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Secret of 'Sprites' Exposed

A very low frequency radio antenna is helping researchers distinguish between lightning strikes in thunderstorms that produce towering luminous glows called sprites, and ones that don't, according to a new study.

A team of scientists from the Stanford University and the University of Massachusetts reports in the most recent issue of Geophysical Research Letters that they've added another piece to understanding this mysterious phenomenon that accompanies thunderstorms.

Lightning that spawns sprites has two electrical signals, whereas normal lightning has just one, says Umran Inan, a Stanford electrical engineer. "It has a higher low frequency wave," he says, and it lasts longer than lightning that doesn't generate a sprite.

Inan is excited because this signature will enable sprite searchers to identify their quarry from great distances. "...We have a signature in the electromagnetic signal that lightning releases that tells us whether or not it will produce a sprite. And I can listen 12,000 kilometers away and say if this signal is a sprite, " he says. 

Sprites have only been studied for the past five years, so researchers are hungry for every scrap of information they can uncover about them.

Inan and his colleagues arrived at their findings by counting sprites in a Kansas thunderstorm, tallying 98 in 90 minutes.

"So far sprites have been pretty much detected over America, Australia and Japan. This way researchers can see whether or not they are occurring over Europe and Africa. We think they are, but this way they can prove it is actually happening," says Dana Moudry, a physics researcher at the University of Alaska, Fairbanks.

What sprites do still isn't certain. Walter Lyons, an atmospheric scientist at FMA research in Fort Collins Colorado, says sprites may play a role in the generation of stratospheric ozone.

And in spite of the potential value of a radio signal, Moudry says video recordings of sprites can offer something that a squiggle on a computer screen doesn't. 

"You still don't know about the structure of a sprite. A radio signal doesn't tell you what they look like," she says.

By Harvey Black, Discovery Online News

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Picture: Courtesy of Victor Pasko and Chris Barrington Leigh, Stanford University |
Video: Courtesy of University of Alaska, Fairbanks |

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