Attenuation Characteristics of Smooth Type Atmospheric Waveforms

Abstract

Quasi-sinusoidal waveforms of distant atmospherics recorded at night were Fourier analysed using an electronic digital computer to yield the amplitude spectra in the VLF range of 1-20kc/s. The relative values of attenuation coefficients, calculated from amplitude spectra have been compared with the experimental results of Hepburn and Wait's theoretical attenuation curves. The attenuation is found to be maximum at 4kc/s and minimum in the frequency range 7-12kc/s, and is in general agreement with results of Croom (1964). The attenuation is also found to increase in 12-20kc/s range, as earlier observed by Taylor and Lange (1958) and Obayashi et al (1959), and this can be explained partly by the waveguide theory (Wait, 1962). The variation of peak frequency and band width of the received atmospherics with propagation distance has also been discussed.