Tidal mechanisms of dynamical influence on oxygen recombination airglow in the mesosphere and lower thermosphere

The specific mechanism causing local time variations in the atomic oxygen recombination airglow emissions is investigated by examining the Lagrangian histories of air parcels in the wind fields of the diurnal tide generated by the Global Scale Wind Model of Hagan et al. (1995). The emission rate variations are found to be due to the vertical displacements of air parcels associated with the diurnal tide. The density and temperature induced airglow perturbations associated with the tide are out of phase with that associated with the vertical displacement and hence act to supress the intensity variations. The modelled emission rate variations with local time correspond closely to those deduced from recent observations in the mesosphere and lower thermosphere by the Wind Imaging Interferometer and the High Resolution Doppler Imager on the Upper Atmosphere Research Satellite. The observed latitudinal variations in the local time behaviour of these airglow emissions are due to latitudinal variations in the vertical velocity associated with the tide.