Sun's Deep Interior Revealed by New Computer Model (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Thu, 7 Jun 2007 21:16:25 GMT
National Center for Atmospheric Research
Boulder, Colorado
Contacts
For Journalists:
David Hosansky, head of Media Relations
303-497-8611
Mark Miesch, NCAR Scientist
303-497-1582
May 28, 2007
Sun's Deep Interior Revealed by New Computer Model; Research Provides
Clues to the Inner Dynamics of Stars
BOULDER -- A new computer model simulates convection patterns in the deep
interior of the Sun in unprecedented detail. The patterns, known as giant
cells, play a critical role in solar variability, influencing magnetic
storms that take aim at Earth.
The model was developed by a team of scientists led by Mark Miesch of the
National Center for Atmospheric Research (NCAR).
"This model provides us with an unprecedented view of how the solar
interior works," says Miesch, a scientist in NCAR's High Altitude
Observatory. "It opens a window on a number of important solar processes,
including the delicate balance of forces that causes the Sun's equator to
rotate faster than its poles."
The team, which has submitted its findings to the Astrophysical Journal,
will present the research at the American Astronomical Society meeting in
Honolulu on Monday, May 28.
"This is our first indication of what the chaotic interior of a star looks
like," Miesch explains. "Stars are the building blocks of the universe,
and understanding what goes on within them is critical to understanding
diverse aspects of astrophysics."
Giant cells and churning masses of plasma
Convection near the surface of the Sun occurs when hot plasma rises and
cooler, denser plasma sinks, which is a process similar to what occurs in
water that is heated on a stove. Convection also takes place far beneath
the Sun's surface, where scientists suspect there are churning masses of
plasma up to 10 times larger than the size of Earth. These masses, known
as giant cells, may hold the key to the movement of sunspots and the
behavior of solar storms, which can buffet Earth's atmosphere and affect
satellites as well as power and communications systems.
To map the giant cells, Miesch and his team drew on data from
helioseismology and used supercomputers to solve the equations of stellar
fluid dynamics. Helioseismology is a technique to measure sound waves that
propagate deep within the interior of the Sun. By analyzing variations in
the light and velocity of the waves as they emerge on the Sun's surface,
scientists can glean information about hidden subsurface structures.
The model simulations capture processes in the outer 30 percent of the
solar interior. They correspond to existing maps that are based on
helioseismic data about subsurface processes. The simulations also capture
the Sun's unusual rotational pattern, which occurs when the giant cells
redistribute angular momentum. This causes the solar equator to rotate
every 28 days while higher latitudes take about 35 days.
Glimpses into the inner workings of the Sun
The model reveals details about the giant cells that could help scientists
learn more about the inner workings of the Sun, which are hidden from any
current observational technique. The team's simulations indicate that, at
low solar latitudes, cooler and denser plasma sinks along north-south
corridors, with the corridors moving eastward relative to hotter plasma
that rises. But at higher latitudes, rising and falling areas of plasma
meet and create solar cyclones that last for several days.
The model also can help scientists understand how giant cells induce a
global circulation. The circulation, acting like a conveyor belt, moves
plasma from the solar equator toward the poles just beneath the surface of
the Sun and then back toward the equator at a greater depth. This
circulation, working with convection and rotation, generates and organizes
magnetic fields, giving rise to patterns of magnetic activity such as the
11-year sunspot cycle.
To create the model, Miesch worked with Allan Sacha Brun of the French
Atomic Energy Commission in Saclay; Marc DeRosa of Lockheed Martin Solar
and Astrophysics Laboratory in Palo Alto, California; and Juri Toomre of
the University of Colorado and JILA in Boulder.
The modeling work was supported by NASA's Heliophysics Theory Program, and
it made use of resources supplied by the Pittsburgh Supercomputing Center,
the San Diego Supercomputing Center, the National Center for
Supercomputing Applications, and NASA's Project Columbia. The National
Science Foundation provides base funding for NCAR's High Altitude
Observatory.
[NOTE: Images supporting this release are available at
http://www.ucar.edu/news/releases/2007/solarmodelvisuals.shtml ]
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