FOR RELEASE: Noon, CST, Dec. 7, 1994

Steve Roy
Marshall Space Flight Center
Huntsville, Ala.
(205)544-6535

Donald Savage
NASA Headquarters
Washington, D.C.
(202)358-1727

Release: 94 - 117

RECENT STUDY SHOWS GAMMA-RAY FLASHES IN ATMOSPHERE ARE MORE COMMON THAN THOUGHT

Scientists are observing rare gamma-ray flashes above thunderstorms at a rate six times that of previous observations. The observations are being made by the Burst and Transient Source Experiment aboard NASA's Compton Gamma Ray Observatory which was recently modified by ground command to be more sensitive to the events.

Scientists at NASA's Marshall Space Flight Center in Huntsville, Ala., previously observed gamma-ray flashes above thunderstorm activity about once every six weeks. Now, they are observing such gamma-ray events weekly. The first indications of gamma-ray flashes above thunderstorms were detected by the Burst and Transient Source Experiment earlier this year.

It is suspected the gamma-ray flashes come from a rare type of powerful electrical discharge, similar to lightning, above large thunderstorm regions. The observed flashes are very brief, lasting only a few thousandths of a second. In the past two months most of the observed gamma-ray flashes have occurred near the equator, primarily over regions of South America and the East Indies known to have high thunderstorm activity.

These recent observations, made by the Burst and Transient Source Experiment, have been confirmed by other instruments on the Compton Observatory. The gamma-ray observations from the Earth's atmosphere and their association with thunderstorms is a complete surprise to scientific investigators. It is suspected the gamma-ray events may be related to faint, but visible electrical discharges observed and reported recently, high in the stratosphere above thunderstorms.

"The high rate of occurrence of these gamma-ray events suggest the presence of a little understood, but significant phenomena that will have impact in many scientific fields", explained Dr. Steve Goodman of the Marshall Center's Space Sciences Laboratory. "We're especially looking forward to the opportunity to bring together investigators from the fields of space and atmospheric physics to study these newly discovered events".

The new observations were presented at a meeting of the American Geophysical Union in San Francisco, today, by Dr. Steve Goodman.

The Compton Gamma Ray Observatory is managed by NASA's Goddard Space Flight Center in Greenbelt, Md. and the Burst and Transient Source Experiment is managed by Marshall Center.