher: ASPCS: San Francisco

Library holdings: Search Newcastle University Library for this item

Series Title: Astronomical Society of the Pacific Conference Series

ISBN: 9781583817384


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