ALBUFEIRA

Aurora - Ruka - Finlândia - 07.01.2011

NACREOUS CLOUD ALERT: Auroras aren't the only colors in the polar sky. Observers around the Arctic Circle are reporting vivid, iridescent nacreous clouds, which form in the stratosphere during the coldest months of northern winter. "Once seen they are never forgotten," says Marketa Stanczykova who photographed these specimens outside Reykjavik, Iceland, on Jan. 4th. Another onlooker in Reykjavik, Albert Jakobsson, describes how "the beautiful colors played in the clouds and kept going for about one and half hour after sunset."

WEEKEND AURORA WATCH: NOAA forecasters estimate a 30% chance of geomagnetic activity during the next 24 hours. High-latitude sky watchers should be alert for scenes like this. Timo Newton-Syms of Ruka, Finland, took the picture on Jan. 7th when a solar wind stream hit Earth's magnetic field. "The auroras where widespread and visible despite passing clouds and light pollution from the nearby ski slopes," he says. The same stream of solar wind continues to buffet Earth's magnetic field, and is the source of the expected geomagnetic activity this weekend.

Spaceweather.com