The Iron-to-Calcium Abundance Ratio in the 20 X 10 6 K Plasma of Medium and Large Solar Flares

The iron-to-calcium abundance ratio during several flares observed by instruments on the P78-1 and Solar Maximum Mission spacecraft are determined using the intensity ratio of a dielectronic satellite line of Fe XXIV and the resonance line of Ca XIX. Values of A(Fe)/A(Ca) equal to 6.8 +/- 1.0 and 6.0 +/- 1.5 were derived from these data sets, respectively, the small difference being attributable to errors in the calculated instrument sensitivities. These values fall between two other determinations from X-ray spectra, but are less than the photospheric value. They are fairly constant from flare to flare, contrasting with other recent work which indicates strong flare-to-flare variations.