How are planetary magnetic fields produced?
In basic electrodynamics, all magnetic fields are produced by currents of charge in motion, so ultimately within each planet there must be a rotating current of conducting, charged material. There is a reasonably good theory of solar and planetary magneto-dynamics worked out in the 1960’s and 1970’s by Eugene Parker that relates the rotation period and conductivity of the Sun and each planet to the geometry and strength of their magnetic fields. It even predicts that periodically, these magnetic fields should change their polarity. The Sun does this every 22 years ( twice the sunspot cycle); the Earth every 250,000 years or so. The periods can actually be computed just by knowing the conductivity and rotation period of the Sun and Earth. One feature of planetary magnetic fields is that they are almost always NOT aligned with the rotation axis of the planet. This indicates that the core of a planet is subject to its own physics, and that the flows of conducting material deep inside do n
