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Tech Researcher Sheds Light on "Sprites," Jan. 28, 2000

Mark Stanley

SOCORRO, NM, January 28, 2000 -- Most everyone is familiar with the dazzling displays of lightning that accompany thunderstorms, but only a handful of atmospheric researchers (and high-altitude pilots) have ever caught a passing glimpse of the electrifying light shows that sometimes simultaneously occur miles above large thunderstorm systems.

Mark Stanley, a doctoral candidate at New Mexico Tech, is one of the few who, in the course of his dissertation research, has had several occasions to observe the lightning-related phenomena which have come to be aptly called "sprites."

Like the mythical, fleeting, fairy like apparitions they're named after, sprites are seldom seen, and, up until about ten years ago, their existence had never been verified with hard scientific evidence.

Red sprites, as atmospheric physicists are more prone to call them, are even more ephemeral than the more common forms of various electrical discharges found in the lower reaches of the Earth's atmosphere.

A sprite's characteristic aurora-like, sometimes deep red, sometimes faintly pinkish, luminous flash reaches into the upper levels of the stratosphere and beyond, and lasts only in the range of thousandths of a second, often stretching up to 60 miles above the Earth in its short lifespan, at times almost touching the beginnings of outer space.

(Also see Tech's Sprite Homepage.)

Stanley typically "hunts" for sprites from Langmuir Laboratory for Atmospheric Research, New Mexico Tech's mountaintop facility for lightning and cloud physics research.

From a vantage point of 10,600 feet above sea level, atop the Magdalena Mountains of central New Mexico, Stanley has detected sprites dancing on the horizon, on some nights as far away as northern Mexico, over the Gulf of California, or near Oklahoma City.

"Most of the time, I'm so busy running the equipment and collecting data that I don't often get a chance to actually see the sprites while they're occurring," he says. "Although, sometimes I do see them out of the corners of my eyes."

Stanley and other scientists involved in current sprite research rely mainly on visual records attained with special light-intensified cameras similar to some military night-vision equipment.

"The particular cameras that I've been working with came to us from the Marshall Space Flight Center and were used in several of NASA's space shuttle missions, so they're 'space-worthy' cameras, as well," Stanley points out.

Sprites are almost always directly associated with positive cloud-to-ground lightning strokes, a rare, highly energized form of lightning which has a polarity that is the opposite charge of "normal" lightning, the Tech researcher says.

"And, as such, I can use a network of ground-based sensors around the U.S.A. to find the locations where positive cloud-to- ground lightning are occurring when I'm looking for sprites," Stanley adds.

In his search for sprites, Stanley also employs lightning sensors and other lightning-tracking equipment which are stationed at Langmuir Laboratory . . . and in a spare bedroom in his home in Lemitar.

High-speed video of sprites taken by Stanley and his research colleagues show that sprites are typically initiated at an altitude of about 46 miles and usually develop simultaneously upward and downward from their point of origin.

 

The few frames of video footage that manage to capture the gigantic sprays of light almost always reveal the more common variants of sprites that atmospheric researchers descriptively dub "columns," "carrots," and "angels."

"Many of the characteristics of the sprites we've observed are consistent with a conventional breakdown mechanism for both sprite initiation and initial sprite development," Stanley relates.

In addition, in the course of his research, Stanley recently documented the first confirmed observation of daytime sprites.

"The daytime sprites emitted radio waves which were significantly larger than anything we've ever measured from any other previously observed sprites," he reveals. "The amount of charge dumped to ground by the parent lightning in order to produce these big daytime sprites was at least a factor of ten higher than the already unusually large amount of charge required to initiate sprites at night."

Stanley's sprite research has resulted in several technical papers being published in recent issues of a number of prestigious scientific journals, including Geophysical Research Letters, Eos Transactions, and Science News.

 


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