Tidal influences on O2 atmospheric band dayglow: HRDI observations vs. model simulations

Atmospheric tides perturb the temperature, winds, density, and composition of the mesosphere and lower thermosphere (MLT) and therefore affect daytime O2 atmospheric band airglow. O2 atmospheric band dayglow measurements made by the High Resolution Doppler Imager (HRDI) show clear tidal signatures in equatorial emission rates during equinox, when diurnal tide amplitudes are large. During solstice the observed symmetric diurnal variation of dayglow indicates an emission process controlled by solar absorption. Observations are compared with modeled emissions based on an atmosphere perturbed with diurnal tides predicted by the Tuned Mechanistic Tidal Model (TMTM) for March 1993. Good data/model agreement indicates enhanced emissions result from tidal advection of atomic oxygen from the lower thermosphere. While tides modulate O2 nightglow by perturbing atomic oxygen recombination rates, the tidal signatures seen in O2 dayglow are due to increased production of ozone and O(¹D). These results provide further confirmation of the consistency of the HRDI daytime wind, temperature and airglow observations.