Solar-like differential rotation in a convective dynamo with a coronal envelope
(English)Manuscript (preprint) (Other academic)
We report on the results of four convective dynamo simulations with an souter coronal layer. The magnetic field is self-consistently generated by the convectivemotions beneath the surface. Above the convection zone we include a polytropic layerthat extends to 1.6 solar radii. The temperature increases in this regionto ≈8 times the value at the surface, corresponding to ≈1.2 times the value at the bottom of the spherical shell. We associate this region with the solar corona. We find a solar-like differential rotation with radial contours of constant rotation rate, together with a solar-like meridionalcirculation and a near-surface shear layer. This spoke-like rotation profile is caused by a non-zero latitudinalentropy gradient which violates the Taylor-Proudman balance via thebaroclinic term. The lower density stratification compared with the Sun leads to anequatorward return flow above the surface. The mean magnetic field is in most of the casesoscillatory with equatorward migration in one case. In other cases the equatorward migration is overlaid by stationary oreven poleward migrating mean fields.
Magnetohydrodynamics, convection, turbulence, Sun: dynamo, Sun: rotation, Sun: activity
Astronomy, Astrophysics and Cosmology
Research subject Astronomy; Space and Plasma Physics
IdentifiersURN: urn:nbn:se:su:diva-88888OAI: oai:DiVA.org:su-88888DiVA: diva2:614410