In this Sept. 15, 2017 photo provided by the U.S. Army Alaska, soldiers from Alpha Company, 70th Brigade Engineer Battalion, 1st Stryker Brigade Combat Team, 25th Infantry Division, based at Fort Wainwright, Alaska, conduct unscheduled field maintenance under the Northern Lights on a squad vehicle in preparation for platoon external evaluations at Donnelly Training Area, near Fort Greely, Alaska.
During the storm, a coronal hole (the spots that appear black on the sun) prompts high winds, which in turn, trigger coronal mass ejections, or CMEs. A CME projects plasma and pieces of the sun’s magnetic field into the atmosphere.
But, like a taut rubber band when it’s released, the magnetic field snaps back, and the force of that recoil creates powerful ripples known as Alfvén waves about 80,000 miles from the ground. As those waves get closer to Earth, they move faster thanks to the planet’s magnetic pull.
“Think about surfing,” said Jim Schroeder, an assistant physics professor at Wheaton College who has led research on the process. “In order to surf, you need to paddle up to the right speed for an ocean wave to pick you up and accelerate you, and we found that electrons were surfing. If they were moving with the right speed relative to the wave, they would get picked up and accelerated.