Hiss (electromagnetic)

VLF spectrogram of electromagnetic hiss, as received by the Stanford University VLF group's wave receiver at Palmer Station, Antarctica. The hiss can be seen between 500 Hz and 4000 Hz, sandwiched between components of sferics

Electromagnetic hiss is a naturally occurring Extremely Low Frequency/Very Low Frequency electromagnetic wave (i.e., 300 Hz – 10 kHz) that is generated in the plasma of either the Earth's ionosphere or magnetosphere. Its name is derived from its incoherent, structureless spectral properties which, when played through an audio system, sound like white noise (hence the onomatopoetic name, "hiss").