Acoustic-gravity modons in the atmosphere

1995 ◽  
Vol 13 (9) ◽  
pp. 973-975 ◽  
Author(s):  
L. Stenflo ◽  
Y. A. Stepanyants
Keyword(s):  
Internal Waves ◽  
Gravity Waves ◽  
Low Frequency ◽  
Horizontal Direction ◽  
Acoustic Gravity Waves ◽  
Dipole Vortex ◽  
Vortex Solutions

Abstract. It is shown that the equations governing low-frequency acoustic-gravity waves in a stable stratified atmosphere can have localized dipole-vortex solutions (modons). They propagate in the horizontal direction with a speed that is larger than that of all possible linear internal waves.

scholarly journals Nonlinear interaction between acoustic gravity waves

1996 ◽  
Vol 14 (3) ◽  
pp. 304-308 ◽  
Author(s):  
P. Axelsson ◽  
J. Larsson ◽  
L. Stenflo
Keyword(s):  
Gravity Waves ◽  
Nonlinear Interaction ◽  
Low Frequency ◽  
Resonant Interaction ◽  
Coupling Coefficients ◽  
Symmetric Form ◽  
Frequency Limit ◽  
Acoustic Gravity Waves

Abstract. The resonant interaction between three acoustic gravity waves is considered. We improve on the results of previous authors and write the new coupling coefficients in a symmetric form. Particular attention is paid to the low-frequency limit.

scholarly journals Time-Dependent Propagation of Tsunami-Generated Acoustic–Gravity Waves in the Atmosphere

2020 ◽  
Vol 77 (4) ◽  
pp. 1233-1244 ◽  
Author(s):  
Yue Wu ◽  
Stefan G. Llewellyn Smith ◽  
James W. Rottman ◽  
Dave Broutman ◽  
Jean-Bernard H. Minster
Keyword(s):  
Internal Waves ◽  
Gravity Waves ◽  
Acoustic Waves ◽  
Early Stage ◽  
Vertical Displacement ◽  
Inverse Laplace Transform ◽  
Acoustic Gravity Waves ◽  
Numerical Inverse Laplace Transform ◽  
Wave Development

Abstract Tsunami-generated linear acoustic–gravity waves in the atmosphere with altitude-dependent vertical stratification and horizontal background winds are studied with the long-term goal of real-time tsunami warning. The initial-value problem is examined using Fourier–Laplace transforms to investigate the time dependence and to compare the cases of anelastic and compressible atmospheres. The approach includes formulating the linear propagation of acoustic–gravity waves in the vertical, solving the vertical displacement of waves and pressure perturbations numerically as a set of coupled ODEs in the Fourier–Laplace domain, and employing den Iseger’s algorithm to carry out a fast and accurate numerical inverse Laplace transform. Results are presented for three cases with different atmospheric and tsunami profiles. Horizontal background winds enhance wave advection in the horizontal but hinder the vertical transmission of internal waves through the whole atmosphere. The effect of compressibility is significant. The rescaled vertical displacement of internal waves at 100-km altitude shows an arrival at the early stage of wave development due to the acoustic branch that is not present in the anelastic case. The long-term displacement also shows an O(1) difference between the compressible and anelastic results for the cases with uniform and realistic stratification. Compressibility hence affects both the speed and amplitude of energy transmitted to the upper atmosphere because of fast acoustic waves.

scholarly journals Electromagnetic oscillations of the Earth's upper atmosphere (review)

2010 ◽  
Vol 28 (7) ◽  
pp. 1387-1399 ◽  
Author(s):  
A. G. Khantadze ◽  
G. V. Jandieri ◽  
A. Ishimaru ◽  
T. D. Kaladze ◽  
Zh. M. Diasamidze
Keyword(s):  
Gravity Waves ◽  
Geomagnetic Field ◽  
Large Scale ◽  
Low Frequency ◽  
Planetary Waves ◽  
Upper Atmosphere ◽  
Acoustic Gravity Waves ◽  
Weakly Ionized ◽  
General Dispersion ◽  
Electromagnetic Oscillations

Abstract. A complete theory of low-frequency MHD oscillations of the Earth's weakly ionized ionosphere is formulated. Peculiarities of excitation and propagation of electromagnetic acoustic-gravity, MHD and planetary waves are considered in the Earth's ionosphere. The general dispersion equation is derived for the magneto-acoustic, magneto-gravity and electromagnetic planetary waves in the ionospheric E- and F-regions. The action of the geomagnetic field on the propagation of acoustic-gravity waves is elucidated. The nature of the existence of the comparatively new large-scale electromagnetic planetary branches is emphasized.

Transmission of acoustic-gravity waves through gas–liquid interfaces

2012 ◽  
Vol 709 ◽  
pp. 313-340 ◽  
Author(s):  
Oleg A. Godin ◽  
Iosif M. Fuks
Keyword(s):  
Gravity Waves ◽  
Acoustic Waves ◽  
Low Frequency ◽  
Paper Analysis ◽  
Liquid Interfaces ◽  
Power Flux ◽  
Acoustic Gravity Waves ◽  
Restoring Forces ◽  
Anomalous Transparency ◽  
Diffraction Effects

AbstractIt was demonstrated recently that gas–liquid interfaces, which are usually almost perfect reflectors of acoustic waves, become anomalously transparent, and the power flux in the wave transmitted into the gas increases dramatically, when a compact sound source in the liquid approaches the interface within a fraction of the wavelength (Godin, Phys. Rev. Lett., vol. 97, 2006b, 164301). Powerful underwater explosions and certain natural sources, such as underwater landslides, generate very low-frequency waves in water and air, for which fluid buoyancy and compressibility simultaneously serve as restoring forces. In this paper, analysis of sound transmission through gas–liquid interfaces is extended to acoustic-gravity waves (AGWs) and applied to the air–water interface. It is found that, as for sound, the interface becomes anomalously transparent for sufficiently shallow compact sources of AGWs. Depending on the source type, the increase of a wave power flux into gas due to diffraction effects can reach several orders of magnitude. The physical mechanisms responsible for the anomalous transparency are discussed. Excitation of an interface wave by a point source in the liquid is shown to be an important channel of AGW transmission into the gas, which has no counterpart in the case of sound.

scholarly journals Spectra of Acoustic-Gravity Waves in the Atmosphere with a Quasi-Isothermal Upper Layer

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 818
Author(s):  
Sergey P. Kshevetskii ◽  
Yuliya A. Kurdyaeva ◽  
Nikolai M. Gavrilov
Keyword(s):  
Gravity Waves ◽  
Evolution Operator ◽  
Mathematical Problem ◽  
Cutoff Frequency ◽  
Lower Boundary ◽  
Low Frequency ◽  
Acoustic Gravity Waves ◽  
Wide Range ◽  
Different Altitudes ◽  
Wave Modes

In this paper, we study, in theoretical terms, the structure of the spectrum of acoustic-gravity waves (AGWs) in the nonisothermal atmosphere having asymptotically constant temperature at high altitudes. A mathematical problem of wave propagation from arbitrary initial perturbations in the half-infinite nonisothermal atmosphere is formulated and analyzed for a system of linearized hydrodynamic equations for small-amplitude waves. Besides initial and lower boundary conditions at the ground, wave energy conservation requirements are applied. In this paper, we show that this mathematical problem belongs to the class of wave problems having self-adjoint evolution operators, which ensures the correctness and existence of solutions for a wide range of atmospheric temperature stratifications. A general solution of the problem can be built in the form of basic eigenfunction expansions of the evolution operator. The paper shows that wave frequencies considered as eigenvalues of the self-adjoint evolution operator are real and form two global branches corresponding to high- and low-frequency AGW modes. These two branches are separated since the Brunt–Vaisala frequency is smaller than the acoustic cutoff frequency at the upper boundary of the model. Wave modes belonging to the low-frequency global spectral branch have properties of internal gravity waves (IGWs) at all altitudes. Wave modes of the high-frequency spectral branch at different altitudes may have properties of IGWs or acoustic waves depending on local stratification. The results of simulations using a high-resolution nonlinear numerical model confirm possible changes of AGW properties at different altitudes in the nonisothermal atmosphere.

Acoustic-Gravity Waves in Whirling Polar Thermosphere

2015 ◽  
Vol 47 (9) ◽  
pp. 10-22 ◽  
Author(s):  
Yuriy P. Ladikov-Roev ◽  
Oleg K. Cheremnykh ◽  
Alla K. Fedorenko ◽  
Vladimir E. Nabivach
Keyword(s):  
Gravity Waves ◽  
Acoustic Gravity Waves
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