Chemical Abundances from the Continuum

TL;DR

This paper revisits the calculation of solar fluxes in the near-UV, highlighting the importance of updated metal opacities and composition adjustments, and finds that 3D effects have minimal impact on continuum flux predictions.

Contribution

It provides a self-consistent approach to modeling solar fluxes with updated metal opacities and composition, and compares 1D and 3D models to assess their differences.

Findings

Adjusted solar composition improves flux reproduction

3D effects cause less than 10% flux correction in near-UV

Discrepancy remains in the 270-290 nm flux window

Abstract

The calculation of solar absolute fluxes in the near-UV is revisited, discussing in some detail recent updates in theoretical calculations of bound-free opacity from metals. Modest changes in the abundances of elements such as Mg and the iron-peak elements have a significant impact on the atmospheric structure, and therefore self-consistent calculations are necessary. With small adjustments to the solar photospheric composition, we are able to reproduce fairly well the observed solar fluxes between 200 and 270 nm, and between 300 and 420 nm, but find too much absorption in the 270-290 nm window. A comparison between our reference 1D model and a 3D time-dependent hydrodynamical simulation indicates that the continuum flux is only weakly sensitive to 3D effects, with corrections reaching <10% in the near-UV, and <2% in the optical.