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December 22, 2000 --As the Sun's stormy season
approaches its zenith, solar scientists have the best seat in
the house, using the largest coordinated fleet of spacecraft
and ground observatories ever assembled to observe these angry
outbursts of solar radiation and predict the impact of turbulent
space weather.
According to scientists from NASA and NOAA, the Sun is near the
peak of its 11-year cycle of activity. Solar maximum is the two-to-three
year period around that peak when the Sun's activity is most
tempestuous and the Earth is buffeted with powerful solar gusts.
Above: Solar maximum is the two-to-three year period
around that peak when the Sun's activity is most complex and
turbulent, and the space around Earth is most disturbed. Notice
the dramatic changes in the Sun's atmosphere from solar minimum
in 1996 (left image) to solar maximum in 2000 (right image).
These false color images were captured by the Solar and Heliospheric
Observatory's (SOHO)
Extreme Ultraviolet Telescope (EIT) camera. Credit: NASA/ESA
"This is a unique solar maximum in history," said
Dr. George Withbroe, Science Director for NASA's Sun-Earth Connection
Program. "The images and data are beyond the wildest expectations
of the astronomers of a generation ago."
By combining sophisticated new instruments and time-tested
older ones, researchers believe their predictions and warnings
related to space weather
events are becoming more accurate and timely. "The new results
from space feed directly into NOAA's plans and programs for forecasting
space weather and its effects on Earth and technological systems,"
said Dr. Ernest Hildner, director of NOAA's Space
Environment Center in Boulder, CO.
The coordinated use of NASA and NOAA technology was key in tracking
and predicting the development of an intense solar storm nicknamed
the "Bastille
Day Event." With data from ground-based observatories,
the Solar and Heliospheric Observatory - a joint project of the
European Space Agency and NASA - and NOAA's Geostationary Operational
Environmental Satellites, scientists were able to anticipate
a bright solar flare and ensuing energetic proton shower July
13.
The flare coincided with a coronal mass ejection (CME) which
sent billions of tons of plasma into space traveling at 4 million
miles per hour, two times faster than normal.
 Left: A full halo coronal mass ejection recorded
on July 14, 2000, by SOHO's C2 coronagraph. "Halo events"
are CMEs aimed toward the Earth. As they loom larger and larger
they appear to envelop the Sun, forming a halo around our star.
The many speckles in the latter half of this animation are energetic
particles from a related solar flare bombarding SOHO's electronic
detectors. "The SOHO instruments look like someone aimed
a Gatling gun at them," commented NOAA's Gary Heckman. Click on the image for
a larger animation.
NOAA forecasters, using data from the Advanced Composition Explorer
(ACE), typically
can provide about one hour notice of prospective magnitude before
the start of a geomagnetic storm. But the July solar shower blinded
key ACE detectors. Without reliable data, scientists and forecasters
had to wait until Earth's magnetic field became distorted before
they knew that the disturbance had arrived.
A G5
geomagnetic storm - the most intense classification - raged for
nearly nine hours after the solar shower's impact.
The effects of the July storm were widespread. Cameras and star-tracking
navigation devices on several satellites were flooded with solar
particles. Measurements from particle detectors and other instruments
on several NOAA and NASA spacecraft were either degraded or temporarily
shut down. The Japanese Advanced Satellite for Cosmology and
Astrophysics (ASCA) was sent tumbling in orbit.
 Right:
Thirty-one hours after the "Bastille Day" coronal mass ejection left the Sun, the
disturbance hit our planet's magnetosphere and triggered a geomagnetic
storm. This image was captured by the Polar satellite at the
height of the storm. In this image captured by the Polar satellite,
false colors indicate the intensity of auroral activity. Notice
the large area over the United States, extending as far south
as Florida. This is a result of an exceptionally strong geomagnetic
storm; auroral activity is usually seen only at high latitudes.
Credit: NASA / University of Iowa
On the ground, auroral light shows were seen as far south as
El Paso, TX. Power companies suffered geomagnetically induced
currents that tripped capacitors and damaged at least one transformer.
Global positioning system (GPS) accuracy was degraded for several
hours. "The July event was a surprise to some of our customers,"
Hildner said. "They haven't seen this kind of activity for
nearly a decade."
A number of international spacecraft provided extensive data
and images showing the development and character of the July
event. "The next generation of solar missions will complement
and improve upon what scientists are learning from the existing
fleet, Withbroe said. "This will provide us with even more
capability to understand and ultimately predict solar weather
and its effect on Earth."
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