Comparison between the measured and predicted parameters of HF radio signals propagating in the polar cap

In this paper, a statistical analysis of the observations of HF signals propagating over two paths, one that crosses the auroral oval and one in the polar cap, are compared to the prediction given by VOACAP. Large deviations in the azimuth of arrival were observed on both paths with upper-decile values of 90° for the trans-auroral oval path, and 70° for the polar cap path. For the trans-auroral path, VOACAP generally underestimates the signal strength in the presence of off-great circle propagation, while for the polar cap path, the signal strength is underestimated when VOACAP predicts propagation via a 2E mode that does not occur.