Simulations of Turbulent Convection in Rotating Young Solarlike Stars: Differential Rotation and Meridional Circulation

Abstract

We present the results of three-dimensional simulations of the deepconvective envelope of a young (10 Myr) 1M(circle dot) star, obtainedwith the anelastic spherical harmonic code. Since young stars are knownto be faster rotators than their main-sequence counterparts, we havesystematically studied the impact of the stellar rotation speed, byconsidering stars spinning up to 5 times as fast as the Sun. The aim ofthese nonlinear models is to understand the complex interactions betweenconvection and rotation. We discuss the influence of the turbulencelevel and of the rotation rate on the intensity and the topology of themean flows. For all of the computed models, we find a solar-typesuperficial differential rotation, with an equatorial acceleration, andmeridional circulation that exhibits a multicellular structure. Even ifthe differential rotation contrast Delta Omega decreases only marginallyfor high rotation rates, the meridional circulation intensity clearlyweakens according to our simulations. We have also shown that, forTaylor numbers above a certain threshold (Ta greater than or similar to10(9)), the convection can develop a vacillating behavior. Sincesimulations with high turbulence levels and rotation rates exhibitstrongly cylindrical internal rotation profiles, we have considered theinfluence of baroclinic effects at the base of the convective envelopeof these young Suns to see whether such effects can modify the otherwisenear-cylindrical profiles to produce more conical, solarlike profiles.