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Search Results: 1 - 10 of 219590 matches for " C. Bizouard "
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Hydrological Excitation of Polar Motion Derived from GRACE Gravity Field Solutions
L. Seoane,J. Nastula,C. Bizouard,D. Gambis
International Journal of Geophysics , 2011, DOI: 10.1155/2011/174396
Abstract: The influence of the continental water storage on the polar motion is not well known. Different models have been developed to evaluate these effects and compared to geodetic observations. However, previous studies have shown large discrepancies mainly attributed to the lack of global measurements of related hydrological parameters. Now, from the observations of the GRACE mission, we can estimate the polar motion excitation due to the global hydrology. Data processing of GRACE data is carried out by several centers of analysis, we focus on the new solution computed by the Groupe de Recherche de Géodésie Spatiale. At annual scales, excitations derived from GRACE data are in better agreement with geodetic observations than models estimates. The main contribution to the hydrological excitation comes from the monsoon climates regions where GRACE and models estimates are in a very good agreement. Still, the effect of the north high latitudes regions, where the principal areas of snow cover are found, cannot be neglected. At these regions, GRACE and models estimated contributions to polar motion excitations show significant discrepancies. Finally, GRACE-based excitations reveal the possible influence of water storage variations in exciting polar motion around the frequency of 3 cycles per year.
Hydrological Excitation of Polar Motion Derived from GRACE Gravity Field Solutions
L. Seoane,J. Nastula,C. Bizouard,D. Gambis
International Journal of Geophysics , 2011, DOI: 10.1155/2011/174396
Abstract: The influence of the continental water storage on the polar motion is not well known. Different models have been developed to evaluate these effects and compared to geodetic observations. However, previous studies have shown large discrepancies mainly attributed to the lack of global measurements of related hydrological parameters. Now, from the observations of the GRACE mission, we can estimate the polar motion excitation due to the global hydrology. Data processing of GRACE data is carried out by several centers of analysis, we focus on the new solution computed by the Groupe de Recherche de Géodésie Spatiale. At annual scales, excitations derived from GRACE data are in better agreement with geodetic observations than models estimates. The main contribution to the hydrological excitation comes from the monsoon climates regions where GRACE and models estimates are in a very good agreement. Still, the effect of the north high latitudes regions, where the principal areas of snow cover are found, cannot be neglected. At these regions, GRACE and models estimated contributions to polar motion excitations show significant discrepancies. Finally, GRACE-based excitations reveal the possible influence of water storage variations in exciting polar motion around the frequency of 3 cycles per year. 1. Introduction The excitation of polar motion is, to a large extent, related to the mass redistribution of geophysical fluids. The importance of atmospheric and oceanic angular momentum signals at monthly and seasonal periods is well known. The contribution of the continental hydrological signals, originating from land water, snow, and ice, is, however, less known. A number of previous studies have estimated hydrological excitation from climatological measurements, numerical climate models, and global hydrology models based upon the observed distribution of surface water, snow, ice, and soil moisture [1–5]. The hydrological part of polar motion excitation can also be obtained, as a residual series, by removing atmospheric and oceanic signals from the geodetic excitation of polar motion. The general conclusion of these studies is that the change in continental water storage plays a major role in the seasonal polar motion although the results of the hydrological models do not agree with each other and with observed polar motion [6, 7]. This is mainly due to the lack of global measurements of related hydrological parameters which are difficult to predict (like evaporation, run-off, groundwater, and snow/ice mass change). Other analyses show that hydrological signals seem
Reconstruction of source location in a network of gravitational wave interferometric detectors
F. Cavalier,M. Barsuglia,M. -A. Bizouard,V. Brisson,A. -C. Clapson,M. Davier,P. Hello,S. Kreckelbergh,N. Leroy,M. Varvella
Physics , 2006, DOI: 10.1103/PhysRevD.74.082004
Abstract: This paper deals with the reconstruction of the direction of a gravitational wave source using the detection made by a network of interferometric detectors, mainly the LIGO and Virgo detectors. We suppose that an event has been seen in coincidence using a filter applied on the three detector data streams. Using the arrival time (and its associated error) of the gravitational signal in each detector, the direction of the source in the sky is computed using a chi^2 minimization technique. For reasonably large signals (SNR>4.5 in all detectors), the mean angular error between the real location and the reconstructed one is about 1 degree. We also investigate the effect of the network geometry assuming the same angular response for all interferometric detectors. It appears that the reconstruction quality is not uniform over the sky and is degraded when the source approaches the plane defined by the three detectors. Adding at least one other detector to the LIGO-Virgo network reduces the blind regions and in the case of 6 detectors, a precision less than 1 degree on the source direction can be reached for 99% of the sky.
Searching for gravitational waves with the LIGO and Virgo interferometers
Marie Anne Bizouard,Maria Alessandra Papa
Physics , 2013, DOI: 10.1016/j.crhy.2013.03.001
Abstract: The first generation of ground-based interferometric gravitational wave detectors, LIGO, GEO and Virgo, have operated and taken data at their design sensitivities over the last few years. The data has been examined for the presence of gravitational wave signals. Presented here is a comprehensive review of the most significant results. The network of detectors is currently being upgraded and extended, providing a large likelihood for observations. These future prospects will also be discussed.
A comparison of methods for gravitational wave burst searches from LIGO and Virgo
F. Beauville,M. -A. Bizouard,L. Blackburn,L. Bosi,L. Brocco,D. Brown,D. Buskulic,F. Cavalier,S. Chatterji,N. Christensen,A. -C. Clapson,S. Fairhurst,D. Grosjean,G. Guidi,P. Hello,S. Heng,M. Hewitson,E. Katsavounidis,S. Klimenko,M. Knight,A. Lazzarini,N. Leroy,F. Marion,J. Markowitz,C. Melachrinos,B. Mours,F. Ricci,A. Viceré,I. Yakushin,M. Zanolin
Physics , 2007, DOI: 10.1088/0264-9381/25/4/045002
Abstract: The search procedure for burst gravitational waves has been studied using 24 hours of simulated data in a network of three interferometers (Hanford 4-km, Livingston 4-km and Virgo 3-km are the example interferometers). Several methods to detect burst events developed in the LIGO Scientific Collaboration (LSC) and Virgo collaboration have been studied and compared. We have performed coincidence analysis of the triggers obtained in the different interferometers with and without simulated signals added to the data. The benefits of having multiple interferometers of similar sensitivity are demonstrated by comparing the detection performance of the joint coincidence analysis with LSC and Virgo only burst searches. Adding Virgo to the LIGO detector network can increase by 50% the detection efficiency for this search. Another advantage of a joint LIGO-Virgo network is the ability to reconstruct the source sky position. The reconstruction accuracy depends on the timing measurement accuracy of the events in each interferometer, and is displayed in this paper with a fixed source position example.
Detailed comparison of LIGO and Virgo Inspiral Pipelines in Preparation for a Joint Search
F. Beauville,M. -A. Bizouard,L. Blackburn,L. Bosi,L. Brocco,D. Brown,D. Buskulic,F. Cavalier,S. Chatterji,N. Christensen,A. -C. Clapson,S. Fairhurst,D. Grosjean,G. Guidi,P. Hello,S. Heng,M. Hewitson,E. Katsavounidis,S. Klimenko,M. Knight,A. Lazzarini,N. Leroy,F. Marion,J. Markowitz,C. Melachrinos,B. Mours,F. Ricci,A. Viceré,I. Yakushin,M. Zanolin
Physics , 2007, DOI: 10.1088/0264-9381/25/4/045001
Abstract: Presented in this paper is a detailed and direct comparison of the LIGO and Virgo binary neutron star detection pipelines. In order to test the search programs, numerous inspiral signals were added to 24 hours of simulated detector data. The efficiencies of the different pipelines were tested, and found to be comparable. Parameter estimation routines were also tested. We demonstrate that there are definite benefits to be had if LIGO and Virgo conduct a joint coincident analysis; these advantages include increased detection efficiency and the providing of source sky location information.
A First Comparison Between LIGO and Virgo Inspiral Search Pipelines
L. Blackburn,F. Beauville,M. -A. Bizouard,L. Bosi,P. Brady,L. Brocco,D. Brown,D. Buskulic,S. Chatterji,N. Christensen,A. -C. Clapson,S. Fairhurst,D. Grosjean,G. Guidi,P. Hello,E. Katsavounidis,M. Knight,A. Lazzarini,F. Marion,B. Mours,F. Ricci,A. Vicere',M. Zanolin
Physics , 2005,
Abstract: This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed.
A first comparison of search methods for gravitational wave bursts using LIGO and Virgo simulated data
L. Blackburn,F. Beauville,M. -A. Bizouard,L. Bosi,P. Brady,L. Brocco,D. Brown,D. Buskulic,S. Chatterji,N. Christensen,A. -C. Clapson,S. Fairhurst,D. Grosjean,G. Guidi,P. Hello,E. Katsavounidis,M. Knight,A. Lazzarini,F. Marion,B. Mours,F. Ricci,A. Vicere,M. Zanolin
Physics , 2005,
Abstract: We present a comparative study of 6 search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The data's spectra were chosen to follow the design sensitivity of the two 4km LIGO interferometers and the 3km Virgo interferometer. The searches were applied on replicas of the data sets to which 8 different signals were injected. Three figures of merit were employed in this analysis: (a) Receiver Operator Characteristic curves, (b) necessary signal to noise ratios for the searches to achieve 50 percent and 90 percent efficiencies, and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.
Benefits of joint LIGO -- Virgo coincidence searches for burst and inspiral signals
F. Beauville,M. -A. Bizouard,L. Blackburn,L. Bosi,P. Brady,L. Brocco,D. Brown,D. Buskulic,F. Cavalier,S. Chatterji,N. Christensen,A. -C. Clapson,S. Fairhurst,D. Grosjean,G. Guidi,P. Hello,E. Katsavounidis,M. Knight,A. Lazzarini,N. Leroy,F. Marion,B. Mours,F. Ricci,A. Vicere,M. Zanolin
Physics , 2005, DOI: 10.1088/1742-6596/32/1/032
Abstract: We examine the benefits of performing a joint LIGO--Virgo search for transient signals. We do this by adding burst and inspiral signals to 24 hours of simulated detector data. We find significant advantages to performing a joint coincidence analysis, above either a LIGO only or Virgo only search. These include an increased detection efficiency, at a fixed false alarm rate, to both burst and inspiral events and an ability to reconstruct the sky location of a signal.
About the detection of gravitational wave bursts
T. Pradier,N. Arnaud,M. -A. Bizouard,F. Cavalier,M. Davier,P. Hello
Physics , 2000, DOI: 10.1142/S0218271800000335
Abstract: Several filtering methods for the detection of gravitational wave bursts in interferometric detectors are presented. These are simple and fast methods which can act as online triggers. All methods are compared to matched filtering with the help of a figure of merit based on the detection of supernovae signals simulated by Zwerger and Muller.
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