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

References in corpus (4)

• Toroidal versus poloidal magnetic fields in Sun-like stars: a rotation threshold
• The connection between stellar activity cycles and magnetic field topology
• A Technique for Measuring Electrical Currents in the Solar Corona
• Surface appearance of dynamo-generated large-scale fields

Cited by in corpus (2)

• Two-scale analysis of solar magnetic helicity
• An analytic mean-field ${\alpha }^2$-dynamo with a force-free corona