Extreme-ultraviolet emission lines of S X in solar flare and active region spectra

Francis Keenan, A.C. Katsiyannis, K.G. Widing

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


R-matrix calculations of electron impact excitation rates in N- like S x are used to derive theoretical emission-line intensity ratios involving 2s(2)2p(3)-2s2p(4) transitions in the 189-265 Angstrom wavelength range. A comparison of these with observational data for solar flares and active regions, obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab and the Solar EUV Rocket Telescope and Spectrograph, reveals that many of the S x lines in the spectra are badly blended with emission features from other species. However, the intensity ratios I(228.70 Angstrom)/I(264.24 Angstrom) and I(228.70 Angstrom)/I(259.49 Angstrom) are found to provide useful electron density diagnostics for flares, although the latter cannot be employed for active regions, because of blending of the 259.49 Angstrom line with an unidentified transition in these solar features.
Original languageEnglish
Pages (from-to)565-569
Number of pages5
JournalAstrophysical Journal
Issue number1 I
Publication statusPublished - 20 Jan 2004

ASJC Scopus subject areas

  • Space and Planetary Science

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