Further Qu~~icat~o~ of the Sources and Sinks of ~e~ospheric O(%) Atoms

*Also affiliated with the National Institute for Telecommunications Research, CSIR, P.O. Box 3718, Johannesburg, South Africa. and excitation cross sections in the ‘L-stream photoelectron code developed by Nagy and Banks (1970). The production rate of O(*D) photoelectron fluxes are -20% lower than that obtained in our original paper (Torr et al., 1980). The new cross sections for dissociation of N2 come from Zipf et al. (1980) and Zipf and McLaughlin (1978). These cross sections are larger because the In; manifold is more efficiently excited by photoelectrons and low energy aurora1 electrons than previously suspected. The other cross sections come from Porter et al. (1976) and Jackman et al. (1977). These include cross sections for exciting Rydberg states of 0 that were not previously included. In this paper we have chosen not to attempt to specifically reproduce the Atmosphere Explorer (AEC) data for orbit 435 which was analysed by Hays et al. (1978), because most of the data were taken at equatorial latitudes, whereas our theoretical mode1 applies to midlatitudes. Instead, we have examined midlatitude data from four 1974 winter orbits (491, 533, 596 and 597) and three 1974 summer orbits (1808, 1823, 1853) (see Hays et al. (1973) for a description of the visible airglow experiment-VAE). Within each group the volume emission rates are remarkably similar, but there is a large increase in the summer emission rates over the winter rates above 250 km which has not been th~reti~ly investigated previously.