Is the size of Earth's gravitational field the same size as it's electric/magnetic field? Also, what is the standard theory as to why the Earth has a magnetic field? What I mean is, how is it generated? Is it the result of the Earth traveling through space and interacting with the rays etc. of the Sun? Or, does the Earth generate the magnetic field itself - almost as a planetary dynamo due to plate tectonics and the motion/composition of it's core? Thanks!