Thermal and wind‐induced variations in thermospheric molecular oxygen as measured on AE‐D

Simultaneous measurements of ambient [O2], [N2], and temperature were made near winter solstice, 1975, by the open source neutral mass spectrometer (OSS) on Atmosphere Explorer-D. The data, taken at midmorning and all latitudes, are analyzed by using scatter plots and correlation coefficients. At 200 km the [O2] density exhibits a positive correlation with the magnetic indices. Owing to the latitude dependence, this description of the response of [O2] during or following periods of magnetic activity, while it is useful, is only qualitative. The increase in [O2] with increasing ambient temperature is much better defined over a wide range of latitudes. In addition to temperature, global scale wind systems may play a role in controlling the distribution of [O2]. To study this role further, measurements of [N2] are used to help distinguish between temperature and wind effects in [O2]. A survey of the latitudinal variations in [O2]/[N2] with temperature indicates a positive response in high-latitude regions and a negative response near the equator. This is further substantiated with the calculation of correlation coefficients. Such an effect can be explained by inferring the existence of upward vertical winds at high latitudes, meridional flow toward lower latitudes, and subsidence near the equator. Such wind systems are in agreement with those predicted by models and measured in the high-latitude regions. It is concluded that [O2], being a minor constituent, is controlled both by temperature variations and by wind induced diffusion.