(Lake Tahoe,
NV · AAS Solar Physics Division Meeting · June
20, 2000) -- A three-dimensional
numerical model developed by scientists at the Naval Research
Laboratory (NRL) in Washington, D.C., and "field-tested"
by astronomers at the Smithsonian Astrophysical Observatory (SAO),
may help explain the nature and origin of solar eruptions. These
eruptions are known to trigger stormy space weather, which can,
in turn, damage communications satellites, endanger astronauts
in space, and disrupt transmissions along electrical power lines
on Earth.
A theoretical reconstruction
of the evolving magnetic fields in a flaring region on the Sun,
using NRL's "pressure cooker model" (as it has been
informally nicknamed), matched actual observations made by SAO
scientists using NASA's Transition Region and Coronal Explorer
(TRACE) of the "Bastille Day" Flare on July 14, 1998.
According to the NRL-Smithsonian team, this close agreement between
theoretical predictions and observations demonstrates the viability
of the model for understanding how energetic solar eruptions
occur and for, perhaps, predicting them in advance.
The key strength of the pressure
cooker model is its novel description of the conditions allowing
the release of energy leading to eruptive flares that lead to
coronal mass ejections (CMEs). Magnetic energy emerges from the
solar interior, appears low in the solar atmosphere, and accumulates
under a magnetic "lid." When the lid has a weak spot
-- in this case the null point, where the magnetic field is equal
to zero -- the accumulated low-lying energy can blow violently
through the lid of the "pressure cooker."
The NRL "pressure cooker"
differs from competing CME models in that the magnetic field
is assumed to have a more complicated (quadrupolar) geometry,
with a null point located high in the solar atmosphere. Other
models, which assume a simpler (bipolar) geometry and rely on
different mechanisms for triggering eruptions, "have never
been compared with actual solar observations as precisely as
we did in our study," notes Dr. Guillaume Aulanier. "This
test," he continues, "allowed us to confirm all of
the conditions required for the model to initiate a CME according
to our model."
This is one of the first attempts
by the NRL-SAO research collaboration to reconstruct and interpret
the complex magnetic field of a real observed flaring region.
TRACE's Bastille Day coverage provided some of the finest detailed
observations of an eruptive flare ever obtained. In particular,
the continuous telemetry of the instrument provided more data
on pre-flare activity than has previously been available, which
was essential for validating the model and confirming the pressure
cooker process. The scientists intend to use additional TRACE
data, SOHO/EIT observations and future data from the SOLAR-B
and STEREO missions to further test the pressure cooker model.
The scientific paper describing
this research will be published in the September 2000 issue of
Astrophysical Journal.
Flare
Model Animations presented at the AAS Solar Physics Division
Meeting 6/20/00
The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of nearly 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 85 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.
Comment policy: We hope to receive submissions from all viewpoints, but we ask that all participants agree to the Department of Defense Social Media User Agreement. All comments are reviewed before being posted.