In this paper, the intensity ratio of [O I] λ6300 and Hα lines, which plays an important role in the study of warm (or diffuse) ionized interstellar medium, is calculated assuming collisional ionization equilibrium (or coronal equilibrium). The calculated ratio is compared with the previous works, and with the observations, obtained by Reynolds (1989) and Reynolds et al. (1998) with the Wisconsin Ha Mapper facility, toward the directions that sample the faint interstellar emission-line background. The comparison confirms that most of the Ha originates from nearly fully ionized regions along the lines of sight rather than from partially ionized H I clouds or layers of H II on the surfaces of H I clouds.

• 선광일(한국천문연구원) | KWANG-IL SEON (Korea Astronomy Observatory)
• 이대희(한국천문연구원) | DAE-HEE LEE (Korea Astronomy Observatory)