scholarly journals Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra

2007 ◽  
Vol 7 (5) ◽  
pp. 625-628 ◽  
Author(s):  
A. Rozhnoi ◽  
M. Solovieva ◽  
O. Molchanov ◽  
P.-F. Biagi ◽  
M. Hayakawa
Keyword(s):  
Gravity Waves ◽  
Fresnel Zone ◽  
Signal Amplitude ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Atmospheric Gravity Waves ◽  
Period Range ◽  
Before And After ◽  
Atmospheric Gravity ◽  
Large Earthquakes

Abstract. We analyze variations of the LF subionospheric signal amplitude and phase from JJY transmitter in Japan (F=40 kHz) received in Petropavlovsk-Kamchatsky station during seismically quiet and active periods including also periods of magnetic storms. After 20 s averaging, the frequency range of the analysis is 0.28–15 mHz that corresponds to the period range from 1 to 60 min. Changes in spectra of the LF signal perturbations are found several days before and after three large earthquakes, which happened in November 2004 (M=7.1), August 2005 (M=7.2) and November 2006 (M=8.2) inside the Fresnel zone of the Japan-Kamchatka wavepath. Comparing the perturbed and background spectra we have found the evident increase in spectral range 10–25 min that is in the compliance with theoretical estimations on lithosphere-ionosphere coupling by the Atmospheric Gravity Waves (T>6 min). Similar changes are not found for the periods of magnetic storms.

scholarly journals A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

1997 ◽  
Vol 15 (8) ◽  
pp. 1048-1056 ◽  
Author(s):  
R. L. Balthazor ◽  
R. J. Moffett
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Ionospheric Disturbance ◽  
Magnetic Equator ◽  
Ionospheric Disturbances ◽  
Atmospheric Gravity Waves ◽  
Opposite Hemisphere ◽  
Travelling Ionospheric Disturbances ◽  
F Region ◽  
Atmospheric Gravity

Abstract. A global coupled thermosphere-ionosphere-plasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs) and associated travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A 'fast' dominant mode and two slower modes are identified. We find that, at the magnetic equator, all the clearly identified modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged velocity. At F-region altitudes the 'fast' AGW has the largest amplitude, and when northward propagating and southward propagating modes interfere at the equator, the TID (as parameterised by the fractional change in the electron density at the F2 peak) increases in magnitude at the equator. The amplitude of the TID at the magnetic equator is increased compared to mid-latitudes in both upper and lower F-regions with a larger increase in the upper F-region. The ionospheric disturbance at the equator persists in the upper F-region for about 1 hour and in the lower F-region for 2.5 hours after the AGWs first interfere, and it is suggested that this is due to enhancements of the TID by slower AGW modes arriving later at the magnetic equator. The complex effects of the interplays of the TIDs generated in the equatorial plasmasphere are analysed by examining neutral and ion winds predicted by the model, and are demonstrated to be consequences of the forcing of the plasmasphere along the magnetic field lines by the neutral air pressure wave.

Search for Atmospheric Gravity Waves induced by the Eclipse of June 30, 1973

Nature ◽  
1973 ◽  
Vol 246 (5433) ◽  
pp. 412-413 ◽  
Author(s):  
J. E. BECKMAN ◽  
J. I. CLUCAS
Keyword(s):  
Gravity Waves ◽  
Atmospheric Gravity Waves ◽  
Atmospheric Gravity

Characterising Atmospheric Gravity Waves on Mars using Mars Express OMEGA images – a preliminary study

2021 ◽  
Author(s):  
Francisco Brasil ◽  
Pedro Machado ◽  
Gabriella Gilli ◽  
Alejandro Cardesín-Moinelo ◽  
José E. Silva ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Atmospheric Gravity Waves ◽  
Mars Express ◽  
Preliminary Study ◽  
Atmospheric Gravity

Asymptotic stability of a polar vortex perturbed by harmonic waves describing atmospheric gravity waves circulating in an equatorial plane of a spherical planet

2018 ◽  
Vol 13 (4) ◽  
pp. 36
Author(s):  
Ranis Ibragimov ◽  
Pirooz Mohazzabi ◽  
Rebecca Roembke ◽  
Justin Van Ee
Keyword(s):  
Shallow Water ◽  
Gravity Waves ◽  
Equatorial Plane ◽  
Polar Vortex ◽  
Water Model ◽  
Large Radius ◽  
Atmospheric Gravity Waves ◽  
Nonstationary Motion ◽  
Two Parameters ◽  
Atmospheric Gravity

We examine stability of the vortex that represents one particular class of exact solution of a a nonlinear shallow water model describing atmospheric gravity waves circulating in an equatorial plane of a spherical planet. The mathematical model is represented by a two-dimensional free boundary Cauchy–Poisson problem on the nonstationary motion of a perfect uid around a solid circle with a sufficiently large radius so that the gravity is directed to the center of the circle. It is shown that the model admits two functionally independent nonlinear systems of shallow water equations. Two essential parameters that control stability of the vortex for both systems are identified. The order of their importance is analyzed and it is shown that one of the systems is more resistant to small perturbations and remains stable for larger range of these two parameters.

scholarly journals Spectral variability in high frequency in sea level and atmospheric pressure on Buenos Aires Coast, Argentina

2017 ◽  
Vol 65 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Iael Perez ◽  
Dragani Walter
Keyword(s):  
Gravity Waves ◽  
Atmospheric Pressure ◽  
Buenos Aires ◽  
Numerical Models ◽  
Spectral Energy ◽  
Spectral Variability ◽  
Atmospheric Gravity Wave ◽  
Atmospheric Gravity Waves ◽  
Atmospheric Gravity ◽  
Low Activity

Abstract There are some observational evidences which support that atmospheric gravity waves constitute an efficient forcing for meteorological tsunamis (meteotsunamis) along the coast of Buenos Aires, Argentina. Meteotsunamis and atmospheric gravity waves, which propagate simultaneously on the sea surface and the atmosphere, respectively, are typical examples of non-stationary geophysical signals. The variability of meteotsunamis and atmospheric gravity waves recorded at Mar del Plata was investigated in this paper. Results obtained in this work reinforce the idea of a cause (atmospheric gravity waves) effect (meteotsunami) relationship, because wavelet spectra obtained from both signals resulted quite similar. However, several very short episodes of mod-erate/low activity of atmospheric gravity waves were detected without detecting meteotsunami activity. On the other hand, it was found that atmospheric gravity wave spectral energy can appear in the wavelets as a single or multiple burst as relatively long and irregular events or as regular wave packets. Results obtained in this paper provide original spectral data about atmospheric gravity waves along the coast of Buenos Aires. This information is useful to be included in realistic numerical models in order to investigate the genesis of this complex atmosphere-ocean interaction.

scholarly journals Climatology of Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) Observed with GPS Networks in the North African Region

2020 ◽  
Author(s):  
Temitope Seun Oluwadare ◽  
Norbert Jakowski ◽  
Cesar E. Valladares ◽  
Andrew Oke-Ovie Akala ◽  
Oladipo E. Abe ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Occurrence Rate ◽  
Ionospheric Disturbances ◽  
North African ◽  
African Region ◽  
Atmospheric Gravity Waves ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances ◽  
The North ◽  
Atmospheric Gravity

Abstract We present for the first time the climatology of medium-scale traveling ionospheric disturbances (MSTIDs) by using Global Positioning System (GPS) receiver networks on geomagnetically quiet days (Kp ≤ 3) over the North African region during 2008-2016. The MSTIDs appear frequently as oscillating waves or wave-like structures in electron density induced by the passage of Atmospheric Gravity Waves (AGW) propagating through the neutral atmosphere and consequently, causing fluctuation in the ionospheric Total Electron Content (TEC). The TEC perturbations (dTEC) data are derived from dual frequency GPS-measurements. We have statistically analyzed the MSTIDs characteristics, occurrence rate, seasonal behavior as well as the interannual dependence. The results show a local and seasonal dependence of nighttime and daytime MSTIDs. The propagation direction is predominantly towards the South (equatorward), MSTIDs event period is (12 ≤ period ≤ 53 mins), and dominant amplitude (0.08 ≤ amp ≤ ~1.5 TECU), with a propagation velocity higher at daytime than nighttime. The amplitudes of the MSTIDs increase with solar activity. The local MSTIDs Spatio-temporal heat reveals variability in disturbance occurrence time, but seems to be dominant within the hours of (Northwest: 1200–1600 LT) and (Northeast: 1000–1400 LT) in December solstice during daytime, and around (NW: 2100–0200 LT) and (NE: 1900–0200 LT) in June solstice, but get extended to March equinox during solar maximum (2014) during the nighttime. The time series of MSTIDs regional distribution map is also generated. Atmospheric gravity waves (AGW) seems to be responsible for the daytime MSTIDs occurrence.

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