Tidal influences on O-2 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 O-2 atmospheric band airglow. O-2 atmospheric band dayglow measurements ma de 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 dayg low indicates an emission process controlled by solar absorption. Observati ons are compared with modeled emissions based on an atmosphere perturbed wi th diurnal tides predicted by the Tuned Mechanistic Tidal Model (TMTM) for March 1993. Good data/model agreement indicates enhanced emissions result f rom tidal advection of atomic oxygen from the lower thermosphere. While tid es modulate O-2 nightglow by perturbing atomic oxygen recombination rates, the tidal signatures seen in 02 dayplow are due to increased production of ozone and O(D-1). These results provide further confirmation of the consist ency of the HRDI daytime wind, temperature and airglow observations.