CME - Corona Mass Ejections are the nearest thing to EMPs that we have experienced. That being said there was a CME in 1857 that could be said to be the “model” of a hostile EMP attack. It was powerful enough to induce telegraph line to ground sparking, temporarily knock out telegraph communication and electrocute some telegraph operators (As near as I can tell from the accounts I have read none were killed!).
http://www.futurescience.com/emp/vehicles.html
http://www.futurescience.com/emp/EMP-myths.html
http://www.futurescience.com/emp/EMP-Sitemap.html