Testing, Comparing, and Validating an L1 Method for Abundances Derivations from EUV Spectra

Abstract Element abundances found in the solar corona and solar wind are often different from those measured in the solar photosphere, and the fractionation mechanisms are thought to be intimately tied to the physical processes leading to coronal heating and acceleration of the solar wind. The complexity of the data and the methods used to invert underconstrained problems and thus estimate abundances make it challenging to identify and study these mechanisms. In this work, we present an L1-norm inversion method to derive abundances from coronal spectral observations. We explored a variety of approaches, considering different sets of inverted variables (e.g., including the abundance of Si, S, and Fe, as separate independent variables), and we tested and validated them using synthetic data from numerical radiative MHD models. In addition, we investigated the effects of bound-free absorption from neutral hydrogen and helium on the method and Poisson noise. We discuss the advantages and limitations of the various inversion approaches presented.