Latitudinal variation of differential photoelectron flux at 560-kilometers altitude

Abstract

Differential photoelectron fluxes are reported for energies of 14, 23, 42, 79, and 152 ev at an altitude of 560 km, a local time of basically 1200, and a latitude range of 70°S to 60°N. The flux measurements were made with three retarding potential analyzers flown on the OVI-18 satellite. The results presented are restricted to the daylight portions of two nonconsecutive orbits on March 22, 1969. The only latitudinal structure exhibited by the differential photoelectron flux is a decrease of a factor of 2 from high to low latitude. The minimum probably occurs at the magnetic equator. The differential-flux energy spectrum is in satisfactory agreement with what few experimental results have been reported by others. The flux decreases with energy somewhat slower than is predicted by theoretical calculations at the higher energies. The particle and energy fluxes between 8- and 100-ev energy at 560-km altitude derived from the results are 7.7 × 108 cm−2 sec−1 and 1.3 × 1010 ev cm−2 sec−1, respectively.