Geomagnetic induction: the study of geomagnetic induction physics

Abstract

Fluctuating electric currents, flowing external to the earth in the ionosphere, the magnetosphere, and beyond, act as primary source fields which cause electromagnetic induction in the solid earth. Secondary electric currents (or 'eddy currents') are thus induced to flow in the earth's oceans, crust, and upper mantle. The horizontal distances over which the primary and secondary currents flow are of the order of thousands of kilometres.