Red Auroras Over Montana

Red Auroras Over Montana

Earth is exiting a solar wind stream that sparked bright auroras around the Arctic Circle on Feb. 17th and 18th. At its peak, the display was visible in several northern-tier US states. Philip Granrud sends this picture from the Polebridge Mercantile in northwest Montana:

"The Northern Lights were low to the horizon, but very bright," says Granrud. "It was a clear cold night, which helped with visibility."
Much of the sky was filled with red, a hue typical of auroras seen from a distance. Red auroras occur some 300 to 500 km above Earth's surface, much higher than ordinary green auroras. Because of their high altitude, reds can be seen over the horizon. In this case, the main display was probably taking place in Canada, far to the north of the Polebridge Mercantile.
Red auroras are not fully understood. Some researchers believe the red lights are linked to low energy electrons from the sun, which move too slowly to penetrate deeply into the atmosphere. When such electrons recombine with oxygen ions in the upper atmosphere, red photons are emitted. At present, space weather forecasters cannot predict when this will occur.

From SpaceWeather.com