ESPOS - Thoughts on measuring elemental abundances in the solar atmosphere (G. Del Zanna)

I briefly review some methods and measurements of elemental abundances in the solar atmosphere, with emphasis on the transition region and corona. Some limitations in the methods, in the modeling of the spectral line intensities, and the observations are discussed. Examples from the X-rays, the EUV, the UV, the visible, and near-infrared are presented. A significant improvement in the modeling of some of the ions is being made available with CHIANTI version 11. All the observations indicate that the solar corona has photospheric abundances and that the hot 3 MK active region cores have stable enhancements of a factor of about 3.2 in the ratios of low to high-FIP elements. A lot of uncertainties and puzzles still exist, requiring further analyses and, more importantly, future instrumentation.