http://www.spaceweather.com/

NORTHERN LIGHTS: Last night (Dec. 15th), a slight uptick in the solar wind speed was enough to spark auroras around the Arctic Circle. In Troms, Norway, the earth turned nearly as green as the sky:

"The auroras appeared right after nightfall," says photographer Arild Heitmann. "The lights became more and more active until they exploded into a green feast over the river. Despite really cold temperatures, this river had large open areas, which were perfect for auroraphotos."

More auroras are possible on Dec. 17-18 when an even faster moving stream of solar wind is expected to hit Earth's magnetic field. NOAA forecasters estimate a 20% chance of polar geomagnetc storms.