Spoke-like differential rotation in a convective dynamo with a coronal envelope

Journal Article · Sun Dec 01 04:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/778/2/141· OSTI ID:22341933

Warnecke, Jörn; Käpylä, Petri J.; Brandenburg, Axel ^[1]

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1. NORDITA, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

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 ≈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 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.

• OSTI ID: 22341933
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 778; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BALANCES
CONVECTION
CYLINDRICAL CONFIGURATION
ENTROPY
LAYERS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MEAN-FIELD THEORY
MIGRATION
ROTATION
SIMULATION
SOLAR CORONA
SPHERICAL CONFIGURATION
SUN
SURFACES
TURBULENCE