The vigorous activity of young solar-type stars

Mark Miesch, miesch@ucar.edu, High Altitude Observatory, Boulder, Colorado, United States
Brown Benjamin, bpbrown@astro.wisc.edu, University of Wisconsin, Madison, United States

Abstract
During their long main-sequence lifetime, star like our Sun have strong magnetic fields at their surfaces. These fields are built by dynamo action in the sub-photospheric stellar convection zones by convective motions that couple with rotation to build and re-build the globally-ordered magnetism. In the Sun, the global magnetic fields reverses polarity every 11 years, and similar behavior is observed in many other stars. Modern simulations of stellar convection and dynamo action are for the first time achieving globally-organized magnetic fields and cyclic dynamo reversals. Here I will discuss recent simulations with the 3-D MHD anelastic spherical harmonic (ASH) code of young, rapidly rotating suns. In these simulations we have found cyclic dynamos. These wreath-building dynamos inhabit the stellar convection zone itself, even when a stably-stratified radiation zone is included in the model. This is a great surprise and suggests that globally-organized dynamo fields may exist even in stars with very deep convection zones.