Fe XVII Soft X-Ray Lines: Theory and Data Comparisons

摘要: Fe XVII soft X-ray spectral emission lines are examined using data from the Flat Crystal Spectrometer (FCS) on Solar Maximum Mission satellite. Results compared with theoretical calculations and other recent observational results. Disparate findings different studies inferred opacity of bright resonance line at 15.01 A its center-to-limb behavior reviewed. Present limitations use scattering to infer coronal plasma densities absolute elemental abundances discussed. An analysis is made temperature-insensitive ratio optically thin 16.78 line. This shows that approximately half photons expected in missing cores quiescent active regions solar disk; fraction increases most by 50% near limb. If flux has been resonantly scattered out sight, then equivalent optical depth center τ0~2 disk, based a simple escape probability treatment for slab geometry. suggests effects FCS lines, possible exception O VIII doublet 18.97 A, should be negligible region conditions. consistent lack systematic dependence found previously than A. Yohkoh Soft Telescope measurements sight as function location results sets all support trend increased limb disk center.