Comparison between F3/C Radio Occultation and Digisonde Bottomside Plasma Frequency Over Cyprus

The objective of this study is to perform a comparison between bottomside 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 measurements from bottomside electron density profiles from manually scaled ionograms from Nicosia. This comparison demonstrates that there is a systematic underestimation of Digisonde plasma frequency (as compared to F3/C plasma frequency) in the bottomside and that the relative difference between F3/C and Digisonde plasma frequency increases with decreasing altitude (below the F-layer peak).