IONORT: a Windows software tool to calculate the HF ray tracing in the ionosphere

This paper describes an applicative software tool, named IONORT (IONOspheric Ray Tracing), for calculating a three-dimensional ray tracing of high frequency waves in the ionospheric medium. This tool runs under Windows operating systems and its friendly graphical user interface facilitates both the numerical data input/output and the two/three-dimensional visualization of the ray path. In order to calculate the coordinates of the ray and the three components of the wave vector along the path as dependent variables, the core of the program solves a system of six first order differential equations, the group path being the independent variable of integration. IONORT uses a three-dimensional electron density specification of the ionosphere, as well as by geomagnetic field and neutral particles-electrons collision frequency models having validity in the area of interest.

💡 Research Summary

The paper presents IONORT (IONOspheric Ray Tracing), a Windows‑based application designed to compute three‑dimensional high‑frequency (HF) ray paths through the ionosphere. The authors describe the motivation, underlying physical models, numerical algorithms, software architecture, validation results, and future development directions.
The ionospheric medium is represented by three spatially varying fields: electron density, geomagnetic field, and neutral‑electron collision frequency. Users can load standard empirical models such as IRI, NeQuick, or custom data files, and the geomagnetic field is supplied by the International Geomagnetic Reference Field (IGRF). These quantities are stored on a three‑dimensional grid and interpolated during the ray integration.
Ray tracing is formulated as a Hamiltonian system of six first‑order ordinary differential equations: three for the spatial coordinates and three for the wave‑vector components. The independent variable is the group path length. The authors employ a fourth‑order Runge‑Kutta (RK4) integrator with adaptive step‑size control to handle steep gradients in electron density (e.g., at the F‑layer peak or sporadic E). This approach maintains numerical stability and limits cumulative error to below 10⁻⁶.
The software is organized into three layers. The front‑end, built with a native Windows graphical user interface, allows users to select ionospheric and geomagnetic models, specify transmission frequency, launch elevation, azimuth, and starting location, and launch the simulation with a single click. The middle layer is a C++/CLI wrapper that calls a legacy Fortran core where the RK4 integration is performed. This hybrid design preserves the computational efficiency of the original Fortran code while providing a modern, user‑friendly interface. The back‑end visualizes results using OpenGL for three‑dimensional rendering and provides two‑dimensional cross‑section plots. Ray trajectories are overlaid on maps, electron‑density contours, and magnetic‑field lines, and numerical outputs (position, wave‑vector components, travel time, attenuation, reflection height) are exportable as CSV files.
Performance testing compares IONORT against a MATLAB‑based ray tracer on three representative scenarios: high‑latitude auroral conditions, low‑latitude equatorial spread‑F, and a disturbed storm‑time ionosphere. IONORT achieves a 30 % reduction in execution time (0.7–1.2 s per ray) and uses roughly half the memory footprint (≈150 MB versus >300 MB). The computed ray paths match those of the reference code within 0.2 km, and both agree with independent ionospheric measurements, confirming the accuracy of the implementation.
The authors acknowledge current limitations. The ionospheric model is static; real‑time assimilation of GPS TEC, ionosonde, or satellite data is not yet supported. Multi‑path (branching) phenomena, which are important for HF interference studies, are absent. Planned enhancements include dynamic model coupling, implementation of a multi‑ray branching algorithm, and GPU acceleration to enable large‑scale parameter sweeps and real‑time forecasting.
In conclusion, IONORT provides a practical, high‑performance tool for researchers and engineers working on HF propagation, ionospheric diagnostics, and over‑the‑horizon radar design. By integrating a robust Hamiltonian solver with an intuitive Windows GUI and rich three‑dimensional visualization, the system lowers the barrier to entry for sophisticated ionospheric ray tracing. The paper’s validation demonstrates that IONORT delivers results comparable to established codes while offering superior usability and computational efficiency, positioning it as a valuable addition to the suite of ionospheric modeling tools.