Physics
Scientific paper
Feb 1984
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984soph...90..291h&link_type=abstract
Solar Physics (ISSN 0038-0938), vol. 90, Feb. 1984, p. 291-302. Research supported by the Ministry of Education.
Physics
7
Atomic Energy Levels, Chromosphere, Helium, Spectral Line Width, Ultraviolet Spectra, Photoionization, Solar Corona, Solar Eclipses
Scientific paper
Line profiles of He II 4686 A and He I 4713 A from active regions in the chromosphere were observed during the total solar eclipse of February 16, 1980, with a grazing incidence objective grating spectrograph. The Doppler width of the He I triplet line of 4713 A increases with height and the average width is compatible with width of metallic and hydrogen lines, suggesting that the kinetic temperature of He I triplet emitting region is less than or equal to 8000 K. This can only be explained by recombination after photoionization due to coronal UV radiation. The Doppler width of the Paschen alpha line of He II 4686 is, without any correction for the separation of subcomponents of the line nor nonthermal velocity, 18.4 km/s. This line width also shows a tendency to increase with height. After comparison with Doppler widths of He I 4713 and the EUV lines, and a necessary subtraction of nonthermal velocity, it is shown that this line is emitted in a 20,000 K temperature region, which again supports the view that this line is emitted through the recombination process after photoionization due to coronal XUV radiation below 228 A.
Hirayama Tadashi
Irie Makoto
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