Solar flux variation of the thermospheric molecular oxygen density

Measurements of the thermospheric molecular oxygen density obtained from the Atmosphere Explorer (AE) satellites and composition data obtained previously from rocket-based experiments provide complimentary information on the distribution of O2 between 120 and 200 km as a function of solar flux. The AE measurements provide a description of the constituent's short-term behavior near solar minimum. With this knowledge, the rocket experiment data, which cover a wider range of solar activity and altitudes, can be analyzed for long-term variations. At mid-latitudes and low latitudes the 200-km O2/N2 density ratio decreases ∼35% as the F10.7 index increases from 70 to 150. The O2 density at 200 km shows little variation but at 120 km decreases ∼30% for the same increase in F10.7. Additionally, the analysis gives evidence for photochemically induced departures from diffusive equilibrium in the molecular oxygen density.