Rocket measurement of thermospheric photoelectron energy spectra

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Abstract
Relative values of thermospheric photoelectron energy distributions between 2 and 100 eV were measured over the altitude range 100–220 km by using a 127° cylindrical electrostatic deflection analyzer flown on a rocket. The measured photoelectron spectra display distinct features that are theoretically predicted (Victor et al., 1976; Jasperse, 1977) and are similar to those obtained in recent satellite experiments (Doering et al., 1975, 1976). The valleylike structure in the energy range 2–5 eV attributed to resonant‐vibrational excitation of N2 was observed in more detail and over a greater altitude range than that measured previously. The prominence of this low‐energy valley decreases with increasing altitude above about 150 km and disappears above 200 km, in general agreement with theory. However, in contrast to theoretical predictions, the low‐energy valley also appears to become less prominent as altitude decreases below about 140 km, down to the lowest observations at 100 km.