Differential rotation in convecting spherical shells with non-uniform viscosity and entropy diffusivity

Gupta, P., MacTaggart, D. and Simitev, R. D. (2023) Differential rotation in convecting spherical shells with non-uniform viscosity and entropy diffusivity. Fluids, 8(11), 288. (doi: 10.3390/fluids8110288)

Abstract

Contemporary three-dimensional physics-based simulations of the solar convection zone disagree with observations. They feature differential rotation substantially different from the true rotation inferred by solar helioseismology and exhibit a conveyor belt of convective “Busse” columns not found in observations. To help unravel this so-called “convection conundrum”, we use a three-dimensional pseudospectral simulation code to investigate how radially non-uniform viscosity and entropy diffusivity affect differential rotation and convective flow patterns in density-stratified rotating spherical fluid shells. We find that radial non-uniformity in fluid properties enhances polar convection, which, in turn, induces non-negligible lateral entropy gradients that lead to large deviations from differential rotation geostrophy due to thermal wind balance. We report simulations wherein this mechanism maintains differential rotation patterns very similar to the true solar profile outside the tangent cylinder, although discrepancies remain at high latitudes. This is significant because differential rotation plays a key role in sustaining solar-like cyclic dipolar dynamos.

• Item Type: Articles
• Additional Information: This equipment was funded by BEIS capital funding via STFC capital grant ST/R00238X/1 and STFC DiRAC Operations grant ST/R001006/1. DiRAC is part of the National e-Infrastructure.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Mactaggart, Dr David and Simitev, Professor Radostin and Gupta, Parag

Creator Roles

Gupta, P.: Investigation, Writing – original draft, Visualization
Mactaggart, D.: Formal analysis, Writing – original draft, Writing – review and editing, Supervision
Simitev, R.: Conceptualization, Methodology, Software, Formal analysis, Resources, Writing – original draft, Writing – review and editing, Supervision

• Authors: Gupta, P., MacTaggart, D., and Simitev, R. D.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
• Journal Name: Fluids
• Publisher: MDPI
• ISSN: 2311-5521
• ISSN (Online): 2311-5521
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Fluids 8(11):288
• Publisher Policy: Reproduced under a Creative Commons License