Longitude features shown by topside sounder data and their importance in ionospheric mapping

Abstract

Of the seven topside-sounder satellites launched to date only two succeeded in mapping the most important peak parameter of the terrestrial ionosphere: ISS-b and INTERKOSMOS-19 (IK-19). A large number of topside ionograms were gathered by IK-19 but the major proportionof these have now been reduced to true heights. A well-adapted system of data storage has allowed Local Time mapping by measurements over essentially a single day and UT - mapping with about two months of measurements. For aeronomy as well as from a propagation viewpoint the most important finding is a systematic longitudinal effect, much greater than has been assumed hitherto.