This cartoon depiction illustrates the electromagnetic coupling that occurs between the auroral electrojet in the ionosphere, the underlying geological features, and power systems in these high latitude areas exposed to the auroral activity. In areas of igneous rock geology (high resistivity), earth surface potentials can be created over large regions which can cause GIC to enter and exit power systems through the transformer neutral grounding points. It is also becoming understood that power systems adjacent to coastal areas (such as New Jersey) may be experiencing GIC from large induced currents in seawater that is being partially forced into power systems when they abruptly terminate at coastal areas.

Further, North America is the most profoundly affected land mass in the world because of igneous rock geologies which cover large regions. This enhances coupling to power systems and also because the magnetic north pole is tilted toward North America. This combined with the large infrastructure located at high geomagnetic latitudes substantially increase the exposure of these systems.

Above text and photos courtesy John Kappenman, Minnesota Power and Electric