An aurora borealis swirls in the sky over the Yukon River village of Ruby, Alaska, a checkpoint of the Iditarod Trail Sled Dog Race on March 9.

The aurora borealis is seen from Mile 7 on Beam Road above snow-covered tundras near Nome, Alaska, March 10. A solar storm that shook the Earth's magnetic field on Thursday spared satellite and power systems as it delivered a glancing blow, although it could still intensify until early Friday, U.S. space weather experts said.