This story is a supplement to the feature "Bracing the Satellite Infrastructure for a Solar Superstorm" which was printed in the August 2008 issue of Scientific American.
Electric currents in the ionosphere induce electric currents in the ground and in pipelines. These currents surge into transformers and can fry them. It would take weeks or longer for workers to fix them all.
Off the Grid
The entire East Coast and much of the rest of the country would lose power. This map (below) shows the blacked-out regions expected from a severe storm like that of 1921, which would induce ground fields of about 20 volts per kilometer. Scientists have yet to model the effects of a full-blown 1859-like storm on the power grid.