Abstract

When stars like our Sun are young, they rotate quite rapidly. Observations of these young suns indicate that they generally possess strong magnetic activity. Here we explore 3-D MHD simulations of dynamo action in rapidly rotating suns. Our simulations with the anelastic spherical harmonic (ASH) ... Show moreWhen stars like our Sun are young, they rotate quite rapidly. Observations of these young suns indicate that they generally possess strong magnetic activity. Here we explore 3-D MHD simulations of dynamo action in rapidly rotating suns. Our simulations with the anelastic spherical harmonic (ASH) code extend from 0.72 to 0.97 solar radii and thus span the bulk of the stellar convection zone. We find that these stars achieve strong dynamo action, and naturally build remarkable global-scale magnetic structures in their convection zones. These wreaths of magnetism fill the convection zone and retain coherence over long epochs despite being embedded in the turbulent convection. This is in striking contrast to many theories of the global solar dynamo, which is thought to require a tachocline of shear and penetration at the base of the convection zone to achieve such structures. Wreath-building dynamos can undergo repeated cycles of magnetic polarity reversal, with the global-scale magnetic structures changing their sense on thousand day timescales. Show less