Solar Storms can Change Directions, Surprising Forecasters   
       
   Sept. 21, 2010:  Solar storms don't always travel in a straight line. But once   
   they start heading in our direction, they can accelerate rapidly, gathering   
   steam for a harder hit on Earth's magnetic field.   
       
   So say researchers who have been using data from NASA's twin STEREO spacecraft   
   to unravel the 3D structure of solar storms. Their findings are presented in   
   today's issue of Nature Communications.   
   [...]   
   A coronal mass ejection (CME) observed by STEREO on Dec. 12, 2008. [larger   
   image]   
       
   "This really surprised us," says co-author 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."   
       
   The result was so strange, at first they thought they'd done something wrong.   
   After double- and triple-checking their work on dozens of eruptions, however,   
   the team knew they were onto something.   
       
   "Our 3D visualizations clearly show that solar storms can be deflected from   
   high solar latitudes and end up hitting planets they might otherwise have   
   missed," says lead author Jason Byrne, a graduate student at the Trinity   
   Center for High Performance Computing.   
   [...]   
   A 3D model of an actual CME based on multiscale processing of STEREO data.   
   [9MB movie] The key to their analysis was an innovative computing technique   
   called "multiscale image processing." Gallagher explains:   
       
   "'Multiscale processing' means taking an image and sorting the things in it   
   according to size. Suppose you're interested in race cars. If you have a photo   
   that contains a bowl of fruit, a person, and a dragster, you could use   
   multiscale processing to single out the race car and study its c   
   aracteristics."   
       
   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.   
       
   "We applied the multiscale technique to coronagraph data from NASA's twin   
   STEREO spacecraft," Gallagher continues. "Our computer was able to look at   
   starry images cluttered with streamers and bright knots of solar wind and zero   
   in on the CMEs."   
       
   STEREO-A and STEREO-B are widely separated and can see CMEs from different   
   points of view. This allowed the team to create fully-stereoscopic models of   
   the storm clouds and track them as they billowed away from the sun.   
       
   One of the first things they noticed was how CMEs trying to go "up"-out of the   
   plane of the solar system and away from the planets-are turned back down   
   again. Gallagher confesses that they had to "crack the books" and spend some   
   time at the white board to fully understand the phenomenon. In the end, the   
   explanation was simple:   
   [...]   
   The magnetic field of a bar magnet. The sun's global magnetic field, which is   
   shaped like a bar magnet, guides the wayward CMEs back toward the sun's   
   equator. When the clouds reach low latitudes, they get caught up in the solar   
   wind and head out toward the planets-"like a cork bobbing along a river," says   
   Gallagher.   
       
   Once a CME is embedded in the solar wind, it can experience significant   
   acceleration. "This is a result of aerodynamic drag," says Byrne. "If the wind   
   is blowing fast enough, it drags the CME along with it-something we actually   
   observed in the STEREO data."   
       
   Past studies from other missions had revealed tantalizing hints of this   
   CME-redirection and acceleration process, but STEREO is the first to see it   
   unfold from nearly beginning to end.   
       
   "The ability to reconstruct the path of a solar storm through space could be   
   of great benefit to forecasters of space weather at Earth," notes Alex Young,   
   STEREO Senior Scientist at the Goddard Space Flight Center. "Knowing when a   
   CME will arrive is crucial for predicting the onset of geomagnetic storms."   
       
   "Furthermore," he says, "the image processing techniques developed by the   
   Trinity team in collaboration with NASA Goddard can be used in applications   
   ranging from surveillance to medical diagnostics."   
       
   To learn more about zig-zagging CMEs and the advanced computing techniques   
   used to track them, read "Propagation of an Earth-directed coronal mass   
   ejection in three dimensions" by Byrne et al in the Sept. 21, 2010, issue of   
   Nature Communications.   
       
       
   Author: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   STEREO -- Solar Terrestrial Relations Observatory home page   
       
   School of Physics, Trinity College, Dublin   
       
   Trinity Centre for High Performance Computing   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.55   
    * Origin: NCS BBS (1:3828/7)