scholarly journals Very low frequency subionospheric remote sensing of thunderstorm-driven acoustic waves in the lower ionosphere

2014 ◽  
Vol 119 (9) ◽  
pp. 5037-5045 ◽  
Author(s):  
R. A. Marshall ◽  
J. B. Snively
Keyword(s):  
Remote Sensing ◽  
Acoustic Waves ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Very Low Frequency

scholarly journals Very Low Frequency Remote Sensing Measurements of the Lower Ionosphere at Site of the United Arab Emirates

2008 ◽  
Vol 104 (1-4) ◽  
pp. 189-193
Author(s):  
Hamid M. K. Al-Naimiy ◽  
Ala A. J. Al-Douri ◽  
Abdalla A. Alnajjar ◽  
Umran Inan
Keyword(s):  
Remote Sensing ◽  
United Arab Emirates ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Very Low Frequency

scholarly journals Strange VLF bursts in northern Scandinavia: case study of the afternoon "mushroom-like" hiss on 8 December 2013

2015 ◽  
Vol 33 (8) ◽  
pp. 991-995 ◽  
Author(s):  
J. Manninen ◽  
N. G. Kleimenova ◽  
A. Kozlovsky ◽  
I. A. Kornilov ◽  
L. I. Gromova ◽  
...  
Keyword(s):  
Low Frequency ◽  
Mutual Effect ◽  
Time History ◽  
Lower Ionosphere ◽  
Wave Interaction ◽  
Recovery Phase ◽  
Frequency Wave ◽  
Left Hand ◽  
Very Low Frequency ◽  
The Right

Abstract. We investigate a non-typical very low frequency (VLF) 1–4 kHz hiss representing a sequence of separated noise bursts with a strange "mushroom-like" shape in the frequency–time domain, each one lasting several minutes. These strange afternoon VLF emissions were recorded at Kannuslehto (KAN, ϕ = 67.74° N, λ = 26.27° E; L ∼ 5.5) in northern Finland during the late recovery phase of the small magnetic storm on 8 December 2013. The left-hand (LH) polarized 2–3 kHz "mushroom caps" were clearly separated from the right-hand (RH) polarized "mushroom stems" at the frequency of about 1.8–1.9 kHz, which could match the lower ionosphere waveguide cutoff (the first transverse resonance of the Earth–ionosphere cavity). We hypothesize that this VLF burst sequence could be a result of the modulation of the VLF hiss electron–cyclotron instability from the strong Pc5 geomagnetic pulsations observed simultaneously at ground-based stations as well as in the inner magnetosphere by the Time History of Events and Macroscale Interactions during Substorms mission probe (THEMIS-E; ThE). This assumption is confirmed by a similar modulation of the intensity of the energetic (1–10 keV) electrons simultaneously observed by the same ThE spacecraft. In addition, the data of the European Incoherent Scatter Scientific Association (EISCAT) radar at Tromsø show a similar quasi-periodicity in the ratio of the Hall-to-Pedersen conductance, which may be used as a proxy for the energetic particle precipitation enhancement. Our findings suggest that this strange mushroom-like shape of the considered VLF hiss could be a combined mutual effect of the magnetospheric ULF–VLF (ultra low frequency–very low frequency) wave interaction and the ionosphere waveguide propagation.

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

2020 ◽  
Vol 38 (2) ◽  
pp. 385-394
Author(s):  
Emilia Correia ◽  
Luis Tiago Medeiros Raunheitte ◽  
José Valentin Bageston ◽  
Dino Enrico D'Amico
Keyword(s):  
Low Frequency ◽  
Lower Ionosphere ◽  
Drake Passage ◽  
Wave Period ◽  
Very Low Frequency ◽  
Reflection Height ◽  
D Region ◽  
Radio Signals ◽  
Sky Conditions ◽  
The Waves

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.

scholarly journals The Sonification of Solar Harmonics (SoSH) Project

2019 ◽  
Author(s):  
Seth Shafer ◽  
Timothy Larson ◽  
Elaine di Falco
Keyword(s):  
Acoustic Waves ◽  
Resonant Cavity ◽  
Low Frequency ◽  
Musical Instrument ◽  
The Sun ◽  
Very Low Frequency ◽  
Musical Compositions ◽  
Oscillation Modes

The Sun is a resonant cavity for very low frequency acoustic waves, and just like a musical instrument, it supports a number of oscillation modes, also commonly known as harmonics. We are able to observe these harmonics by looking at how the Sun’s surface oscillates in response to them. Although this data has been studied scientifically for decades, it has only rarely been sonified. The Sonification of Solar Harmonics (SoSH) Project seeks to sonify data related to the field of helioseismology and distribute tools for others to do the same. Creative applications of this research by the authors include musical compositions, installation artwork, a short documentary, and a full-dome planetarium experience.

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