Sunspot Breakthrough   
       
   August 25, 2011: Imagine forecasting a hurricane in Miami weeks before the   
   storm was even a swirl of clouds off the coast of Africa-or predicting a   
   tornado in Kansas from the flutter of a butterfly's wing1 in Texas. These are   
   the kind of forecasts meteorologists can only dream about.   
       
   Could the dream come true? A new study by Stanford researchers suggests that   
   such forecasts may one day be possible-not on Earth, but on the sun.   
       
   "We have learned to detect sunspots before they are visible to the human eye,"   
   says Stathis Ilonidis, a PhD student at Stanford University. "This could lead   
   to significant advances in space weather forecasting."   
       
   Sunspots are the "butterfly's wings" of solar storms. Visible to the human eye   
   as dark blemishes on the solar disk, sunspots are the starting points of   
   explosive flares and coronal mass ejections (CMEs) that sometimes hit our   
   planet 93 million miles away. Consequences range from Northern Lights to radio   
   blackouts to power outages.   
       
   http://science.nasa.gov/media/medialibrary/2011/08/25/ar1158.mp4   
       
   Based on data from the Solar Dynamics Observatory, this movie shows a sunspot   
   emerging from depth in February 2011. Visualization credit: Thomas Hartlep and   
   Scott Winegarden, Stanford University. [video] [more]   
   Astronomers have been studying sunspots for more than 400 years, and they have   
   pieced together their basic characteristics: Sunspots are planet-sized islands   
   of magnetism that float in solar plasma. Although the details are still   
   debated, researchers generally agree that sunspots are born deep inside the   
   sun via the action of the sun's inner magnetic dynamo. From there they bob to   
   the top, carried upward by magnetic buoyancy; a sunspot emerging at the   
   stellar surface is a bit like a submarine emerging from the ocean depths.     
   http://science.nasa.gov/media/medialibrary/2011/08/25/ar488.mp4   
       
   In the August 19th issue of Science, Ilonidis and co-workers Junwei Zhao and   
   Alexander Kosovichev announced that they can see some sunspots while they are   
   still submerged.   
       
   Their analysis technique is called "time-distance helioseismology2," and it is   
   similar to an approach widely used in earthquake studies. Just as seismic   
   waves traveling through the body of Earth reveal what is inside the planet,   
   acoustic waves traveling through the body of the sun can reveal what is inside   
   the star. Fortunately for helioseismologists, the sun has acoustic waves in   
   abundance. The body of the sun is literally roaring with turbulent boiling   
   motions. This sets the stage for early detection of sunspots.   
       
   "We can't actually hear these sounds across the gulf of space," explains   
   Ilonidis, "but we can see the vibrations they make on the sun's surface."   
   Instruments onboard two spacecraft, the venerable Solar and Heliospheric   
   Observatory (SOHO) and the newer Solar Dynamics Observatory (SDO) constantly   
   monitor the sun for acoustic activity.   
       
   False-colors in this SOHO movie represent acoustic travel-time differences   
   heralding a sunspot as it rises toward the sun's surface in October 2003.   
   Visualization credit: Thomas Hartlep, Stanford University. [video] [more]   
   Submerged sunspots have a detectable effect on the sun's inner a   
   oustics-namely, sound waves travel faster through a sunspot than through the   
   surrounding plasma. A big sunspot can leapfrog an acoustic wave by 12 to 16   
   seconds. "By measuring these time differences, we can find the hidden sunspot."   
       
   Ilonidis says the technique seems to be most sensitive to sunspots located   
   about 60,000 km beneath the sun's surface. The team isn't sure why that is   
   "the magic distance," but it's a good distance because it gives them as much   
   as two days advance notice that a spot is about to reach the surface.   
       
   "This is the first time anyone has been able to point to a blank patch of sun   
   and say 'a sunspot is about to appear right there,'" says Ilonidis's thesis   
   advisor Prof. Phil Scherrer of the Stanford Physics Department. "It's a big   
   advance."   
       
   "There are limits to the technique," cautions Ilonidis. "We can say that a big   
   sunspot is coming, but we cannot yet predict if a particular sunspot will   
   produce an Earth-directed flare."   
       
   So far they have detected five emerging sunspots-four with SOHO and one with   
   SDO. Of those five, two went on to produce X-class flares, the most powerful   
   kind of solar explosion. This encourages the team to believe their technique   
   can make a positive contribution to space weather forecasting. Because   
   helioseismology is computationally intensive, regular monitoring of the whole   
   sun is not yet possible-"we don't have enough CPU cycles," says Ilonidis -but   
   he believes it is just a matter of time before refinements in their algorithm   
   allow routine detection of hidden sunspots.   
       
   The original research reported in this story may be found in Science magazine:   
   "Detection of Emerging Sunspot Regions in the Solar Interior" by Ilonidis,   
   Zhao and Kosovichev, 333 (6045): 993-996.   
       
       
   Author: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Footnotes:   
       
   (1) The Butterfly Effect   
       
   (2) Time-distance helioseismology was originally developed by NASA scientist   
   Thomas Duvall in 1993   
       
   Credits: SOHO, a joint project by NASA and European Space Agency, was launched   
   in December 1995 and is still under operation. SDO is a NASA mission and was   
   launched in February 2010. Prof. Scherrer, adviser of Stathis Ilonidis, is the   
   Principal Investigator of both MDI onboard SOHO, and HMI onboard SDO. Data   
   observed by both MDI and HMI were used in this study.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.64   
    * Origin: NCS BBS (1:3828/7)