Equation of state in the solar convection zone and the implications of helioseismology

The equation of stale of partially ionized plasmas is complicated owing to the long-range nature of the Coulomb force. Two competing theories of such plasmas, the chemical picture (as employed in the MHD equation of state) and the physical picture (as employed in the Livermore equation of state), predict different values for the adiabatic exponent. Helioseismic inversions for this parameter show a preference for the Livermore equation of state, given the currently preferred heavy-element abundances. The possibility exists of making inferences about heavy-element abundances from helioseismic data, albeit under the assumptions inherent in the choice of equation of state.