Solar activity can cause a severe geomagnetic storm producing widespread electric power grid failures similar to the effects of HEMP.

In February 2009 the National Academy of Sciences published a NASA – funded study which reported that a severe geomagnetic storm of a magnitude that risks widespread electric grid damage is expected about once in a century.  In a comparatively mild example from more recent history, on March 13, 1989, an intermediate-scale geomagnetic storm destroyed transformers in the Hydro-Quebec Power Authority and the entire Quebec power grid collapsed.

The last very severe storm occurred in 1859.  Referred to as a “Carrington Event,” after Richard Carrington, the British astronomer who observed the sun spots associated with eight days of severe solar weather.  In that event auroras were seen even at the equator, and telegraph networks – the only electrical equipment in existence – were down all over the world.

The report’s conclusion:  A severe geomagnetic storm could destroy the U.S. electric grid’s 300 key high voltage transformers within 90 seconds, cutting off most of America’s power.