Between Jan. 15 and 20, a single collection of sunspots erupted seven times. Four of these events hurled into space powerful X-ray–emitting flares accompanied by billion-ton clouds of charged particles. The eruptions themselves weren't record breakers, but one was accompanied by a storm of high-energy protons that was the most energetic proton squall that's been recorded near Earth in 15 years.
The storm, detected by a weather satellite within minutes of a Jan. 20 solar flare, was particularly rich in protons packing more than 100 million electron-volts (MeV) of energy. Protons of this energy can burrow through 11 centimeters of water.
The proton storm caused several satellites to shut down temporarily. Among these were the infrared Spitzer Sp