Effects of Penetrative Convection on Solar Dynamo

TL;DR

This study uses advanced simulations to explore how penetrative convection influences the solar dynamo, revealing the formation of a tachocline-like shear layer and large-scale magnetic fields, with implications for understanding solar magnetic activity.

Contribution

It demonstrates that a stably stratified layer is crucial for organizing large-scale magnetic fields in solar dynamo models, without being necessary for polarity reversals.

Findings

A tachocline-like shear layer forms with penetrative convection.

Large-scale magnetic fields with dipole symmetry develop in the stable layer.

Polarity reversal occurs globally regardless of the stable layer presence.

Abstract

Spherical solar dynamo simulations are performed. Self-consistent, fully compressible magnetohydrodynamic system with a stably stratified layer below the convective envelope is numerically solved with a newly developed simulation code based on the Yin-Yang grid. The effects of penetrative convection are studied by comparing two models with and without the stable layer. The differential rotation profile in both models is reasonably solar-like with equatorial acceleration. When considering the penetrative convection, a tachocline-like shear layer is developed and maintained beneath the convection zone without assuming any forcing. While turbulent magnetic field becomes predominant in the region where the convective motion is vigorous, mean-field component is preferentially organized in the region where the convective motion is less vigorous. Especially in the stable layer, the strong large-scale field with a dipole symmetry is spontaneously built up. The polarity reversal of the mean-field component takes place globally and synchronously throughout the system regardless the presence of the stable layer. Our results suggest that the stably stratified layer is a key component for organizing the large-scale strong magnetic field, but is not essential for the polarity reversal.