UF helps link lightning, X-rays

Published: Friday, January 31, 2003 at 6:01 a.m.
Last Modified: Friday, January 31, 2003 at 12:11 a.m.
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A rocket-triggered lightning bolt touches down on the rocket launch tower at the University of Florida International Center for Lightning Research and Testing, located in North Florida, in this undated photo from an automated camera. UF and Florida Institute of Technology researchers used data gathered from such strikes to determine that lightning emits X-rays, or possibly gamma rays or energetic electrons. The discovery, one of the rare instances when such high-energy, high frequency radiation has been reported in atmospheric conditions, may settle an 80-year-old debate.

AP Photo/University of Florida
As a magnet for lightning, the University of Florida's International Center for Lightning Research and Testing has made a living attracting a charge.
Ten years after moving from its original home at the Kennedy Space Center to Starke, it is now generating world-renowned prestige.
Scientists at the UF and Florida Institute of Technology have discovered X-rays and other high-energy radiation in triggered lightning strikes, research that experts say may open doors to new avenues of natural lightning research.
The findings, reported today in the journal Science, may help answer a decades-old question about lightning's high-energy properties, says Martin Uman, director of the UF lightning center.
"I think it's really exciting," Uman said. "We didn't expect to see anything at all and, then, all of a sudden, with almost every lightning stroke, we had X-rays."
While the findings may have few practical applications, Uman says the research could pave the way for the next phase of lightning study, including methods for protecting powerlines from strikes and improving protection systems for commercial aircraft.
Since the 1920s, researchers have tried to measure whether high-energy, high-frequency X-rays, gamma rays or energetic electrons were released during lightning strikes, a long-held but until now, unproven theory.
"It's a tough problem," Uman said. "Lightning never strikes near you and X-rays can only travel a few hundred yards through sea-level air."
To overcome the elusiveness of naturally occurring lightning, and the difficulty with measuring high-energy radiation, Uman and his team fired rockets trailed by wire toward passing storm clouds, essentially bringing the lightning to them.
Since 1993, Uman and colleague Vladimir Rakov have triggered lightning by firing rockets during the summer, disrupting the electric fields of passing clouds, from a tower at Camp Blanding. During successfully triggered strikes, wires attached to the 5-foot steel tubes conduct the lightning back to a targeted strike point on the ground.
Joe Dwyer, the Science study's lead investigator and an assistant professor of space science at the Florida Institute of Technology, measured the high-energy radiation released and found that intense bursts of radiation are released during the non-visual phase of lightning - when the charge is moving from the cloud to the ground, just before the visible stroke.
"There have been many things about lightning that no one thought was worth studying," Uman said.
But as scientists have gained insight into the formation and properties associated with lightning, many military and commercial applications have emerged. Lightning research, for example, has led to the development of satellite detection technology capable of discerning missile launches from lightning strikes, and improved the lightning protection systems for commercial aircraft.
Greg Bruno can be reached at 374-5026 or greg.bruno@ gvillesun.com.

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