Ionospheric Modification by High Power, Obliquely Propagated HF Radio Wave Transmissions. Part 1. Experimental

Published material on heating of electrons in the ionosphere using high power transmissions at high frequencies typically used for communications and OTH radar systems, is reviewed. Although the emphasis of the reviewed experimental papers involves the oblique nature of radio transmissions, actually the important factor that differentiates these measurements from typical high power plasma heating studies is the fact that these involve underdense heating, i.e. at frequencies above the maximum plasma frequency in the ionosphere. The process of inclusion into this report necessitated a critical judgement of the published experimental results, requiring of them, either a degree of credibility and repeatability or when they have become part of the folk lore in the field of oblique heating. In the latter case, a critical review of the reported results is undertaken in light of current and best understanding of heating phenomenology.