Solar flare X-ray spectra

Abstract

A comparison is given of the spectra in the region A = 1.70-1.95 A obtained aboard the 'Inter- cosmos' satellites with those observed in laboratory from a vacuum spark. Wavelengths of the reference He-like Fe ion resonance line (to) and its/'-satellite are reviewed. The difference of 0.0006 ,~, between measured and earlier calculated values is attributed to the Lamb shift of Is-electron. A discussion is presented of the existence of the Kfl lines in the solar spectra. During the period of maximum solar activity (October-Novembe r 1970) more than 20 solar flare spectra in the region 1.70-1.95 A were obtained aboard the ~ cosmos-4' satellite. The wavelengths of the Fe xxIv-xxv ion lines identified in the high resolution spectra were presented in the previous paper (Paper I, Korneev et al., 1979). In the present paper a comparison is made of solar flare spectra with those observed in laboratory from a vacuum spark source. Spectra of this source-i-n-the region of the resonance H- and He-like ion lines of iron were earlier studied in several papers (Fraenkel and Schwob, 1972; Elton and Lie, 1972; Cilliers et al., 1975; Turechek and Kunze, 1975; Kononov, 1978). Apart from its own intrinsic interest, laboratory reproduction of the flare spectra allowed more exact wavelength measurements, necessary to interpret the spectral lines and, by way of comparison between both spectra, to obtain information about the physical conditions of spec- trum excitation. The analysis of the physical conditions in the flare volume based on intensities of registered lines will be presented later in Paper III.