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11/01/92

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STANFORD BEGINS NEW ERA OF ANTARCTIC EXPLORATION

STANFORD - Three electronic devices built largely by Stanford students will be airlifted onto the Antarctic ice this month to begin further exploration of the earth's ionosphere and magnetosphere.

They, and a fourth device to be added next year, will compose the Automatic Geophysical Observatory (AGO), beginning a new era of Antarctic exploration driven by budget cuts and the exploding costs of crewed stations.

David Shafer, a doctoral candidate in electrical engineering, said the four stations will be able to give coverage of the polar region's interior not possible under current conditions.

"It's a much lower-cost way of doing this," he said. "There is no way you could build manned stations at each of these sites, but technology over the last 20 years has allowed this sort of thing to become very sophisticated."

The polar regions are particularly inviting for studies of the magnetosphere because "the magnetic field of Earth cusps in at the poles, so energetic particles from the sun get funneled toward the poles," he said. The impact of these particles on the Earth's atmosphere produces the auroras, among other phenomena.

For many years, until its closure because of maintenance and staff coasts, Stanford staffed an Antarctic base called Siple Station. Technicians and engineers working for Stanford frequently "wintered- over" at Siple, largely studying the magnetosphere. Other Stanford experiments have been run from Palmer Station on the Antarctic Peninsula that reaches toward South America.

Shafer was one of the technicians hired for Siple. He is now studying under Umran Inan, associate professor of electrical engineering, with hopes of getting his doctorate in June.

The three instruments to be installed in the Automatic Geophysical Observatory are blue boxes, 14 inches (35.5 centimeters) tall and 16 inches (41 cms) deep, constructed during the summer by three Stanford students.

The instruments will be housed in a prefabricated structure built so that it fits in the back of a Navy C-130. The hut can support a crew of four for several weeks.

Technicians from Stanford, the University of Maryland, Lockheed Corp., Dartmouth College, Bell Labs, and one Japanese group - all with experiments for these sites - will assemble station huts at McMurdo, the main U.S. base in the Antarctic. A group of three then will fly on the C- 130 to each site, landing on the ice on skis.

All the technicians going out "on the ice" have been trained at Stanford, and one has a doctorate from the university. They will spend several days setting up the equipment, then leave on the aircraft for McMurdo to ready the next station.

The devices will be set on racks in the huts and connected to a pair of loop antennas by a cable 500 feet (152 meters) long.

The Stanford team will be reading very low frequency natural- radio transmissions between 1-40 kHz. The data will be recorded on optical disks (about 2 gigabytes per year per station), and every year another team will visit the station to replace the disks. The data then will be distributed to the collaborators on CD-ROMS.

"One part of the experiment looks for naturally occurring radio waves," Shafer said. "The Earth's magnetic field traps energetic electrons from the sun.... These electrons are injected by solar flares. Some are accelerated by the earth's magnetic field . . . and they get trapped.

"They swirl around in the field lines and they bounce from pole to pole." They are trapped for days or weeks at a time, taking a tenth of a second to a few seconds to recoil from pole to pole.

Radio waves from lightning interacting with magnetospheric electrons create "whistlers," electromagnetic signals named for the whistling sound they make in radio receivers.

Because of these interactions, electrons that have been stably trapped in the magnetosphere can be "precipitated out"; they deposit their energy in the ionosphere at altitudes of 60-100 kms.

"The other [motivation] is just to study what's out there," Shafer said. "A lot of good data has been gathered from satellites, but satellites are only in one place at a time. They give you a very detailed picture about what's going on next to the satellite, but almost no comprehensive measurements. These ground-based measurements will complement the satellite measurements and help make sense out of it."

A third part of the study is to watch what happens to man- made signals sent from Navy communications transmitters used to probe the ionosphere. The waves bounce between the surface and the ionosphere and are altered by fluctuations in that boundary.

"That would be very helpful in pinning down some of the big unknowns about the energy balance in the outer part of the Earth's atmosphere," he added.

-jns/antarctic-

921101Arc2053.html


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