Abstract

Calculations have been made of photoelectron fluxes and energy spectra in the ionosphere for predawn and sunlit atmospheres, taking account of transport, elastic and inelastic collisions, and energy loss to ambient electrons. For predawn models the results indicate that a significant fraction of the incoming electrons are backscattered. By using recent predawn measurements of the high-altitude incident electron flux, the rates of O I (6300 A) emission and secondary ionization rates are computed. An escape flux of the order of 4.1×108 electrons cm−2 sec−1 is calculated for the sunlit atmosphere. The present results are compared with recent rocket measurements and previous calculations. The problem of a recently noted reduction in O I (1304 A) emissions in polar regions is also discussed.