Geomagnetic storms are brewing, but not every colorful light in the night sky is an aurora. For instance, Yuri Beletsky sends this picture taken Dec. 17th from the Atacama desert in Chile:
"These are not auroras. We just witnessed an amazing display of airglow," says Beletsky. "It was so intense that you could not see many stars close to the horizon - the sky was literally shining."
Airglow is an aurora-like phenomenon in the upper atmosphere caused by a variety of chemical reactions. It begins during the day when solar ultraviolet radiation ionizes atoms and molecules. At night, those same atoms and molecules glow as they re-capture lost electrons. The green in Beletsky's photo comes from oxygen atoms in a layer 90-100 km high; the red is probably associated with OH ions at an altitude of about 85 km. The wavy structure of the glow is due to high-altitude gravity waves, which alter the temperature and density structure of the upper atmosphere.
"Airglow is much less intense than aurora," continues Beletsky. "The display I saw looked, to the naked eye, like a series of black-and-white waving bands. The full color of the display was easily captured, however, by my digital camera."
www.spaceweather.com
Airglow is an aurora-like phenomenon in the upper atmosphere caused by a variety of chemical reactions. It begins during the day when solar ultraviolet radiation ionizes atoms and molecules. At night, those same atoms and molecules glow as they re-capture lost electrons. The green in Beletsky's photo comes from oxygen atoms in a layer 90-100 km high; the red is probably associated with OH ions at an altitude of about 85 km. The wavy structure of the glow is due to high-altitude gravity waves, which alter the temperature and density structure of the upper atmosphere.
"Airglow is much less intense than aurora," continues Beletsky. "The display I saw looked, to the naked eye, like a series of black-and-white waving bands. The full color of the display was easily captured, however, by my digital camera."
www.spaceweather.com
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