A Comparative Analysis of ELF/VLF Wave Generation at HAARP

Abstract:

In November and December of 2018, a series of ionospheric heating experiments were performed at the High-frequency Active Auroral Research Program (HAARP) facility. One of the goals of these experiments was to generate extremely low frequency/very low frequency (ELF/VLF, 3 Hz – 30 kHz) radio waves by modulated high frequency (HF) heating of the naturally occurring auroral electrojet currents above the array. Three types of heating transmissions are compared: synthesized-two-frequency (STF) modulation, beat-wave modulation, and standard amplitude modulation. At different times, X-mode and O-mode polarizations were employed, different HF frequencies were transmitted, and the HF beams were directed vertically and toward magnetic zenith. We present a preliminary analysis of these experiments and employ ELF/VLF time-of-arrival analysis to identify ELF/VLF source height dependencies on HF frequency, HF polarization, and HF beam direction.