scholarly journals Wave over the source in a thermal-conductive atmosphere

2015 ◽  
Vol 1 (4) ◽  
pp. 11-29 ◽  
Author(s):  
Георгий Руденко ◽  
Georgiy Rudenko ◽  
Ирина Дмитриенко ◽  
Irina Dmitrienko
Keyword(s):  
Thermal Conductivity ◽  
Analytical Solution ◽  
Numerical Solution ◽  
Gravity Waves ◽  
Lower Atmosphere ◽  
The Real ◽  
Acoustic Gravity Waves ◽  
Wave Disturbances ◽  
Small Dissipation

For acoustic-gravity waves, we propose a method for obtaining solutions over the source, taking into account the thermal conductivity throughout the atmosphere. The solution is constructed by combining the analytical solution for the upper isothermal part and numerical solution for the real non-isothermal dissipative atmosphere. The possibility of different ways of describing the wave disturbances investigated for different altitudinal ranges. A special way of accounting for small dissipation of the lower atmosphere is proposed. The heights of strong dissipation are found.

AGW manifestations in the Earth neutral atmosphere and ionosphere

2021 ◽  
Author(s):  
Tatiana Syrenova ◽  
Alexander Beletsky
Keyword(s):  
Optical System ◽  
Deep Convection ◽  
Lower Atmosphere ◽  
Automatic Identification ◽  
Complex Data ◽  
Neutral Atmosphere ◽  
Data Set ◽  
Acoustic Gravity Waves ◽  
Wave Disturbances ◽  
System Data

<p>Acoustic gravity waves (AGW) manifestations spread from the lower atmosphere to the upper layers due to processes such as orography, weather fronts, deep convection atmosphere, and vice versa, can form in the upper atmosphere during geomagnetic activity, receiving energy from the magnetosphere. These wave processes can be considered as a dynamic process that transfers energy between different atmospheric and latitudinal regions, therefore it is important to understand their basic parameters and behavior.</p><p>In this work, to study wave disturbances, we used the Keo Sentinel optical system data, designed to record the spatial pattern of the 630 nm emission intensity (emission height 180-300 km). The system is located at the Geophysical Observatory (GPO) of the ISTP SB RAS, near the Tory, Buryatiya, Russia (52<sup>0</sup> N, 103<sup>0</sup> E, height 670 m). The  interference filter transmission half-width is ~ 2 nm. Sight direction - zenith, field of view 145 degrees, exposure time 30-60 s (http://atmos.iszf.irk.ru/ru/data/keo).</p><p>For the analysis, we chose data obtained on clear, moonless nights from 2014 to March 2019. The total number of nights selected for analysis was 71 (~ 491 hours). An algorithm for the wave events and their characteristics automatic identification from the optic data was developed and tested. The approbation was carried out on a data set previously processed manually [Syrenova, Beletsky, 2019]. A comparison was made with traveling ionospheric disturbances (TID) characteristics obtained from the ISTP SB RAS radio-physical complex data [Medvedev et al., 2012].</p><p>The main directions of wave disturbances propagation obtained with automatic optical system data processing - southward (~ 175º) and eastward (~ 90º) - are similar to the TID directions. From the radiophysical complex data, the TID distribution from North to South prevails, the most probable azimuth is ~ 135º during the day, and ~ 205º at night. The most probable values ​​of the wave disturbances propagation velocity obtained as a result of automatic processing are about 80 m/s. These values ​​also accept well with the TID values.</p><p>The main characteristics obtained using the data of the optical and radiophysical complexes agree with each other. Differences in the preferred propagation direction of the recorded wave structures from the KEO Sentinel data from the directions obtained with photometers at the same observation point [Tashchilin, 2010, Podlesny, 2018], probably, associated with different observation heights.</p>

scholarly journals On resonant triad interactions of acoustic–gravity waves

2015 ◽  
Vol 788 ◽  
Author(s):  
Usama Kadri ◽  
T. R. Akylas
Keyword(s):  
Gravity Waves ◽  
Evolution Equations ◽  
Phase Speed ◽  
Acoustic Mode ◽  
Coupling Mechanism ◽  
Acoustic Gravity Waves ◽  
Compression Waves ◽  
Interaction Terms ◽  
Wave Disturbances ◽  
Quadratic Interaction

The propagation of wave disturbances in water of uniform depth is discussed, accounting for both gravity and compressibility effects. In the linear theory, free-surface (gravity) waves are virtually decoupled from acoustic (compression) waves, because the speed of sound in water far exceeds the maximum phase speed of gravity waves. However, these two types of wave motion could exchange energy via resonant triad nonlinear interactions. This scenario is analysed for triads comprising a long-crested acoustic mode and two oppositely propagating subharmonic gravity waves. Owing to the disparity of the gravity and acoustic length scales, the interaction time scale is longer than that of a standard resonant triad, and the appropriate amplitude evolution equations, apart from the usual quadratic interaction terms, also involve certain cubic terms. Nevertheless, it is still possible for monochromatic wavetrains to form finely tuned triads, such that nearly all the energy initially in the gravity waves is transferred to the acoustic mode. This coupling mechanism, however, is far less effective for locally confined wavepackets.

scholarly journals On the propagation of acoustic–gravity waves under elastic ice sheets

2018 ◽  
Vol 837 ◽  
pp. 640-656 ◽  
Author(s):  
Ali Abdolali ◽  
Usama Kadri ◽  
Wade Parsons ◽  
James T. Kirby
Keyword(s):  
Gravity Waves ◽  
Cutoff Frequency ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Bottom Pressure ◽  
Acoustic Gravity Waves ◽  
Gravitational Forces ◽  
Wave Disturbances ◽  
Different Characteristics ◽  
Elasticity Effects

The propagation of wave disturbances in water of varying depth bounded above by ice sheets is discussed, accounting for gravity, compressibility and elasticity effects. Considering the more realistic scenario of elastic ice sheets reveals a continuous spectrum of acoustic–gravity modes that propagate even below the cutoff frequency of the rigid surface solution where surface (gravity) waves cannot exist. The balance between gravitational forces and oscillations in the ice sheet defines a new dimensionless quantity $\mathfrak{Ka}$. When the ice sheet is relatively thin and the prescribed frequency is relatively low ($\mathfrak{Ka}\ll 1$), the free-surface bottom-pressure solution is retrieved in full. However, thicker ice sheets or propagation of relatively higher frequency modes ($\mathfrak{Ka}\gg 1$) alter the solution fundamentally, which is reflected in an amplified asymmetric signature and different characteristics of the eigenvalues, such that the bottom pressure is amplified when acoustic–gravity waves are transmitted to shallower waters. To analyse these scenarios, an analytical solution and a depth-integrated equation are derived for the cases of constant and varying depths, respectively. Together, these are capable of modelling realistic ocean geometries and an inhomogeneous distribution of ice sheets.

Vertical Propagation of Acoustic Gravity Waves from the Lower Atmosphere during a Solar Eclipse

2020 ◽  
Vol 14 (2) ◽  
pp. 355-361
Author(s):  
Yu. A. Dyakov ◽  
Yu. A. Kurdyaeva ◽  
O. P. Borchevkina ◽  
I. V. Karpov ◽  
S. O. Adamson ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Solar Eclipse ◽  
Lower Atmosphere ◽  
Acoustic Gravity Waves ◽  
Vertical Propagation

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

scholarly journals Acoustic–gravity waves from multi-fault rupture

2021 ◽  
Vol 915 ◽  
Author(s):  
Byron Williams ◽  
Usama Kadri ◽  
Ali Abdolali
Keyword(s):  
Gravity Waves ◽  
Fault Rupture ◽  
Acoustic Gravity Waves

Abstract

scholarly journals A fractional order epidemic model for the simulation of outbreaks of Ebola

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Weiqiu Pan ◽  
Tianzeng Li ◽  
Safdar Ali
Keyword(s):  
Numerical Solution ◽  
Root Mean Square ◽  
Fractional Order ◽  
Relative Error ◽  
Numerical Solutions ◽  
Real Data ◽  
Mean Square ◽  
Order Model ◽  
The Real ◽  
Fractional Orders

AbstractThe Ebola outbreak in 2014 caused many infections and deaths. Some literature works have proposed some models to study Ebola virus, such as SIR, SIS, SEIR, etc. It is proved that the fractional order model can describe epidemic dynamics better than the integer order model. In this paper, we propose a fractional order Ebola system and analyze the nonnegative solution, the basic reproduction number $R_{0}$ R 0 , and the stabilities of equilibrium points for the system firstly. In many studies, the numerical solutions of some models cannot fit very well with the real data. Thus, to show the dynamics of the Ebola epidemic, the Gorenflo–Mainardi–Moretti–Paradisi scheme (GMMP) is taken to get the numerical solution of the SEIR fractional order Ebola system and the modified grid approximation method (MGAM) is used to acquire the parameters of the SEIR fractional order Ebola system. We consider that the GMMP method may lead to absurd numerical solutions, so its stability and convergence are given. Then, the new fractional orders, parameters, and the root-mean-square relative error $g(U^{*})=0.4146$ g ( U ∗ ) = 0.4146 are obtained. With the new fractional orders and parameters, the numerical solution of the SEIR fractional order Ebola system is closer to the real data than those models in other literature works. Meanwhile, we find that most of the fractional order Ebola systems have the same order. Hence, the fractional order Ebola system with different orders using the Caputo derivatives is also studied. We also adopt the MGAM algorithm to obtain the new orders, parameters, and the root-mean-square relative error which is $g(U^{*})=0.2744$ g ( U ∗ ) = 0.2744 . With the new parameters and orders, the fractional order Ebola systems with different orders fit very well with the real data.

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