Atmospheric Noise From 20 Hz to 30 kHz

This paper discusses measurements of atmospheric noise which have been made at various times during the past two years in Malta, G.C.; Point Barrow, Alaska; Boulder, Colorado; Tokyo, Japan; Hawaii; Miami, Florida; and at various locations throughout Central and South America. Most of the measurements were average measurements of the vertical electric field intensity and amplitude probability distributions of the vertical electric fields. The atmospheric noise spectra obtained at these widely spaced locations over this large frequency range provide a good basis for rough estimates of noise field intensities at any global location. The results correlate well with lightning spectra and propagation attenuation coefficients. The amplitude probability distributions provide interesting and useful information regarding the characteristics of the noise and are used to convert the average measurements to rms values. These are some of the first amplitude probability distributions obtained throughout this frequency range. Subsurface noise spectra have been computed for several earth models as an aid to subsurface communicators.