Directrice de recherche, CNRS
Summary
CNRS researcher
ORCID: 0000-0003-4606-2170
Research ID: P-3438-2014
Keywords of research activity: Time-varying Gravimetry, Superconducting Gravimetry, Earth's normal modes, Gravito-elasticity of the Earth, Geodesy
Qu'est-ce que la gravité ?
Newton, Lettre III (25 février 1692-1693), ibid., p. 211, extrait d'une lettre au révérend Dr Bentley :
"Il est inconcevable que la matière brute inanimée, sans la médiation de quelque chose d'autre qui n'est pas matériel, puisse agir sur une autre matière et l'affecter sans contact mutuel, comme cela devrait être si la gravitation, dans le sens d'Epicure, lui était essentielle et inhérente."
Gravité quantique :
Le graviton est le médiateur des ondes gravitationnelles, comme le photon pour les ondes électromagnétiques.
Relativité générale (Einstein, 1915) :
La gravité est la manifestation de la courbure de l'espace-temps.
Some current and past projects Geodesy and geophysics
- Characterization of gravitational disturbances at various time and space scales (analysis of geodetic records: gravimeter, tiltmeter, GNSS, SLR...): noise levels, accuracy, stability
- Consistency of space and ground geodetic (gravimetric, surface deformation) observables
- Intercomparison of gravity (Superconducting Gravimeters) and vertical height changes (GNSS) at seasonal periods
- Comparison of degree-2 space gravity (Satellite Laser Ranging) and surface deformation (GNSS) at interannual periods
- Inversion of geocenter motion
Geocenter motion = motion of center of mass of the entire Earth (solid Earth and surficial layers) with respect to the center of the terrestrial reference frame
- Characterization of fluid core and inner core dynamical processes from ground and space observations, theoretical modeling
- Free Core Nutation (retrograde 430-day nutation in space, quasi-diurnal wobble on Earth)
- Free Inner Core Nutation (prograde nutation in space, nearly-diurnal wobble on Earth)
- Translational oscillation of the inner core at a 5-hour period ("Slichter" modes)
- Interannual & decadal fluctuations from space gravimetry (Hugo Lecomte's PhD thesis 2020-2023)
Free Core Nutation (FCN) = rotational normal mode of the Earth that exists because of the presence of the elliptical fluid core. The axis of rotation of the flattened fluid core is misaligned with the rotation axis of the Earth's mantle. Displaced flows act as a restoring pressure torque on the fluid core. In a terrestrial reference frame, the FCN mode has a period close to one day, so it is also called "nearly-diurnal free wobble". In a celestial reference frame, its period is about -430 days with a retrograde motion (opposite to Earth's rotation). This mode can be observed by the resonance effect in diurnal tidal waves or in nutation observed by VLBI (Very Long Baseline Interferometry) technique.
Free Inner Core Nutation (FICN) = equivalent to the FCN but for the solid elliptical inner core. This rotational mode has never been directly observed. The theoretically predicted period is poorly constrained with values ranging from 200 to more than 1000 sidereal days. The IERS Conventions based on VLBI nutation propose a period between 930 and 1140 days.
--> Constraints on coupling mechanisms and some physical parameters at core boundaries
- Normal modes of the Earth (analysis, modeling):
- Seismic modes : Low-frequency seismic modes after the 2004 Mw9.2 Sumatra-Andaman, 2010 Mw8.8 Chile and 2011 Mw9 Tohoku earthquakes
- Rotational modes: Free Core Nutation, Free Inner Core Nutation, Chandler Wobble, Inner-Core Wobble
Interdisciplinarity Gravitational waves and geophysics
- Interactions of Gravitational Waves with the Earth
- Excitation of seismic modes (J. Majstorovic's PhD thesis 2016-2019)
- Perturbation of the Earth's rotation
- Newtonian noise on instruments
- Observed vs. instrumental noise levels of Superconducting Gravimeters
- Surficial layers (atmospheric, oceanic, hydrologic) Newtonian and loading deformation contributions on gravity field measurements
Partnership in French Projets Investissement d'Avenir
- MIGA : Antenne gravitationnelle basée sur l'interférométrie atomique
Collaboration in European projects
- ELGAR : the European Laboratory for Gravitational and Atom-interferometric Research
(Canuel et al. 2020. ELGAR -- a European Laboratory for Gravitation and Atom-interferometric Research, Classical and Quantum Gravity, https://doi.org/10.1088/1361-6382/aba80e) - GRACEFUL (GRavimetry, mAgnetism, rotation and CorE FLow): Synergy Grant from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme. P.I.: Véronique Dehant (Royal Observatory of Belgium, Bruxelles), Mioara Mandea (CNES), Anny Cazenave (CNES - MAGELLIUM, Toulouse)
- 2023 - 2027 : International Research Network, INP - CNRS, ELGAR European Laboratory for Gravitation and Atom-interferometric Research, member steering committee, leader WG2 (Strategies for Newtonian Noise (NN) reduction), PI : B. Canuel (LP2N, Bordeaux)