Maybe all those crazy and eccentric Doomsday Preppers on NatGeo are on to something.  Scientist say there's a 1-in-8 chance earth will sustain a catastrophic solar megastorm by 2020.  Thankfully these events are rare.

Solar flares are the stuff auroras are made of and most commonly they cause a fantastic light show if you live in the right area.

150 years ago earth was struck by The Carrington Event.  It was the most powerful solar storm in recorded history.  It melted telegraph lines and caused telegraph stations to catch fire.

A modern day Carrington Event has unknown consequences.  Protection has improved but not quite as much as technology has advanced.  We are more dependent on technology over the last fifty years much less a hundred before that.

The potential collateral damage in the U.S. of a Carrington-type solar storm might be between $1 trillion and $2 trillion in the first year alone, with full recovery taking an estimated four to 10 years, according to a 2008 report from the National Research Council.

If you're the prepping sort you'll want to account for a month of anarchy while society attempts to get the lights on and the water running.