Role of lower thermospheric neutral concentration and F2-region ion drifts in the peak electron densities

Data of three simultaneously measured ionospheric parameters, namely, the ion-neutral collision frequency in the lower thermosphere, and ion drift and electron concentration in the F2-region, taken from the incoherent scatter radar measurements at Arecibo for the period August 1974-May 1977, have been analyzed. The analysis shows that variability in peak electron density cannot be explained on the basis of changes in the F-region vertical ion drift alone. Changes in neutral concentration, which are seen in the ion-neutral collision frequency in the lower thermosphere, need also be considered.