Some Solar Storms Start With a Twist

Snap! Magnetic twisting and tightening beneath the sun's surface can launch a giant solar flare.


Scientists have detected a consistent pattern in the sun's magnetic behavior that precedes solar flares. If the pattern can be unraveled completely, it could give hours or even days of warning to telecommunications companies, electric power grids, and satellite operators to prepare for these dangerous storms.

Solar flares threaten all of the artificial objects orbiting our planet, including GPS and telecommunications satellites, occupied spacecraft and the International Space Station. Every so often the sun emits a gigantic burst that includes highly energized x-rays, gamma rays, and charged particles. These surges can injure or even kill astronauts and fry electronic circuits. During such a burst, astronauts must rush to shielded compartments of their spacecraft, and technicians must scramble to place satellites in safe modes. Even on the ground, a large flare can overload power grids.

Because of the hazards and short lead times, for decades scientists have been trying to find reliable predictors of solar flares. Progress remained mostly stalled because of the seeming unpredictability of the events. Then in 2001 the Global Oscillation Network Group began operations. GONG comprises six ground-based observing sites that constantly monitor vibrations on the sun's surface for signs of activity deep within its interior.

A few years ago, some preliminary observations linked a solar flare to a large magnetic disturbance that seemed to have spiraled up from below the sun's surface. So a team of researchers examined data for 20 more big flares to determine if the same pattern preceded them. It did. The evidence showed a magnetic "twisting that started fast and slowly decreased to almost nothing as the flare occurred," says space scientist and lead author Alysha Reinard of the National Oceanic and Atmospheric Administration in Boulder, Colorado.

The team suggests in an upcoming paper in The Astrophysical Journal that the spirals result from subsurface turbulence in the sun's superhot gases--the equivalent of what happens on Earth when turbulent winds whip up tornadoes and hurricanes.

Reinard says the team has studied data from 1023 magnetic spirals that occurred between 2001 and 2007. In about one-third of the cases, she says, the magnetic vortices preceded a flare--sometimes up to 3 days before it erupted. But for unknown reasons, in the remaining cases the twisting did not presage a flare. Despite that uncertainty, she says, "We are confident that this is the breakthrough we need to understand why flares erupt and to be able to predict them."

The findings should provide some "interesting food for thought" for NASA's new Solar Dynamics Observatory mission, says space scientist Scott McIntosh of the National Center for Atmospheric Research, also in Boulder. The mission, which is scheduled to launch in a few weeks, is designed, among other tasks, to study the possible causes of solar flares, so it could help refine the data linking the vortices to the flares. "Exciting times are ahead," McIntosh says.