Characterization of gravity waves in the lower ionosphere using very low frequency observations at Comandante Ferraz Brazilian Antarctic Station
<p>The goal of this work is to investigate the gravity wave (GW) characteristics in the low ionosphere using very low frequency (VLF) radio signals. The spatial modulations produced by the GWs affect the conditions of the electron density at reflection height of the VLF signals, which produce...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-03-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/38/385/2020/angeo-38-385-2020.pdf |
| Summary: | <p>The goal of this work is to investigate the gravity wave (GW)
characteristics in the low ionosphere using very low frequency (VLF) radio
signals. The spatial modulations produced by the GWs affect the conditions
of the electron density at reflection height of the VLF signals, which
produce fluctuations of the electrical conductivity in the D region that can
be detected as variations in the amplitude and phase of VLF narrowband
signals. The analysis considered the VLF signal transmitted from the US
Cutler, Maine (NAA) station that was received at Comandante Ferraz Brazilian
Antarctic Station (EACF, 62.1<span class="inline-formula"><sup>∘</sup></span> S, 58.4<span class="inline-formula"><sup>∘</sup></span> W), with its great circle
path crossing the Drake Passage longitudinally. The wave periods of the GWs
detected in the low ionosphere are obtained using the wavelet analysis
applied to the VLF amplitude. Here the VLF technique was used as a new
aspect for monitoring GW activity. It was validated comparing the wave
period and duration properties of one GW event observed simultaneously with
a co-located airglow all-sky imager both operating at EACF. The statistical
analysis of the seasonal variation of the wave periods detected using VLF
technique for 2007 showed that the GW events occurred all observed days,
with the waves with a period between 5 and 10 min dominating during night
hours from May to September, while during daytime hours the waves with
a period between 0 and 5 min are predominant the whole year and dominate
all days from November to April. These results show that VLF technique is a
powerful tool to obtain the wave period and duration of GW events in the low
ionosphere, with the advantage of being independent of sky conditions, and it can
be used during the whole day and year-round.</p> |
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| ISSN: | 0992-7689 1432-0576 |