The emergence of magnetic flux loops in sunlike stars

We explore the latitude of emergence of flux tubes at the surface of G stars as a function of the rotation rate, magnetic flux, and injection latitude at the bottom of the convective zone. Our analysis is based on a thin flux tube evolution code that has been developed to study the emergence of magnetic flux in the Sun and is well calibrated by detailed comparisons with solar observations. We study solar models with rotation rates between 1/3 and 10 times solar, injection latitudes phi(I), between 1 degrees and 40 degrees, and tubes with a range of held strengths, B-O, and fluxes. For our range of input parameters, we find that the mean latitude of emergence, [phi(E)], increases and its range decreases with higher rotation rates, that phi(E) less than or equal to 45 degrees for stars with rotational periods greater than or equal to 27 days, that phi(E) increases with B, in rapid rotators, while the reverse is true for slow rotators, that the dependence of phi(E), on B-O decreases with increasing phi(I), that tubes with higher flux emerge at larger phi(E), and that the footpoint separation depends linearly on B-O. We compare our results to other calculations and with observations of magnetic features on stars and suggest future observations and extensions of this research. Our results suggest that for near-polar starspots to occur, either active stars must have a larger range of phi(I) than inferred for the Sun, or differential rotation and meridional flows are more important for magnetic flux redistribution in these stars. Our models also imply that flux appearing near the equator of active stars may be generated by a distributed, rather than a boundary layer, dynamo.