CONTACT: GARY GALLUZZO
100 Old Public Library
Iowa City IA 52242
(319) 384-0009; fax (319) 384-0024
Release: May 31, 2000
Embargoed for Release: Thursday, June 1, 2000
UI professor observes space weather/Earth connection
IOWA CITY, Iowa -- University of Iowa physics professor Jack Scudder said
today (Thursday, June 1) that an international team of physicists has significantly
advanced mankind's understanding of the northern lights and related phenomena
by making the first direct observations of the switch that permits energy
to be transferred between the solar wind and the Earth.
Scudder, who spoke on behalf of his co-authors at a news conference at the
spring meeting of the American Geophysical Union in Washington, D.C., noted
that the naturally occurring switch for this energy transfer, known as "magnetic
reconnection," is responsible for the aurora borealis and australis,
as well as occasional interruptions in radio and satellite communications.
He said that the outer layer of the Earth's magnetosphere generally behaves
like a cocoon, shielding the Earth from reconnection, but that every once
in a while a tear appears as a result of reconnection.
"Sometimes the solar wind creates tears in the cocoon, and charged
particles and energy from the sun penetrate into the magnetosphere,"
said Scudder, who is principal investigator for the Hot Plasma Analyzer (HYDRA)
on NASA's Polar spacecraft. "We have directly observed these tears for
the first time using Polar.
"One of the most exciting things about the detection is finding that
such small-scale structures really do exist in the precise sizes predicted
25 years ago. Some of these tears are extremely small -- on the order of one
kilometer long," he said.
In the current investigation, scientists involved in the multi-satellite
International Solar-Terrestrial Physics (ISTP) program identified two general
areas where reconnection occurs. One region penetrated by Polar is 30,000
to 40,000 miles on the dayside of the cocoon, and the other (observed by the
Geotail satellite) is inferred to be some 85,000 to 96,000 miles downwind
of the Earth, on the night side of the planet and in the tail of the teardrop-shaped
magnetosphere. ISTP is a collaborative study between NASA, the Japanese space
agency (ISAS), and the European Space Agency (ESA), with contributions from
Russia's Institute for Space Research (IKI) and many other international science
The observation of magnetic reconnection is of interest to physicists because
it answers a half-century-old question surrounding the origin of the energy
responsible for auroras and magnetic disturbances. On the dayside of the Earth,
reconnection allows energy from the solar wind to enter the magnetosphere,
that volume of magnetic fields surrounding the Earth that contains the Van
Allen radiation belts. On the night side, reconnection permits the transfer
of energy down to the Earth's atmosphere, but the whole sequence is started
by reconnection on the dayside, as observed by Polar.
"Everything that happens regarding space weather happens through and
because of these slits," Scudder said. "We're excited that the data
clearly show the electrons jumping through these slits, doorways really, that
open the Earth to these particles from space. The $64 question is what makes
the tears possible. We'd like to see some more of them to know whether those
already detected represent a general or an unusual picture of the switch."
To better define where the tears take place, Scudder has helped outline
an entire NASA satellite mission. Dubbed BLAST (Boundary LAyer SnapshoT),
it would carefully study these small, but crucial, intersections of the magnetic
highways between the sun and the Earth. The investigation would be a collaborative
effort between the University of California, Berkeley; UCLA; the University
of Colorado and the University of Iowa. Additional information on reconnection
and ISTP can be found on the web at: http://www-st.physics.uiowa.edu/www/html/press/video.html.