Extremely Low-Frequency Electromagnetic Waves. I. Reception from Lightning

Abstract

Extremely low-frequency (ELF) radio waves (10–500 cycles) originating in lightning were received over distances in excess of 15 000 km. Transmission conditions were equally good, day or night. Propagation distances were ascertained by analysis of higher frequency components (>1700 cycles) according to known methods. The receiving antenna employed an arrangement of grounded electrodes which uniquely determined the azimuthal direction of the source. Two distinct classes of ELF pulses are described which are attributed to different conditions of propagation.