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Academic literature on the topic 'VLF atmosphere'

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Published: 6 September 2023

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Journal articles on the topic "VLF atmosphere"

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Biswas, Sagardweep, Subrata Kundu, Sudipta Sasmal, Dimitrios Z. Politisb, Stelios M. Potirakis, and Masashi Hayakawa. "Preseismic Perturbations and their Inhomogeneity as Computed from Ground- and Space-Based Investigation during the 2016 Fukushima Earthquake." Journal of Sensors 2023 (February 24, 2023): 1–23. http://dx.doi.org/10.1155/2023/7159204.

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We present the atmospheric anomalies instigated through seismogenic sources by a multichannel observation using ground- and satellite-based systems. This study emphasizes the seismic event which happened on the east coast of Japan, near the Fukushima Prefecture on November 21, 2016 (in UTC), with a magnitude of 6.9 and a depth of 11.4 km. We mainly focus on the atmospheric and ionospheric irregularities via acoustic and electromagnetic channels originating from earthquakes in the process of the lithosphere, atmosphere, and ionospheric coupling (LAIC) mechanism. In the acoustic channel, we study the seismogenic atmospheric gravity wave (AGW) which perturbs the local lower atmosphere. The observation of nighttime fluctuations in the very low frequency (VLF) signals and total electron content (TEC) is used to investigate the atmospheric perturbation through the electromagnetic channel. For the ground-based observations, a VLF signal network consisting of 5 receivers in Japan is used to study by recording the VLF amplitude transmitted from the Japanese transmitter JJI (22.2 kHz). VLF nighttime fluctuation is used to check the unusualities due to the earthquake. Preseismic wavelike structures having periods of AGW are observed in the nighttime signal. Direct investigation of such AGWs is done by computing the potential energy related to AGW from the sounding of the atmosphere using broadband emission radiometry (SABER) temperature profiles mounted on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. Ionospheric TEC inspection is done by using a ground-based global navigation satellite system (GNSS) receiver from the International GNSS Survey (IGS) station MIZU in Japan and observing anomalies in diurnal TEC around 6 and 10 days prior to the earthquake. We also obtain the wavelike structure of AGW from the small-scale fluctuation of TEC using wavelet analysis. All the parameters are found to be preseismic for this earthquake; the acoustics channel gives more consistent outcomes than the electromagnetic channel.
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Kachakhidze, M. K., Z. A. Kereselidze, and N. K. Kachakhidze. "The model of own seismoelectromagnetic oscillations of LAI system." Solid Earth Discussions 2, no. 2 (July 26, 2010): 233–50. http://dx.doi.org/10.5194/sed-2-233-2010.

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Abstract. Very low frequency (VLF) electromagnetic radiation (in diapason 1 kHz – 1 MHz) in atmosphere, generated during earthquake preparation period, may be connected with linear size, characterizing incoming earthquake source. In order to argue this hypothesis very simple quasi-electrostatic model is used: local VLF radiation may be the manifestation of own electromagnetic oscillations of concrete seismoactive segments of lithosphere-atmosphere system. This model explains qualitatively well-known precursor effects of earthquakes. At the same time, it will be principally possible to forecast expected earthquake with certain precision if we use this model after diagnosing existed data. As physical basis of working hypothesis is atmospheric effect of polarization charges occurred in surface layer of the Earth, it is possible to test the below constructed model in medium, where reasons of polarization charge generation may be different from piezoelectric mechanism, for example, due to electrolytic hydration.
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Kachakhidze, M. K., Z. A. Kereselidze, and N. K. Kachakhidze. "The model of self-generated seismo-electromagnetic oscillations of the LAI system." Solid Earth 2, no. 1 (February 8, 2011): 17–23. http://dx.doi.org/10.5194/se-2-17-2011.

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Abstract. Very low frequency (VLF) electromagnetic radiation (in diapason 1 kHz–1 MHz) in the atmosphere, generated during an earthquake preparation period, may be connected with the linear size characterising the expected earthquake focus. In order to argue this hypothesis, a very simple quasi-electrostatic model is used: the local VLF radiation may represent the self-generated (own) electromagnetic oscillations of interactive seismoactive segments of the lithosphere-atmosphere system. This model qualitatively explains the well-known precursor effects of earthquakes. In addition, using this model after diagnosing existing data makes it principally possible to forecast an expected earthquake with certain precision. As a physical basis of the working hypothesis is the atmospheric effect of polarization charges occurring in the surface layer of the Earth, it is possible to test the following constructed model in the Earth's crust, where the reason for polarization charge generation may be different from piezo-electric mechanism, e.g., some other mechanism.
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Buchanan, Weston P., Maxim de Jong, Rachana Agrawal, Janusz J. Petkowski, Archit Arora, Sarag J. Saikia, Sara Seager, and James Longuski. "Aerial Platform Design Options for a Life-Finding Mission at Venus." Aerospace 9, no. 7 (July 7, 2022): 363. http://dx.doi.org/10.3390/aerospace9070363.

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Mounting evidence of chemical disequilibria in the Venusian atmosphere has heightened interest in the search for life within the planet’s cloud decks. Balloon systems are currently considered to be the superior class of aerial platform for extended atmospheric sampling within the clouds, providing the highest ratio of science return to risk. Balloon-based aerial platform designs depend heavily on payload mass and target altitudes. We present options for constant- and variable-altitude balloon systems designed to carry out science operations inside the Venusian cloud decks. The Venus Life Finder (VLF) mission study proposes a series of missions that require extended in situ analysis of Venus cloud material. We provide an overview of a representative mission architecture, as well as gondola designs to accommodate a VLF instrument suite. Current architecture asserts a launch date of 30 July 2026, which would place an orbiter and entry vehicle at Venus as early as November 29 of that same year.
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Zhao, Shufan, Xuhui Shen, Weiyan Pan, Xuemin Zhang, and Li Liao. "Penetration characteristics of VLF wave from atmosphere into lower ionosphere." Earthquake Science 23, no. 3 (June 2010): 275–81. http://dx.doi.org/10.1007/s11589-010-0723-9.

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Rodger, C. J., M. A. Clilverd, N. R. Thomson, D. Nunn, and J. Lichtenberger. "Lightning driven inner radiation belt energy deposition into the atmosphere: regional and global estimates." Annales Geophysicae 23, no. 11 (December 21, 2005): 3419–30. http://dx.doi.org/10.5194/angeo-23-3419-2005.

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Abstract. In this study we examine energetic electron precipitation fluxes driven by lightning, in order to determine the global distribution of energy deposited into the middle atmosphere. Previous studies using lightning-driven precipitation burst rates have estimated losses from the inner radiation belts. In order to confirm the reliability of those rates and the validity of the conclusions drawn from those studies, we have analyzed New Zealand data to test our global understanding of troposphere to magnetosphere coupling. We examine about 10000h of AbsPAL recordings made from 17 April 2003 through to 26 June 2004, and analyze subionospheric very-low frequency (VLF) perturbations observed on transmissions from VLF transmitters in Hawaii (NPM) and western Australia (NWC). These observations are compared with those previously reported from the Antarctic Peninsula. The perturbation rates observed in the New Zealand data are consistent with those predicted from the global distribution of the lightning sources, once the different experimental configurations are taken into account. Using lightning current distributions rather than VLF perturbation observations we revise previous estimates of typical precipitation bursts at L~2.3 to a mean precipitation energy flux of ~1×10-3 ergs cm-2s-1. The precipitation of energetic electrons by these bursts in the range L=1.9-3.5 will lead to a mean rate of energy deposited into the atmosphere of 3×10-4 ergs cm-2min-1, spatially varying from a low of zero above some ocean regions to highs of ~3-6×10-3 ergs cm-2min-1 above North America and its conjugate region.
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Zhao, Shufan, Xuhui Sheng, Weiyan Pan, and Xuemin Zhang. "Penetration characteristics of VLF wave from atmosphere into the lower ionosphere." Chinese Journal of Space Science 31, no. 2 (2011): 194. http://dx.doi.org/10.11728/cjss2011.02.194.

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Srećković, Vladimir A., Desanka M. Šulić, Ljubinko Ignjatović, and Veljko Vujčić. "Low Ionosphere under Influence of Strong Solar Radiation: Diagnostics and Modeling." Applied Sciences 11, no. 16 (August 4, 2021): 7194. http://dx.doi.org/10.3390/app11167194.

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Solar flares (SFs) and intense radiation can generate additional ionization in the Earth’s atmosphere and affect its structure. These types of solar radiation and activity create sudden ionospheric disturbances (SIDs), affect electronic equipment on the ground along with signals from space, and potentially induce various natural disasters. Focus of this work is on the study of SIDs induced by X-ray SFs using very low frequency (VLF) radio signals in order to predict the impact of SFs on Earth and analyze ionosphere plasmas and its parameters. All data are recorded by VLF BEL stations and the model computation is used to obtain the daytime atmosphere parameters induced by this extreme radiation. The obtained ionospheric parameters are compared with results of other authors. For the first time we analyzed physics of the D-region—during consecutive huge SFs which continuously perturbed this layer for a few hours—in detail. We have developed an empirical model of the D-region plasma density and gave a simple approximative formula for electron density.
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Silber, Israel, Colin Price, and Craig J. Rodger. "Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers." Atmospheric Chemistry and Physics 16, no. 5 (March 14, 2016): 3279–88. http://dx.doi.org/10.5194/acp-16-3279-2016.

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Abstract. Earth's middle and upper atmosphere exhibits several dominant large-scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere–lower thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequency (VLF) narrowband (NB) subionospheric measurements. As VLF signals are reflected off the ionospheric D region (at altitudes of ∼ 65 and ∼ 85 km, during the day and night, respectively), this implies that the upper part of the D region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D region is NOx molecule transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D region in general and VLF wave propagation in particular.
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Silber, I., C. G. Price, and C. J. Rodger. "Semi-annual oscillation (SAO) of the nighttime ionospheric D-region as detected through ground-based VLF receivers." Atmospheric Chemistry and Physics Discussions 15, no. 21 (November 4, 2015): 30383–407. http://dx.doi.org/10.5194/acpd-15-30383-2015.

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Abstract. Earth's middle and upper atmosphere exhibits several dominant large scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere-lower-thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequencies (VLF) narrow-band subionospheric measurements. As VLF signals are reflected off the ionospheric D-region (at altitudes of ~65 and ~85 km, during the day and night, respectively), this implies that the upper part of the D-region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D-region is due to NOx molecules transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D-region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D-region in general and VLF wave propagation in particular.
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Dissertations / Theses on the topic "VLF atmosphere"

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Groves, Keith Michael. "Nonlinear ionospheric propagation effects on UHF and VLF radio signals." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/52949.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.
Includes bibliographical references (p. 179-184).
by Keith Michael Groves.
Ph.D.
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Low, David J. "Studies of the lower atmosphere with a VHF wind profiler /." Title page, abstract and contents only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phl9121.pdf.

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Culbertson, Gary W. "Assessments of atmospheric affects of VHF and UHF communications." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA226661.

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Thesis (M.S. in Telecommunication Systems Management)--Naval Postgraduate School, March 1990.
Thesis Advisor(s): Davidson, Kenneth L. Second Reader: Tulloch, A. W. "March 1990." Description based on signature page as viewed on August 26, 2009. DTIC Descriptor(s): Atmospheric Refraction, Very High Frequency, Ultrahigh Frequency, Communication And Radio Systems, Tools, Parameters, Wind, Forecasting, Accuracy, Theses, Electromagnetic Radiation, Pressure, Radiosondes, Refraction, Pacific Ocean, Climatology, Troposphere, Humidity, Gradients, Shores, East(Direction), Computer Printouts, Television Display Systems, Weather, Guided Missiles, Synoptic Meteorology, Test And Evaluation, Data Bases. DTIC Identifier(s): IREPS (Integrated Refractive Effect Prediction System). Author(s) subject terms: Communications, IREPS, refraction. Includes bibliographical references (p. 70-71). Also available online.
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Campos, Ortega Edwin F. 1972. "Analyses of precipitation signal using VHF vertically-pointing radar." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102965.

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In addition to a proper radar calibration, quantitative estimation of precipitation from VHF radars requires the extraction of the precipitation signal out of the Doppler spectra. It also requires the proper conversion of this precipitation signal into a reflectivity factor.
This research develops a multi-faceted approach for the calibration of VHF vertically-pointing radars, by combining a first calibration method that compares the recorded VHF signal to power coming from a noise generator and a second calibration method that compares recorded VHF signal to cosmic radiation. This approach allows the retrieval of antenna and receiver parameters (such as noise levels, efficiency, and gain), and four other equations for the corresponding errors. In addition, we develop an equation for calibrating Doppler spectra.
The analysis is focused on rain observations with VHF radar. We verify the hypothesis that |K|2 = 0.93 for most of the rain observations at VHF band. A signal-processing algorithm for extracting the rain signal out of the VHF power spectra is then presented. This work also derives a general version of the radar equation valid for vertically pointing radars, as well as a particular version of this equation valid for the McGill VHF radar. The study then makes numerical simulations of several profiles of precipitation signal at VHF band, by combining high-resolution profiles of precipitation signal (from a calibrated X-band radar) and the VHF antenna pattern in our general version of the radar equation. The analyses indicate that VHF reflectivity at gates above the melting layer is artificially enhanced by the precipitation signal collected from the side lobes.
This work also studies the effect of precipitation in the scattering properties of clear air. We analyze several cases of stratiform and convective rain, occurring in a continental mid-latitude environment (Montreal, Lat.45.41°N, Long.73.94°W). For these cases, Doppler spectra taken by a VHF vertically-pointing radar were used to retrieve simultaneous co-located values of precipitation intensity (rainrates) and degrees of refractive index fluctuation (structure-function parameter for refractivity turbulence, Cn2). We validated these retrievals using co-located, calibrated measurements of precipitation signal at X-band. The comparison between equivalent reflectivity factors at X and VHF bands agrees within 1 dB. The study includes rainrates between 0.3 and 78 mm/h, and Cn2 values between 10-16 and 10-12 m-2/3 , retrieved from the VHF spectra at 2.5 km height. The study finds that the occurrence of rain is associated with distinctive changes in the structure of air refractive index fluctuations, and that these changes are of a turbulent nature for the most intense rainrates.
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Beldon, Charlotte. "VHF radar studies of mesosphere and thermosphere." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512294.

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Mu, K. L. "Investigation of tropospheric turbulence using the Adelaide VHF radar /." Title page, abstract and contents only, 1991. http://web4.library.adelaide.edu.au/theses/09SM/09smm941.pdf.

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Baudino, Jean-Loup. "Analyse des données photométriques et spectroscopiques infrarouges d'exoplanètes obtenues avec l'instrument SPHERE au VLT." Observatoire de Paris, 2015. https://hal.science/tel-02095304.

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Depuis 2003 l’imagerie directe d’exoplanètes a permis d’obtenir des informations spectroscopiques et photométriques pour caractériser l’atmosphère de ces planètes géantes. Notre but a été tout d’abord de développer un outil simple pour interpréter les observations venant de SPHERE (Spectro-Polarimetric-High-contrast Exoplanet REsearch) au VLT et GPI (Gemini Planet Imager) au Gemini Sud pour déterminer les paramètres physiques des planètes. Nous avons développé un modèle d’exoplanètes géantes jeunes (nommés Exo-REM pour Exoplanet Radiative-convective Equilibriul Model). Les paramètres d’entrée du modèle sont la gravité de surface g, la température effective (Teff) et la composition élémentaire. Les sources d’opacité comprennent l’absorption par le continuum induit par collisions H2 –He et les raies atomiques et moléculaires de 8 corps différents (incluant la liste de raies du méthane d’Exomol). Les absorptions par des nuages de fer et de silicates sont aussi prises en compte sans diffusion. J’ai utilisé Exo-REM avec des observations photométriques et spectroscopiques des planètes naines et brunes HD 95086 b, beta Pictoris b, kappa Andromedae B, HR 8799 b, c, d, e, GJ 758 B. J’ai enfin étudié avec quelle précision pouvait-on dériver les paramètres physiques des planètes à partir de différents jeux d’observations, photométriques et spectroscopiques dans le cadre de SPHERE
Since 2003 direct imaging of exoplanets allows us to obtain spectroscopic and photometric data to characterize their atmospheres. First, our goal was to develop a simple tool to interpret data from SPHERE and GPI to derive planetary physical parameters. We developed a model of young giant exoplanet (called Exo-REM for Exoplanet Radiative-convective Equilibrium Model). Input parameters are surface gravity g, effective temperature (Teff) and an elemental composition. Opacity sources include the H2 –He collision-induced absorption and atomic and molecular lines from eight compounds (including CH4 updated with the Exomol linelist). We consider clouds of iron and silicates without scattering. I have used Exo-REM to analyse photometric and spectral observations of HD 95086 b, beta Pictoris b, kappa Andromedae B, HR 8799 b, c, d, e, GJ 758 B. I finally investigated the presicion to which the above parameters can be constrained from SPHERE measurement
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Mauriet, Sylvain. "Simulation d'un écoulement de jet de rive par une méthode VOF." Phd thesis, Université de Pau et des Pays de l'Adour, 2009. http://tel.archives-ouvertes.fr/tel-00463578.

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Les processus dynamiques présents en zone de swash ont un impact significatif sur l'évolution des zones côtières. Une part importante du transport sédimentaire cross-shore se produit dans cette zone, plus particulièrement dans cette zone où se produisent le run-up et le run-down. La zone située au-delà de la ligne de rivage au repos est le plus souvent décrite par des modèles intégrés sur la verticale. La décroissance des vagues est bien reproduite, cependant l'étude du transport sédimentaire impose une paramétrisation du frottement sur le fond. Nous présentons les résultats de simulations RANS de la propagation d'un mascaret (obtenu par un "lâcher de barrage") sur une plage en pente et le run-up et le run-down ainsi générés. Les résultats numériques sont comparés aux résultats expérimentaux de Yeh et al. (1989). Les simulations ont été réalisées avec le code Navier-Stokes diphasique AQUILON. Deux méthodes de suivi d'interface VOF (VOF TVD ET VOF PLIC) sont implémentées. La viscosité turbulente est calculée par un modèle V2-F (Durbin, 1991). Une estimation des grandeurs turbulentes k et epsilon basée sur la théorie des ondes longues pour la propagation d'un ressaut hydraulique est présentée. Une modélisation VOF-PLIC & V2-F est appliquée pour reproduire les caractéristiques macroscopiques du lâcher de barrage, qui comme on pouvait s'y attendre dépendent peu de la turbulence. Nous étudions aussi l'impact des conditions initiales sur k et epsilon sur l'établissement de l'écoulement turbulent. Après ces validations vis-à-vis de la turbulence, des simulations du cas décrit par Yeh et al. (1989) sont menées pour optimiser le choix des paramètres de calcul. La théorie de Whitham (1958), prédit un effondrement du mascaret au niveau de la ligne de rivage au repos. La théorie de Shen and Meyer (1963) est toujours à l'heure actuelle le modèle de référence. Les résultats expérimentaux de Yeh et al. (1989) montrent clairement un phénomène différent. L'utilisation conjointe de la technique VOF-TVD et du modèle de turbulence V2-F semble apporter les meilleurs résultats par rapport aux expériences de Yeh et al. (1989). Une étude de la transition mascaret/lame de swash est proposée. Nos résultats montrent que la théorie de Whitham décrit de façon assez précise le mécanisme de d'effondrement du mascaret. Les résultats de nos simulations sont utilisés pour décrire la transition entre l'effondrement du mascaret et l'écoulement du run-up. L'analyse des processus de frottement dans le jet de rive met en évidence une forte dissymétrie entre le run-up et le run-down avec cisaillement plus faible lors du run-down
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Lee, Christopher Francis. "Use of wind profilers to quantify atmospheric turbulence." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/use-of-wind-profilers-to-quantify-atmospheric-turbulence(d6a12ed2-533a-4dae-9f0d-747bc0b4c725).html.

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Doppler radar wind profilers are already widely used to measure atmospheric winds throughout the free troposphere and stratosphere. Several methods have been developed to quantify atmospheric turbulence with such radars, but to date they have remained largely un-tested; this thesis presents the first comprehensive validation of one such method. Conventional in-situ measurements of turbulence have been concentrated in the surface layer, with some aircraft and balloon platforms measuring at higher altitudes on a case study basis. Radars offer the opportunity to measure turbulence near continuously, and at a range of altitudes, to provide the first long term observations of atmospheric turbulence above the surface layer. Two radars were used in this study, a Mesosphere-Stratosphere-Troposphere (MST) radar, at Capel Dewi, West Wales, and the Facility for Ground Based Atmospheric Measurements (FGAM) mobile boundary layer profiler. In-situ measurements were made using aircraft and tethered-balloon borne turbulence probes. The spectral width method was chosen for detailed testing, which uses the width of a radar's Doppler spectrum as a measure of atmospheric velocity variance. Broader Doppler spectra indicate stronger turbulence. To obtain Gaussian Doppler spectra (a requirement of the spectral width method), combination of between five and seven consecutive spectra was required. Individual MST spectra were particularly non-Gaussian, because of the sparse nature of turbulence at its observation altitudes. The width of Gaussian fits to the Doppler spectrum were compared to those from the `raw' spectrum, to ensure that non-atmospheric signals were not measured. Corrections for non-turbulent broadening, such as beam broadening, and signal processing, were investigated. Shear broadening was found to be small, and the errors in its calculation large, so no corrections for wind shear were applied. Beam broadening was found to be the dominant broadening contribution, and also contributed the largest uncertainty to spectral widths. Corrected spectral widths were found to correlate with aircraft measurements for both radars. Observing spectral widths over time periods of 40 and 60 minutes for the boundary layer profiler and MST radar respectively, gave the best measure of turbulence intensity and variability. Median spectral widths gave the best average over that period, with two-sigma limits (where sigma is the standard deviation of spectral widths) giving the best representation of the variability in turbulence. Turbulent kinetic energies were derived from spectral widths; typical boundary layer values were 0.13 m 2.s (-2) with a two-sigma range of 0.04-0.25 m 2.s (-2), and peaked at 0.21 m 2.s (-2) with a two-sigma range of 0.08-0.61 m 2.s (-2). Turbulent kinetic energy dissipation rates were also calculated from spectral widths, requiring radiosonde measurements of atmospheric stability. Dissipation rates compared well width aircraft measurements, reaching peaks of 1x10 (-3) m 2.s (-3) within 200 m of the ground, and decreasing to 1-2x10 (-5) m 2.s (-3) near the boundary layer capping inversion. Typical boundary layer values were between 1-3x10 (-4) m 2.s (-3). Those values are in close agreement with dissipation rates from previous studies.
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Drevard, Déborah. "Etude expérimentale et numérique de la propagation d'ondes de gravité en zone de déferlement." Phd thesis, Université du Sud Toulon Var, 2006. http://tel.archives-ouvertes.fr/tel-00141744.

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En zone littorale, la houle subit de fortes transformations par effets bathymétriques. Une meilleure compréhension de ses modifications et des transferts d'énergie associés permet de mieux appréhender les problèmes de dimensionnement de structures côtières et d'aménagement du littoral (protection du littoral, influence des ouvrages sur la côte).
L'objectif de ce travail est d'étudier expérimentalement et numériquement la propagation et le déferlement
d'ondes de gravité.
La première partie, expérimentale, propose des méthodes de calcul, basées sur les houles de Stokes, pour la mesure d'ondes partiellement stationnaires à partir d'instruments de type électromagnétique (S4) ou
acoustique (ADV) donnant des mesures synchrones de vitesses et/ou de pression. Les influences du courant,
de la direction de propagation, de la profondeur d'immersion des appareils ainsi que des effets non
linéaires sont alors étudiés à partir de données en bassin et in situ.
La deuxième partie, numérique, consiste en la validation d'une méthode de suivi de surface libre de type
SL-VOF (Semi-Lagrangian Volume Of Fluid), insérée dans un code de calcul industriel (code EOLE de la
société Principia R&D). L'onde de gravité est modélisée par un soliton. L'étude de la propagation et du
déferlement du soliton est effectuée pour deux applications : sur une marche (discontinuité du fond) puis sur un fond de pente constante 1/15. L'évolution de la surface libre, son élévation et le champ de vitesses
sont alors comparés aux résultats expérimentaux.
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Books on the topic "VLF atmosphere"

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Gubbay, J. S. Scientific investigations of the Space Research Group. Salisbury: DSTO, 1988.

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W, Thomson Dennis, and United States. National Aeronautics and Space Administration., eds. Final technical report for NASA grant no. NAG8-050 entitled Combined VHF doppler radar and airborne (CV-990) measurements of atmospheric winds on the mesoscale. University Park, PA: Pennsylvania State University, 1989.

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Book chapters on the topic "VLF atmosphere"

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Windsteig, W., E. A. Dorfi, S. Höfner, J. Hron, and F. Kerschbaum. "Synthetic Images from Dynamic Model Atmospheres of C-Rich Long-Period Variables." In Science with the VLT Interferometer, 401–2. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-540-69398-7_66.

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Röttger, J., and M. F. Larsen. "UHF/VHF Radar Techniques for Atmospheric Research and Wind Profiler Applications." In Radar in Meteorology, 235–81. Boston, MA: American Meteorological Society, 1990. http://dx.doi.org/10.1007/978-1-935704-15-7_23.

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Das, Tanmay, Debyendu Jana, Arpan Mitra, P. Nandakumar, Sudipto Datta, Jawad Y. Siddiqui, Ashik Paul, Gopal Singh, Arnam Ghosh, and Souvik Majumder. "Lower Atmospheric Wind Profile Studies and Validation of VHF Doppler Radar of University of Calcutta." In Computers and Devices for Communication, 183–89. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-8366-7_25.

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Maurya, Ajeet Kumar, Gaurish Tripathi, S. B. Singh, Rajesh Singh, and A. K. Singh. "Low-latitude upper atmosphere remote sensing using very low frequency (VLF) waves." In Atmospheric Remote Sensing, 283–306. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-323-99262-6.00002-x.

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Wakabayashi, Ryoji. "Fundamentals of Meteor Burst Communication." In Advances in Environmental Engineering and Green Technologies, 202–12. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-2381-0.ch011.

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When space dust rushes into the atmosphere, oxygen and nitrogen are ionized by frictional heat. Along the dust flight path, a very long cylindrical plasma tube, 10 meters in diameter and several kilometers long is formed. The long plasma tube is called “meteor burst” and is a good reflector for radio waves in the VHF band. Non-line-of-sight communication performed using this reflector is called “meteor burst communication”. In this chapter, the basics of meteor burst communication and its applications are outlined.
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Conference papers on the topic "VLF atmosphere"

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Jang, Bo, Dong Wen, Tao Xu, and Cuihai Liu. "Linear prediction model based suppression technology for VLF atmosphere noise signals." In 2012 11th International Conference on Signal Processing (ICSP 2012). IEEE, 2012. http://dx.doi.org/10.1109/icosp.2012.6491828.

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Nico, G., A. Nina, P. Biagi, R. Colella, and A. Ermini. "Studying the temporal variations of atmosphere physical properties at different spatial and temporal scales by VLF radio signals and space geodesy techniques." In 2020 XXXIIIrd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS). IEEE, 2020. http://dx.doi.org/10.23919/ursigass49373.2020.9232381.

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Lyakhov, A. N., A. A. Egoshin, J. I. Zetzer, and K. N. Yakimenko. "Numerical simulation of the impact of the middle atmosphere parameters on the lower ionosphere and VLF/LF radiowaves propagation using MLS EOS AURA data." In 2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM). IEEE, 2013. http://dx.doi.org/10.1109/usnc-ursi-nrsm.2013.6525134.

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Bashkuev, Yuri, Ludmila Angarkhaeva, Darima Buyanova, and Viktor Melchinov. "Surface impedance of the structure: thick ice-sea in VLF-VHF range of radio waves." In 26th International Symposium on Atmospheric and Ocean Optics, Atmospheric Physics, edited by Gennadii G. Matvienko and Oleg A. Romanovskii. SPIE, 2020. http://dx.doi.org/10.1117/12.2575050.

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Bashkuev, Yuri B., Ludmila K. Angarkhaeva, and Darima G. Buyanova. "Surface impedance of the layered medium "dry sand - watered sea sand" in the VLF-VHF range." In 27th International Symposium on Atmospheric and Ocean Optics, Atmospheric Physics, edited by Oleg A. Romanovskii and Gennadii G. Matvienko. SPIE, 2021. http://dx.doi.org/10.1117/12.2603255.

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Cherneva, Nina V., and Gennadii I. Druzhin. "Diurnal periods of VLF radiation." In XXIII International Symposium, Atmospheric and Ocean Optics, Atmospheric Physics, edited by Oleg A. Romanovskii. SPIE, 2017. http://dx.doi.org/10.1117/12.2286243.

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Jenn-Shyong Chen, Shih-Chiao Tsai, Yen-Hsyang Chu, and Ching-Lun Su. "Multifrequency range imaging of atmospheric structures using VHF-band atmosphere radars." In 2016 Progress in Electromagnetic Research Symposium (PIERS). IEEE, 2016. http://dx.doi.org/10.1109/piers.2016.7735368.

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Buyanova, D. G., D. B. Auyrov, and Y. B. Bashkuev. "Variations of parameters ELF-VLF noise and VLF signals on the Demeter satellite over the seismic activity region." In 20th International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics, edited by Oleg A. Romanovskii. SPIE, 2014. http://dx.doi.org/10.1117/12.2073467.

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Vodinchar, G. M., E. A. Malysh, and N. V. Cherneva. "Recognition of whistler patterns in vlf signal spectrograms." In XXII International Symposium Atmospheric and Ocean Optics. Atmospheric Physics, edited by Gennadii G. Matvienko and Oleg A. Romanovskii. SPIE, 2016. http://dx.doi.org/10.1117/12.2247928.

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Bashkuev, Yuri B., Valery B. Khaptanov, and Darima G. Buyanova. "ELF-VLF radio wave diagnostics of the granitoid massif." In XXV International Symposium, Atmospheric and Ocean Optics, Atmospheric Physics, edited by Gennadii G. Matvienko and Oleg A. Romanovskii. SPIE, 2019. http://dx.doi.org/10.1117/12.2540893.

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Reports on the topic "VLF atmosphere"

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Wilson, D., Daniel Breton, Lauren Waldrop, Danney Glaser, Ross Alter, Carl Hart, Wesley Barnes, et al. Signal propagation modeling in complex, three-dimensional environments. Engineer Research and Development Center (U.S.), April 2021. http://dx.doi.org/10.21079/11681/40321.

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The Signal Physics Representation in Uncertain and Complex Environments (SPRUCE) work unit, part of the U.S. Army Engineer Research and Development Center (ERDC) Army Terrestrial-Environmental Modeling and Intelligence System (ARTEMIS) work package, focused on the creation of a suite of three-dimensional (3D) signal and sensor performance modeling capabilities that realistically capture propagation physics in urban, mountainous, forested, and other complex terrain environments. This report describes many of the developed technical capabilities. Particular highlights are (1) creation of a Java environmental data abstraction layer for 3D representation of the atmosphere and inhomogeneous terrain that ingests data from many common weather forecast models and terrain data formats, (2) extensions to the Environmental Awareness for Sensor and Emitter Employment (EASEE) software to enable 3D signal propagation modeling, (3) modeling of transmitter and receiver directivity functions in 3D including rotations of the transmitter and receiver platforms, (4) an Extensible Markup Language/JavaScript Object Notation (XML/JSON) interface to facilitate deployment of web services, (5) signal feature definitions and other support for infrasound modeling and for radio-frequency (RF) modeling in the very high frequency (VHF), ultra-high frequency (UHF), and super-high frequency (SHF) frequency ranges, and (6) probabilistic calculations for line-of-sight in complex terrain and vegetation.
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