Origin of a tidal structure in the thermospheric O/N2 ratio



One recently recognized way of studying the ionospheric and thermospheric structure is through measurements of the column number density ratio of atomic oxygen to molecular nitrogen (O/N2). Data from the Global Ultraviolet Imager on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite show that this ratio exhibits a tidal structure. Kil and Paxton found that the 135.6-nanometer emission produced by the radiative recombination of the oxygen ion contributes to the retrieved O/N2 ratio, and therefore the tidal structure in the O/N2 ratio originates in the ionosphere, not the thermosphere. (Geophysical Research Letters, doi:10.1029/2011GL049432, 2011)