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Lundi, 13 Décembre 2010 23:05

Video: Explosions Connected Across Sun's Surface

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SAN FRANCISCO — Dramatic explosions from the surface of the sun can link up across hundreds of thousands of miles. New views from three different NASA spacecraft show how near-simultaneous eruptions on opposite sides of the

sun can connect through looping lines of magnetic force.

Solar scientists have suspected for decades that solar flares, sudden bursts of energy that erupt from sunspots, and coronal mass ejections, bubbles of gas threaded with lines of magnetic field that throw tons of solar plasma out into space when they explode, could be connected across great distances. So-called sympathetic flares that went off one after another had been observed for 75 years. But how the flares could link together was a mystery.

New videos of a recent eruption that crossed nearly the entire sun could solve the puzzle. On August 1, a chain of more than a dozen flares and other eruptions cascaded across the surface of the sun. Much of the show was hidden from Earth, but it was all captured by NASA’s Solar Dynamics Observatory (above) and twin STEREO spacecraft.

“We had to be beaten over the head, which is what the August events did,” said Alan Title, a solar physicist at Lockheed Martin’s Solar and Astrophysics Lab, here in a press conference at the American Geophysical Union meeting Dec. 13. “Once you see something like this, the things you saw in the past all fall into place.”

Based on observations from SDO, Title and solar physicist Karel Schrijver of Lockheed Martin built a model of how lines of magnetic field changes on the sun from day to day. They found that a far-reaching network of magnetic field lines connected one region to another, even across the entire 860,000-mile diameter of the sun (video below).

“For years, solar physicists including ourselves have been looking for the cause of these explosions in the region that’s exploding,” Schrijver said. The new observations show that “we need to expand our view and look well beyond the region exploding.”

When flares and coronal mass ejections erupt on the sun, they can blast Earth with bursts of X-rays and plasma that can shut down power grids, knock out satellites and make airplanes lose communication. Solar physicists are working to predict such damaging flares before they happen, but so far models have been built “by the seat of the pants,” said Rodney Viereck of NOAA’s Space Weather Prediction Center. The new global view of the sun could help improve space weather forecasting models.

“These observations have provided forecasters with more detail than they’ve ever had before,” Viereck said.

Video: 1) Lockheed Martin’s Solar and Astrophysics Laboratory. 2) SDO/AIA

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Authors: Lisa Grossman

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