Study of topside electron density profiles obtained by cosmic satellites and an ionosonde over Cyprus during a four year period

The determination of the ionospheric electron density profile below the electron density peak (bottomside) has been traditionally conducted by ground-based ionosondes, which probe the ionosphere up to the maximum electron density and define the profile above the peak (topside) using functions which extrapolate the profile above the peak. An alternative modern technique for measuring electron density profiles is the GPS Radio Occultation, conducted by means of signals transmitted by GPS satellites and received by LEO satellites. The FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) is such a system operating since 2006. In this paper a comparison of the topside electron density profiles over Cyprus is investigated in terms of these two different measurement techniques, within a period of four years. The ability of the International Reference Ionosphere model (IRI-2012) to represent the topside electron density profile is also examined.