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Posted by baalke on September 3, 2007, 8:24 pm
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http://www.ucar.edu/news/releases/2007/solar.shtml
News Release
Scientists Find Elusive Waves in Sun's Corona;
Discovery Can Help Unlock Secrets of Corona's Heat, Solar Storms
August 30, 2007
BOULDER - Scientists for the first time have observed
elusive oscillations in the Sun's corona, known as Alfv=E9n waves, that
transport energy outward from the surface of the Sun. The discovery is
expected to give researchers more insight into the fundamental
behavior
of solar magnetic fields, eventually leading to a fuller understanding
of how the Sun affects Earth and the solar system.
The research, led by Steve Tomczyk of the National Center for
Atmospheric Research (NCAR), is being published this week in Science.
"Alfv=E9n waves can provide us with a window into processes that are
fundamental to the workings of the Sun and its impacts on Earth," says
Tomczyk, a scientist with NCAR's High Altitude Observatory.
Alfv=E9n waves are fast-moving perturbations that emanate outward from
the
Sun along magnetic field lines, transporting energy. Although they
have
been detected in the heliosphere outside the Sun, they have never
before
been viewed within the corona, which is the outer layer of the Sun's
atmosphere. Alfv=E9n waves are difficult to detect partly because,
unlike
other waves, they do not lead to large-intensity fluctuations in the
corona. In addition, their velocity shifts are small and not easily
spotted.
Insights into the Sun
By tracking the speed and direction of the waves, researchers will be
able to infer basic properties of the solar atmosphere, such as the
density and direction of magnetic fields. The waves may provide
answers
to questions that have puzzled physicists for generations, such as why
the Sun's corona is hundreds of times hotter than its surface.
The research also can help scientists better predict solar storms that
spew thousands of tons of magnetized matter into space, sometimes
causing geomagnetic storms on Earth that disrupt sensitive
telecommunications and power systems. By learning more about solar
disruptions, scientists may be able to better protect astronauts from
potentially dangerous levels of radiation in space.
"If we want to go to the moon and Mars, people need to know what's
going
to happen on the Sun," Tomczyk says.
A powerful instrument
To observe the waves, Tomczyk and his coauthors turned to an
instrument
developed at NCAR over the last few years. The Coronal Multichannel
Polarimeter, or CoMP, uses a telescope at the National Solar
Observatory
in Sacramento Peak, New Mexico, to gather and analyze light from the
corona, which is much dimmer than the Sun itself. It tracks magnetic
activity around the entire edge of the Sun and collects data with
unusual speed, making a measurement as frequently as every 15 seconds.
The instrument enabled the research team to simultaneously capture
intensity, velocity, and polarization images of the solar corona.
Those
images revealed propagating oscillations that moved in trajectories
aligned with magnetic fields, and traveled as fast as nearly 2,500
miles
per second.
In addition to Tomczyk and McIntosh, the research team included
scientists from the National Solar Observatory, University of Notre
Dame, Framingham High School in Massachusetts, University of Michigan,
and NCAR.
About the article
Title: "Alfv=E9n Waves in the Solar Corona"
Authors: S. Tomczyk, S.W. McIntosh, S.L. Keil, P.G. Judge, T. Schad,
D=2EH. Seeley, J. Edmondson
Publication: Science, August 31, 2007
Contacts for This Release
303-497-8611
303-497-8604
303-497-1579
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