OBSERVATIONS OF TRANSITIONS OF HYDROGEN-LIKE FE-XXVI IN SOLAR-FLARE SPECTRA

Observations of solar flare spectra over the wavelength range 1.769-1.796 Å with the Bent Crystal Spectrometer on the NASA Solar Maximum Mission satellite are presented. The 2P3/2, 2P1/2 and associated satellite transitions of Fe XXVI are identified, their intensities and widths estimated and the results compared with theoretical predictions. For two spectra, which include the isolated n = 2 satellite features, the observations can be reproduced by plasma temperatures of 24.0 * 106 and 28.4 * 106 K. Linewidth measurements show evidence for non-thermal velocities of up to 150 Km-1. We compare emission measures derived from the Fe XXVI observations with those from lower temperature Ca XIX and Fe XXV measurements and find emission measure decreasing with temperature. © 1981 Oxford University Press. All rights reserved.