Nonlinear small-scale dynamos at low magnetic Prandtl numbers |
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Axel Brandenburg Submitted: 2012-07-07 13:12
Saturated small-scale dynamo solutions driven by isotropic non-helical turbulence are presented at low magnetic Prandtl numbers Pm down to 0.01. For Pm < 0.1, most of the energy is dissipated via Joule heat and, in agreement with earlier results for helical large-scale dynamos, kinetic energy dissipation is shown to diminish proportional to Pm1/2 down to values of 0.1. In agreement with earlier work, there is, in addition to a short Golitsyn k-11/3 spectrum near the resistive scale also some evidence for a short k-1 spectrum on larger scales. The rms magnetic field strength of the small-scale dynamo is found to depend only weakly on the value of Pm and decreases by about a factor of 2 as Pm is decreased from 1 to 0.01. The possibility of dynamo action at Pm=0.1 in the nonlinear regime is argued to be a consequence of a suppression of the bottleneck seen in the kinetic energy spectrum in the absence of a dynamo and, more generally, a suppression of kinetic energy near the dissipation wavenumber.
Authors: Axel Brandenburg
Projects: None
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Publication Status: Astrophys. J. 741, 92 (2011)
Last Modified: 2012-07-07 14:47
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