Comparison of optical and incoherent scatter measurements of nighttime exospheric temperature at the magnetic equator

Abstract

During March and April 1968 the nighttime exospheric neutral temperature was measured at the Jicamarca Radio Observatory both from the Doppler width of the 6300-Å nightglow line, measured by a Fabry-Perot interferometer, and from the electron temperature, measured by incoherent scatter. The mean difference between the incoherent scatter and the optical measurements was 26K for simultaneous measurements and 31K for all measurements (compared by using the Jacchia (1971) model). Since the height of the incoherent scatter measurement was 400 km and the mean height of the 6300-Å emission was 270 km, this difference is consistent with the ∼28K temperature difference in the appropriate Jacchia (1971) atmospheric models but not with the ∼7K difference in the Jacchia (1965) models. In any case the measured difference is much smaller than the reported discrepancies between incoherent scatter and satellite-borne Langmuir probe measurements of electron temperature. The present comparison tends to support the correctness of the incoherent scatter measurements.