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[1] Ionospheric effects of energetic electron precipitation induced by controlled injection of VLF signals from a ground based transmitter are observed via subionospheric VLF remote sensing. The 21.4 kHz NPM transmitter in Lualualei, Hawaii is keyed ON-OFF in 30 minute periodic sequences. The same periodicity is observed in the amplitude and phase of the sub ionospherically propagating signals of the 24.8 kHz NLK (Jim Creek, Washington) and 25.2 kHz NLM (LaMoure, North Dakota) transmitters measured at Midway Island. Periodic perturbations of the NLK signal observed at Palmer, Antarctica suggest that energetic electrons scattered at longitudes of NPM continue to be precipitated into the atmosphere as they drift toward the South Atlantic Anomaly. Utilizing a model of the magnetospheric waveparticle interaction, ionospheric energy deposition, and subionospheric VLF propagation, the precipitated energy flux induced by the NPM transmitter is estimated to peak at L $ 2 and $ 1.6 Â 10 À4 ergs s À1 cm À2 . Citation: Inan,

We present calibrated measurements of ELF waves generated by modulated HF heating of the auroral electrojet by the High frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska, and detected after propagating more than 4400 km in the Earth‐ionosphere waveguide to Midway Atoll. The magnitude of the 2125 Hz wave received at Midway Atoll is consistent with the radiation from a horizontal dipole located at the altitude of the maximum Hall conductivity variation (created by modulated HF heating) and radiating ∼4–32 W. The HF‐ELF conversion efficiency at HAARP is thus estimated to be ∼0.0004–0.0032% for the 2125 Hz wave generated using sinusoidal amplitude modulation.

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.

[1] Modulated HF heating of the auroral electrojet is used to inject ELF signals into the magnetosphere that are observed on the low altitude DEMETER spacecraft. The HF heater is a component of the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska, (located at L $ 4.9). Simultaneous observations of all six components of the ELF electromagnetic fields on the DEMETER spacecraft are used to estimate the total ELF power radiated downward into the Earth-ionosphere waveguide. ELF signals generated by the HAARP heater are also simultaneously observed at a nearby ground-based site, allowing a comparison of the ELF power in the Earthionosphere waveguide versus that detected on DEMETER.The estimated values of power onboard DEMETER at different frequencies range from 0.32W to 4W, while the values of power estimated from a ground receiver at a distance of 36 km from HAARP range from 2.71W to 4