Cyclic magnetic activity due to turbulent convection in spherical wedge geometry

TL;DR

This paper presents simulations of turbulent magnetohydrodynamic convection in spherical wedge geometry, demonstrating the self-generation of large-scale magnetic fields with solar-like differential rotation and equatorward magnetic activity, resembling the solar cycle.

Contribution

First simulation showing large-scale magnetic field generation with both poleward and equatorward branches in spherical wedge geometry.

Findings

Magnetic fields amplified by dynamo action from weak initial fields.

Differential rotation is solar-like, with fast equator.

Discovery of an equatorward magnetic activity branch at ~20° latitude.

Abstract

We report on simulations of turbulent, rotating, stratified, magnetohydrodynamic convection in spherical wedge geometry. An initially small-scale, random, weak-amplitude magnetic field is amplified by several orders of magnitude in the course of the simulation to form oscillatory large-scale fields in the saturated state of the dynamo. The differential rotation is solar-like (fast equator), but neither coherent meridional poleward circulation nor near-surface shear layer develop in these runs. In addition to a poleward branch of magnetic activity beyond 50 degrees latitude, we find for the first time a pronounced equatorward branch at around 20 degrees latitude, reminiscent of the solar cycle.