Global Turbulent Solar Convection: a Numerical Path Investigating Key Force Balances in the context of the Convective Conundrum

TL;DR

This study uses advanced numerical simulations to explore solar turbulent convection, aiming to resolve the Convective Conundrum by achieving Sun-like differential rotation through controlling key parameters.

Contribution

It introduces a novel numerical approach that maintains solar parameters while increasing turbulence, successfully reproducing Sun-like rotation profiles and revealing new convective structures.

Findings

Achieved a Sun-like prograde equatorial rotation in simulations.

Identified vorticity rings near the poles that could exist on the Sun.

Demonstrated a shift from CIA to CI force balance promoting prograde rotation.

Abstract

Understanding solar turbulent convection and its influence on differential rotation has been a challenge over the past two decades. Current models often overestimate giant convection cells amplitude, leading to an effective Rossby number too large and a shift towards an anti-solar rotation regime. This Convective Conundrum, underscores the need for improved comprehension of solar convective dynamics. We propose a numerical experiment in the parameter space that controls $Ro$ while increasing the Reynolds number ($Re$) and maintaining solar parameters. By controlling the Nusselt number ($Nu$), we limit the energy transport by convection while reducing viscous dissipation. This approach enabled us to construct a Sun-like rotating model (SBR97n035) with strong turbulence ($Re \sim 800$) that exhibits prograde equatorial rotation and aligns with observational data from helioseismology. We compare this model with an anti-solar rotating counterpart, and provide an in-depth spectral analysis to investigate the changes in convective dynamics. We also find the appearance of vorticity rings near the poles, which existence on the Sun could be probed in the future. The Sun-like model shows reduced buoyancy over the spectrum, as well as an extended quasi-geostrophic equilibrium towards smaller scales. This promotes a Coriolis-Inertia (CI) balance rather than a Coriolis-Inertia-Archimedes (CIA) balance, in order to favor the establishment of a prograde equator. The presence of convective columns in the bulk of the convection zone, with limited surface manifestations, also hints at such structures potentially occurring in the Sun.