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Scientists Find Key for Forecasting Solar Storms

Posted on: Wednesday, 17 August 2005, 09:00 CDT

Scientists find key for forecasting solar storms

LOS ANGELES, Aug. 16 (Xinhua) -- A new study revealing previously unknown aspects to solar eruptions may lead to better understanding of solar storms and more reliable forecasts for space weather, scientists reported on Tuesday.

Solar forecasts are important because radiation from particles from the sun associated with large solar flares can be hazardous to unprotected astronauts, airplane occupants and satellites, said Karel Schrijver of the Lockheed Martin Advanced Technology Center, lead author of a paper published in the Astrophysical Journal.

While researchers have learned much about the Sun's temper in recent years relying on new data from satellites that keep a constant eye on the situation, many mysteries remain and forecasts are only about as reliable as weather predictions were in the 1950s, experts said.

But the new study has made big strides in learning how to forecast "all clear" periods, when severe space weather is unlikely, said Schrijver.

Solar flares are violent explosions in the atmosphere of the sun caused by the sudden release of magnetic energy. Like a rubber band twisted too tightly, stressed magnetic fields in the sun's atmosphere can suddenly snap to a new shape. They can release as much energy as one 10-billion-megaton nuclear bomb.

Probe into the causes of the largest solar flares came in two steps, the researchers said.

"First, we discovered characteristic patterns of magnetic field evolution associated with strong electrical currents in the solar atmosphere," said Schrijver. "It is these strong electrical currents that drive solar flares."

Then the researchers discovered the regions most likely to flare had new magnetic fields merge into them that were clearly out of alignment with the existing field.

This emerging field from the solar interior appears to induce even more current as it interacts with the existing field.

They also found flares do not necessarily occur immediately upon the emergence of a new magnetic field. Apparently the electrical currents must build up over several hours before the fireworks start.

Solar flares will happen just like avalanches, which occur only after enough snow built up. Once the threshold is reached, the avalanche can happen anytime by processes not yet completely understood, said the researchers.

"We found the current-carrying regions flare two to three times more often than the regions without large currents," Schrijver said. "Also, the average flare magnitude is three times greater for the group of active regions with large current systems than for the other group."

The researchers made the discovery by comparing data about magnetic fields on the sun's surface to the sharpest extreme- ultraviolet images of the solar corona. They also used computer models of a three-dimensional solar magnetic field. Differences between images and models indicated the presence of large electrical currents.

This result is "not only interesting scientifically, but has broad implications for society," commented Dick Fisher, head of NASA's solar study section.

Source: Xinhua News Agency - CEIS

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