Magnetic Field Uses Sound Waves to Ignite Sun's Ring of Fire

    GREENBELT, Md., May 29 /PRNewswire-USNewswire/ -- Sound waves escaping
 the Sun's interior create fountains of hot gas that shape and power the
 chromosphere, a thin region of the sun's atmosphere which appears as a ruby
 red "ring of fire" around the moon during a total solar eclipse, according
 to research funded by NASA and the National Science Foundation (NSF). These
 results were presented May 29, at the American Astronomical Society Meeting
 in Honolulu, Hawaii.
     The chromosphere is important because it is largely responsible for the
 deep ultraviolet radiation that bathes the Earth, producing our
 atmosphere's ozone layer, and it has the strongest solar connection to
 climate variability. The new result also helps explain a mystery that's
 existed since the middle of the last century -- why the chromosphere (and
 the tenuous corona above) is much hotter than the visible surface of the
 star. "It's like getting warmer as you move away from the fire instead of
 cooler, certainly not what you expect," said Scott McIntosh, a researcher
 at Southwest Research Institute, Boulder, Colo.
     "This work finds the missing piece of the puzzle that has fascinated
 many generations of solar astronomers. When you fit this piece in place,
 our vision of the chromosphere becomes clear," said Alexei Pevtsov, Program
 Scientist NASA Headquarters, Washington.
     Using spacecraft, ground-based telescopes, and computer simulations,
 these new results show that the Sun's magnetic field allows the release of
 wave energy from its interior, permitting the sound waves to travel through
 thin fountains upward into the solar chromosphere. These magnetic fountains
 form the mold for the chromosphere.
     "Scientists have long realized that solar magnetic fields hold the key
 to tapping the vast energy reservoir locked in the Sun's interior," said
 Paul Bellaire, program director in NSF's division of atmospheric sciences.
 "These researchers have found the ingenious way that the Sun uses magnetic
 keys to pick those locks."
     Over the past twenty years, helioseismologists have studied energetic
 sound waves as probes of the Sun's interior structure because they are
 largely trapped by the Sun's visible surface -- the photosphere. The new
 research found that some of these waves can escape the photosphere into the
 chromosphere and corona.
     To make the new discovery, the team used observations from the SOHO and
 TRACE spacecrafts combined with those from the Magneto-Optical filters at
 Two Heights (MOTH) instrument stationed in Antarctica, and the Swedish 1
 meter (3 foot) Solar Telescope on the Canary Islands. The observations gave
 detailed insight into how some of these trapped waves manage to leak out
 through magnetic "cracks" in the photosphere, sending mass and energy
 shooting upwards into the atmosphere above. "The Sun's interior vibrates
 with the peal of millions of bells, but the bells are all on the inside of
 the building. We have been able to show how the sound can escape the
 building and travel a long way using the magnetic field as a guide,"
 continued McIntosh.
     By analyzing motions of structures in the solar atmosphere in detail,
 the scientists observed that near strong knots of magnetic field, sound
 waves from the interior of the Sun can leak out and propagate upward into
 its atmosphere. "The constantly evolving magnetic field above the solar
 surface acts like a doorman opening and closing the door for the waves that
 are constantly passing by," said Bart De Pontieu, a researcher Lockheed
 Martin Solar and Astrophysics Lab, Palo Alto, Calif.
     These results were confirmed by state-of-the-art computer simulations
 that show how the leaking waves continually propel fountains of hot gas
 upward into the Sun's atmosphere, which fall back to its surface a few
 minutes later.
     The scientists were able to independently demonstrate that the magnetic
 field controls the release of mass and wave energy into the solar
 atmosphere. The combination of these results demonstrates that a lot more
 energy can be pumped into the chromosphere by wave motions than researchers
 had previously thought. This wouldn't be possible without the relentlessly
 changing magnetic field at the surface.
     The research team includes Stuart Jefferies, University of Hawaii,
 Maui, Hawaii; Scott McIntosh, Southwest Research Institute, Boulder, Colo.;
 Bart De Pontieu, Lockheed Martin, Palo Alto, Calif.; and Viggo Hansteen,
 University of Oslo, Norway.
     For related images and more information, please visit on the Web:
 
    http://www.nasa.gov/vision/universe/solarsystem/ring_of_fire_media.html
 
     For information about the SOHO satellite, please visit on the Web:
 
                        http://sohowww.nascom.nasa.gov/
 
     For information about the TRACE satellite, please visit on the Web:
 
           http://sunland.gsfc.nasa.gov/smex/trace/mission/trace.htm
 
 

SOURCE NASA