Global-scale Magnetism (and Cycles) in Dynamo Simulations of Stellar Convection Zones

TL;DR

This paper investigates global-scale magnetic field generation in rapidly rotating stellar convection zones through 3-D MHD simulations, revealing organized wreath-like magnetic structures and cyclic polarity reversals.

Contribution

It introduces detailed 3-D MHD simulations of stellar dynamos at high rotation rates, highlighting global-scale magnetic organization and cyclic behavior not previously characterized.

Findings

Magnetic fields form wreath-like structures in the convection zone.

The D5 simulation exhibits quasi-cyclic polarity reversals.

Global-scale magnetic organization is driven by rapid rotation.

Abstract

Young solar-type stars rotate rapidly and are very magnetically active. The magnetic fields at their surfaces likely originate in their convective envelopes where convection and rotation can drive strong dynamo action. Here we explore simulations of global-scale stellar convection in rapidly rotating suns using the 3-D MHD anelastic spherical harmonic (ASH) code. The magnetic fields built in these dynamos are organized on global-scales into wreath-like structures that span the convection zone. We explore one case rotates five times faster than the Sun in detail. This dynamo simulation, called case D5, has repeated quasi-cyclic reversals of global-scale polarity. We compare this case D5 to the broader family of simulations we have been able to explore and discuss how future simulations and observations can advance our understanding of stellar dynamos and magnetism.