#upper
AURORAS ARE NOT AURORAS: Two nights ago astrophotographer Ruslan Merzlyakov went to the coastal wilderness of Denmark's Thy National Park and set up his camera for a long exposure of the Milky Way. He found the galaxy surrounded by aurora-like bands of red and green:
"It wasn't the aurora borealis," says Merzlyakov. "This was a magnificent display of airglow."
#Airglow is aurora-like #phenomenon caused by #chemical #reactions in the #upper #atmosphere. It gets started during the day when the air is illuminated by #ultraviolet #radiation from the #sun. At night the delicate afterglow can be seen from dark-sky locations like Thy National Park.
Green airglow is caused by oxygen. Red airglow is more rare; it is caused by OH. These neutral molecules (not to be confused with the OH- ion found in aqueous solutions) exist in a thin layer 85 km high where gravity waves impress the red glow with a dramatic rippling structure.
Who needs auroras? "The airglow," says Merzlyakov, "was out of this world."
