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The α effect in rotating convection with sinusoidal shear
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
2010 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 402, no 3, 1458-1466 p.Article in journal (Refereed) Published
Abstract [en]

Using three-dimensional convection simulations, it is shown that a sinusoidal variation of horizontal shear leads to a kinematic α effect with a similar sinusoidal variation. The effect exists even for weak stratification and arises owing to the inhomogeneity of turbulence and the presence of impenetrable vertical boundaries. This system produces large-scale magnetic fields that also show a sinusoidal variation in the cross-stream direction. It is argued that earlier investigations overlooked these phenomena partly because of the use of horizontal averaging and also because measurements of α using an imposed field combined with long time averages give erroneous results. It is demonstrated that in such cases the actual horizontally averaged mean field becomes non-uniform. The turbulent magnetic diffusion term resulting from such non-uniform fields can then no longer be neglected and begins to balance the α effect.

Place, publisher, year, edition, pages
2010. Vol. 402, no 3, 1458-1466 p.
Keyword [en]
convection, hydrodynamics, magnetic fields, MHD, turbulence
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-50490DOI: 10.1111/j.1365-2966.2009.16004.xOAI: diva2:381572
Available from: 2010-12-28 Created: 2010-12-28 Last updated: 2016-07-01Bibliographically approved

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Brandenburg, Axel
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Department of AstronomyNordic Institute for Theoretical Physics (Nordita)
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ReferencesLink to record
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