The Schumann Resonance is a set of spectrum peaks in the ELF portion of the Earth's electromagnetic field spectrum.
Schumann resonance is due to the space between the surface of the Earth and the conductive ionosphere acting as a waveguide. The limited dimensions of the earth cause this waveguide to act as a resonant cavity for electromagnetic waves in the ELF band. The cavity is naturally excited by energy from lightning strikes. Since the seventh overtone lies at approximately 60Hz, the cavity is also driven by the North American power grid.
The lowest-frequency (and highest-intensity) mode of the Schumann resonance is at a frequency of approximately 7.8 Hz. Detectable overtones extend upwards into the kilohertz range.
The phenomenon is named after physicist W. O. Schumann who predicted it mathematically in 1952.
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