Observations of the 3.3—6.1 Â X-ray line and continuous spectrum during four long-duration flares with the RESIK crystal spectrometer on the Coronas-F spacecraft have been analyzed to get the absolute abundances of potassium, argon, and sulphur. A differential emission measure of the form DEM ∝ exp(—Te/T0) was found to give the most consistent results of three models including an isothermal model. We obtained K/H = (3.7 ± 1.0) x 10—7, a factor 3 times photospheric; Ar/H = (2.8 ± 0.2) x 10—6, slightly lower than photospheric; and S/H = (2.2±0.4) x 10—5, approximately equal to photospheric. These measurements are consistent with a pattern in which elements with low (< 10 eV) first ionization potential are enriched in the corona by a factor of about 3 and elements of high first ionization potential have abundances approximately equal to photospheric.
Abundances of Potassium, Argon, and Sulphur in Solar Flares