Validation of the European Ionosonde Service nowcasting foF2 maps over the eastern Mediterranean

Abstract

The Cyprus ionosonde (Digisonde) has been operating since 2009. Therefore it has been monitoring ionospheric conditions over the eastern Mediterranean region for more than 14 years. It is the only ionosonde operating in the area and it does not contribute to any existing European database and subsequently has not been utilised in the frames of any Space Situational Awareness (SSA) program. In the frames of the European Space Agency (ESA) activity “Potential Enhancements in Ionospheric Monitoring under SSA (PEIMSSA)” a quantitative validation of the the European Ionosonde Service (EIS) was undertaken. This validation is based on 8 years of manually scaled F-layer critical frequency (foF2) data that was compared with the corresponding interpolated values from EIS nowcasting foF2 maps over Europe. The aim of the study was to quantify EIS accuracy over the eastern Mediterranean with respect to manually scaled foF2 data from the Cyprus Digisonde. The findings of this study suggest that there are systematic underestimation-overestimation features that appear in all years considered. The most notable feature is an overestimation of EIS over Cyprus in the interval 00:00–03:00 UT, from October to March and an underestimation from April to August. An underestimation is also systematically observed in the interval, 14:00–16:00 UT from April to December and 22:00–23:00 UT in September to October. This overestimation-underestimation pattern is evident throughout all years under investigation with a higher mean % difference discrepancy in low than in high solar activity years. During disturbed days we observe, for all years, EIS slightly overestimating Cyprus foF2 values.