Atomic oxygen in the thermosphere during the July 13, 1982, solar proton event deduced from far ultraviolet images

The far ultraviolet (FUV) analysis technique of Strickland et al. [this issue] is used to infer height‐integrated O/N2 column densities from O I‐130.4‐nm FUV dayglow images taken by the Dynamics Explorer 1 (DE 1) spin scan auroral imager (SAI) [Frank et al., 1981] during a large solar proton event that occurred on July 13, 1982. The FUV results show that O/N2 decreases in the northern hemisphere as a result of seasonal and storm time effects. Furthermore, these decreases differ significantly from corresponding predictions made by the MSISE‐90 model of Hedin et al. [1991]. The FUV‐derived O/N2 column densities are compared to in situ volume density and neutral temperature ([O], [N2], Tn) measurements made from the Dynamics Explorer 2 (DE 2) satellite [Carignan et al., 1981; Spencer et al., 1981]. The comparisons are made using two techniques, In the first approach, ground truth estimates of O/N2 column densities are made from the in situ measurements. In the second approach, [O] volume densities are inferred from the FUV measurements of O/N2 column density and directly compared to direct DE 2 neutral atmosphere composition spectrometer (NACS) measurements of [O]. While some discrepancies exist, the results show that reasonable estimates of the atomic oxygen volume density [O] during the July 13, 1982, solar proton event could be made using the FUV images.