Rapidly Rotating Suns and Active Nests of Convection

TL;DR

This study investigates how increased stellar rotation influences convection patterns, differential rotation, and meridional circulation in solar-type stars, revealing localized convection nests and changes in shear and circulation structures.

Contribution

It provides the first detailed analysis of convection and flow patterns in rapidly rotating stars, highlighting the emergence of convection nests and altered differential rotation.

Findings

Localized convection nests form at high rotation rates

Total shear in differential rotation increases with rotation speed

Meridional circulation weakens and becomes multi-cellular at rapid rotation

Abstract

In the solar convection zone, rotation couples with intensely turbulent convection to drive a strong differential rotation and achieve complex magnetic dynamo action. 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 global-scale patterns of convection in such stars and the flows of differential rotation and meridional circulation 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 localized convection emerges. Convection near the equator in these systems is dominated by one or two nests in longitude of locally enhanced convection, with 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 Delta Omega grows with more rapid rotation while the relative shear Delta Omega/Omega_0 decreases. In contrast, at more rapid rotation the meridional circulations decrease in energy and peak velocities and break into multiple cells of circulation in both radius and latitude.