I understand the earths magnetic field to be akin to a faraday homopolar generator. (First dynamo ever discovered btw, and the least understood)
However a homopolar dynamo requires either a permanent magnet to generate the ring voltage when undergoing rotation or a loop of current to generate the magnetic field. I understand that the Liquid Metal may constitute the “conductive disk” portion of the dynamo as iron is conductive, and I understand that the rotation of the earth causes the iron to rotate. I understand we are above the curie temp in the core so there is no permanent magnetization.
However it seems like a chicken/egg problem, you need a large external voltage to get the magnetic field, and you need the magnetic field to generate a ring voltage
Where is the voltage coming from to spark the dynamo? Is that even the right way to frame the conundrum?
Bonus question: why does faraday’s dynamo not work when only the magnet is rotated?