Large-scale dynamos in turbulent convection with shear

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dc.creatorKäpylä, P. J.
dc.creatorKorpi, M. J.
dc.creatorBrandenburg, A.
dc.date2008-06-03
dc.date2008-10-06
dc.date.accessioned2026-07-07T10:16:44Z
dc.date.available2026-07-07T10:16:44Z
dc.description(abridged) Aims: Three-dimensional numerical simulations of penetrative compressible convection with uniform horizontal shear are used to study dynamo action and the generation of large-scale magnetic fields. Methods: We consider cases where the magnetic Reynolds number is either marginal or moderately supercritical with respect to small-scale dynamo action in the absence of shear and rotation. The effects of magnetic helicity fluxes are studied by comparing results for the magnetic field with open and closed boundaries. Results: Without shear no large-scale dynamos are found even if the ingredients necessary for the alpha-effect (rotation and stratification) are present in the system. When uniform horizontal shear is added, a large-scale magnetic field develops, provided the boundaries are open. In this case the mean magnetic field contains a significant fraction of the total field. For those runs where the magnetic Reynolds number is between 60 and 250, small-scale dynamo is expected to be excited, but the field distribution is found to be similar to cases with smaller magnetic Reynolds number where the small-scale dynamo is not excited. In the case of closed (perfectly conducting) boundaries, magnetic helicity fluxes are suppressed and no large-scale fields are found. Similarly, poor large-scale field development is seen when vertical shear is used in combination with periodic boundary conditions in the horizontal directions. If, however, open (normal-field) boundary conditions are used in the x-direction, a large-scale field develops. These results support the notion that shear not only helps to generate the field, but it also plays a crucial role in driving magnetic helicity fluxes out of the system along the isocontours of shear, thereby allowing efficient dynamo action.
dc.description10 pages, 19 figures, accepted for publication in Astron. Astrophys
dc.identifierhttps://arxiv.org/abs/0806.0375
dc.identifierhttp://arxiv.org/abs/0806.0375
dc.identifierAstron. Astrophys. 491, 353-362 (2008)
dc.identifierdoi:10.1051/0004-6361:200810307
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/173612
dc.subjectAstrophysics
dc.titleLarge-scale dynamos in turbulent convection with shear
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