Measurement of the daytime photoelectron energy distribution from AE‐E with improved energy resolution

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Abstract
Photoelectron energy spectra in the 150‐320 km altitude range have been obtained with the AE‐E satellite at substantial higher energy resolution than previously reported by Doering et al, Geophys. Res. Letters, 3, 129, 1976. The improvement was the result of a data analysis technique which makes use of spectra obtained from the spinning spacecraft when the potential of the sensor varies slightly with respect to the ionospheric plasma as a consequence of the v×B induced voltage in the spacecraft body. This data reduction technique has allowed the full instrumental energy resolution (ΔE/E = 2.5%) to be obtained. The results show new, weak features in the photoelectron energy spectrum and allow the determination of the line shape and area of the O and N2 304A solar radiation produced photoelectron lines as a function of altitude. The photoelectron lines are found to be essentially unbroadened by coulomb scattering below 200 km, but substantial broadening occurs by 250 km. At 300 km, the characteristic line shape due to coulomb scattering with a degradation to low energy and a sharp high energy side can be observed readily.