Further ionosonde observations of ionospheric modification by a high-powered HF transmitter

Abstract

Ionospheric modification by high-powered HF transmissions has produced many different radio and optical effects, some of which have been reported. Additional effects observed with ionosondes are presented here in more detail so that researchers interested in ionospheric phenomena can examine some of the major and subtle changes and then, perhaps, contribute to new understanding about ionospheric processes. The data shown were obtained with O-mode excitation and provide examples of (a) major deformation of nighttime ionospheric structure, (b) prompt, strong, wideband attenuation of diagnostic O waves on all frequencies exceeding the modifier frequency, and (c) daytime creation of artificial spread F, extending over a range of about 200-km virtual height, and showing different responses in the F1 and F2 regions.