VLF radio signal perturbations during two recent solar eclipses observed from a VLF receiving station, Cooch Behar, India

Abstract

Effects of two recent solar eclipses of December 2019 and June 2020 on the Very Low Frequency (VLF) radio signal amplitudes, observed from a single receiving station at Cooch Behar (CHB), India, have been presented in this paper. Signal amplitudes of VLF transmitters such as VTX (18.2 kHz), NWC (19.8 kHz), JJI (22.2 kHz), and DHO (23.4 kHz) experienced both enhancement and reduction during the eclipse period. Depending on the eclipse obscuration over the propagation path, propagation distance, and frequency of the signal, increase and decrease of signal amplitudes were observed. The amplitude perturbation on the VLF signals was also opposite for the two eclipses on each propagation path. The possible reason behind the amplitude perturbations is the changes induced in the earth ionosphere waveguide during the solar eclipses and corresponding constructive or destructive interference that occurred between the waveguide modes of the received signal at each frequency.