Can a solid FeS layer help explain Mercury’s unique magnetic field?

Abstract:

The origin of Mercury’s weak magnetic field and displaced magnetic equator remains poorly understood. While the field is likely generated by a planetary dynamo in the iron core of Mercury, producing a weak dipolar magnetic field with a displaced magnetic equator has proven to be a challenge for dynamo modelers.

Recent gravity measurements from the MESSENGER probe allow for a solid, dense layer at the base of Mercury’s mantle. The authors of this study have suggested that this could be a solid layer of FeS. This solid FeS could reduce the observed field strength due to the electromagnetic skin effect. It may also affect the character of the dynamo by coupling to the fluid flow via the Lorenz force.

We use a numerical dynamo model with an electrically conducting, solid mantle layer to determine whether this solid layer can help produce the strength and morphology of Mercury’s magnetic field.