Closure tests for mean field magnetohydrodynamics using a self consistent reduced model

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dc.creatorPipin, V. V.
dc.creatorProctor, M. R. E.
dc.date2007-12-28
dc.date.accessioned2026-07-07T12:33:35Z
dc.date.available2026-07-07T12:33:35Z
dc.descriptionThe mean electromotive force and alpha effect are computed for a forced turbulent flow using a simple nonlinear dynamical model. The results are used to check the applicability of two basic analytic ansatze of mean-field magnetohydrodynamics - the second order correlation approximation (SOCA) and the tau approximation. In the numerical simulations the effective Reynolds number Re is 2-20, while the magnetic Prandtl number varies from 0.1 to $10^{7}$. We present evidence that the $τ$ approximation may be appropriate in dynamical regimes where there is a small-scale dynamo. Catastrophic quenching of the $α$ effect is found for high $P_{m}$. Our results indicate that for high $P_{m}$ SOCA gives a very large value of the $α$ coefficient compared with the ``exact'' solution. The discrepancy depends on the properties of the random force that drives the flow, with a larger difference occuring for $δ$-correlated force compared with that for a steady random force.
dc.descriptionsubmitted to MNRAS
dc.identifierhttps://arxiv.org/abs/0712.4311
dc.identifierhttp://arxiv.org/abs/0712.4311
dc.identifierMNRAS, V.388, Issue 1, pp. 367-374, 2008
dc.identifierdoi:10.1111/j.1365-2966.2008.13396.x
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/217179
dc.subjectAstrophysics
dc.titleClosure tests for mean field magnetohydrodynamics using a self consistent reduced model
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