Notes on Wright's interpretation of temporal variation of O/N2ratio in the thermosphere

Abstract

The spectrophotometric determination of an increase in the ratio of concentrations of atomic oxygen to molecular nitrogen, R ≡ n(O)/n(N2), from R1∼1 (early morning, June 5, 1962, 190 km over White Sands, New Mexico, under a solar zenith angle χ = 81°) to the larger value R2∼1.5 (late afternoon, October 25, 1962, same altitude and zenith angle as for R1) has been interpreted as evidence of a predominantly diurnal variation by us [Hall et al., 1963] and as a predominantly seasonal variation by Wright (preceding letter) in this Journal. Therefore, it seems desirable to pursue this apparent discrepancy somewhat further. The Rishbeth-Barron-Wright hypothesis, attributing certain anomalously low F2-region electron densities to correspondingly low O/N2 ratios (for references see Wright's paper), can be discussed profitably on the simplifying basis of assumed photoequilibrium. This assumption appears to be justified mainly because the RBW rule is not intended to refer to variations due to changes in zenith angle or solar EUV radiation fluxes, nor to variations (anomalies) such as may be caused largely by changes in the generally nonvanishing divergences of the ‘ordinary’ diffusion flux of essentially thermal electrons and the hitherto largely ignored redistribution fluxes of essentially nonthermal, fast photoelectrons [Hanson, 1963; Mariani, 1964].