Vertical propagation of gravity waves determined from zenith observations of airglow Original Research Article

From our growing data base of OH and O2 airglow intensity and temperature measurements at lower mid-latitudes, gravity wave information has been extracted by time series spectral analysis. According to existing theories, the amplitude and phase relationships between intensities and rotational temperatures for a given airglow emission contain information about vertical wave propagation. A wide but clearly non-random distribution of phase shifts between intensity and temperature is observed. Cases of 180°, often cited in the literature, are definitely exceptions, here. For observed periods between about ten minutes and three hours, 30% of the waves at 95 km, and 40% at 87 km propagate downward. This signals the importance of wave reflection in the mesopause region.