The differential rotation of G dwarfs

TL;DR

This paper models the differential rotation of G dwarf stars, explaining observed rotation profiles through mean-field equations, and identifies key physical effects influencing surface shear and internal rotation laws.

Contribution

It provides a comprehensive theoretical framework for understanding the rotation laws of G dwarfs, linking convection zone depth, shear layers, and physical effects like the Lambda effect and barocline effect.

Findings

Reproduces rotation laws of various G dwarfs.

Shows convection zone depth affects surface shear.

Identifies physical mechanisms behind differential rotation.

Abstract

A series of stellar models of spectral type G is computed to study the rotation laws resulting from mean-field equations. The rotation laws of the slowly rotating Sun, the fast rotating MOST stars epsilon Eri and kappa1 Cet and the rapid rotators R58 and LQ Lup can easily be reproduced. We also find that differences in the depth of the convection zone cause large differences in the surface rotation law and that the extreme surface shear of HD 171488 can only be explained with a artificially shallow convection layer. We also check the thermal wind equilibrium in fast-rotating G dwarfs and find that the polar subrotation (dOmega/dz<0) is due to the barocline effect and that the equatorial superrotation (dOmega/dr>0) is due to the Lambda effect as part of the Reynolds stresses. In the bulk of the convection zones where the meridional flow is slow and smooth the thermal wind equilibrium actually holds between the centrifugal and the pressure forces. It does not hold, however, in the bounding shear layers including the equatorial region where the Reynolds stresses dominate.