VLF attenuation for east-west and west-east daytime propagation using atmospherics

Daytime attenuation characteristics have been computed by comparing the amplitude spectra of atmospheric waveforms recorded at four widely separated stations. The results of these attenuation measurements are presented for the band of frequencies from 3 to 30 kc/s and involving distances of 1000 to 10,000 km. Nonreciprocity is evident from this study. Attenuation rates over sea water for east-to-west propagation were about 3 db/1000 km greater for frequencies below 8 kc/s, and about 1 db/1000 km greater for frequencies above 10 kc/s, than for west-to-east propagation. East-to-west attenuation rates over land were about 1 db/ 1000 greater than for over sea water.