Call it the ultimate solar fake-out: A new study has found that when storms rage on the sun, they don't always shoot out in a straight line, but actually switch directions.
"This really surprised us," wrote researcher Peter Gallagher of Trinity College in Dublin, Ireland. "Solar coronal mass ejections (CMEs) can start out going one way — and then turn in a different direction."
Scientists made the discovery using NASA's twin Stereo spacecraft, which are studying the sun to unravel the 3-D structure of solar storms.
The result was so surprising that researchers initially thought they'd made a mistake. But after triple-checking their calculations on dozens of solar eruptions, the team arrived at the same conclusion.
"Our 3-D visualizations clearly show that solar storms can be deflected from high solar latitudes and end up hitting planets they might otherwise have missed," said study leader Jason Byrne, a graduate student at the Trinity Center for High Performance Computing.
Wayward solar storms that try to head out of the plane of the solar system seem to be guided by the sun's global magnetic field, which is shaped like a bar magnet, back in line with the sun's equator, researchers said.
Stereo-A and Stereo–B are two spacecraft that provide a view of solar flares from different points of view. Stereo-A is watching the sun from a point in Earth's orbit ahead of our planet, while Stereo B is trailing behind.
This allowed the team to create fully stereoscopic models of the storm's particle clouds and track them as they billowed away from the sun. The researchers used an innovative computing technique called multiscale image processing, which sorts through objects in an image according to their size.
In medical research, multiscale processing has been used to identify individual nuclei in crowded pictures of cells. In astronomy, it comes in handy for picking galaxies out of a busy star field. Gallagher and colleagues are the first to refine and use it in the realm of solar physics.
The research is detailed in the Sept. 21 issue of the journal Nature Communications.
Studies from past missions revealed tantalizing hints of this solar storm redirection process, but the Stereo spacecraft are the first to see it unfold from nearly beginning to end. ("Stereo" stands for Solar Terrestrial Relations Observatory.)
"The ability to reconstruct the path of a solar storm through space could be of great benefit to forecasters of space weather at Earth," said Alex Young, Stereo senior scientist at NASA's Goddard Space Flight Center. "Knowing when a CME will arrive is crucial for predicting the onset of geomagnetic storms."