Commission 3: Progress in Ionospheric Radio

Abstract

The major advances in our understanding of the morphology of the D region in the last three years have come about through the application of rocket techniques. A series of rocket measurements carried out at Wallops Island [Mechtly and Smith, 1968a] at different seasons but at roughly the same solar zenith angle have shown the principal features of the seasonal variation in the electron density profile between 50 and 100 km. It appears that electron densities are lower by a factor of about 3 below 82 km on ‘normal’ winter days as compared with summer days for a solar zenith angle of 60°. The anomalous winter days of high absorption have been the subject of a separate rocket investigation [Sechrist et al., 1969], which has shown that the electron density profile is remarkably similar to that of a normal summer day and that in at least one case was associated with a pronounced temperature inversion near 70 km.