RE: Article: Lightning emits X-Rays

[Randall_F_Brich@RL.GOV]

In 1953 Stanley Miller demonstrated in a laboratory simulation on a small

scale that an electric discharge through a reducing mixture of gases

produced plenty of amino acids (though not all of those that occur in living

organisms). 



Perhaps X-rays, from lightning, are the "missing link" researchers haven't

created when conducting origin of life experiments.





Randy Brich

USDOE

509-372-4617 (phone)

509-372-4549 (fax)

randall_f_brich@rl.gov 





The contents of this message are mine personally and do not reflect the

views or position of the U.S. Department of Energy or the Federal

Government.





-----Original Message-----

From: Timm, Jason [mailto:jdtimm@EHS.UFL.EDU]

Sent: Friday, January 31, 2003 7:26 AM

To: radsafe@list.vanderbilt.edu

Subject: Article: Lightning emits X-Rays





FLORIDA RESEARCHERS: LIGHTNING EMITS X-RAYS

Modern-day Ben Franklins use rockets to settle 80-year-old debate

GAINESVILLE, Fla. --- Anyone who has heard a radio crackle during a storm

knows lightning emits radio signals.

But in a series of unique experiments that involved firing wire-trailing

rockets into storm clouds, a team of Florida researchers has found that

"triggered" lightning also emits waves of energy much higher up the

frequency scale - X-rays, or possibly gamma rays or relativistic electrons.

Set to be reported Friday in the journal Science, the finding comes on the

heels of a similar discovery for natural lightning reported last year,

suggesting that all lightning emits such so-called energetic radiation. Not

only might the discovery finally settle a question that has been debated for

80 years, it also is among the rare instances where such high-energy,

high-frequency radiation has been reported in atmospheric conditions. Vacuum

tubes in doctor's office machines can produce X-rays on Earth, but otherwise

X-rays and gamma rays generally occur only in outer space, where they are

propagated by such extraordinary events as supernova explosions.

"I think it's really exciting," said Martin Uman, a lightning expert and

director of the University of Florida's International Center for Lightning

Research and Testing, where the experiments were done. "We didn't expect to

see anything at all, and then, all of a sudden, with almost every lightning

stroke, we had X-rays."

Debate over whether lightning emits energetic radiation dates back to the

1920s, when Nobel Prize physicist Charles Thomson Rees Wilson first

predicted the phenomenon. Numerous researchers have attempted to confirm or

refute his prediction, but results have proved inconclusive. That's because

natural lightning is devilishly hard to study, said Joe Dwyer, the lead

investigator on the project and an assistant professor of physics and space

science at the Florida Institute of Technology.

While there is no practical application for the discovery, it enhances the

basic understanding of lightning, which aids in development of lightning

protection systems, he said. X-rays, gamma rays and relativistic electrons

travel only a few hundred yards at most through the air at sea level, Dwyer

said.

Because no one knows where lightning will strike, obtaining accurate

measurements can be a matter of extraordinary luck rather than repeatable

experiment. Researchers also have been hamstrung by the difficulty of

distinguishing interference from true measurements. As a result, Dwyer said,

"there have been a whole long series of results, with roughly half positive

and half negative."

Dywer set out to obtain a more conclusive result. Rather than chase natural

lightning, he turned to the UF engineering college's lightning research and

testing center in rural North Florida. Researchers at the facility, located

at Camp Blanding near Starke, spark lightning by launching slender rockets

from batteries of steel tubs 2,400 feet toward passing storm clouds. Each of

the rockets trails a thin, Kevlar-coated wire designed to conduct the

lightning back to the targeted strike point on the ground.

Ground zero for the triggered lightning is the rocket launch tower. Dwyer

installed a carefully constructed detection system about 75 feet from this

tower. The system, contained in a heavy aluminum box with thick sides that

blocked out all signals except energetic radiation, consisted in part of two

photo multiplier tube detectors, standard equipment for measuring the

radiation. Two detectors were used so that one could act as a control.

Besides triggering the lightning, the UF group provided critical

measurements of its current and field strength. Manning the system from July

through September, the researchers triggered multiple lightning flashes.

Each flash typically contained several return strokes, or individual

lightning events that occur too quickly for the human eye to distinguish.

The detector recorded energetic radiation in 87 percent of 37 such strokes,

showing it occurred at the beginning or just before each stroke - the moment

when the charge moved down from the cloud and contacted the ground just

before the stroke.

"It's right before the visible stroke occurs - that appears to be when the

energetic radiation is being produced," Dwyer said. "Nobody really

understands completely how this is happening."

This phase of the lightning process is known as the "dart leader" and also

is present in natural lightning extending from clouds to the ground, which

suggests the findings likely apply to all cloud-to-ground lightning, Uman

said. It's also important the observations occurred near sea level, because

the lower the altitude, the harder it is for energetic radiation to generate

and propagate, he said.

Earth-orbiting satellites have recorded energetic radiation apparently

associated with thunderstorms. But few expected to see it produced at near

ground level, Dwyer said. "People didn't think the electric fields were

strong enough or that the length scales were long enough," he said.

Dwyer's project is part of a five-year, $410,000 Young Investigator Award

from the National Science Foundation, research performed in connection with

related NSF-sponsored research at UF. He plans to return to the lightning

research and testing center next summer to continue the investigation. At

the top of his priority list: narrowing down whether the energetic radiation

produced by lightning consists specifically of X-rays, gamma rays, energetic

electrons or some combination of the three. UF researchers are preparing an

improved set of supporting instruments for the experiment.

"We can go out there every summer," Dwyer said. "So it's finally become an

experimental science where we can do experiments and test theories, and it

never really was that before."





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