"Pressure Cooker" Model May Help Explain and Predict Giant Solar Flares

6/30/2000 - 36-00r
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(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
 TRACE intro clip

 Data from TRACE showing the flare

 Animation of the model

Additional Animation of the Model

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