Pink aurora lit up the sky over Norway

On Saturday evening, auroras of unusual pink color flashed over Tromso in Norway

"We were all so amazed that we were speechless," says the Northern Lights guide Marcus Varick, who photographed these consequences of geomagnetic disturbances in the earth's atmosphere.

Auroras are usually green. This is the color of oxygen atoms when they collide with energetic particles at an altitude of 100 to 300 km above the Earth's surface. Pink appears when energetic particles drop lower than usual, hitting nitrogen molecules at a level of 100 km and below. Sometimes this is called the "nitrogen strip".

"It was only the second splash of pink I've ever seen," says Varick.