Gravity waves and vertical diffusion in the lower thermosphere from 557.7nm airglow

The 557.7 nm oxygen airglow is emitted in the 90-100 km region. This is the region where a large part of the gravity-wave (GW) spectrum saturates and where nonlinear effects and wave breaking become important to limit the amplitude growth of the waves through the generation of turbulence, which enhances the mixing in the region. Mixing leads to diffusion, especially of O, which diffuses downward from its rich source above 95 km. Studying the 557.7 nm airglow enables one to characterize both the gravity waves and the enhanced vertical diffusion. Model predictions of fluctuations due to gravity waves in the atomic-oxygen green line emission are calculated and used in conjunction with ground-based data from a CCD all-sky camera to predict the density fluctuations and estimate the GW enhanced vertical diffusivity D-ZZ as derived by Weinstock [1976]. Three wave events were used for this study, and an average D-ZZ of 3.6 x 10(4) m(2)/sec was calculated. (C) 1997 COSPAR.