HF propagation modelling within the polar ionosphere

HF radio propagation via the ionosphere in the polar cap is strongly affected by the features such as patches and arcs that are present there. These effects include significant, and at times total, attenuation in the D- region and off-great circle propagation leading to delay spread, Doppler, and directional characteristics not predicted or considered by empirical prediction tools such as VOACAP. In this paper, area coverage results from a ray-tracing based simulation are presented for HF signal propagating in the polar cap. With the patches and arcs absent from the ionospheric model, the results are in agreement with VOACAP predictions. However, once the patches and arcs are included in the ionospheric model the expected area coverage is strongly modified, with the signal being received in some areas where previously it was absent and vice versa. The new simulation tool is essential for successfully modelling the prorpgation of HF radio waves in the polar cap.