Si IX Emission Lines in Spectra Obtained with the Solar euv Research Telescope and Spectrograph (Serts) |
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| Authors: | Keenan F.P. Katsiyannis A.C. Aggarwal K.M. Mathioudakis M. Brosius J.W. Davila J.M. Thomas R.J. |
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| Affiliation: | (1) Department of Pure and Applied Physics, The Queen's University of Belfast, Belfast, BT7 1NN, Northern Ireland;(2) Laboratory for Astronomy and Solar Physics, Code 682, NASA's Goddard Space Flight Center, Greenbelt, MD, 20771, U.S.A;(3) Department of Physics, The Catholic University of America, Washington, DC, 20064, U.S.A |
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| Abstract: | Theoretical electron-density-sensitive emission line ratios involving 2s22p2–2s2p3 transitions in Si?ix between 223 and 350 Å are presented. A comparison of these with an extensive dataset of solar-active-region, quiet-Sun, subflare and off-limb observations, obtained during rocket flights by the Solar EUV Research Telescope and Spectrograph (SERTS), reveals generally very good agreement between theory and experiment. This provides support for the accuracy of the line-ratio diagnostics, and hence the atomic data on which they are based. In particular, the density-sensitive intensity ratio I(258.10 Å)/I(349.87 Å) offers an especially promising diagnostic for studies of coronal plasmas, as it involves two reasonably strong emission lines and varies by more than an order of magnitude over the useful density range of 109–1011 cm?3. The 2s22p2 1S0–2s2p3 1P1 transition at 259.77 Å is very marginally identified for the first time in the SERTS database, although it has previously been detected in solar flare observations. |
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