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

TL;DR

This paper investigates how the choice of equation-of-state and atomic level data affects the convergence of Rosseland Mean Opacity calculations at the solar radiative boundary, highlighting differences between datasets and models.

Contribution

It compares different EOS models and atomic datasets, revealing their impact on opacity calculations and suggesting improvements for high-energy-density plasma modeling.

Findings

RMOP datasets have many more atomic levels than EOS constrains

RMOP spectra differ significantly from Opacity Project models

EOS constraints reduce the effective number of levels contributing to opacity

Abstract

Convergence of the Rosseland Mean Opacity (RMO) is investigated with respect to the equation-of-state (EOS) and the number of atomic levels of iron ions prevalent at the solar radiative/convection boundary. The "chemical picture" Mihalas-Hummer-D\"{a}ppen 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: $(2 \times 10^6K, \ 10^{23}/cc)$ and $(2.11 \times 10^6K, \ 3.16 \times 10^{22}/cc)$, 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 -- FeXVII, FeXVIII and FeXIX -- 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.