Solar abundances from X-ray flare observations

Abstract

The absolute coronal abundances of Si, Ar and Ca are derived from line and continuum X-ray flare observations. The lines used in the analysis are from either H- or He-like ions and allowance has been made for the presence of satellite lines and other unresolved line blends. The measured abundances for Si |$(7.7^{+0.2}_{-0.3})$| (log H = 12) and Ca |$(6.5^{+0.1}_{-0.2})$| are in good agreement with other solar values. However, those for S |$(6.9^{+0.1}_{-0.3})$| and Ar |$(6.4^{+0.2}_{-0.3})$| are lower than other solar values derived from observations of lower ionization stages. It is established that these are real differences and it is suggested that these may be caused by ambipolar and magnetic diffusion effects. In addition the calculations of line and continuum intensities are presented in the form of equivalent width versus temperature plots for use in analysing cosmic X-ray spectra.