Observations of the O+ (2P-2D) 732 and 733 nm Thermospheric Airglow Emissions with the Wind Imaging Interferometer Leading to Atomic Oxygen Concentrations and ionospheric Winds

Abstract:

Remote sensing of airglow emission provides a powerful approach to the measurement of composition, temperature and winds in the thermosphere, on short and long time scales, including the responses to magnetic storms. Of the available emissions, one that has not been exploited to its full potential is the O+ (2P-2D) pair of doublets at 732.0 and 733.0 nm wavelength. This presentation is of recently analyzed results from WINDII, the Wind Imaging Interferometer on NASA’s Upper Atmosphere Research Satellite, launched in 1991. WINDII is a Doppler Michelson interferometer with the capacity to measure airglow emission rates, Doppler temperatures from line widths and winds from Doppler shifts. One of the filters used to select specific airglow emissions was intended for measurement of the P1(2) line of the (8,3) Meinel band of OH at 731.63 nm but it also transmitted the O+ lines of interest. These have recently been retrieved from the data and are the basis of this presentation. The O+ emission is produced in the daytime, primarily from the photo-ionization of atomic oxygen and so knowing the solar flux the concentration of atomic oxygen can be determined. As a first step the variation of the emission rate on solar flux, solar zenith angle and conjugate photoelectron flux has been investigated, and preliminary results on atomic oxygen concentration are presented. In addition, ion winds can be determined from the Doppler shifts of the emission, which may be compared with the neutral winds obtained with WINDII from the atomic oxygen O(1S) and O(1D) emissions at 557.7 nm and 630.0 nm respectively. This possibility will allow the study of the interactions between the thermosphere and ionosphere for a wide range of conditions.