Interface of Equation-of-State, Atomic Data and Opacities in the Solar Problem

The dependence of the Rosseland Mean Opacity (RMO) on the equation-of-state and the number of included atomic levels of iron ions prevalent at the solar radiative/convection boundary is investigated. The ”chemical picture” Mihalas-Hummer-Däppen MHD-EOS, and its variant QMHD-EOS, are studied at two representative temperature-density sets at the base of the convection zone (BCZ) and the Sandia Z experiment: (2 × 106K, 1023/cc) and (2.11 × 106K, 3.16 × 1022/cc), respectively. It is found that whereas the new atomic datasets from accurate R-matrix calculations for opacities (RMOP) are vastly overcomplete, involving hundreds to over a thousand levels of each of the three Fe ions considered — Fe xvii , Fe xviii , Fe xix — the EOS constrains contributions to RMOs by relatively fewer levels. The RMOP iron opacity spectrum is quite different from the Opacity Project distorted wave model and shows considerably more plasma broadening effects. This work points to possible improvements needed in the EOS for opacities in high-energy-density (HED) plasma sources.