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Spoke-like differential rotation in a convective dynamo with a coronal envelope
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.ORCID iD: 0000-0002-7304-021X
2013 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 778, no 2, 141- p.Article in journal (Refereed) Published
Abstract [en]

We report on the results of four convective dynamo simulations with an outer coronal layer. The magnetic field is self-consistently generated by the convective motions beneath the surface. Above the convection zone, we include a polytropic layer that extends to 1.6 solar radii. The temperature increases in this region to approximate to 8 times the value at the surface, corresponding to approximate to 1.2 times the value at the bottom of the spherical shell. We associate this region with the solar corona. We find solar-like differential rotation with radial contours of constant rotation rate, together with a near-surface shear layer. This non-cylindrical rotation profile is caused by a non-zero latitudinal entropy gradient that offsets the Taylor-Proudman balance through the baroclinic term. The meridional circulation is multi-cellular with a solar-like poleward flow near the surface at low latitudes. In most of the cases, the mean magnetic field is oscillatory with equatorward migration in two cases. In other cases, the equatorward migration is overlaid by stationary or even poleward migrating mean fields.

Place, publisher, year, edition, pages
2013. Vol. 778, no 2, 141- p.
Keyword [en]
convection, dynamo, magnetohydrodynamics (MHD), Sun: activity, Sun: rotation, turbulence
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Other Physics Topics
URN: urn:nbn:se:kth:diva-139283DOI: 10.1088/0004-637X/778/2/141ISI: 000327762800056ScopusID: 2-s2.0-84887247882OAI: diva2:684612
EU, European Research Council, 227952Swedish Research Council, 621-2007-4064EU, FP7, Seventh Framework Programme, 228398

QC 20140108

Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2014-01-08Bibliographically approved

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Warnecke, JörnKäpylä, Petri J.Brandenburg, Axel
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