Va. Baturin et al., Seismology of the solar envelope: sound-speed gradient in the convection zone and its diagnosis of the equation of state, M NOT R AST, 316(1), 2000, pp. 71-83
We report the results of an asymptotic inversion of solar oscillation data
for the gradient of the sound speed in the convection zone. This gradient r
eveals derails of;he non-ideal Coulomb interactions between particles, incl
uding pressure ionization, A simplified physical model is used to track dow
n the effect of various physical assumptions in the sound-speed derivative,
The model contains a calibration for the size of the H and He atoms and th
e He+ ion. We find that, for the pressure-ionization regions of hydrogen an
d helium, such a model matches the data better than any of the currently av
ailable parameter-free theories.