Scientists Seek Sprite Light Source

[Dover]

by Mike Bettwy


Giant red blobs, picket fences, upward branching carrots, and tentacled octopi --- these are just a few of the phrases used to describe sprites --- spectacular, eerie flashes of colored light high above the tops of powerful thunderstorms that can travel up to 50 miles high in the atmosphere.


Image: This dramatic, garishly colored image was captured with a low-light level camera on June 7, 2001. It shows what appears to be a "burning tree", or red sprite, above the National Cheng Kung University campus in Tainan City, Taiwan. Credit: ISUAL Project, NCKU/NSPO, Taiwan

Most researchers have long supported the theory that sprites are linked to major lightning charges. Still, some scientists believe that conditions high in the atmosphere, like meteoritic dust particles or gravity waves might also induce sprite formation.

Now, a study led by Steven Cummer of Duke University, Durham, N.C. and Walter Lyons of FMA Research, Inc., Fort Collins, Colo. has found more evidence that sprites are generated by major lightning strikes. They also found the total charge, as it moves from the cloud to the ground, and multiplied by that distance, known as the "lightning charge moment," is most critical in the sprite''s development. The study appeared in the April 2005 issue of Journal of Geophysical Research---Space Physics.

During the summer of 2000, researchers from across the nation participated in the Severe Thunderstorm Electrification and Precipitation Study. While the primary goal was to study severe thunderstorms and their link to heavy rain and hail, scientists also gathered important data on lightning's role in triggering events above thunderclouds, like sprites.

Armed with the aid of sophisticated instruments and sensors, Cummer collected information from three thunderstorm outbreaks across the central U.S. and compared the "lightning charge moment" in both sprite and non---sprite producing lightning.

"The idea was that if other factors contributed to lowering the electric field threshold for sprite initiation, they would probably not always be present and we would find that sprites occasionally form after just modest lightning strokes," said Cummer. ..cont'd

http://www.physorg.com/news4423.html

[punpirate]

1. They're going to find more interesting stuff...

... without doubt. Electrical discharges between cloud layers are very interesting--lots of ionization and plasma effects to be studied.

Thanks--good article.