Parameter dependences of convection driven dynamos in rotating spherical fluid shells

TL;DR

This paper explores how key parameters influence convection-driven magnetic field generation in rotating spherical shells, highlighting transitions between different magnetic field structures and types of oscillating dynamos.

Contribution

It extends previous studies by examining higher Prandtl numbers and uniform heat flux conditions, providing new insights into dynamo behavior and transitions.

Findings

Transition from non-axisymmetric to axisymmetric magnetic fields depends on magnetic and ordinary Prandtl numbers.

Various oscillating dynamo types are identified and explained as dynamo waves or oscillations.

Higher Prandtl numbers influence the nature of dynamo transitions and oscillations.

Abstract

For the understanding of planetary and stellar dynamos an overview of the major parameter dependences of convection driven dynamos in rotating spherical fluid shells is desirable. Although the computationally accessible parameter space is limited, earlier work is extended with emphasis on higher Prandtl numbers and uniform heat flux condition at the outer boundary. The transition from dynamos dominated by non-axisymmetric components of the magnetic field to those dominated by the axisymmetric components depends on the magnetic Prandtl number as well as on the ordinary Prandtl number for higher values of the rotation parameter $\tau$. The dependence of the transition on the latter parameter is also discussed. A variety of oscillating dynamos is presented and interpreted in terms of dynamo waves, standing oscillation or modified relaxation oscillations.