Solar Wind Energy Source Discovered   
       
   March 8, 2013: Using data from an aging NASA spacecraft, researchers have   
   found signs of an energy source in the solar wind that has caught the   
   attention of fusion researchers. NASA will be able to test the theory later   
   this decade when it sends a new probe into the sun for a closer look.   
       
   The discovery was made by a group of astronomers trying to solve a decades-old   
   mystery: What heats and accelerates the solar wind?   
       
   http://solarscience.msfc.nasa.gov/SolarWind.shtml   
       
   Solar wind flows away from the sun at speeds up to and exceeding 500 km/s (a   
   million mph). MoreThe solar wind is a hot and fast flow of magnetized gas that   
   streams away from the sun's upper atmosphere.  It is made of hydrogen and   
   helium ions with a sprinkling of heavier elements.  Researchers liken it to   
   the steam from a pot of water boiling on a stove; the sun is literally boiling   
   itself away.   
       
   "But," says Adam Szabo of the NASA Goddard Space Flight Center, "solar wind   
   does something that steam in your kitchen never does.  As steam rises from a   
   pot, it slows and cools.  As solar wind leaves the sun, it accelerates,   
   tripling in speed as it passes through the corona. Furthermore, something   
   inside the solar wind continues to add heat even as it blows into the cold of   
   space."   
       
   Finding that "something" has been a goal of researchers for decades.  In the   
   1970s and 80s, observations by two German/US Helios spacecraft set the stage   
   for early theories, which usually included some mixture of plasma   
   instabilities, magnetohydrodynamic waves, and turbulent heating.  Narrowing   
   down the possibilities was a challenge. The answer, it turns out, has been   
   hiding in a dataset from one of NASA's oldest active spacecraft, a solar probe   
   named Wind.   
       
   Launched in 1994, Wind is so old that it uses magnetic tapes similar to   
   old-fashioned 8-track tapes to record and play back its data.  Equipped with   
   heavy shielding and double-redundant systems to safeguard against failure, the   
   spacecraft was built to last; at least one researcher at NASA calls it the   
   "Battlestar Gallactica" of the heliophysics fleet. Wind has survived almost   
   two complete solar cycles and innumerable solar flares.   
       
   "After all these years, Wind is still sending us excellent data," says Szabo,   
   the mission's project scientist, "and it still has 60 years' worth of fuel   
   left in its tanks."   
       
   http://science.nasa.gov/media/medialibrary/2013/03/08/splash_big.jpg   
       
   An artist's concept of the Wind spacecraft sampling the solar wind. Justin   
   Kasper's science result is inset. [larger image]   
   Using Wind to unravel the mystery was, to Justin Kasper of the H   
   rvard-Smithsonian Center for Astrophysics, a "no brainer." He and his team   
   processed the spacecraft's entire 19-year record of solar wind temperatures,   
   magnetic field and energy readings and ...   
       
   "I think we found it," he says.  "The source of the heating in the solar wind   
   is ion cyclotron waves."   
       
   Ion cyclotron waves are made of protons that circle in wavelike-rhythms around   
   the sun's magnetic field.  According to a theory developed by Phil Isenberg   
   (University of New Hampshire) and expanded by Vitaly Galinsky and Valentin   
   Shevchenko (UC San Diego), ion cyclotron waves emanate from the sun; coursing   
   through the solar wind, they heat the gas to millions of degrees and   
   accelerate its flow to millions of miles per hour. Kasper's findings confirm   
   that ion cyclotron waves are indeed active, at least in the vicinity of Earth   
   where the Wind probe operates.   
       
   Ion cyclotron waves can do much more than heat and accelerate the solar wind,   
   notes Kasper.  "They also account for some of the wind's very strange   
   properties."   
       
   The solar wind is not like wind on Earth.  Here on Earth, atmospheric winds   
   carry nitrogen, oxygen, water vapor along together; all species move with the   
   same speed and they have the same temperature.  The solar wind, however, is   
   much stranger.  Chemical elements of the solar wind such as hydrogen, helium,   
   and heavier ions, blow at different speeds; they have different temperatures;   
   and, strangest of all, the temperatures change with direction.   
       
   "We have long wondered why heavier elements in the solar wind move faster and   
   have higher temperatures than the lighter elements," says Kasper.  "This is   
   completely counterintuitive."   
       
   The ion cyclotron theory explains it: Heavy ions resonate well with ion   
   cyclotron waves. Compared to their lighter counterparts, they gain more energy   
   and heat as they surf.   
       
       
   An artist's concept of Solar Probe Plus approaching the sun where it can test   
   the ion cyclotron theory. MoreThe behavior of heavy ions in the solar wind is   
   what intrigues fusion researchers. Kasper explains: "When you look at fusion   
   reactors on Earth, one of the big challenges is contamination. Heavy ions that   
   sputter off the metal walls of the fusion chamber get into the plasma where   
   the fusion takes place.  Heavy ions radiate heat. This can cool the plasma so   
   much that it shuts down the fusion reaction."   
       
   Ion cyclotron waves of the type Kasper has found in the solar wind might   
   provide a way to reverse this process. Theoretically, they could be used to   
   heat and/or remove the heavy ions, restoring thermal balance to the fusing   
   plasma.   
       
   "I have been invited to several fusion conferences to talk about our work with   
   the solar wind," he says.   
       
   The next step, agree Kasper and Szabo, is to find out if ion cyclotron waves   
   work the same way deep inside the sun's atmosphere where the solar wind begins   
   its journey.  To find out, NASA is planning to send a spacecraft into the sun   
   itself.   
       
   Solar Probe Plus, scheduled for launch in 2018, will plunge so far into the   
   sun's atmosphere that the sun will appear as much as 23 times wider than it   
   does in the skies of Earth. At closest approach, about 7 million km from the   
   sun's surface, Solar Probe Plus must withstand temperatures greater than 1400   
   deg. C and survive blasts of radiation at levels not experienced by any   
   previous spacecraft.  The mission's goal is to sample the sun's plasma and   
   magnetic field at the very source of the solar wind.   
       
   "With Solar Probe Plus we'll be able to conduct specific tests of the ion   
   cyclotron theory using sensors far more advanced than the ones on the Wind   
   spacecraft," says Kasper.  "This should give us a much deeper understanding of   
   the solar wind's energy source."   
       
   The research described in this story was published in the Physical Review   
   Letters on February 28, 2013: "Sensitive Test for Ion-Cyclotron Resonant   
   Heating in the Solar Wind" by Justin Kasper et al.   
       
       
   Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.9   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)