Solar storm is not the only source for a massive EM pulse that might just knock us back to the 19th century. Our enemies could do this to us in "the blink of an eye" with a high-altitude nuclear detonation. Reports that Russia, China, Iran, and North Korea have practiced firing a suitable missile from an oceangoing freighter have been floating around for years now. In 2004, the Electromagnetic Pulse Commission (created by Congress) issued a rather detailed report that makes fascinating if not terrifying reading. The report is available on the web. There has reportedly been progress in hardening critical infrastructure against this threat, but lacking a consolidated database and mandated compliance by providers of critical services, true resilience is still a long way off. Lots of interesting reads out there on the topic in the wide wide web of deceit.