The Balmer 9 and Balmer 11 lines of He ii in the Sun |
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| Authors: | J C Raymond R W Noyes M P Stopa |
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| Institution: | (1) Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., U.S.A. |
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| Abstract: | We identify the Balmer 9 and 11 lines of He ii at 959 Å and 942 Å in solar spectra. These lines are produced mainly by recombination following photoionization of He ii by coronal XUV radiation. From analysis of the line intensities, we confirm the theoretical model of Avrett et al. (1976), who found that an appreciable amount of He++ is present at temperatures of 1–2 × 104 K and that the anomalously strong He ii  304 line is produced primarily by collisional excitation. We also confirm the suggestion of Kohl (1977) that the photoionization-recombination process is more important in active regions than in the quiet Sun, and we find that the 304 line is produced largely by recombination in solar flares. |
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