Dec 21, 2000

Watching the Angry Sun




Solar physicists are enjoying their best-ever look at a Solar Maximum thanks to NOAA and NASA satellites.


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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.


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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."



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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.


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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. .

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.


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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."


Web Links


NOAA Space Environment Center -- updates and forecasts of solar and geomagnetic activity -- news about solar activity, auroras, meteor showers, comets, and near-Earth asteroids

Solar and Heliospheric Observatory -- find out what the Sun looks like right now!


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