“…In addition, ambient power‐line harmonics (Fedorov et al., 2021 ; Park & Helliwell, 1978 ), intentional VLF transmissions from terrestrial power lines and high‐power VLF transmitters can leak into space where they may interact with energetic electrons in the Earth's magnetosphere (Hua et al., 2020 ; Ma et al., 2017 ; Ross et al., 2019 ). Several man‐made facilities have been developed to study this wave‐particle‐interaction process including VLF transmitters (Helliwell, 1977 , 1988 ), high‐power HF facilities for modulations of natural ionosphere currents in the ionosphere (Guo et al., 2021 ), large satellite antennas driven by high power signal generators, electron beams that are modulated at VLF rates, and high‐speed neutral injections that rapidly photoionize in sunlight (Borovsky & Delzanno, 2019 ; Sotnikov et al., 2018 ). These techniques require dedicated, expensive engineering efforts for design, construction, and testing before they are deployed on the ground or in space.…”