Electron Collision Frequency in the F-region of the Ionosphere

Abstract

EXPERIMENTAL measurements of the collision frequency of electrons in the lower ionosphere have been made by a variety of ground-based and rocket techniques. In general there is good agreement up to about 100 km between these and values calculated from atmospheric properties and laboratory measurements of electron collision cross-sections (see, for example, ref. 1). Above 100 km, as Thrane and Piggott have pointed out, however, there are significant difficulties in providing reliable estimates of the collisional frequency and, in particular, there seems to be some considerable discrepancy between calculated values based on the variation of atmospheric pressure with height and experimental values based on ground-based radio wave propagation studies. We have recently re-examined the problem of determining the collision frequency at levels above the E-layer and in this report we outline an approach based on simultaneous absorption and h′(f) measurements.