Dayglow of the oxygen A band

Abstract

Rocket observations of O2 dayglow have been obtained by means of spectrometers and photometers. Results for the A band (0–0 band of the atmospheric system) cover the range 35–128 km, and for the 0–1 band 59–95 km. Spurious effects attributed to dust particles and clouds from the rocket have also been observed. A detailed analysis of the observations is given, taking account of the fact that they were made in an optically thick atmosphere. Three major production processes have been identified: energy transfer from O(¹D), dominant above 100 km; resonance scattering, dominant from 65 to 100 km; and photolysis of ozone, dominant from 35 to 65 km, and probably important up to 100 km. In the region 85–100 km, an alternative to the ozone source, a chemiluminescent reaction as in the nightglow, suffers difficulties that make it less probable. It is thus likely that a good estimate is now available for daytime ozone concentrations up to 100 km. Collisional quenching at a rate proportional to atmospheric density is found, and the rate coefficient for air molecules is 1.4 × 10−15 cm³ sec−1. This quenching is fast enough to suppress the effects of multiple scattering, including the Bates fluorescence that could convert 0–0 photons into 0–1. The observed photon intensity ratio of 17±2 is therefore not perturbed by this fluorescence. A discussion is given of the effects of varying solar zenith angle, and calculated results are shown, A perturbation in the 110–130 km region is attributed to a ‘wave’ in the distribution of O2, caused by a similar variation in the flux due to eddy mixing. The calculation of transmission functions for a self-absorbed band and the production and transmission of the nightglow emission are discussed in the appendixes.