Earth-Ionosphere Waveguide Model Parameters Using VLF Transmissions Received in the South Pacific Region

Abstract

Very Low Frequency (VLF) signals form a novel tool to study the earth-ionosphere waveguide mode parameters. The waveguide model analysis of four VLF transmitter signals: 1) NWC, Australia (19.8 kHz), 2) NPM, Hawaii (21.4 kHz), 3) JJI, Elbino, Japan (22.2 kHz) and 4) NLK, Seattle, USA (24.8 kHz) propagating over long propagation paths to Suva, Fiji, has been carried out using the VLF amplitude and phase data recorded during 2014. The Transmitter Receiver Great Circle Path distances to the receiving station are 6.69 Mm for NWC, 5.07 Mm for NPM, 7.50 Mm for JJI and 9.43 Mm for NLK transmitter signal. Our results show good consistency between experimental and theoretical values of waveguide mode parameters for the west-east (W-E) (NWC/JJI-Suva) and east-west (E-W) (NLK/NPM-Suva) component of the VLF propagation paths. The waveguide mode parameters estimated in our work were found to be higher for the E-W component of the VLF propagation path compared to the W-E component path. We have also employed Long Wave Propagation Capability (V2.1) code to estimate the daytime and nighttime signal strength and daytime to nighttime signal strength ratio ( $E_{\mathrm {DN}}$ ) for all four VLF transmitter signals and found that the nighttime signal strength is generally higher compared to the daytime.