Solarlike to Antisolar Differential Rotation: A Geometric Interpretation
Abstract
The solar convection zone rotates differentially, with its equatorial region rotating more rapidly than the polar regions. This form of differential rotation, also observed in many other lowmass stars, is understood to arise when Coriolis effects are stronger than those associated with buoyant driving of the convection. When buoyancy dominates, a socalled antisolar state of differential rotation results, characterized by rapidly rotating poles and a slow equator. The transition between these two states has been shown to occur when the intensity of these two forces is roughly equal or, equivalently, when the convective Rossby number of the system is unity. Here we consider an alternative view of the transition that relates this phenomenon to convective structure and convectivezone depth. Using a series of 3D rotatingconvectionzone simulations, we demonstrate that the solar/antisolar transition occurs when the columnar convective structures characteristic of rotating convection attain a diameter roughly equivalent to the shell depth. When the characteristic convective wavelength exceeds twice the shell depth, we find that the coherent convective structures necessary to sustain an equatorward Reynolds stress are lost, and an antisolar state results. We conclude by presenting a forcebalance analysis that relates this geometric interpretation of the transition to the convective Rossbynumber criteria identified in previous studies.
 Publication:

The Astrophysical Journal
 Pub Date:
 October 2022
 DOI:
 10.3847/15384357/ac879f
 arXiv:
 arXiv:2208.05591
 Bibcode:
 2022ApJ...938...65C
 Keywords:

 Solar convective zone;
 Stellar convective zones;
 Hydrodynamics;
 Solar differential rotation;
 Astrophysical fluid dynamics;
 Solar interior;
 Solar rotation;
 Stellar rotation;
 Stellar interiors;
 Helioseismology;
 1998;
 301;
 1963;
 1996;
 101;
 1500;
 1524;
 1629;
 1606;
 709;
 Astrophysics  Solar and Stellar Astrophysics;
 Physics  Fluid Dynamics
 EPrint:
 16 pages, 9 figures, accepted for publication in ApJ