Stellar dynamo models with prominent surface toroidal fields

Abstract

Recent spectro-polarimetric observations of solar-type stars have shown the presence of photospheric magnetic fields with a predominant toroidal component. If the external field is assumed to be current-free it is impossible to explain these observations within the framework of standard mean-field dynamo theory. In this work it will be shown that if the coronal field of these stars is assumed to be harmonic, the underlying stellar dynamo mechanism can support photospheric magnetic fields with a prominent toroidal component even in the presence of axisymmetric magnetic topologies. In particular it is argued that the observed increase in the toroidal energy in low mass fast rotating stars can be naturally explained with an underlying $\alpha \Omega$ mechanism.

5 pages, 3 figures, accepted for publication in ApJL

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Cited by in corpus (12)

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• The magnetic field vector of the Sun-as-a-star. II. Evolution of the large-scale vector field through activity cycle 24
• Connecting the large- and the small-scale magnetic fields of solar-like stars
• Measuring stellar magnetic helicity density
• Magnetic Helicity Reversal in the Corona at Small Plasma Beta
• On effects of surface bipolar magnetic regions on the convection zone dynamo
• Migrating Dynamo Waves and Consequences for Stellar Current Sheets
• Various scenarios for the equatorward migration of sunspots
• An analytic mean-field ${\alpha }^2$-dynamo with a force-free corona
• Constraining the outer boundary condition for the Babcock-Leighton dynamo models
• Solar-like dynamos and rotational scaling of cycles from star-in-a-box simulations
• Magnetic field spreading from stellar and galactic dynamos into the exterior