Analysis of potassium abundance in a large number of flares

An initial study of spectra observed in the shortest wavelength channel (3.40–3.80 Å) of the RESIK X-ray spectrometer on CORONAS-F indicates the presence of substantial flare-to-flare variations in the line-to-continuum ratio of several lines, in particular He-like potassium (K xviii) lines, occurring in the range 3.53–3.57 Å. The observed variations are larger than those expected from temperature variations. This has motivated a study of possible variations in the potassium abundance in the observed spectra. With a new RESIK calibration available, we have obtained absolute fluxes of the K xviii resonance line as well as the continuum and lines observed in other RESIK channels (3.40–6.05 Å) for some 1163 intervals observed early in 2003. Analysis of these observations allowed us to determine the average absolute potassium abundance for the period studied and investigate the variability of abundance. The results obtained are presented and discussed.