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

Atishnal Elvin Chand,Sushil Kumar

doi:10.1109/access.2021.3072133

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.

Highlights

The propagation of Very Low Frequency (VLF, 3-30 kHz) signals over a long distance in the waveguide bounded by Earth’s surface and the D-region of the lower ionosphere is conveniently described by the means of a waveguide model
NWC transmitter signal received at Suva shows three amplitude minima during both sunrise and sunset transitions hours labeled as SR1, SR2, SR3 and SS1, SS2, SS3 (Fig. 2), respectively along the Transmitter and Receiver Great Circle Path (TRGCP)
SUMMARY AND CONCLUSION Results presented in this paper on the waveguide mode analysis of VLF waves at 19.8, 21.4, 22.2 and 24.8 kHz during different seasons for the year 2014 indicate a good consistency between experimental and theoretical values of waveguide mode parameters

Summary

Introduction

The propagation of Very Low Frequency (VLF, 3-30 kHz) signals over a long distance in the waveguide bounded by Earth’s surface and the D-region of the lower ionosphere is conveniently described by the means of a waveguide model. Collisions between charged and neutral particles are dominant in the D-region of the ionosphere. These physical interactions play a significant role in the propagation of VLF waves through the EIWG [2]. At VLF, both the upper boundary (D-region of the ionosphere) and the lower boundary (Earth’s surface) of the EIWG act as good electrical conductors having sufficient conductivities to reflect these waves when incident upon these boundaries. The guided VLF propagation from navigational transmitters undergoes a low attenuation rate (a few dB per 1000 km), has high phase and frequency stability, a high signal-to-noise ratio, and could be received at large distances from the transmitter

Objectives

Results

Discussion

Conclusion