International Journal of Geosciences

Volume 8, Issue 9 (September 2017)

ISSN Print: 2156-8359   ISSN Online: 2156-8367

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A Study on the VLF/LF Long Term Amplitude Oscillations Associated with Frequencies 37.5 kHz and 45.9 kHz Received at Keil Longwave Monitor, Keil, Germany

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DOI: 10.4236/ijg.2017.89061    736 Downloads   1,433 Views   Citations

ABSTRACT

The middle and upper atmosphere of Earth displays many large-scale oscillations in several parameters. Of these oscillations, Atmospheric Oscillation (AO) and Semi-annual Oscillation (SAO) are prominent ones. In this work, we have analyzed the Very Low Frequency/Low Frequency (VLF/LF) data from two of the transmitters of frequency 45.9 kHz at NSY, Sicily, Italy and 37.5 kHz at Grindavik, Iceland. The selected Trasmitter-Receiver Great Circle Path (TRGCP) is middle latitude which is marine in case of Grindavik TRGCP and terrestrial in case of NSY TRGCP. The VLF/LF signals are bounced back and forth from D-layer of ionosphere (altitude at ~65 km during day and ~95 km during night) in Earth-ionospheric waveguide. This infers the presence of atmospheric oscillations as a consequence of change in ionization and recombination rates. Many works related to AO and SAO are mostly done only for equatorial region of the ionosphere and authors have reported the elegant dominancy of AO and SAO in the VLF/LF amplitude pattern over years. To our surprise, in our work it is seen that not only AO and SAO but also other oscillations are necessary to model the oscillation pattern of middle latitude ionosphere.

Cite this paper

Sharma, G. , Kandel, K. , Khadka, B. , Schnoor, P. , Bhatta, K. , Ghimire, B. and Thapa, A. (2017) A Study on the VLF/LF Long Term Amplitude Oscillations Associated with Frequencies 37.5 kHz and 45.9 kHz Received at Keil Longwave Monitor, Keil, Germany. International Journal of Geosciences, 8, 1080-1090. doi: 10.4236/ijg.2017.89061.

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