Question

the earth's magnetic field : its history, origin, and planetary perspectiveedited by mcelhinny

Answer 1

According to Michael WMcElhinny, the origin of earth magnetic field is left out.

The present thinking about this is, briefly, the earth magma has electric currents and they are spiraling (or helical path) inside the earth. It is like solenoid. This is the reason why it has magnetic field. Also it keeps varying at very very slow pace and some times it reverses.