From reversing to hemispherical dynamos

TL;DR

This paper demonstrates that weak equatorial symmetry breaking in planetary and stellar interiors can lead to hemispherical magnetic fields, unifying the phenomena of hemispherical dynamos and magnetic reversals.

Contribution

It introduces a model showing how symmetry breaking causes hemispherical magnetic fields and links this to magnetic reversals within a unified framework.

Findings

Hemispherical dynamos result from symmetry breaking in flow.

Interaction of dipolar and quadrupolar modes localizes magnetic fields hemispherically.

The process relates to magnetic field reversals.

Abstract

We show that hemispherical dynamos can result from weak equatorial symmetry breaking of the flow in the interior of planets and stars. Using a model of spherical dynamo, we observe that the interaction between a dipolar and a quadrupolar mode can localize the magnetic field in only one hemisphere when the equatorial symmetry is broken. This process is shown to be related to the one that is responsible for reversals of the magnetic field. These seemingly very different behaviors are thus understood in a unified framework.