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X-ray lines of helium-like calcium (\ion{Ca}{19}) between 3.17~\AA\ and3.21~\AA\ and associated \ion{Ca}{18} dielectronic satellites have previouslybeen observed in solar flare spectra, and their excitation mechanisms are wellestablished. Dielectronic satellites of lower ionization stages(\ion{Ca}{17}~--~\ion{Ca}{15}) are not as well characterized. Several spectraduring a large solar flare in 2001 by the DIOGENESS X-ray spectrometer on the{\em CORONAS-F}\/ spacecraft show the \ion{Ca}{17} and \ion{Ca}{16} satellitesas well as lines of ionized argon (\ion{Ar}{17}, \ion{Ar}{16}) includingdielectronic satellites. The DIOGENESS spectra are compared with spectra from asynthesis code developed here based on an isothermal assumption with variousatomic sources including dielectronic satellite data from the CowanHartree--Fock code. Best-fit comparisons are made by varying the temperature asthe code's input (Ar/Ca abundance ratio fixed at 0.33); close agreement isachieved although with adjustments to some ion fractions. The derivedtemperature is close to that derived from the two {\em GOES}\/ X-ray channels,$T_{\rm GOES}$. Some lines are identified for the first time. Similar spectrafrom the {\em P78-1}\/ spacecraft and the Alcator C-Mod tokamak have also beenanalyzed and similar agreement obtained. The importance of blends of calciumand argon lines is emphasized, affecting line ratios used for temperaturediagnostics. This analysis will be applied to the {\em Solar Maximum Mission}\/Bent Crystal Spectrometer archive and to X-ray spectra expected from the ChemiXinstrument on the Sun-orbiting {\em Interhelioprobe}\/ spacecraft, while therelevance to X-ray spectra from non-solar sources is indicated.

Highly ionized Calcium and Argon X-ray spectra from a large solar flare