Ionospheric heater beam scanning: A realistic model of this mobile source of ELF/VLF radiation

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Abstract
The generation of ELF/VLF radio waves by heating the auroral ionosphere with a powerful HF transmitter, modulated at the ELF/VLF frequency, is now well documented. Recently, results were presented of the phase of the ELF/VLF signals received at a distance of 500 km from such a source as the HF beam was deflected toward and away from the receiver by up to 37° from the vertical. The phase data were modeled assuming the source to be a simple point dipole located in the ionosphere at the point of maximum HF radiation. This simple model provided good agreement with experimental phase data only when the HF beam was deflected toward the ELF/VLF receiver. The model of the ELF/VLF generation mechanism presented here includes contributions from the majority of the HF radiation pattern illuminating the ionosphere and assumes it to be a continuous source of ELF/VLF excitation. Computations based on this new model provide excellent agreement with the experimental phase data at all beam deflection angles. The use of this model to improve the power efficiency of the generation of ELF/VLF radio waves by HF heating facilities by more than a factor of 3 is discussed.