Originally created 05/12/02

Solar storms hit close to home



New NASA satellite images are giving scientists a better understanding of how Earth's outer atmosphere protects the planet during solar storms but also gets superheated and charged to produce disruptive electrical fields.

"The atmosphere shields us from the most damaging effects of space storms, but the Earth pays a price for these events, too," Richard Fisher, director of NASA's Sun-Earth Connection program, said Thursday at a news conference in Washington to announce the findings.

"In the past, there's been an impression that Earth was a bystander to these storms, but these results show that our planet is a much more active participant and supplies much of the material that produces adverse effects," said Stephen Fuselier, manager of the space physics lab at Lockheed-Martin Advanced Techology Center in Palo Alto, Calif. He is lead author of one of two new papers on results from the National Aeronautics and Space Administration's IMAGE (Imager for Magnetopause to Aurora Global Exploration) spacecraft.

Although the sun provides the energy, some of Earth's own oxygen gets supercharged to a point that it can disrupt satellites, radio communication, even send damaging surges through power lines and pipelines on the ground.

Solar wind, a high-velocity mix of charged particles, blows constantly from the sun at average speeds of 250 miles a second, but faster when eruptions occur from our star. Most of this energy is diverted by Earth's magnetic field, but some gets through to strike electrically charged atoms in the outer layer of our atmosphere, 180 to 620 miles high.

And during storms, a small fraction of that upper atmosphere gets blasted into outer space.

"Just as a heat shield sacrifices itself by allowing its outer layers to slough off during the fiery re-entry of a spacecraft, Earth's shield absorbs space-storm energy by throwing some of its charged particles into space," said Fuselier.

"We're talking about a very small part of the atmosphere, about 100 million tons of oxygen, or about the volume inside the Louisiana Superdome," he added.

Even then, most of those expelled particles are trapped by Earth's magnetic field, and eventually form a hot plasma cloud around the planet, said Donald Mitchell, a physicist at the Johns Hopkins Applied Physics Laboratory in Laurel, Md., lead author of a second study.

His team found that the oxygen particles ejected into space return 100,000 times more energized, generating a multimillion-amp electric current that flows along Earth's invisible magnetic field lines and causes phenomena like the aurora (northern and southern lights) to form.

In fact, all this energy actually helps distort Earth's magnetic field on the side of the planet away from the sun into a millions-mile-long tail, which eventually stretches out so far that it snaps back like a rubber band, acting like an enormous slingshot.

"So even though most of the material is lost into space, the energy content of what comes back is a lot greater than what went out originally, and it makes quite a splash that can affect so much of our technology on the ground and in space," Fuselier said.

John Foster, associate director of the Massachusetts Institute of Technology's Haystack Observatory, said his team was able to match up some of the data on a March 2001 solar storm collected by the IMAGE spacecraft with ground observations taken by a series of stations tuned to the Global Positioning Satellite navigation system.

"We mapped a region of radio disturbance from this event that stretched from Washington, D.C., into Canada," Foster said. "This kind of situation, if the disturbance is strong enough, could have serious implications for everyone from the hiker out in the mountains to commercial pilots."

The scientists said the new images will help them and others develop new models to forecast the severity and impact of space storms.

"Just as we use images from satellites to predict weather on the ground, the IMAGE spacecraft is our first weather satellite for the geosphere," said Janet Kozyra, a research scientist at the University of Michigan.

On the Net:

http://www.gsfc.nasa.gov/



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