Parting shots: just as the sun was calming down, it flared with a vengeance

Science News, July 31, 2004 by Sid Perkins

SOHO instruments, for example, directly measure the speed and strength of clouds of charged particles headed for Earth, providing researchers with early warnings of approaching space storms. The Space Environment Center, operated in Boulder, Colo., by NOAA and the U.S. Air Force, was particularly busy last fall distributing warnings worldwide about the solar disturbances that had the potential to affect people, satellites, and infrastructure.

The swarms of charged particles spewing from the sun generally travel along the sun's magnetic field lines. The sun's rotation, which takes 27 days, makes these lines curve through space like water from a spinning sprinkler. The coronal mass ejections most likely to smack Earth originate from solar longitudes between 10[degrees] and 50[degrees] west of the sun's center, says Woods. Flares typically lift straight off the solar surface, so scientists can roughly estimate where they're headed, but accuracy plummets when, for instance, the shock waves from several flares interact with each other.

To better predict space weather, researchers have developed a technique to quickly characterize fresh coronal mass ejections. Using three or more satellite images of the flare's cloud of charged particles taken through a polarizing filter, which can be rotated to different angles to block waves of light along different directions, scientists construct a three-dimensional image of the flare and estimate its speed and direction. Collecting the data and producing the image take just a few minutes, says Thomas G. Moran, a solar physicist at NASA'S Goddard Space Flight Center in Greenbelt, Md. He and Joseph M. Davila of the Catholic University of America in Washington, D.C., describe the technique in the July 2 Science.

Previous techniques for analyzing coronal mass ejections sometimes failed or were too slow, says John C. Raymond, an astrophysicist at Harvard University. Besides providing scientists with a better idea of when clouds of charged particles will arrive at Earth, the new 3-D views of solar flares could contribute to models of how solar flares behave, he notes.

Many other new visualization techniques could result from a European search for better ways to monitor, simulate, and predict space weather. By coincidence, that 17-nation, 4-year program was lannched just as last fall's barrage of superflares waned.