IONOspheric Ray Tracing (IONORT) is an applicative software tool package for calculating a three-dimensional ray tracing of high frequency (HF) radio waves in the ionospheric medium.
IONORT runs under Windows operating systems. The corresponding software is coded in MATLAB for the input/output routines, while the integration algorithm is coded in FORTRAN. MATLAB graphical user interface (GUI), friendly managing the input needed to the integration algorithm and the corresponding numerical and graphical output, facilitates noticeably the numerical data input entry managed by the user and at the same time performs an useful two/three dimensional (2-D/3-D) visualization of the ray path. From a numerical point of view, in order to calculate the coordinates of the ray and the three components of the wave vector as dependent variables along the path, the core of the program solves a system of at least six first order differential equations, with Hamiltonian formalism, which are computed into a spherical coordinate geocentric system, where the group path is the independent variable of integration. IONORT uses a 3-D electron density representation of the ionosphere, as well as geomagnetic field and electron-neutral particle collision frequency models having validity in the area of interest. An analytical standard Chapman’s modelled ionosphere, useful mainly for testing purpose, completes the whole applicative software tool package.
IONORT-ISP system (IONOspheric Ray-Tracing – IRI-SIRMUP-Profiles) was developed and tested by comparing the recorded oblique ionograms over the radio link between Rome (41.89ºN, 12.48ºE), Italy, and Chania (35.51ºN, 24.02ºE), Greece, with IONORT-ISP synthesized oblique ionograms. As upgrade of the system: a) electron-neutral particle collisions have been included by using a collision frequency model, which consists of a double exponential profile; b) ISP model of 3-D electron density profile grid has been extended down to the altitudes of the D layer; c) the resolution in latitude and longitude of ISP model for 3-D electron density profile grid has been increased from 2°x2° to 1°x1°. Based on these updates, a new applicative software tool package, named IONORT-ISP-WC system (WC means with collisions) was developed, and a database of 33 IONORT-ISP-WC synthesized oblique ionograms was calculated for single and multiple ionospheric reflections (1 – 3 hop paths). IONORT-ISP-WC synthesized oblique ionograms were compared with both IONORT-IRI-WC synthesized oblique ionograms, generated by applying IONORT in conjunction with the 3-D International Reference Ionosphere (IRI) electron density profile grid, and the recorded oblique ionograms over the aforementioned radio link. The results obtained show that: (1) during daytime, for the lower ionospheric layers, the traces of the synthesized oblique ionograms are cut away at lower HFs because of the noteworthy HF absorption; (2) during night-time, for the higher ionospheric layers, the traces of the synthesized oblique ionograms are not cut off at lower HFs because of thr negligible HF absorption; (3) IONORT-ISP-WC MUF values are more accurate than IONORT-IRI-WC MUF values.