YOHKOH OBSERVATIONS AS A MEANS OF CHECKING S, Ca, AND Fe CORONAL ABUNDANCES AND He-LIKE IONIZATION FRACTIONS

摘要

Electron temperatures are derived from X-ray spectra observed by the Bragg crystal spectrometer on board the Yohkoh satellite during long-duration solar flares, and it is found that in the late stages of such events the emitting plasma is nearly isothermal. This fact enables us to examine the accuracy of the fractional abundances of He-like S, Ca, and Fe ions, as well as the ratios of coronal element abundances. Using currently accepted values for ionization fractions and our own values of element abundances, we find that adjustments of 50% or less are needed.