Conjugate photoelectron fluxes observed on Atmosphere Explorer C

Abstract

High resolution energy spectra of the flux of precipitating photoelectrons which arise from solar illumination of the area near the magnetic conjugate point have been measured with the Photoelectron Spectrometer Experiment on the Atmosphere Explorer C Spacecraft. Conjugate photoelectrons have been observed when the spacecraft was well away from the terminator at local solar zenith angles up to 160°. The shape of the observed electron energy spectrum is almost identical to that reported for high altitude photoelectron spectra from the Atmosphere Explorer E Spacecraft by Doering et al., 1976. Identification of the residual spectral features in the energy spectra of the conjugate photoelectrons shows that to within the experimental uncertainty of ± 1 eV, the photoelectrons from the magnetic conjugate point have not experienced any acceleration. The magnitude of the observed conjugate photoelectron flux varies considerably between passes, but in some cases the 250 km flux has been observed to be as much as half of the magnitude of the escaping photoelectron flux at 300 km near the sunlit conjugate point. Observations of the precipitating and backscattered flux provide a direct measurement of the low energy (10 eV ‐ 60 eV) electron albedo.