Development of Improved Ionospheric Empirical Model and Software for HF Ray Tracing

We developed two new global empirical models of the F2 layer critical frequency that discribe the main features of high latitude ionosphere in details: (1) Main Ionospheric Trough (MIT) model based on satellite data of topside ionosphere sounding and in-situ measurements; (2) CHanged of the foF2 calculation in IRI model (Kaliningrad version) - CHIRIK model based on radio occultation measurements. Using radio occultation and ground-based ionosonde database with an archive of F10.7 values we obtained the F10.7-optimized index for better global reproduction of the foF2 dependence on solar activity for all temporal intervals. Another applied product of our team is the ray tracing technique in 3D weakly inhomogeneous ionosphere.