Characterization of gravity waves in the lower ionosphere using very low frequency observations at Comandante Ferraz Brazilian Antarctic Station

Abstract

Abstract. 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∘ S, 58.4∘ 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.

Review of Environmental Monitoring by Means of Radio Waves in the Polar Regions: From Atmosphere to Geospace

“…The VLF measurements at Comandante Ferraz Brazilian Antarctic Station started in 1984, and digitally since 2006. In addition to the investigation of the ionospheric forcing from space, the VLF technique has also been used to investigate the ionospheric effects produced by the impact of the planetary and gravity waves generated below the ionosphere (Correia et al , 2013b(Correia et al , 2020.…”

Preseismic Perturbations and their Inhomogeneity as Computed from Ground‐ and Space‐Based Investigation during the 2016 Fukushima Earthquake

“…The evidence of AGW can also be computed from the nighttime VLF/LF signal by Fourier or wavelet analysis [27,29,36,[51][52][53][54][55]. The periodic thrust produced by the gravity waves can affect the lower ionospheric characteristics by modulating the electron density profile and effective reflection height of VLF signals.…”