Audio-Frequency Spectrum of Atmospherics

Abstract

THE observations on the low-frequency or ‘slow tail’ component in the waveform of an atmospheric described recently by Hepburn and Pierce in Nature¹ is of particular interest to us since we have been making similar observations for some years. The earlier observations made by Appleton and Chapman² dealt with the evolution of atmospheric waveforms. It was shown that many atmospherics consist of an oscillatory portion, composed of a sequence of quasi half-cycles of increasing duration, followed by a ‘slow tail’ of usually two rounded half-cycles. The oscillatory portion was found to move ahead of the slower disturbance as the distance of propagation increased. Further, the quasi half-period of the components of the oscillatory portion was found to obey a relation different from the ‘slow tail’.