© Markus Varik
Pink or white auroras appear when energetic particles from space descend lower than usual
WHITE AURORAS? Auroras are usually green. Occasionally, other colors appear: red, purple, blue. One color that never shows itself, however, is white -- that is, not until last night. "I saw white auroras over Tromsø, Norway!" reports veteran observer Markus Varik. He recorded the phenomenon in this photo:

"I've been working more than 400 nights as a Northern Lights guide, and although sometimes I think I've seen it all, never have i witnessed white auroras like that," says Varik. "It was amazing to see it unravel white like that in front of my eyes. Pure magic!"

Auroras get their colors from specific elements in Earth's upper atmosphere. Green auroras, for instance, come from atomic oxygen; blue is associated with molecular nitrogen. No element produces white. So where did it come from?

An important clue: Elsewhere in Scandinavia, intense ribbons of pale pink appeared. Here is a specimen recorded by an automated auroracam in Abisko, Sweden:

© Auroracam
These pink and white aurora seen in Sweden are somewhat rarer
Sarah Skinner, a tour guide with Lights over Lapland, saw the display: "OMG, it was the pinkest aurora ever!"

The 'white auroras' Varik photographed might actually be pink auroras filtered and paled by low-hanging clouds. Indeed, there is a strong hint of pink in Varik's photo.

Pink auroras are somewhat rare, but hardly unprecedented. They appear when energetic particles from space descend lower than usual, striking nitrogen molecules at the 100 km level and below.