Rapid Rotation, Active Nests of Convection and Global-scale Flows in Solar-like Stars

TL;DR

This study investigates how increased rotation rates in solar-like stars influence convection patterns and global flows, revealing localized convection nests, differential rotation, and altered meridional circulation structures.

Contribution

It provides the first detailed analysis of convection and flow patterns in rapidly rotating solar-like stars, highlighting the emergence of localized convection nests and changes in differential rotation and meridional circulation.

Findings

Localized convection nests form at high rotation rates.

Differential rotation shows increased shear with faster rotation.

Meridional circulation weakens and becomes multi-cellular at rapid rotation.

Abstract

In the solar convection zone, rotation couples with intensely turbulent convection to build global-scale flows of differential rotation and meridional circulation. Our sun must have rotated more rapidly in its past, as is suggested by observations of many rapidly rotating young solar-type stars. Here we explore the effects of more rapid rotation on the patterns of convection in such stars and the global-scale flows which are self-consistently established. The convection in these systems is richly time dependent and in our most rapidly rotating suns a striking pattern of spatially localized convection emerges. Convection near the equator in these systems is dominated by one or two patches of locally enhanced convection, with nearly quiescent streaming flow in between at the highest rotation rates. These active nests of convection maintain a strong differential rotation despite their small size. The structure of differential rotation is similar in all of our more rapidly rotating suns, with fast equators and slower poles. We find that the total shear in differential rotation, as measured by latitudinal angular velocity contrast, Delta_Omega, increases with more rapid rotation while the relative shear, Delta_Omega/Omega, decreases. In contrast, at more rapid rotation the meridional circulations decrease in both energy and peak velocities and break into multiple cells of circulation in both radius and latitude.