First detection of the O III 495.8911 and 500.6843 nm lines in the Earth's upper atmosphere

Abstract. We report the first detection of two emission lines of the atomic oxygen doubly-charged ion at 495.8911 and 500.6843 nm in the terrestrial upper atmosphere. They correspond to the transitions 1 D 2 - 3 P 1 and 1 D 2 - 3 P 2 of the O ++ ion, respectively. The measurements were performed on 30 October 2003 during the "Halloween" storms, with the Ultraviolet and Visual Echelle Spectrograph (UVES) mounted on the Very Large Telescope (VLT) in Chile. The intensities of these emissions are ~70 mRayleigh, and ~260 mRayleigh, respectively. These emissions constitute a new diagnostic of the state of the ionosphere.