UpDate - Vol. 13, No. 15, Page 3
December 16, 1993
Down under; Antarctic data important to campus research

     Antarctica is an outdoor laboratory for two groups of physicists, one
headed by Thomas Gaisser, professor, and one by John Bieber, associate
professor, both faculty members of the Bartol Research Institute at the
University. The two teams are working on Antarctic research projects
involving astrophysics, funded by the National Science Foundation.
     Designated as a global laboratory under the international Antarctic
Treaty of 1959, Antarctica is an ideal location for carrying out certain
astronomical observations and other scientific activities. From Antarctica
during its summer season, the sun can be viewed almost continually for six
months. Because of its cold, dry climate, stars can be viewed more clearly,
and since it is close to the Earth's axis, the elevation of stars above the
horizon does not change. Cosmic rays entering the atmosphere also encounter
less interference from the Earth's magnetic field.
     Gaisser and his group are involved in a South Pole Air Shower
Experiment (SPASE), in conjunction with the University of Leeds in Great
Britain. Air showers are generated by high energy protons and nuclei called
cosmic rays traveling at nearly the speed of light, which enter the
atmosphere from all directions although one cannot see or feel them.
     Detectors have been installed on the ice to monitor unusual air shower
activity from binary or double stars or other astrophysical objects such as
supernovas. Air showers are continually passing through the atmosphere to
ground level. When the high energy particles from the showers hit the
sensors, the amplitude, time and direction are recorded, making it possible
to discover any unusual activity.
     The SPASE group receives one megabyte or about 10 percent of recorded
data by e-mail each week. The other 90 percent of the data is brought out
on tape at the end of the season. Data transfer may soon be upgraded so
that all the data will be available through e-mail.
     Although SPASE has been an ongoing activity for several years, this
year Gaisser and his team have become involved in a new project using a
pioneering instrument called AMANDA (Antarctic Muon and Neutrino Detector
Array), in conjunction with the University of Wisconsin and the University
of California at Berkeley and Irvine.
     The goal of the AMANDA project is to detect neutrinos and muons. Most
electrons in air showers are absorbed by the ice. But some high-energy
subatomic particles, called muons, are not absorbed. These can be measured
by new detectors, which will be installed in the ice in January. To install
these detectors requires melting 10 holes in the ice at the South Pole to a
depth of more than one kilometer. A cable with 20 photo tubes will be
lowered into each hole. These will be capable of detecting muons, which are
not absorbed by the kilometer of ice above.
     In addition to the installation of AMANDA, SPASE air shower detectors
will be placed on the surface in the same area.
     Coincidence between the two detectors will provide unique information
about the about the incident cosmic ray nuclei by sampling different
aspects of the same showers.
     Todor Stanev, associate professor; Paul Evenson, professor; and
post-doctorate fellows John Petrokis and Tim Miller also are on the Bartol
SPASE research team.
     Bieber is carrying on the neutron monitor program initiated by Bartol
director emeritus Martin A. Pomerantz in 1959. Broadly speaking Bieber is
interested in space plasma, the collection of charged particles emitted by
the sun that become solar winds, moving at a speed of 250 miles per second.
High energy particles originating in other parts of the galaxy encounter
these solar winds, and from this interaction, high energy protons, or
cosmic rays, arrive at the top of the atmosphere, producing sub-atomic
particles, some of which are neutrons.
     As the neutrons reach ground level, they are monitored in four areas
by Bartol-at two locations in Antarctica, one in Greenland and with a
36-ton monitor atop the roof of Sharp Laboratory on the Newark campus. Data
is relayed by e-mail from Anarctica and on diskettes at the end of the
season.
     Sun flares that occur periodically in cycles of approximately 11 years
intensify the number of neutrons entering the atmosphere, which is picked
up by the neutron monitors.
     The last major episode occurred in 1989 when there were seven solar
flares, the most recorded since these observations began. On Sept. 29,
1989, a solar flare set off the radiation alarm on the Concorde and caused
power outages and caused satellites to drop into lower orbit. This event
was recorded by the two neutron monitors in Antarctica, but less so in
Newark and Greenland.
     Neutron monitors can detect these flares minutes before the radiation
caused by the flares reaches a level that is potentially harmful to
astronauts and high-altitude space craft. In the future, this time lapse
may enable scientists and others to take precautionary measures.
     There is some discussion about cosmic rays affecting the weather, but
this is still controversial, Bieber said.
     Working with Bieber are professor Paul Evenson, electronics engineer
Leonard Shulman, research scientist Chang-Hua Tsao and post-doctoral fellow
Zhongmin Lin.
                                                  -Sue Swyers Moncure