Scattering of internal gravity waves

OpenAIRE

Leaman Nye, Abigail

2011-01-01

Internal gravity waves play a fundamental role in the dynamics of stably stratified regions of the atmosphere and ocean. In addition to the radiation of momentum and energy remote from generation sites, internal waves drive vertical transport of heat and mass through the ocean by wave breaking and the mixing subsequently produced. Identifying regions where internal gravity waves contribute to ocean mixing and quantifying this mixing are therefore important for accurate climate ...

The gravitational wave stress–energy (pseudo)-tensor in modified gravity

Science.gov (United States)

Saffer, Alexander; Yunes, Nicolás; Yagi, Kent

2018-03-01

The recent detections of gravitational waves by the advanced LIGO and Virgo detectors open up new tests of modified gravity theories in the strong-field and dynamical, extreme gravity regime. Such tests rely sensitively on the phase evolution of the gravitational waves, which is controlled by the energy–momentum carried by such waves out of the system. We here study four different methods for finding the gravitational wave stress–energy pseudo-tensor in gravity theories with any combination of scalar, vector, or tensor degrees of freedom. These methods rely on the second variation of the action under short-wavelength averaging, the second perturbation of the field equations in the short-wavelength approximation, the construction of an energy complex leading to a Landau–Lifshitz tensor, and the use of Noether’s theorem in field theories about a flat background. We apply these methods in general relativity, Jordan–Fierz–Brans–Dicky theoy, and Einstein-Æther theory to find the gravitational wave stress–energy pseudo-tensor and calculate the rate at which energy and linear momentum is carried away from the system. The stress–energy tensor and the rate of linear momentum loss in Einstein-Æther theory are presented here for the first time. We find that all methods yield the same rate of energy loss, although the stress–energy pseudo-tensor can be functionally different. We also find that the Noether method yields a stress–energy tensor that is not symmetric or gauge-invariant, and symmetrization via the Belinfante procedure does not fix these problems because this procedure relies on Lorentz invariance, which is spontaneously broken in Einstein-Æther theory. The methods and results found here will be useful for the calculation of predictions in modified gravity theories that can then be contrasted with observations.

GEODYNAMIC WAVES AND GRAVITY

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A. V. Vikulin

2014-01-01

Full Text Available  Gravity phenomena related to the Earth movements in the Solar System and through the Galaxy are reviewed. Such movements are manifested by geological processes on the Earth and correlate with geophysical fields of the Earth. It is concluded that geodynamic processes and the gravity phenomena (including those of cosmic nature are related.  The state of the geomedium composed of blocks is determined by stresses with force moment and by slow rotational waves that are considered as a new type of movements [Vikulin, 2008, 2010]. It is shown that the geomedium has typical rheid properties [Carey, 1954], specifically an ability to flow while being in the solid state [Leonov, 2008]. Within the framework of the rotational model with a symmetric stress tensor, which is developed by the authors [Vikulin, Ivanchin, 1998; Vikulin et al., 2012a, 2013], such movement of the geomedium may explain the energy-saturated state of the geomedium and a possibility of its movements in the form of vortex geological structures [Lee, 1928]. The article discusses the gravity wave detection method based on the concept of interactions between gravity waves and crustal blocks [Braginsky et al., 1985]. It is concluded that gravity waves can be recorded by the proposed technique that detects slow rotational waves. It is shown that geo-gravitational movements can be described by both the concept of potential with account of gravitational energy of bodies [Kondratyev, 2003] and the nonlinear physical acoustics [Gurbatov et al., 2008]. Based on the combined description of geophysical and gravitational wave movements, the authors suggest a hypothesis about the nature of spin, i.e. own moment as a demonstration of the space-time ‘vortex’ properties.  

Multipole analysis in the radiation field for linearized f (R ) gravity with irreducible Cartesian tensors

Science.gov (United States)

Wu, Bofeng; Huang, Chao-Guang

2018-04-01

The 1 /r expansion in the distance to the source is applied to the linearized f (R ) gravity, and its multipole expansion in the radiation field with irreducible Cartesian tensors is presented. Then, the energy, momentum, and angular momentum in the gravitational waves are provided for linearized f (R ) gravity. All of these results have two parts, which are associated with the tensor part and the scalar part in the multipole expansion of linearized f (R ) gravity, respectively. The former is the same as that in General Relativity, and the latter, as the correction to the result in General Relativity, is caused by the massive scalar degree of freedom and plays an important role in distinguishing General Relativity and f (R ) gravity.

The instability of internal gravity waves to localised disturbances

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J. Vanneste

1995-02-01

Full Text Available The instability of an internal gravity wave due to nonlinear wave-wave interaction is studied theoretically and numerically. Three different aspects of this phenomenon are examined. 1. The influence of dissipation on both the resonant and the nonresonant interactions is analysed using a normal mode expansion of the basic equations. In particular, the modifications induced in the interaction domain are calculated and as a result some modes are shown to be destabilised by dissipation. 2. The evolution of an initial unstable disturbance of finite vertical extent is described as the growth of two secondary wave packets travelling at the same group velocity. A quasi-linear correction to the basic primary wave is calculated, corresponding to a localised amplitude decrease due to the disturbance growth. 3. Numerical experiments are carried out to study the effect of a basic shear on wave instability. It appears that the growing secondary waves can have a frequency larger than that of the primary wave, provided that the shear is sufficient. The instability of waves with large amplitude and long period, such as tides or planetary waves, could therefore be invoked as a possible mechanism for the generation of gravity waves with shorter period in the middle atmosphere.

New Gravity Wave Treatments for GISS Climate Models

Science.gov (United States)

Geller, Marvin A.; Zhou, Tiehan; Ruedy, Reto; Aleinov, Igor; Nazarenko, Larissa; Tausnev, Nikolai L.; Sun, Shan; Kelley, Maxwell; Cheng, Ye

2011-01-01

Previous versions of GISS climate models have either used formulations of Rayleigh drag to represent unresolved gravity wave interactions with the model-resolved flow or have included a rather complicated treatment of unresolved gravity waves that, while being climate interactive, involved the specification of a relatively large number of parameters that were not well constrained by observations and also was computationally very expensive. Here, the authors introduce a relatively simple and computationally efficient specification of unresolved orographic and nonorographic gravity waves and their interaction with the resolved flow. Comparisons of the GISS model winds and temperatures with no gravity wave parameterization; with only orographic gravity wave parameterization; and with both orographic and nonorographic gravity wave parameterizations are shown to illustrate how the zonal mean winds and temperatures converge toward observations. The authors also show that the specifications of orographic and nonorographic gravity waves must be different in the Northern and Southern Hemispheres. Then results are presented where the nonorographic gravity wave sources are specified to represent sources from convection in the intertropical convergence zone and spontaneous emission from jet imbalances. Finally, a strategy to include these effects in a climate-dependent manner is suggested.

Transition from geostrophic turbulence to inertia–gravity waves in the atmospheric energy spectrum

Science.gov (United States)

Callies, Jörn; Ferrari, Raffaele; Bühler, Oliver

2014-01-01

Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth’s rotation and the atmosphere’s stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia–gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia–gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia–gravity waves dominate at scales smaller than 500 km. PMID:25404349

Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

Science.gov (United States)

Callies, Jörn; Ferrari, Raffaele; Bühler, Oliver

2014-12-02

Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth's rotation and the atmosphere's stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia-gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia-gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia-gravity waves dominate at scales smaller than 500 km.

Relic gravity waves from braneworld inflation

International Nuclear Information System (INIS)

Sahni, Varun; Sami, M.; Souradeep, Tarun

2002-01-01

We discuss a scenario in which extra dimensional effects allow a scalar field with a steep potential to play the dual role of the inflaton as well as dark energy (quintessence). The post-inflationary evolution of the universe in this scenario is generically characterized by a 'kinetic regime' during which the kinetic energy of the scalar field greatly exceeds its potential energy resulting in a 'stiff' equation of state for scalar field matter P φ ≅ρ φ . The kinetic regime precedes the radiation dominated epoch and introduces an important new feature into the spectrum of relic gravity waves created quantum mechanically during inflation. The amplitude of the gravity wave spectrum increases with the wave number for wavelengths shorter than the comoving horizon scale at the commencement of the radiative regime. This 'blue tilt' is a generic feature of models with steep potentials and imposes strong constraints on a class of inflationary braneworld models. Prospects for detection of the gravity wave background by terrestrial and space-borne gravity wave observatories such as LIGO II and LISA are discussed

Relic gravitational wave spectrum, the trans-Planckian physics and Horava-Lifshitz gravity

International Nuclear Information System (INIS)

Koh, Seoktae

2010-01-01

We calculate the spectrum of the relic gravitational wave due to the trans-Planckian effect in which the standard linear dispersion relations may be modified. Of the modified dispersion relations suggested in the literature which has investigated the trans-Planckian effect, we especially use the Corley-Jacobson dispersion relations. The Corley-Jacobson-type modified dispersion relations can be obtained from Horava-Lifshitz gravity which is non-relativistic and UV complete. Although it is not clear how the transitions from Horava-Lifshitz gravity in the UV regime to Einstein gravity in the IR limit occur, we assume that the Horava-Lifshitz gravity regime is followed by the inflationary phase in Einstein gravity.

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

Science.gov (United States)

Meyer, Catrin I.; Ern, Manfred; Hoffmann, Lars; Trinh, Quang Thai; Alexander, M. Joan

2018-01-01

We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are compared on a

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

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C. I. Meyer

2018-01-01

Full Text Available We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are

Investigating gravity waves evidences in the Venus upper atmosphere

Science.gov (United States)

Migliorini, Alessandra; Altieri, Francesca; Shakun, Alexey; Zasova, Ludmila; Piccioni, Giuseppe; Bellucci, Giancarlo; Grassi, Davide

2014-05-01

We present a method to investigate gravity waves properties in the upper mesosphere of Venus, through the O2 nightglow observations acquired with the imaging spectrometer VIRTIS on board Venus Express. Gravity waves are important dynamical features that transport energy and momentum. They are related to the buoyancy force, which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Gravity waves can manifest through fluctuations on temperature and density fields, and hence on airglow intensities. We use the O2 nightglow profiles showing double peaked structures to study the influence of gravity waves in shaping the O2 vertical profiles and infer the waves properties. In analogy to the Earth's and Mars cases, we use a well-known theory to model the O2 nightglow emissions affected by gravity waves propagation. Here we propose a statistical discussion of the gravity waves characteristics, namely vertical wavelength and wave amplitude, with respect to local time and latitude. The method is applied to about 30 profiles showing double peaked structures, and acquired with the VIRTIS/Venus Express spectrometer, during the mission period from 2006-07-05 to 2008-08-15.

Electromagnetic internal gravity waves in the Earth's ionospheric E-layer

International Nuclear Information System (INIS)

Kaladze, T.D.; Tsamalashvili, L.V.; Kaladze, D.T.

2011-01-01

In the Earth's ionospheric E-layer existence of the new waves connecting with the electromagnetic nature of internal gravity waves is shown. They represent the mixture of the ordinary internal gravity waves and the new type of dispersive Alfven waves. -- Highlights: ► Existence of electromagnetic internal gravity waves in the ionospheric E-layer is shown. ► Electromagnetic nature of internal gravity waves is described. ► Appearance of the new dispersive Alfven waves is shown.

The sources of atmospheric gravity waves

International Nuclear Information System (INIS)

Nagpal, O.P.

1979-01-01

The gravity wave theory has been very successful in the interpretation of various upper atmospheric phenomena. This article offers a review of the present state of knowledge about the various sources of atmospheric gravity waves, particularly those which give rise to different types of travelling ionospheric disturbance. Some specific case studies are discussed. (author)

Gravity waves from tachyonic preheating after hybrid inflation

Energy Technology Data Exchange (ETDEWEB)

Dufaux, Jean-Francois [Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Felder, Gary [Department of Physics, Clark Science Center, Smith College, Northampton, MA 01063 (United States); Kofman, Lev [CITA, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Navros, Olga, E-mail: jeff.dufaux@uam.es, E-mail: gfelder@email.smith.edu, E-mail: kofman@cita.utoronto.ca, E-mail: navros@email.unc.edu [Department of Mathematics, University of North Carolina Chapel Hill, CB3250 Philips Hall, Chapel Hill, NC 27599 (United States)

2009-03-15

We study the stochastic background of gravitational waves produced from preheating in hybrid inflation models. We investigate different dynamical regimes of preheating in these models and we compute the resulting gravity wave spectra using analytical estimates and numerical simulations. We discuss the dependence of the gravity wave frequencies and amplitudes on the various potential parameters. We find that large regions of the parameter space leads to gravity waves that may be observable in upcoming interferometric experiments, including Advanced LIGO, but this generally requires very small coupling constants.

Seeding and layering of equatorial spread F by gravity waves

International Nuclear Information System (INIS)

Hysell, D.L.; Kelley, M.C.; Swartz, W.E.; Woodman, R.F.

1990-01-01

Studies dating back more than 15 years have presented evidence that atmospheric gravity waves play a role in initiating nighttime equatorial F region instabilities. This paper analyzes a spectabular spread F event that for the first time demonstrates a layering which, the authors argue, is controlled by a gravity wave effect. The 50-km vertical wavelength of a gravity wave which they have found is related theoretically to a plasma layering irregularity that originated at low altitudes and then was convected, intact, to higher altitudes. Gravity waves also seem to have determined bottomside intermediate scale undulations, although this fact is not as clear in the data. The neutral wind dynamo effect yields wave number conditions on the gravity wave's ability to modulate the Rayleigh-Taylor instaiblity process. Finally, after evaluating the gravity wave dispersion relation and spatial resonance conditions, we estimate the properties of the seeding wave

Gravity wave vertical energy flux at 95 km

Science.gov (United States)

Jacob, P. G.; Jacka, F.

1985-01-01

A three-field photometer (3FP) located at Mt. Torrens near Adelaide, is capable of monitoring different airglow emissions from three spaced fields in the sky. A wheel containing up to six different narrow bandpass interference filters can be rotated, allowing each of the filters to be sequentially placed into each of the three fields. The airglow emission of interest is the 557.7 nm line which has an intensity maximum at 95 km. Each circular field of view is located at the apexes of an equilateral triangle centered on zenith with diameters of 5 km and field separations of 13 km when projected to the 95-km level. The sampling period was 30 seconds and typical data lengths were between 7 and 8 hours. The analysis and results from the interaction of gravity waves on the 557.7 nm emission layer are derived using an atmospheric model similar to that proposed by Hines (1960) where the atmosphere is assumed isothermal and perturbations caused by gravity waves are small and adiabatic, therefore, resulting in linearized equations of motion. In the absence of waves, the atmosphere is also considered stationary. Thirteen nights of quality data from January 1983 to October 1984, covering all seasons, are used in this analysis.

Tidal and gravity waves study from the airglow measurements at ...

Indian Academy of Sciences (India)

The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application ...

Gravitational Wave in Linear General Relativity

Science.gov (United States)

Cubillos, D. J.

2017-07-01

General relativity is the best theory currently available to describe the interaction due to gravity. Within Albert Einstein's field equations this interaction is described by means of the spatiotemporal curvature generated by the matter-energy content in the universe. Weyl worked on the existence of perturbations of the curvature of space-time that propagate at the speed of light, which are known as Gravitational Waves, obtained to a first approximation through the linearization of the field equations of Einstein. Weyl's solution consists of taking the field equations in a vacuum and disturbing the metric, using the Minkowski metric slightly perturbed by a factor ɛ greater than zero but much smaller than one. If the feedback effect of the field is neglected, it can be considered as a weak field solution. After introducing the disturbed metric and ignoring ɛ terms of order greater than one, we can find the linearized field equations in terms of the perturbation, which can then be expressed in terms of the Dalambertian operator of the perturbation equalized to zero. This is analogous to the linear wave equation in classical mechanics, which can be interpreted by saying that gravitational effects propagate as waves at the speed of light. In addition to this, by studying the motion of a particle affected by this perturbation through the geodesic equation can show the transversal character of the gravitational wave and its two possible states of polarization. It can be shown that the energy carried by the wave is of the order of 1/c5 where c is the speed of light, which explains that its effects on matter are very small and very difficult to detect.

A case study of gravity waves in noctilucent clouds

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P. Dalin

2004-06-01

Full Text Available We present a case study of a noctilucent cloud (NLC display appearing on 10-11 August 2000 over Northern Sweden. Clear wave structures were visible in the clouds and time-lapse photography was used to derive the parameters characterising the gravity waves which could account for the observed NLC modulation. Using two nearby atmospheric radars, the Esrange MST Radar data and Andoya MF radar, we have identified gravity waves propagating upward from the upper stratosphere to NLC altitudes. The wave parameters derived from the radar measurements support the suggestion that gravity waves are responsible for the observed complex wave dynamics in the NLC.

Stratospheric gravity wave activities inferred through the GPS radio occultation technique

International Nuclear Information System (INIS)

Wrasse, Cristiano Max; Takahashi, Hisao; Fechine, Joaquim; Denardini, Clezio Marcos; Wickert, Jens

2007-01-01

Stratospheric gravity wave activities were deduced from GPS radio occultation temperature profiles obtained by CHAMP satellite between 2001 and 2005. Potential energy profiles are used to analyze the gravity wave activity over South America. The results showed an inter-annual variation of the potential energy integrated between 24 and 34 km of altitude. The gravity wave activity is more concentrated around the equatorial region. In order to evaluate the seasonal variation of the gravity wave activity, a mean potential energy was determined over (10 deg N-10 deg S) and (100 deg W-20 deg W). The results showed a lower gravity wave activity during winter time, while during spring time the mean potential energy showed an increase in the wave activity. The results of the mean potential energy also showed that the gravity wave activity in the lower stratosphere exhibits a higher wave activity during 2002 and 2004 and a lower wave activity during 2003 and 2005. (author)

Dynamical structure of linearized GL(4) gravities

International Nuclear Information System (INIS)

Aragone, C.; Restuccia, A.

1978-01-01

The physical content of the three more natural models of GL(4) gravity is analyzed, for the case of weak fields. It is shown that the first model is the linearized version of Yang's one-tensor-field gravity and is a scalar-tensor theory, with its scalar part contained in a symmetric tensor. The second and the third linearized models, which can both be derived from the fourth-order action postulated by Yang, are two-tensor decoupled systems. In both cases one of the tensors is the symmetric weak metric gravity tensor field. the second tensor appearing in these two models, representing the GL(4)-gauge field, is either a linearized symmetric affinity (in the second model) or a linearized but nonsymmetric affinity (for the third model). It is shown that in these last two cases the affinity contains a helicity-3 propagating field. Owing to the presence of helicity-3 fields it is shown that it is better to regard Yang's action as an action for a two-tensor system instead of trying to recover from a pure gravity (one-tensor-field) action. Finally, it is shown what is the dynamical structure of the second and third linearized two-tensor models which can be derived from Yang's action. (author)

Experimental Observation of Negative Effective Gravity in Water Waves

Science.gov (United States)

Hu, Xinhua; Yang, Jiong; Zi, Jian; Chan, C. T.; Ho, Kai-Ming

2013-01-01

The gravity of Earth is responsible for the formation of water waves and usually difficult to change. Although negative effective gravity was recently predicted theoretically in water waves, it has not yet been observed in experiments and remains a mathematical curiosity which is difficult to understand. Here we experimentally demonstrate that close to the resonant frequency of purposely-designed resonating units, negative effective gravity can occur for water waves passing through an array of resonators composing of bottom-mounted split tubes, resulting in the prohibition of water wave propagation. It is found that when negative gravity occurs, the averaged displacement of water surface in a unit cell of the array has a phase difference of π to that along the boundary of the unit cell, consistent with theoretical predictions. Our results provide a mechanism to block water waves and may find applications in wave energy conversion and coastal protection. PMID:23715132

Gravity wave influence on NLC: experimental results from ALOMAR, 69° N

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H. Wilms

2013-12-01

Full Text Available The influence of gravity waves on noctilucent clouds (NLC at ALOMAR (69° N is analysed by relating gravity wave activity to NLC occurrence from common-volume measurements. Gravity wave kinetic energies are derived from MF-radar wind data and filtered into different period ranges by wavelet transformation. From the dataset covering the years 1999–2011, a direct correlation between gravity wave kinetic energy and NLC occurrence is not found, i.e., NLC appear independently of the simultaneously measured gravity wave kinetic energy. In addition, gravity wave activity is divided into weak and strong activity as compared to a 13 yr mean. The NLC occurrence rates during strong and weak activity are calculated separately for a given wave period and compared to each other. Again, for the full dataset no dependence of NLC occurrence on relative gravity wave activity is found. However, concentrating on 12 h of NLC detections during 2008, we do find an NLC-amplification with strong long-period gravity wave occurrence. Our analysis hence confirms previous findings that in general NLC at ALOMAR are not predominantly driven by gravity waves while exceptions to this rule are at least possible.

Intercomparison of stratospheric gravity wave observations with AIRS and IASI

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L. Hoffmann

2014-12-01

Full Text Available Gravity waves are an important driver for the atmospheric circulation and have substantial impact on weather and climate. Satellite instruments offer excellent opportunities to study gravity waves on a global scale. This study focuses on observations from the Atmospheric Infrared Sounder (AIRS onboard the National Aeronautics and Space Administration Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI onboard the European MetOp satellites. The main aim of this study is an intercomparison of stratospheric gravity wave observations of both instruments. In particular, we analyzed AIRS and IASI 4.3 μm brightness temperature measurements, which directly relate to stratospheric temperature. Three case studies showed that AIRS and IASI provide a clear and consistent picture of the temporal development of individual gravity wave events. Statistical comparisons based on a 5-year period of measurements (2008–2012 showed similar spatial and temporal patterns of gravity wave activity. However, the statistical comparisons also revealed systematic differences of variances between AIRS and IASI that we attribute to the different spatial measurement characteristics of both instruments. We also found differences between day- and nighttime data that are partly due to the local time variations of the gravity wave sources. While AIRS has been used successfully in many previous gravity wave studies, IASI data are applied here for the first time for that purpose. Our study shows that gravity wave observations from different hyperspectral infrared sounders such as AIRS and IASI can be directly related to each other, if instrument-specific characteristics such as different noise levels and spatial resolution and sampling are carefully considered. The ability to combine observations from different satellites provides an opportunity to create a long-term record, which is an exciting prospect for future climatological studies of stratospheric

Laser Source for Atomic Gravity Wave Detector

Data.gov (United States)

National Aeronautics and Space Administration — The Atom Interferometry (AI) Technology for Gravity Wave Measurements demonstrates new matter wave Interferometric sensor technology for precise detection and...

Propagation and Breaking at High Altitudes of Gravity Waves Excited by Tropospheric Forcing

Science.gov (United States)

Prusa, Joseph M.; Smolarkiewicz, Piotr K.; Garcia, Rolando R.

1996-01-01

An anelastic approximation is used with a time-variable coordinate transformation to formulate a two-dimensional numerical model that describes the evolution of gravity waves. The model is solved using a semi-Lagrangian method with monotone (nonoscillatory) interpolation of all advected fields. The time-variable transformation is used to generate disturbances at the lower boundary that approximate the effect of a traveling line of thunderstorms (a squall line) or of flow over a broad topographic obstacle. The vertical propagation and breaking of the gravity wave field (under conditions typical of summer solstice) is illustrated for each of these cases. It is shown that the wave field at high altitudes is dominated by a single horizontal wavelength; which is not always related simply to the horizontal dimension of the source. The morphology of wave breaking depends on the horizontal wavelength; for sufficiently short waves, breaking involves roughly one half of the wavelength. In common with other studies, it is found that the breaking waves undergo "self-acceleration," such that the zonal-mean intrinsic frequency remains approximately constant in spite of large changes in the background wind. It is also shown that many of the features obtained in the calculations can be understood in terms of linear wave theory. In particular, linear theory provides insights into the wavelength of the waves that break at high altitudes, the onset and evolution of breaking. the horizontal extent of the breaking region and its position relative to the forcing, and the minimum and maximum altitudes where breaking occurs. Wave breaking ceases at the altitude where the background dissipation rate (which in our model is a proxy for molecular diffusion) becomes greater than the rate of dissipation due to wave breaking, This altitude, in effect, the model turbopause, is shown to depend on a relatively small number of parameters that characterize the waves and the background state.

Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves

Science.gov (United States)

Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

2010-01-01

As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.

On the unstable mode merging of gravity-inertial waves with Rossby waves

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J. F. McKenzie

2011-08-01

Full Text Available We recapitulate the results of the combined theory of gravity-inertial-Rossby waves in a rotating, stratified atmosphere. The system is shown to exhibit a "local" (JWKB instability whenever the phase speed of the low-frequency-long wavelength westward propagating Rossby wave exceeds the phase speed ("Kelvin" speed of the high frequency-short wavelength gravity-inertial wave. This condition ensures that mode merging, leading to instability, takes place in some intermediate band of frequencies and wave numbers. The contention that such an instability is "spurious" is not convincing. The energy source of the instability resides in the background enthalpy which can be released by the action of the gravitational buoyancy force, through the combined wave modes.

Gravity waves from quantum stress tensor fluctuations in inflation

International Nuclear Information System (INIS)

Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

2011-01-01

We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

Gravity waves from quantum stress tensor fluctuations in inflation

Science.gov (United States)

Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

2011-11-01

We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

Seasonal variation and sources of atmospheric gravity waves in the Antarctic

Directory of Open Access Journals (Sweden)

Kaoru Sato

2010-12-01

Full Text Available In the last recent ten years, our knowledge of gravity waves in the Antarctic has been significantly improved through numerous studies using balloon and satellite observations and high-resolution model simulations. In this report, we introduce results from two studies which were performed as a part of the NIPR project "Integrated analysis of the material circulation in the Antarctic atmosphere-cryosphere-ocean" (2004-2009, i.e., Yoshiki et al. (2004 and Sato and Yoshiki (2008. These two studies focused on the seasonal variation and sources of the gravity waves in the Antarctic, because horizontal wavelengths and phase velocities depend largely on the wave sources. The former study used original high-resolution data from operational radiosonde observations at Syowa Station. In the lowermost stratosphere, gravity waves do not exhibit characteristic seasonal variation; instead, the wave energy is intensified when lower latitude air intrudes into the area near Syowa Station in the upper troposphere. This intrusion is associated with blocking events or developed synoptic-scale waves. In the lower and middle stratosphere, the gravity wave energy is maximized in spring and particularly intensified when the axis of the polar night jet approaches Syowa Station. The latter study is based on intensive radiosonde observation campaigns that were performed in 2002 at Syowa Station as an activity of JARE-43. Gravity wave propagation was statistically examined using two dimensional (i.e., vertical wavenumber versus frequency spectra in each season. It was shown that the gravity waves are radiated upward and downward from an unbalanced region of the polar night jet. This feature is consistent with the gravity-wave resolving GCM simulation.

Numerical simulations of convectively excited gravity waves

International Nuclear Information System (INIS)

Glatzmaier, G.A.

1983-01-01

Magneto-convection and gravity waves are numerically simulated with a nonlinear, three-dimensional, time-dependent model of a stratified, rotating, spherical fluid shell heated from below. A Solar-like reference state is specified while global velocity, magnetic field, and thermodynamic perturbations are computed from the anelastic magnetohydrodynamic equations. Convective overshooting from the upper (superadiabatic) part of the shell excites gravity waves in the lower (subadiabatic) part. Due to differential rotation and Coriolis forces, convective cell patterns propagate eastward with a latitudinally dependent phase velocity. The structure of the excited wave motions in the stable region is more time-dependent than that of the convective motions above. The magnetic field tends to be concentrated over giant-cell downdrafts in the convective zone but is affected very little by the wave motion in the stable region

Simulation of non-hydrostatic gravity wave propagation in the upper atmosphere

Directory of Open Access Journals (Sweden)

Y. Deng

2014-04-01

Full Text Available The high-frequency and small horizontal scale gravity waves may be reflected and ducted in non-hydrostatic simulations, but usually propagate vertically in hydrostatic models. To examine gravity wave propagation, a preliminary study has been conducted with a global ionosphere–thermosphere model (GITM, which is a non-hydrostatic general circulation model for the upper atmosphere. GITM has been run regionally with a horizontal resolution of 0.2° long × 0.2° lat to resolve the gravity wave with wavelength of 250 km. A cosine wave oscillation with amplitude of 30 m s−1 has been applied to the zonal wind at the low boundary, and both high-frequency and low-frequency waves have been tested. In the high-frequency case, the gravity wave stays below 200 km, which indicates that the wave is reflected or ducted in propagation. The results are consistent with the theoretical analysis from the dispersion relationship when the wavelength is larger than the cutoff wavelength for the non-hydrostatic situation. However, the low-frequency wave propagates to the high altitudes during the whole simulation period, and the amplitude increases with height. This study shows that the non-hydrostatic model successfully reproduces the high-frequency gravity wave dissipation.

An evaluation of gravity waves and gravity wave sources in the Southern Hemisphere in a 7 km global climate simulation.

Science.gov (United States)

Holt, L A; Alexander, M J; Coy, L; Liu, C; Molod, A; Putman, W; Pawson, S

2017-07-01

In this study, gravity waves (GWs) in the high-resolution GEOS-5 Nature Run are first evaluated with respect to satellite and other model results. Southern Hemisphere winter sources of non-orographic GWs in the model are then investigated by linking measures of tropospheric non-orographic gravity wave generation tied to precipitation and frontogenesis with absolute gravity wave momentum flux in the lower stratosphere. Finally, non-orographic GW momentum flux is compared to orographic gravity wave momentum flux and compared to previous estimates. The results show that the global patterns in GW amplitude, horizontal wavelength, and propagation direction are realistic compared to observations. However, as in other global models, the amplitudes are weaker and horizontal wavelengths longer than observed. The global patterns in absolute GW momentum flux also agree well with previous model and observational estimates. The evaluation of model non-orographic GW sources in the Southern Hemisphere winter shows that strong intermittent precipitation (greater than 10 mm h -1 ) is associated with GW momentum flux over the South Pacific, whereas frontogenesis and less intermittent, lower precipitation rates (less than 10 mm h -1 ) are associated with GW momentum flux near 60°S. In the model, orographic GWs contribute almost exclusively to a peak in zonal mean momentum flux between 70 and 75°S, while non-orographic waves dominate at 60°S, and non-orographic GWs contribute a third to a peak in zonal mean momentum flux between 25 and 30°S.

A coupling modulation model of capillary waves from gravity waves: Theoretical analysis and experimental validation

Science.gov (United States)

Chen, Pengzhen; Wang, Xiaoqing; Liu, Li; Chong, Jinsong

2016-06-01

According to Bragg theory, capillary waves are the predominant scatterers of high-frequency band (such as Ka-band) microwave radiation from the surface of the ocean. Therefore, understanding the modulation mechanism of capillary waves is an important foundation for interpreting high-frequency microwave remote sensing images of the surface of the sea. In our experiments, we discovered that modulations of capillary waves are significantly larger than the values predicted by the classical theory. Further, analysis shows that the difference in restoring force results in an inflection point while the phase velocity changes from gravity waves region to capillary waves region, and this results in the capillary waves being able to resonate with gravity waves when the phase velocity of the gravity waves is equal to the group velocity of the capillary waves. Consequently, we propose a coupling modulation model in which the current modulates the capillary wave indirectly by modulating the resonant gravity waves, and the modulation of the former is approximated by that of the latter. This model very effectively explains the results discovered in our experiments. Further, based on Bragg scattering theory and this coupling modulation model, we simulate the modulation of normalized radar cross section (NRCS) of typical internal waves and show that the high-frequency bands are superior to the low-frequency bands because of their greater modulation of NRCS and better radiometric resolution. This result provides new support for choice of radar band for observation of wave-current modulation oceanic phenomena such as internal waves, fronts, and shears.

Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations

Directory of Open Access Journals (Sweden)

S. Suzuki

2009-04-01

Full Text Available We present the characteristics of small-scale (<100 km gravity waves in the equatorial mesopause region derived from OH airglow imaging observations at Kototabang (100.3° E, 0.2° S, Indonesia, from 2002 to 2005. We adopted a method that could automatically detect gravity waves in the airglow images using two-dimensional cross power spectra of gravity waves. The propagation directions of the waves were likely controlled by zonal filtering due to stratospheric mean winds that show a quasi-biennial oscillation (QBO and the presence of many wave sources in the troposphere.

Laser Source for Atomic Gravity Wave Detector Project

Data.gov (United States)

National Aeronautics and Space Administration — The Atom Interferometry (AI) Technology for Gravity Wave Measurements demonstrates new matter wave Interferometric sensor technology for precise detection and...

Sensitivity of Gravity Wave Fluxes to Interannual Variations in Tropical Convection and Zonal Wind.

Science.gov (United States)

Alexander, M Joan; Ortland, David A; Grimsdell, Alison W; Kim, Ji-Eun

2017-09-01

Using an idealized model framework with high-frequency tropical latent heating variability derived from global satellite observations of precipitation and clouds, the authors examine the properties and effects of gravity waves in the lower stratosphere, contrasting conditions in an El Niño year and a La Niña year. The model generates a broad spectrum of tropical waves including planetary-scale waves through mesoscale gravity waves. The authors compare modeled monthly mean regional variations in wind and temperature with reanalyses and validate the modeled gravity waves using satellite- and balloon-based estimates of gravity wave momentum flux. Some interesting changes in the gravity spectrum of momentum flux are found in the model, which are discussed in terms of the interannual variations in clouds, precipitation, and large-scale winds. While regional variations in clouds, precipitation, and winds are dramatic, the mean gravity wave zonal momentum fluxes entering the stratosphere differ by only 11%. The modeled intermittency in gravity wave momentum flux is shown to be very realistic compared to observations, and the largest-amplitude waves are related to significant gravity wave drag forces in the lowermost stratosphere. This strong intermittency is generally absent or weak in climate models because of deficiencies in parameterizations of gravity wave intermittency. These results suggest a way forward to improve model representations of the lowermost stratospheric quasi-biennial oscillation winds and teleconnections.

No further gravitational wave modes in F(T) gravity

Energy Technology Data Exchange (ETDEWEB)

Bamba, Kazuharu, E-mail: bamba@kmi.nagoya-u.ac.jp [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Capozziello, Salvatore, E-mail: capozziello@na.infn.it [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Dipartimento di Fisica, Università di Napoli “Federico II” (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli (Italy); De Laurentis, Mariafelicia, E-mail: felicia@na.infn.it [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Dipartimento di Fisica, Università di Napoli “Federico II” (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli (Italy); Nojiri, Shin' ichi, E-mail: nojiri@phys.nagoya-u.ac.jp [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Sáez-Gómez, Diego, E-mail: diego.saezgomez@uct.ac.za [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Astrophysics, Cosmology and Gravity Centre (ACGC) and Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa); Fisika Teorikoaren eta Zientziaren Historia Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, 644 Posta Kutxatila, 48080 Bilbao (Spain)

2013-11-25

We explore the possibility of further gravitational wave modes in F(T) gravity, where T is the torsion scalar in teleparallelism. It is explicitly demonstrated that gravitational wave modes in F(T) gravity are equivalent to those in General Relativity. This result is achieved by calculating the Minkowskian limit for a class of analytic function of F(T). This consequence is also confirmed by the preservative analysis around the flat background in the weak field limit with the scalar–tensor representation of F(T) gravity.

No further gravitational wave modes in F(T) gravity

International Nuclear Information System (INIS)

Bamba, Kazuharu; Capozziello, Salvatore; De Laurentis, Mariafelicia; Nojiri, Shin'ichi; Sáez-Gómez, Diego

2013-01-01

We explore the possibility of further gravitational wave modes in F(T) gravity, where T is the torsion scalar in teleparallelism. It is explicitly demonstrated that gravitational wave modes in F(T) gravity are equivalent to those in General Relativity. This result is achieved by calculating the Minkowskian limit for a class of analytic function of F(T). This consequence is also confirmed by the preservative analysis around the flat background in the weak field limit with the scalar–tensor representation of F(T) gravity

Smoothed-particle-hydrodynamics modeling of dissipation mechanisms in gravity waves.

Science.gov (United States)

Colagrossi, Andrea; Souto-Iglesias, Antonio; Antuono, Matteo; Marrone, Salvatore

2013-02-01

The smoothed-particle-hydrodynamics (SPH) method has been used to study the evolution of free-surface Newtonian viscous flows specifically focusing on dissipation mechanisms in gravity waves. The numerical results have been compared with an analytical solution of the linearized Navier-Stokes equations for Reynolds numbers in the range 50-5000. We found that a correct choice of the number of neighboring particles is of fundamental importance in order to obtain convergence towards the analytical solution. This number has to increase with higher Reynolds numbers in order to prevent the onset of spurious vorticity inside the bulk of the fluid, leading to an unphysical overdamping of the wave amplitude. This generation of spurious vorticity strongly depends on the specific kernel function used in the SPH model.

Linear and non-linear Modified Gravity forecasts with future surveys

Science.gov (United States)

Casas, Santiago; Kunz, Martin; Martinelli, Matteo; Pettorino, Valeria

2017-12-01

Modified Gravity theories generally affect the Poisson equation and the gravitational slip in an observable way, that can be parameterized by two generic functions (η and μ) of time and space. We bin their time dependence in redshift and present forecasts on each bin for future surveys like Euclid. We consider both Galaxy Clustering and Weak Lensing surveys, showing the impact of the non-linear regime, with two different semi-analytical approximations. In addition to these future observables, we use a prior covariance matrix derived from the Planck observations of the Cosmic Microwave Background. In this work we neglect the information from the cross correlation of these observables, and treat them as independent. Our results show that η and μ in different redshift bins are significantly correlated, but including non-linear scales reduces or even eliminates the correlation, breaking the degeneracy between Modified Gravity parameters and the overall amplitude of the matter power spectrum. We further apply a Zero-phase Component Analysis and identify which combinations of the Modified Gravity parameter amplitudes, in different redshift bins, are best constrained by future surveys. We extend the analysis to two particular parameterizations of μ and η and consider, in addition to Euclid, also SKA1, SKA2, DESI: we find in this case that future surveys will be able to constrain the current values of η and μ at the 2-5% level when using only linear scales (wavevector k < 0 . 15 h/Mpc), depending on the specific time parameterization; sensitivity improves to about 1% when non-linearities are included.

VHF radar observations of gravity waves at a low latitude

Directory of Open Access Journals (Sweden)

G. Dutta

1999-08-01

Full Text Available Wind observations made at Gadanki (13.5°N by using Indian MST Radar for few days in September, October, December 1995 and January, 1996 have been analyzed to study gravity wave activity in the troposphere and lower stratosphere. Horizontal wind variances have been computed for gravity waves of period (2-6 h from the power spectral density (PSD spectrum. Exponential curves of the form eZ/H have been fitted by least squares technique to these variance values to obtain height variations of the irregular winds upto the height of about 15 km, where Z is the height in kilometers. The value of H, the scale height, as determined from curve fitting is found to be less than the theoretical value of scale height of neutral atmosphere in this region, implying that the waves are gaining energy during their passage in the troposphere. In other words, it indicates that the sources of gravity waves are present in the troposphere. The energy densities of gravity wave fluctuations have been computed. Polynomial fits to the observed values show that wave energy density increases in the troposphere, its source region, and then decreases in the lower stratosphere.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides

Effects of Rotation and Gravity Field on Surface Waves in Fibre-Reinforced Thermoelastic Media under Four Theories

Directory of Open Access Journals (Sweden)

A. M. Abd-Alla

2013-01-01

Full Text Available Estimation is done to investigate the gravitational and rotational parameters effects on surface waves in fibre-reinforced thermoelastic media. The theory of generalized surface waves has been firstly developed and then it has been employed to investigate particular cases of waves, namely, Stoneley waves, Rayleigh waves, and Love waves. The analytical expressions for surface waves velocity and attenuation coefficient are obtained in the physical domain by using the harmonic vibrations and four thermoelastic theories. The wave velocity equations have been obtained in different cases. The numerical results are given for equation of coupled thermoelastic theory (C-T, Lord-Shulman theory (L-S, Green-Lindsay theory (G-L, and the linearized (G-N theory of type II. Comparison was made with the results obtained in the presence and absence of gravity, rotation, and parameters for fibre-reinforced of the material media. The results obtained are displayed by graphs to clear the phenomena physical meaning. The results indicate that the effect of gravity, rotation, relaxation times, and parameters of fibre-reinforced of the material medium is very pronounced.

A global climatology of stratospheric gravity waves from Atmospheric Infrared Sounder observations

Science.gov (United States)

Hoffmann, Lars; Xue, Xianghui; Alexander, M. Joan

2014-05-01

We present the results of a new study that aims on the detection and classification of `hotspots' of stratospheric gravity waves on a global scale. The analysis is based on a nine-year record (2003 to 2011) of radiance measurements by the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. We detect the presence of stratospheric gravity waves based on 4.3 micron brightness temperature variances. Our method is optimized for peak events, i.e., strong gravity wave events for which the local variance considerably exceeds background levels. We estimated the occurrence frequencies of these peak events for different seasons and time of day and used the results to find local maxima of gravity wave activity. In addition, we use AIRS radiances at 8.1 micron to simultaneously detect convective events, including deep convection in the tropics and mesoscale convective systems at mid latitudes. We classified the gravity waves according to their sources, based on seasonal occurrence frequencies for convection and by means of topographic data. Our study reproduces well-known hotspots of gravity waves, e.g., the mountain wave hotspots at the Andes and the Antarctic Peninsula or the convective hotspot during the thunderstorm season over the North American Great Plains. However, the high horizontal resolution of the AIRS observations also helped us to locate several smaller hotspots, which were partly unknown or poorly studied so far. Most of these smaller hotspots are found near orographic features like small mountain ranges, in coastal regions, in desert areas, or near isolated islands. This new study will help to select the most promising regions and seasons for future observational studies of gravity waves. Reference: Hoffmann, L., X. Xue, and M. J. Alexander, A global view of stratospheric gravity wave hotspots located with Atmospheric Infrared Sounder observations, J. Geophys. Res., 118, 416-434, doi:10.1029/2012JD018658, 2013.

Stochastic Background of Relic Scalar Gravitational Waves tuned by Extended Gravity

International Nuclear Information System (INIS)

De Laurentis, Mariafelicia; Capozziello, Salvatore

2009-01-01

A stochastic background of relic gravitational waves is achieved by the so called adiabatically-amplified zero-point fluctuations process derived from early inflation. It provides a distinctive spectrum of relic gravitational waves. In the framework of scalar-tensor gravity, we discuss the scalar modes of gravitational waves and the primordial production of this scalar component which is generated beside tensorial one. Then analyze seven different viable f(R)-gravities towards the Solar System tests and stochastic gravitational waves background. It is demonstrated that seven viable f(R)-gravities under consideration not only satisfy the local tests, but additionally, pass the above PPN-and stochastic gravitational waves bounds for large classes of parameters.

f (T) Non-linear Massive Gravity and the Cosmic Acceleration

International Nuclear Information System (INIS)

Wu You; Chen Zu-Cheng; Wei Hao; Wang Jia-Xin

2015-01-01

Inspired by the f (R) non-linear massive gravity, we propose a new kind of modified gravity model, namely f (T) non-linear massive gravity, by adding the dRGT mass term reformulated in the vierbein formalism, to the f (T) theory. We then investigate the cosmological evolution of f (T) massive gravity, and constrain it by using the latest observational data. We find that it slightly favors a crossing of the phantom divide line from the quintessence-like phase (w_d_e > −1) to the phantom-like one (w_d_e < −1) as redshift decreases. (paper)

Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

Science.gov (United States)

Lombriser, Lucas; Lima, Nelson A.

2017-02-01

With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar-tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar-tensor modification of gravity.

Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

Energy Technology Data Exchange (ETDEWEB)

Lombriser, Lucas, E-mail: llo@roe.ac.uk; Lima, Nelson A.

2017-02-10

With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar–tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity.

Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

Directory of Open Access Journals (Sweden)

Lucas Lombriser

2017-02-01

Full Text Available With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar–tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity.

Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects

Energy Technology Data Exchange (ETDEWEB)

Vigeesh, G.; Steiner, O. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg (Germany); Jackiewicz, J., E-mail: vigeesh@leibniz-kis.de [New Mexico State University, Department of Astronomy, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003 (United States)

2017-02-01

Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in the Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high- β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.

A Comparison Between Gravity Wave Momentum Fluxes in Observations and Climate Models

Science.gov (United States)

Geller, Marvin A.; Alexadner, M. Joan; Love, Peter T.; Bacmeister, Julio; Ern, Manfred; Hertzog, Albert; Manzini, Elisa; Preusse, Peter; Sato, Kaoru; Scaife, Adam A.;

GRACILE: a comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings

Directory of Open Access Journals (Sweden)

M. Ern

2018-04-01

Full Text Available Gravity waves are one of the main drivers of atmospheric dynamics. The spatial resolution of most global atmospheric models, however, is too coarse to properly resolve the small scales of gravity waves, which range from tens to a few thousand kilometers horizontally, and from below 1 km to tens of kilometers vertically. Gravity wave source processes involve even smaller scales. Therefore, general circulation models (GCMs and chemistry climate models (CCMs usually parametrize the effect of gravity waves on the global circulation. These parametrizations are very simplified. For this reason, comparisons with global observations of gravity waves are needed for an improvement of parametrizations and an alleviation of model biases. We present a gravity wave climatology based on atmospheric infrared limb emissions observed by satellite (GRACILE. GRACILE is a global data set of gravity wave distributions observed in the stratosphere and the mesosphere by the infrared limb sounding satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER. Typical distributions (zonal averages and global maps of gravity wave vertical wavelengths and along-track horizontal wavenumbers are provided, as well as gravity wave temperature variances, potential energies and absolute momentum fluxes. This global data set captures the typical seasonal variations of these parameters, as well as their spatial variations. The GRACILE data set is suitable for scientific studies, and it can serve for comparison with other instruments (ground-based, airborne, or other satellite instruments and for comparison with gravity wave distributions, both resolved and parametrized, in GCMs and CCMs. The GRACILE data set is available as supplementary data at https://doi.org/10.1594/PANGAEA.879658.

GRACILE: a comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings

Science.gov (United States)

Ern, Manfred; Trinh, Quang Thai; Preusse, Peter; Gille, John C.; Mlynczak, Martin G.; Russell, James M., III; Riese, Martin

2018-04-01

Gravity waves are one of the main drivers of atmospheric dynamics. The spatial resolution of most global atmospheric models, however, is too coarse to properly resolve the small scales of gravity waves, which range from tens to a few thousand kilometers horizontally, and from below 1 km to tens of kilometers vertically. Gravity wave source processes involve even smaller scales. Therefore, general circulation models (GCMs) and chemistry climate models (CCMs) usually parametrize the effect of gravity waves on the global circulation. These parametrizations are very simplified. For this reason, comparisons with global observations of gravity waves are needed for an improvement of parametrizations and an alleviation of model biases. We present a gravity wave climatology based on atmospheric infrared limb emissions observed by satellite (GRACILE). GRACILE is a global data set of gravity wave distributions observed in the stratosphere and the mesosphere by the infrared limb sounding satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). Typical distributions (zonal averages and global maps) of gravity wave vertical wavelengths and along-track horizontal wavenumbers are provided, as well as gravity wave temperature variances, potential energies and absolute momentum fluxes. This global data set captures the typical seasonal variations of these parameters, as well as their spatial variations. The GRACILE data set is suitable for scientific studies, and it can serve for comparison with other instruments (ground-based, airborne, or other satellite instruments) and for comparison with gravity wave distributions, both resolved and parametrized, in GCMs and CCMs. The GRACILE data set is available as supplementary data at https://doi.org/10.1594/PANGAEA.879658" target="_blank">https://doi.org/10.1594/PANGAEA.879658.

Linear waves and instabilities

International Nuclear Information System (INIS)

Bers, A.

1975-01-01

The electrodynamic equations for small-amplitude waves and their dispersion relation in a homogeneous plasma are outlined. For such waves, energy and momentum, and their flow and transformation, are described. Perturbation theory of waves is treated and applied to linear coupling of waves, and the resulting instabilities from such interactions between active and passive waves. Linear stability analysis in time and space is described where the time-asymptotic, time-space Green's function for an arbitrary dispersion relation is developed. The perturbation theory of waves is applied to nonlinear coupling, with particular emphasis on pump-driven interactions of waves. Details of the time--space evolution of instabilities due to coupling are given. (U.S.)

Linear Water Waves

Science.gov (United States)

Kuznetsov, N.; Maz'ya, V.; Vainberg, B.

2002-08-01

This book gives a self-contained and up-to-date account of mathematical results in the linear theory of water waves. The study of waves has many applications, including the prediction of behavior of floating bodies (ships, submarines, tension-leg platforms etc.), the calculation of wave-making resistance in naval architecture, and the description of wave patterns over bottom topography in geophysical hydrodynamics. The first section deals with time-harmonic waves. Three linear boundary value problems serve as the approximate mathematical models for these types of water waves. The next section uses a plethora of mathematical techniques in the investigation of these three problems. The techniques used in the book include integral equations based on Green's functions, various inequalities between the kinetic and potential energy and integral identities which are indispensable for proving the uniqueness theorems. The so-called inverse procedure is applied to constructing examples of non-uniqueness, usually referred to as 'trapped nodes.'

Slope wavenumber spectrum models of capillary and capillary-gravity waves

Institute of Scientific and Technical Information of China (English)

贾永君; 张杰; 王岩峰

2010-01-01

Capillary and capillary-gravity waves possess a random character, and the slope wavenumber spectra of them can be used to represent mean distributions of wave energy with respect to spatial scale of variability. But simple and practical models of the slope wavenumber spectra have not been put forward so far. In this article, we address the accurate definition of the slope wavenumber spectra of water surface capillary and capillary-gravity waves. By combining the existing slope wavenumber models and using th...

On the nonlinear shaping mechanism for gravity wave spectrum in the atmosphere

Directory of Open Access Journals (Sweden)

I. P. Chunchuzov

2009-11-01

Full Text Available The nonlinear mechanism of shaping of a high vertical wave number spectral tail in the field of a few discrete internal gravity waves in the atmosphere is studied in this paper. The effects of advection of fluid parcels by interacting gravity waves are taken strictly into account by calculating wave field in Lagrangian variables, and performing a variable transformation from Lagrangian to Eulerian frame. The vertical profiles and vertical wave number spectra of the Eulerian displacement field are obtained for both the case of resonant and non-resonant wave-wave interactions. The evolution of these spectra with growing parameter of nonlinearity of the internal wave field is studied and compared to that of a broad band spectrum of gravity waves with randomly independent amplitudes and phases. The calculated vertical wave number spectra of the vertical displacements or relative temperature fluctuations are found to be consistent with the observed spectra in the middle atmosphere.

pp waves of conformal gravity with self-interacting source

International Nuclear Information System (INIS)

Ayon-Beato, Eloy; Hassaine, Mokhtar

2005-01-01

Recently, Deser, Jackiw and Pi have shown that three-dimensional conformal gravity with a source given by a conformally coupled scalar field admits pp wave solutions. In this paper, we consider this model with a self-interacting potential preserving the conformal structure. A pp wave geometry is also supported by this system and, we show that this model is equivalent to topologically massive gravity with a cosmological constant whose value is given in terms of the potential strength

ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. I. ACOUSTIC AND INERTIA-GRAVITY WAVES

Energy Technology Data Exchange (ETDEWEB)

Peralta, J.; López-Valverde, M. A. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Imamura, T. [Institute of Space and Astronautical Science-Japan Aerospace Exploration Agency 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Read, P. L. [Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford (United Kingdom); Luz, D. [Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Piccialli, A., E-mail: peralta@iaa.es [LATMOS, UVSQ, 11 bd dAlembert, 78280 Guyancourt (France)

2014-07-01

This paper is the first of a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases when the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this first part, only waves that are direct solutions of the generic dispersion relation are studied—acoustic and inertia-gravity waves. Concerning inertia-gravity waves, we found that in the cases of short horizontal wavelengths, null background wind, or propagation in the equatorial region, only pure gravity waves are possible, while for the limit of large horizontal wavelengths and/or null static stability, the waves are inertial. The correspondence between classical atmospheric approximations and wave filtering has been examined too, and we carried out a classification of the mesoscale waves found in the clouds of Venus at different vertical levels of its atmosphere. Finally, the classification of waves in exoplanets is discussed and we provide a list of possible candidates with cyclostrophic regimes.

A Plant's Response to Gravity as a Wave Guide Phenomenon

Science.gov (United States)

Wagner, Orvin

1997-11-01

Plant experimental data provides a unifying wave theory (W-wave theory) for the growth and development of plants. A plant's response to gravity is an important aspect of this theory. It appears that a plant part is tuned to the angle with which it initially grew with respect to the gravitational field and changes produce correction responses. This is true because the velocity of W-waves (whose standing waves determine plant structure) within plant tissue is found to be different in different directions (angle a) with respect to the gravitational field. I found that there are preferred values of a, namely integral multiples of near 5 degrees for some plants. Conifers apparently are more sensitive to the gravitational field than deciduous trees, in the cases studied, so their structure is determined in more detail by the gravitational field. A plant's response to gravity appears to be a fundamental phenomenon and may provide a new model for gravity that can be experimentally verified in the laboratory. Along these same lines accelerometers placed in plant tissue indicate that plants produce gravity related forces that facilitate sap flow. See the

Coupling of linearized gravity to nonrelativistic test particles: Dynamics in the general laboratory frame

International Nuclear Information System (INIS)

Speliotopoulos, A.D.; Chiao, Raymond Y.

2004-01-01

The coupling of gravity to matter is explored in the linearized gravity limit. The usual derivation of gravity-matter couplings within the quantum-field-theoretic framework is reviewed. A number of inconsistencies between this derivation of the couplings and the known results of tidal effects on test particles according to classical general relativity are pointed out. As a step towards resolving these inconsistencies, a general laboratory frame fixed on the worldline of an observer is constructed. In this frame, the dynamics of nonrelativistic test particles in the linearized gravity limit is studied, and their Hamiltonian dynamics is derived. It is shown that for stationary metrics this Hamiltonian reduces to the usual Hamiltonian for nonrelativistic particles undergoing geodesic motion. For nonstationary metrics with long-wavelength gravitational waves present (GWs), it reduces to the Hamiltonian for a nonrelativistic particle undergoing geodesic deviation motion. Arbitrary-wavelength GWs couple to the test particle through a vector-potential-like field N a , the net result of the tidal forces that the GW induces in the system, namely, a local velocity field on the system induced by tidal effects, as seen by an observer in the general laboratory frame. Effective electric and magnetic fields, which are related to the electric and magnetic parts of the Weyl tensor, are constructed from N a that obey equations of the same form as Maxwell's equations. A gedankin gravitational Aharonov-Bohm-type experiment using N a to measure the interference of quantum test particles is presented

Gravity Waves and Wind-Farm Efficiency in Neutral and Stable Conditions

Science.gov (United States)

Allaerts, Dries; Meyers, Johan

2018-02-01

We use large-eddy simulations (LES) to investigate the impact of stable stratification on gravity-wave excitation and energy extraction in a large wind farm. To this end, the development of an equilibrium conventionally neutral boundary layer into a stable boundary layer over a period of 8 h is considered, using two different cooling rates. We find that turbulence decay has considerable influence on the energy extraction at the beginning of the boundary-layer transition, but afterwards, energy extraction is dominated by geometrical and jet effects induced by an inertial oscillation. It is further shown that the inertial oscillation enhances gravity-wave excitation. By comparing LES results with a simple one-dimensional model, we show that this is related to an interplay between wind-farm drag, variations in the Froude number and the dispersive effects of vertically-propagating gravity waves. We further find that the pressure gradients induced by gravity waves lead to significant upstream flow deceleration, reducing the average turbine output compared to a turbine in isolated operation. This leads us to the definition of a non-local wind-farm efficiency, next to a more standard wind-farm wake efficiency, and we show that both can be of the same order of magnitude. Finally, an energy flux analysis is performed to further elucidate the effect of gravity waves on the flow in the wind farm.

Experimental study of the propgation and dispersion of internal atmospheric gravity waves

International Nuclear Information System (INIS)

Ballard, K.A.

1981-01-01

Traveling ionospheric disturbances (TID's) appear as large-scale transverse waves in the F-region (150 to 1000 km altitude), with frequencies on the order of 0.005 to 0.005 cycles per minute, which propagate horizontally over hundreds or even thousands of kilometers. These disturbances have been observed by various radiowave techniques over the past thirty-five years and are now generally accepted as being the manifestation, in the ionized medium, of internal atmospheric gravity waves. A model describing the propagation of gravity waves in an isothermal atmosphere is presented here. The dispersion relation is derived from fundamental principles, and the relation between phase velocity and group velocity is examined. The effects of the Coriolis force and horizontally stratified winds on wave propagation are also analyzed. Conservation of energy in the gravity wave requires increasing amplitude with increasing altitude, inasmuch as the atmospheric density decreases with height. However, this is counteracted by dissipation of wave energy by ion drag, thermal conductivity, and viscous damping. The production of TID's (in the ionized medium) by gravity waves (in the neutral medium) is discussed in quantitative terms, and the vertical predictive function is derived. Dartmouth College has operated a three-station ionosonde network in northern New Hampshire and Vermont on an intermittent basis since 1968. Seven large TID's, found in the 1969 data, are reexamined here in an exhaustive and successful comparison with the gravity wave model. Iso-true-height contours of electron density are used to determine several pertinent TID wave parameters as a function of height

Solitary wave and periodic wave solutions for the thermally forced gravity waves in atmosphere

International Nuclear Information System (INIS)

Li Ziliang

2008-01-01

By introducing a new transformation, a new direct and unified algebraic method for constructing multiple travelling wave solutions of general nonlinear evolution equations is presented and implemented in a computer algebraic system, which extends Fan's direct algebraic method to the case when r > 4. The solutions of a first-order nonlinear ordinary differential equation with a higher degree nonlinear term and Fan's direct algebraic method of obtaining exact solutions to nonlinear partial differential equations are applied to the combined KdV-mKdV-GKdV equation, which is derived from a simple incompressible non-hydrostatic Boussinesq equation with the influence of thermal forcing and is applied to investigate internal gravity waves in the atmosphere. As a result, by taking advantage of the new first-order nonlinear ordinary differential equation with a fifth-degree nonlinear term and an eighth-degree nonlinear term, periodic wave solutions associated with the Jacobin elliptic function and the bell and kink profile solitary wave solutions are obtained under the effect of thermal forcing. Most importantly, the mechanism of propagation and generation of the periodic waves and the solitary waves is analysed in detail according to the values of the heating parameter, which show that the effect of heating in atmosphere helps to excite westerly or easterly propagating periodic internal gravity waves and internal solitary waves in atmosphere, which are affected by the local excitation structures in atmosphere. In addition, as an illustrative sample, the properties of the solitary wave solution and Jacobin periodic solution are shown by some figures under the consideration of heating interaction

Magnetoelastic shear wave propagation in pre-stressed anisotropic media under gravity

Science.gov (United States)

Kumari, Nirmala; Chattopadhyay, Amares; Singh, Abhishek K.; Sahu, Sanjeev A.

2017-03-01

The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker's asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot's gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations.

On the interaction of small-scale linear waves with nonlinear solitary waves

Science.gov (United States)

Xu, Chengzhu; Stastna, Marek

2017-04-01

In the study of environmental and geophysical fluid flows, linear wave theory is well developed and its application has been considered for phenomena of various length and time scales. However, due to the nonlinear nature of fluid flows, in many cases results predicted by linear theory do not agree with observations. One of such cases is internal wave dynamics. While small-amplitude wave motion may be approximated by linear theory, large amplitude waves tend to be solitary-like. In some cases, when the wave is highly nonlinear, even weakly nonlinear theories fail to predict the wave properties correctly. We study the interaction of small-scale linear waves with nonlinear solitary waves using highly accurate pseudo spectral simulations that begin with a fully nonlinear solitary wave and a train of small-amplitude waves initialized from linear waves. The solitary wave then interacts with the linear waves through either an overtaking collision or a head-on collision. During the collision, there is a net energy transfer from the linear wave train to the solitary wave, resulting in an increase in the kinetic energy carried by the solitary wave and a phase shift of the solitary wave with respect to a freely propagating solitary wave. At the same time the linear waves are greatly reduced in amplitude. The percentage of energy transferred depends primarily on the wavelength of the linear waves. We found that after one full collision cycle, the longest waves may retain as much as 90% of the kinetic energy they had initially, while the shortest waves lose almost all of their initial energy. We also found that a head-on collision is more efficient in destroying the linear waves than an overtaking collision. On the other hand, the initial amplitude of the linear waves has very little impact on the percentage of energy that can be transferred to the solitary wave. Because of the nonlinearity of the solitary wave, these results provide us some insight into wave-mean flow

A solution of nonlinear equation for the gravity wave spectra from Adomian decomposition method: a first approach

Directory of Open Access Journals (Sweden)

Antonio Gledson Goulart

2013-12-01

Full Text Available In this paper, the equation for the gravity wave spectra in mean atmosphere is analytically solved without linearization by the Adomian decomposition method. As a consequence, the nonlinear nature of problem is preserved and the errors found in the results are only due to the parameterization. The results, with the parameterization applied in the simulations, indicate that the linear solution of the equation is a good approximation only for heights shorter than ten kilometers, because the linearization the equation leads to a solution that does not correctly describe the kinetic energy spectra.

Detection of traveling ionospheric disturbances induced by atmospheric gravity waves using the global positioning system

Science.gov (United States)

Bassiri, Sassan; Hajj, George A.

1993-01-01

Natural and man-made events like earthquakes and nuclear explosions launch atmospheric gravity waves (AGW) into the atmosphere. Since the particle density decreases exponentially with height, the gravity waves increase exponentially in amplitude as they propagate toward the upper atmosphere and ionosphere. As atmospheric gravity waves approach the ionospheric heights, the neutral particles carried by gravity waves collide with electrons and ions, setting these particles in motion. This motion of charged particles manifests itself by wave-like fluctuations and disturbances that are known as traveling ionospheric disturbances (TID). The perturbation in the total electron content due to TID's is derived analytically from first principles. Using the tilted dipole magnetic field approximation and a Chapman layer distribution for the electron density, the variations of the total electron content versus the line-of-sight direction are numerically analyzed. The temporal variation associated with the total electron content measurements due to AGW's can be used as a means of detecting characteristics of the gravity waves. As an example, detection of tsunami generated earthquakes from their associated atmospheric gravity waves using the Global Positioning System is simulated.

Linear superposition solutions to nonlinear wave equations

International Nuclear Information System (INIS)

Liu Yu

2012-01-01

The solutions to a linear wave equation can satisfy the principle of superposition, i.e., the linear superposition of two or more known solutions is still a solution of the linear wave equation. We show in this article that many nonlinear wave equations possess exact traveling wave solutions involving hyperbolic, triangle, and exponential functions, and the suitable linear combinations of these known solutions can also constitute linear superposition solutions to some nonlinear wave equations with special structural characteristics. The linear superposition solutions to the generalized KdV equation K(2,2,1), the Oliver water wave equation, and the k(n, n) equation are given. The structure characteristic of the nonlinear wave equations having linear superposition solutions is analyzed, and the reason why the solutions with the forms of hyperbolic, triangle, and exponential functions can form the linear superposition solutions is also discussed

Geometric controls of the flexural gravity waves on the Ross Ice Shelf

Science.gov (United States)

Sergienko, O. V.

2017-12-01

Long-period ocean waves, formed locally or at distant sources, can reach sub-ice-shelf cavities and excite coupled motion in the cavity and the ice shelf - flexural gravity waves. Three-dimensional numerical simulations of the flexural gravity waves on the Ross Ice Shelf show that propagation of these waves is strongly controlled by the geometry of the system - the cavity shape, its water-column thickness and the ice-shelf thickness. The results of numerical simulations demonstrate that propagation of the waves is spatially organized in beams, whose orientation is determined by the direction of the of the open ocean waves incident on the ice-shelf front. As a result, depending on the beams orientation, parts of the Ross Ice Shelf experience significantly larger flexural stresses compared to other parts where the flexural gravity beams do not propagate. Very long-period waves can propagate farther away from the ice-shelf front exciting flexural stresses in the vicinity of the grounding line.

Upper atmospheric gravity wave details revealed in nightglow satellite imagery

Science.gov (United States)

Miller, Steven D.; Straka, William C.; Yue, Jia; Smith, Steven M.; Alexander, M. Joan; Hoffmann, Lars; Setvák, Martin; Partain, Philip T.

2015-01-01

Gravity waves (disturbances to the density structure of the atmosphere whose restoring forces are gravity and buoyancy) comprise the principal form of energy exchange between the lower and upper atmosphere. Wave breaking drives the mean upper atmospheric circulation, determining boundary conditions to stratospheric processes, which in turn influence tropospheric weather and climate patterns on various spatial and temporal scales. Despite their recognized importance, very little is known about upper-level gravity wave characteristics. The knowledge gap is mainly due to lack of global, high-resolution observations from currently available satellite observing systems. Consequently, representations of wave-related processes in global models are crude, highly parameterized, and poorly constrained, limiting the description of various processes influenced by them. Here we highlight, through a series of examples, the unanticipated ability of the Day/Night Band (DNB) on the NOAA/NASA Suomi National Polar-orbiting Partnership environmental satellite to resolve gravity structures near the mesopause via nightglow emissions at unprecedented subkilometric detail. On moonless nights, the Day/Night Band observations provide all-weather viewing of waves as they modulate the nightglow layer located near the mesopause (∼90 km above mean sea level). These waves are launched by a variety of physical mechanisms, ranging from orography to convection, intensifying fronts, and even seismic and volcanic events. Cross-referencing the Day/Night Band imagery with conventional thermal infrared imagery also available helps to discern nightglow structures and in some cases to attribute their sources. The capability stands to advance our basic understanding of a critical yet poorly constrained driver of the atmospheric circulation. PMID:26630004

Duality in linearized gravity

International Nuclear Information System (INIS)

Henneaux, Marc; Teitelboim, Claudio

2005-01-01

We show that duality transformations of linearized gravity in four dimensions, i.e., rotations of the linearized Riemann tensor and its dual into each other, can be extended to the dynamical fields of the theory so as to be symmetries of the action and not just symmetries of the equations of motion. Our approach relies on the introduction of two superpotentials, one for the spatial components of the spin-2 field and the other for their canonically conjugate momenta. These superpotentials are two-index, symmetric tensors. They can be taken to be the basic dynamical fields and appear locally in the action. They are simply rotated into each other under duality. In terms of the superpotentials, the canonical generator of duality rotations is found to have a Chern-Simons-like structure, as in the Maxwell case

Propagation of internal gravity waves in the inhomogeneous atmosphere

International Nuclear Information System (INIS)

Deminov, M.G.; Ponomareva, L.I.

1988-01-01

Equations for disturbances of the density, temperature and speed of large-scale horizontally propagating internal gravity wave (IGM) wind are presented with regard to non-linearity, dispersion, molecular viscosity, thermal conductivity and background horizontal density and wind speed gradients. It is shown that values of wind speed and background atmosphere density decrease, typical of night conditions, provide for IGV amplitude increase near 250 km above the equator about 1.5 times, which with regard to the both hemispheres, fully compensates the effect of viscosity and thermal conductivity under increased solar activity. Speed and density decrease along IGW propagation can be provided both by background distribution of thermosphere parameters and by the front of a large-scale IGW on the background of which isolated IGW amplitude can grow

Gravitational Wave Polarizations in f (R Gravity and Scalar-Tensor Theory

Directory of Open Access Journals (Sweden)

Gong Yungui

2018-01-01

Full Text Available The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use gravitational waves to test alternative theories of gravity. We investigate the polarizations of gravitational waves in f (R gravity and Horndeski theory, both containing scalar modes. These theories predict that in addition to the familiar + and × polarizations, there are transverse breathing and longitudinal polarizations excited by the massive scalar mode and the new polarization is a single mixed state. It would be very difficult to detect the longitudinal polarization by interferometers, while pulsar timing array may be the better tool to detect the longitudinal polarization.

Quintessential inflation on the brane and the relic gravity wave background

International Nuclear Information System (INIS)

Sami, M.; Sahni, V.

2004-01-01

Quintessential inflation describes a scenario in which both inflation and dark energy (quintessence) are described by the same scalar field. In conventional braneworld models of quintessential inflation gravitational particle-production is used to reheat the universe. This reheating mechanism is very inefficient and results in an excessive production of gravity waves which violate nucleosynthesis constraints and invalidate the model. We describe a new method of realizing quintessential inflation on the brane in which inflation is followed by 'instant preheating' (Felder, Kofman and Linde 1999). The larger reheating temperature in this model results in a smaller amplitude of relic gravity waves which is consistent with nucleosynthesis bounds. The relic gravity wave background has a 'blue' spectrum at high frequencies and is a generic byproduct of successful quintessential inflation on the brane

Acoustic-gravity waves in atmospheric and oceanic waveguides.

Science.gov (United States)

Godin, Oleg A

2012-08-01

A theory of guided propagation of sound in layered, moving fluids is extended to include acoustic-gravity waves (AGWs) in waveguides with piecewise continuous parameters. The orthogonality of AGW normal modes is established in moving and motionless media. A perturbation theory is developed to quantify the relative significance of the gravity and fluid compressibility as well as sensitivity of the normal modes to variations in sound speed, flow velocity, and density profiles and in boundary conditions. Phase and group speeds of the normal modes are found to have certain universal properties which are valid for waveguides with arbitrary stratification. The Lamb wave is shown to be the only AGW normal mode that can propagate without dispersion in a layered medium.

The measurement of the total electron content applied to the observation of medium scale gravity wave

International Nuclear Information System (INIS)

Bertel, L.; Bertin, F.; Testud, J.

1976-01-01

The interpretation of the measurements of the integrated electron content in terms of gravity wave requires (1) a gravity wave model at thermospheric altitudes; (2) a gravity wave-ionization interaction model in the F-region of the ionosphere; and (3) a computing program for the resulting perturbation on the integrated electron content between the satellite and the earth station used. The gravity wave model considered in this paper takes into account the dissipative effects (viscosity, thermal conduction) which become very importanr above 250 km altitude and the effect of the base wind which is capable of affecting deeply the propagation of the waves of medium scale. Starting with this model, the domains of frequencies and the wavelength of atmospheric waves which may exist in the upper atmosphere are considered. The interaction of such waves and the ionization is examined. The theoretical results give information particularly on the selectivity of the ionospheric response to the wave passage. The deduced selectivity of the models appears to be smaller than that given by other authors who used simplified gravity wave models. The method for computing the perturbation of the of the integrated electron content introduced by the wave passage is given for a geostationary satellite. Computational results are presented for application to the case of medium scale gravity waves. (author)

Long-Term Observation of Small and Medium-Scale Gravity Waves over the Brazilian Equatorial Region

Science.gov (United States)

Essien, Patrick; Buriti, Ricardo; Wrasse, Cristiano M.; Medeiros, Amauri; Paulino, Igo; Takahashi, Hisao; Campos, Jose Andre

2016-07-01

This paper reports the long term observations of small and medium-scale gravity waves over Brazilian equatorial region. Coordinated optical and radio measurements were made from OLAP at Sao Joao do Cariri (7.400S, 36.500W) to investigate the occurrences and properties and to characterize the regional mesospheric gravity wave field. All-sky imager measurements were made from the site. for almost 11 consecutive years (September 2000 to November 2010). Most of the waves propagated were characterized as small-scale gravity. The characteristics of the two waves events agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the short period events, suggesting they originated from the same source regions. It was also observed that some of the medium-scale were capable of propagating into the lower thermosphere where they may have acted directly as seeds for the Rayleigh-Taylor instability development. The wave events were primarily generated by meteorological processes since there was no correlation between the evolution of the wave events and solar cycle F10.7.

Issues concerning gravity waves from first-order phase transitions

International Nuclear Information System (INIS)

Kosowsky, A.

1993-01-01

The stochastic background of gravitational radiation is a unique and potentially valuable source of information about the early universe. Photons thermally decoupled when the universe was around 100,000 years old; electromagnetic radiation cannot directly provide information about the epoch earlier than this. In contrast, gravitons presumably decoupled around the Planck time, when the universe was only 10 -44 seconds old. Since gravity wave propagate virtually unimpeded, any energetic event in the evolution of the universe will leave an imprint on the gravity wave background. Turner and Wilczek first suggested that first-order phase transitions, and particularly transitions which occur via the nucleation, expansion, and percolation of vacuum bubbles, will be a particularly efficient source of gravitational radiation. Detailed calculations with scalar-field vacuum bubbles confirm this conjecture and show that strongly first-order phase transitions are probably the strongest stochastic gravity-wave source yet conjectured. In this work the author first reviews the vacuum bubble calculations, stressing their physical assumptions. The author then discusses realistic scenarios for first-order phase transitions and describes how the calculations must be modified and extended to produce reliable results. 11 refs

Linearization instability for generic gravity in AdS spacetime

Science.gov (United States)

Altas, Emel; Tekin, Bayram

2018-01-01

In general relativity, perturbation theory about a background solution fails if the background spacetime has a Killing symmetry and a compact spacelike Cauchy surface. This failure, dubbed as linearization instability, shows itself as non-integrability of the perturbative infinitesimal deformation to a finite deformation of the background. Namely, the linearized field equations have spurious solutions which cannot be obtained from the linearization of exact solutions. In practice, one can show the failure of the linear perturbation theory by showing that a certain quadratic (integral) constraint on the linearized solutions is not satisfied. For non-compact Cauchy surfaces, the situation is different and for example, Minkowski space having a non-compact Cauchy surface, is linearization stable. Here we study, the linearization instability in generic metric theories of gravity where Einstein's theory is modified with additional curvature terms. We show that, unlike the case of general relativity, for modified theories even in the non-compact Cauchy surface cases, there are some theories which show linearization instability about their anti-de Sitter backgrounds. Recent D dimensional critical and three dimensional chiral gravity theories are two such examples. This observation sheds light on the paradoxical behavior of vanishing conserved charges (mass, angular momenta) for non-vacuum solutions, such as black holes, in these theories.

The Role of Gravity Waves in the Formation and Organization of Clouds during TWPICE

Energy Technology Data Exchange (ETDEWEB)

Reeder, Michael J. [Monash University; Lane, Todd P. [University of Melbourne; Hankinson, Mai Chi Nguyen [Monash University

2013-09-27

All convective clouds emit gravity waves. While it is certain that convectively-generated waves play important parts in determining the climate, their precise roles remain uncertain and their effects are not (generally) represented in climate models. The work described here focuses mostly on observations and modeling of convectively-generated gravity waves, using the intensive observations from the DoE-sponsored Tropical Warm Pool International Cloud Experiment (TWP-ICE), which took place in Darwin, from 17 January to 13 February 2006. Among other things, the research has implications the part played by convectively-generated gravity waves in the formation of cirrus, in the initiation and organization of further convection, and in the subgrid-scale momentum transport and associated large-scale stresses imposed on the troposphere and stratosphere. The analysis shows two groups of inertia-gravity waves are detected: group L in the middle stratosphere during the suppressed monsoon period, and group S in the lower stratosphere during the monsoon break period. Waves belonging to group L propagate to the south-east with a mean intrinsic period of 35 h, and have vertical and horizontal wavelengths of about 5-6 km and 3000-6000 km, respectively. Ray tracing calculations indicate that these waves originate from a deep convective region near Indonesia. Waves belonging to group S propagate to the south-south-east with an intrinsic period, vertical wavelength and horizontal wavelength of about 45 h, 2 km and 2000-4000 km, respectively. These waves are shown to be associated with shallow convection in the oceanic area within about 1000 km of Darwin. The intrinsic periods of high-frequency waves are estimated to be between 20-40 minutes. The high-frequency wave activity in the stratosphere, defined by mass-weighted variance of the vertical motion of the sonde, has a maximum following the afternoon local convection indicating that these waves are generated by local convection

Gravity the quest for gravitational wave

CERN Document Server

Binétruy, Pierre

2018-01-01

What force do the Big Bang, the expansion of the Universe, dark matter and dark energy, black holes, and gravitational waves all have in common? This book uncovers gravity as a key to understanding these fascinating phenomena that have so captivated public interest in recent years. Readers will discover the latest findings on how this familiar force in our everyday lives powers the most colossal changes in the Universe. Written by the widely recognized French public scientist and leading astrophysicist Pierre Binetruy, the book also explains the recent experimental confirmation of the existence of gravitational waves.

Temporal variability of tidal and gravity waves during a record long 10-day continuous lidar sounding

Science.gov (United States)

Baumgarten, Kathrin; Gerding, Michael; Baumgarten, Gerd; Lübken, Franz-Josef

2018-01-01

Gravity waves (GWs) as well as solar tides are a key driving mechanism for the circulation in the Earth's atmosphere. The propagation of gravity waves is strongly affected by tidal waves as they modulate the mean background wind field and vice versa, which is not yet fully understood and not adequately implemented in many circulation models. The daylight-capable Rayleigh-Mie-Raman (RMR) lidar at Kühlungsborn (54° N, 12° E) typically provides temperature data to investigate both wave phenomena during one full day or several consecutive days in the middle atmosphere between 30 and 75 km altitude. Outstanding weather conditions in May 2016 allowed for an unprecedented 10-day continuous lidar measurement, which shows a large variability of gravity waves and tides on timescales of days. Using a one-dimensional spectral filtering technique, gravity and tidal waves are separated according to their specific periods or vertical wavelengths, and their temporal evolution is studied. During the measurement period a strong 24 h wave occurs only between 40 and 60 km and vanishes after a few days. The disappearance is related to an enhancement of gravity waves with periods of 4-8 h. Wind data provided by ECMWF are used to analyze the meteorological situation at our site. The local wind structure changes during the observation period, which leads to different propagation conditions for gravity waves in the last days of the measurement period and therefore a strong GW activity. The analysis indicates a further change in wave-wave interaction resulting in a minimum of the 24 h tide. The observed variability of tides and gravity waves on timescales of a few days clearly demonstrates the importance of continuous measurements with high temporal and spatial resolution to detect interaction phenomena, which can help to improve parametrization schemes of GWs in general circulation models.

Approximate Stream Function wavemaker theory for highly non-linear waves in wave flumes

DEFF Research Database (Denmark)

Zhang, H.W.; Schäffer, Hemming Andreas

2007-01-01

An approximate Stream Function wavemaker theory for highly non-linear regular waves in flumes is presented. This theory is based on an ad hoe unified wave-generation method that combines linear fully dispersive wavemaker theory and wave generation for non-linear shallow water waves. This is done...... by applying a dispersion correction to the paddle position obtained for non-linear long waves. The method is validated by a number of wave flume experiments while comparing with results of linear wavemaker theory, second-order wavemaker theory and Cnoidal wavemaker theory within its range of application....

Electron non-linearities in Langmuir waves with application to beat-wave experiments

International Nuclear Information System (INIS)

Bell, A.R.; Gibbon, P.

1988-01-01

Non-linear Langmuir waves are examined in the context of the beat-wave accelerator. With a background of immobile ions the waves in one dimension are subject to the relativistic non-linearity of Rosenbluth, M.N. and Liu, C.S., Phys. Rev. Lett., 1972, 29, 701. In two or three dimensions, other electron non-linearities occur which involve electric and magnetic fields. The quasi-linear equations for these non-linearities are developed and solved numerically in a geometry representative of laser-driven beat waves. (author)

Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves.

Science.gov (United States)

Ripepe, M; Barfucci, G; De Angelis, S; Delle Donne, D; Lacanna, G; Marchetti, E

2016-11-10

Volcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencies of acoustic waves, down to much longer periods typical of gravity waves. We show that atmospheric gravity oscillations induced by volcanic eruptions and recorded by pressure sensors can be modeled as a compact source representing the rate of erupted volcanic mass. We demonstrate the feasibility of using gravity waves to derive eruption source parameters such as duration of the injection and total erupted mass with direct application in constraining plume and ash dispersal models.

Gravity waves observed from the Equatorial Wave Studies (EWS campaign during 1999 and 2000 and their role in the generation of stratospheric semiannual oscillations

Directory of Open Access Journals (Sweden)

V. Deepa

2006-10-01

Full Text Available The altitude profiles of temperature fluctuations in the stratosphere and mesosphere observed with the Rayleigh Lidar at Gadanki (13.5° N, 79.2° E on 30 nights during January to March 1999 and 21 nights during February to April 2000 were analysed to bring out the temporal and vertical propagation characteristics of gravity wave perturbations. The gravity wave perturbations showed periodicities in the 0.5–3-h range and attained large amplitudes (4–5 K in the mesosphere. The phase propagation characteristics of gravity waves with different periods showed upward wave propagation with a vertical wavelength of 5–7 km. The mean flow acceleration computed from the divergence of momentum flux of gravity waves is compared with that calculated from monthly values of zonal wind obtained from RH-200 rockets flights. Thus, the contribution of gravity waves towards the generation of Stratospheric Semi Annual Oscillation (SSAO is estimated.

Gravity wave generation from jets and fronts: idealized and real-case simulations

Science.gov (United States)

Plougonven, Riwal; Arsac, Antonin; Hertzog, Albert; Guez, Lionel; Vial, François

2010-05-01

The generation of gravity waves from jets and fronts remains an outstanding issue in the dynamics of the atmosphere. It is important to explain and quantify this emission because of the several impacts of these waves, in particular the induced momentum fluxes towards the middle atmosphere, and their contribution to turbulence and mixing, e.g. in the region of the tropopause. Yet, the mechanisms at the origin of these waves have been difficult to identify, the fundamental reason for this being the separation between the time scales of balanced motions and gravity waves. Recent simulations of idealized baroclinic life cycles and of dipoles have provided insights into the mechanisms determining the characteristics and the amplitude of gravity waves emitted by jets. It has been shown in particular that the environmental strain and shear play a crucial role in determining the characteristics and location of the emitted waves, emphasizing jet exit regions for the appearance of coherent low-frequency waves. It has also been shown how advection of relatively small-scales allow to overcome the separation of time scales alluded to above. Recent results, remaining open questions and ongoing work on these idealized simulations will be briefly summarized. Nevertheless, unavoidable shortcomings of such idealized simulations include the sensitivity of the emitted waves to model setup (resolution, diffusion, parameterizations) and uncertainty regarding the realism of this aspect of the simulations. Hence, it is necessary to compare simulations with observations in order to assess their relevance. Such comparison has been undertaken using the dataset from the Vorcore campaign (Sept. 2005 - Feb. 2006, Hertzog, J. Atmos. Ocean. Techno. 2007) during which 27 superpressure balloons drifted as quasi-Lagrangian tracers in the lower stratosphere above Antarctica and the Southern Ocean. High-resolution simulations (dx = 20 km) have been carried out using the Weather Research and Forecast

On weakly singular and fully nonlinear travelling shallow capillary–gravity waves in the critical regime

Energy Technology Data Exchange (ETDEWEB)

Mitsotakis, Dimitrios, E-mail: dmitsot@gmail.com [Victoria University of Wellington, School of Mathematics, Statistics and Operations Research, PO Box 600, Wellington 6140 (New Zealand); Dutykh, Denys, E-mail: Denys.Dutykh@univ-savoie.fr [LAMA, UMR 5127 CNRS, Université Savoie Mont Blanc, Campus Scientifique, F-73376 Le Bourget-du-Lac Cedex (France); Assylbekuly, Aydar, E-mail: asylbekuly@mail.ru [Khoja Akhmet Yassawi International Kazakh–Turkish University, Faculty of Natural Science, Department of Mathematics, 161200 Turkestan (Kazakhstan); Zhakebayev, Dauren, E-mail: daurjaz@mail.ru [Al-Farabi Kazakh National University, Faculty of Mechanics and Mathematics, Department of Mathematical and Computer Modelling, 050000 Almaty (Kazakhstan)

2017-05-25

In this Letter we consider long capillary–gravity waves described by a fully nonlinear weakly dispersive model. First, using the phase space analysis methods we describe all possible types of localized travelling waves. Then, we especially focus on the critical regime, where the surface tension is exactly balanced by the gravity force. We show that our long wave model with a critical Bond number admits stable travelling wave solutions with a singular crest. These solutions are usually referred to in the literature as peakons or peaked solitary waves. They satisfy the usual speed-amplitude relation, which coincides with Scott–Russel's empirical formula for solitary waves, while their decay rate is the same regardless their amplitude. Moreover, they can be of depression or elevation type independent of their speed. The dynamics of these solutions are studied as well. - Highlights: • A model for long capillary–gravity weakly dispersive and fully nonlinear water waves is derived. • Shallow capillary–gravity waves are classified using phase plane analysis. • Peaked travelling waves are found in the critical regime. • The dynamics of peakons in Serre–Green–Naghdi equations is studied numerically.

Acoustic-gravity modons in the atmosphere

Directory of Open Access Journals (Sweden)

L. Stenflo

Full Text Available 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.

Comparison of the Effect of Horizontal Vibrations on Interfacial Waves in a Two-Layer System of Inviscid Liquids to Effective Gravity Inversion

Science.gov (United States)

Pimenova, Anastasiya V.; Goldobin, Denis S.; Lyubimova, Tatyana P.

2018-02-01

We study the waves at the interface between two thin horizontal layers of immiscible liquids subject to high-frequency tangential vibrations. Nonlinear governing equations are derived for the cases of two- and three-dimensional flows and arbitrary ratio of layer thicknesses. The derivation is performed within the framework of the long-wavelength approximation, which is relevant as the linear instability of a thin-layers system is long-wavelength. The dynamics of equations is integrable and the equations themselves can be compared to the Boussinesq equation for the gravity waves in shallow water, which allows one to compare the action of the vibrational field to the action of the gravity and its possible effective inversion.

Quantum spreading of a self-gravitating wave-packet in singularity free gravity

Science.gov (United States)

Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

2018-01-01

In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein's general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1 / r singularity in the potential - such that the gradient of the potential vanishes within the scale of non-locality. We will show that a quantum wave-packet spreads faster for a ghost-free and singularity-free gravity as compared to the Newtonian case, therefore providing us a unique scenario for testing classical and quantum properties of short-distance gravity in a laboratory in the near future.

A Study of Mesoscale Gravity Waves over the North Atlantic with Satellite Observations and a Mesoscale Model

Science.gov (United States)

Wu, Dong L.; Zhang, Fuqing

2004-01-01

Satellite microwave data are used to study gravity wave properties and variabilities over the northeastern United States and the North Atlantic in the December-January periods. The gravity waves in this region, found in many winters, can reach the stratopause with growing amplitude. The Advanced Microwave Sounding Unit-A (AMSU-A) observations show that the wave occurrences are correlated well with the intensity and location of the tropospheric baroclinic jet front systems. To further investigate the cause(s) and properties of the North Atlantic gravity waves, we focus on a series of wave events during 19-21 January 2003 and compare AMSU-A observations to simulations from a mesoscale model (MM5). The simulated gravity waves compare qualitatively well with the satellite observations in terms of wave structures, timing, and overall morphology. Excitation mechanisms of these large-amplitude waves in the troposphere are complex and subject to further investigations.

Study of gravity waves propagation in the thermosphere of Mars based on MAVEN/NGIMS density measurements

Science.gov (United States)

Vals, M.

2017-09-01

We use MAVEN/NGIMS CO2 density measurements to analyse gravity waves in the thermosphere of Mars. In particular the seasonal/latitudinal variability of their amplitude is studied and interpreted. Key background parameters controlling the activity of gravity waves are analysed with the help of the Mars Climate Database (MCD). Gravity waves activity presents a good anti-correlation to the temperature variability retrieved from the MCD. An analysis at pressure levels is ongoing.

Atmospheric gravity waves due to the Tohoku-Oki tsunami observed in the thermosphere by GOCE

NARCIS (Netherlands)

Garcia, R.F.; Doornbos, E.N.; Bruinsma, S.; Hebert, H.

2014-01-01

Oceanic tsunami waves couple with atmospheric gravity waves, as previously observed through ionospheric and airglow perturbations. Aerodynamic velocities and density variations are computed from Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) accelerometer and thruster data during

Interaction between ionization and gravity waves in the upper atmosphere

International Nuclear Information System (INIS)

Balcioglu, O.

1982-10-01

It is known that travelling ionospheric disturbances are produced by gravity waves. During their movement from the F region downwards to the E region, gravity waves can produce thin layers called transients on ionograms and, if the wave motion persists, 'h-type Esub(S) can be produced. To investigate the problem, the continuity equations for both the E and F regions are solved for a perturbation, the motion of which is taken to be a gravity wave. Hitherto, N'/N 0 , the ratio of the disturbed to the undisturbed electron density, has been calculated by using only the Hall conductivity and ignoring the diffusion term for the F region. In the present calculations we have used Pedersan and Hall conductivities and calculated the N'/N 0 ratio for both the E and F regions. Using CIRA standard atmosphere data we find for the F region that N' can exceed N 0 by up to 4 percent, depending on the horizontal wind velocity. In the E region, N' reaches much higher values than in the F region. Thus at 120 km if we take a typical horizontal wind velocity of 80 m/sec (wavelength 150 km), N' is about twice as large as N 0 . From these results we see that the diffusion term is important for the E region. (author)

A case study of typhoon-induced gravity waves and the orographic impacts related to Typhoon Mindulle (2004) over Taiwan

OpenAIRE

Wu, J. F.; Xue, X. H.; Hoffmann, L.; Dou, X. K.; Li, H. M.; Chen, T. D.

2015-01-01

Atmospheric gravity waves (GWs) significantly influence global circulation. Deep convection, particularly that associated with typhoons, is believed to be an important source of gravity waves. Stratospheric gravity waves induced by Typhoon Mindulle (2004) were detected by the Atmospheric Infrared Sounder (AIRS). Semicircular GWs with horizontal wavelengths of 100–400 km were found over Taiwan through an inspection of AIRS radiances at 4.3 μm. Characteristics of the stratospheric gravity waves...

Dynamics of Nearshore Sand Bars and Infra-gravity Waves: The Optimal Theory Point of View

Science.gov (United States)

Bouchette, F.; Mohammadi, B.

2016-12-01

It is well known that the dynamics of near-shore sand bars are partly controlled by the features (location of nodes, amplitude, length, period) of the so-called infra-gravity waves. Reciprocally, changes in the location, size and shape of near-shore sand bars can control wave/wave interactions which in their turn alter the infra-gravity content of the near-shore wave energy spectrum. The coupling infra-gravity / near-shore bar is thus definitely two ways. Regarding numerical modelling, several approaches have already been considered to analyze such coupled dynamics. Most of them are based on the following strategy: 1) define an energy spectrum including infra-gravity, 2) tentatively compute the radiation stresses driven by this energy spectrum, 3) compute sediment transport and changes in the seabottom elevation including sand bars, 4) loop on the computation of infra-gravity taking into account the morphological changes. In this work, we consider an alternative approach named Nearshore Optimal Theory, which is a kind of breakdown point of view for the modeling of near-shore hydro-morphodynamics and wave/ wave/ seabottom interactions. Optimal theory applied to near-shore hydro-morphodynamics arose with the design of solid coastal defense structures by shape optimization methods, and is being now extended in order to model dynamics of any near-shore system combining waves and sand. The basics are the following: the near-shore system state is through a functional J representative of the energy of the system in some way. This J is computed from a model embedding the physics to be studied only (here hydrodynamics forced by simple infra-gravity). Then the paradigm is to say that the system will evolve so that the energy J tends to minimize. No really matter the complexity of wave propagation nor wave/bottom interactions. As soon as J embeds the physics to be explored, the method does not require a comprehensive modeling. Near-shore Optimal Theory has already given

Properties of surface waves in granular media under gravity

International Nuclear Information System (INIS)

Zheng He-Peng

2014-01-01

Acoustical waves propagating along the free surface of granular media under gravity are investigated in the framework of elasticity theory. The influence of stress on a surface wave is analyzed. The results have shown that two types of surface waves, namely sagittal and transverse modes exist depending on initial stress states, which may have some influence on the dispersion relations of surface waves, but the influence is not great. Considering that the present experimental accuracy is far from distinguishing this detail, the validity of elasticity theory on the surface waves propagating in granular media can still be maintained. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Agradient velocity, vortical motion and gravity waves in a rotating shallow-water model

Science.gov (United States)

Sutyrin Georgi, G.

2004-07-01

A new approach to modelling slow vortical motion and fast inertia-gravity waves is suggested within the rotating shallow-water primitive equations with arbitrary topography. The velocity is exactly expressed as a sum of the gradient wind, described by the Bernoulli function,B, and the remaining agradient part, proportional to the velocity tendency. Then the equation for inverse potential vorticity,Q, as well as momentum equations for agradient velocity include the same source of intrinsic flow evolution expressed as a single term J (B, Q), where J is the Jacobian operator (for any steady state J (B, Q) = 0). Two components of agradient velocity are responsible for the fast inertia-gravity wave propagation similar to the traditionally used divergence and ageostrophic vorticity. This approach allows for the construction of balance relations for vortical dynamics and potential vorticity inversion schemes even for moderate Rossby and Froude numbers assuming the characteristic value of |J(B, Q)| = to be small. The components of agradient velocity are used as the fast variables slaved to potential vorticity that allows for diagnostic estimates of the velocity tendency, the direct potential vorticity inversion with the accuracy of 2 and the corresponding potential vorticity-conserving agradient velocity balance model (AVBM). The ultimate limitations of constructing the balance are revealed in the form of the ellipticity condition for balanced tendency of the Bernoulli function which incorporates both known criteria of the formal stability: the gradient wind modified by the characteristic vortical Rossby wave phase speed should be subcritical. The accuracy of the AVBM is illustrated by considering the linear normal modes and coastal Kelvin waves in the f-plane channel with topography.

Gravity's kiss the detection of gravitational waves

CERN Document Server

Collins, Harry

2017-01-01

Scientists have been trying to confirm the existence of gravitational waves for fifty years. Then, in September 2015, came a "very interesting event" (as the cautious subject line in a physicist's email read) that proved to be the first detection of gravitational waves. In Gravity's Kiss, Harry Collins -- who has been watching the science of gravitational wave detection for forty-three of those fifty years and has written three previous books about it -- offers a final, fascinating account, written in real time, of the unfolding of one of the most remarkable scientific discoveries ever made. Predicted by Einstein in his theory of general relativity, gravitational waves carry energy from the collision or explosion of stars. Dying binary stars, for example, rotate faster and faster around each other until they merge, emitting a burst of gravitational waves. It is only with the development of extraordinarily sensitive, highly sophisticated detectors that physicists can now confirm Einstein's prediction. This is...

F region manifestation of atmospheric gravity waves at a high magnetic dip station

International Nuclear Information System (INIS)

Yeh, K.C.; Dubroff, R.E.; Nagpal, O.P.

1976-01-01

An average power spectrum of the observed fluctuations in electron content at Urbana has been computed. Several features of the experimental results can be explained in terms of theoretical models of the ionospheric response to internal gravity waves. An extension of an earlier theory to include the effect of dissipation provides additional justification for the relation between the observed electron content fluctuations and internal gravity waves

A statistical study of gravity waves from radiosonde observations at Wuhan (30° N, 114° E China

Directory of Open Access Journals (Sweden)

S. D. Zhang

2005-03-01

Full Text Available Several works concerning the dynamical and thermal structures and inertial gravity wave activities in the troposphere and lower stratosphere (TLS from the radiosonde observation have been reported before, but these works were concentrated on either equatorial or polar regions. In this paper, background atmosphere and gravity wave activities in the TLS over Wuhan (30° N, 114° E (a medium latitudinal region were statistically studied by using the data from radiosonde observations on a twice daily basis at 08:00 and 20:00 LT in the period between 2000 and 2002. The monthly-averaged temperature and horizontal winds exhibit the essential dynamic and thermal structures of the background atmosphere. For avoiding the extreme values of background winds and temperature in the height range of 11-18km, we studied gravity waves, respectively, in two separate height regions, one is from ground surface to 10km (lower part, and the other is within 18-25km (upper part. In total, 791 and 1165 quasi-monochromatic inertial gravity waves were extracted from our data set for the lower and upper parts, respectively. The gravity wave parameters (intrinsic frequencies, amplitudes, wavelengths, intrinsic phase velocities and wave energies are calculated and statistically studied. The statistical results revealed that in the lower part, there were 49.4% of gravity waves propagating upward, and the percentage was 76.4% in the upper part. Moreover, the average wave amplitudes and energies are less than those at the lower latitudinal regions, which indicates that the gravity wave parameters have a latitudinal dependence. The correlated temporal evolution of the monthly-averaged wave energies in the lower and upper parts and a subsequent quantitative analysis strongly suggested that at the observation site, dynamical instability (strong wind shear induced by the tropospheric jet is the main excitation source of inertial gravity waves in the TLS.

Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

Directory of Open Access Journals (Sweden)

Colin C. Triplett

2017-01-01

Full Text Available The meteorological control of gravity wave activity through filtering by winds and generation by spontaneous adjustment of unbalanced flows is investigated. This investigation is based on a new analysis of Rayleigh LiDAR measurements of gravity wave activity in the upper stratosphere-lower mesosphere (USLM,40–50kmon 152 nights at Poker Flat Research Range (PFRR, Chatanika, Alaska (65◦ N, 147◦ W, over 13 years between 1998 and 2014. The LiDAR measurements resolve inertia-gravity waves with observed periods between 1 h and 4 h and vertical wavelengths between 2 km and 10 km. The meteorological conditions are defined by reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA. The gravity wave activity shows large night-to-night variability, but a clear annual cycle with a maximum in winter,and systematic interannual variability associated with stratospheric sudden warming events. The USLM gravity wave activity is correlated with the MERRA winds and is controlled by the winds in the lower stratosphere through filtering by critical layer filtering. The USLM gravity wave activity is also correlated with MERRA unbalanced flow as characterized by the residual of the nonlinear balance equation. This correlation with unbalanced flow only appears when the wind conditions are taken into account, indicating that wind filtering is the primary control of the gravity wave activity.

Quantum spreading of a self-gravitating wave-packet in singularity free gravity

Energy Technology Data Exchange (ETDEWEB)

Buoninfante, Luca [Universita di Salerno, Dipartimento di Fisica ' ' E.R. Caianiello' ' , Fisciano (Italy); INFN-Sezione di Napoli, Gruppo Collegato di Salerno, Fisciano (Italy); University of Groningen, Van Swinderen Institute, Groningen (Netherlands); Lambiase, Gaetano [Universita di Salerno, Dipartimento di Fisica ' ' E.R. Caianiello' ' , Fisciano (Italy); INFN-Sezione di Napoli, Gruppo Collegato di Salerno, Fisciano (Italy); Mazumdar, Anupam [University of Groningen, Van Swinderen Institute, Groningen (Netherlands); University of Groningen, Kapteyn Astronomical Institute, Groningen (Netherlands)

2018-01-15

In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein's general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1/r singularity in the potential - such that the gradient of the potential vanishes within the scale of non-locality. We will show that a quantum wave-packet spreads faster for a ghost-free and singularity-free gravity as compared to the Newtonian case, therefore providing us a unique scenario for testing classical and quantum properties of short-distance gravity in a laboratory in the near future. (orig.)

Testing strong gravity with gravitational waves and Love numbers

International Nuclear Information System (INIS)

Franzin, E; Cardoso, V; Raposo, G; Pani, P

2017-01-01

The LIGO observation of GW150914 has inaugurated the gravitational-wave astronomy era and the possibility of testing gravity in extreme regimes. While distorted black holes are the most convincing sources of gravitational waves, similar signals might be produced also by other compact objects. In particular, we discuss what the gravitational-wave ringdown could tell us about the nature of the emitting object, and how measurements of the tidal Love numbers could help us in understanding the internal structure of compact dark objects. (paper)

Effect of Gravity Waves from Small Islands in the Southern Ocean on the Southern Hemisphere Atmospheric Circulation

Science.gov (United States)

Garfinkel, C. I.; Oman, L. D.

2018-01-01

The effect of small islands in the Southern Ocean on the atmospheric circulation in the Southern Hemisphere is considered with a series of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model in which the gravity wave stress generated by these islands is increased to resemble observed values. The enhanced gravity wave drag leads to a 2 K warming of the springtime polar stratosphere, partially ameliorating biases in this region. Resolved wave drag declines in the stratospheric region in which the added orographic gravity waves deposit their momentum, such that changes in gravity waves are partially compensated by changes in resolved waves, though resolved wave drag increases further poleward. The orographic drag from these islands has impacts for surface climate, as biases in tropospheric jet position are also partially ameliorated. These results suggest that these small islands are likely contributing to the missing drag near 60 degrees S in the upper stratosphere evident in many data assimilation products.

Improved analysis of all-sky meteor radar measurements of gravity wave variances and momentum fluxes

Directory of Open Access Journals (Sweden)

V. F. Andrioli

2013-05-01

Full Text Available The advantages of using a composite day analysis for all-sky interferometric meteor radars when measuring mean winds and tides are widely known. On the other hand, problems arise if this technique is applied to Hocking's (2005 gravity wave analysis for all-sky meteor radars. In this paper we describe how a simple change in the procedure makes it possible to use a composite day in Hocking's analysis. Also, we explain how a modified composite day can be constructed to test its ability to measure gravity wave momentum fluxes. Test results for specified mean, tidal, and gravity wave fields, including tidal amplitudes and gravity wave momentum fluxes varying strongly with altitude and/or time, suggest that the modified composite day allows characterization of monthly mean profiles of the gravity wave momentum fluxes, with good accuracy at least at the altitudes where the meteor counts are large (from 89 to 92.5 km. In the present work we also show that the variances measured with Hocking's method are often contaminated by the tidal fields and suggest a method of empirical correction derived from a simple simulation model. The results presented here greatly increase our confidence because they show that our technique is able to remove the tide-induced false variances from Hocking's analysis.

Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation.

Science.gov (United States)

Tsuda, Toshitaka

2014-01-01

The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10-100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50-90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10-50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet.

Can gravity waves significantly impact PSC occurrence in the Antarctic?

Directory of Open Access Journals (Sweden)

R. M. Woollands

2009-11-01

Full Text Available A combination of POAM III aerosol extinction and CHAMP RO temperature measurements are used to examine the role of atmospheric gravity waves in the formation of Antarctic Polar Stratospheric Clouds (PSCs. POAM III aerosol extinction observations and quality flag information are used to identify Polar Stratospheric Clouds using an unsupervised clustering algorithm.

A PSC proxy, derived by thresholding Met Office temperature analyses with the PSC Type Ia formation temperature (T_NAT, shows general agreement with the results of the POAM III analysis. However, in June the POAM III observations of PSC are more abundant than expected from temperature threshold crossings in five out of the eight years examined. In addition, September and October PSC identified using temperature thresholding is often significantly higher than that derived from POAM III; this observation probably being due to dehydration and denitrification. Comparison of the Met Office temperature analyses with corresponding CHAMP observations also suggests a small warm bias in the Met Office data in June. However, this bias cannot fully explain the differences observed.

Analysis of CHAMP data indicates that temperature perturbations associated with gravity waves may partially explain the enhanced PSC incidence observed in June (relative to the Met Office analyses. For this month, approximately 40% of the temperature threshold crossings observed using CHAMP RO data are associated with small-scale perturbations. Examination of the distribution of temperatures relative to T_NAT shows a large proportion of June data to be close to this threshold, potentially enhancing the importance of gravity wave induced temperature perturbations. Inspection of the longitudinal structure of PSC occurrence in June 2005 also shows that regions of enhancement are geographically associated with the Antarctic Peninsula; a known mountain wave "hotspot". The

Atmospheric gravity wave detection following the 2011 Tohoku earthquakes combining COSMIC occultation and GPS observations

Science.gov (United States)

Yan, X.; Tao, Y.; Xia, C.; Qi, Y.; Zuo, X.

2017-12-01

Several studies have reported the earthquake-induced atmospheric gravity waves detected by some new technologies such as airglow (Makela et al., 2011), GOCE (Garcia et al., 2013), GRACE (Yang et al., 2014), F3/C radio occultation sounding (Coïsson et al., 2015). In this work, we collected all occultation events on 11 March, and selected four events to analyze at last. The original and filtered podTEC is represented as function of the altitude of the impact parameter and UT of the four events. Then, the travel time diagrams of filtered podTEC derived from the events were analyzed. The occultation signal from one event (marked as No.73) is consistent with the previous results reported by Coïsson. 2015, which is corresponds to the ionospheric signal induced from tsunami gravity wave. What is noticeable, in this work, is that three occultation events of No.403, 77 and 118 revealed a disturbance of atmospheric gravity wave with velocity 300m/s, preceding the tsunami. It would probably be correspond to the gravity waves caused by seismic rupture but not tsunami. In addition, it can be seen that the perturbation height of occultation observation TEC is concentrated at 200-400km, corresponding ionosphere F region. The signals detected above are compared with GPS measurements of TEC from GEONET and IGS. From GPS data, traveling ionospheric disturbances were observed spreading out from the epicenter as a quasi-circular propagation pattern with the time. Exactly, we observed an acoustic wave coupled with Rayleigh wave starting from the epicenter with a speed of 3.0km/s and a superimposed acoustic-gravity wave moving with a speed of 800m/s. The acoustic-gravity wave generated at the epicenter and gradually attenuated 800km away, then it is replaced by a gravity wave coupled with the tsunami that moves with a speed of between 100 and 300m/s. It is necessary to confirm the propagation process of the waves if we attempt to evaluate the use of ionospheric seismology as a

Observation of gravity waves during the extreme tornado outbreak of 3 April 1974

Science.gov (United States)

Hung, R. J.; Phan, T.; Smith, R. E.

1978-01-01

A continuous wave-spectrum high-frequency radiowave Doppler sounder array was used to observe upper-atmospheric disturbances during an extreme tornado outbreak. The observations indicated that gravity waves with two harmonic wave periods were detected at the F-region ionospheric height. Using a group ray path computational technique, the observed gravity waves were traced in order to locate potential sources. The signals were apparently excited 1-3 hours before tornado touchdown. Reverse ray tracing indicated that the wave source was located at the aurora zone with a Kp index of 6 at the time of wave excitation. The summation of the 24-hour Kp index for the day was 36. The results agree with existing theories (Testud, 1970; Titheridge, 1971; Kato, 1976) for the excitation of large-scale traveling ionospheric disturbances associated with geomagnetic activity in the aurora zone.

Research on linear driving of wave maker; Zoha sochi no linear drive ka kenkyu

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, I; Taniguchi, S; Nohara, T [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

1997-10-01

The water tank test of marine structures or submarine structures uses a wave maker to generate waves. A typical flap wave maker uses the wave making flap penetrating a water surface whose bottom is fixed on a tank bottom through a hinge, and the top is connected with a rod driven by rotating servomotor for reciprocating motion of the flap. However, this driving gear using a rotating servomotor and a bowl- screw has some defects such as noise caused by bowl rotation, backlash due to wear and limited driving speed. A linear motor with less friction mechanisms was thus applied to the driving gear. The performance test result of the prototype driving gear using a linear motor showed the possibility of the linear driven wave maker. The linear driven wave maker could also achieve low noise and simple mechanism. The sufficient durability and applicability of the linear driven wave maker mechanism were confirmed through strength calculation necessary for improving the prototype wave maker. 1 ref., 5 figs., 2 tabs.

Spherically symmetric analysis on open FLRW solution in non-linear massive gravity

Energy Technology Data Exchange (ETDEWEB)

Chiang, Chien-I; Izumi, Keisuke; Chen, Pisin, E-mail: chienichiang@berkeley.edu, E-mail: izumi@phys.ntu.edu.tw, E-mail: chen@slac.stanford.edu [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei 10617, Taiwan (China)

2012-12-01

We study non-linear massive gravity in the spherically symmetric context. Our main motivation is to investigate the effect of helicity-0 mode which remains elusive after analysis of cosmological perturbation around an open Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. The non-linear form of the effective energy-momentum tensor stemming from the mass term is derived for the spherically symmetric case. Only in the special case where the area of the two sphere is not deviated away from the FLRW universe, the effective energy momentum tensor becomes completely the same as that of cosmological constant. This opens a window for discriminating the non-linear massive gravity from general relativity (GR). Indeed, by further solving these spherically symmetric gravitational equations of motion in vacuum to the linear order, we obtain a solution which has an arbitrary time-dependent parameter. In GR, this parameter is a constant and corresponds to the mass of a star. Our result means that Birkhoff's theorem no longer holds in the non-linear massive gravity and suggests that energy can probably be emitted superluminously (with infinite speed) on the self-accelerating background by the helicity-0 mode, which could be a potential plague of this theory.

Comparison of Global Distributions of Zonal-Mean Gravity Wave Variance Inferred from Different Satellite Instruments

Science.gov (United States)

Preusse, Peter; Eckermann, Stephen D.; Offermann, Dirk; Jackman, Charles H. (Technical Monitor)

2000-01-01

Gravity wave temperature fluctuations acquired by the CRISTA instrument are compared to previous estimates of zonal-mean gravity wave temperature variance inferred from the LIMS, MLS and GPS/MET satellite instruments during northern winter. Careful attention is paid to the range of vertical wavelengths resolved by each instrument. Good agreement between CRISTA data and previously published results from LIMS, MLS and GPS/MET are found. Key latitudinal features in these variances are consistent with previous findings from ground-based measurements and some simple models. We conclude that all four satellite instruments provide reliable global data on zonal-mean gravity wave temperature fluctuations throughout the middle atmosphere.

Investigation of fog structure affected by gravity waves and turbulence in the mountainous region of Pyeongchang, Korea, the place for the 2018 Winter Olympics and Paralympics

Science.gov (United States)

La, I.; Yum, S. S.; Yeom, J. M.; Gultepe, I.

2017-12-01

Since microphysical and dynamical processes of fog are not well-known and have non-linear relationships among processes that are related to fog formation, improving the accuracy of the fog forecasting/nowcasting system is challenging. For these reasons, understanding the fog mechanism is needed to develop the fog forecasting system. So, we focus on understanding fog-turbulence interactions and fog-gravity wave interactions. Many studies noted that turbulence plays important roles in fog. However, a discrepancy between arguments for the effect of turbulent mixing on fog formation exists. Several studies suggested that turbulent mixing suppresses fog formation. Some other studies reported that turbulent mixing contributes to fog formation. On the other hand, several quasi-periodic oscillations of temperature, visibility, and vertical velocity, which have period of 10-20 minutes, were observed to be related to gravity waves in fog; because gravity waves play significant dynamic roles in the atmosphere. Furthermore, a numerical study suggested that gravity waves, simulated near the top of the fog layer, may affect fog microphysics. Thus, we investigate the effects of turbulent mixing on fog formation and the influences of gravity waves on fog microphysics to understand fog structure in Pyeongchang. In these studies, we analyze the data that are obtained from doppler lidar and 3.5 m meteorological observation tower including 3D-ultrasonic anemometer, IR sensor, and fog monitor during ICE-POP (International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games) campaign. In these instruments, doppler lidar is a good instrument to observe the gravity waves near the fog top, while in situ measurements have small spatial coverage. The instruments are installed at the mountainous terrain of Pyeongchang, Korea. More details will be presented at the conference.

Temporal variability of gravity wave drag - vertical coupling and possible climate links

Science.gov (United States)

Miksovsky, Jiri; Sacha, Petr; Kuchar, Ales; Pisoft, Petr

2017-04-01

In the atmosphere, the internal gravity waves (IGW) are one of the fastest ways of natural information transfer in the vertical direction. Tropospheric changes that result in modification of sourcing, propagation or breaking conditions for IGWs almost immediately influence the distribution of gravity wave drag in the stratosphere. So far most of the related studies deal with IGW impacts higher in the upper stratospheric/mesospheric region and with the modulation of IGWs by planetary waves. This is most likely due to the fact that IGWs induce highest accelerations in the mesosphere and lower thermosphere region. However, the imposed drag force is much bigger in the stratosphere. In the presented analysis, we have assessed the relationship between the gravity wave activity in the stratosphere and other climatic phenomena through statistical techniques. Multivariable regression has been applied to investigate the IGW-related eastward and northward wind tendencies in the CMAM30-SD data, subject to the explanatory variables involving local circulation characteristics (derived from regional configuration of the thermobaric field) as well as the phases of the large-scale internal climate variability modes (ENSO, NAO, QBO). Our tests have highlighted several geographical areas with statistically significant responses of the orographic gravity waves effect to each of the variability modes under investigation; additional experiments have also indicated distinct signs of nonlinearity in some of the links uncovered. Furthermore, we have also applied composite analysis of displaced and split stratospheric polar vortex events (SPV) from CMAM30-SD to focus on how the strength and occurrence of the IGW hotspots can play a role in SPV occurrence and frequency.

Gravity induced wave function collapse

Science.gov (United States)

Gasbarri, G.; Toroš, M.; Donadi, S.; Bassi, A.

2017-11-01

Starting from an idea of S. L. Adler [in Quantum Nonlocality and Reality: 50 Years of Bell's Theorem, edited by M. Bell and S. Gao (Cambridge University Press, Cambridge, England 2016)], we develop a novel model of gravity induced spontaneous wave function collapse. The collapse is driven by complex stochastic fluctuations of the spacetime metric. After deriving the fundamental equations, we prove the collapse and amplification mechanism, the two most important features of a consistent collapse model. Under reasonable simplifying assumptions, we constrain the strength ξ of the complex metric fluctuations with available experimental data. We show that ξ ≥10-26 in order for the model to guarantee classicality of macro-objects, and at the same time ξ ≤10-20 in order not to contradict experimental evidence. As a comparison, in the recent discovery of gravitational waves in the frequency range 35 to 250 Hz, the (real) metric fluctuations reach a peak of ξ ˜10-21.

Propagation of inertial-gravity waves on an island shelf

Science.gov (United States)

Bondur, V. G.; Sabinin, K. D.; Grebenyuk, Yu. V.

2015-09-01

The propagation of inertial-gravity waves (IGV) at the boundary of the Pacific shelf near the island of Oahu (Hawaii), whose generation was studied in the first part of this work [1], is analyzed. It is shown that a significant role there is played by the plane oblique waves; whose characteristics were identified by the method of estimating 3D wave parameters for the cases when the measurements are available only for two verticals. It is established that along with the descending propagation of energy that is typical of IGVs, wave packets ascend from the bottom to the upper layers, which is caused by the emission of waves from intense jets of discharged waters flowing out of a diffusor located at the bottom.

Propagation of acoustic-gravity waves in arctic zones with elastic ice-sheets

Science.gov (United States)

Kadri, Usama; Abdolali, Ali; Kirby, James T.

2017-04-01

We present an analytical solution of the boundary value problem of propagating acoustic-gravity waves generated in the ocean by earthquakes or ice-quakes in arctic zones. At the surface, we assume elastic ice-sheets of a variable thickness, and show that the propagating acoustic-gravity modes have different mode shape than originally derived by Ref. [1] for a rigid ice-sheet settings. Computationally, we couple the ice-sheet problem with the free surface model by Ref. [2] representing shrinking ice blocks in realistic sea state, where the randomly oriented ice-sheets cause inter modal transition at the edges and multidirectional reflections. We then derive a depth-integrated equation valid for spatially slowly varying thickness of ice-sheet and water depth. Surprisingly, and unlike the free-surface setting, here it is found that the higher acoustic-gravity modes exhibit a larger contribution. These modes travel at the speed of sound in water carrying information on their source, e.g. ice-sheet motion or submarine earthquake, providing various implications for ocean monitoring and detection of quakes. In addition, we found that the propagating acoustic-gravity modes can result in orbital displacements of fluid parcels sufficiently high that may contribute to deep ocean currents and circulation, as postulated by Refs. [1, 3]. References [1] U. Kadri, 2016. Generation of Hydroacoustic Waves by an Oscillating Ice Block in Arctic Zones. Advances in Acoustics and Vibration, 2016, Article ID 8076108, 7 pages http://dx.doi.org/10.1155/2016/8076108 [2] A. Abdolali, J. T. Kirby and G. Bellotti, 2015, Depth-integrated equation for hydro-acoustic waves with bottom damping, J. Fluid Mech., 766, R1 doi:10.1017/jfm.2015.37 [3] U. Kadri, 2014. Deep ocean water transportation by acoustic?gravity waves. J. Geophys. Res. Oceans, 119, doi:10.1002/ 2014JC010234

Three-Dimensional Coupled NLS Equations for Envelope Gravity Solitary Waves in Baroclinic Atmosphere and Modulational Instability

Directory of Open Access Journals (Sweden)

Baojun Zhao

2018-01-01

Full Text Available Envelope gravity solitary waves are an important research hot spot in the field of solitary wave. And the weakly nonlinear model equations system is a part of the research of envelope gravity solitary waves. Because of the lack of technology and theory, previous studies tried hard to reduce the variable numbers and constructed the two-dimensional model in barotropic atmosphere and could only describe the propagation feature in a direction. But for the propagation of envelope gravity solitary waves in real ocean ridges and atmospheric mountains, the three-dimensional model is more appropriate. Meanwhile, the baroclinic problem of atmosphere is also an inevitable topic. In the paper, the three-dimensional coupled nonlinear Schrödinger (CNLS equations are presented to describe the evolution of envelope gravity solitary waves in baroclinic atmosphere, which are derived from the basic dynamic equations by employing perturbation and multiscale methods. The model overcomes two disadvantages: (1 baroclinic problem and (2 propagation path problem. Then, based on trial function method, we deduce the solution of the CNLS equations. Finally, modulational instability of wave trains is also discussed.

Quantum-Wave Equation and Heisenberg Inequalities of Covariant Quantum Gravity

Directory of Open Access Journals (Sweden)

Claudio Cremaschini

2017-07-01

Full Text Available Key aspects of the manifestly-covariant theory of quantum gravity (Cremaschini and Tessarotto 2015–2017 are investigated. These refer, first, to the establishment of the four-scalar, manifestly-covariant evolution quantum wave equation, denoted as covariant quantum gravity (CQG wave equation, which advances the quantum state ψ associated with a prescribed background space-time. In this paper, the CQG-wave equation is proved to follow at once by means of a Hamilton–Jacobi quantization of the classical variational tensor field g ≡ g μ ν and its conjugate momentum, referred to as (canonical g-quantization. The same equation is also shown to be variational and to follow from a synchronous variational principle identified here with the quantum Hamilton variational principle. The corresponding quantum hydrodynamic equations are then obtained upon introducing the Madelung representation for ψ , which provides an equivalent statistical interpretation of the CQG-wave equation. Finally, the quantum state ψ is proven to fulfill generalized Heisenberg inequalities, relating the statistical measurement errors of quantum observables. These are shown to be represented in terms of the standard deviations of the metric tensor g ≡ g μ ν and its quantum conjugate momentum operator.

Frozen-wave instability in near-critical hydrogen subjected to horizontal vibration under various gravity fields.

Science.gov (United States)

Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

2014-01-01

The frozen-wave instability which appears at a liquid-vapor interface when a harmonic vibration is applied in a direction tangential to it has been less studied until now. The present paper reports experiments on hydrogen (H2) in order to study this instability when the temperature is varied near its critical point for various gravity levels. Close to the critical point, a liquid-vapor density difference and surface tension can be continuously varied with temperature in a scaled, universal way. The effect of gravity on the height of the frozen waves at the interface is studied by performing the experiments in a magnetic facility where effective gravity that results from the coupling of the Earth's gravity and magnetic forces can be varied. The stability diagram of the instability is obtained. The experiments show a good agreement with an inviscid model [Fluid Dyn. 21 849 (1987)], irrespective of the gravity level. It is observed in the experiments that the height of the frozen waves varies weakly with temperature and increases with a decrease in the gravity level, according to a power law with an exponent of 0.7. It is concluded that the wave height becomes of the order of the cell size as the gravity level is asymptotically decreased to zero. The interface pattern thus appears as a bandlike pattern of alternate liquid and vapor phases, a puzzling phenomenon that was observed with CO2 and H2 near their critical point in weightlessness [Acta Astron. 61 1002 (2007); Europhys. Lett. 86 16003 (2009)].

GPS-TEC Observation of Gravity Waves Generated in the Ionosphere During 21 August 2017 Total Solar Eclipse

Science.gov (United States)

Nayak, Chinmaya; Yiǧit, Erdal

2018-01-01

The present work investigates ionospheric effects of the 21 August 2017 total solar eclipse, particularly targeting eclipse-generated gravity waves in the ionosphere. Ionospheric total electron content (TEC) derived from Global Positioning System (GPS) data obtained from a number of stations located both along and across the path of eclipse totality has been utilized for this purpose. Distinct gravity wave-like signatures with wave periods around 20-90 min (with dominant peak at 25-30 min wave period) have been observed at all locations both in the path of totality and away from it. The observed gravity waves are more intense at locations closer to the path of totality, and the wave amplitudes decrease gradually with increasing distance from the path of totality. Our result highlights the manifestation of eclipse-generated waves in the variability of the terrestrial ionosphere.

Thermal infrared sounding observations of lower atmospheric variances at Mars and their implications for gravity wave activity: a preliminary examination

Science.gov (United States)

Heavens, N. G.

2017-12-01

It has been recognized for over two decades that the mesoscale statistical variance observed by Earth-observing satellites at temperature-sensitive frequencies above the instrumental noise floor is a measure of gravity wave activity. These types of observation have been made by a variety of satellite instruments have been an important validation tool for gravity wave parameterizations in global and mesoscale models. At Mars, the importance of topographic and non-topographic sources of gravity waves for the general circulation is now widely recognized and the target of recent modeling efforts. However, despite several ingenious studies, gravity wave activity near hypothetical lower atmospheric sources has been poorly and unsystematically characterized, partly because of the difficulty of separating the gravity wave activity from baroclinic wave activity and the thermal tides. Here will be presented a preliminary analysis of calibrated radiance variance at 15.4 microns (635-665 cm-1) from nadir, off-nadir, and limb observations by the Mars Climate Sounder on board Mars Reconnaissance Orbiter. The overarching methodology follows Wu and Waters (1996, 1997). Nadir, off-nadir, and lowest detector limb observations should sample variability with vertical weighting functions centered high in the lower atmosphere (20-30 km altitude) and full width half maximum (FWHM) 20 km but be sensitive to gravity waves with different horizontal wavelengths and slightly different vertical wavelengths. This work is supported by NASA's Mars Data Analysis Program (NNX14AM32G). References Wu, D.L. and J.W. Waters, 1996, Satellite observations of atmospheric variances: A possible indication of gravity waves, GRL, 23, 3631-3634. Wu D.L. and J.W. Waters, 1997, Observations of Gravity Waves with the UARS Microwave Limb Sounder. In: Hamilton K. (eds) Gravity Wave Processes. NATO ASI Series (Series I: Environmental Change), vol 50. Springer, Berlin, Heidelberg.

Sediment gravity flows triggered by remotely generated earthquake waves

Science.gov (United States)

Johnson, H. Paul; Gomberg, Joan S.; Hautala, Susan L.; Salmi, Marie S.

2017-06-01

Recent great earthquakes and tsunamis around the world have heightened awareness of the inevitability of similar events occurring within the Cascadia Subduction Zone of the Pacific Northwest. We analyzed seafloor temperature, pressure, and seismic signals, and video stills of sediment-enveloped instruments recorded during the 2011-2015 Cascadia Initiative experiment, and seafloor morphology. Our results led us to suggest that thick accretionary prism sediments amplified and extended seismic wave durations from the 11 April 2012 Mw8.6 Indian Ocean earthquake, located more than 13,500 km away. These waves triggered a sequence of small slope failures on the Cascadia margin that led to sediment gravity flows culminating in turbidity currents. Previous studies have related the triggering of sediment-laden gravity flows and turbidite deposition to local earthquakes, but this is the first study in which the originating seismic event is extremely distant (> 10,000 km). The possibility of remotely triggered slope failures that generate sediment-laden gravity flows should be considered in inferences of recurrence intervals of past great Cascadia earthquakes from turbidite sequences. Future similar studies may provide new understanding of submarine slope failures and turbidity currents and the hazards they pose to seafloor infrastructure and tsunami generation in regions both with and without local earthquakes.

Investigating Gravity Waves in Polar Mesospheric Clouds Using Tomographic Reconstructions of AIM Satellite Imagery

Science.gov (United States)

Hart, V. P.; Taylor, M. J.; Doyle, T. E.; Zhao, Y.; Pautet, P.-D.; Carruth, B. L.; Rusch, D. W.; Russell, J. M.

2018-01-01

This research presents the first application of tomographic techniques for investigating gravity wave structures in polar mesospheric clouds (PMCs) imaged by the Cloud Imaging and Particle Size instrument on the NASA AIM satellite. Albedo data comprising consecutive PMC scenes were used to tomographically reconstruct a 3-D layer using the Partially Constrained Algebraic Reconstruction Technique algorithm and a previously developed "fanning" technique. For this pilot study, a large region (760 × 148 km) of the PMC layer (altitude 83 km) was sampled with a 2 km horizontal resolution, and an intensity weighted centroid technique was developed to create novel 2-D surface maps, characterizing the individual gravity waves as well as their altitude variability. Spectral analysis of seven selected wave events observed during the Northern Hemisphere 2007 PMC season exhibited dominant horizontal wavelengths of 60-90 km, consistent with previous studies. These tomographic analyses have enabled a broad range of new investigations. For example, a clear spatial anticorrelation was observed between the PMC albedo and wave-induced altitude changes, with higher-albedo structures aligning well with wave troughs, while low-intensity regions aligned with wave crests. This result appears to be consistent with current theories of PMC development in the mesopause region. This new tomographic imaging technique also provides valuable wave amplitude information enabling further mesospheric gravity wave investigations, including quantitative analysis of their hemispheric and interannual characteristics and variations.

QBO Modulation of the Mesopause Gravity Wave Momentum Flux over Tierra del Fuego

Science.gov (United States)

De Wit, R. J.; Janches, D.; Fritts, D. C.; Hibbins, R. E.

2016-01-01

The interannual variability of the mesosphere and lower thermosphere (MLT) gravity wave momentum flux over southern mid latitudes (53.7degS) has been studied using more than 7 years of meteor radar observations at Ro Grande, Argentina. A modulation, with periods similar to that of the equatorial stratospheric quasi-biennial oscillation (QBO), is observed in the vertical flux of zonal as well as meridional momentum. The QBO signal is largest in the zonal component during summer and is in phase with the stratospheric QBO at 50 hPa (approx. 21 km). The relation between the stratospheric QBO and the QBO modulation in the MLT gravity wave forcing (derived from the divergence of the momentum flux) was found to be consistent with that expected from the Holton-Tan effect coupled to the interhemispheric coupling mechanism. These results provide the first observational support for the existence of the midlatitude gravity wave forcing anomalies as hypothesized in the interhemispheric coupling mechanism.

Linear and Nonlinear Electrostatic Waves in Unmagnetized Dusty Plasmas

International Nuclear Information System (INIS)

Mamun, A. A.; Shukla, P. K.

2010-01-01

A rigorous and systematic theoretical study has been made of linear and nonlinear electrostatic waves propagating in unmagnetized dusty plasmas. The basic features of linear and nonlinear electrostatic waves (particularly, dust-ion-acoustic and dust-acoustic waves) for different space and laboratory dusty plasma conditions are described. The experimental observations of such linear and nonlinear features of dust-ion-acoustic and dust-acoustic waves are briefly discussed.

The Effect of Aerosol on Gravity Wave Characteristics above the Boundary Layer over a Tropical Location

Science.gov (United States)

Rakshit, G.; Jana, S.; Maitra, A.

2017-12-01

The perturbations of temperature profile over a location give an estimate of the potential energy of gravity waves propagating through the atmosphere. Disturbances in the lower atmosphere due to tropical deep convection, orographic effects and various atmospheric disturbances generates of gravity waves. The present study investigates the gravity wave energy estimated from fluctuations in temperature profiles over the tropical location Kolkata (22°34' N, 88°22' E). Gravity waves are most intense during the pre-monsoon period (March-June) at the present location, the potential energy having high values above the boundary layer (2-4 km) as observed from radiosonde profiles. An increase in temperature perturbation, due to high ambient temperature in the presence of heat absorbing aerosols, causes an enhancement in potential energy. As the present study location is an urban metropolitan city experiencing high level of pollution, pollutant aerosols can go much above the normal boundary layer during daytime due to convection causing an extended boundary layer. The Aerosol Index (AAI) obtained from Global Ozone Monitoring Experiment-2 (GOME-2) on MetOp-A platform at 340 nm and 380 nm confirms the presence of absorbing aerosol particles over the present location. The Hysplit back trajectory analysis shows that the aerosol particles at those heights are of local origin and are responsible for depleting liquid water content due to cloud burning. The aerosol extinction coefficient obtained from CALIPSO data exhibits an increasing trend during 2006-2016 accompanied by a similar pattern of gravity wave energy. Thus the absorbing aerosols have a significant role in increasing the potential energy of gravity wave at an urban location in the tropical region.

Active Absorption of Irregular Gravity Waves in BEM-Models

DEFF Research Database (Denmark)

Brorsen, Michael; Frigaard, Peter

1992-01-01

The boundary element method is applied to the computation of irregular gravity waves. The boundary conditions at the open boundaries are obtained by a digital filtering technique, where the surface elevations in front of the open boundary are filtered numerically yielding the velocity to be presc...... to be prescribed at the boundary. By numerical examples it is shown that well designed filters can reduce the wave reflection to a few per cent over a frequency range corresponding to a Jonswap spectrum....

Thermal effect on gravity waves in a compressible liquid layer over a ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

Abstract. This paper deals with the effect of temperature on gravity waves in a compressible liquid layer over a solid half-space. It has been assumed that the liquid layer is under the action of gravity, while the solid half-space is under the influence of initial compressive hydrostatic stress. When the temperature of the.

Gravity waves as a probe of the Hubble expansion rate during an electroweak scale phase transition

International Nuclear Information System (INIS)

Chung, Daniel J. H.; Zhou Peng

2010-01-01

Just as big bang nucleosynthesis allows us to probe the expansion rate when the temperature of the Universe was around 1 MeV, the measurement of gravity waves from electroweak scale first order phase transitions may allow us to probe the expansion rate when the temperature of the Universe was at the electroweak scale. We compute the simple transformation rule for the gravity wave spectrum under the scaling transformation of the Hubble expansion rate. We then apply this directly to the scenario of quintessence kination domination and show how gravity wave spectra would shift relative to Laser Interferometer Space Antenna and Big Bang Observer projected sensitivities.

Universal power law of the gravity wave manifestation in the AIM CIPS polar mesospheric cloud images

Science.gov (United States)

Rong, Pingping; Yue, Jia; Russell, James M., III; Siskind, David E.; Randall, Cora E.

2018-01-01

We aim to extract a universal law that governs the gravity wave manifestation in polar mesospheric clouds (PMCs). Gravity wave morphology and the clarity level of display vary throughout the wave population manifested by the PMC albedo data. Higher clarity refers to more distinct exhibition of the features, which often correspond to larger variances and a better-organized nature. A gravity wave tracking algorithm based on the continuous Morlet wavelet transform is applied to the PMC albedo data at 83 km altitude taken by the Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument to obtain a large ensemble of the gravity wave detections. The horizontal wavelengths in the range of ˜ 20-60 km are the focus of the study. It shows that the albedo (wave) power statistically increases as the background gets brighter. We resample the wave detections to conform to a normal distribution to examine the wave morphology and display clarity beyond the cloud brightness impact. Sample cases are selected at the two tails and the peak of the normal distribution to represent the full set of wave detections. For these cases the albedo power spectra follow exponential decay toward smaller scales. The high-albedo-power category has the most rapid decay (i.e., exponent = -3.2) and corresponds to the most distinct wave display. The wave display becomes increasingly blurrier for the medium- and low-power categories, which hold the monotonically decreasing spectral exponents of -2.9 and -2.5, respectively. The majority of waves are straight waves whose clarity levels can collapse between the different brightness levels, but in the brighter background the wave signatures seem to exhibit mildly turbulent-like behavior.

Thermal effect on gravity waves in a compressible liquid layer over a ...

Indian Academy of Sciences (India)

This paper deals with the effect of temperature on gravity waves in a compressible liquid layer over a solid half-space. It has been assumed that the liquid layer is under the action of gravity, while the solid half-space is under the influence of initial compressive hydrostatic stress. When the temperature of the half-space is ...

Constrained non-linear waves for offshore wind turbine design

International Nuclear Information System (INIS)

Rainey, P J; Camp, T R

2007-01-01

Advancements have been made in the modelling of extreme wave loading in the offshore environment. We give an overview of wave models used at present, and their relative merits. We describe a method for embedding existing non-linear solutions for large, regular wave kinematics into linear, irregular seas. Although similar methods have been used before, the new technique is shown to offer advances in computational practicality, repeatability, and accuracy. NewWave theory has been used to constrain the linear simulation, allowing best possible fit with the large non-linear wave. GH Bladed was used to compare the effect of these models on a generic 5 MW turbine mounted on a tripod support structure

Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

International Nuclear Information System (INIS)

Sugimoto, Norihiko

2015-01-01

Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves

Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

Energy Technology Data Exchange (ETDEWEB)

Sugimoto, Norihiko, E-mail: nori@phys-h.keio.ac.jp [Department of Physics, Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8521 (Japan)

2015-12-15

Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves.

influence of gravity

Directory of Open Access Journals (Sweden)

Animesh Mukherjee

1991-01-01

Full Text Available Based upon Biot's [1965] theory of initial stresses of hydrostatic nature produced by the effect of gravity, a study is made of surface waves in higher order visco-elastic media under the influence of gravity. The equation for the wave velocity of Stonely waves in the presence of viscous and gravitational effects is obtained. This is followed by particular cases of surface waves including Rayleigh waves and Love waves in the presence of viscous and gravity effects. In all cases the wave-velocity equations are found to be in perfect agreement with the corresponding classical results when the effects of gravity and viscosity are neglected.

Gravitational field of static p -branes in linearized ghost-free gravity

Science.gov (United States)

Boos, Jens; Frolov, Valeri P.; Zelnikov, Andrei

2018-04-01

We study the gravitational field of static p -branes in D -dimensional Minkowski space in the framework of linearized ghost-free (GF) gravity. The concrete models of GF gravity we consider are parametrized by the nonlocal form factors exp (-□/μ2) and exp (□2/μ4) , where μ-1 is the scale of nonlocality. We show that the singular behavior of the gravitational field of p -branes in general relativity is cured by short-range modifications introduced by the nonlocalities, and we derive exact expressions of the regularized gravitational fields, whose geometry can be written as a warped metric. For large distances compared to the scale of nonlocality, μ r →∞ , our solutions approach those found in linearized general relativity.

Cosmic Tsunamis in Modified Gravity: Disruption of Screening Mechanisms from Scalar Waves.

Science.gov (United States)

Hagala, R; Llinares, C; Mota, D F

2017-03-10

Extending general relativity by adding extra degrees of freedom is a popular approach for explaining the accelerated expansion of the Universe and to build high energy completions of the theory of gravity. The presence of such new degrees of freedom is, however, tightly constrained from several observations and experiments that aim to test general relativity in a wide range of scales. The viability of a given modified theory of gravity, therefore, strongly depends on the existence of a screening mechanism that suppresses the extra degrees of freedom. We perform simulations, and find that waves propagating in the new degrees of freedom can significantly impact the efficiency of some screening mechanisms, thereby threatening the viability of these modified gravity theories. Specifically, we show that the waves produced in the symmetron model can increase the amplitude of the fifth force and the parametrized post Newtonian parameters by several orders of magnitude.

Statistical comparisons of gravity wave features derived from OH airglow and SABER data

Science.gov (United States)

Gelinas, L. J.; Hecht, J. H.; Walterscheid, R. L.

2017-12-01

The Aerospace Corporation's near-IR camera (ANI), deployed at Andes Lidar Observatory (ALO), Cerro Pachon Chile (30S,70W) since 2010, images the bright OH Meinel (4,2) airglow band. The imager provides detailed observations of gravity waves and instability dynamics, as described by Hecht et al. (2014). The camera employs a wide-angle lens that views a 73 by 73 degree region of the sky, approximately 120 km x 120 km at 85 km altitude. Image cadence of 30s allows for detailed spectral analysis of the horizontal components of wave features, including the evolution and decay of instability features. The SABER instrument on NASA's TIMED spacecraft provides remote soundings of kinetic temperature profiles from the lower stratosphere to the lower thermosphere. Horizontal and vertical filtering techniques allow SABER temperatures to be analyzed for gravity wave variances [Walterscheid and Christensen, 2016]. Here we compare the statistical characteristics of horizontal wave spectra, derived from airglow imagery, with vertical wave variances derived from SABER temperature profiles. The analysis is performed for a period of strong mountain wave activity over the Andes spanning the period between June and September 2012. Hecht, J. H., et al. (2014), The life cycle of instability features measured from the Andes Lidar Observatory over Cerro Pachon on March 24, 2012, J. Geophys. Res. Atmos., 119, 8872-8898, doi:10.1002/2014JD021726. Walterscheid, R. L., and A. B. Christensen (2016), Low-latitude gravity wave variances in the mesosphere and lower thermosphere derived from SABER temperature observation and compared with model simulation of waves generated by deep tropical convection, J. Geophys. Res. Atmos., 121, 11,900-11,912, doi:10.1002/2016JD024843.

Atmosphere-ionosphere coupling from convectively generated gravity waves

Science.gov (United States)

Azeem, Irfan; Barlage, Michael

2018-04-01

Ionospheric variability impacts operational performances of a variety of technological systems, such as HF communication, Global Positioning System (GPS) navigation, and radar surveillance. The ionosphere is not only perturbed by geomagnetic inputs but is also influenced by atmospheric tides and other wave disturbances propagating from the troposphere to high altitudes. Atmospheric Gravity Waves (AGWs) excited by meteorological sources are one of the largest sources of mesoscale variability in the ionosphere. In this paper, Total Electron Content (TEC) data from networks of GPS receivers in the United States are analyzed to investigate AGWs in the ionosphere generated by convective thunderstorms. Two case studies of convectively generated gravity waves are presented. On April 4, 2014 two distinct large convective systems in Texas and Arkansas generated two sets of concentric AGWs that were observed in the ionosphere as Traveling Ionospheric Disturbances (TIDs). The period of the observed TIDs was 20.8 min, the horizontal wavelength was 182.4 km, and the horizontal phase speed was 146.4 m/s. The second case study shows TIDs generated from an extended squall line on December 23, 2015 stretching from the Gulf of Mexico to the Great Lakes in North America. Unlike the concentric wave features seen in the first case study, the extended squall line generated TIDs, which exhibited almost plane-parallel phase fronts. The TID period was 20.1 min, its horizontal wavelength was 209.6 km, and the horizontal phase speed was 180.1 m/s. The AGWs generated by both of these meteorological events have large vertical wavelength (>100 km), which are larger than the F2 layer thickness, thus allowing them to be discernible in the TEC dataset.

Linear interaction of gravitational waves

International Nuclear Information System (INIS)

Ciubotariu, C.D.

1992-01-01

Starting with the linearized Einstein equations written in the same form as Maxwell equations, a damping term is found in the wave equation. The analogy with the propagation of the electromagnetic wave in ohmic media is obvious if we introduce an 'ohmic relation' for gravitational interaction. The possibility of the amplification of gravitational waves by a suitable choice of the velocity field of a dust ('dust with negative viscosity'), for example by the use of the free-electron laser principle, is indicated. (Author)

Detection of large-scale concentric gravity waves from a Chinese airglow imager network

Science.gov (United States)

Lai, Chang; Yue, Jia; Xu, Jiyao; Yuan, Wei; Li, Qinzeng; Liu, Xiao

2018-06-01

Concentric gravity waves (CGWs) contain a broad spectrum of horizontal wavelengths and periods due to their instantaneous localized sources (e.g., deep convection, volcanic eruptions, or earthquake, etc.). However, it is difficult to observe large-scale gravity waves of >100 km wavelength from the ground for the limited field of view of a single camera and local bad weather. Previously, complete large-scale CGW imagery could only be captured by satellite observations. In the present study, we developed a novel method that uses assembling separate images and applying low-pass filtering to obtain temporal and spatial information about complete large-scale CGWs from a network of all-sky airglow imagers. Coordinated observations from five all-sky airglow imagers in Northern China were assembled and processed to study large-scale CGWs over a wide area (1800 km × 1 400 km), focusing on the same two CGW events as Xu et al. (2015). Our algorithms yielded images of large-scale CGWs by filtering out the small-scale CGWs. The wavelengths, wave speeds, and periods of CGWs were measured from a sequence of consecutive assembled images. Overall, the assembling and low-pass filtering algorithms can expand the airglow imager network to its full capacity regarding the detection of large-scale gravity waves.

Effects of gravity and planetary waves on the lower ionosphere as obtained from radio wave absorption measurements

Czech Academy of Sciences Publication Activity Database

Laštovička, Jan

2001-01-01

Roč. 26, 6, Part C (2001), s. 381-386 ISSN 1464-1917 R&D Projects: GA AV ČR IBS3012007; GA AV ČR IAA3042102; GA MŠk OC 271.10 Institutional research plan: CEZ:AV0Z3042911 Keywords : planetary wave * gravity wave * lower ionosphere Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.399, year: 2001

Long-term MST radar observations of vertical wave number spectra of gravity waves in the tropical troposphere over Gadanki (13.5° N, 79.2° E: comparison with model spectra

Directory of Open Access Journals (Sweden)

S. Vijaya Bhaskara Rao

2008-06-01

Full Text Available The potential utility of Mesosphere-Stratosphere-Troposphere (MST radar measurements of zonal, meridional and vertical winds for divulging the gravity wave vertical wave number spectra is discussed. The data collected during the years 1995–2004 are used to obtain the mean vertical wave number spectra of gravity wave kinetic energy in the tropical troposphere over Gadanki (13.5° N, 79.2° E. First, the climatology of 3-dimensional wind components is developed using ten years of radar observations, for the first time, over this latitude. This climatology brought out the salient features of background tropospheric winds over Gadanki. Further, using the second order polynomial fit as background, the day-to-day wind anomalies are estimated. These wind anomalies in the 4–14 km height regions are used to estimate the profiles of zonal, meridional and vertical kinetic energy per unit mass, which are then used to estimate the height profile of total kinetic energy. Finally, the height profiles of total kinetic energy are subjected to Fourier analysis to obtain the monthly mean vertical wave number spectra of gravity wave kinetic energy. The monthly mean vertical wave number spectra are then compared with a saturation spectrum predicted by gravity wave saturation theory. A slope of 5/3 is used for the model gravity wave spectrum estimation. In general, the agreement is good during all the months. However, it is noticed that the model spectrum overestimates the PSD at lower vertical wave numbers and underestimates it at higher vertical wave numbers, which is consistently observed during all the months. The observed discrepancies are attributed to the differences in the slopes of theoretical and observed gravity wave spectra. The slopes of the observed vertical wave number spectra are estimated and compared with the model spectrum slope, which are in good agreement. The estimated slopes of the observed monthly vertical wave number spectra are in the

Surface gravity waves and their acoustic signatures, 1-30 Hz, on the mid-Pacific sea floor.

Science.gov (United States)

Farrell, W E; Munk, Walter

2013-10-01

In 1999, Duennebier et al. deployed a hydrophone and geophone below the conjugate depth in the abyssal Pacific, midway between Hawaii and California. Real time data were transmitted for 3 yr over an abandoned ATT cable. These data have been analyzed in the frequency band 1 to 30 Hz. Between 1 and 6 Hz, the bottom data are interpreted as acoustic radiation from surface gravity waves, an extension to higher frequencies of a non-linear mechanism proposed by Longuet-Higgins in 1950 to explain microseisms. The inferred surface wave spectrum for wave lengths between 6 m and 17 cm is saturated (wind-independent) and roughly consistent with the traditional Phillips κ(-4) wave number spectrum. Shorter ocean waves have a strong wind dependence and a less steep wave number dependence. Similar features are found in the bottom record between 6 and 30 Hz. But this leads to an enigma: The derived surface spectrum inferred from the Longuet-Higgins mechanism with conventional assumptions for the dispersion relation is associated with mean square slopes that greatly exceed those derived from glitter. Regardless of the generation mechanism, the measured bottom intensities between 10 and 30 Hz are well below minimum noise standards reported in the literature.

Exact piecewise flat gravitational waves

NARCIS (Netherlands)

van de Meent, M.

2011-01-01

We generalize our previous linear result (van de Meent 2011 Class. Quantum Grav 28 075005) in obtaining gravitational waves from our piecewise flat model for gravity in 3+1 dimensions to exact piecewise flat configurations describing exact planar gravitational waves. We show explicitly how to

Sea surface temperature as a proxy for convective gravity wave excitation: a study based on global gravity wave observations in the middle atmosphere

Directory of Open Access Journals (Sweden)

J. Y. Jia

2014-11-01

Full Text Available Absolute values of gravity wave momentum flux (GWMF deduced from satellite measurements by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER instrument and the High Resolution Dynamics Limb Sounder (HIRDLS are correlated with sea surface temperature (SST with the aim of identifying those oceanic regions for which convection is a major source of gravity waves (GWs. Our study identifies those latitude bands where high correlation coefficients indicate convective excitation with confidence. This is based on a global ray-tracing simulation, which is used to delineate the source and wind-filtering effects. Convective GWs are identified at the eastern coasts of the continents and over the warm water regions formed by the warm ocean currents, in particular the Gulf Stream and the Kuroshio. Potential contributions of tropical cyclones to the excitation of the GWs are discussed. Convective excitation can be identified well into the mid-mesosphere. In propagating upward, the centers of GWMF formed by convection shift poleward. Some indications of the main forcing regions are even shown for the upper mesosphere/lower thermosphere (MLT.

Gravity waves, Tides and Planetary wave characteristics revealed by network of MLT radars over Indian region

Science.gov (United States)

Venkat Ratnam, Madineni; Karanam, Kishore Kumar; Sunkara, Eswaraiah; Vijaya Bhaskara Rao, S.; Subrahmanyam, K. V.; Ramanjaneyulu, L.

2016-07-01

Mesosphere and Lower Thermosphere (MLT) mean winds, gravity waves, tidal and planetary wave characteristics are investigated using two years (2013-2015) of advanced meteor radar installed at Tirupathi (13.63oN, 79.4oE), India. The observations reveal the presence of high frequency gravity waves (30-120 minutes), atmospheric tides (diurnal, semi-diurnal and terr-diurnal) along with long period oscillations in both zonal and meridional winds. Background mean zonal winds show clear semi-annual oscillation in the mesosphere, whereas meridional winds are characterized by annual oscillation as expected. Diurnal tide amplitudes are significantly larger (60-80 m/s) than semi-diurnal (10-20 m/s) and terr-diurnal (5-8 m/s) tides and larger in meridional than zonal winds. The measured meridional components are in good agreement with Global Scale Wave Model (GSWM-09) predictions than zonal up to ~90 km in all the seasons, except fall equinox. Diurnal tidal phase matches well than the amplitudes between observations and model predictions. However, no similarity is being found in the semi-diurnal tides between observations and model. The measurements are further compared with nearby Thumba meteor radar (8.5oN, 77oE) observations. Some differences do exist between the measurements from Tirupati and Thumba meteor radar and model outputs at greater heights and the possible reasons are discussed. SVU meteor radar observations clearly showed the dominance of well-known ultra-fast kelvin waves (3.5 days), 5-8 day, 16 day, 27 day, and 30-40 day oscillations. Due to higher meteor count extending up to 110 km, we could investigate the variability of these PWs and oscillations covering wider range (70-110 km) for the first time. Significant change above 100 km is noticed in all the above mentioned PW activity and oscillations. We also used ERA-Interim reanalysis data sets available at 0.125x0.125 degree grids for investigating the characteristics of these PW right from surface to 1 h

Acoustic-gravity nonlinear structures

Directory of Open Access Journals (Sweden)

D. Jovanović

2002-01-01

Full Text Available A catalogue of nonlinear vortex structures associated with acoustic-gravity perturbations in the Earth's atmosphere is presented. Besides the previously known Kelvin-Stewart cat's eyes, dipolar and tripolar structures, new solutions having the form of a row of counter-rotating vortices, and several weakly two-dimensional vortex chains are given. The existence conditions for these nonlinear structures are discussed with respect to the presence of inhomogeneities of the shear flows. The mode-coupling mechanism for the nonlinear generation of shear flows in the presence of linearly unstable acoustic-gravity waves, possibly also leading to intermittency and chaos, is presented.

Constraint on reconstructed f(R) gravity models from gravitational waves

Science.gov (United States)

Lee, Seokcheon

2018-06-01

The gravitational wave (GW) detection of a binary neutron star inspiral made by the Advanced LIGO and Advanced Virgo paves the unprecedented way for multi-messenger observations. The propagation speed of this GW can be scrutinized by comparing the arrival times between GW and neutrinos or photons. It provides the constraint on the mass of the graviton. f(R) gravity theories have the habitual non-zero mass gravitons in addition to usual massless ones. Previously, we show that the model independent f(R) gravity theories can be constructed from the both background evolution and the matter growth with one undetermined parameter. We show that this parameter can be constrained from the graviton mass bound obtained from GW detection. Thus, the GW detection provides the invaluable constraint on the validity of f(R) gravity theories.

Atmospheric gravity waves in the Red Sea: a new hotspot

KAUST Repository

Magalhaes, J. M.; Araú jo, I. B.; da Silva, J. C. B.; Grimshaw, R. H. J.; Davis, K.; Pineda, J.

2011-01-01

The region of the Middle East around the Red Sea (between 32° E and 44° E longitude and 12° N and 28° N latitude) is a currently undocumented hotspot for atmospheric gravity waves (AGWs). Satellite imagery shows evidence that this region is prone

Testing effective quantum gravity with gravitational waves from extreme mass ratio inspirals

International Nuclear Information System (INIS)

Yunes, N; Sopuerta, C F

2010-01-01

Testing deviation of GR is one of the main goals of the proposed Laser Interferometer Space Antenna. For the first time, we consistently compute the generation of gravitational waves from extreme-mass ratio inspirals (stellar compact objects into supermassive black holes) in a well-motivated alternative theory of gravity, that to date remains weakly constrained by double binary pulsar observations. The theory we concentrate on is Chern-Simons (CS) modified gravity, a 4-D, effective theory that is motivated both from string theory and loop-quantum gravity, and which enhances the Einstein-Hilbert action through the addition of a dynamical scalar field and the parity-violating Pontryagin density. We show that although point particles continue to follow geodesics in the modified theory, the background about which they inspiral is a modification to the Kerr metric, which imprints a CS correction on the gravitational waves emitted. CS modified gravitational waves are sufficiently different from the General Relativistic expectation that they lead to significant dephasing after 3 weeks of evolution, but such dephasing will probably not prevent detection of these signals, but instead lead to a systematic error in the determination of parameters. We end with a study of radiation-reaction in the modified theory and show that, to leading-order, energy-momentum emission is not CS modified, except possibly for the subdominant effect of scalar-field emission. The inclusion of radiation-reaction will allow for tests of CS modified gravity with space-borne detectors that might be two orders of magnitude larger than current binary pulsar bounds.

Effect of small floating disks on the propagation of gravity waves

Energy Technology Data Exchange (ETDEWEB)

Santi, F De; Olla, P, E-mail: olla@dsf.unica.it [ISAC-CNR, Sez. Cagliari, I-09042 Monserrato (Italy)

2017-04-15

A dispersion relation for gravity waves in water covered by disk-like impurities embedded in a viscous matrix is derived. The macroscopic equations are obtained by ensemble-averaging the fluid equations at the disk scale in the asymptotic limit of long waves and low disk surface fraction. Various regimes are identified depending on the disk radii and the thickness and viscosity of the top layer. Semi-quantitative analysis in the close-packing regime suggests dramatic modification of the dynamics, with orders of magnitude increase in wave damping and wave dispersion. A simplified model working in this regime is proposed. Possible applications to wave propagation in an ice-covered ocean are discussed and comparison with field data is provided. (paper)

Internal gravity waves in Titan's atmosphere observed by Voyager radio occultation

Science.gov (United States)

Hinson, D. P.; Tyler, G. L.

1983-01-01

The radio scintillations caused by scattering from small-scale irregularities in Titan's neutral atmosphere during a radio occultation of Voyager 1 by Titan are investigated. Intensity and frequency fluctuations occurred on time scales from about 0.1 to 1.0 sec at 3.6 and 13 cm wavelengths whenever the radio path passed within 90 km of the surface, indicating the presence of variations in refractivity on length scales from a few hundred meters to a few kilometers. Above 25 km, the altitude profile of intensity scintillations closely agrees with the predictions of a simple theory based on the characteristics of internal gravity waves propagating with little or no attenuation through the vertical stratification in Titan's atmosphere. These observations support a hypothesis of stratospheric gravity waves, possibly driven by a cloud-free convective region in the lowest few kilometers of the stratosphere.

Cosmological large-scale structures beyond linear theory in modified gravity

Energy Technology Data Exchange (ETDEWEB)

Bernardeau, Francis; Brax, Philippe, E-mail: francis.bernardeau@cea.fr, E-mail: philippe.brax@cea.fr [CEA, Institut de Physique Théorique, 91191 Gif-sur-Yvette Cédex (France)

2011-06-01

We consider the effect of modified gravity on the growth of large-scale structures at second order in perturbation theory. We show that modified gravity models changing the linear growth rate of fluctuations are also bound to change, although mildly, the mode coupling amplitude in the density and reduced velocity fields. We present explicit formulae which describe this effect. We then focus on models of modified gravity involving a scalar field coupled to matter, in particular chameleons and dilatons, where it is shown that there exists a transition scale around which the existence of an extra scalar degree of freedom induces significant changes in the coupling properties of the cosmic fields. We obtain the amplitude of this effect for realistic dilaton models at the tree-order level for the bispectrum, finding them to be comparable in amplitude to those obtained in the DGP and f(R) models.

Seasonal and height variation of gravity wave activities observed by a meteor radar at King Sejong Station (62°S, 57°W), Antarctica

Science.gov (United States)

Kim, Y.; Lee, C.; Kim, J.; Choi, J.; Jee, G.

2010-12-01

We have analyzed wind data from individual meteor echoes detected by a meteor radar at King Sejong Station, Antarctica to measure gravity wave activity in the mesopause region. Wind data in the meteor altitudes has been obtained routinely by the meteor radar since its installation in March 2007. The mean variances in the wind data that were filtered for large scale motions (mean winds and tides) can be regarded as the gravity wave activity. Monthly mean gravity wave activities show strong seasonal and height dependences in the altitude range of 80 to 100 km. The gravity wave activities except summer monotonically increase with altitude, which is expected since decreasing atmospheric densities cause wave amplitudes to increase. During summer (Dec. - Feb.) the height profiles of gravity wave activities show a minimum near 90 - 95 km, which may be due to different zonal wind and strong wind shear near 80 - 95 km. Our gravity wave activities are generally stronger than those of the Rothera station, implying sensitive dependency on location. The difference may be related to gravity wave sources in the lower atmosphere near Antarctic vortex.

Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity: stability, ringdown, and gravitational-wave emission

CERN Document Server

Blázquez-Salcedo, Jose Luis

2016-01-01

Gravitational waves emitted by distorted black holes---such as those arising from the coalescence of two neutron stars or black holes---carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory, and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations; (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that...

Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign. Part I. Observations with collocated radars

Energy Technology Data Exchange (ETDEWEB)

Hoffmann, P.; Serafimovich, A.; Peters, D.; Latteck, R. [Leibniz-Inst. fuer Atmosphaerenphysik, Kuehlungsborn (Germany); Dalin, P. [Swedish Inst. of Space Physics, Kiruna (Sweden); Goldberg, R. [NASA/Goddard Space Flight Center, Greenbelt, MD (United States)

2006-07-01

During the MaCWAVE campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andoeya rocket range (ARR) near Andenes and the Swedish rocket range (ESRANGE) near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHP radar in the upper troposphere/ lower stratosphere at Andenes (69.3 N, 16.0 E) and the ESRAD VHP radar near Kiruna (67.9 N, 21.9 E). Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24-26 January 2003 with dominant vertical wavelengths of about 4-5 km as well as with dominant observed periods of about 13-14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of {proportional_to}200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of {proportional_to}5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains. (orig.)

Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign. Part II. Radar investigations and modelling studies

Energy Technology Data Exchange (ETDEWEB)

Serafimovich, A.; Zuelicke, C.; Hoffmann, P.; Peters, D.; Singer, W. [Leibniz-Inst. fuer Atmosphaerenphysik, Kuehlungsborn (Germany); Dalin, P. [Swedish Inst. of Space Physics, Kiruna (Sweden)

2006-07-01

We present an experimental and modelling study of a strong gravity wave event in the upper troposphere/lower stratosphere near the Scandinavian mountain ridge. Continuous VHP radar measurements during the MaCWAVE rocket and ground-based measurement campaign were performed at the Norwegian Andoya rocket range (ARR) near Andenes (69.3 N, 16 E) in January 2003. Detailed gravity wave investigations based on PSU/NCAR fifth-generation mesoscale model (MM5) data have been used for comparison with experimentally obtained results. The model data show the presence of a mountain wave and of an inertia gravity wave generated by a jet streak near the tropopause region. Temporal and spatial dependencies of jet induced inertia gravity waves with dominant observed periods of about 13 h and vertical wavelengths of {proportional_to}4.5-5 km are investigated with wavelet transform applied on radar measurements and model data. The jet induced wave packet is observed to move upstream and downward in the upper troposphere. The model data agree with the experimentally obtained results fairly well. Possible reasons for the observed differences, e.g. in the time of maximum of the wave activity, are discussed. Finally, the vertical fluxes of horizontal momentum are estimated with different methods and provide similar amplitudes. We found indications that the derived positive vertical flux of the horizontal momentum corresponds to the obtained parameters of the jet-induced inertia gravity wave, but only at the periods and heights of the strongest wave activity. (orig.)

The non-Gaussian joint probability density function of slope and elevation for a nonlinear gravity wave field. [in ocean surface

Science.gov (United States)

Huang, N. E.; Long, S. R.; Bliven, L. F.; Tung, C.-C.

1984-01-01

On the basis of the mapping method developed by Huang et al. (1983), an analytic expression for the non-Gaussian joint probability density function of slope and elevation for nonlinear gravity waves is derived. Various conditional and marginal density functions are also obtained through the joint density function. The analytic results are compared with a series of carefully controlled laboratory observations, and good agreement is noted. Furthermore, the laboratory wind wave field observations indicate that the capillary or capillary-gravity waves may not be the dominant components in determining the total roughness of the wave field. Thus, the analytic results, though derived specifically for the gravity waves, may have more general applications.

Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data

Directory of Open Access Journals (Sweden)

N. F. Arnold

1998-10-01

Full Text Available Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.Key words. Ionosphere (ionosphere – atmosphere interactions · Meteorology and atmospheric dynamics (thermospheric dynamics · Radio science (ionospheric propagations

Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data

Directory of Open Access Journals (Sweden)

N. F. Arnold

Full Text Available Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.

Key words. Ionosphere (ionosphere – atmosphere interactions · Meteorology and atmospheric dynamics (thermospheric dynamics · Radio science (ionospheric propagations

Nonlinear internal gravity waves and their interaction with the mean wind

International Nuclear Information System (INIS)

Grimshaw, R.

1975-01-01

The interaction of a wave packet of internal gravity waves with the mean wind is investigated, for the case when there is a region of wind shear and hence a critical level. The principal equations are the Doppler-shifted dispersion relation, the equation for conservation of wave action and the mean momentum equation, in which the mean wind is accelerated by a 'radiation stress' tensor, due to the waves. These equations are integrated numerically to study the behaviour of a wave packet approaching a critical level, where the horizontal phase speed matches the mean wind. The results demonstrate the exchange of energy from the waves to the mean wind in the vicinity of the critical level. The interaction between the waves and the mean wind is also studied in the absence of any initial wind shear. (author)

Linear waves and stability in ideal magnetohydrodynamics

International Nuclear Information System (INIS)

Eckhoff, K.S.

1987-05-01

Linear waves superimposed on an arbitrary basic state in ideal magnetohydrodynamics are studied by an asymptotic expansion valid for short wavelenghts. The theory allows for a gravitational potential, and it may therefore be applied both in astrophysics and in problems related to thermonuclear fusion. The linearized equations for the perturbations of the basic state are found in the form of a symmetric hyperbolic system. This symmetric hyperbolic system is shown to possess characteristics of nonuniform multiplicity, which implies that waves of different types may interact. In particular it is shown that the mass waves, the Alf-n waves, and the slow magnetoacoustic waves will persistently interact in the exceptional case where the local wave number vector is perpendicular to the magnetic field. The equations describing this interaction are found in the form of a weakly coupled hyperbolic system. This weakly coupled hyperbloc system is studied in a number of special cases, and detailed analytic results are obtained for some such cases. The results show that the interaction of the waves may be one of the major causes of instability of the basic state. It seems beyond doubt that the interacting waves contain the physically relevant parts of the waves, which often are referred to as ballooning modes, including Suydam modes and Mercier modes

On the Chemical Mixing Induced by Internal Gravity Waves

Energy Technology Data Exchange (ETDEWEB)

Rogers, T. M. [School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne (United Kingdom); McElwaine, J. N. [Planetary Science Institute, Tucson, AZ 85721 (United States)

2017-10-10

Detailed modeling of stellar evolution requires a better understanding of the (magneto)hydrodynamic processes that mix chemical elements and transport angular momentum. Understanding these processes is crucial if we are to accurately interpret observations of chemical abundance anomalies, surface rotation measurements, and asteroseismic data. Here, we use two-dimensional hydrodynamic simulations of the generation and propagation of internal gravity waves in an intermediate-mass star to measure the chemical mixing induced by these waves. We show that such mixing can generally be treated as a diffusive process. We then show that the local diffusion coefficient does not depend on the local fluid velocity, but rather on the wave amplitude. We then use these findings to provide a simple parameterization for this diffusion, which can be incorporated into stellar evolution codes and tested against observations.

Horizon effects with surface waves on moving water

Energy Technology Data Exchange (ETDEWEB)

Rousseaux, Germain; Maissa, Philippe; Mathis, Christian; Coullet, Pierre [Universite de Nice-Sophia Antipolis, Laboratoire J-A Dieudonne, UMR CNRS-UNS 6621, Parc Valrose, 06108 Nice Cedex 02 (France); Philbin, Thomas G; Leonhardt, Ulf, E-mail: Germain.Rousseaux@unice.f [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom)

2010-09-15

Surface waves on a stationary flow of water are considered in a linear model that includes the surface tension of the fluid. The resulting gravity-capillary waves experience a rich array of horizon effects when propagating against the flow. In some cases, three horizons (points where the group velocity of the wave reverses) exist for waves with a single laboratory frequency. Some of these effects are familiar in fluid mechanics under the name of wave blocking, but other aspects, in particular waves with negative co-moving frequency and the Hawking effect, were overlooked until surface waves were investigated as examples of analogue gravity (Schuetzhold R and Unruh W G 2002 Phys. Rev. D 66 044019). A comprehensive presentation of the various horizon effects for gravity-capillary waves is given, with emphasis on the deep water/ short wavelength case kh>>1, where many analytical results can be derived. A similarity of the state space of the waves to that of a thermodynamic system is pointed out.

Hyperbolicity and constrained evolution in linearized gravity

International Nuclear Information System (INIS)

Matzner, Richard A.

2005-01-01

Solving the 4-d Einstein equations as evolution in time requires solving equations of two types: the four elliptic initial data (constraint) equations, followed by the six second order evolution equations. Analytically the constraint equations remain solved under the action of the evolution, and one approach is to simply monitor them (unconstrained evolution). Since computational solution of differential equations introduces almost inevitable errors, it is clearly 'more correct' to introduce a scheme which actively maintains the constraints by solution (constrained evolution). This has shown promise in computational settings, but the analysis of the resulting mixed elliptic hyperbolic method has not been completely carried out. We present such an analysis for one method of constrained evolution, applied to a simple vacuum system, linearized gravitational waves. We begin with a study of the hyperbolicity of the unconstrained Einstein equations. (Because the study of hyperbolicity deals only with the highest derivative order in the equations, linearization loses no essential details.) We then give explicit analytical construction of the effect of initial data setting and constrained evolution for linearized gravitational waves. While this is clearly a toy model with regard to constrained evolution, certain interesting features are found which have relevance to the full nonlinear Einstein equations

Stratospheric gravity wave activities inferred through the GPS radio occultation technique; Ondas de gravidade na estratosfera terrestre inferida atraves da tecnica de radio ocultacao de GPS

Energy Technology Data Exchange (ETDEWEB)

Wrasse, Cristiano Max [Universidade do Vale do Paraiba (UNIVAP), Instituto de Pesquisa e Desenvolvimento (IPeD), Sao Jose dos Campos, SP (Brazil); Takahashi, Hisao; Fechine, Joaquim; Denardini, Clezio Marcos [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Wickert, Jens, E-mail: cmw@univap.br, E-mail: hisaotak@laser.inpe.br, E-mail: joaquim@laser.inpe.br, E-mail: denardin@dae.inpe.br, E-mail: jens.wickert@gfz-potsdam.de [GeoForschungsZentrum, Potsdam (GFZ), Department of Geodesy and Remote Sensing (Germany)

2007-07-01

Stratospheric gravity wave activities were deduced from GPS radio occultation temperature profiles obtained by CHAMP satellite between 2001 and 2005. Potential energy profiles are used to analyze the gravity wave activity over South America. The results showed an inter-annual variation of the potential energy integrated between 24 and 34 km of altitude. The gravity wave activity is more concentrated around the equatorial region. In order to evaluate the seasonal variation of the gravity wave activity, a mean potential energy was determined over (10 deg N-10 deg S) and (100 deg W-20 deg W). The results showed a lower gravity wave activity during winter time, while during spring time the mean potential energy showed an increase in the wave activity. The results of the mean potential energy also showed that the gravity wave activity in the lower stratosphere exhibits a higher wave activity during 2002 and 2004 and a lower wave activity during 2003 and 2005. (author)

Acoustic–gravity waves during solar eclipses: Detection and characterization using wavelet transforms

Czech Academy of Sciences Publication Activity Database

Šauli, Petra; Roux, S. G.; Abry, P.; Boška, Josef

2007-01-01

Roč. 69, 17-18 (2007), s. 2465-2484 ISSN 1364-6826 R&D Projects: GA ČR GA205/06/1619; GA AV ČR IAA300420504 Grant - others:CNRS(FR) 18098 Institutional research plan: CEZ:AV0Z30420517 Keywords : Acoustic–gravity wave * Vertical ionospheric sounding * F-layer * Wavelet transform * Wave-packet characterization Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.566, year: 2007

Locating the Tohoku-Oki 2011 tsunami source using acoustic-gravity waves

OpenAIRE

Andriamiranto Raveloson; Rainer Kind; Xiaohui Yuan; L. Cerana

2012-01-01

The giant Tohoku-Oki earthquake of 11 March 2011 in offshore Japan did not only generate tsunami waves in the ocean but also infrasound (or acoustic-gravity) waves in the atmosphere. We indentified ultra-long-period signals (>500s) in the recordings of infrasound stations in northeast Asia, the northwest Pacific, and Alaska. Their source was fond close to the earthquake epicenter. Therefore, we conclude that in general, infrasound observations after a large offshore earthquake are evidence th...

Gravitational wave echoes from macroscopic quantum gravity effects

Energy Technology Data Exchange (ETDEWEB)

Barceló, Carlos [Instituto de Astrofísica de Andalucía (IAA-CSIC),Glorieta de la Astronomía, 18008 Granada (Spain); Carballo-Rubio, Raúl [The Cosmology & Gravity Group and the Laboratory for Quantum Gravity & Strings,Department of Mathematics & Applied Mathematics, University of Cape Town,Private Bag, Rondebosch 7701 (South Africa); Garay, Luis J. [Departamento de Física Teórica II,Universidad Complutense de Madrid, 28040 Madrid (Spain); Instituto de Estructura de la Materia (IEM-CSIC),Serrano 121, 28006 Madrid (Spain)

2017-05-10

New theoretical approaches developed in the last years predict that macroscopic quantum gravity effects in black holes should lead to modifications of the gravitational wave signals expected in the framework of classical general relativity, with these modifications being characterized in certain scenarios by the existence of dampened repetitions of the primary signal. Here we use the fact that non-perturbative corrections to the near-horizon external geometry of black holes are necessary for these modifications to exist, in order to classify different proposals and paradigms with respect to this criterion and study in a neat and systematic way their phenomenology. Proposals that lead naturally to the existence of echoes in the late-time ringdown of gravitational wave signals from black hole mergers must share the replacement of black holes by horizonless configurations with a physical surface showing reflective properties in the relevant range of frequencies. On the other hand, proposals or paradigms that restrict quantum gravity effects on the external geometry to be perturbative, such as black hole complementarity or the closely related firewall proposal, do not display echoes. For the sake of completeness we exploit the interplay between the timescales associated with the formation of firewalls and the mechanism behind the existence of echoes in order to conclude that even unconventional distortions of the firewall concept (such as naked firewalls) do not lead to this phenomenon.

Persistent gravity wave coupling from the stratosphere to the MLT versus secondary wave generation in Antarctica

Science.gov (United States)

Zhao, J.; Geraghty, I.; Chu, X.; Vadas, S.; Becker, E.; Harvey, V. L.; Jones, R. M.; Chen, C.; Lu, X.

2017-12-01

After Antarctic persistent gravity waves (GWs) in the Mesosphere and Lower Thermosphere (MLT) were discovered from lidar observations [Chen et al., 2013, 2016], secondary wave generation theory was proposed to explain the source. Here we perform a source investigation of such persistent GWs through analyzing both stratospheric and MLT GWs at McMurdo using temperature measurements (30 - 50 km, year 2011 - 2015) obtained by Fe Boltzmann lidar. In the stratosphere, GW vertical wavelengths (λ) and periods exhibit seasonal cycles with winter maxima and summer minima, which linearly correlated with mean zonal wind velocities. GWs dissipate more in winter than in summer due to larger wave amplitudes. The potential energy density (Ep) are anti-correlated with wind rotation angles but positively correlated with surface and stratospheric winds. Critical level filtering, in-situ generation of GWs, and wave saturation changes play roles in Ep seasonal variations (winter maxima and summer minima). The large increase of Ep from summer to winter possibly results from the decrease in critical level filtering. The gradual variations of Ep from Mar to Oct are likely related both to the increased λ towards winter, allowing larger wave amplitudes before saturation, and to in-situ GW generation via geostrophic adjustment, secondary GW generation. Large Ep occur when McMurdo is inside the jet stream core 5-24º poleward from vortex edge. In winter MLT, the persistent GWs cause larger temperature perturbations (± 30 K, compared to ± 10 K in the stratosphere) with longer λ (23.5 km) and larger vertical phase speeds (1.8 m/s). More waves (95.4%) show downward phase progression compared to the stratospheric GWs (70.4%). Since the inferred horizontal wavelength of stratospheric GWs (350 - 450 km) are much shorter than those of the persistent GWs in the MLT (1000 - 2000 km), the dominant stratospheric GWs are not the direct source of the MLT persistent GWs. Secondary wave generation

Vertical Transport of Momentum by the Inertial-Gravity Internal Waves in a Baroclinic Current

Directory of Open Access Journals (Sweden)

A. A. Slepyshev

2017-08-01

Full Text Available When the internal waves break, they are one of the sources of small-scale turbulence. Small-scale turbulence causes the vertical exchange in the ocean. However, internal waves with regard to the Earth rotation in the presence of vertically inhomogeneous two-dimensional current are able to contribute to the vertical transport. Free inertial-gravity internal waves in a baroclinic current in a boundless basin of a constant depth are considered in the Bussinesq approximation. Boundary value problem of linear approximation for the vertical velocity amplitude of internal waves has complex coefficients when current velocity component, which is transversal to the wave propagation direction, depends on the vertical coordinate (taking into account the rotation of the Earth. Eigenfunction and wave frequency are complex, and it is shown that a weak wave damping takes place. Dispersive relation and wave damping decrement are calculated in the linear approximation. At a fixed wave number damping decrement of the second mode is larger (in the absolute value than the one of the first mode. The equation for vertical velocity amplitude for real profiles of the Brunt – Vaisala frequency and current velocity are numerically solved according to implicit Adams scheme of the third order of accuracy. The dispersive curves of the first two modes do not reach inertial frequency in the low-frequency area due to the effect of critical layers in which wave frequency of the Doppler shift is equal to the inertial one. Termination of the second mode dispersive curves takes place at higher frequency than the one of the first mode. In the second order of the wave amplitude the Stokes drift speed is determined. It is shown that the Stokes drift speed, which is transversal to the wave propagation direction, differs from zero if the transversal component of current velocity depends on the vertical coordinate. In this case, the Stokes drift speed in the second mode is lower than

Parameter spaces for linear and nonlinear whistler-mode waves

International Nuclear Information System (INIS)

Summers, Danny; Tang, Rongxin; Omura, Yoshiharu; Lee, Dong-Hun

2013-01-01

We examine the growth of magnetospheric whistler-mode waves which comprises a linear growth phase followed by a nonlinear growth phase. We construct time-profiles for the wave amplitude that smoothly match at the transition between linear and nonlinear wave growth. This matching procedure can only take place over a limited “matching region” in (N h /N 0 ,A T )-space, where A T is the electron thermal anisotropy, N h is the hot (energetic) electron number density, and N 0 is the cold (background) electron number density. We construct this matching region and determine how the matching wave amplitude varies throughout the region. Further, we specify a boundary in (N h /N 0 ,A T )-space that separates a region where only linear chorus wave growth can occur from the region in which fully nonlinear chorus growth is possible. We expect that this boundary should prove of practical use in performing computationally expensive full-scale particle simulations, and in interpreting experimental wave data

Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign – Part I: Observations with collocated radars

Directory of Open Access Journals (Sweden)

P. Hoffmann

2006-11-01

Full Text Available During the {MaCWAVE} campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andøya Rocket Range (ARR near Andenes and the Swedish Rocket Range (ESRANGE near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHF radar in the upper troposphere/ lower stratosphere at Andenes (69.3° N, 16.0° E and the ESRAD VHF radar near Kiruna (67.9° N, 21.9° E. Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24–26 January 2003 with dominant vertical wavelengths of about 4–5 km as well as with dominant observed periods of about 13–14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of ~200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of ~5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains.

Acoustic Gravity Waves Generated by an Oscillating Ice Sheet in Arctic Zone

Science.gov (United States)

Abdolali, A.; Kadri, U.; Kirby, J. T., Jr.

2016-12-01

We investigate the formation of acoustic-gravity waves due to oscillations of large ice blocks, possibly triggered by atmospheric and ocean currents, ice block shrinkage or storms and ice-quakes.For the idealized case of a homogeneous weakly compressible water bounded at the surface by ice sheet and a rigid bed, the description of the infinite family of acoustic modes is characterized by the water depth h and angular frequency of oscillating ice sheet ω ; The acoustic wave field is governed by the leading mode given by: Nmax=\\floor {(ω h)/(π c)} where c is the sound speed in water and the special brackets represent the floor function (Fig1). Unlike the free-surface setting, the higher acoustic modes might exhibit a larger contribution and therefore all progressive acoustic modes have to be considered.This study focuses on the characteristics of acoustic-gravity waves generated by an oscillating elastic ice sheet in a weakly compressible fluid coupled with a free surface model [Abdolali et al. 2015] representing shrinking ice blocks in realistic sea state, where the randomly oriented ice sheets cause inter modal transition and multidirectional reflections. A theoretical solution and a 3D numerical model have been developed for the study purposes. The model is first validated against the theoretical solution [Kadri, 2016]. To overcome the computational difficulties of 3D models, we derive a depth-integrated equation valid for spatially varying ice sheet thickness and water depth. We show that the generated acoustic-gravity waves contribute significantly to deep ocean currents compared to other mechanisms. In addition, these waves travel at the sound speed in water carrying information on ice sheet motion, providing various implications for ocean monitoring and detection of ice-quakes. Fig1:Snapshots of dynamic pressure given by an oscillating ice sheet; h=4500m, c=1500m/s, semi-length b=10km, ζ =1m, omega=π rad/s. Abdolali, A., Kirby, J. T. and Bellotti, G

Asymptotic expansions for solitary gravity-capillary waves in two and three dimensions

International Nuclear Information System (INIS)

Ablowitz, M J; Haut, T S

2010-01-01

High-order asymptotic series are obtained for gravity-capillary solitary waves, where the first term in the series is the well-known sech 2 solution of the KdV equation. The asymptotic series is used, with nine terms included, to investigate the effects of surface tension on the height and energy of large amplitude waves, and waves close to the solitary version of Stokes' extreme wave. In particular, for surface tension below a critical value, the solitary wave with the maximum energy is obtained. For large surface tension, the series is also used to study the energy related to the solitary waves of depression. Energy considerations suggest that, for large enough surface tension, there are solitary waves that can get close to the fluid bottom. Comparisons are also made with recent experiments.

Gravity waves from the non-renormalizable electroweak vacua phase transition

Energy Technology Data Exchange (ETDEWEB)

Greenwood, Eric [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics; Vaudrevange, Pascal M. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2010-11-15

It is currently believed that the Standard Model is an effective low energy theory which in principle may contain higher dimensional non-renormalizable operators. These operators may modify the standard model Higgs potential in many ways, one of which being the appearance of a second vacuum. For a wide range of parameters, this new vacuum becomes the true vacuum. It is then assumed that our universe is currently sitting in the false vacuum. Thus the usual second-order electroweak phase transition at early times will be followed by a second, first-order phase transition. In cosmology, a first-order phase transition is associated with the production of gravity waves. In this paper we present an analysis of the production of gravitational waves during such a second electroweak phase transition. We find that, for one certain range of parameters, the stochastic background of gravitational waves generated by bubble nucleation and collision have an amplitude which is estimated to be of order {omega}{sub GW}h{sup 2}{proportional_to}10{sup -11} at f=3 x 10{sup -4} Hz, which is within reach of the planned sensitivity of LISA. For another range of parameters, we find that the amplitude is estimated to be of order {omega}{sub GW}h{sup 2}{proportional_to} 0{sup -25} around f=10{sup 3} Hz, which is within reach of LIGO. Hence, it is possible to detect gravity waves from such a phase transition at two different detectors, with completely different amplitude and frequency ranges. (orig.)

Influences of Gravity Waves on Convectively Induced Turbulence (CIT): A Review

Science.gov (United States)

Sharman, Robert D.; Trier, S. B.

2018-03-01

Thunderstorms are known to produce turbulence. Such turbulence is commonly referred to as convectively induced turbulence or CIT, and can be hazardous to aviation. Although this turbulence can occur both within and outside the convection, out-of-cloud CIT is particularly hazardous, since it occurs in clear air and cannot be seen by eye or onboard radar. Furthermore, due to its small scale and its ties to the underlying convection, it is very difficult to forecast. Guidelines for out-of-cloud CIT avoidance are available, but they are oversimplified and can be misleading. In the search for more appropriate and physically based avoidance guidelines, considerable research has been conducted in recent years on the nature of the phenomenon, and in particular, its connection to gravity waves generated by the convection. This paper reviews the advances in our understanding of out-of-cloud CIT and its relation to convective gravity waves, and provides several detailed examples of observed cases to elucidate some of the underlying dynamics.

Seasonal and nightly variations of gravity-wave energy density in the middle atmosphere measured by the Purple Crow Lidar

Directory of Open Access Journals (Sweden)

R. J. Sica

2007-11-01

Full Text Available The Purple Crow Lidar (PCL is a large power-aperture product monostatic Rayleigh-Raman-Sodium-resonance-fluorescence lidar, which has been in operation at the Delaware Observatory (42.9° N, 81.4° W, 237 m elevation near the campus of The University of Western Ontario since 1992. Kinetic-energy density has been calculated from the Rayleigh-scatter system measurements of density fluctuations at temporal-spatial scales relevant for gravity waves, e.g. soundings at 288 m height resolution and 9 min temporal resolution in the upper stratosphere and mesosphere. The seasonal averages from 10 years of measurements show in all seasons some loss of gravity-wave energy in the upper stratosphere. During the equinox periods and summer the measurements are consistent with gravity waves growing in height with little saturation, in agreement with the classic picture of the variations in the height at which gravity waves break given by Lindzen (1981. The mean values compare favourably to previous measurements when computed as nightly averages, but the high temporal-spatial resolution measurements show considerable day-to-day variability. The variability over a night is often extremely large, with typical RMS fluctuations of 50 to 100% at all heights and seasons common. These measurements imply that using a daily or nightly-averaged gravity-wave energy density in numerical models may be highly unrealistic.

A novel method for the extraction of local gravity wave parameters from gridded three-dimensional data: description, validation, and application

Directory of Open Access Journals (Sweden)

L. Schoon

2018-05-01

Full Text Available For the local diagnosis of wave properties, we develop, validate, and apply a novel method which is based on the Hilbert transform. It is called Unified Wave Diagnostics (UWaDi. It provides the wave amplitude and three-dimensional wave number at any grid point for gridded three-dimensional data. UWaDi is validated for a synthetic test case comprising two different wave packets. In comparison with other methods, the performance of UWaDi is very good with respect to wave properties and their location. For a first practical application of UWaDi, a minor sudden stratospheric warming on 30 January 2016 is chosen. Specifying the diagnostics for hydrostatic inertia–gravity waves in analyses from the European Centre for Medium-Range Weather Forecasts, we detect the local occurrence of gravity waves throughout the middle atmosphere. The local wave characteristics are discussed in terms of vertical propagation using the diagnosed local amplitudes and wave numbers. We also note some hints on local inertia–gravity wave generation by the stratospheric jet from the detection of shallow slow waves in the vicinity of its exit region.

The effect of breaking gravity waves on the dynamics and chemistry of the mesosphere and lower thermosphere (invited review)

Science.gov (United States)

Garcia, R. R.

1986-01-01

The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.

Linear wave systems on n-D spatial domains

NARCIS (Netherlands)

Kurula, Mikael; Zwart, Heiko J.

2015-01-01

In this paper, we study the linear wave equation on an n-dimensional spatial domain.We show that there is a boundary triplet associated to the undamped wave equation. This enables us to characterise all boundary conditions for which the undamped wave equation possesses a unique solution

Mesospheric Temperature Measurements over Scandinavia During the Gravity Wave Life Cycle Campaign (GW-LCYCLE)

Science.gov (United States)

Pautet, P. D.; Taylor, M.; Kaifler, B.

2016-12-01

The Gravity Wave Life Cycle (GW-LCYCLE) project took place in Northern Scandinavia during the winter 2015-16. This international program focused on investigating the generation and deep propagation of atmospheric gravity waves, especially the orographic waves generated over the Scandinavian mountain range. A series of instruments was operated at several ground-based locations and on-board the DLR HALO Gulfstream V and Falcon aircrafts. As part of this project, Utah State University (USU) deployed 3 Advanced Mesospheric Temperature Mappers (AMTM) at the ALOMAR facility, Norway (operational since December 2010), at the IRF institute in Kiruna, Sweden, and at the FMI institute in Sodankylä, Finland. Each of these instruments measures the OH (3,1) rotational temperature over a large region (200x160km) at 87km altitude. During the campaign, their total coverage extended across the Scandinavian Mountain Range, from the wind side in the west to 500 km to the east in the lee of the mountains, allowing the investigation of the occurrence and evolution of gravity waves (GWs) over this part of Scandinavia. Furthermore, the AMTM in Sodankylä operated in the container housing a DLR Rayleigh lidar. Both instruments ran simultaneously and autonomously from November 2015 to April 2016, providing an unprecedented complementary high-quality data set. This presentation will introduce preliminary results obtained during this campaign, in particular the evolution of the mesospheric temperature through the winter, the analysis of mountain waves occurrence and dynamics at mesospheric altitude, as well as the investigation of interesting individual GW cases.

Electromagnetic waves in gravitational wave spacetimes

International Nuclear Information System (INIS)

Haney, M.; Bini, D.; Ortolan, A.; Fortini, P.

2013-01-01

We have considered the propagation of electromagnetic waves in a space-time representing an exact gravitational plane wave and calculated the induced changes on the four-potential field Aμ of a plane electromagnetic wave. By choosing a suitable photon round-trip in a Michelson interferometer, we have been able to identify the physical effects of the exact gravitational wave on the electromagnetic field, i.e. phase shift, change of the polarization vector, angular deflection and delay. These results have been exploited to study the response of an interferometric gravitational wave detector beyond the linear approximation of the general theory of relativity. A much more detailed examination of this problem can be found in our paper recently published in Classical and Quantum Gravity (28 (2011) 235007).

Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign – Part II: Radar investigations and modelling studies

Directory of Open Access Journals (Sweden)

A. Serafimovich

2006-11-01

Full Text Available We present an experimental and modelling study of a strong gravity wave event in the upper troposphere/lower stratosphere near the Scandinavian mountain ridge. Continuous VHF radar measurements during the MaCWAVE rocket and ground-based measurement campaign were performed at the Norwegian Andoya Rocket Range (ARR near Andenes (69.3° N, 16° E in January 2003. Detailed gravity wave investigations based on PSU/NCAR Fifth-Generation Mesoscale Model (MM5 data have been used for comparison with experimentally obtained results. The model data show the presence of a mountain wave and of an inertia gravity wave generated by a jet streak near the tropopause region. Temporal and spatial dependencies of jet induced inertia gravity waves with dominant observed periods of about 13 h and vertical wavelengths of ~4.5–5 km are investigated with wavelet transform applied on radar measurements and model data. The jet induced wave packet is observed to move upstream and downward in the upper troposphere. The model data agree with the experimentally obtained results fairly well. Possible reasons for the observed differences, e.g. in the time of maximum of the wave activity, are discussed. Finally, the vertical fluxes of horizontal momentum are estimated with different methods and provide similar amplitudes. We found indications that the derived positive vertical flux of the horizontal momentum corresponds to the obtained parameters of the jet-induced inertia gravity wave, but only at the periods and heights of the strongest wave activity.

Numerical Simulation of a Breaking Gravity Wave Event Over Greenland Observed During Fastex

National Research Council Canada - National Science Library

Doyle, James

1997-01-01

Measurements from the NOAA G4 research aircraft and high-resolution numerical simulations are used to study the evolution and dynamics of a large-amplitude gravity wave event over Greenland that took...

Dynamical influence of gravity waves generated by the Vestfjella Mountains in Antarctica: radar observations, fine-scale modelling and kinetic energy budget analysis

Directory of Open Access Journals (Sweden)

Joel Arnault

2012-02-01

Full Text Available Gravity waves generated by the Vestfjella Mountains (in western Droning Maud Land, Antarctica, southwest of the Finnish/Swedish Aboa/Wasa station have been observed with the Moveable atmospheric radar for Antarctica (MARA during the SWEDish Antarctic Research Programme (SWEDARP in December 2007/January 2008. These radar observations are compared with a 2-month Weather Research Forecast (WRF model experiment operated at 2 km horizontal resolution. A control simulation without orography is also operated in order to separate unambiguously the contribution of the mountain waves on the simulated atmospheric flow. This contribution is then quantified with a kinetic energy budget analysis computed in the two simulations. The results of this study confirm that mountain waves reaching lower-stratospheric heights break through convective overturning and generate inertia gravity waves with a smaller vertical wavelength, in association with a brief depletion of kinetic energy through frictional dissipation and negative vertical advection. The kinetic energy budget also shows that gravity waves have a strong influence on the other terms of the budget, i.e. horizontal advection and horizontal work of pressure forces, so evaluating the influence of gravity waves on the mean-flow with the vertical advection term alone is not sufficient, at least in this case. We finally obtain that gravity waves generated by the Vestfjella Mountains reaching lower stratospheric heights generally deplete (create kinetic energy in the lower troposphere (upper troposphere–lower stratosphere, in contradiction with the usual decelerating effect attributed to gravity waves on the zonal circulation in the upper troposphere–lower stratosphere.

Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

Directory of Open Access Journals (Sweden)

E. A. K. Ford

2008-02-01

Full Text Available Data from the Fabry-Perot Interferometers at KEOPS (Sweden, Sodankylä (Finland, and Svalbard (Norway, have been analysed for gravity wave activity on all the clear nights from 2000 to 2006. A total of 249 nights were available from KEOPS, 133 from Sodankylä and 185 from the Svalbard FPI. A Lomb-Scargle analysis was performed on each of these nights to identify the periods of any wave activity during the night. Comparisons between many nights of data allow the general characteristics of the waves that are present in the high latitude upper thermosphere to be determined. Comparisons were made between the different parameters: the atomic oxygen intensities, the thermospheric winds and temperatures, and for each parameter the distribution of frequencies of the waves was determined. No dependence on the number of waves on geomagnetic activity levels, or position in the solar cycle, was found. All the FPIs have had different detectors at various times, producing different time resolutions of the data, so comparisons between the different years, and between data from different sites, showed how the time resolution determines which waves are observed. In addition to the cutoff due to the Nyquist frequency, poor resolution observations significantly reduce the number of short-period waves (<1 h period that may be detected with confidence. The length of the dataset, which is usually determined by the length of the night, was the main factor influencing the number of long period waves (>5 h detected. Comparisons between the number of gravity waves detected at KEOPS and Sodankylä over all the seasons showed a similar proportion of waves to the number of nights used for both sites, as expected since the two sites are at similar latitudes and therefore locations with respect to the auroral oval, confirming this as a likely source region. Svalbard showed fewer waves with short periods than KEOPS data for a season when both had the same time resolution data

Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

Directory of Open Access Journals (Sweden)

J. F. McKenzie

2009-11-01

Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

Inviscid linear stability analysis of two fluid columns of different densities subject to gravity

Science.gov (United States)

Prathama, Aditya; Pantano, Carlos

2017-11-01

We investigate the inviscid linear stability of vertical interface between two fluid columns of different densities under the influence of gravity. In this flow arrangement, the two free streams are continuously accelerating, in contrast to the canonical Kelvin-Helmholtz or Rayleigh-Taylor instabilities whose base flows are stationary (or weakly time dependent). In these classical cases, the temporal evolution of the interface can be expressed as Fourier or Laplace solutions in time. This is not possible in our case; instead, we employ the initial value problem method to solve the equations analytically. The results, expressed in terms of the well-known parabolic cylinder function, indicate that the instability grows as the exponential of a quadratic function of time. The analysis shows that in this accelerating Kelvin-Helmholtz configuration, the interface is unconditionally unstable at all wave modes, despite the presence of surface tension. Department of Energy, National Nuclear Security Administration (Award No. DE-NA0002382) and the California Institute of Technology.

Effective gravitational wave stress-energy tensor in alternative theories of gravity

International Nuclear Information System (INIS)

Stein, Leo C.; Yunes, Nicolas

2011-01-01

The inspiral of binary systems in vacuum is controlled by the stress-energy of gravitational radiation and any other propagating degrees of freedom. For gravitational waves, the dominant contribution is characterized by an effective stress-energy tensor at future null infinity. We employ perturbation theory and the short-wavelength approximation to compute this stress-energy tensor in a wide class of alternative theories. We find that this tensor is generally a modification of that first computed by Isaacson, where the corrections can dominate over the general relativistic term. In a wide class of theories, however, these corrections identically vanish at asymptotically flat, future, null infinity, reducing the stress-energy tensor to Isaacson's. We exemplify this phenomenon by first considering dynamical Chern-Simons modified gravity, which corrects the action via a scalar field and the contraction of the Riemann tensor and its dual. We then consider a wide class of theories with dynamical scalar fields coupled to higher-order curvature invariants and show that the gravitational wave stress-energy tensor still reduces to Isaacson's. The calculations presented in this paper are crucial to perform systematic tests of such modified gravity theories through the orbital decay of binary pulsars or through gravitational wave observations.

First 3D measurements of temperature fluctuations induced by gravity wave with the infrared limb imager GLORIA

Science.gov (United States)

Krisch, Isabell; Preusse, Peter; Ungermann, Jörn; Friedl-Vallon, Felix; Riese, Martin

2017-04-01

Gravity waves (GWs) are one of the most important coupling mechanisms in the atmosphere. They couple different compartments of the atmosphere. The GW-LCYCLE (Gravity Wave Life Cycle) project aims on studying the excitation, propagation, and dissipation of gravity waves. An aircraft campaign has been performed in winter 2015/2016, during which the first 3D tomographic measurements of GWs were performed with the infrared limb imager GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere). GLORIA combines a classical Fourier Transform Spectrometer with a 2D detector array. The capability to image the atmosphere and thereby take several thousand spectra simultaneously improves the spatial sampling compared to conventional limb sounders by an order of magnitude. Furthermore GLORIA is able to pan the horizontal viewing direction and therefore measure the same volume of air under different angles. Due to these properties tomographic methods can be used to derive 3D temperature and tracer fields with spatial resolutions of better than 30km x 30km x 250m from measurements taken during circular flight patterns. Temperature distributions measured during a strong GW event on the 25.01.2016 during the GW-LCycle campaign over Iceland will be presented and analyzed for gravity waves. The three dimensional nature of the GLORIA measurements allows for the determination of the gravity wave momentum flux, including its horizontal direction. The calculated momentum fluxes rank this event under one of the strongest 1% observed in that latitude range in January 2016. The three dimensional wave vectors determined from the GLORIA measurements can be used for a ray tracing study with the Gravity wave Regional Or Global RAy Tracer (GROGRAT). Here 1D ray tracing, meaning solely vertical column propagation, as used by standard parameterizations in numerical weather prediction and climate models is compared to 4D ray tracing (spatially three dimensional with time varying

Impact of dissipation on the energy spectrum of experimental turbulence of gravity surface waves

Science.gov (United States)

Campagne, Antoine; Hassaini, Roumaissa; Redor, Ivan; Sommeria, Joël; Valran, Thomas; Viboud, Samuel; Mordant, Nicolas

2018-04-01

We discuss the impact of dissipation on the development of the energy spectrum in wave turbulence of gravity surface waves with emphasis on the effect of surface contamination. We performed experiments in the Coriolis facility, which is a 13-m-diam wave tank. We took care of cleaning surface contamination as well as possible, considering that the surface of water exceeds 100 m2. We observe that for the cleanest condition the frequency energy spectrum shows a power-law decay extending up to the gravity capillary crossover (14 Hz) with a spectral exponent that is increasing with the forcing strength and decaying with surface contamination. Although slightly higher than reported previously in the literature, the exponent for the cleanest water remains significantly below the prediction from the weak turbulence theory. By discussing length and time scales, we show that weak turbulence cannot be expected at frequencies above 3 Hz. We observe with a stereoscopic reconstruction technique that the increase with the forcing strength of energy spectrum beyond 3 Hz is mostly due to the formation and strengthening of bound waves.

A one-dimensional model of the semiannual oscillation driven by convectively forced gravity waves

Science.gov (United States)

Sassi, Fabrizio; Garcia, Rolando R.

1994-01-01

A one-dimensional model that solves the time-dependent equations for the zonal mean wind and a wave of specified zonal wavenumber has been used to illustrate the ability of gravity waves forced by time-dependent tropospheric heating to produce a semiannual oscillation (SAO) in the middle atmosphere. When the heating has a strong diurnal cycle, as observed over tropical landmasses, gravity waves with zonal wavelengths of a few thousand kilometers and phase velocities in the range +/- 40-50 m/sec are excited efficiently by the maximum vertical projection criterion (vertical wavelength approximately equals 2 x forcing depth). Calculations show that these waves can account for large zonal mean wind accelerations in the middle atmosphere, resulting in realistic stratopause and mesopause oscillations. Calculations of the temporal evolution of a quasi-conserved tracer indicate strong down-welling in the upper stratosphere near the equinoxes, which is associated with the descent of the SAO westerlies. In the upper mesosphere, there is a semiannual oscillation in tracer mixing ratio driven by seasonal variability in eddy mixing, which increases at the solstices and decreases at the equinoxes.

Investigation of Gravity Waves VIA the Rotational Temperature of Hydroxyl Nightglow

National Research Council Canada - National Science Library

Willingham, Erin

2001-01-01

... monochrometer optimized for the visible and near infrared. Quantifying gravity wave activity was the ultimate objective of this experiment. No spectrum of OH nightglow was recorded. The instrumentation was not sensitive enough to pick up the weak signal. This thesis is primarily a characterization of the equipment, its capabilities, and its limitations.

Linear theory of plasma filled backward wave oscillator

Indian Academy of Sciences (India)

An analytical and numerical study of backward wave oscillator (BWO) in linear regime is presented to get an insight into the excitation of electromagnetic waves as a result of the interaction of the relativistic electron beam with a slow wave structure. The effect of background plasma on the BWO instability is also presented.

Modulation of Precipitation in the Olympic Mountains by Trapped Gravity Waves

Science.gov (United States)

Heymsfield, G. M.; Tian, L.; Grecu, M.; McLinden, M.; Li, L.

2017-12-01

Precipitation over the Olympic Mountains was studied intensely with multiple aircraft and ground-based measurements during the Olympic Mountains Experiment (OLYMPEX) during the fall-winter season 2015-2016 as part of validation for the Global Precipitation Mission (GPM) (Houze et al. 2017) and the Radar Definition Experiment (RADEX) supported by the Aerosol Chemistry, Ecosystem (ACE) NASA Decadal Mission. This presentation focuses on observations of a broad frontal cloud system with strong flow over the mountains on 5 December 2015. Unique observations of trapped waves were obtained with in the three Goddard Space Flight Center nadir-looking, X- through W-band, Doppler radars on the NASA high-altitude ER-2: the High-altitude Wind and Rain Airborne Profiler (HIWRAP) at Ku and Ka-band, the W-band Cloud Radar System (CRS), and the ER-2 X-band Radar (EXRAD). Analysis of the aircraft measurements showed the presence of deep, trapped gravity waves on a scale ranging from 10-25 km in the nadir-looking Doppler and reflectivity observations. These waves cause localized vertical up/down motions on the order of 1-2 ms-1 and they are superimposed on the widespread south-southwest flow over the Olympic Mountains. While much of this widespread flow over the mountains produces copious amounts of snowfall, the gravity waves play an important role in modulating this precipitation indirectly through microphysical processes in the ice region. We will describe analyses of the interactions between the air motions and precipitation structure for this case and other cases we observed similar waves. We will present preliminary results from precipitation retrievals based on optimal estimation (Grecu et al. 2011).

Constraints on Born-Infeld gravity from the speed of gravitational waves after GW170817 and GRB 170817A

Science.gov (United States)

Jana, Soumya; Chakravarty, Girish Kumar; Mohanty, Subhendra

2018-04-01

The observations of gravitational waves from the binary neutron star merger event GW170817 and the subsequent observation of its electromagnetic counterparts from the gamma-ray burst GRB 170817A provide us a significant opportunity to study theories of gravity beyond general relativity. An important outcome of these observations is that they constrain the difference between the speed of gravity and the speed of light to less than 10-15c . Also, the time delay between the arrivals of gravitational waves at different detectors constrains the speed of gravity at the Earth to be in the range 0.55 c gravity: Eddington-inspired Born-Infeld (EiBI) gravity. We show that, in EiBI theory, the speed of gravitational waves in matter deviates from c . From the time delay in the arrival of gravitational wave signals at Earth-based detectors, we obtain the bound on the theory parameter κ as |κ |≲1021 m2 . Similarly, from the time delay between the signals of GW170817 and GRB 170817A, in a background Friedmann-Robertson-Walker universe, we obtain |κ |≲1037 m2 . Although the bounds on κ are weak compared to other earlier bounds from the study of neutron stars, stellar evolution, primordial nucleosynthesis, etc., our bounds are from direct observations and thus worth noting.

Gravity Waves in the Atmosphere of Mars as seen by the Radio Science Experiment MaRS on Mars Express

Science.gov (United States)

Tellmann, S.; Paetzold, M.; Häusler, B.; Bird, M. K.; Tyler, G. L.; Hinson, D. P.

2016-12-01

Gravity waves are atmospheric waves whose restoring force is the buoyancy. They are known to play an essential role in the redistribution of energy, momentum and atmospheric constituents in all stably stratified planetary atmospheres. Possible excitation mechanisms comprise convection in an adjacent atmospheric layer, other atmospheric instabilities like wind shear instabilities, or air flow over orographic obstacles especially in combination with the strong winter jets on Mars. Gravity waves on Mars were observed in the lower atmosphere [1,2] but are also expected to play a major role in the cooling of the thermosphere [3] and the polar warming [4]. A fundamental understanding of the possible source mechanisms is required to reveal the influence of small scale gravity waves on the global atmospheric circulation. Radio occultation profiles from the MaRS experiment on Mars Express [5] with their exceptionally high vertical resolution can be used to study small-scale vertical gravity waves and their global distribution in the lower atmosphere from the planetary boundary layer up to 40 km altitude. Atmospheric instabilities, which are clearly identified in the data, are used to gain further insight into possible atmospheric processes contributing to the excitation of gravity waves. [1] Creasey, J. E., et al.,(2006), Geophys. Res. Lett., 33, L01803, doi:10.1029/2005GL024037. [2]Tellmann, S., et al.(2013), J. Geophys. Res. Planets, 118, 306-320, doi:10.1002/jgre.20058. [3]Medvedev, A. S., et al.(2015), J. Geophys. Res. Planets, 120, 913-927. doi:10.1002/2015JE004802.[4] Barnes, J. R. (1990), J. Geophys. Res., 95, B2, 1401-1421. [5] Pätzold, M., et al. (2016), Planet. Space Sci., 127, 44 - 90.

Stoneley waves in a non-homogeneous orthotropic granular medium under the influence of gravity

Directory of Open Access Journals (Sweden)

S. M. Ahmed

2005-01-01

Full Text Available The aim of this paper is to investigate the Stoneley waves in a non-homogeneous orthotropic granular medium under the influence of a gravity field. The frequency equation obtained, in the form of a sixth-order determinantal expression, is in agreement with the corresponding result when both media are elastic. The frequency equation when the gravity field is neglected has been deduced as a particular case.

Gravity wave-driven fluctuations in OH nightglow from an extended, dissipative emission region

International Nuclear Information System (INIS)

Schubert, G.; Walterscheid, R.L.; Hickey, M.P.

1991-01-01

The theory of gravity wave-driven fluctuations in the OH nightglow from an extended source region is generalized to account for effects of eddy kinematic viscosity v and eddy thermal diffusivity κ. In the nondiffusive case, the amplitudes and phases of vertically integrated normalized intensity (δI)/(bar I) and temperature (δT 1 )/(bar T 1 ) perturbations and vertically integrated Krassovsky's ratio (η) as functions of period are influenced by the upper limit of vertical integration of the extended source, especially at long periods when vertical wavelengths γ v are small. The effects, which include oscillations in (δT)/(bar I), (δT 1 )/(bar T 1 ), and (η), particularly at long periods, are due to constructive and destructive interference of nightglow signals from vertically separated levels of the OH emitting region that occur when γ v is comparable to or smaller than the thickness of the main emission region. The sensitivity of these ratios to the upper limit of vertical integration occurs because of the relatively small rate of decay of the intensity of OH emission with height above the peak emission level and the exponential growth with altitude of nondissipative gravity waves. Because eddy diffusion increases γ v , especially at long periods, and reduces wave growth with height compared with the case v = κ = 0, inclusion of eddy diffusion removes the sensitivity of (η) and the other ratios ot the maximum height of vertical integration. It is essential to account for both eddy diffusion and emission from the entire vertically extended emission region to correctly predict (η), (δI)/(bar I), and (δT 1 )/(bar T 1 ) at long gravity wave periods

Intermittency of gravity wave momentum flux in the mesopause region observed with an all-sky airglow imager

Science.gov (United States)

Cao, Bing; Liu, Alan Z.

2016-01-01

The intermittency of gravity wave momentum flux (MF) near the OH airglow layer (˜87 km) in the mesopause region is investigated for the first time using observation of all-sky airglow imager over Maui, Hawaii (20.7°N, 156.3°W), and Cerro Pachón, Chile (30.3°S, 70.7°W). At both sites, the probability density function (pdf) of gravity wave MF shows two distinct distributions depending on the magnitude of the MF. For MF smaller (larger) than ˜16 m2 s-2 (0.091 mPa), the pdf follows a lognormal (power law) distribution. The intermittency represented by the Bernoulli proxy and the percentile ratio shows that gravity waves have higher intermittency at Maui than at Cerro Pachón, suggesting more intermittent background variation above Maui. It is found that most of the MF is contributed by waves that occur very infrequently. But waves that individually contribute little MF are also important because of their higher occurrence frequencies. The peak contribution is from waves with MF around ˜2.2 m2 s-2 at Cerro Pachón and ˜5.5 m2 s-2 at Maui. Seasonal variations of the pdf and intermittency imply that the background atmosphere has larger influence on the observed intermittency in the mesopause region.

Quantum solitonic wave-packet of a meso-scopic system in singularity free gravity

Science.gov (United States)

Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

2018-06-01

In this paper we will discuss how to localise a quantum wave-packet due to self-gravitating meso-scopic object by taking into account gravitational self-interaction in the Schrödinger equation beyond General Relativity. In particular, we will study soliton-like solutions in infinite derivative ghost free theories of gravity, which resolves the gravitational 1 / r singularity in the potential. We will show a unique feature that the quantum spread of such a gravitational system is larger than that of the Newtonian gravity, therefore enabling us a window of opportunity to test classical and quantum properties of such theories of gravity in the near future at a table-top experiment.

Several localized waves induced by linear interference between a nonlinear plane wave and bright solitons

Science.gov (United States)

Qin, Yan-Hong; Zhao, Li-Chen; Yang, Zhan-Ying; Yang, Wen-Li

2018-01-01

We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by a pair-transition coupled two-component Bose-Einstein condensate. We demonstrate that the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark solitons, W-shaped solitons, multi-peak solitons, Kuznetsov-Ma like breathers, and multi-peak breathers. Specifically, the explicit conditions for them are clarified by a phase diagram based on the linear interference properties. Furthermore, the interactions between these localized waves are discussed. The detailed analysis indicates that the soliton-soliton interaction induced phase shift brings the collision between these localized waves which can be inelastic for solitons involving collision and can be elastic for breathers. These characters come from the fact that the profile of solitons depends on the relative phase between bright solitons and a plane wave, and the profile of breathers does not depend on the relative phase. These results would motivate more discussions on linear interference between other nonlinear waves. Specifically, the solitons or breathers obtained here are not related to modulational instability. The underlying reasons are discussed in detail. In addition, possibilities to observe these localized waves are discussed in a two species Bose-Einstein condensate.

Development of stochastic webs in a wave-driven linear oscillator

International Nuclear Information System (INIS)

Murakami, Sadayoshi; Sato, Tetsuya; Hasegawa, Akira.

1988-01-01

We present developments of stochastic webs in a linear oscillator which is driven by a finite number (N) of external waves with frequency ω o (harmonic of the linear oscillator frequency). The expansion of the stochastic domain as functions of the number of waves and their amplitudes is studied numerically. The results with small amplitude waves compares well with the perturbation theory. When the amplitude of external waves is small a leaf structure which expands with N develops radially in the phase space. (author)

Gravitational waves from quasicircular black-hole binaries in dynamical Chern-Simons gravity.

Science.gov (United States)

Yagi, Kent; Yunes, Nicolás; Tanaka, Takahiro

2012-12-21

Dynamical Chern-Simons gravity cannot be strongly constrained with current experiments because it reduces to general relativity in the weak-field limit. This theory, however, introduces modifications in the nonlinear, dynamical regime, and thus it could be greatly constrained with gravitational waves from the late inspiral of black-hole binaries. We complete the first self-consistent calculation of such gravitational waves in this theory. For favorable spin orientations, advanced ground-based detectors may improve existing solar system constraints by 6 orders of magnitude.

Determination of gravity wave parameters in the airglow combining photometer and imager data

Science.gov (United States)

Nyassor, Prosper K.; Arlen Buriti, Ricardo; Paulino, Igo; Medeiros, Amauri F.; Takahashi, Hisao; Wrasse, Cristiano M.; Gobbi, Delano

2018-05-01

Mesospheric airglow measurements of two or three layers were used to characterize both vertical and horizontal parameters of gravity waves. The data set was acquired coincidentally from a multi-channel filter (Multi-3) photometer and an all-sky imager located at São João do Cariri (7.4° S, 36.5° W) in the equatorial region from 2001 to 2007. Using a least-square fitting and wavelet analysis technique, the phase and amplitude of each observed wave were determined, as well as the amplitude growth. Using the dispersion relation of gravity waves, the vertical and horizontal wavelengths were estimated and compared to the horizontal wavelength obtained from the keogram analysis of the images observed by an all-sky imager. The results show that both horizontal and vertical wavelengths, obtained from the dispersion relation and keogram analysis, agree very well for the waves observed on the nights of 14 October and 18 December 2006. The determined parameters showed that the observed wave on the night of 18 December 2006 had a period of ˜ 43.8 ± 2.19 min, with the horizontal wavelength of 235.66 ± 11.78 km having a downward phase propagation, whereas that of 14 October 2006 propagated with a period of ˜ 36.00 ± 1.80 min with a horizontal wavelength of ˜ 195 ± 9.80 km, and with an upward phase propagation. The observation of a wave taken by a photometer and an all-sky imager allowed us to conclude that the same wave could be observed by both instruments, permitting the investigation of the two-dimensional wave parameter.

An Estimation of Wave Attenuation Factor in Ultrasonic Assisted Gravity Drainage Process

Directory of Open Access Journals (Sweden)

Behnam Keshavarzi

2014-01-01

Full Text Available It has been proved that ultrasonic energy can considerably increase the amount of oil recovery in an immiscible displacement process. Although many studies have been performed on investigating the roles of ultrasonic waves, based on the best of our knowledge, little attention has been paid to evaluate wave attenuation parameter, which is an important parameter in the determination of the energy delivered to the porous medium. In this study, free fall gravity drainage process is investigated in a glass bead porous medium. Kerosene and Dorud crude oil are used as the wetting phases and air is used as the non-wetting phase. A piston-like displacement model with considering constant capillary pressure and applying Corey type approximation for relative permeabilities of both wetting and nonwetting phases is applied. A pressure term is considered to describe the presence of ultrasonic waves and the attenuation factor of ultrasonic waves is calculated by evaluating the value of external pressure applied to enhance the flow using the history matching of the data in the presence and absence of ultrasonic waves. The results introduce the attenuation factor as an important parameter in the process of ultrasonic assisted gravity drainage. The results show that only a low percentage of the ultrasonic energy (5.8% for Dorud crude oil and 3.3% for kerosene is delivered to the flow of the fluid; however, a high increase in oil recovery enhancement (15% for Dorud crude oil and 12% for Kerosene is observed in the experiments. This proves that the ultrasonic waves, even when the contribution is not substantial, can be a significantly efficient method for flow enhancement.

Gravitational radiation in relativistic theory of gravity with a nonzero graviton mass

International Nuclear Information System (INIS)

Vlasov, A.A.; Chugreev, Yu.V.

1987-01-01

Radiation of gravitation waves have been analysed in the linear approximation of the relative theory of gravity, with the mass of graviton being nonzero. It is shown that the main contribution to the energy loss due to gravitational radiation has been described by the well-known quadrupole formula. Linear approximation applicability conditions have been analysed

VLP seismicity from resonant modes of acoustic-gravity waves in a conduit-crack system filled with multiphase magma

Science.gov (United States)

Liang, C.; Prochnow, B. N.; OReilly, O. J.; Dunham, E. M.; Karlstrom, L.

2016-12-01

Oscillation of magma in volcanic conduits connected to cracks (dikes and sills) has been suggested as an explanation for very long period (VLP) seismic signals recorded at active basaltic volcanoes such as. Kilauea, Hawaii, and Erebus, Antarctica. We investigate the VLP seismicity using a linearized model for waves in and associated eigenmodes of a coupled conduit-crack system filled with multiphase magma, an extension of the Karlstrom and Dunham (2016) model for acoustic-gravity waves in volcanic conduits. We find that the long period surface displacement (as recorded on broadband seismometers) is dominated by opening/closing of the crack rather than the deformation of the conduit conduit walls. While the fundamental eigenmode is sensitive to the fluid properties and the geometry of the magma plumbing system, a closer scrutiny of various resonant modes reveals that the surface displacement is often more sensitive to higher modes. Here we present a systematic analysis of various long period acoustic-gravity wave resonant modes of a coupled conduit-crack system that the surface displacement is most sensitive to. We extend our previous work on a quasi-one-dimensional conduit model with inviscid magma to a more general axisymmetric conduit model that properly accounts for viscous boundary layers near the conduit walls, based on the numerical method developed by Prochnow et al. (submitted to Computers and Fluids, 2016). The surface displacement is dominated by either the fundamental or higher eigenmodes, depending on magma properties and the geometry of conduit and crack. An examination of the energetics of these modes reveals the complex interplay of different restoring forces (magma compressibility in the conduit, gravity, and elasticity of the crack) driving the VLP oscillations. Both nonequilibrium bubble growth and resorption and viscosity contribute to the damping of VLP signals. Our models thus provide a means to infer properties of open-vent basaltic volcanoes

On the covariant gauge {alpha} of the linearized gravity in de Sitter spacetime

Energy Technology Data Exchange (ETDEWEB)

Cheong, Lee Yen [Department of Fundamental and Applied Science Universiti Teknologi Petronas, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2012-09-26

In previous work, we studied the linearized gravity with covariant gauge {beta}= 2/3 and {alpha}= 5/3. It was found that the sum of the source and initial contributions reproduces the correct field configuration over the whole de Sitter spacetime. In this paper, we extend this work to generalizing the linearized gravitational field in an arbitrary value of the gauge parameter {alpha} but the gauge parameter {beta} remains the same.

The response of superpressure balloons to gravity wave motions

Directory of Open Access Journals (Sweden)

R. A. Vincent

2014-04-01

Full Text Available Superpressure balloons (SPB, which float on constant density (isopycnic surfaces, provide a unique way of measuring the properties of atmospheric gravity waves (GW as a function of wave intrinsic frequency. Here we devise a quasi-analytic method of investigating the SPB response to GW motions. It is shown that the results agree well with more rigorous numerical simulations of balloon motions and provide a better understanding of the response of SPB to GW, especially at high frequencies. The methodology is applied to ascertain the accuracy of GW studies using 12 m diameter SPB deployed in the 2010 Concordiasi campaign in the Antarctic. In comparison with the situation in earlier campaigns, the vertical displacements of the SPB were measured directly using GPS. It is shown using a large number of Monte Carlo-type simulations with realistic instrumental noise that important wave parameters, such as momentum flux, phase speed and wavelengths, can be retrieved with good accuracy from SPB observations for intrinsic wave periods greater than ca. 10 min. The noise floor for momentum flux is estimated to be ca. 10−4 mPa.

Observations of linear and nonlinear processes in the foreshock wave evolution

Directory of Open Access Journals (Sweden)

Y. Narita

2007-07-01

Full Text Available Waves in the foreshock region are studied on the basis of a hypothesis that the linear process first excites the waves and further wave-wave nonlinearities distribute scatter the energy of the primary waves into a number of daughter waves. To examine this wave evolution scenario, the dispersion relations, the wave number spectra of the magnetic field energy, and the dimensionless cross helicity are determined from the observations made by the four Cluster spacecraft. The results confirm that the linear process is the ion/ion right-hand resonant instability, but the wave-wave interactions are not clearly identified. We discuss various reasons why the test for the wave-wave nonlinearities fails, and conclude that the higher order statistics would provide a direct evidence for the wave coupling phenomena.

Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

Directory of Open Access Journals (Sweden)

J. F. McKenzie

2009-11-01

Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θ_c versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θ_c~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

Chiral gravity, log gravity, and extremal CFT

International Nuclear Information System (INIS)

Maloney, Alexander; Song Wei; Strominger, Andrew

2010-01-01

We show that the linearization of all exact solutions of classical chiral gravity around the AdS 3 vacuum have positive energy. Nonchiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity--the theory with logarithmically relaxed boundary conditions--has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic conformal field theories (CFT). Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We formally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.

Properties of internal planetary-scale inertio gravity waves in the mesosphere

Directory of Open Access Journals (Sweden)

H. G. Mayr

2004-11-01

Full Text Available At high latitudes in the upper mesosphere, horizontal wind oscillations have been observed with periods around 10h. Waves with such a period are generated in our Numerical Spectral Model (NSM, and they are identified as planetary-scale inertio gravity waves (IGW. These IGWs have periods between 9 and 11h and appear above 60km in the zonal mean (m=0, as well as in m=1 to 4, propagating eastward and westward. Under the influence of the Coriolis force, the amplitudes of the waves propagating westward are larger at high latitudes than those propagating eastward. The waves grow in magnitude at least up to about 100km and have vertical wavelengths around 25km. Applying a running window of 15 days for spectral analysis, the amplitudes in the wind field are typically between 10 and 20m/s and can reach 30m/s in the westward propagating component for m=1 at the poles. In the temperature perturbations, the wave amplitudes above 100km are typically 5K and as large as 10K for m=0 at the poles. The IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in late winter and spring. Numerical experiments show that such waves are also generated without excitation of the migrating tides. The amplitudes and periods then are similar, indicating that the tides are not essential to generate the waves. However, the seasonal variations without tides are significantly different, which leads to the conclusion that non linear interactions between the semidiurnal tide and planetary waves must contribute to the excitation of the IGWs. Directly or indirectly through the planetary waves, the IGWs are apparently excited by the instabilities that arise in the zonal mean circulation. When the solar heating is turned off for m=0, both the PWs and IGWs essentially disappear. That the IGWs and PWs have common roots in their excitation mechanism is also indicated by the striking similarity of their seasonal variations in the

Quantum spreading of a self-gravitating wave-packet in singularity free gravity

NARCIS (Netherlands)

Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein’s general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1 / r singularity in the potential – such

Ultra-Low Noise Quad Photoreceiver for Space Based Laser Interferometric Gravity Wave Detection, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Gravity wave detection using space-based long-baseline laser interferometric sensors imposes stringent noise requirements on the system components, including the...

Fast and local non-linear evolution of steep wave-groups on deep water: A comparison of approximate models to fully non-linear simulations

International Nuclear Information System (INIS)

Adcock, T. A. A.; Taylor, P. H.

2016-01-01

The non-linear Schrödinger equation and its higher order extensions are routinely used for analysis of extreme ocean waves. This paper compares the evolution of individual wave-packets modelled using non-linear Schrödinger type equations with packets modelled using fully non-linear potential flow models. The modified non-linear Schrödinger Equation accurately models the relatively large scale non-linear changes to the shape of wave-groups, with a dramatic contraction of the group along the mean propagation direction and a corresponding extension of the width of the wave-crests. In addition, as extreme wave form, there is a local non-linear contraction of the wave-group around the crest which leads to a localised broadening of the wave spectrum which the bandwidth limited non-linear Schrödinger Equations struggle to capture. This limitation occurs for waves of moderate steepness and a narrow underlying spectrum

Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 2. Gravity wave observations in the MLT region

Science.gov (United States)

Kumar, Karanam Kishore; Antonita, T. Maria; Shelbi, S. T.

2007-12-01

In the present communication, allSKy interferometric METeor (SKiYMET) radar observations of gravity wave activity in the mesosphere lower thermosphere (MLT) region over Thumba (8.5°N, 77°E) are presented. The present meteor radar system provides hourly zonal and meridional winds in the MLT region, which can be readily used for studying the tides, planetary waves, gravity waves of periods 2-6 hours, and other long period oscillations in this region. However, these hourly winds are not sufficient for studying short period gravity waves having periods less than an hour, which demand high temporal resolution measurements. Even though the winds are estimated on an hourly basis, information such as zenith angle, azimuth angle, and radial velocity of each detected meteor are archived. Using these details of the meteor, an algorithm is developed to obtain the 15-min temporal resolution wind data. The output of the algorithm is compared with hourly wind data, and it showed a good agreement during the high meteor shower periods. Most of the times high meteor counts are observed during late night and early morning hours (local) over this latitude. Continuous wind measurements during the high meteor shower periods are used for studying the gravity wave activity in the MLT region. As the wave activity is intermittent and nonstationary, wavelet analysis has been used for delineating the wave features. The results showed the upward propagating intermittent gravity waves with periods 1-2 and 4-5 hours. The new aspect of the present communication is the usage of meteor radar for gravity wave studies for the first time over this latitude and studying their seasonal variability.

Integrability and Linear Stability of Nonlinear Waves

Science.gov (United States)

Degasperis, Antonio; Lombardo, Sara; Sommacal, Matteo

2018-03-01

It is well known that the linear stability of solutions of 1+1 partial differential equations which are integrable can be very efficiently investigated by means of spectral methods. We present here a direct construction of the eigenmodes of the linearized equation which makes use only of the associated Lax pair with no reference to spectral data and boundary conditions. This local construction is given in the general N× N matrix scheme so as to be applicable to a large class of integrable equations, including the multicomponent nonlinear Schrödinger system and the multiwave resonant interaction system. The analytical and numerical computations involved in this general approach are detailed as an example for N=3 for the particular system of two coupled nonlinear Schrödinger equations in the defocusing, focusing and mixed regimes. The instabilities of the continuous wave solutions are fully discussed in the entire parameter space of their amplitudes and wave numbers. By defining and computing the spectrum in the complex plane of the spectral variable, the eigenfrequencies are explicitly expressed. According to their topological properties, the complete classification of these spectra in the parameter space is presented and graphically displayed. The continuous wave solutions are linearly unstable for a generic choice of the coupling constants.

Gravity wave spectra in the lower stratosphere diagnosed from project loon balloon trajectories

Science.gov (United States)

Schoeberl, M. R.; Jensen, E.; Podglajen, A.; Coy, L.; Lodha, C.; Candido, S.; Carver, R.

2017-08-01

Project Loon has been launching superpressure balloons since January 2013 to provide worldwide Internet coverage. These balloons typically fly between 18 and 21 km and provide measurements of winds and pressure fluctuations in the lower stratosphere. We divide 1560 Loon flights into 3405 two-day segments for gravity wave analysis. We derive the kinetic energy spectrum from the horizontal balloon motion and estimate the temperature perturbation spectrum (proportional to the potential energy spectrum) from the pressure variations. We fit the temperature (and kinetic energy) data to the functional form T'2 = T'o2[ω/ωο)α, where ω is the wave frequency, ωο is daily frequency, T'o is the base temperature amplitude, and α is the spectral slope. Both the kinetic energy and temperature spectra show -1.9 ± 0.2 power-law dependence in the intrinsic frequency window 3-50 cycles/day. The temperature spectrum slope is weakly anticorrelated with the base temperature amplitude. We also find that the wave base temperature distribution is highly skewed. The tropical modal temperature is 0.77 K. The highest amplitude waves occur over the mountainous regions, the tropics, and the high southern latitudes. Temperature amplitudes show little height variation over our 18-21 km domain. Our results are consistent with other limited superpressure balloon analyses. The modal temperature is higher than the temperature currently used in high-frequency gravity wave parameterizations.

Study of the linear and non-linear coupling of the LH wave to the tokamak plasmas

International Nuclear Information System (INIS)

Preynas, M.

2012-10-01

In order to achieve long pulse operation with a tokamak, additional heating and current drive systems are necessary. High frequency antennas, which deliver several megawatts of power to the plasma, are currently used in several tokamaks. Moreover, a good control of the coupling of the wave launched by the antenna to the edge plasma is required to optimize the efficiency of heating and current drive LH systems. However, non-linear effects which depend on the level of injected power in the plasma strongly damage the coupling of the LH wave at particular edge parameters (density and temperature profiles). Results presented in the manuscript deal with the study of the linear and non-linear coupling of the LH wave to the plasma. In the framework of the commissioning of the Passive Active Multijunction antenna in 2009 on the Tore Supra tokamak aiming at validating the LH system suggested for ITER, the characterisation of its coupling properties was realized from low power experiments. The experimental results, which are compared with the linear coupling code ALOHA, have validated the theoretical predictions of good coupling at edge plasma density around the cut-off density. Besides, the ponderomotive effect is clearly identified as responsible for the deterioration in the coupling of the wave, which is measured under particular edge plasma conditions. A theoretical model combining the coupling of the LH wave with the ponderomotive force is suggested to explain the experimental observations. Thus, a new full wave code (named PICCOLO-2D) was developed and results from simulations validate the working hypothesis of the contribution of the ponderomotive effect in the non-linear observations of LHCD coupling on Tore Supra. (author)

A fast wind-farm boundary-layer model to investigate gravity wave effects and upstream flow deceleration

Science.gov (United States)

Allaerts, Dries; Meyers, Johan

2017-11-01

Wind farm design and control often relies on fast analytical wake models to predict turbine wake interactions and associated power losses. Essential input to these models are the inflow velocity and turbulent intensity at hub height, which come from prior measurement campaigns or wind-atlas data. Recent LES studies showed that in some situations large wind farms excite atmospheric gravity waves, which in turn affect the upstream wind conditions. In the current study, we develop a fast boundary-layer model that computes the excitation of gravity waves and the perturbation of the boundary-layer flow in response to an applied force. The core of the model is constituted by height-averaged, linearised Navier-Stokes equations for the inner and outer layer, and the effect of atmospheric gravity waves (excited by the boundary-layer displacement) is included via the pressure gradient. Coupling with analytical wake models allows us to study wind-farm wakes and upstream flow deceleration in various atmospheric conditions. Comparison with wind-farm LES results shows excellent agreement in terms of pressure and boundary-layer displacement levels. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

Gravity wave generation and propagation during geomagnetic storms over Kiruna (67.8°N, 20.4°E

Directory of Open Access Journals (Sweden)

P. R. Fagundes

1995-04-01

Full Text Available Atmospheric gravity waves, detected over Kiruna (67.8°N, 20.4°E during geomagnetic storms, are presented and analysed. The data include direct measurements of the OI 630.0 nm emission line intensity, the x-component of the local geomagnetic field and thermospheric (meridional and zonal wind velocities derived from the OI 630.0 nm Doppler shift observed with an imaging Fabry-Perot interferometer (IFPI. A low pass band filter technique was used to determine short-period variations in the thermospheric meridional wind velocities observed during geomagnetic storms. These short-period variations in the meridional wind velocities, which are identified as due to gravity waves, are compared to the corresponding variations observed in the OI 630.0 nm emission line intensity, x-component of the local geomagnetic field and the location of the auroral electrojet. A cross-correlation analysis was used to calculate the propagation velocities of the observed gravity waves.

Gravitational waves during inflation from a 5D large-scale repulsive gravity model

International Nuclear Information System (INIS)

Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio

2012-01-01

We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

Gravitational waves during inflation from a 5D large-scale repulsive gravity model

Science.gov (United States)

Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio

2012-10-01

We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

Gravitational waves during inflation from a 5D large-scale repulsive gravity model

Energy Technology Data Exchange (ETDEWEB)

Reyes, Luz M., E-mail: luzmarinareyes@gmail.com [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Moreno, Claudia, E-mail: claudia.moreno@cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Madriz Aguilar, Jose Edgar, E-mail: edgar.madriz@red.cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Bellini, Mauricio, E-mail: mbellini@mdp.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata (UNMdP), Funes 3350, C.P. 7600, Mar del Plata (Argentina); Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR) - Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)

2012-10-22

We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

Analytical and numerical investigation of nonlinear internal gravity waves

Directory of Open Access Journals (Sweden)

S. P. Kshevetskii

2001-01-01

Full Text Available The propagation of long, weakly nonlinear internal waves in a stratified gas is studied. Hydrodynamic equations for an ideal fluid with the perfect gas law describe the atmospheric gas behaviour. If we neglect the term Ͽ dw/dt (product of the density and vertical acceleration, we come to a so-called quasistatic model, while we name the full hydro-dynamic model as a nonquasistatic one. Both quasistatic and nonquasistatic models are used for wave simulation and the models are compared among themselves. It is shown that a smooth classical solution of a nonlinear quasistatic problem does not exist for all t because a gradient catastrophe of non-linear internal waves occurs. To overcome this difficulty, we search for the solution of the quasistatic problem in terms of a generalised function theory as a limit of special regularised equations containing some additional dissipation term when the dissipation factor vanishes. It is shown that such solutions of the quasistatic problem qualitatively differ from solutions of a nonquasistatic nature. It is explained by the fact that in a nonquasistatic model the vertical acceleration term plays the role of a regularizator with respect to a quasistatic model, while the solution qualitatively depends on the regularizator used. The numerical models are compared with some analytical results. Within the framework of the analytical model, any internal wave is described as a system of wave modes; each wave mode interacts with others due to equation non-linearity. In the principal order of a perturbation theory, each wave mode is described by some equation of a KdV type. The analytical model reveals that, in a nonquasistatic model, an internal wave should disintegrate into solitons. The time of wave disintegration into solitons, the scales and amount of solitons generated are important characteristics of the non-linear process; they are found with the help of analytical and numerical investigations. Satisfactory

Computation of 3D steady Navier-Stokes flow with free-surface gravity waves

NARCIS (Netherlands)

Lewis, M.R.; Koren, B.; Raven, H.C.; Armfield, S.; Morgan, P.; Srinivas, K,

2003-01-01

In this paper an iterative method for the computation of stationary gravity-wave solutions is investigated, using a novel formulation of the free-surface (FS) boundary-value problem. This method requires the solution of a sequence of stationary Reynolds-Averaged Navier-Stokes subproblems employing

Computation of 3D steady Navier-Stokes flow with free-surface gravity waves

NARCIS (Netherlands)

M.R. Lewis; B. Koren (Barry); H.C. Raven

2003-01-01

textabstractIn this paper an iterative method for the computation of stationary gravity-wave solutions is investigated, using a novel formulation of the free-surface (FS) boundary-value problem. This method requires the solution of a sequence of stationary Reynolds-Averaged Navier-Stokes subproblems

Gravity wave propagation through a large semidiurnal tide and instabilities in the mesosphere and lower thermosphere during the winter 2003 MaCWAVE rocket campaign

Directory of Open Access Journals (Sweden)

B. P. Williams

2006-07-01

Full Text Available The winter MaCWAVE (Mountain and convective waves ascending vertically rocket campaign took place in January 2003 at Esrange, Sweden and the ALOMAR observatory in Andenes, Norway. The campaign combined balloon, lidar, radar, and rocket measurements to produce full temperature and wind profiles from the ground to 105 km. This paper will investigate gravity wave propagation in the mesosphere and lower thermosphere using data from the Weber sodium lidar on 28–29 January 2003. A very large semidiurnal tide was present in the zonal wind above 80 km that grew to a 90 m/s amplitude at 100 km. The superposition of smaller-scale gravity waves and the tide caused small regions of possible convective or shear instabilities to form along the downward progressing phase fronts of the tide. The gravity waves had periods ranging from the Nyquist period of 30 min up to 4 h, vertical wavelengths ranging from 7 km to more than 20 km, and the frequency spectra had the expected –5/3 slope. The dominant gravity waves had long vertical wavelengths and experienced rapid downward phase progression. The gravity wave variance grew exponentially with height up from 86 to 94 km, consistent with the measured scale height, suggesting that the waves were not dissipated strongly by the tidal gradients and resulting unstable regions in this altitude range.

Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

Science.gov (United States)

Wüst, Sabine; Offenwanger, Thomas; Schmidt, Carsten; Bittner, Michael; Jacobi, Christoph; Stober, Gunter; Yee, Jeng-Hwa; Mlynczak, Martin G.; Russell, James M., III

2018-05-01

For the first time, we present an approach to derive zonal, meridional, and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer, addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information, such as the wave group velocity vector.OH(3-1) spectrometer measurements allow the analysis of gravity wave ground-based periods but spatial information cannot necessarily be deduced. We use a scanning spectrometer and harmonic analysis to derive horizontal wavelengths at the mesopause altitude above Oberpfaffenhofen (48.09° N, 11.28° E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequencies and additional horizontal wind information, we calculate vertical wavelengths. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30° N, 13.02° E), Germany, ca. 380 km northeast of Oberpfaffenhofen, by a meteor radar.In order to compare our results, vertical temperature profiles of TIMED-SABER (thermosphere ionosphere mesosphere energetics dynamics, sounding of the atmosphere using broadband emission radiometry) overpasses are analysed with respect to the dominating vertical wavelength.

Propagation of acoustic waves in a stratified atmosphere, 1

Science.gov (United States)

Kalkofen, W.; Rossi, P.; Bodo, G.; Massaglia, S.

1994-01-01

This work is motivated by the chromospheric 3 minute oscillations observed in the K(sub 2v) bright points. We study acoustic gravity waves in a one-dimensional, gravitationally stratified, isothermal atmosphere. The oscillations are excited either by a velocity pulse imparted to a layer in an atmosphere of infinite vertical extent, or by a piston forming the lower boundary of a semi-infinite medium. We consider both linear and non-linear waves.

Instability of combined gravity-inertial-Rossby waves in atmospheres and oceans

Directory of Open Access Journals (Sweden)

J. F. McKenzie

2011-06-01

Full Text Available The properties of the instability of combined gravity-inertial-Rossby waves on a β-plane are investigated. The wave-energy exchange equation shows that there is an exchange of energy with the background stratified medium. The energy source driving the instability lies in the background enthalpy released by the gravitational buoyancy force. It is shown that if the phase speed of the westward propagating low frequency-long wavelength Rossby wave exceeds the Poincaré-Kelvin (or "equivalent" shallow water wave speed, instability arises from the merging of Rossby and Poincaré modes. There are two key parameters in this instability condition; namely, the equatorial/rotational Mach (or Froude number M and the latitude θ0 of the β-plane. In general waves equatorward of a critical latitude for given M can be driven unstable, with corresponding growth rates of the order of a day or so. Although these conclusions may only be safely drawn for short wavelengths corresponding to a JWKB wave packet propagating internally and located far from boundaries, nevertheless such a local instability may play a significant role in atmosphere-ocean dynamics.

Recent progress in mesospheric gravity wave studies using nightglow imaging system

Energy Technology Data Exchange (ETDEWEB)

Taylor, Michael J.; Pendleton Junior, William R.; Pautet, Pierre-Dominique; Zhao, Yucheng; Olsen, Chris; Babu, Hema Karnam Surendra [Center for Atmospheric and Space Sciences, Utah State University, Logan, Utah (United States); Medeiros, Amauri F. [Universidade Federal de Campina Grande, Centro de Ciencias e Tecnologia, Unidade Academica de Fisica, Campina Grande, PB (Brazil); Takahashi, Hisao, E-mail: mtaylor@cc.usu.edu, E-mail: wpen@cc.usu.edu, E-mail: dominiquepautet@gmail.com, E-mail: yucheng@cc.usu.edu, E-mail: cmellob@gmail.com, E-mail: hema_sb@rediffmail.com, E-mail: afragoso@df.ufcg.edu.br, E-mail: hisaotak@laser.inpe.br [INPE, Sao Jose dos Campos, SP (Brazil)

2007-07-01

A variety of optical remote sensing techniques have now revealed a rich spectrum of wave activity in the upper atmosphere. Many of these perturbations, with periodicities ranging from {approx} 5 min to many hours and horizontal scales of a few tens of km to several thousands km, are due to freely propagating atmospheric gravity waves and forced tidal oscillations. Passive optical observations of the spatial and temporal characteristics of these waves in the mesosphere and lower thermosphere (MLT) region ( {approx} 80-100 km) are facilitated by several naturally occurring, vertically distinct nightglow layers. This paper describes the use of state-of-the-art ground-based CCD imaging techniques to detect these waves in intensity and temperature. All-sky (180 deg ) image measurements are used to illustrate the characteristics of small-scale, short period ( < 1 hour) waves and to investigate their seasonal propagation and momentum impact on the MLT region. These results are then contrasted with measurements of mesospheric temperature made using a new temperature mapping imaging system capable of determining induced temperature amplitudes of a large range of wave motions and investigating night-to-night and seasonal variability in mesospheric temperature. (author)

Inertia-gravity waves in the troposphere and lower stratosphere associated with a jet stream exit region

Directory of Open Access Journals (Sweden)

L. Thomas

Full Text Available Radar measurements at Aberystwyth (52.4° N, 4.1° W of winds at tropospheric and lower stratospheric heights are shown for 12-13 March 1994 in a region of highly curved flow, downstream of the jet maximum. The perturbations of horizontal velocity have comparable amplitudes in the troposphere and lower stratosphere with downward and upward phase propagation, respectively, in these two height regions. The sense of rotation with increasing height in hodographs of horizontal perturbation velocity derived for hourly intervals show downwards propagation of energy in the troposphere and upward propagation in the lower stratosphere with vertical wavelengths of 1.7 to 2.3 km. The results indicate inertia-gravity waves propagating in a direction similar to that of the jet stream but at smaller velocities. Some of the features observed contrast with those of previous observations of inertia-gravity waves propagating transverse to the jet stream. The interpretation of the hodographs to derive wave parameters has taken account of the vertical shear of the background wind transverse to the direction of wave propagation.

Key words. Meteorology and atmospheric dynamics (mesoscale meteorology; middle atmosphere dynamics; waves and tides

Tsunami mitigation by resonant triad interaction with acoustic-gravity waves.

Science.gov (United States)

Kadri, Usama

2017-01-01

Tsunamis have been responsible for the loss of almost a half million lives, widespread long lasting destruction, profound environmental effects, and global financial crisis, within the last two decades. The main tsunami properties that determine the size of impact at the shoreline are its wavelength and amplitude in the ocean. Here, we show that it is in principle possible to reduce the amplitude of a tsunami, and redistribute its energy over a larger space, through forcing it to interact with resonating acoustic-gravity waves. In practice, generating the appropriate acoustic-gravity modes introduces serious challenges due to the high energy required for an effective interaction. However, if the findings are extended to realistic tsunami properties and geometries, we might be able to mitigate tsunamis and so save lives and properties. Moreover, such a mitigation technique would allow for the harnessing of the tsunami's energy.

Atmospheric gravity waves in the Red Sea: a new hotspot

KAUST Repository

Magalhaes, J. M.

2011-02-03

The region of the Middle East around the Red Sea (between 32° E and 44° E longitude and 12° N and 28° N latitude) is a currently undocumented hotspot for atmospheric gravity waves (AGWs). Satellite imagery shows evidence that this region is prone to relatively high occurrence of AGWs compared to other areas in the world, and reveals the spatial characteristics of these waves. The favorable conditions for wave propagation in this region are illustrated with three typical cases of AGWs propagating in the lower troposphere over the sea. Using weakly nonlinear long wave theory and the observed characteristic wavelengths we obtain phase speeds which are consistent with those observed and typical for AGWs, with the Korteweg-de Vries theory performing slightly better than Benjamin-Davis-Acrivos-Ono theory as far as phase speeds are concerned. ERS-SAR and Envisat-ASAR satellite data analysis between 1993 and 2008 reveals signatures consistent with horizontally propagating large-scale internal waves. These signatures cover the entire Red Sea and are more frequently observed between April and September, although they also occur during the rest of the year. The region\\'s (seasonal) propagation conditions for AGWs, based upon average vertical atmospheric stratification profiles suggest that many of the signatures identified in the satellite images are atmospheric internal waves. © Author(s) 2011.

A statistical study of variations of internal gravity wave energy characteristics in meteor zone

Science.gov (United States)

Gavrilov, N. M.; Kalov, E. D.

1987-01-01

Internal gravity wave (IGW) parameters obtained by the radiometer method have been considered by many other researchers. The results of the processing of regular radiometeor measurements taken during 1979 to 1980 in Obninsk (55.1 deg N, 36.6 deg E) are presented.

Holographic p-wave superfluid in Gauss–Bonnet gravity

International Nuclear Information System (INIS)

Liu, Shancheng; Pan, Qiyuan; Jing, Jiliang

2017-01-01

We construct the holographic p-wave superfluid in Gauss–Bonnet gravity via a Maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit. We obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second-order transition to the first-order one or for the emergence of the Cave of Winds. Moreover, for the supercurrents versus the superfluid velocity, we observe that our results near the critical temperature are independent of the Gauss–Bonnet parameter and agree well with the Ginzburg–Landau prediction.

Holographic p-wave superfluid in Gauss–Bonnet gravity

Energy Technology Data Exchange (ETDEWEB)

Liu, Shancheng [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Pan, Qiyuan, E-mail: panqiyuan@126.com [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Jing, Jiliang, E-mail: jljing@hunnu.edu.cn [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China)

2017-02-10

We construct the holographic p-wave superfluid in Gauss–Bonnet gravity via a Maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit. We obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second-order transition to the first-order one or for the emergence of the Cave of Winds. Moreover, for the supercurrents versus the superfluid velocity, we observe that our results near the critical temperature are independent of the Gauss–Bonnet parameter and agree well with the Ginzburg–Landau prediction.

An overset grid approach to linear wave-structure interaction

DEFF Research Database (Denmark)

Read, Robert; Bingham, Harry B.

2012-01-01

A finite-difference based approach to wave-structure interaction is reported that employs the overset approach to grid generation. A two-dimensional code that utilizes the Overture C++ library has been developed to solve the linear radiation problem for a floating body of arbitrary form. This sof......A finite-difference based approach to wave-structure interaction is reported that employs the overset approach to grid generation. A two-dimensional code that utilizes the Overture C++ library has been developed to solve the linear radiation problem for a floating body of arbitrary form...

On The Implications of Atmospheric Gravity Waves on Wind Power

OpenAIRE

Norris, Luke

2011-01-01

In view of the rapidly rising cost of fossil fuels and concerns over climate change, there can be little doubt that renewable energy is to play a large role in the future of our economic development. The impact of Atmospheric Gravity Waves (AGWs) on wind power is, at best, unclear. In this research, AGWs are successfully modelled both in theoretical and real world environments using the WindSim software package which has revealed a potential 7.4% drop in annual power output as a direct ...

Diffusion phenomenon for linear dissipative wave equations

KAUST Repository

Said-Houari, Belkacem

2012-01-01

In this paper we prove the diffusion phenomenon for the linear wave equation. To derive the diffusion phenomenon, a new method is used. In fact, for initial data in some weighted spaces, we prove that for {equation presented} decays with the rate {equation presented} [0,1] faster than that of either u or v, where u is the solution of the linear wave equation with initial data {equation presented} [0,1], and v is the solution of the related heat equation with initial data v 0 = u 0 + u 1. This result improves the result in H. Yang and A. Milani [Bull. Sci. Math. 124 (2000), 415-433] in the sense that, under the above restriction on the initial data, the decay rate given in that paper can be improved by t -γ/2. © European Mathematical Society.

No slip gravity

Science.gov (United States)

Linder, Eric V.

2018-03-01

A subclass of the Horndeski modified gravity theory we call No Slip Gravity has particularly interesting properties: 1) a speed of gravitational wave propagation equal to the speed of light, 2) equality between the effective gravitational coupling strengths to matter and light, Gmatter and Glight, hence no slip between the metric potentials, yet difference from Newton's constant, and 3) suppressed growth to give better agreement with galaxy clustering observations. We explore the characteristics and implications of this theory, and project observational constraints. We also give a simple expression for the ratio of the gravitational wave standard siren distance to the photon standard candle distance, in this theory and others, and enable a direct comparison of modified gravity in structure growth and in gravitational waves, an important crosscheck.

Horizontal velocities and propagation directions of gravity waves in the ionosphere over the Czech Republic

Czech Academy of Sciences Publication Activity Database

Chum, Jaroslav; Šindelářová, Tereza; Laštovička, Jan; Hruška, František; Burešová, Dalia; Baše, Jiří

2010-01-01

Roč. 115, - (2010), A11322/1-A11322/13 ISSN 0148-0227 R&D Projects: GA ČR GA205/07/1367; GA ČR GA205/09/1253 Grant - others:AV ČR(CZ) M100420901 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * gravity waves * wave propagation * remote sensing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.303, year: 2010

Plasma heating by non-linear wave-Plasma interaction | Echi ...

African Journals Online (AJOL)

We simulate the non-linear interaction of waves with magnetized tritium plasma with the aim of determining the parameter values that characterize the response of the plasma. The wave-plasma interaction has a non-conservative Hamiltonian description. The resulting system of Hamilton's equations is integrated numerically ...

A Stream Function Theory Based Calculation of Wave Kinematics for Very Steep Waves Using a Novel Non-linear Stretching Technique

DEFF Research Database (Denmark)

Stroescu, Ionut Emanuel; Sørensen, Lasse; Frigaard, Peter Bak

2016-01-01

A non-linear stretching method was implemented for stream function theory to solve wave kinematics for physical conditions close to breaking waves in shallow waters, with wave heights limited by the water depth. The non-linear stretching method proves itself robust, efficient and fast, showing good...

Simple analytical methods for computing the gravity-wave contribution to the cosmic background radiation anisotropy

International Nuclear Information System (INIS)

Wang, Y.

1996-01-01

We present two simple analytical methods for computing the gravity-wave contribution to the cosmic background radiation (CBR) anisotropy in inflationary models; one method uses a time-dependent transfer function, the other methods uses an approximate gravity-mode function which is a simple combination of the lowest order spherical Bessel functions. We compare the CBR anisotropy tensor multipole spectrum computed using our methods with the previous result of the highly accurate numerical method, the open-quote open-quote Boltzmann close-quote close-quote method. Our time-dependent transfer function is more accurate than the time-independent transfer function found by Turner, White, and Lindsey; however, we find that the transfer function method is only good for l approx-lt 120. Using our approximate gravity-wave mode function, we obtain much better accuracy; the tensor multipole spectrum we find differs by less than 2% for l approx-lt 50, less than 10% for l approx-lt 120, and less than 20% for l≤300 from the open-quote open-quote Boltzmann close-quote close-quote result. Our approximate graviton mode function should be quite useful in studying tensor perturbations from inflationary models. copyright 1996 The American Physical Society

Statistical properties of nonlinear one-dimensional wave fields

Directory of Open Access Journals (Sweden)

D. Chalikov

2005-01-01

Full Text Available A numerical model for long-term simulation of gravity surface waves is described. The model is designed as a component of a coupled Wave Boundary Layer/Sea Waves model, for investigation of small-scale dynamic and thermodynamic interactions between the ocean and atmosphere. Statistical properties of nonlinear wave fields are investigated on a basis of direct hydrodynamical modeling of 1-D potential periodic surface waves. The method is based on a nonstationary conformal surface-following coordinate transformation; this approach reduces the principal equations of potential waves to two simple evolutionary equations for the elevation and the velocity potential on the surface. The numerical scheme is based on a Fourier transform method. High accuracy was confirmed by validation of the nonstationary model against known solutions, and by comparison between the results obtained with different resolutions in the horizontal. The scheme allows reproduction of the propagation of steep Stokes waves for thousands of periods with very high accuracy. The method here developed is applied to simulation of the evolution of wave fields with large number of modes for many periods of dominant waves. The statistical characteristics of nonlinear wave fields for waves of different steepness were investigated: spectra, curtosis and skewness, dispersion relation, life time. The prime result is that wave field may be presented as a superposition of linear waves is valid only for small amplitudes. It is shown as well, that nonlinear wave fields are rather a superposition of Stokes waves not linear waves. Potential flow, free surface, conformal mapping, numerical modeling of waves, gravity waves, Stokes waves, breaking waves, freak waves, wind-wave interaction.

Statistical properties of nonlinear one-dimensional wave fields

Science.gov (United States)

Chalikov, D.

2005-06-01

A numerical model for long-term simulation of gravity surface waves is described. The model is designed as a component of a coupled Wave Boundary Layer/Sea Waves model, for investigation of small-scale dynamic and thermodynamic interactions between the ocean and atmosphere. Statistical properties of nonlinear wave fields are investigated on a basis of direct hydrodynamical modeling of 1-D potential periodic surface waves. The method is based on a nonstationary conformal surface-following coordinate transformation; this approach reduces the principal equations of potential waves to two simple evolutionary equations for the elevation and the velocity potential on the surface. The numerical scheme is based on a Fourier transform method. High accuracy was confirmed by validation of the nonstationary model against known solutions, and by comparison between the results obtained with different resolutions in the horizontal. The scheme allows reproduction of the propagation of steep Stokes waves for thousands of periods with very high accuracy. The method here developed is applied to simulation of the evolution of wave fields with large number of modes for many periods of dominant waves. The statistical characteristics of nonlinear wave fields for waves of different steepness were investigated: spectra, curtosis and skewness, dispersion relation, life time. The prime result is that wave field may be presented as a superposition of linear waves is valid only for small amplitudes. It is shown as well, that nonlinear wave fields are rather a superposition of Stokes waves not linear waves. Potential flow, free surface, conformal mapping, numerical modeling of waves, gravity waves, Stokes waves, breaking waves, freak waves, wind-wave interaction.

Convective cells of internal gravity waves in the earth's atmosphere with finite temperature gradient

Directory of Open Access Journals (Sweden)

O. Onishchenko

2013-03-01

Full Text Available In this paper, we have investigated vortex structures (e.g. convective cells of internal gravity waves (IGWs in the earth's atmosphere with a finite vertical temperature gradient. A closed system of nonlinear equations for these waves and the condition for existence of solitary convective cells are obtained. In the atmosphere layers where the temperature decreases with height, the presence of IGW convective cells is shown. The typical parameters of such structures in the earth's atmosphere are discussed.

On analyticity of linear waves scattered by a layered medium

Science.gov (United States)

Nicholls, David P.

2017-10-01

The scattering of linear waves by periodic structures is a crucial phenomena in many branches of applied physics and engineering. In this paper we establish rigorous analytic results necessary for the proper numerical analysis of a class of High-Order Perturbation of Surfaces methods for simulating such waves. More specifically, we prove a theorem on existence and uniqueness of solutions to a system of partial differential equations which model the interaction of linear waves with a multiply layered periodic structure in three dimensions. This result provides hypotheses under which a rigorous numerical analysis could be conducted for recent generalizations to the methods of Operator Expansions, Field Expansions, and Transformed Field Expansions.

Axisymmetric capillary-gravity waves at the interface of two viscous, immiscible fluids - Initial value problem

Science.gov (United States)

Farsoiya, Palas Kumar; Dasgupta, Ratul

2017-11-01

When the interface between two radially unbounded, viscous fluids lying vertically in a stable configuration (denser fluid below) at rest, is perturbed, radially propagating capillary-gravity waves are formed which damp out with time. We study this process analytically using a recently developed linearised theory. For small amplitude initial perturbations, the analytical solution to the initial value problem, represented as a linear superposition of Bessel modes at time t = 0 , is found to agree very well with results obtained from direct numerical simulations of the Navier-Stokes equations, for a range of initial conditions. Our study extends the earlier work by John W. Miles who studied this initial value problem analytically, taking into account, a single viscous fluid only. Implications of this study for the mechanistic understanding of droplet impact into a deep pool, will be discussed. Some preliminary, qualitative comparison with experiments will also be presented. We thank SERB Dept. Science & Technology, Govt. of India, Grant No. EMR/2016/000830 for financial support.

Mathematical Methods in Wave Propagation: Part 2--Non-Linear Wave Front Analysis

Science.gov (United States)

Jeffrey, Alan

1971-01-01

The paper presents applications and methods of analysis for non-linear hyperbolic partial differential equations. The paper is concluded by an account of wave front analysis as applied to the piston problem of gas dynamics. (JG)

Analytical Solution of Unsteady Gravity Flows of A Power-Law Fluid ...

African Journals Online (AJOL)

We present an analytical study of unsteady non-linear rheological effects of a power-law fluid under gravity. The fluid flows through a porous medium. The governing equations are derived and similarity solutions are determined. The results show the existence of traveling waves. It is assumed that the viscosity is temperature ...

Application of dopplionograms and gonionograms to atmospheric gravity wave disturbances in the ionosphere

International Nuclear Information System (INIS)

Wright, J.W.; Pitteway, M.L.V.

1982-01-01

A sequence of digital ionograms is processed by dopplionogram and gonionogram methods. Together, these disclose a disturbance in the F region which descends in altitude with time. Two wavelike periods of the disturbance are evident. The Doppler and angle-of-arrival behavior are consistent with a semiquantitative model of the plasma perturbations caused by an internal atmospheric gravity wave

Traveling-wave piezoelectric linear motor part II: experiment and performance evaluation.

Science.gov (United States)

Ting, Yung; Li, Chun-Chung; Chen, Liang-Chiang; Yang, Chieh-Min

2007-04-01

This article continues the discussion of a traveling-wave piezoelectric linear motor. Part I of this article dealt with the design and analysis of the stator of a traveling-wave piezoelectric linear motor. In this part, the discussion focuses on the structure and modeling of the contact layer and the carriage. In addition, the performance analysis and evaluation of the linear motor also are dealt with in this study. The traveling wave is created by stator, which is constructed by a series of bimorph actuators arranged in a line and connected to form a meander-line structure. Analytical and experimental results of the performance are presented and shown to be almost in agreement. Power losses due to friction and transmission are studied and found to be significant. Compared with other types of linear motors, the motor in this study is capable of supporting heavier loads and provides a larger thrust force.

Quintic quasi-topological gravity

Energy Technology Data Exchange (ETDEWEB)

Cisterna, Adolfo [Vicerrectoría académica, Universidad Central de Chile,Toesca 1783 Santiago (Chile); Instituto de Ciencias Físicas y Matemáticas, Universidad Austral de Chile,Casilla 567, Valdivia (Chile); Guajardo, Luis; Hassaïne, Mokhtar [Instituto de Matemática y Física, Universidad de Talca,Casilla 747, Talca (Chile); Oliva, Julio [Departamento de Física, Universidad de Concepción,Casilla, 160-C, Concepción (Chile)

2017-04-11

We construct a quintic quasi-topological gravity in five dimensions, i.e. a theory with a Lagrangian containing R{sup 5} terms and whose field equations are of second order on spherically (hyperbolic or planar) symmetric spacetimes. These theories have recently received attention since when formulated on asymptotically AdS spacetimes might provide for gravity duals of a broad class of CFTs. For simplicity we focus on five dimensions. We show that this theory fulfils a Birkhoff’s Theorem as it is the case in Lovelock gravity and therefore, for generic values of the couplings, there is no s-wave propagating mode. We prove that the spherically symmetric solution is determined by a quintic algebraic polynomial equation which resembles Wheeler’s polynomial of Lovelock gravity. For the black hole solutions we compute the temperature, mass and entropy and show that the first law of black holes thermodynamics is fulfilled. Besides of being of fourth order in general, we show that the field equations, when linearized around AdS are of second order, and therefore the theory does not propagate ghosts around this background. Besides the class of theories originally introduced in https://arxiv.org/abs/1003.4773, the general geometric structure of these Lagrangians remains an open problem.

Observation of mesospheric gravity waves at Comandante Ferraz Antarctica Station (62° S

Directory of Open Access Journals (Sweden)

P. B. Souza

2009-06-01

Full Text Available An airglow all-sky imager was operated at Comandante Ferraz Antarctica Station (62.1° S, 58.4° W, between April and October of 2007. Mesospheric gravity waves were observed using the OH airglow layer during 43 nights with good weather conditions. The waves presented horizontal wavelengths between 10 and 60 km and observed periods mainly distributed between 5 and 20 min. The observed phase speeds range between 5 m/s and 115 m/s; the majority of the wave velocities were between 10 and 60 m/s. The waves showed a preferential propagation direction towards the southwest in winter (May to July, while during spring (August to October there was an anisotropy with a preferential propagation direction towards the northwest. Unusual mesospheric fronts were also observed. The most probable wave source could be associated to orographic forcing, cold fronts or strong cyclonic activity in the Antarctica Peninsula.

Gravitational-Wave Tests of General Relativity with Ground-Based Detectors and Pulsar-Timing Arrays

Directory of Open Access Journals (Sweden)

Nicolás Yunes

2013-11-01

Full Text Available This review is focused on tests of Einstein's theory of general relativity with gravitational waves that are detectable by ground-based interferometers and pulsar-timing experiments. Einstein’s theory has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves will allow us to probe a complimentary, yet previously unexplored regime: the non-linear and dynamical strong-field regime. Such a regime is, for example, applicable to compact binaries coalescing, where characteristic velocities can reach fifty percent the speed of light and gravitational fields are large and dynamical. This review begins with the theoretical basis and the predicted gravitational-wave observables of modified gravity theories. The review continues with a brief description of the detectors, including both gravitational-wave interferometers and pulsar-timing arrays, leading to a discussion of the data analysis formalism that is applicable for such tests. The review ends with a discussion of gravitational-wave tests for compact binary systems.

Gravitational-Wave Tests of General Relativity with Ground-Based Detectors and Pulsar-Timing Arrays.

Science.gov (United States)

Yunes, Nicolás; Siemens, Xavier

2013-01-01

This review is focused on tests of Einstein's theory of general relativity with gravitational waves that are detectable by ground-based interferometers and pulsar-timing experiments. Einstein's theory has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves will allow us to probe a complimentary, yet previously unexplored regime: the non-linear and dynamical strong-field regime . Such a regime is, for example, applicable to compact binaries coalescing, where characteristic velocities can reach fifty percent the speed of light and gravitational fields are large and dynamical. This review begins with the theoretical basis and the predicted gravitational-wave observables of modified gravity theories. The review continues with a brief description of the detectors, including both gravitational-wave interferometers and pulsar-timing arrays, leading to a discussion of the data analysis formalism that is applicable for such tests. The review ends with a discussion of gravitational-wave tests for compact binary systems.

Linear Elastic Waves - Series: Cambridge Texts in Applied Mathematics (No. 26)

Science.gov (United States)

Harris, John G.

2001-10-01

Wave propagation and scattering are among the most fundamental processes that we use to comprehend the world around us. While these processes are often very complex, one way to begin to understand them is to study wave propagation in the linear approximation. This is a book describing such propagation using, as a context, the equations of elasticity. Two unifying themes are used. The first is that an understanding of plane wave interactions is fundamental to understanding more complex wave interactions. The second is that waves are best understood in an asymptotic approximation where they are free of the complications of their excitation and are governed primarily by their propagation environments. The topics covered include reflection, refraction, the propagation of interfacial waves, integral representations, radiation and diffraction, and propagation in closed and open waveguides. Linear Elastic Waves is an advanced level textbook directed at applied mathematicians, seismologists, and engineers. Aimed at beginning graduate students Includes examples and exercises Has application in a wide range of disciplines

Second generation diffusion model of interacting gravity waves on the surface of deep fluid

Directory of Open Access Journals (Sweden)

A. Pushkarev

2004-01-01

Full Text Available We propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum.

Alfven wave. [Book on linear and nonlinear properties for fusion applications

Energy Technology Data Exchange (ETDEWEB)

Hasegawa, A.; Uberoi, C.

1978-11-01

Seven chapters are included. Chapters 1 and 2 introduce the Alfven wave and describe its linear properties in a homogeneous medium. Chapters 3 and 4 cover the effects of inhomogeneities on these linear properties. Particular emphasis is placed on the appearance of a continuum spectrum and the associated absorption of the Alfven wave which arise due to the inhomogeneity. The explanation of the physical origin of absorption is given using kinetic theory. Chapter 5 is devoted to the associated plasma instabilities. Nonlinear effects discussed in Chapter 6 include quasilinear diffusion, decay, a solitary wave, and a modulational instability. The principles of Alfven wave heating, a design example and present-day experimental results are described in Chapter 7.

Asymptotic expansion of unsteady gravity flow of a power-law fluid ...

African Journals Online (AJOL)

We present a paper on the asymptotic expansion of unsteady non-linear rheological effects of a power-law fluid under gravity. The fluid flows through a porous medium. The asymptotic expansion is employed to obtain solution of the nonlinear problem. The results show the existence of traveling waves. It is assumed that the ...

The variational 2D Boussinesq model for wave propagation over a shoal

NARCIS (Netherlands)

Adytia, D.; van Groesen, Embrecht W.C.

2011-01-01

The Variational Boussinesq Model (VBM) for waves (Klopman et al. 2010) is based on the Hamiltonian structure of gravity surface waves. In its approximation, the fluid potential in the kinetic energy is approximated by the sum of its value at the free surface and a linear combination of vertical

A Note on Standing Internal Inertial Gravity Waves of Finite Amplitude

Science.gov (United States)

Thorpe, S. A.

2003-01-01

The effects of finite amplitude are examined in two-dimensional, standing, internal gravity waves in a rectangular container which rotates about a vertical axis at frequency f/2. Expressions are given for the velocity components, density fluctuations and isopycnal displacements to second order in the wave steepness in fluids with buoyancy frequency, N, of general form, and the effect of finite amplitude on wave frequency is given in an expansion to third order. The first order solutions, and the solutions to second order in the absence of rotation, are shown to conserve energy during a wave cycle. Analytical solutions are found to second order for the first two modes in a deep fluid with N proportional to sech(az), where z is the upward vertical coordinate and a is scaling factor. In the absence of rotation, results for the first mode in the latter stratification are found to be consistent with those for interfacial waves. An analytical solution to fourth order in a fluid with constant N is given and used to examine the effects of rotation on the development of static instability or of conditions in which shear instability may occur. As in progressive internal waves, an effect of rotation is to enhance the possibility of shear instability for waves with frequencies close to f. The analysis points to a significant difference between the dynamics of standing waves in containers of limited size and progressive internal waves in an unlimited fluid; the effect of boundaries on standing waves may inhibit the onset of instability. A possible application of the analysis is to transverse oscillations in long, narrow, steep-sided lakes such as Loch Ness, Scotland.

Consistent deformations of dual formulations of linearized gravity: A no-go result

International Nuclear Information System (INIS)

Bekaert, Xavier; Boulanger, Nicolas; Henneaux, Marc

2003-01-01

The consistent, local, smooth deformations of the dual formulation of linearized gravity involving a tensor field in the exotic representation of the Lorentz group with Young symmetry type (D-3,1) (one column of length D-3 and one column of length 1) are systematically investigated. The rigidity of the Abelian gauge algebra is first established. We next prove a no-go theorem for interactions involving at most two derivatives of the fields

Long-term Global Morphology of Gravity Wave Activity Using UARS Data

Science.gov (United States)

Eckermann, Stephen D.; Jackman, C. (Technical Monitor)

2000-01-01

This quarter was largely devoted to a detailed study of temperature data acquired by the Cryogenic Limb Array Etalon Spectrometer (CLAES) on UARS. Our analysis used the same sequence of methods that have been developed, tested and refined on a more limited subset of temperature data acquired by the CRISTA instrument. We focused on a limited subset of our reasoning that geographical and vertical trends in the small-scale temperature variability could be compared with similar trends observed in November 1994 by the CRISTA-SPAS satellite. Results, backed up with hindcasts from the Mountain Wave Forecast Model (MWFM), reveal strong evidence of mountain waves, most persuasively in the Himalayas on 16-17 November, 1992. These CLAES results are coherent over the 30-50 km range and compare well with MWFM hindcasts for the same period. This constitutes, we believe, the first clear evidence that CLAES explicitly resolved long wavelength gravity waves in its CO2 temperature channel. A series of other tasks, related to mesoscale modeling of mountain waves in CRISTA data and fitting of ground-based and HRDI data on global scales, were seen through to publication stage in peer-reviewed journals.

Planetary-Scale Inertio Gravity Waves in the Numerical Spectral Model

Science.gov (United States)

Mayr, H. G.; Mengel, J. R.; Talaat, E. R.; Porter, H. S.

2004-01-01

In the polar region of the upper mesosphere, horizontal wind oscillations have been observed with periods around 10 hours. Waves with such a period are generated in our Numerical Spectral Model (NSM), and they are identified as planetary-scale inertio gravity waves (IGW). These IGWs have periods between 9 and 11 hours and appear above 60 km in the zonal mean (m = 0), as well as in zonal wavenumbers m = 1 to 4. The waves can propagate eastward and westward and have vertical wavelengths around 25 km. The amplitudes in the wind field are typically between 10 and 20 m/s and can reach 30 m/s in the westward propagating component for m = 1 at the poles. In the temperature perturbations, the wave amplitudes above 100 km are typically 5 K and as large as 10 K for m = 0 at the poles. The IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in late winter and spring. In the NSM, the IGW are generated like the planetary waves (PW). They are produced apparently by the instabilities that arise in the zonal mean circulation. Relative to the PWs, however, the IGWs propagate zonally with much larger velocities, such that they are not affected much by interactions with the background zonal winds. Since the IGWs can propagate through the mesosphere without much interaction, except for viscous dissipation, one should then expect that they reach the thermosphere with significant and measurable amplitudes.

Investigation of inertia-gravity waves in the upper troposphere/lower stratosphere over Northern Germany observed with collocated VHF/UHF radars

Directory of Open Access Journals (Sweden)

A. Serafimovich

2005-01-01

Full Text Available A case study to investigate the properties of inertia-gravity waves in the upper troposphere/lower stratosphere has been carried out over Northern Germany during the occurrence of an upper tropospheric jet in connection with a poleward Rossby wave breaking event from 17-19 December 1999. The investigations are based on the evaluation of continuous radar measurements with the OSWIN VHF radar at Kühlungsborn (54.1 N, 11.8 E and the 482 MHz UHF wind profiler at Lindenberg (52.2 N, 14.1 E. Both radars are separated by about 265 km. Based on wavelet transformations of both data sets, the dominant vertical wavelengths of about 2-4 km for fixed times as well as the dominant observed periods of about 11 h and weaker oscillations with periods of  6 h for the altitude range between 5 and 8 km are comparable. Gravity wave parameters have been estimated at both locations separately and by a complex cross-spectral analysis of the data of both radars. The results show the appearance of dominating inertia-gravity waves with characteristic horizontal wavelengths of  300 km moving in the opposite direction than the mean background wind and a secondary less pronounced wave with a horizontal wavelength in the order of about 200 km moving with the wind. Temporal and spatial differences of the observed waves are discussed.

Sensitivity of Middle Atmospheric Temperature and Circulation in the UIUC Mesosphere-Stratosphere-Troposphere GCM to the Treatment of Subgrid-Scale Gravity-Wave Breaking

Science.gov (United States)

Yang, Fanglin; Schlesinger, Michael E.; Andranova, Natasha; Zubov, Vladimir A.; Rozanov, Eugene V.; Callis, Lin B.

2003-01-01

The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean- flow forcing due to breaking gravity waves was investigated using the University of Illinois at Urbana-Champaign 40-layer Mesosphere-Stratosphere-Troposphere General Circulation Model (MST-GCM). Three GCM experiments were performed. The gravity-wave forcing was represented first by Rayleigh friction, and then by the Alexander and Dunkerton (AD) parameterization with weak and strong breaking effects of gravity waves. In all experiments, the Palmer et al. parameterization was included to treat the breaking of topographic gravity waves in the troposphere and lower stratosphere. Overall, the experiment with the strong breaking effect simulates best the middle atmospheric temperature and circulation. With Rayleigh friction and the weak breaking effect, a large warm bias of up to 60 C was found in the summer upper mesosphere and lower thermosphere. This warm bias was linked to the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. With the strong breaking effect, the GCM was able to simulate this reversal, and essentially eliminated the warm bias. This improvement was the result of a much stronger meridional transport circulation that possesses a strong vertical ascending branch in the summer upper mesosphere, and hence large adiabatic cooling. Budget analysis indicates that 'in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are small. To obtain a transport circulation in the mesosphere of the UIUC MST-GCM that is strong enough to produce the observed cold summer mesopause, gravity-wave forcing larger than 100 m/s/day in magnitude is required near the summer mesopause. In

Local energy decay for linear wave equations with variable coefficients

Science.gov (United States)

Ikehata, Ryo

2005-06-01

A uniform local energy decay result is derived to the linear wave equation with spatial variable coefficients. We deal with this equation in an exterior domain with a star-shaped complement. Our advantage is that we do not assume any compactness of the support on the initial data, and its proof is quite simple. This generalizes a previous famous result due to Morawetz [The decay of solutions of the exterior initial-boundary value problem for the wave equation, Comm. Pure Appl. Math. 14 (1961) 561-568]. In order to prove local energy decay, we mainly apply two types of ideas due to Ikehata-Matsuyama [L2-behaviour of solutions to the linear heat and wave equations in exterior domains, Sci. Math. Japon. 55 (2002) 33-42] and Todorova-Yordanov [Critical exponent for a nonlinear wave equation with damping, J. Differential Equations 174 (2001) 464-489].

Asymptotic solutions and spectral theory of linear wave equations

International Nuclear Information System (INIS)

Adam, J.A.

1982-01-01

This review contains two closely related strands. Firstly the asymptotic solution of systems of linear partial differential equations is discussed, with particular reference to Lighthill's method for obtaining the asymptotic functional form of the solution of a scalar wave equation with constant coefficients. Many of the applications of this technique are highlighted. Secondly, the methods and applications of the theory of the reduced (one-dimensional) wave equation - particularly spectral theory - are discussed. While the breadth of application and power of the techniques is emphasised throughout, the opportunity is taken to present to a wider readership, developments of the methods which have occured in some aspects of astrophysical (particularly solar) and geophysical fluid dynamics. It is believed that the topics contained herein may be of relevance to the applied mathematician or theoretical physicist interest in problems of linear wave propagation in these areas. (orig./HSI)

The evolution of a localized nonlinear wave of the Kelvin-Helmholtz instability with gravity

Science.gov (United States)

Orazzo, Annagrazia; Hoepffner, Jérôme

2012-11-01

At the interface between two fluids of different density and in the presence of gravity, there are well known periodic surface waves which can propagate for long distances with little attenuation, as it is for instance the case at the surface of the sea. If wind is present, these waves progressively accumulate energy as they propagate and grow to large sizes—this is the Kelvin-Helmholtz instability. On the other hand, we show in this paper that for a given wind strength, there is potential for the growth of a localized nonlinear wave. This wave can reach a size such that the hydrostatic pressure drop from top to bottom equals the stagnation pressure of the wind. This process for the disruption of the flat interface is localized and nonlinear. We study the properties of this wave using numerical simulations of the Navier-Stokes equations.

Plasma flux and gravity waves in the midlatitude ionosphere during the solar eclipse of 20 May 2012

Science.gov (United States)

Chen, Gang; Wu, Chen; Huang, Xueqin; Zhao, Zhengyu; Zhong, Dingkun; Qi, Hao; Huang, Liang; Qiao, Lei; Wang, Jin

2015-04-01

The solar eclipse effects on the ionosphere are very complex. Except for the ionization decay due to the decrease of the photochemical process, the couplings of matter and energy between the ionosphere and the regions above and below will introduce much more disturbances. Five ionosondes in the Northeast Asia were used to record the midlatitude ionospheric responses to the solar eclipse of 20 May 2012. The latitude dependence of the eclipse lag was studied first. The foF2 response to the eclipse became slower with increased latitude. The response of the ionosphere at the different latitudes with the same eclipse obscuration differed from each other greatly. The plasma flux from the protonsphere was possibly produced by the rapid temperature drop in the lunar shadow to make up the ionization loss. The greater downward plasma flux was generated at higher latitude with larger dip angle and delayed the ionospheric response later. The waves in the foEs and the plasma frequency at the fixed height in the F layer are studied by the time period analytic method. The gravity waves of 43-51 min center period during and after the solar eclipse were found over Jeju and I-Cheon. The northward group velocity component of the gravity waves was estimated as ~108.7 m/s. The vertical group velocities between 100 and 150 km height over the two stations were calculated as ~5 and ~4.3 m/s upward respectively, indicating that the eclipse-induced gravity waves propagated from below the ionosphere.

Controlling the wave propagation through the medium designed by linear coordinate transformation

International Nuclear Information System (INIS)

Wu, Yicheng; He, Chengdong; Wang, Yuzhuo; Liu, Xuan; Zhou, Jing

2015-01-01

Based on the principle of transformation optics, we propose to control the wave propagating direction through the homogenous anisotropic medium designed by linear coordinate transformation. The material parameters of the medium are derived from the linear coordinate transformation applied. Keeping the space area unchanged during the linear transformation, the polarization-dependent wave control through a non-magnetic homogeneous medium can be realized. Beam benders, polarization splitter, and object illusion devices are designed, which have application prospects in micro-optics and nano-optics. The simulation results demonstrate the feasibilities and the flexibilities of the method and the properties of these devices. Design details and full-wave simulation results are provided. The work in this paper comprehensively applies the fundamental theories of electromagnetism and mathematics. The method of obtaining a new solution of the Maxwell equations in a medium from a vacuum plane wave solution and a linear coordinate transformation is introduced. These have a pedagogical value and are methodologically and motivationally appropriate for physics students and teachers at the undergraduate and graduate levels. (paper)

Controlling the wave propagation through the medium designed by linear coordinate transformation

Science.gov (United States)

Wu, Yicheng; He, Chengdong; Wang, Yuzhuo; Liu, Xuan; Zhou, Jing

2015-01-01

Based on the principle of transformation optics, we propose to control the wave propagating direction through the homogenous anisotropic medium designed by linear coordinate transformation. The material parameters of the medium are derived from the linear coordinate transformation applied. Keeping the space area unchanged during the linear transformation, the polarization-dependent wave control through a non-magnetic homogeneous medium can be realized. Beam benders, polarization splitter, and object illusion devices are designed, which have application prospects in micro-optics and nano-optics. The simulation results demonstrate the feasibilities and the flexibilities of the method and the properties of these devices. Design details and full-wave simulation results are provided. The work in this paper comprehensively applies the fundamental theories of electromagnetism and mathematics. The method of obtaining a new solution of the Maxwell equations in a medium from a vacuum plane wave solution and a linear coordinate transformation is introduced. These have a pedagogical value and are methodologically and motivationally appropriate for physics students and teachers at the undergraduate and graduate levels.

Linear density response function in the projector augmented wave method

DEFF Research Database (Denmark)

Yan, Jun; Mortensen, Jens Jørgen; Jacobsen, Karsten Wedel

2011-01-01

We present an implementation of the linear density response function within the projector-augmented wave method with applications to the linear optical and dielectric properties of both solids, surfaces, and interfaces. The response function is represented in plane waves while the single...... functions of Si, C, SiC, AlP, and GaAs compare well with previous calculations. While optical properties of semiconductors, in particular excitonic effects, are generally not well described by ALDA, we obtain excellent agreement with experiments for the surface loss function of graphene and the Mg(0001...

Radiative observables for linearized gravity on asymptotically flat spacetimes and their boundary induced states

International Nuclear Information System (INIS)

Benini, Marco; Dappiaggi, Claudio; Murro, Simone

2014-01-01

We discuss the quantization of linearized gravity on globally hyperbolic, asymptotically flat, vacuum spacetimes, and the construction of distinguished states which are both of Hadamard form and invariant under the action of all bulk isometries. The procedure, we follow, consists of looking for a realization of the observables of the theory as a sub-algebra of an auxiliary, non-dynamical algebra constructed on future null infinity ℑ + . The applicability of this scheme is tantamount to proving that a solution of the equations of motion for linearized gravity can be extended smoothly to ℑ + . This has been claimed to be possible provided that a suitable gauge fixing condition, first written by Geroch and Xanthopoulos [“Asymptotic simplicity is stable,” J. Math. Phys. 19, 714 (1978)], is imposed. We review its definition critically, showing that there exists a previously unnoticed obstruction in its implementation leading us to introducing the concept of radiative observables. These constitute an algebra for which a Hadamard state induced from null infinity and invariant under the action of all spacetime isometries exists and it is explicitly constructed

Short-period atmospheric gravity waves - A study of their statistical properties and source mechanisms

Science.gov (United States)

Gedzelman, S. D.

1983-01-01

Gravity waves for the one year period beginning 19 October 1976 around Palisades, New York, are investigated to determine their statistical properties and sources. The waves have typical periods of 10 min, pressure amplitudes of 3 Pa and velocities of 30 m/s. In general, the largest, amplitude waves occur during late fall and early winter when the upper tropospheric winds directly overhead are fastest and the static stability of the lower troposphere is greatest. Mean wave amplitudes correlate highly with the product of the mean maximum wind speed and the mean low level stratification directly aloft. A distinct diurnal variation of wave amplitudes with the largest waves occurring in the pre-dawn hours is also observed as a result of the increased static stability then. The majority of waves are generated by shear instability; however, a number of waves are generated by distant sources such as nuclear detonations or large thunderstorms. The waves with distant sources can be distinguished on the basis of their generally much higher coherency across the grid and velocities that depart markedly from the wind velocity at any point in the sounding.

Spectral energy transfer of atmospheric gravity waves through sum and difference nonlinear interactions

Energy Technology Data Exchange (ETDEWEB)

Huang, K.M. [Wuhan Univ. (China). School of Electronic Information; Chinese Academey of Sciences, Hefei (China). Key Lab. of Geospace Environment; Embry Riddle Aeronautical Univ., Daytona Beach, FL (United States). Dept. of Physical Science; Ministry of Education, Wuhan (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China); Liu, A.Z.; Li, Z. [Embry Riddle Aeronautical Univ., Daytona Beach, FL (United States). Dept. of Physical Science; Zhang, S.D.; Yi, F. [Wuhan Univ. (China). School of Electronic Information; Ministry of Education, Wuhan (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China)

2012-07-01

Nonlinear interactions of gravity waves are studied with a two-dimensional, fully nonlinear model. The energy exchanges among resonant and near-resonant triads are examined in order to understand the spectral energy transfer through interactions. The results show that in both resonant and near-resonant interactions, the energy exchange between two high frequency waves is strong, but the energy transfer from large to small vertical scale waves is rather weak. This suggests that the energy cascade toward large vertical wavenumbers through nonlinear interaction is inefficient, which is different from the rapid turbulence cascade. Because of considerable energy exchange, nonlinear interactions can effectively spread high frequency spectrum, and play a significant role in limiting wave amplitude growth and transferring energy into higher altitudes. In resonant interaction, the interacting waves obey the resonant matching conditions, and resonant excitation is reversible, while near-resonant excitation is not so. Although near-resonant interaction shows the complexity of match relation, numerical experiments show an interesting result that when sum and difference near-resonant interactions occur between high and low frequency waves, the wave vectors tend to approximately match in horizontal direction, and the frequency of the excited waves is also close to the matching value. (orig.)

Observations and modeling of wave-supported sediment gravity flows on the Po prodelta and comparison to prior observations from the Eel shelf

Science.gov (United States)

Traykovski, P.; Wiberg, P. L.; Geyer, W. R.

2007-02-01

A mooring and tripod array was deployed from the fall of 2002 through the spring of 2003 on the Po prodelta to measure sediment transport processes associated with sediment delivered from the Po River. Observations on the prodelta revealed wave-supported gravity flows of high concentration mud suspensions that are dynamically and kinematically similar to those observed on the Eel shelf [Traykovski, P., Geyer, W.R., Irish, J.D., Lynch, J.F., 2000. The role of wave-induced density-driven fluid mud flows for cross-shelf transport on the Eel River continental shelf. Continental Shelf Research 20, 2113-2140]. Due to the dynamic similarity between the two sites, a simple one-dimensional (1D) across-shelf model with the appropriate bottom boundary condition was used to examine fluxes associated with this transport mechanism at both locations. To calculate the sediment concentrations associated with the wave-dominated and wave-current resuspension, a bottom boundary condition using a reference concentration was combined with an "active layer" formulation to limit the amount of sediment in suspension. Whereas the wave-supported gravity flow mechanism dominated the transport on the Eel shelf, on the Po prodelta flux due to this mechanism is equal in magnitude to transport due to wave resuspension and wind-forced mean currents in the cross-shore direction. Southward transport due to wave resuspension and wind forced mean currents move an order of magnitude more sediment along-shore than the down-slope flux associated wave-supported gravity flows.

Quantum Gravity Experiments

Directory of Open Access Journals (Sweden)

Cahill R. T.

2015-10-01

Full Text Available A new quantum gravity experiment is reported with the data confirming the generali- sation of the Schrödinger equation to include the interaction of the wave function with dynamical space. Dynamical space turbulence, via this interaction process, raises and lowers the energy of the electron wave function, which is detected by observing conse- quent variations in the electron quantum barrier tunnelling rate in reverse-biased Zener diodes. This process has previously been reported and enabled the measurement of the speed of the dynamical space flow, which is consistent with numerous other detection experiments. The interaction process is dependent on the angle between the dynamical space flow velocity and the direction of the electron flow in the diode, and this depen- dence is experimentally demonstrated. This interaction process explains gravity as an emergent quantum process, so unifying quantum phenomena and gravity. Gravitational waves are easily detected.

Rayleigh-Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries

Science.gov (United States)

Titarchuk, Lev

2002-01-01

Accretion onto compact objects in X-ray binaries (black hole, neutron star (NS), white dwarf) is characterized by non-uniform flow density profiles. Such an effect of heterogeneity in presence of gravitational forces and pressure gradients exhibits Rayleigh-Taylor gravity waves (RTGW). They should be seen as quasiperiodic wave oscillations (QPO) of the accretion flow in the transition (boundary) layer between the Keplerian disk and the central object. In this paper the author shows that the main QPO frequency, which is very close to the Keplerian frequency, is split into separate frequencies (hybrid and low branch) under the influence of the gravitational forces in the rotational frame of reference. The RTGWs must be present and the related QPOs should be detected in any system where the gravity, buoyancy and Coriolis force effects cannot be excluded (even in the Earth and solar environments). The observed low and high QPO frequencies are an intrinsic signature of the RTGW. The author elaborates the conditions for the density profile when the RTGW oscillations are stable. A comparison of the inferred QPO frequencies with QPO observations is presented. The author finds that hectohertz frequencies detected from NS binaries can be identified as the RTGW low branch frequencies. The author also predicts that an observer can see the double NS spin frequency during the NS long (super) burst events when the pressure gradients and buoyant forces are suppressed. The Coriolis force is the only force which acts in the rotational frame of reference and its presence causes perfect coherent pulsations with a frequency twice of the NS spin. The QPO observations of neutron binaries have established that the high QPO frequencies do not go beyond of the certain upper limit. The author explains this observational effect as a result of the density profile inversions. Also the author demonstrates that a particular problem of the gravity waves in the rotational frame of reference in the

Simulation and Observation of Acoustic-Gravity Waves in the Ionosphere

Science.gov (United States)

Kunitsyn, Viacheslav; Andreeva, Elena; Krysanov, Boris; Nesterov, Ivan

Atmospheric and ionospheric perturbations associated with the acoustic-gravity waves (AGW) with typical frequencies of a few hertz -millihertz are considered. These events may be caused by the influence from space and atmosphere as well as by oscillations of the Earth surface and other near-surface phenomena. The surface sources include long-period oscillations of the Earth's surface, earthquakes, explosions, thermal heating, seisches and tsunami waves. The wavelike phenomena manifest themself as travelling disturbances of air (in the atmosphere) and of electron density (in the ionosphere). Travelling ionospheric disturbances (TIDs) are well detected by radio physical methods. AGW generation by near-surface sources is modeled by the numerical solution of the equation of geophysical fluid dynamics for different sources in two-dimensional non-linear dissipative compressible atmosphere. The numerical calculations are based on the FCT (Flux Corrected Transport) technique of the second order accuracy in time and space. Different scenarios of AGW generation are analyzed. The AGW caused by the surface sources within a few hertz-millihertz frequency band appear at the altitudes of middle atmosphere and ionosphere as the disturbances with typical scales from a few kilometers to several hundreds kilometers. Such structures can be successfully monitored by the methods of satellite radio tomography (RT). For the purposes of RT diagnostics of such disturbances, low-orbiting navigational satellites like Transit and Tsikada and high-orbiting navigation systems GPS/GLONASS are used. The results of numerical modeling of AGW generation by the surface sources are compared with the data of RT sounding. Also, generation of AGW by volumetric sources such as particle precipitation, rocket launching, heating by high-frequency radiation and other are considered. The obtained results proved the capability of RT methods of detecting and distinguishing between TIDs caused by AGW generated by

Numerical simulation and analysis of impact of non-orographic gravity waves drag of middle atmosphere in framework of a general circulation model

Science.gov (United States)

Zhao, J.; Wang, S.

2017-12-01

Gravity wave drag (GWD) is among the drivers of meridional overturning in the middle atmosphere, also known as the Brewer-Dobson Circulation, and of the quasi-biennial oscillation (QBO). The small spatial scales and complications due to wave breaking require their effects to be parameterised. GWD parameterizations are usually divided into two parts, orographic and non-orographic. The basic dynamical and physical processes of the middle atmosphere and the mechanism of the interactions between the troposphere and the middle atmosphere were studied in the frame of a general circulation model. The model for the troposphere was expanded to a global model considering middle atmosphere with the capability of describing the basic processes in the middle atmosphere and the troposphere-middle atmosphere interactions. Currently, it is too costly to include full non-hydrostatic and rotational wave dynamics in an operational parameterization. The hydrostatic non-rotational wave dynamics which allow an efficient implementation that is suitably fast for operation. The simplified parameterization of non-orographic GWD follows from the WM96 scheme in which a framework is developed using conservative propagation of gravity waves, critical level filtering, and non-linear dissipation. In order to simulate and analysis the influence of non-orographic GWD on the stratospheric wind and temperature fields, experiments using Stratospheric Sudden Warming (SSW) event case occurred in January 2013 were carried out, and results of objective weather forecast verifications of the two months period were compared in detail. The verification of monthly mean of forecast anomaly correlation (ACC) and root mean square (RMS) errors shows consistently positive impact of non-orographic GWD on skill score of forecasting for the three to eight days, both in the stratosphere and troposphere, and visible positive impact on prediction of the stratospheric wind and temperature fields. Numerical simulation

Wigner's little group as a gauge generator in linearized gravity theories

International Nuclear Information System (INIS)

Scaria, Tomy; Chakraborty, Biswajit

2002-01-01

We show that the translational subgroup of Wigner's little group for massless particles in 3 + 1 dimensions generates gauge transformation in linearized Einstein gravity. Similarly, a suitable representation of the one-dimensional translational group T(1) is shown to generate gauge transformation in the linearized Einstein-Chern-Simons theory in 2 + 1 dimensions. These representations are derived systematically from appropriate representations of translational groups which generate gauge transformations in gauge theories living in spacetime of one higher dimension by the technique of dimensional descent. The unified picture thus obtained is compared with a similar picture available for vector gauge theories in 3 + 1 and 2 + 1 dimensions. Finally, the polarization tensor of the Einstein-Pauli-Fierz theory in 2 + 1 dimensions is shown to split into the polarization tensors of a pair of Einstein-Chern-Simons theories with opposite helicities suggesting a doublet structure for the Einstein-Pauli-Fierz theory

Ion acoustic waves in pair-ion plasma: Linear and nonlinear analyses

International Nuclear Information System (INIS)

Saeed, R.; Mushtaq, A.

2009-01-01

Linear and nonlinear properties of low frequency ion acoustic wave (IAW) in pair-ion plasma in the presence of electrons are investigated. The dispersion relation and Kadomtsev-Petviashvili equation for linear/nonlinear IAW are derived from sets of hydrodynamic equations where the ion pairs are inertial while electrons are Boltzmannian. The dispersion curves for various concentrations of electrons are discussed and compared with experimental results. The predicted linear IAW propagates at the same frequencies as those of the experimentally observed IAW if n e0 ∼10 4 cm -3 . It is found that nonlinear profile of the ion acoustic solitary waves is significantly affected by the percentage ratio of electron number density and temperature. It is also determined that rarefactive solitary waves can propagate in this system. It is hoped that the results presented in this study would be helpful in understanding the salient features of the finite amplitude localized ion acoustic solitary pulses in a laboratory fullerene plasma.

Even-dimensional topological gravity from Chern-Simons gravity

International Nuclear Information System (INIS)

Merino, N.; Perez, A.; Salgado, P.

2009-01-01

It is shown that the topological action for gravity in 2n-dimensions can be obtained from the (2n+1)-dimensional Chern-Simons gravity genuinely invariant under the Poincare group. The 2n-dimensional topological gravity is described by the dynamics of the boundary of a (2n+1)-dimensional Chern-Simons gravity theory with suitable boundary conditions. The field φ a , which is necessary to construct this type of topological gravity in even dimensions, is identified with the coset field associated with the non-linear realizations of the Poincare group ISO(d-1,1).

On the mechanism of self gravitating Rossby interfacial waves in proto-stellar accretion discs

Science.gov (United States)

Yellin-Bergovoy, Ron; Heifetz, Eyal; Umurhan, Orkan M.

2016-05-01

The dynamical response of edge waves under the influence of self-gravity is examined in an idealised two-dimensional model of a proto-stellar disc, characterised in steady state as a rotating vertically infinite cylinder of fluid with constant density except for a single density interface at some radius ?. The fluid in basic state is prescribed to rotate with a Keplerian profile ? modified by some additional azimuthal sheared flow. A linear analysis shows that there are two azimuthally propagating edge waves, kin to the familiar Rossby waves and surface gravity waves in terrestrial studies, which move opposite to one another with respect to the local basic state rotation rate at the interface. Instability only occurs if the radial pressure gradient is opposite to that of the density jump (unstably stratified) where self-gravity acts as a wave stabiliser irrespective of the stratification of the system. The propagation properties of the waves are discussed in detail in the language of vorticity edge waves. The roles of both Boussinesq and non-Boussinesq effects upon the stability and propagation of these waves with and without the inclusion of self-gravity are then quantified. The dynamics involved with self-gravity non-Boussinesq effect is shown to be a source of vorticity production where there is a jump in the basic state density In addition, self-gravity also alters the dynamics via the radial main pressure gradient, which is a Boussinesq effect. Further applications of these mechanical insights are presented in the conclusion including the ways in which multiple density jumps or gaps may or may not be stable.

The generation of gravitational waves. 2. The post-linear formalism revisted

International Nuclear Information System (INIS)

Crowley, R.J.; Thorne, K.S.

1976-04-01

Different versions of the Green's function for the scalar wave equation in weakly curved space-time are compared and contrasted and their mathematical equivalence is demonstrated. Then the DeWitt--DeWitt Green's function is used to construct several alternative versions of the Thorne--Kovacs post-linear formalism for gravitational-wave generation. Finally, it is shown that, in calculations of gravitational bremsstrahlung radiation, some of the presented versions of the post-linear formalism allow one to treat the interacting bodies as point masses, while others do not

Large-scale dynamical influence of a gravity wave generated over the Antarctic Peninsula – regional modelling and budget analysis

Directory of Open Access Journals (Sweden)

JOEL Arnault

2013-03-01

Full Text Available The case study of a mountain wave triggered by the Antarctic Peninsula on 6 October 2005, which has already been documented in the literature, is chosen here to quantify the associated gravity wave forcing on the large-scale flow, with a budget analysis of the horizontal wind components and horizontal kinetic energy. In particular, a numerical simulation using the Weather Research and Forecasting (WRF model is compared to a control simulation with flat orography to separate the contribution of the mountain wave from that of other synoptic processes of non-orographic origin. The so-called differential budgets of horizontal wind components and horizontal kinetic energy (after subtracting the results from the simulation without orography are then averaged horizontally and vertically in the inner domain of the simulation to quantify the mountain wave dynamical influence at this scale. This allows for a quantitative analysis of the simulated mountain wave's dynamical influence, including the orographically induced pressure drag, the counterbalancing wave-induced vertical transport of momentum from the flow aloft, the momentum and energy exchanges with the outer flow at the lateral and upper boundaries, the effect of turbulent mixing, the dynamics associated with geostrophic re-adjustment of the inner flow, the deceleration of the inner flow, the secondary generation of an inertia–gravity wave and the so-called baroclinic conversion of energy between potential energy and kinetic energy.

Virtual Seafloor Reduces Internal Wave Generation by Tidal Flow

Science.gov (United States)

Zhang, Likun; Swinney, Harry L.

2014-03-01

Our numerical simulations of tidal flow of a stratified fluid over periodic knife-edge ridges and random topography reveal that the time-averaged tidal energy converted into internal gravity wave radiation arises only from the section of a ridge above a virtual seafloor. The average radiated power is approximated by the power predicted by linear theory if the height of the ridge is measured relative to the virtual floor. The concept of a virtual floor can extend the applicability of linear theory to global predictions of the conversion of tidal energy into internal wave energy in the oceans.

An Asymptotic and Stochastic Theory for the Effects of Surface Gravity Waves on Currents and Infragravity Waves

Science.gov (United States)

McWilliams, J. C.; Lane, E.; Melville, K.; Restrepo, J.; Sullivan, P.

2004-12-01

Oceanic surface gravity waves are approximately irrotational, weakly nonlinear, and conservative, and they have a much shorter time scale than oceanic currents and longer waves (e.g., infragravity waves) --- except where the primary surface waves break. This provides a framework for an asymptotic theory, based on separation of time (and space) scales, of wave-averaged effects associated with the conservative primary wave dynamics combined with a stochastic representation of the momentum transfer and induced mixing associated with non-conservative wave breaking. Such a theory requires only modest information about the primary wave field from measurements or operational model forecasts and thus avoids the enormous burden of calculating the waves on their intrinsically small space and time scales. For the conservative effects, the result is a vortex force associated with the primary wave's Stokes drift; a wave-averaged Bernoulli head and sea-level set-up; and an incremental material advection by the Stokes drift. This can be compared to the "radiation stress" formalism of Longuet-Higgins, Stewart, and Hasselmann; it is shown to be a preferable representation since the radiation stress is trivial at its apparent leading order. For the non-conservative breaking effects, a population of stochastic impulses is added to the current and infragravity momentum equations with distribution functions taken from measurements. In offshore wind-wave equilibria, these impulses replace the conventional surface wind stress and cause significant differences in the surface boundary layer currents and entrainment rate, particularly when acting in combination with the conservative vortex force. In the surf zone, where breaking associated with shoaling removes nearly all of the primary wave momentum and energy, the stochastic forcing plays an analogous role as the widely used nearshore radiation stress parameterizations. This talk describes the theoretical framework and presents some

Imaging gravity waves in lower stratospheric AMSU-A radiances, Part 2: Validation case study

Directory of Open Access Journals (Sweden)

S. D. Eckermann

2006-01-01

, horizontal structure and time evolution that closely match those observed in the AMSU-A data. These comparisons not only verify gravity wave detection and horizontal imaging capabilities for AMSU-A Channel 9, but provide an absolute validation of the anticipated radiance signals for a given three-dimensional gravity wave, based on the modeling of Eckermann and Wu (2006.

Revisiting linear plasma waves for finite value of the plasma parameter

Science.gov (United States)

Grismayer, Thomas; Fahlen, Jay; Decyk, Viktor; Mori, Warren

2010-11-01

We investigate through theory and PIC simulations the Landau-damping of plasma waves with finite plasma parameter. We concentrate on the linear regime, γφB, where the waves are typically small and below the thermal noise. We simulate these condition using 1,2,3D electrostatic PIC codes (BEPS), noting that modern computers now allow us to simulate cases where (nλD^3 = [1e2;1e6]). We study these waves by using a subtraction technique in which two simulations are carried out. In the first, a small wave is initialized or driven, in the second no wave is excited. The results are subtracted to provide a clean signal that can be studied. As nλD^3 is decreased, the number of resonant electrons can be small for linear waves. We show how the damping changes as a result of having few resonant particles. We also find that for small nλD^3 fluctuations can cause the electrons to undergo collisions that eventually destroy the initial wave. A quantity of interest is the the life time of a particular mode which depends on the plasma parameter and the wave number. The life time is estimated and then compared with the numerical results. A surprising result is that even for large values of nλD^3 some non-Vlasov discreteness effects appear to be important.

Distortion of gravitational-wave packets due to their self-gravity

International Nuclear Information System (INIS)

Kocsis, Bence; Loeb, Abraham

2007-01-01

When a source emits a gravity-wave (GW) pulse over a short period of time, the leading edge of the GW signal is redshifted more than the inner boundary of the pulse. The GW pulse is distorted by the gravitational effect of the self-energy residing in between these shells. We illustrate this distortion for GW pulses from the final plunge of black hole binaries, leading to the evolution of the GW profile as a function of the radial distance from the source. The distortion depends on the total GW energy released ε and the duration of the emission τ, scaled by the total binary mass M. The effect should be relevant in finite box simulations where the waveforms are extracted within a radius of 2 M. For characteristic emission parameters at the final plunge between binary black holes of arbitrary spins, this effect could distort the simulated GW templates for LIGO and LISA by a fraction of 10 -3 . Accounting for the wave distortion would significantly decrease the waveform extraction errors in numerical simulations

Two-dimensional linear and nonlinear Talbot effect from rogue waves.

Science.gov (United States)

Zhang, Yiqi; Belić, Milivoj R; Petrović, Milan S; Zheng, Huaibin; Chen, Haixia; Li, Changbiao; Lu, Keqing; Zhang, Yanpeng

2015-03-01

We introduce two-dimensional (2D) linear and nonlinear Talbot effects. They are produced by propagating periodic 2D diffraction patterns and can be visualized as 3D stacks of Talbot carpets. The nonlinear Talbot effect originates from 2D rogue waves and forms in a bulk 3D nonlinear medium. The recurrences of an input rogue wave are observed at the Talbot length and at the half-Talbot length, with a π phase shift; no other recurrences are observed. Differing from the nonlinear Talbot effect, the linear effect displays the usual fractional Talbot images as well. We also find that the smaller the period of incident rogue waves, the shorter the Talbot length. Increasing the beam intensity increases the Talbot length, but above a threshold this leads to a catastrophic self-focusing phenomenon which destroys the effect. We also find that the Talbot recurrence can be viewed as a self-Fourier transform of the initial periodic beam that is automatically performed during propagation. In particular, linear Talbot effect can be viewed as a fractional self-Fourier transform, whereas the nonlinear Talbot effect can be viewed as the regular self-Fourier transform. Numerical simulations demonstrate that the rogue-wave initial condition is sufficient but not necessary for the observation of the effect. It may also be observed from other periodic inputs, provided they are set on a finite background. The 2D effect may find utility in the production of 3D photonic crystals.

Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study

Directory of Open Access Journals (Sweden)

Anna E. Frost

2017-11-01

Full Text Available This paper presents a study on how the power absorption and damping in a linear generator for wave energy conversion are affected by partial overlap between stator and translator. The theoretical study shows that the electrical power as well as the damping coefficient change quadratically with partial stator overlap, if inductance, friction and iron losses are assumed independent of partial stator overlap or can be neglected. Results from onshore experiments on a linear generator for wave energy conversion cannot reject the quadratic relationship. Measurements were done on the inductance of the linear generator and no dependence on partial stator overlap could be found. Simulations of the wave energy converter’s operation in high waves show that entirely neglecting partial stator overlap will overestimate the energy yield and underestimate the peak forces in the line between the buoy and the generator. The difference between assuming a linear relationship instead of a quadratic relationship is visible but small in the energy yield in the simulation. Since the theoretical deduction suggests a quadratic relationship, this is advisable to use during modeling. However, a linear assumption could be seen as an acceptable simplification when modeling since other relationships can be computationally costly.

Lidar observations of middle atmospheric gravity wave activity over a low-latitude site (Gadanki, 13.5° N, 79.2° E

Directory of Open Access Journals (Sweden)

V. Sivakumar

2006-05-01

Full Text Available The low-latitude middle atmospheric gravity wave characteristics are presented using 310 nights of Rayleigh lidar observations made at Gadanki (13.5° N, 79.2° E over the period from March 1998 to December 2002. The gravity wave characteristics are presented in terms of vertical wave number and frequency spectra, along with the estimated potential energy for the four seasons, namely, spring, summer, autumn and winter. The computed wave number spectra for both the stratosphere and the mesosphere are found to differ significantly from a saturated model predicted spectrum. The spectra were found to be shallower at lower wave numbers and steeper at higher wave numbers with transition at ~8.85×10-4 cy/m. The computed frequency spectra seem to follow the model plot with a power law index of -5/3 above a frequency of ~2×10-4 Hz. The estimated potential energy per unit mass increases gradually up to ~60 km and then rather rapidly above this height to reach values of the order of 200J/kg at ~70 km.

Wavelet characterisation of ionospheric acoustic and gravity waves occuring during the solar eclipse of August 11, 1999

Czech Academy of Sciences Publication Activity Database

Šauli, Petra; Abry, P.; Boška, Josef; Duchayne, L.

2006-01-01

Roč. 68, 3-5 (2006), s. 586-598 ISSN 1364-6826 R&D Projects: GA ČR GP205/02/P077; GA ČR(CZ) GA205/01/1071; GA AV ČR(CZ) IAA3042102 Grant - others:CNRS(FR) 18098 Institutional research plan: CEZ:AV0Z30420517 Keywords : Solar eclipse * Acoustic-gravity waves * Vertical ionospheric sounding * Wavelet decomposition * Wave packet characterisation Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.448, year: 2006

Destruction of coherence in nondemolition monitoring: quantum 'watchdog effect' in gravity wave detectors

International Nuclear Information System (INIS)

Zurek, W.H.

1984-01-01

The author shows that nondemolition monitoring of a Weber bar may prevent changes of the number of phonons, and thus influence the sensitivity of quantum-counting gravity wave detectors. This effect is similar to the Watchdog Effect which is predicted to delay decays of the monitored, unstable quantum system. Relations between watchdog effect and Environment-Induced Superselection Rules as well as its connections to the fundamental questions of the quantum theory of measurement are briefly considered. (Auth.)

(abstract) Tropospheric Calibration for the Mars Observer Gravity Wave Experiment

Science.gov (United States)

Walter, Steven J.; Armstrong, John

1994-01-01

In spring 1993, microwave radiometer-based tropospheric calibration was provided for the Mars Observer gravitational wave search. The Doppler shifted X-band radio signals propagating between Earth and the Mars Observer satellite were precisely measured to determine path length variations that might signal passage of gravitational waves. Experimental sensitivity was restricted by competing sources of variability in signal transit time. Principally, fluctuations in the solar wind and ionospheric plasma density combined with fluctions in tropospheric refractivity determined the detection limit. Troposphere-induced path delay fluctions are dominated by refractive changes caused by water vapor inhomogeneities blowing through the signal path. Since passive microwave remote sensing techniques are able to determine atmospheric propagation delays, radiometer-based tropospheric calibration was provided at the Deep Space Network Uranus tracking site (DSS-15). Two microwave water vapor radiometers (WVRs), a microwave temperature profiler (MTP), and a ground based meterological station were deployed to determine line-of-sight vapor content and vertical temperature profile concurrently with Mars Observer tracking measurements. This calibration system provided the capability to correct Mars Observer Doppler data for troposphere-induced path variations. We present preliminary analysis of the Doppler and WVR data sets illustrating the utility of WVRs to calibrate Doppler data. This takes an important step toward realizing the ambitious system required to support future Ka-band Cassini satellite gravity wave tropospheric calibration system.

Exact solution to the Coulomb wave using the linearized phase-amplitude method

Directory of Open Access Journals (Sweden)

Shuji Kiyokawa

2015-08-01

Full Text Available The author shows that the amplitude equation from the phase-amplitude method of calculating continuum wave functions can be linearized into a 3rd-order differential equation. Using this linearized equation, in the case of the Coulomb potential, the author also shows that the amplitude function has an analytically exact solution represented by means of an irregular confluent hypergeometric function. Furthermore, it is shown that the exact solution for the Coulomb potential reproduces the wave function for free space expressed by the spherical Bessel function. The amplitude equation for the large component of the Dirac spinor is also shown to be the linearized 3rd-order differential equation.

Finite field-dependent symmetries in perturbative quantum gravity

International Nuclear Information System (INIS)

Upadhyay, Sudhaker

2014-01-01

In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and non-linear gauges. Further, we analyze the finite field-dependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gauge-fixing and ghost parts of the perturbative quantum gravity within functional integration. However, the operation of such symmetry transformation on the generating functional of perturbative quantum gravity does not affect the theory on physical ground. The FFBRST transformation with appropriate choices of finite BRST parameter connects non-linear Curci–Ferrari and Landau gauges of perturbative quantum gravity. The validity of the results is also established at quantum level using Batalin–Vilkovisky (BV) formulation. -- Highlights: •The perturbative quantum gravity is treated as gauge theory. •BRST and anti-BRST transformations are developed in linear and non-linear gauges. •BRST transformation is generalized by making it finite and field dependent. •Connection between linear and non-linear gauges is established. •Using BV formulation the results are established at quantum level also

Linear electrostatic waves in a three-component electron-positron-ion plasma

Energy Technology Data Exchange (ETDEWEB)

Mugemana, A., E-mail: mugemanaa@gmail.com; Moolla, S. [School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa); Lazarus, I. J. [Department of Mathematics, Statistics and Physics, Durban University of Technology, Durban 4000 (South Africa)

2014-12-15

Analytical linear electrostatic waves in a magnetized three-component electron-positron-ion plasma are studied in the low-frequency limit. By using the continuity and momentum equations with Poisson's equation, the dispersion relation for the electron-positron-ion plasma consisting of cool ions, and hot Boltzmann electrons and positrons is derived. In the linear regime, the propagation of two possible modes and their evolution are studied. In the cases of parallel and perpendicular propagation, it is shown that these two possible modes are always stable. The present investigation contributes to nonlinear propagation of electrostatic waves in space and the laboratory.

Ion-acoustic cnoidal wave and associated non-linear ion flux in dusty plasma

Energy Technology Data Exchange (ETDEWEB)

Jain, S. L. [Poornima Group of Institution, Sitapura, Jaipur 302022 (India); Tiwari, R. S. [Regional College for Education, Research and Technology, Jaipur 302022 (India); Mishra, M. K. [Department of Physics, University of Rajasthan, Jaipur 302004 (India)

2012-10-15

Using reductive perturbation method with appropriate boundary conditions, coupled evolution equations for first and second order potentials are derived for ion-acoustic waves in a collisionless, un-magnetized plasma consisting of hot isothermal electrons, cold ions, and massive mobile charged dust grains. The boundary conditions give rise to renormalization term, which enable us to eliminate secular contribution in higher order terms. Determining the non secular solution of these coupled equations, expressions for wave phase velocity and averaged non-linear ion flux associated with ion-acoustic cnoidal wave are obtained. Variation of the wave phase velocity and averaged non-linear ion flux as a function of modulus (k{sup 2}) dependent wave amplitude are numerically examined for different values of dust concentration, charge on dust grains, and mass ratio of dust grains with plasma ions. It is found that for a given amplitude, the presence of positively (negatively) charged dust grains in plasma decreases (increases) the wave phase velocity. This behavior is more pronounced with increase in dust concentrations or increase in charge on dust grains or decrease in mass ratio of dust grains. The averaged non-linear ion flux associated with wave is positive (negative) for negatively (positively) charged dust grains in the plasma and increases (decreases) with modulus (k{sup 2}) dependent wave amplitude. For given amplitude, it increases (decreases) as dust concentration or charge of negatively (positively) charged dust grains increases in the plasma.

Solitary waves under the competition of linear and nonlinear periodic potentials

International Nuclear Information System (INIS)

Rapti, Z; Kevrekidis, P G; Konotop, V V; Jones, C K R T

2007-01-01

In this paper, we study the competition of the linear and nonlinear lattices and its effects on the stability and dynamics of bright solitary waves. We consider both lattices in a perturbative framework, whereby the technique of Hamiltonian perturbation theory can be used to obtain information about the existence of solutions, and the same approach, as well as eigenvalue count considerations, can be used to obtain detailed conditions about their linear stability. We find that the analytical results are in very good agreement with our numerical findings and can also be used to predict features of the dynamical evolution of such solutions. A particularly interesting result of these considerations is the existence of a tunable cancellation effect between the linear and nonlinear lattices that allows for increased mobility of the solitary wave

The linear potential propagator via wave function expansion

International Nuclear Information System (INIS)

Nassar, Antonio B.; Cattani, Mauro S.D.

2002-01-01

We evaluate the quantum propagator for the motion of a particle in a linear potential via a recently developed formalism [A.B. Nassar et al., Phys. Rev. E56, 1230, (1997)]. In this formalism, the propagator comes about as a type of expansion of the wave function over the space of the initial velocities. (author)

Determination of wave direction from linear and polygonal arrays

Digital Repository Service at National Institute of Oceanography (India)

Fernandes, A.A; Gouveia, A; Nagarajan, R.

documentation of Borgman (1974) in case of linear arrays; and the second issue being the failure of Esteva (1976, 1977) to correctly determine wave directions over the design range 25 to 7 sec of his polygonal array. This paper presents requisite documentation...

Characterization of linear interfacial waves in a turbulent gas-liquid pipe flow

Science.gov (United States)

Ayati, A. A.; Farias, P. S. C.; Azevedo, L. F. A.; de Paula, I. B.

2017-06-01

The evolution of interfacial waves on a stratified flow was investigated experimentally for air-water flow in a horizontal pipe. Waves were introduced in the liquid level of stratified flow near the pipe entrance using an oscillating plate. The mean height of liquid layer and the fluctuations superimposed on this mean level were captured using high speed cameras. Digital image processing techniques were used to detect instantaneous interfaces along the pipe. The driving signal of the oscillating plate was controlled by a D/A board that was synchronized with acquisitions. This enabled to perform phase-locked acquisitions and to use ensemble average procedures. Thereby, it was possible to measure the temporal and spatial evolution of the disturbances introduced in the flow. In addition, phase-locked measurements of the velocity field in the liquid layer were performed using standard planar Particle Image Velocimetry (PIV). The velocity fields were extracted at a fixed streamwise location, whereas the measurements of the liquid level were performed at several locations along the pipe. The assessment of the setup was important for validation of the methodology proposed in this work, since it aimed at providing results for further comparisons with theoretical models and numerical simulations. Therefore, the work focuses on validation and characterization of interfacial waves within the linear regime. Results show that under controlled conditions, the wave development can be well captured and reproduced. In addition, linear waves were observed for liquid level oscillations lower than about 1.5% of the pipe diameter. It was not possible to accurately define an amplitude threshold for the appearance of nonlinear effects because it strongly depended on the wave frequency. According to the experimental findings, longer waves display characteristics similar to linear waves, while short ones exhibit a more complex evolution, even for low amplitudes.

Towards New Constraints in Extended Theories of Gravity: Cosmography and Gravitational-Wave Signals from Neutron Stars

Directory of Open Access Journals (Sweden)

Álvaro de la Cruz Dombriz

2018-02-01

Full Text Available Combined cosmological, astrophysical and numerical tests may shed some light on the viability of theories of gravity beyond Einsteinian relativity. In this letter, we present two different techniques providing complementary ways of testing new physics beyond the Λ CDM cosmological paradigm. First, we shall present some of the latest progress and shortcomings in the cosmographic model-independent approach for several modified gravity theories using supernovae catalogues, baryonic acoustic oscillation data and H ( z differential age compilations. Second, we shall show how once the Einsteinian paradigm is abandoned, the phenomenology of neutron stars changes dramatically since neutron-star masses can be much larger than their General Relativity counterparts. Consequently, the total energy available for radiating gravitational waves could be of the order of several solar masses, and thus a merger of these stars constitutes a privileged wave source. Unfortunately at the present time our persisting lack of understanding in the strong interaction sector does not allow to distinguish the alternative theories from the usual General Relativity predictions.

Studies of Gravity Waves Using Michelson Interferometer Measurements of OH (3-1) Bands

Science.gov (United States)

Won, Young-In; Cho, Young-Min; Lee, Bang Yong; Kim, J.

2001-06-01

As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH (3-1) bands were derived from spectrometric observations of airglow emissions over King Sejong station (62.22o S, 301.25o E). These measurements were made with a Michelson interferometer to cover wavelength regions between 1000 nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1) airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky's parameter and compared with published values.

Bouncing dynamics of Bose–Einstein condensates under the effects of gravity

Energy Technology Data Exchange (ETDEWEB)

Sekh, Golam Ali, E-mail: golamali.sekh@ba.infn.it [Department of Physics, University of Kashmir, Hazratbal, Srinagar-190006, J & K (India); Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, I-70126 Bari (Italy)

2017-03-03

Bouncing dynamics of quasi-one dimensional Bose–Einstein condensates (BECs) falling under gravity on delta-function potentials is investigated. First, we consider a single component BEC in the presence of cubic-quintic nonlinearity and study dynamical behavior of different parameters of the system using variational and numerical approaches. We see that the quintic nonlinearity plays a dominant role over cubic nonlinear interaction to extend the bouncing dynamics in the non-linear regime. We find that a matter-wave performs bouncing motion only for certain discrete values of initial position above the reflecting potential. We then consider bouncing dynamics of binary BECs. It is shown that the pair of matter-waves bounces together if inter-species interaction is attractive. However, their pairing breaks down if the inter-species interaction is made repulsive. - Highlights: • Single and coupled BECs • Effects of inter-component interaction and gravity • Periodic and quasi-periodic dynamics • Fermi-type acceleration.

Evidence for a continuous spectrum of equatorial waves in the Indian Ocean

Science.gov (United States)

Eriksen, Charles C.

1980-06-01

Seven-month records of current and temperature measurements from a moored array centered at 53°E on the equator in the Indian Ocean are consistent with a continuous spectrum of equatorially trapped internal inertial-gravity, mixed Rossby-gravity, and Kelvin waves. A model spectrum of free linear waves analogous to those for mid-latitude internal gravity waves is used to compute spectra of observed quantities at depths greater than about 2000 m. Model parameters are adjusted to fit general patterns in the observed spectra over periods from roughly 2 days to 1 month. Measurements at shallower depths presumably include forced motions which we have not attempted to model. This `straw-person' spectrum is consistent with the limited data available. The model spectru Ē (n, m, ω) = K · B(m) · C(n, ω), where Ē is an average local energy density in the equatorial wave guide which has amplitude K, wave number shape B(m) ∝ (1 + m/m*)-3, where m is vertical mode number and the bandwidth parameter m* is between 4 and 8, and frequency shape C(n, ω) ∝ [(2n + 1 + s2)½ · σ3]-1 where n is meridional mode number, and s and σ are dimensionless zonal wave number and frequency related by the usual dispersion relation. The scales are (β/cm)½ and (β · cm)½ for horizontal wave number and frequency, where cm is the Kelvin wave speed of the vertical mode m. At each frequency and vertical wave number, energy is partitioned equally among the available inertial gravity modes so that the field tends toward horizontal isotropy at high frequency. The transition between Kelvin and mixed Rossby-gravity motion at low frequency and inertial-gravity motion at high frequency occurs at a period of roughly 1 week. At periods in the range 1-3 weeks, the model spectrum which fits the observations suggests that mixed Rossby-gravity motion dominates; at shorter periods gravity motion dominates. The model results are consistent with the low vertical coherence lengths observed (roughly 80 m

A new active absorption system and its performance to linear and non-linear waves

DEFF Research Database (Denmark)

Andersen, Thomas Lykke; Clavero, M.; Frigaard, Peter Bak

2016-01-01

Highlights •An active absorption system for wavemakers has been developed. •The theory for flush mounted gauges has been extended to cover also small gaps. •The new system has been validated in a wave flume with wavemakers in both ends. •A generation and absorption procedure for highly non-linear...

Gravity Waves in the Martian Atmosphere detected by the Radio Science Experiment MaRS on Mars Express

Science.gov (United States)

Tellmann, S.; Pätzold, M.; Häusler, B.; Tyler, G. L.; Hinson, D. P.

2013-09-01

Gravity waves are an ubiquitous feature in all stably stratified planetary atmospheres. They are known to play a significant role in the energy and momentum budget of the Earth, and they are assumed to be of importance for the redistribution of energy and momentum throughout the Martian atmosphere.

Drake Antarctic Agile Meteor Radar (DrAAMER) First Results: Configuration and Comparison of Mean and Tidal Wind and Gravity Wave Momentum Flux Measurements with SAAMER

Science.gov (United States)

Fritts, D. C.; Janches, D.; Iimura, H.; Hocking, W. K.; Bageston, J. V.; Pene, N. M.

2011-01-01

A new-generation meteor radar was installed at the Brazilian Antarctic Comandante Ferraz Base (62.1degS) in March 2010. This paper describes the motivations for the radar location, its measurement capabilities, and comparisons of measured mean winds, tides, and gravity wave momentum fluxes from April to June of 2010 and 2011 with those by a similar radar on Tierra del Fuego (53.8degS). Motivations for the radars include the "hotspot" of small-scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere (MLT) centered over the Drake Passage, the maximum of the semidiurnal tide at these latitudes, and the lack of other MLT wind measurements in this latitude band. Mean winds are seen to be strongly modulated at planetary wave and longer periods and to exhibit strong coherence over the two radars at shorter time scales as well as systematic seasonal variations. The semidiurnal tide contribute most to the large-scale winds over both radars, with maximum tidal amplitudes during May and maxima at the highest altitudes varying from approx.20 to >70 m/s. In contrast, the diurnal tide and various planetary waves achieve maximum winds of approx.10 to 20 m/s. Monthly-mean gravity wave momentum fluxes appear to reflect the occurrence of significant sources at lower altitudes, with relatively small zonal fluxes over both radars, but with significant, and opposite, meridional momentum fluxes below approx.85 km. These suggest gravity waves propagating away from the Drake Passage at both sites, and may indicate an important source region accounting in part for this "hotspot".

An inhomogeneous wave equation and non-linear Diophantine approximation

DEFF Research Database (Denmark)

Beresnevich, V.; Dodson, M. M.; Kristensen, S.

2008-01-01

A non-linear Diophantine condition involving perfect squares and arising from an inhomogeneous wave equation on the torus guarantees the existence of a smooth solution. The exceptional set associated with the failure of the Diophantine condition and hence of the existence of a smooth solution...

Nonlinear and linear wave equations for propagation in media with frequency power law losses

Science.gov (United States)

Szabo, Thomas L.

2003-10-01

The Burgers, KZK, and Westervelt wave equations used for simulating wave propagation in nonlinear media are based on absorption that has a quadratic dependence on frequency. Unfortunately, most lossy media, such as tissue, follow a more general frequency power law. The authors first research involved measurements of loss and dispersion associated with a modification to Blackstock's solution to the linear thermoviscous wave equation [J. Acoust. Soc. Am. 41, 1312 (1967)]. A second paper by Blackstock [J. Acoust. Soc. Am. 77, 2050 (1985)] showed the loss term in the Burgers equation for plane waves could be modified for other known instances of loss. The authors' work eventually led to comprehensive time-domain convolutional operators that accounted for both dispersion and general frequency power law absorption [Szabo, J. Acoust. Soc. Am. 96, 491 (1994)]. Versions of appropriate loss terms were developed to extend the standard three nonlinear wave equations to these more general losses. Extensive experimental data has verified the predicted phase velocity dispersion for different power exponents for the linear case. Other groups are now working on methods suitable for solving wave equations numerically for these types of loss directly in the time domain for both linear and nonlinear media.

Multiband Circular Polarizer Based on Fission Transmission of Linearly Polarized Wave for X-Band Applications

Directory of Open Access Journals (Sweden)

Farman Ali Mangi

2016-01-01

Full Text Available A multiband circular polarizer based on fission transmission of linearly polarized wave for x-band application is proposed, which is constructed of 2 × 2 metallic strips array. The linear-to-circular polarization conversion is obtained by decomposing the linearly incident x-polarized wave into two orthogonal vector components of equal amplitude and 90° phase difference between them. The innovative approach of “fission transmission of linear-to-circular polarized wave” is firstly introduced to obtain giant circular dichroism based on decomposition of orthogonal vector components through the structure. It means that the incident linearly polarized wave is converted into two orthogonal components through lower printed metallic strips layer and two transmitted waves impinge on the upper printed strips layer to convert into four orthogonal vector components at the end of structure. This projection and transmission sequence of orthogonal components sustain the chain transmission of electromagnetic wave and can achieve giant circular dichroism. Theoretical analysis and microwave experiments are presented to validate the performance of the structure. The measured results are in good agreement with simulation results. In addition, the proposed circular polarizer exhibits the optimal performance with respect to the normal incidence. The right handed circularly polarized wave is emitted ranging from 10.08 GHz to 10.53 GHz and 10.78 GHz to 11.12 GHz, while the left handed circular polarized wave is excited at 10.54 GHz–10.70 GHz and 11.13 GHz–11.14 GHz, respectively.

Particle Dynamics under Quasi-linear Interaction with Electromagnetic Waves

Energy Technology Data Exchange (ETDEWEB)

Castejon, F.; Eguilior, S.

2003-07-01

Langevin equations for quasi-linear wave particle interaction are obtained taking advantage of the unique vocal equivalence between Fokker-Plank equation and the former ones. Langevin equations are solved numerically and, hence, the evolution of a single particle embedded in an electromagnetic field in momentum space is obtained. The equations are relativistic and valid for any wave. It is also shown that the stochastic part of the equations is negligible in comparison with the deterministic term, except for the momentum to the resonance condition for the main parallel refractive index. (Author) 24 refs.

Particle Dynamics under Quasi-linear Interaction with Electromagnetic Waves

International Nuclear Information System (INIS)

Castejon, F.; Eguilior, S.

2003-01-01

Langevin equations for quasi-linear wave particle interaction are obtained taking advantage of the unique vocal equivalence between Fokker-Plank equation and the former ones. Langevin equations are solved numerically and, hence, the evolution of a single particle embedded in an electromagnetic field in momentum space is obtained. The equations are relativistic and valid for any wave. It is also shown that the stochastic part of the equations is negligible in comparison with the deterministic term, except for the momentum to the resonance condition for the main parallel refractive index. (Author) 24 refs

Extracting gravity wave parameters during the September 2002 Southern Hemisphere major sudden stratospheric warming using a SANAE imaging riometer

Energy Technology Data Exchange (ETDEWEB)

Mbatha, N. [South African National Space Agency, Hermanus (South Africa). Space Science; KwaZulu-Natal Univ., Durban (South Africa). School of Chemistry and Physics; Sivakumar, V. [KwaZulu-Natal Univ., Durban (South Africa). School of Chemistry and Physics; Bencherif, H. [La Reunion Univ. UMR 8105 CNRS, Saint-Denis (France). Lab. de l' Atmosphere et des Cyclones; Malinga, S. [South African National Space Agency, Hermanus (South Africa). Space Science

2013-11-01

Using absorption data measured by imaging riometer for ionospheric studies (IRIS) located at the South Africa National Antarctic Expedition (SANAE), Antarctica (72 S, 3 W), we extracted the parameters of gravity waves (GW) of periods between 40 and 50 min during late winter/ spring of the year 2002, a period of the unprecedented major sudden stratospheric warming (SSW) in the Southern Hemisphere middle atmosphere. During this period, an unprecedented substantial increase of temperature by about 25-30K throughout the stratosphere was observed. During the period of the occurrence of the major stratospheric warming, there was a reduction of both the GW horizontal phase speeds and the horizontal wavelengths at 90 km. The GW phase speeds and horizontal wavelengths were observed to reach minimum values of about 7ms{sup -1} and 19 km, respectively, while during the quiet period the average value of the phase speed and horizontal wavelength was approximately 23ms{sup -1} and 62 km, respectively. The observed event is discussed in terms of momentum flux and also a potential interaction of gravity waves, planetary waves and mean circulation.

A numerical model for ocean ultra-low frequency noise: wave-generated acoustic-gravity and Rayleigh modes.

Science.gov (United States)

Ardhuin, Fabrice; Lavanant, Thibaut; Obrebski, Mathias; Marié, Louis; Royer, Jean-Yves; d'Eu, Jean-François; Howe, Bruce M; Lukas, Roger; Aucan, Jerome

2013-10-01

The generation of ultra-low frequency acoustic noise (0.1 to 1 Hz) by the nonlinear interaction of ocean surface gravity waves is well established. More controversial are the quantitative theories that attempt to predict the recorded noise levels and their variability. Here a single theoretical framework is used to predict the noise level associated with propagating pseudo-Rayleigh modes and evanescent acoustic-gravity modes. The latter are dominant only within 200 m from the sea surface, in shallow or deep water. At depths larger than 500 m, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii and the Kerguelen islands reveal: (a) Deep ocean acoustic noise at frequencies 0.1 to 1 Hz is consistent with the Rayleigh wave theory, in which the presence of the ocean bottom amplifies the noise by 10 to 20 dB; (b) in agreement with previous results, the local maxima in the noise spectrum support the theoretical prediction for the vertical structure of acoustic modes; and (c) noise level and variability are well predicted for frequencies up to 0.4 Hz. Above 0.6 Hz, the model results are less accurate, probably due to the poor estimation of the directional properties of wind-waves with frequencies higher than 0.3 Hz.

Linear and Nonlinear MHD Wave Processes in Plasmas. Final Report

International Nuclear Information System (INIS)

Tataronis, J. A.

2004-01-01

This program treats theoretically low frequency linear and nonlinear wave processes in magnetized plasmas. A primary objective has been to evaluate the effectiveness of MHD waves to heat plasma and drive current in toroidal configurations. The research covers the following topics: (1) the existence and properties of the MHD continua in plasma equilibria without spatial symmetry; (2) low frequency nonresonant current drive and nonlinear Alfven wave effects; and (3) nonlinear electron acceleration by rf and random plasma waves. Results have contributed to the fundamental knowledge base of MHD activity in symmetric and asymmetric toroidal plasmas. Among the accomplishments of this research effort, the following are highlighted: Identification of the MHD continuum mode singularities in toroidal geometry. Derivation of a third order ordinary differential equation that governs nonlinear current drive in the singular layers of the Alfven continuum modes in axisymmetric toroidal geometry. Bounded solutions of this ODE implies a net average current parallel to the toroidal equilibrium magnetic field. Discovery of a new unstable continuum of the linearized MHD equation in axially periodic circular plasma cylinders with shear and incompressibility. This continuum, which we named ''accumulation continuum'' and which is related to ballooning modes, arises as discrete unstable eigenfrequency accumulate on the imaginary frequency axis in the limit of large mode numbers. Development of techniques to control nonlinear electron acceleration through the action of multiple coherent and random plasmas waves. Two important elements of this program aye student participation and student training in plasma theory

The Gravity of Photons and the Necessary Rectification of Einstein Equation

Directory of Open Access Journals (Sweden)

Lo C. Y.

2006-01-01

Full Text Available It is pointed out that Special Relativity together with the principle of causality implies that the gravity of an electromagnetic wave is an accompanying gravitational wave propagating with the same speed. Since a gravitational wave carries energy-momentum, this accompanying wave would make the energy-stress tensor of the light to be different from the electromagnetic energy-stress tensor, and thus can produce a geodesic equation for the photons. Moreover, it is found that the appropriate Einstein equation must additionally have the photonic energy-stress tensor with the antigravity coupling in the source term. This would correct that, in disagreement with the calculations for the bending of light, existing solutions of gravity for an electromagnetic wave, is unbounded. This rectification is confirmed by calculating the gravity of electromagnetic plane-waves. The gravity of an electromagnetic wave is indeed an accompanying gravitational wave. Moreover, these calculations show the first time that Special Relativity and General Relativity are compatible because the physical meaning of coordinates has been clarified. The success of this rectification makes General Relativity standing out further among theories of gravity.

Extreme gravity tests with gravitational waves from compact binary coalescences: (II) ringdown

Science.gov (United States)

Berti, Emanuele; Yagi, Kent; Yang, Huan; Yunes, Nicolás

2018-05-01

The LIGO/Virgo detections of binary black hole mergers marked a watershed moment in astronomy, ushering in the era of precision tests of Kerr dynamics. We review theoretical and experimental challenges that must be overcome to carry out black hole spectroscopy with present and future gravitational wave detectors. Among other topics, we discuss quasinormal mode excitation in binary mergers, astrophysical event rates, tests of black hole dynamics in modified theories of gravity, parameterized "post-Kerr" ringdown tests, exotic compact objects, and proposed data analysis methods to improve spectroscopic tests of Kerr dynamics by stacking multiple events.

Analyses of the stratospheric dynamics simulated by a GCM with a stochastic nonorographic gravity wave parameterization

Science.gov (United States)

Serva, Federico; Cagnazzo, Chiara; Riccio, Angelo

2016-04-01

The effects of the propagation and breaking of atmospheric gravity waves have long been considered crucial for their impact on the circulation, especially in the stratosphere and mesosphere, between heights of 10 and 110 km. These waves, that in the Earth's atmosphere originate from surface orography (OGWs) or from transient (nonorographic) phenomena such as fronts and convective processes (NOGWs), have horizontal wavelengths between 10 and 1000 km, vertical wavelengths of several km, and frequencies spanning from minutes to hours. Orographic and nonorographic GWs must be accounted for in climate models to obtain a realistic simulation of the stratosphere in both hemispheres, since they can have a substantial impact on circulation and temperature, hence an important role in ozone chemistry for chemistry-climate models. Several types of parameterization are currently employed in models, differing in the formulation and for the values assigned to parameters, but the common aim is to quantify the effect of wave breaking on large-scale wind and temperature patterns. In the last decade, both global observations from satellite-borne instruments and the outputs of very high resolution climate models provided insight on the variability and properties of gravity wave field, and these results can be used to constrain some of the empirical parameters present in most parameterization scheme. A feature of the NOGW forcing that clearly emerges is the intermittency, linked with the nature of the sources: this property is absent in the majority of the models, in which NOGW parameterizations are uncoupled with other atmospheric phenomena, leading to results which display lower variability compared to observations. In this work, we analyze the climate simulated in AMIP runs of the MAECHAM5 model, which uses the Hines NOGW parameterization and with a fine vertical resolution suitable to capture the effects of wave-mean flow interaction. We compare the results obtained with two

The MaCWAVE program to study gravity wave influences on the polar mesosphere

Directory of Open Access Journals (Sweden)

R. A. Goldberg

2006-07-01

Full Text Available MaCWAVE (Mountain and Convective Waves Ascending VErtically was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT. The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite measurements of thermal structures. The data have been used to define both the mean fields and the wave field structures and turbulence generation leading to forcing of the large-scale flow. In summer, launch sequences coupled with ground-based measurements at ARR addressed the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. These motions were measured with two 12-h rocket sequences, each involving one Terrier-Orion payload accompanied by a mix of MET rockets, all at ARR in Norway. The MET rockets were used to define the temperature and wind structure of the stratosphere and mesosphere. The Terrier-Orions were designed to measure small-scale plasma fluctuations and turbulence that might be induced by wave breaking in the mesosphere. For the summer series, three European MIDAS (Middle Atmosphere Dynamics and Structure rockets were also launched from ARR in coordination with the MaCWAVE payloads. These were designed to measure plasma and neutral turbulence within the MLT. The summer program exhibited a number of indications of significant departures of the mean wind and temperature structures from ``normal" polar summer conditions, including an unusually warm mesopause and a slowing of the formation of polar mesospheric summer echoes (PMSE and noctilucent clouds (NLC. This

A case study of the energy dissipation of the gravity wave field based on satellite altimeter measurements

Science.gov (United States)

Huang, N. E.; Parsons, C. L.; Long, S. R.; Bliven, L. F.

1983-01-01

Wave breaking is proposed as the primary energy dissipation mechanism for the gravity wave field. The energy dissipation rate is calculated based on the statistical model proposed by Longuet-Higgins (1969) with a modification of the breaking criterion incorporating the surface stress according to Phillips and Banner (1974). From this modified model, an analytic expression is found for the wave attenuation rate and the half-life time of the wave field which depend only on the significant slope of the wave field and the ratio of friction velocity to initial wave phase velocity. These expressions explain why the freshly generated wave field does not last long, but why swells are capable of propagating long distances without substantial change in energy density. It is shown that breaking is many orders of magnitude more effective in dissipating wave energy than the molecular viscosity, if the significant slope is higher than 0.01. Limited observational data from satellite and laboratory are used to compare with the analytic results, and show good agreement.

Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

Directory of Open Access Journals (Sweden)

Q. T. Trinh

2018-03-01

Full Text Available Atmospheric gravity waves (GWs are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30–90 km and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE and CHAllenging Minisatellite Payload (CHAMP satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above. Two coupling mechanisms are likely responsible for these positive correlations: (1 fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2 primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude–longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also

Satellite observations of middle atmosphere-thermosphere vertical coupling by gravity waves

Science.gov (United States)

Trinh, Quang Thai; Ern, Manfred; Doornbos, Eelco; Preusse, Peter; Riese, Martin

2018-03-01

Atmospheric gravity waves (GWs) are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I) system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30-90 km) and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE) and CHAllenging Minisatellite Payload (CHAMP) satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km) and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above). Two coupling mechanisms are likely responsible for these positive correlations: (1) fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2) primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude-longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also propagate up to the T

Generating gravity waves with matter and electromagnetic waves

International Nuclear Information System (INIS)

Barrabes, C.; Hogan, P A.

2008-01-01

If a homogeneous plane lightlike shell collides head on with a homogeneous plane electromagnetic shock wave having a step-function profile then no backscattered gravitational waves are produced. We demonstrate, by explicit calculation, that if the matter is accompanied by a homogeneous plane electromagnetic shock wave with a step-function profile then backscattered gravitational waves appear after the collision

Diffusion phenomenon for linear dissipative wave equations in an exterior domain

Science.gov (United States)

Ikehata, Ryo

Under the general condition of the initial data, we will derive the crucial estimates which imply the diffusion phenomenon for the dissipative linear wave equations in an exterior domain. In order to derive the diffusion phenomenon for dissipative wave equations, the time integral method which was developed by Ikehata and Matsuyama (Sci. Math. Japon. 55 (2002) 33) plays an effective role.

Linear waves on higher dimensional Schwarzschild black holes and Schwarzschild de Sitter spacetimes

OpenAIRE

Schlue, Volker

2012-01-01

I study linear waves on higher dimensional Schwarzschild black holes and Schwarzschild de Sitter spacetimes. In the first part of this thesis two decay results are proven for general finite energy solutions to the linear wave equation on higher dimensional Schwarzschild black holes. I establish uniform energy decay and improved interior first order energy decay in all dimensions with rates in accordance with the 3 + 1-dimensional case. The method of proof departs from earlier work on th...

Cutoff for extensions of massive gravity and bi-gravity

International Nuclear Information System (INIS)

Matas, Andrew

2016-01-01

Recently there has been interest in extending ghost-free massive gravity, bi-gravity, and multi-gravity by including non-standard kinetic terms and matter couplings. We first review recent proposals for this class of extensions, emphasizing how modifications of the kinetic and potential structure of the graviton and modifications of the coupling to matter are related. We then generalize existing no-go arguments in the metric language to the vielbein language in second-order form. We give an ADM argument to show that the most promising extensions to the kinetic term and matter coupling contain a Boulware–Deser ghost. However, as recently emphasized, we may still be able to view these extensions as effective field theories below some cutoff scale. To address this possibility, we show that there is a decoupling limit where a ghost appears for a wide class of matter couplings and kinetic terms. In particular, we show that there is a decoupling limit where the linear effective vielbein matter coupling contains a ghost. Using the insight we gain from this decoupling limit analysis, we place an upper bound on the cutoff for the linear effective vielbein coupling. This result can be generalized to new kinetic interactions in the vielbein language in second-order form. Combined with recent results, this provides a strong uniqueness argument on the form of ghost-free massive gravity, bi-gravity, and multi-gravity. (paper)

Studies of Gravity Waves Using Michelson Interferometer Measurements of OH (3-1 Bands

Directory of Open Access Journals (Sweden)

Young-In Won

2001-06-01

Full Text Available As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH (3-1 bands were derived from spectrometric observations of airglow emissions over King Sejong station (62.22o S, 301.25o E. These measurements were made with a Michelson interferometer to cover wavelength regions between 1000 nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1 airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky's parameter and compared with published values.

Secondary gravity waves from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere

Science.gov (United States)

Vadas, S.

2017-12-01

In this paper, we investigate the generation, propagation and effectsof secondary gravity waves (GWs) from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere in high-resolution GW-resolving models and in TEC/lidar/redline data. We show that secondary GWs generated from the dissipation of orographic GWs at McMurdo Station in Antarctica play a dominant role in the wave activity over McMurdo in the wintertime mesosphere. These secondary GWs are created in the stratosphere, and have been identified in models and data via their telltale "fishbone" appearance in z-t plots. We also show that secondary GWs from the dissipation of GWs excited by deep convectiongenerate concentric rings in the F-region ionosphere. These model results and data point to the importance of secondary GWs from momentumdeposition in the Earth's atmosphere and ionosphere.

Non-linear dynamo waves in an incompressible medium when the turbulence dissipative coefficients depend on temperature

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A. D. Pataraya

1997-01-01

Full Text Available Non-linear α-ω; dynamo waves existing in an incompressible medium with the turbulence dissipative coefficients depending on temperature are studied in this paper. We investigate of α-ω solar non-linear dynamo waves when only the first harmonics of magnetic induction components are included. If we ignore the second harmonics in the non-linear equation, the turbulent magnetic diffusion coefficient increases together with the temperature, the coefficient of turbulent viscosity decreases, and for an interval of time the value of dynamo number is greater than 1. In these conditions a stationary solution of the non-linear equation for the dynamo wave's amplitude exists; meaning that the magnetic field is sufficiently excited. The amplitude of the dynamo waves oscillates and becomes stationary. Using these results we can explain the existence of Maunder's minimum.

Quantum gravito-optics: a light route from semiclassical gravity to quantum gravity

International Nuclear Information System (INIS)

Unnikrishnan, C S; Gillies, George T

2015-01-01

Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation, ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for the detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitational optics can assist in guiding along the fuzzy roads to quantum gravity. (paper)

Variations of global gravity waves derived from 14 years of SABER temperature observations

Science.gov (United States)

Liu, Xiao; Yue, Jia; Xu, Jiyao; Garcia, Rolando R.; Russell, James M.; Mlynczak, Martin; Wu, Dong L.; Nakamura, Takuji

2017-06-01

The global gravity wave (GW) potential energy (PE) per unit mass is derived from SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) temperature profiles over the past 14 years (2002-2015). Since the SABER data cover longer than one solar cycle, multivariate linear regression is applied to calculate the trend (means linear trend from 2002 to 2015) of global GW PE and the responses of global GW PE to solar activity, to QBO (quasi-biennial oscillation) and to ENSO (El Niño-Southern Oscillation). We find a significant positive trend of GW PE at around 50°N during July from 2002 to 2015, in agreement with ground-based radar observations at a similar latitude but from 1990 to 2010. Both the monthly and the deseasonalized trends of GW PE are significant near 50°S. Specifically, the deseasonalized trend of GW PE has a positive peak of 12-15% per decade at 40°S-50°S and below 60 km, which suggests that eddy diffusion is increasing in some places. A significant positive trend of GW PE near 50°S could be due to the strengthening of the polar stratospheric jets, as documented from Modern Era Retrospective-analysis for Research and Applications wind data. The response of GW PE to solar activity is negative in the lower and middle latitudes. The response of GW PE to QBO (as indicated by 30 hPa zonal winds over the equator) is negative in the tropical upper stratosphere and extends to higher latitudes at higher altitudes. The response of GW PE to ENSO (as indicated by the Multivariate ENSO Index) is positive in the tropical upper stratosphere.

Relationship Between the Parameters of the Linear and Nonlinear Wave Generation Stages in a Magnetospheric Cyclotron Maser in the Backward-Wave Oscillator Regime

Science.gov (United States)

Demekhov, A. G.

2017-03-01

By using numerical simulations we generalize certain relationships between the parameters of quasimonochromatic whistler-mode waves generated at the linear and nonlinear stages of the cyclotron instability in the backward-wave oscillator regime. One of these relationships is between the wave amplitude at the nonlinear stage and the linear growth rate of the cyclotron instability. It was obtained analytically by V.Yu.Trakhtengerts (1984) for a uniform medium under the assumption of constant frequency and amplitude of the generated wave. We show that a similar relationship also holds for the signals generated in a nonuniform magnetic field and having a discrete structure in the form of short wave packets (elements) with fast frequency drift inside each element. We also generalize the formula for the linear growth rate of absolute cyclotron instability in a nonuniform medium and analyze the relationship between the frequency drift rate in the discrete elements and the wave amplitude. These relationships are important for analyzing the links between the parameters of chorus emissions in the Earth's and planetary magnetospheres and the characteristics of the energetic charged particles generating these signals.

Gravity inversion code

International Nuclear Information System (INIS)

Burkhard, N.R.

1979-01-01

The gravity inversion code applies stabilized linear inverse theory to determine the topography of a subsurface density anomaly from Bouguer gravity data. The gravity inversion program consists of four source codes: SEARCH, TREND, INVERT, and AVERAGE. TREND and INVERT are used iteratively to converge on a solution. SEARCH forms the input gravity data files for Nevada Test Site data. AVERAGE performs a covariance analysis on the solution. This document describes the necessary input files and the proper operation of the code. 2 figures, 2 tables

Modelization of highly nonlinear waves in coastal regions

Science.gov (United States)

Gouin, Maïté; Ducrozet, Guillaume; Ferrant, Pierre

2015-04-01

The proposed work deals with the development of a highly non-linear model for water wave propagation in coastal regions. The accurate modelization of surface gravity waves is of major interest in ocean engineering, especially in the field of marine renewable energy. These marine structures are intended to be settled in coastal regions where the effect of variable bathymetry may be significant on local wave conditions. This study presents a numerical model for the wave propagation with complex bathymetry. It is based on High-Order Spectral (HOS) method, initially limited to the propagation of non-linear wave fields over flat bottom. Such a model has been developed and validated at the LHEEA Lab. (Ecole Centrale Nantes) over the past few years and the current developments will enlarge its application range. This new numerical model will keep the interesting numerical properties of the original pseudo-spectral approach (convergence, efficiency with the use of FFTs, …) and enable the possibility to propagate highly non-linear wave fields over long time and large distance. Different validations will be provided in addition to the presentation of the method. At first, Bragg reflection will be studied with the proposed approach. If the Bragg condition is satisfied, the reflected wave generated by a sinusoidal bottom patch should be amplified as a result of resonant quadratic interactions between incident wave and bottom. Comparisons will be provided with experiments and reference solutions. Then, the method will be used to consider the transformation of a non-linear monochromatic wave as it propagates up and over a submerged bar. As the waves travel up the front slope of the bar, it steepens and high harmonics are generated due to non-linear interactions. Comparisons with experimental data will be provided. The different test cases will assess the accuracy and efficiency of the method proposed.

Designing and Testing Composite Energy Storage Systems for Regulating the Outputs of Linear Wave Energy Converters

Directory of Open Access Journals (Sweden)

Zanxiang Nie

2017-01-01

Full Text Available Linear wave energy converters generate intrinsically intermittent power with variable frequency and amplitude. A composite energy storage system consisting of batteries and super capacitors has been developed and controlled by buck-boost converters. The purpose of the composite energy storage system is to handle the fluctuations and intermittent characteristics of the renewable source, and hence provide a steady output power. Linear wave energy converters working in conjunction with a system composed of various energy storage devices, is considered as a microsystem, which can function in a stand-alone or a grid connected mode. Simulation results have shown that by applying a boost H-bridge and a composite energy storage system more power could be extracted from linear wave energy converters. Simulation results have shown that the super capacitors charge and discharge often to handle the frequent power fluctuations, and the batteries charge and discharge slowly for handling the intermittent power of wave energy converters. Hardware systems have been constructed to control the linear wave energy converter and the composite energy storage system. The performance of the composite energy storage system has been verified in experiments by using electronics-based wave energy emulators.

Dispersion relation of linearly polarized strong electromagnetic waves

Energy Technology Data Exchange (ETDEWEB)

Ferrari, A; Massaglia, S [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Dobrowolny, M [Comitato Nazionale per l' Energia Nucleaire, Frascati (Italy). Lab. Plasma Spazio

1975-12-15

A numerical study is presented of the dispersion relation of linearly polarized strong electromagnetic waves in a cold electron plasma. The nonlinear effects introduced by the relativistic motion of electrons are: (1) the dispersion relation depends explicitly on the field strength ..cap alpha..=eE/sub 0//mc..omega../sub 0/, and (2) the propagation of modes with frequencies below the formal electron plasma frequency is allowed.