Solar flare effects on D ‑ region ionosphere using VLF measurements during low ‑ and high ‑ solar activity phases of solar cycle 24

Kumar, Abhikesh and Kumar, Sushil (2018) Solar flare effects on D ‑ region ionosphere using VLF measurements during low ‑ and high ‑ solar activity phases of solar cycle 24. Earth, Planets and Space, 70 (29). NA. ISSN 1343-8832

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Abstract

The effects of solar flares on the propagation of subionospheric VLF signals from NWC and NLK transmitter stations monitored at a low latitude station, Suva (18.2° S, 178.4° E), Fiji, between December 2006 and December 2010 (an unprecedented solar minimum of solar cycles 23 and 24) and between January 2012 and December 2013 (moderate solar activity at the peak of solar cycle 24) have been analyzed to find solar flare-time D-region changes. The amplitude and phase enhancements associated with solar flares were observed in the signals from both stations which is due to an increase in the electron density of the D-region as a result of extra ionization caused by the solar flares. The solar flare-induced perturbations in both the amplitude and phase of VLF signals were used to determine D-region ionospheric parameters: H′ (the ionospheric reflection height) and β (rate of increase of electron density with height) using Long Wave Propagation Capability (LWPC) V2.1 modeling. A comparative analysis of the ionospheric D-region parameter changes carried out for this location shows a greater increase in β and decrease in H′ during low solar activity than during periods of moderate solar activity period, for the same class of flares. Our results also show greater differences in the values of β and H' for strong flares in comparison to weak flares under both low and moderate solar activity conditions.

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:	23 Feb 2018 00:10
Last Modified:	23 Feb 2018 00:10
URI:	http://repository.usp.ac.fj/id/eprint/10549

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