Influence of a coronal envelope as a free boundary to global convective dynamo simulations

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en Warnecke, J. Käpylä, P. J. Käpylä, M. J. Brandenburg, A. 2018-08-01T13:34:36Z 2018-08-01T13:34:36Z 2016-12-01
dc.identifier.citation Warnecke , J , Käpylä , P J , Käpylä , M J & Brandenburg , A 2016 , ' Influence of a coronal envelope as a free boundary to global convective dynamo simulations ' Astronomy and Astrophysics , vol 596 , A115 . DOI: 10.1051/0004-6361/201526131 en
dc.identifier.issn 0004-6361
dc.identifier.issn 1432-0746
dc.identifier.other PURE UUID: d5a1f0c4-5a46-4213-a671-bdf01a075510
dc.identifier.other PURE ITEMURL:
dc.identifier.other PURE LINK:
dc.identifier.other PURE FILEURL:
dc.description.abstract Aims. We explore the effects of an outer stably stratified coronal envelope on rotating turbulent convection, differential rotation, and large-scale dynamo action in spherical wedge models of the Sun. Methods. We solve the compressible magnetohydrodynamic equations in a two-layer model with unstable stratification below the surface, representing the convection zone, and a stably stratified coronal envelope above. The interface represents a free surface. We compare our model to models that have no coronal envelope. Results. The presence of a coronal envelope is found to modify the Reynolds stress and the Λ effect resulting in a weaker and non-cylindrical differential rotation. This is related to the reduced latitudinal temperature variations that are caused by and dependent on the angular velocity. Some simulations develop a near-surface shear layer that we can relate to a sign change in the meridional Reynolds stress term in the thermal wind balance equation. Furthermore, the presence of a free surface changes the magnetic field evolution since the toroidal field is concentrated closer to the surface. In all simulations, however, the migration direction of the mean magnetic field can be explained by the Parker-Yoshimura rule, which is consistent with earlier findings. Conclusions. A realistic treatment of the upper boundary in spherical dynamo simulations is crucial for the dynamics of the flow and magnetic field evolution. en
dc.format.mimetype application/pdf
dc.language.iso en en
dc.relation.ispartofseries Astronomy and Astrophysics en
dc.relation.ispartofseries Volume 596 en
dc.rights openAccess en
dc.subject.other Astronomy and Astrophysics en
dc.subject.other Space and Planetary Science en
dc.subject.other 113 Computer and information sciences en
dc.title Influence of a coronal envelope as a free boundary to global convective dynamo simulations en
dc.type A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä fi
dc.description.version Peer reviewed en
dc.contributor.department Max-Planck-Institut für Sonnensystemforschung
dc.contributor.department Department of Computer Science
dc.contributor.department University of Colorado Boulder
dc.subject.keyword Dynamo
dc.subject.keyword Magnetohydrodynamics (MHD)
dc.subject.keyword Sun: activity
dc.subject.keyword Sun: magnetic fields
dc.subject.keyword Sun: rotation
dc.subject.keyword Turbulence
dc.subject.keyword Astronomy and Astrophysics
dc.subject.keyword Space and Planetary Science
dc.subject.keyword 113 Computer and information sciences
dc.identifier.urn URN:NBN:fi:aalto-201808014319
dc.identifier.doi 10.1051/0004-6361/201526131
dc.type.version publishedVersion

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