Dec. 26, 2016: Christmas Day 2016 brought a fantastic display of auroras to the Arctic Circle. A great many of them were pink. James Helmericks sends this picture from the Colville River Delta in northern Alaska:
“This was the brightest pink display I have ever seen, at one time even giving the snow a pink tinge,” he says.
The pink color is probably a sign of nitrogen. Most auroras are green–a verdant glow caused by energetic particles from space hitting oxygen atoms 100 km to 300 km above Earth’s surface. Seldom-seen pink appears when the energetic particles descend lower than usual, striking nitrogen molecules at the 100 km level and below.
On the days and nights around Christmas 2016, the pinks became so intense, they appeared white, not only to cameras, “but also to the naked eye,” says Sarah Skinner, who witnessed the strange colors several nights in a row from Abisko, Sweden. “It looked like someone had photoshopped the sky!” she says.
It is worth noting that these remarkable auroras appeared during a lull in solar activity. For three days centered on Christmas, the face of the sun was completely blank. There were no sunspots, no solar flares, and no CMEs. Instead, the display was caused by a high-speed solar wind stream blowing out of a large hole in the sun’s atmosphere. Such atmospheric holes are common during Solar Minimum, so we can expect many similar displays as the sunspot cycle crashes in the years ahead.