Dynamical influence on the equatorial airglow observed from the South American sector

Abstract The upper atmospheric airglow emissions, OI 557.7 nm, NaD 589.3 nm, OH (9,4) and O 2 atmospheric (0,1) bands and their rotational temperatures have been measured using ground-based multichannel airglow photometers, one located near the equator at Fortaleza (3.9 S, 38.4 W) and the other at lowmiddle latitude Cachoeira Paulista (22.7 S, 45.0 W). Monthly averaged nocturnal variations calculated from the data from 1987 to 1993 were used to study the influence of atmospheric dynamical processes on these emissions. Harmonic analysis revealed that the Cachoeira Paulista data are mainly represented by a 12 hour period oscillation. Phase differences between the different emissions reveal that the vertical phase velocity is about 4 km/h and the vertical wavelength about 50 km. Fortaleza data on the other hand showed longer period, 24 hours, slow vertical propagation velocity, 1.1 km/h, and short vertical wavelength, about 30 km. These facts lead us to conclude that the Cachoeira Paulista data are mainly controlled by the semidiurnal tidal oscillation and the Fortaleza data are controlled by the diurnal tide.