This paper describes the local and long‐path very low frequency/extremely low frequency (VLF/ELF) radiation produced by modulation of the ionospheric current systems during high frequency (HF) heating of the ionospheric D region and very high frequency (VHF) heating of the equatorial electrojet. A brief description of the theory and the geometry of the heating experiment is followed by a discussion of local VLF/ELF radiation detected near the HF transmitter locations at Arecibo, Puerto Rico, and at the Jicamarca Radar Observatory near Lima, Peru. Long‐path detection of VLF/ELF radiation initially recorded on a path from Tromso, Norway, to the Pennsylvania State University in 1981 is updated with current experimental long‐path results over paths between Jicamarca, Peru, and Salinas, Puerto Rico, as well as Arecibo, Puerto Rico, to the Pennsylvania State University.
This paper describes a diagnostic system developed for the study of radio signals at frequencies below 8 kHz. Of specific interest are emissions produced by high-frequency heating of the ionosphere which modulates natural ionospheric current systems. Dual receivers allow independent reception on orthogonal loop antennas, and microcomputer systems provide real-time data acquisition and processing of all experimental data. Provisions are also made for automatic control of modulating frequency applied to the heating transmitters; operating frequencies may be changed on a preset schedule in tandem with receiver tuning.
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