Picture of the Week—the Atmospheric Phenomenon Sprite

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This may look like a flying saucer of movie fame, but it's really an atmospheric phenomenon called a "sprite." Sprites appear 35 to 80 miles above the earth's surface; they can be set off when the lightning from a thunderstorm (only 7 to 10 miles high) excites the electric field farther up in the atmosphere. Though they appear above most thunderstorms, they appear so briefly—less then a second—and so high up that it's not so shocking that they weren't discovered until 1989. Like other similar phenomena called "elves," "trolls" and "goblins," sprites dance in the sky and are thought to be the source of some UFO sightings.

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