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Effect of Density Stratification and Rotation on the Dynamics of Overshooting Convection

Presentation #129.06 in the session Tracking Plasma Flows in the Heliosphere — Poster Session.

Published onOct 20, 2022
Effect of Density Stratification and Rotation on the Dynamics of Overshooting Convection

Motivated by the deep solar interior, we study the dynamics associated with the overshooting of turbulent motions from an outer convective region into an underlying stably stratified radiative zone. We systematically examine the effect of density stratification and rotation on convective overshooting via the use of 3D fully nonlinear numerical simulations in a spherical shell by varying the number of density scale-heights in the convection zone, the degree of convective driving, and the rotation rate. We demonstrate that the overshoot lengthscale is a non-monotonic function of the number of density scale-heights in the convection zone and that it is proportional to Rρ 0.36, namely the ratio of the density stratification in the stable region over the one in the convection zone. We also show that the overshoot lengthscale decreases with Rossby number Ro as Ro0.23 (where the Rossby number is the ratio of inertial force to Coriolis force) while it also depends on latitude with higher Rossby cases leading to a weaker latitudinal variation. Finally, we examine the large-scale mean flows arising due to rotation and find that they extend below the base of the convection zone, even beyond the overshoot region, into the stable layer. These findings may elucidate the dynamics occurring within stellar convection zone-radiative zone interfaces, and motivate future studies specifically focused on the solar tachocline.

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