© James Helmericks
"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. Such deep-penetrating particles are being produced by the solar wind stream now blowing around Earth.
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
Comment: See also: Veteran northern lights guide surprised to see rare pink and white auroras