A previous muse of the origin of the geomagnetic field was posted here when I suggested the Van Allen Belt as a co-rotating torus of plasma is the probable cause of the geomagnetic field. Except the Earth does not have a geomagnetic dipole field but a quadrapole field.
At the 2016 Electric Universe conference Dr. Michael Clarage presented the latest, simple, model of the Earth’s geomagnetic field and it is now recognised that there are two co-rotating belts of charged particles co-rotating with the Earth, an inner electrically positive torus and an outer larger, electrically negative torus.
Two counter-rotating belts would generate the known quadrupole geomagnetic field. In addition 70% of the Earth’s surface is comprised of oceans that are negatively charged, and would constitute another source of the geomagnetic field. If we then include the polar Birkeland currents which themselves are also generating a magnetic field, or fields, then these would be sufficient to explain the geomagnetic field.