Equation of State Studies Using SOHO Data
Principal Investigator / Institution: Werner Dappen, USC
This is a new task to use the SOHO data to obtain constraints on the equation
of state while pre-helioseismic solar models were quite adequately using
simple ideal-gas equations of state, it turned out that non-ideal corrections
had to be included in order to match the constraints from solar oscillation
frequencies. in particular, the effect of the Coulomb pressure correction in
the solar plasma became clearly evident. Finer non-ideal effects are
emerging in analyses of current observational data. The finer effects in
the equation of state are subject of current controversial physical models
of plasmas. A helioseismic analysis effectively allows experiments to be
carried out on the physics of the plasma at this level of detail. This is a
severe test of theory. Although the non-ideal effects are relatively small
corrections (typically 1-10% of the pressure), the extraordinary
observational accuracy makes the helioseismic data sensitive to them,
imposing stringent constraints on their theoretical computation to the
required level. In this way, the subtle quantum many-body effects that
contribute to the small, but theoretically challenging non-ideal corrections
in the equation of state, can be studied in the Sun. Knowledge about these
non-ideal corrections will have astrophysical implications for higher
densities plasmas of low-mass stars, brown dwarfs, and giant planets.
So far, the P.I. has been carrying out solar modeling and inversion tasks
in collaboration with Joergen Christensen-Dalsgaard (Aarhus). To enable
the higher cadence required by the flurry of the SOI/MDI data, this proposal
requests support to develop solar modeling and inversion capabilities at USC,
in order to analyze the data for equation of state effects. In this way, SOHO
data will make a contribution to solar physics, stellar astrophysics, and
basic physics.