Multi-hop whistler-mode ELF/VLF signals and triggered emissions excited by the HAARP HF heater

Modulated heating of the lower ionosphere with the HAARP HF heater is used to excite 1-2 kHz signals observed on a ship-borne receiver in the geomagnetic conjugate hemisphere after propagating as ducted whistler-mode signals. These 1-hop signals are believed to be amplified, and are accompanied by triggered emissions. Simultaneous observations near (~30 km) HAARP show 2-hop signals which travel to the northern hemisphere upon reflection from the ionosphere in the south. Multiple reflected signals, up to 10-hop, are detected, with the signal dispersing and evolving in shape, indicative of re-amplification and re-triggering of emissions during successive traversals of the equatorial interaction regions.