An Exercise To Model a "Solar Radiation Katrina"
Hugh Pickens writes in with an update on the warnings we discussed a year back about the dangers of a "solar Katrina." Now NPR is reporting on a tabletop exercise mounted in Boulder, Colorado by government workers attempting to model the effects of a worst-case solar electromagnetic storm. "...an exercise held in Boulder, Colorado, has investigated what might happen if the Earth were struck by a solar storm as intense as the huge storms that occurred in 1921 and 1859 — a sort of solar Katrina — and researchers found that the impact is likely to be far worse than in previous solar storms because of our growing dependence on satellites and other electronic devices that are vulnerable to electromagnetic radiation. 'In many ways, the impact of a major solar storm resembles that of a hurricane or an earthquake,' says FEMA Administrator Craig Fugate, except that a solar Katrina would cause damage in a much larger area — power could be knocked out almost simultaneously in countries from Sweden to Canada and the US. In the exercise, the first sign of trouble came when radiation began disrupting radio signals and GPS devices, says Tom Bogdan, who directs the Space Weather Prediction Center. Ten or 20 minutes later electrically charged particles 'basically took out' most of the commercial satellites that transmit telephone conversations, TV shows, and huge amounts of data we depend on in our daily lives. But the worst damage came nearly a day later, when the solar storm began to induce electrical currents in high voltage power lines strong enough to destroy transformers around the globe, leaving millions of people in northern latitudes without power."
You're mixing up two effects. You're correct that the direct EM radiation would affect largely only the sunlit portion of the Earth. However, the "second punch" of these events is the large burst of protons that arrives the next day -- it's the solar wind, but several orders of magnitude larger than usual.
These protons are affected by the geomagnetic field, and (to simplify a lot) rain down in large regions generally centered around the magnetic poles (cf. the auroral ovals), where they induce very large currents in long conductors like power lines, leading to general power failures that could not be easily repaired.
This wouldn't be your garden-variety blackout -- it would require physical replacement of massive equipment for which there are no spares readily available -- at least not in the quantities needed. Large numbers of people -- entire provinces and states in North America, and likely entire nations in northern Europe -- would be without power for months while new equipment was manufactured and installed. This would lead to mass migrations out of these areas, which would lead to social disruption and significant loss of life as critical systems, whose backup generators and other emergency systems were not designed for such an extended outage, failed.
I was in south Florida for Hurricane Wilma, and I can report to you that the social structure of the region almost broke down during the week or two the region was without electricity -- and this was a natural disaster, albeit a severe one, that people understood and had largely prepared for. Power was restored relatively quickly then, because (a) the causes, downed power lines, were easy to find and repair, and (b) there was a massive influx of utility workers from the rest of the country to help out. In a solar flare scenario, the cause would be much harder to fix, and there would be a much larger affected area (and, consequently, a much smaller unaffected area from which to draw support).