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Session 53 - First Results from the Global Oscillations Network Group (GONG).
Oral session, Wednesday, June 12
The wealth of very precise data from the GONG network and other helioseismic experiments provide a unique opportunity for testing the modeling of stellar interiors. Stellar modeling forms the basis for much of astrophysics. Furthermore, the application and calibration of solar models to the helioseismic data provides a test of the physics on which the models depend; thus we can investigate the thermodynamic and radiative properties of matter under the extreme conditions found in the Sun. Current models are in remarkable agreement with the helioseismic inferences within the errors in the input data; this suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the Sun is unlikely to be caused by errors in the standard solar model.
However, careful analysis of the GONG data reveals subtle discrepancies that we attribute to uncertainties in some of the model input physics and the neglect of other subtle physical processes. The role of mixing inside the Sun, due for example to rotationally induced instabilities during its past evolution, the precise form of the hydrogen depletion profile near the center, the efficiency of helium and heavier element diffusion below the convection zone, and the structure of the highly superadiabatic layer just below the photosphere, are among the significant details in solar models, which the high-quality GONG data will greatly help to resolve. Comparisons between theoretical predictions of solar p-mode frequencies, previous p-mode observations and the first GONG data are used to illustrate these points.
Program listing for Wednesday