Scientists hunt for x-ray source in lightning

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Researchers are using an array of electric field and x-ray detectors at a University of Florida (UF) and Florida Institute of Technology (FIT) lightning research facility in north Florida to discover the source of x-rays emitted by lightning strokes.

In the latest research published online in Geophysical Research Letters, electrical engineering doctoral student Joey Howard, the paper's lead author, and other UF/FIT researchers used a series of electric field detectors and sodium iodide x-ray detectors to try to probe x-rays more closely.

They narrowed the production of x-rays to the beginning of each step of the step leader, based on data gathered from one natural lightning strike and one triggered strike, according to Martin Uman, a professor of electrical and computer engineering.

"We could see when the electric field arrived at the sequence of stations, and it was the same with the x-rays," Uman said. "We then went back and calculated what the source location was for the field and the x-ray."

Uman said the research will continue with more expensive, faster and more sensitive x-ray detectors. One area of future interest, he said, is whether lightning strikes to airplanes could produce x-rays harmful to passengers.

"From a practical point of view, if we are going to ever be able to predict when and where lightning will strike, we need to first understand how lightning moves from one place to the other," said Joseph Dwyer, a professor in the department of physics and space sciences at FIT. "At present, we do not have a good handle on this. X-rays are giving us a close-up view of what is happening inside the lightning as it moves."