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11/01/92

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NEWFOUNDLAND SENSORS SEEK TO SHED LIGHT ON LIGHTNING

STANFORD - Stanford researchers are setting up remote sensing equipment in Newfoundland hoping to understand better the possible effects of lightning on the ionosphere.

The equipment will enable scientists to study a recently discovered phenomenon called ionospheric heating, according to Umran Inan, professor of electrical engineering at Stanford's Space Telecommunications and Radioscience Laboratory.

The ionosphere, the region of earth's atmosphere between the stratosphere and the exosphere, extends from about 50 to 250 miles (80 to 400 km.) above the surface of the earth and is composed of ionized atoms. During the day, the sun's intense rays pummel the atoms, stripping off charged electrons. During the night, cosmic rays also ionize the atmosphere, but the density of electrons is lower.

Lightning and, to a lesser extent, radio transmitters, cause acceleration of this natural flow of electrons, producing a temperature rise known as ionospheric heating.

"We measure the changing density of electrons in the ionosphere," Inan said, "and the changing of temperature, which [measures] how energetic the electrons are."

Lightning has the most potent effect on the flow of electrons, according to electrical engineering graduate student Juan Rodriguez, who designed and built the sensing equipment. However, the random nature of lightning strikes makes experimentation difficult. So Inan will use Navy radio transmitters and measure at night, when other electron activity is also lower.

A radio signal will heat the electrons to be measured by the Stanford equipment. By turning the transmitters on and off, the sensing equipment will be able to measure the changes in the ionosphere.

Scientists chose to put the remote sensing equipment in Newfoundland because it is in a direct line with two Navy transmitters, one in Annapolis, Md. and the other in Maine. The positioning will allow researchers to measure the effects of both transmitters on the atmosphere.

"This is one step toward a more ambitious experiment where we will go after lightning itself," Inan said. Arizona may be the site for those experiments, since lightning is very frequent there.

-jns-

This release was written by Troy Parkins, a science writing intern at the Stanford News Service.

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