CHANCE OF FLARES TODAY: NOAA forecasters say there is a 25% chance of M-class solar flares today. The likely source, sunspot complex AR2907-09, is almost directly facing Earth, which means any explosions would be geoeffective. Solar flare alerts: SMS Text.
POLAR STRATOSPHERIC CLOUDS (UPDATED): Earth's most beautiful clouds just materialized inside the Arctic Circle. "We saw them on Dec. 14th, 15th and 16th," reports Laura Kranich, who photographed the colorful forms over Örnskjöldsvik, Sweden:
These are called "polar stratospheric clouds" (PSCs), and they are very rare. Normally the stratosphere has no clouds at all. PSCs form when the temperature drops to a staggeringly-low -85 C. Then, and only then, can sparse water molecules in the stratosphere begin to coalesce into tiny ice crystals -- the "stuff" of PSCs.
Because of their intense iridescent colors, PSCs are widely regarded as the most beautiful clouds on Earth. Sometimes they rival auroras themselves. "Once seen they are never forgotten," says atmospheric optics expert Les Cowley.
The display is now 5 days long. Arina Kraaijeveld saw PSCs drifting over Abisko, Sweden, on Dec. 18th:
"I was leading a tour to the Ice Hotel for Lights over Lapland when the clouds appeared," says Kraaijeveld. "We immediately pulled over to take their picture. Amazing!"
In a typical Arctic winter, PSCs appear two or three times at most. This early, long apparition might herald a good season. Arctic sky watchers, if you see a PSC, photograph it and send it here.
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