Late one cold winter night, during a massive winter storm that covers most of the Central and Eastern United States, a 100-kiloton nuclear warhead suddenly explodes 100 miles above Dallas, Texas. Two minutes later, identical nuclear warheads explode over Las Vegas, Nevada, and Columbus, Ohio. Then a fourth and larger 800-kiloton warhead explodes over the southern Yucatan Peninsula.
The electromagnetic pulses (EMPs) produced by the first three nuclear detonations will act to almost instantly destroy the solid-state electronics that control the operation of most U.S. critical national infrastructure including the Emergency Power Systems and active Emergency Core Cooling Systems of 26 commercial nuclear reactors. The EMP E3A Blast Wave from the fourth detonation will create a final collapse of all three U.S. electric power grids, which will be knocked out of service for a year or longer.
Poster Comment:
An 1859 Carrington like event would do the same but worse.