The inner
workings of sunspots —those dark blotches that mark intense magnetic activity
on the sun's surface — have long been a mystery, but a new computer simulation
is providing a more realistic look inside them.
Understanding
the complex dynamics that drive sunspots could help scientists better
understand and predict the potential impacts on
communications systems and climate patterns of the geomagnetic storms produced
by these solar blights.
"This
is the first time we have a model of an entire sunspot," said one of the
scientists who helped create the simulation, Matthias Rempel of the National
Center for Atmospheric Research (NCAR) in Boulder, Colo. "If you want to
understand all the drivers of Earth's atmospheric system, you have to
understand how sunspots emerge and evolve."
Sunspots
are areas where intense magnetic activity acts like a cap on the roiling
material below. These splotches appear darker than the surrounding surface
because they are cooler — around 7,000 degrees Fahrenheit (4,000 Celsius)
versus 10,000 F (5,500 C).
Solar flares
and coronal mass ejections are typically found in magnetically active regions
around groupings of sunspots. These plasma
storms can buffet the Earth's atmosphere and disrupt power grids,
satellites and other systems.
Sunspot
activity peaks and wanes on a roughly 11-year cycle. That cycle is currently
in its low period, so there now are few sunspots and little solar activity.
The new
model simulates an area on the sun of about 31,000 by 62,000 miles (50,000 by
100,000 km) and 3,700 miles (6,000 km) in depth; within this area, the
simulation captures pairs of sunspots with opposite magnetic polarity. The
model reveals the details of the dark central region, or umbra, as well
as the narrow filaments of mass that stream away from the spots in the outer,
or penumbral, regions of the sunspot.
The
simulations suggest that the magnetic fields within the sunspots need to be
inclined in certain directions to create these complex structures. Rempel and
his colleagues think that sunspot features can be explained as a consequence of
convection in a magnetic field.
"With
this breakthrough simulation, an overall comprehensive physical picture is
emerging for everything that observers have associated with the appearance,
formation, dynamics and the decay of sunspots on the sun's surface," said
Michael Knoelker, also of NCAR.
The model
was run on NCAR's new bluefire supercomputer and verified with the
detailed observations made by ground- and space-based telescopes.
The
research, detailed in the June 19 online issue of the journal Science,
was funded by the National Science Foundation.
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