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 iss ue] is used to infer height-integrated O/N-2 column densities from O I-130. 3-nm FUV dayglow images taken by the Dynamics Explorer 1 (DE 1) spin scan a uroral imager (SAI) [Frank et al., 1981] during a large solar proton event that occurred on July 13, 1982, The FUV results show that O/N-2 decreases i n the northern hemisphere as a result of seasonal and storm time effects. F urthermore, these decreases differ significantly from corresponding predict ions made by the MSISE-90 model of Hedin et al. [1991]. The FUV-derived O/N -2 column densities are compared to in situ volume density and neutral temp erature ([O], [N-2], T-n) measurements made from the Dynamics Explorer 2 (D E 2) satellite [Carignan et al., 1981; Spencer et al., 1981]. The compariso ns are made using two techniques. In the first approach, ground truth estim ates of O/N-2 column densities are made from the in situ measurements. In t he second approach, [O] volume densities are inferred from the FUV measurem ents of O/N-2 column density and directly compared to direct DE 2 neutral a tmosphere composition spectrometer (NACS) measurements of [O]. While some d iscrepancies exist, the results show that reasonable estimates of the atomi c oxygen volume density [O] during the July 13, 1982, solar proton event co uld be made using the FUV images.