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Paper: Small-scale Dynamo Action in Compressible Convection
Volume: 429, Numerical Modeling of Space Plasma Flows, Astronum-2009
Page: 181
Authors: Bushby, P. J.; Proctor, M. R. E.; Weiss, N. O.
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 near the upper surface of the computational domain. This partial evacuation has a profound influence upon the efficiency of the (explicit) numerical scheme that is used in these calculations. These results can be related (in a qualitative sense) to recent observations of magnetic fields in the quiet Sun.
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