This review is devoted to ultra-low-frequency electromagnetic waves of a natural origin. A variety of frequency-modulated waves whose sources are located in the ionosphere, in the radiation belt, on the periphery of the magnetosphere, and in the solar wind in front of the magnetosphere bow shock are considered. The main focus is on the mechanisms of the formation of frequency modulation. Analysis of frequency modulation gives us information about the processes of excitation and propagation of waves, as well as about physical conditions in places of excitation and along signal propagation paths. Relevant open question about the physics of frequency-modulated waves are indicated.

Keywords: plasma, solar wind, magnetosphere, radiation belt, electromagnetic waves, ion cyclotron instability, dispersion, Doppler effect PACS: 94.20.ws, 94.30.−d, 94.30.Ms (all) DOI: 10.3367/UFNe.2020.06.038777 URL: https://ufn.ru/en/articles/2021/5/b/ 000691278700002 2-s2.0-85101635140 2021PhyU...64..452G Citation: Guglielmi A V, Potapov A S "Frequency-modulated ULF waves in near-Earth space" Phys. Usp. 64 452–467 (2021) BibTexBibNote ® (generic)BibNote ® (RIS)MedlineRefWorks Received: 29th, March 2020, revised: 9th, June 2020, accepted: 10th, June 2020 Оригинал: Гульельми А В, Потапов А С «Частотно-модулированные ультранизкочастотные волны в околоземном космическом пространстве» УФН 191 475–491 (2021); DOI: 10.3367/UFNr.2020.06.038777