Ionospheric D region parameters obtained using VLF measurements in the South Pacific region

Kumar, Abhikesh and Kumar, Sushil (2020) Ionospheric D region parameters obtained using VLF measurements in the South Pacific region. Journal of Geophysical Research: Space Physics, 125 . pp. 1-18. ISSN 2156-2202

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Abstract

The diurnal variations in the phase and amplitude of NWC, NPM, and NLK very low frequency (VLF) transmissions received at Suva, Fiji, have been modeled using the Long Wave Propagation Capability (LWPC V2.1) code to determine the ionospheric D region parameters, H΄ (reference height) and β (rate of increase of electron density with height), for different daytime and nighttime conditions along the transmitter-receiver great circle paths (TRGCPs). Measured VLF signal amplitude and phase show explicit variation over the day and nighttime along the TRGCP, also revealing amplitude minima and phase steps during sunrise and sunset as the day/night terminator traverses the TRGCP. While the daytime signal strength is reasonably smooth, at nighttime, the signal exhibits a great deal of variability. For three signal paths, the mean daytime H΄ and β were found to be 70.7 km and 0.40 km-1, respectively, while nighttime mean values of these parameters were found to be 84.2 km and 0.68 km-1, respectively. The temporal and day-to-day variability of the nighttime D region parameters shows that H΄ and β ranges in between 83.0 – 85.0 km and 0.58 – 0.80 km-1, respectively. One of the possible sources of nighttime signal variability is increase in the number of modes propagating and relative complex interference between them along the TRGCPs, whereby the weaker modes also become significant at night due to reduced attenuation. In addition, the variations in the nighttime D region itself may be a cause of high signal variability.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science, Technology and Environment (FSTE) > School of Engineering and Physics
Depositing User:	Abhikesh Kumar
Date Deposited:	28 Jan 2020 22:40
Last Modified:	28 Jan 2020 22:42
URI:	https://repository.usp.ac.fj/id/eprint/11949

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