Latitudinal distributions of minor neutral hydrogen-oxygen constituents in the winter mesosphere and lower thermosphere

Abstract

The latitudinal distributions of the concentrations of hydrogen-oxygen constituents are computed in the winter mesosphere and lower thermosphere. Vertical eddy diffusion coefficients varying with latitude and altitude are used, but the effects of horizontal transport are not included. The results show that the distributions of minor constituents have significant latitudinal variations due to the effects of photodissociation and vertical diffusion. It is also indicated that the meridional profile of the O ( 3 P) concentration has a maximum in the latitudes 50°–60° near the mesopause in winter, and that the vertical profile of the O 3 concentration has a second peak near the mesopause, mainly caused by the indirect influences of vertical eddy diffusion. The calculated profiles of the O( 3 P) and O 3 concentrations, the atomic-to-molecular oxygen concentration ratios, and airglow emission rates are compared with the recent available observations, showing fairly good agreement. Comparison of the theoretical O( 3 P) concentrations and 5577 Å airglow emissions suggests an important role of horizontal transport in the lower thermosphere.