To complicate the riddle, the sun also is undergoing one of its oddest magnetic reversals on record. Normally, the sun's magnetic north and south poles change polarity every 11 years or so. During a magnetic-field reversal, the sun's polar magnetic fields weaken, drop to zero, and then emerge again with the opposite polarity. As far as scientists know, the magnetic shift is notable only because it signals the peak of the solar maximum, said Douglas Biesecker at NASA's Space Environment Center. But in this cycle, the sun's magnetic poles are out of sync, solar scientists said. The sun's north magnetic...