Whistler Wave Interactions with Space Plasmas during HF Heating of the Ionosphere at Arecibo

We demonstrate that signals at 28.5 kHz emitted from the Naval (NAU) transmitter in Puerto Rico e ectively couple into ionospheric ducts, induced/enhanced by the Arecibo HF heater, and propagate into the conjugate hemisphere as ducted whistlers. Also presented are suspected radar detections of whistler-triggered electron precipitation events. NAU-generated whistlers have intensities su cient to parametrically excite lower hybrid waves and 10-m scale ionospheric irregularities over Arecibo. Subsequent heating of electrons and ions by the lower hybrid waves yields a chain of ionospheric plasma e ects, such as airglow, short-scale density depletions, and plasma line enhancements in a range of altitudes which far exceeds that a ected by the HF heater. Whistler contamination from NAU overriding some heater-induced e ects may account for apparent discrepancies between results reported from Arecibo and other heater sites.