Gamma Rays From Thunderstorms?

(From AScribe)

DURHAM, N.C. -- Duke University engineers have led the most detailed analyses of links between some lightning events and mysterious gamma ray emissions that emanate from earth's own atmosphere. Their study suggests that this gamma radiation fountains upward from starting points surprisingly low in thunderclouds. Counter-intuitively, these strong gamma outbursts also seem to precede associated lightning discharges by a split second.

"All of this comes as a huge surprise," said Steven Cummer, an assistant professor of electrical and computer engineering at Duke's Pratt School of Engineering. "These are higher energy gamma rays than come from the sun. And yet here they are coming from the kind of terrestrial thunderstorm that we see here all the time."

Cummer, Pratt School graduate student Wenyi Hu and postdoctoral researcher Yuhu Zhai described their analyses in a paper published online Saturday, April 30, in the journal Geophysical Research Letters. Other co-authors include David Smith of the University of California, Santa Cruz; Liliana Lopez of the University of California, Berkeley; and Mark Stanley of Los Alamos National Laboratory in New Mexico.

The research was funded by the National Science Foundation.

Natural emissions of gamma rays, the most energetic forms of light, are usually triggered only by high-energy events in outer space. Such events include thermonuclear reactions within the sun, interactions between cosmic rays and black-hole-creating star collapses.

But in 1994, scientists using the Compton Gamma Ray Observatory satellite first detected gamma rays seemingly originating near the earth's surface. And researchers quickly found evidence that those emissions were connected to lightning, Cummer said.