Effects of stratification in spherical shell convection

TL;DR

This study uses simulations to explore how varying density stratification affects turbulent convection and differential rotation in spherical shells, revealing changes in convective cell size, turbulence anisotropy, and the emergence of near-surface shear layers.

Contribution

It demonstrates the impact of density stratification on convection patterns and differential rotation, including the transition from anti-solar to solar-like rotation.

Findings

Convective cell size decreases with increased stratification

Turbulence becomes more anisotropic as stratification increases

Near-surface shear layers appear in highly stratified, high Reynolds number runs

Abstract

We report on simulations of mildly turbulent convection in spherical wedge geometry with varying density stratification. We vary the density contrast within the convection zone by a factor of 20 and study the influence of rotation on the solutions. We demonstrate that the size of convective cells decreases and the anisotropy of turbulence increases as the stratification is increased. Differential rotation is found to change from anti-solar (slow equator) to solar-like (fast equator) at roughly the same Coriolis number for all stratifications. The largest stratification runs, however, are sensitive to changes of the Reynolds number. Evidence for a near-surface shear layer is found in runs with strong stratification and large Reynolds numbers.