Global Eruption Rocks the Sun   
       
   Dec. 13, 2010:  On August 1, 2010, an entire hemisphere of the sun erupted.   
   Filaments of magnetism snapped and exploded, shock waves raced across the   
   stellar surface, billion-ton clouds of hot gas billowed into space.   
   Astronomers knew they had witnessed something big.   
       
   It was so big, it may have shattered old ideas about solar activity.   
       
   "The August 1st event really opened our eyes," says Karel Schrijver of   
   Lockheed Martin's Solar and Astrophysics Lab in Palo Alto, CA. "We see that   
   solar storms can be global events, playing out on scales we scarcely imagined   
   before."   
       
   Click to play an extreme ultraviolet movie of the August 1st global eruption.   
   Different colors represent different plasma temperatures in the range 1.0 to   
   2.2 million K. Credit: Solar Dynamics Observatory.   
       
   URL:   
       
   http://science.nasa.gov/media/medialibrary/2010/12/13/globaldisruption.mov   
       
   [JEEZ!]   
       
   For the past three months, Schrijver has been working with fellow   
   Lockheed-Martin solar physicist Alan Title to understand what happened during   
   the "Great Eruption." They had plenty of data: The event was recorded in   
   unprecedented detail by NASA's Solar Dynamics Observatory and twin STEREO   
   spacecraft. With several colleagues present to offer commentary, they outlined   
   their findings at a press conference today at the American Geophysical Union   
   meeting in San Francisco.   
       
   Explosions on the sun are not localized or isolated events, they announced.   
   Instead, solar activity is interconnected by magnetism over breathtaking   
   distances. Solar flares, tsunamis, coronal mass ejections--they can go off all   
   at once, hundreds of thousands of miles apart, in a dizzyingly-complex concert   
   of mayhem.   
   [...]   
   NASA's twin STEREO spacecraft surround the sun. [STEREO home page] "To predict   
   eruptions we can no longer focus on the magnetic fields of isolated active   
   regions," says Title, "we have to know the surface magnetic field of   
   practically the entire sun."   
       
   This revelation increases the work load for space weather forecasters, but it   
   also increases the potential accuracy of their forecasts.   
       
   "The whole-sun approach could lead to breakthroughs in predicting solar   
   activity," commented Rodney Viereck of NOAA's Space Weather Prediction Center   
   in Boulder, CO. "This in turn would provide improved forecasts to our   
   customers such as electric power grid operators and commercial airlines, who   
   could take action to protect their systems and ensure the safety of passengers   
   and crew."   
       
   In a paper they prepared for the Journal of Geophysical Research (JGR),   
   Schrijver and Title broke down the Great Eruption into more than a dozen   
   significant shock waves, flares, filament eruptions, and CMEs spanning 180   
   degrees of solar longitude and 28 hours of time. At first it seemed to be a   
   cacophony of disorder until they plotted the events on a map of the sun's   
   magnetic field.   
       
   Title describes the Eureka! moment: "We saw that all the events of substantial   
   coronal activity were connected by a wide-ranging system of separatrices,   
   separators, and quasi-separatrix layers." A "separatrix" is a magnetic fault   
   zone where small changes in surrounding plasma currents can set off big   
   electromagnetic storms.   
   [...]   
   Locations of key events are labeled in this extreme ultraviolet image of the   
   sun, obtained by the Solar Dynamics Observatory during the Great Eruption of   
   August 1st. White lines trace the sun's magnetic field. Credit: K Schrijver &   
   A. Title. [larger image]   
       
   Researchers have long suspected this kind of magnetic connection was possible.   
   "The notion of 'sympathetic' flares goes back at least three quarters of a   
   century," they wrote in their JGR paper. Sometimes observers would see flares   
   going off one after another--like popcorn--but it was impossible to prove a   
   link between them. Arguments in favor of cause and effect were statistical and   
   often full of doubt.   
       
   "For this kind of work, SDO and STEREO are game-changers," says Lika   
   Guhathakurta, NASA's Living with a Star Program Scientist. "Together, the   
   three spacecraft monitor 97% of the sun, allowing researchers to see   
   connections that they could only guess at in the past."   
   [...]   
   An artist's concept of the Solar Dynamics Observatory. [SDO home page] To wit,   
   barely two-thirds of the August event was visible from Earth, yet all of it   
   could be seen by the SDO-STEREO fleet. Moreover, SDO's measurements of the   
   sun's magnetic field revealed direct connections between the various   
   components of the Great Eruption-no statistics required.   
       
   Much remains to be done. "We're still sorting out cause and effect," says   
   Schrijver. "Was the event one big chain reaction, in which one eruption   
   triggered another--bang, bang, bang--in sequence? Or did everything go off   
   together as a consequence of some greater change in the sun's global magnetic   
   field?"   
       
   Further analysis may yet reveal the underlying trigger; for now, the team is   
   still wrapping their minds around the global character of solar activity. One   
   commentator recalled the old adage of three blind men describing an   
   elephant--one by feeling the trunk, one by holding the tail, and another by   
   sniffing a toenail. Studying the sun one sunspot at a time may be just as   
   limiting.   
       
   "Not all eruptions are going to be global," notes Guhathakurta. "But the   
   global character of solar activity can no longer be ignored."   
       
   As if the sun wasn't big enough already..   
       
       
   Author: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Solar Dynamics Observatory -- SDO home page   
       
   Solar Terrestrial Relations Observatory -- STEREO home page   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.58   
    * Origin: NCS BBS (1:3828/7)