Ultra-low frequency waves in Space and on Earth

A brief overview of modern ideas about the physical nature of wave variations of the geomagnetic field in the ultra-low frequency (UHF) range from fractions of MHz to the first Hz is given. The noise and fluctuations of the UHF range reflect the turbulent nature of the interaction of solar wind plasma with the Earth's magnetosphere. The excitation of some types of UHF waves is a manifestation of the resonant interaction of waves and particles in near-Earth plasma. The physics of UHF waves is based on the theoretical apparatus of plasma physics and magnetic hydrodynamics, and the experimental research base is the data from observations on satellites and ground stations. The morphological characteristics of the main types of geomagnetic pulsations are given, and then the physical mechanisms of their generation and the possible role in the course of plasma processes in the near-Earth environment are considered. Geomagnetic UHF waves turn out to be not only one of the main diagnostic tools for near-Earth space, but also an active factor affecting both the near-Earth environment and terrestrial and satellite technological systems. The presentation is intended for readers working in related fields (space technology, geophysics) who would like to get a general idea of the physics of UHF waves in near-Earth space.