Measurements and interpretation of low-energy photoelectrons

Measurements of the photoelectron spectrum at White Sands Missile Range in June 1965 are reported and compared with theory. The agreement is satisfactory and shows that a realistic treatment of photoelectrons, at least at low altitudes, is feasible with current information on atmospheric structure, solar fluxes, and cross sections. The theoretical model is also compared with measurements by Hinteregger in August 1959. Theory and experiment agree satisfactorily in this case also if one assumes a solar cycle variation of extreme ultraviolet solar radiation comparable with that observed for the 10-cm radio flux.