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Title:
Solar Si II line ratios from the high-resolution telescope and spectrograph
Authors:
Keenan, F. P.; Cook, J. W.; Dufton, P. L.; Kingston, A. E.
Affiliation:
AA(Belfast, Queen's University, Northern Ireland), AB(U.S. Navy, E.O. Hulburt Center for Space Research, Washington, DC), AC(Belfast, Queen's University, Northern Ireland), AD(Belfast, Queen's University, Northern Ireland)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 387, March 10, 1992, p. 726-731. Research supported by SERC and U.S. Navy. (ApJ Homepage)
Publication Date:
03/1992
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
Atomic Excitations, Silicon, Solar Radiation, Solar Spectra, Sunspots, Ultraviolet Radiation, Emission Spectra, Fine Structure, High Resolution, Line Spectra, Rocket-Borne Instruments, Spectrographs, Telescopes
DOI:
10.1086/171121
Bibliographic Code:
1992ApJ...387..726K

Abstract

Theoretical emission-line ratios involving multiplets near 1262, 1306, and 1530 A are derived on the basis of new calculations of electron-impact excitation rates for allowed transition in Si II. A comparison of these line ratios with observational data from a quiet solar region, a sunspot, and an active region, obtained with the HIRTS on board a sounding rocket flight reveals that the 1530-A multiplet is optically thick, which is consistent with a calculation of the optical depth of these lines through a model atmosphere. The 1262- and 1306-A multiplets appear to be effectively optically thin. The average discrepancy between the theoretical and observed ratios is about 40 percent, which may not be significant, since the estimated uncertainties in both the calculated and experimental data are approximately 30 percent.

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