Diurnal and seasonal variations of the atmosphere near the 100-kilometer level

Abstract

Variations in the relative concentration of molecular nitrogen (N2) and atomic oxygen (O) in the upper atmosphere are of considerable interest, since it seems probable that the electron concentration of the F region depends directly on the [O]/[N2] ratio. Thus Rishbeth and Barron [1960] and Wright [1963a, b; 1964] have elsewhere suggested that seasonal variations in (dNe/dt)n at sunrise, the F-region seasonal anomaly, and certain features of the F-region diurnal variation can be explained by decreases in the [O]/[N2] ratio in the summer and in the afternoon. In a recent communication to this Journal, Hall et al. [1963] reported an interesting pair of rocket experiments in which the neutral particle concentrations were inferred from measurements of solar extreme ultraviolet absorption. Their flights represented morning (0545 MST) and afternoon (1630 MST) conditions in June and October, respectively. It had been intended to examine only the diurnal variation in June, but circumstances forced the afternoon experiment into the later month. Their results pertinent to the present discussion are summarized in Table 1.