Dynamo theory has it covered imo, and it's not a million miles away from what I've been saying. I think where I'm wrong is that I thought gravity is a dominant factor, that it is causing the fluctuations that give us magnetism. But dynamo theory suggests it's convection currents, which makes a whole lot of sense. Columns of hotter, rising molten iron, surrounded by sinking cooler iron. Much like air around a fire. This motion will be constant so long as there's a constant heat source.
Gravity plays a role though in that it provides one means for the interior of the planet to heat up... tidal heating.
I would imagine that in terms of flow, convection is going to utterly dominate gravity.
According to this theory, for a magnetic field we need three things...
planetry rotation,
an electrically conductive fluid,
an internal energy source to drive convective currents.
Mercury is small, but has a magnetic field, probably because it meets these criteria.
Io doesn't have a magnetic field, despite an abundance of tidal heating, it is lacking a conductive fluid.
I think they're close to solving this without my help. There goes that Nobel prize.
Originally Posted by wufwugy
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