Measurements and interpretation of low-energy photoelectrons

Abstract

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.

Calculated photoelectron pitch angle and energy spectra

“…Several theoretical studies (Hoegy et al, 1965;Nisbet, 1968;Henry and McElroy, 1968;Dalgarno et al, 1969;Rees et al, 1969;Banks and Nagy, 1970;Nagy and Banks, 1970;Takayanagy and Itikawa, 1970;Cicerone and Bowhill, 1971a;Dalgarno and Lejeune, 1971) have progressively improved our knowledge of the energy spectrum of photoelectrons in the ionosphere. In parallel, experimental studies (Shea et al, 1968;Yngvesson and Perkins, 1968;Rao and Maier, 1970;Heikkila, 1970;Evans and Gastman, 1970;Doering et al, 1970;Cicerone and Bowhill, 1971b;Knudsen and Sharp, 1972;Galperin et al, 1972) have provided valuable data for comparison with the theoretical results.…”

Thermal electron energy distribution measurements in the ionosphere

“…The energy distribution of the ionospheric electron population has been studied extensively, both theoretically (Hanson and Johnson, 1961;Hanson, 1963;Dalgarno et al, 1963;Hoegy et al, 1965;Geisler and Bowhill, 1965;Nisbet, 1968;Fontheim et aL, 1968;Duboin et al, 1968;Whitten, 1968;Dalgarno et al, 1969;Banks and Nags, 1970;Nagy and Banks, 1970;Nagy and Banks, 1971;Cicerone and Bowhill, 1971;Dalgarno and Lejeune, 1971) and experimentally (Yngvesson and Perkins, 1968;Shea et al, 1968;Rao and Donley, 1969;Evans and Gastman, 1970;Rao and Maier, 1970;Doering et al, 1970;Knudsen, 1972;Hays and Sharp, 1973), but many questions remain unresolved. The least understood range of energy distribution is the transition region where the distribution changes from thermal to non-thermal in character.…”

Photoelectron Fluxes Measured at Millstone Hill

“…In addition, one requires a large number of discrete levels in the retarding voltage to permit the energy spectrum of the flux to be measured. Shea et al [1968] reported similar rocket measurements of photoelectron fluxes in the energy range 11-82 ev, but only for altitudes between 130 and 156 km. Doering et al [1970] have flown an electron spectrometer to nearly 300 km, measuring electron fluxes in the energy range 4-50 ev.…”