PHOTOSPHERIC ABUNDANCES OF OXYGEN, NEON, AND ARGON DERIVED FROM THE XUV SPECTRUM OF AN IMPULSIVE FLARE

Relative elemental abundances of O, Ne, Na, Mg, Ar, and Ca are determined from detailed analysis of XUV spectra emitted by an impulsive flare. The electron density measured from three diagnostic line ratios is 2-3 × 1012 cm-3. We have found that the relative abundances in the flare are similar to values obtained from or proposed for photospheric material. The ratios of O/Mg, Ne/Mg, and Ar/Mg are about 4 times higher in the impulsive flare than the values typically observed in the average corona. We suggest that electric fields above the photosphere may be responsible for the order of magnitude variations between the abundances of the group of elements with high first ionization potentials (FIP) and the group with low FIP.