The Sun's Magnetic Field is about to Flip   
       
   August 5, 2013:  Something big is about to happen on the sun.  According to   
   measurements from NASA-supported observatories, the sun's vast magnetic field   
   is about to flip.   
       
   "It looks like we're no more than 3 to 4 months away from a complete field   
   reversal," says solar physicist Todd Hoeksema of Stanford University. "This   
   change will have ripple effects throughout the solar system."   
       
   http://www.youtube.com/watch?v=34gNgaME86Y   
       
   A new ScienceCast video anticipates the reversal of the sun's global magnetic   
   field. Play it   
       
   The sun's magnetic field changes polarity approximately every 11 years.  It   
   happens at the peak of each solar cycle as the sun's inner magnetic dynamo   
   re-organizes itself.  The coming reversal will mark the midpoint of Solar   
   Cycle 24. Half of 'Solar Max' will be behind us, with half yet to come.   
       
   Hoeksema is the director of Stanford's Wilcox Solar Observatory, one of the   
   few observatories in the world that monitor the sun's polar magnetic fields.    
   The poles are a herald of change. Just as Earth scientists watch our planet's   
   polar regions for signs of climate change, solar physicists do the same thing   
   for the sun. Magnetograms at Wilcox have been tracking the sun's polar   
   magnetism since 1976, and they have recorded three grand reversals-with a   
   fourth in the offing.   
       
   http://wso.stanford.edu/   
       
   Astronomers at the Wilcox Solar Observatory (WSO) monitor the sun's global   
   magnetic field on a daily basis. WSO home pageSolar physicist Phil Scherrer,   
   also at Stanford, describes what happens: "The sun's polar magnetic fields   
   weaken, go to zero, and then emerge again with the opposite polarity. This is   
   a regular part of the solar cycle."   
       
   A reversal of the sun's magnetic field is, literally, a big event. The domain   
   of the sun's magnetic influence (also known as the "heliosphere") extends   
   billions of kilometers beyond Pluto. Changes to the field's polarity ripple   
   all the way out to the Voyager probes, on the doorstep of interstellar space.   
       
   When solar physicists talk about solar field reversals, their conversation   
   often centers on the "current sheet."  The current sheet is a sprawling   
   surface jutting outward from the sun's equator where the sun's slowly-rotating   
   magnetic field induces an electrical current.  The current itself is small,   
   only one ten-billionth of an amp per square meter (0.0000000001 amps/m2), but   
   there's a lot of it: the amperage flows through a region 10,000 km thick and   
   billions of kilometers wide.  Electrically speaking, the entire heliosphere is   
   organized around this enormous sheet.   
       
   During field reversals, the current sheet becomes very wavy. Scherrer likens   
   the undulations to the seams on a baseball.  As Earth orbits the sun, we dip   
   in and out of the current sheet. Transitions from one side to another can stir   
   up stormy space weather around our planet.   
       
   http://wso.stanford.edu/gifs/HCS.html   
       
   An artist's concept of the heliospheric current sheet, which becomes more wavy   
   when the sun's magnetic field flips. MoreCosmic rays are also affected. These   
   are high-energy particles accelerated to nearly light speed by supernova   
   explosions and other violent events in the galaxy.  Cosmic rays are a danger   
   to astronauts and space probes, and some researchers say they might affect the   
   cloudiness and climate of Earth. The current sheet acts as a barrier to cosmic   
   rays, deflecting them as they attempt to penetrate the inner solar system. A   
   wavy, crinkly sheet acts as a better shield against these energetic particles   
   from deep space.   
       
   As the field reversal approaches, data from Wilcox show that the sun's two   
   hemispheres are out of synch.   
       
   "The sun's north pole has already changed sign, while the south pole is racing   
   to catch up," says Scherrer. "Soon, however, both poles will be reversed, and   
   the second half of Solar Max will be underway."   
       
   When that happens, Hoeksema and Scherrer will share the news with their   
   colleagues and the public.   
       
   Stay tuned to Science@NASA for updates.   
       
   Credits:   
       
   Author:Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More information:   
       
   Is Solar Max Double-Peaked?  -- ScienceCast video   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.94   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)