Angular Momentum Transport by Gravity Waves in the Solar Interior

We present self-consistent numerical simulations of the sun's convection zoneand radiative interior using a two-dimensional model of its equatorial plane.The background reference state is a one-dimensional solar structure model.Turbulent convection in the outer convection zone continually excites gravitywaves which propagate throughout the stable radiative interior and deposittheir angular momentum. We find that angular velocity variations in thetachocline are driven by angular momentum transported by overshootingconvective plumes rather than the nonlinear interaction of waves. The mean flowin the tachocline is time dependent but not oscillatory in direction. Since theforcing in this shallow region can not be described by simple linear waves, itis unlikely that the interaction of such waves is responsible for the solarcycle or the 1.3 year oscillation. However, in the deep radiative interior, theinteraction of low amplitude gravity waves, continually excited by theovershooting plumes, is responsible for the angular velocity deviationsobserved there. Near the center of the model sun the angular velocity deviationis about two orders of magnitude greater than that in the bulk of the radiativeregion and reverses its direction (prograde to retrograde or vice versa) in theopposite sense of the angular velocity deviations that occur in the tachocline.Our simulations thus demonstrate how angular velocity variations in the solarcore are linked to those in the tachocline, which themselves are driven byconvective overshooting.Comment: submitted to Ap