Cynthia L. Atwood, Science Correspondent
Yale University Office of Public Affairs
433 Temple St.
New Haven, CT 06520
(203) 432-1326, fax (203) 432-1323
[email protected]
Yale University Quarterly Science News Tips Sheet
December 1996
CONTACT: Cynthia L. Atwood #131
Embargoed by the American Astronomical Society until 10 a.m. EDT
Jan. 14, 1997
Yale and NASA Astronomers Predict Decline in Sunspots,
Which Could Bring Cooler Weather, Fewer Electronic Disruptions
New Haven, CT -- Fewer sunspots will erupt on the sun's surface
during the next decade, indicating an unexpected decrease in the
activity of magnetic fields that churn the sun's hot gases, Yale
University and NASA astronomers predict. The milder "space weather"
-- marked by a decrease in magnetic storms, cosmic rays and ionspheric
disturbances -- could bring cooler temperatures on earth, fewer power
blackouts and less interference with radio waves.
The optimistic prediction, which contradicts that of many other
scientists, will be reported Jan. 14 at a meeting of the American
Astronomical Society in Toronto, Canada, by Kenneth Schatten of
Goddard Space Flight Center/NASA in Greenbelt, Maryland. He and
Sabatino Sofia, chairman of the Yale astronomy department, inferred
the magnitude of magnetic fields just below the sun's surface from
observations with solar telescopes in Stanford and Big Bear,
California.
The researchers noted that the sun's magnetic activity, which
waxes and wanes in cycles lasting about eleven years, is as notoriously
unpredictable as the weather. "During the last 50 years, the sun has
displayed more activity than it has since Galileo first observed
sunspots in the early 1600's," said Professor Sofia. "Thus, if the
next solar cycle shows a downward trend, it could reverse the general
rise in activity which has occurred during the past 400 years."
Variations in solar activity have been linked to long-term climate
changes on earth, such as the global phenomenon known as the "Little
Ice Age" in the 1600's, which was triggered by a century of little
solar activity. The relatively abrupt cooling froze the Thames River
and caused glaciers around the world to advance. At the other extreme,
increased solar activity during the 11th and 12th centuries may have
triggered global warming that enabled the Vikings to inhabit Greenland,
which they were forced to abandon when solar activity waned, Dr.
Schatten said.
If his prediction for the coming decade proves accurate, the
milder space weather could help moderate global warming expected from
the greenhouse effect. It also would be good news for NASA, the Air
Force and others whose high-tech equipment is often affected by solar
storms, Professor Sofia said. For example, the enhanced "drag" caused
by a thickening in the earth's upper atmosphere during solar storms
can make satellites fall from orbit prematurely. The shortened life
of the Skylab satellite in the late 1970's was due to the exceptionally
high level of solar activity at that time.
Furthermore, enhanced solar cosmic rays can sometimes cause "glitches"
in the sophisticated electronic systems of satellites, while large
solar storms have been known to cause widespread power blackouts,
especially in northern latitudes, when power surges blow out
transformers.
Not everyone agrees with the Schatten and Sofia model for
predicting solar activity, which is based on the physics of how
magnetic fields are generated within the sun by a "dynamo" process,
similar to the way an automobile alternator generates electrical
voltages. Their Solar Dynamo Amplitude index -- which they call the
SODA index because it provides a prediction of the amount of magnetic
flux, or "fizz," below the sun's surface -- indicates that the next
solar cycle will peak in the year 2000.
Many statisticians are predicting a continued increase in solar
activity, based on recent patterns of fluctuations, said Dr. Schatten,
who explained that solar physicists divide cycles into odd and even
pairs. For most cycles -- and for all during this century -- solar
activity during the odd cycle of a pair exceeded that during the
previous even numbered cycle. Since the current, even-numbered cycle
was the second largest in recorded history, the next cycle would by
expected to be larger still. Yet, the Schatten & Sofia model predicts
a significant downturn.
"Are solar cycles random, or do they follow rules and behave
predictably, in the manner that planets orbit the sun? Put simply,
will our prediction technique beat the statistical rules, or will the
statisticians win? Stay tuned," said Professor Sofia.
###
Note to Editors: Sabatino Sofia, (203) 432-3011, is associate
director of Yale's Center for Solar and Space Research.
He developed the Solar Disk Sextant, which is a candidate for
installation in the year 2002 aboard the U.S. space station.
The experiment is designed to provide more accurate measurements of
changes in the sun's diameter and shape, and its long-term cyclic
changes in energy output.
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