[Update: National Geographic says the flare might be the largest ever observed, "shooting perhaps the largest amount of solar material into space ever seen, scientists say."]
The largest solar flare in 4 years occurred today. It might knock out some power grids.
As I've previously warned, if we don't harden the grids and nuclear power plants against electromagnetic forces, a solar flare could eventually cause widespread nuclear disasters which make Fukushima look tame.