Comparison between RO and Digisonde topside plasma frequency over European Digisonde stations

Abstract

The objective of this study is to perform a comparison between topside electron density measurements from the Global Navigation Satellite System (GNSS) radio occultation (RO) FORMOSAT3/COSMIC (F3/C) constellation mission along with collocated (in space and time) plasma frequency values from topside electron density profiles from manually scaled ionograms from European Digisondes (at Chilton, Juliusruh, Moscow, Dourbes, Pruhonice and by El Arenosillo, Roquetes, Rome, San Vito, Athens and Nicosia). This comparison demonstrates that there is a systematic underestimation of Digisonde plasma frequency (as compared to F3/C Ne) in the topside and that the relative difference between COSMIC and Digisonde plasma frequency increases with altitude (above the F-layer peak).