3D finite element simulation of electric fields (arrows) within Earth's lithosphere arising from magnetospheric "ring current" excitation a layered mantle overlain by a surface conductance model*, an electrically heterogenous layer (colors) which represents the distribution of oceans and continents along with the lateral variablity in ocean depth and sediment thickness. Fully 3D simulations like that shown below are a key element of any electromagentic study of not only deep earth structure, but also of the electromagentic environment at satellite altitudes and beyond.

*Everett,M.E., S. Constable, and C.G. Constable, 2003: Effects of near-surface conductance on global satellite induction responses, Geophys. J. Int., 153, 277-286.