Weakening of the solar extreme-ultraviolet line emission by lyman continuum absorption as derived from line ratios |
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| Authors: | Mitsuo Kanno Yoshinori Suematsu Takara Nishikawa |
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| Affiliation: | (1) Hida Observatory, University of Kyoto, Kamitakara, 506-13 Gifu, Japan;(2) Department of Astronomy, University of Kyoto, 606 Kyoto, Japan |
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| Abstract: | The intensity ratios of Niii, Oiii, Oiv, and Ov lines observed by the HCO experiment on Skylab are compared with the results of recent multilevel calculations. It is found that solar transition-region spectra require Lyman continuum absorption. The equivalent optical thickness of the absorbers causing the weakening is found to be 1.6–1.7 for a quiet area, 1.4–1.9 for a coronal hole, and 2.4–2.5 for active regions. These values are consistent with previous estimates from different methods. |
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