A5041679533- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Geomagnetism and Paleomagnetism Studies
- Astronomy and Astrophysical Research
- Calibration and Measurement Techniques
- Atmospheric Ozone and Climate
- Ionosphere and magnetosphere dynamics
- Astronomical Observations and Instrumentation
- solar cell performance optimization
- Distributed and Parallel Computing Systems
- Spacecraft Dynamics and Control
- Methane Hydrates and Related Phenomena
- Optical Wireless Communication Technologies
- Nuclear Physics and Applications
- Geological and Geophysical Studies
- Cancer Treatment and Pharmacology
- Various Chemistry Research Topics
- Analytical Chemistry and Sensors
- Mathematics, Computing, and Information Processing
- Scientific Research and Discoveries
- History and Developments in Astronomy
Lagrange Laboratory
2012-2025
Observatoire de la Côte d’Azur
2012-2025
Université Côte d'Azur
2010-2025
Institut de Biologie Valrose
2025
Centre National de la Recherche Scientifique
2010-2021
National Solar Observatory
2002-2003
Imperial College London
2002
High Altitude Observatory
2000-2002
Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within solar interior. The nearly uninterrupted observations Global Oscillation Network Group (GONG) yield power spectra high duty cycles signal-to-noise ratios. Frequency splittings derived from GONG confirm that variation rate seen at surface carries through much convection zone, base which is an adjustment layer leading latitudinally...
We present the identification of very low frequency g modes in asymptotic regime and two important parameters that have long been waited for: core rotation rate, equidistant period spacing these modes. The GOLF instrument on board SOHO space observatory has provided decades full-disk helioseismic data. In study, we search for possible collective modulations are produced by periodic changes deep solar structure. Such provide access to only modes, thus allowing statistical methods take...
Using contemporaneous helioseismic data from the Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI) onboard SOHO, we compare frequency-splitting resulting inversions about Sun's internal rotation. Helioseismology has been very successful in making detailed subtle inferences solar interior. But there are some significant differences between inversion results obtained MDI GONG projects. It is important for robust interior that these located their causes eliminated. By...
From the analysis of low-order GOLF+MDI sectoral modes (ℓ ≤ 3, 6 n 15, |m| = ℓ) and LOWL data > 3), we derive radial rotation profile by assuming no latitudinal dependence in solar core. These acoustic contain most statistically significant information about deepest layers should be least influenced internal variability associated with dynamo. After correction splittings for their contamination higher latitudes, obtain a flat down to 0.2 R☉.
Ring-diagram analysis, a local helioseismology technique, has proven to be very useful for studying solar subsurface velocity flows down depth of about 0.97 R☉. The range is determined by the modes used in this type and thus depends on size area analyzed. Extending allows us detect lower spherical harmonic degree (l) which, at constant frequency, penetrate deeper Sun. However, there compromise between validity plane-wave approximation technique. We present results applying ring diagrams 30°...
We analyze Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI) observations obtained during Carrington rotation 1988 (2002 March 30-April 26) with a ring-diagram technique in order to measure the zonal meridional flow components upper solar convection zone. derive daily maps over range of depths up 16 Mm on spatial grid 75 latitude longitude covering ±60° central meridian distance combine them make synoptic maps. begin exploring dynamics near-surface layers interaction...
The Sun is the most studied of all stars, and thus constitutes a benchmark for stellar models. However, our vision still incomplete, as illustrated by current debate on its chemical composition. problem reaches far beyond abundances intimately linked to microscopic macroscopic physical ingredients solar models such radiative opacity, which experimental results have been recently measured that await theoretical explanations. We present opacity profiles derived from helioseismic inferences...
Corbard & Thompson analyzed quantitatively the strong radial differential rotation that exists in a thin layer near solar surface. We investigate role of this shear driving flux transport dynamo operating with such profile. show despite being strong, near-surface effectively contributes only ~1 kG (~30% total) to toroidal fields produced there unless an abnormally high, surface α-effect is included. While 3 spot formation from ~1-2 by convective collapse cannot be ruled out, evolutionary...
We measure the horizontal flows in outer 2% of Sun by analyzing 14 consecutive Carrington rotations Global Oscillation Network Group (GONG) Doppler images and two Michelson Imager (MDI) Dynamics Program data with ring-diagram technique. The zonal meridional show no variation activity at low to medium levels (below 71 G). At active region locations, flow increases increasing activity; regions rotate faster than their quieter surroundings. locations is more equatorward on average depths less...
The potential relationship between solar activity and changes in diameter remains the subject of debate requires both models measurements with sufficient precision over long periods time. Using PICARD instruments, we carried out precise variations during rising phase cycle 24. From new correction methods found space telescope radius amplitudes that were less than ±20 mas (i.e. ±14.5 km) for years 2010–2011. Moreover, ground-based are smaller ±50 from 2011 to 2014. Our observations could not...
Context.The most recent determination of the solar chemical composition, using a time-dependent, 3D hydrodynamical model atmosphere, exhibits significant decrease C, N, O abundances compared to their previous values. Solar models that use these new are not consistent with helioseismological determinations sound speed profile, surface helium abundance and convection zone depth.
The POLAR Investigation of the Sun (POLARIS) mission uses a combination gravity assist and solar sail propulsion to place spacecraft in 0.48 AU circular orbit around with an inclination 75 degrees respect equator. This challenging is made possible by development propulsion. first extended view high-latitude regions will enable crucial observations not from ecliptic viewpoint or Solar Orbiter. While Orbiter would give glimpse high latitude magnetic field flows probe dynamo, it does have...
High quality observations of the low-degree acoustic modes (p-modes) exist for almost two complete solar cycles using spectrophotometer Mark-I, located at Observatorio del Teide (Tenerife, Spain) and operating now as part Birmingham Solar Oscillations Network (BiSON). We have performed a Fourier analysis 30 calibrated time-series one year duration covering total period 15 years between 1984 1999. Applying different techniques to resulting power spectra, we study signature activity changes on...
Context. We compare solar differential rotation of subphotospheric layers derived from local helioseismology analysis GONG++ dopplergrams and the one tracing small bright coronal structures (SBCS) using EIT/SOHO images for period August 2001 - December 2006, which correspond to declining phase cycle 23. Aims. The study aims find a relationship between SBCS angular velocity. northsouth asymmetries both velocity measurements are also investigated. Methods. Subphotospheric was ring-diagram...
The recent claims of g-mode detection have restarted the search for these potentially extremely important modes. These can be reassessed in view different data sets available from SoHO instruments and ground-based instruments. We produce a new calibration GOLF with more consistent p-mode amplitude time shift correction compared to series used past. 22 years is done simpler approach that uses only predictive radial velocity spacecraft as reference. Using p modes, we measure correct between...
Recent studies have established that peaks in solar oscillation power spectra are not Lorentzian shape but a distinct asymmetry. Fitting symmetric profile to the peaks, therefore, produces shift frequency of modes. Accurate determination low-frequency modes is essential infer structure core by inversion mode frequencies. In this paper we investigate how changes frequencies low-degree obtained fitting and asymmetric peak profiles change inferred properties core. We use data Global...
Context . In 2015, the International Astronomical Union (IAU) passed Resolution B3, which defined a set of nominal conversion constants for stellar and planetary astronomy. B3 new value solar radius ( R ⊙ N = 695 700 km km) that is different from canonical used until now (695 990 km). The consistent with helioseismic estimates. Recent results obtained ground-based instruments, balloon flights, or space-based instruments highlight values are significantly different. These related to direct...
The equator-to-pole radius difference (Δr=R eq−R pol) is a fundamental property of our star, and understanding it will enrich future solar stellar dynamical models. oblateness (Δ⊙) corresponds to the excess ratio equatorial (R eq) polar pol), which great interest for those working in relativity different areas physics. Δr known be rather small quantity, where positive value about 8 milli-arcseconds (mas) suggested by previous measurements predictions. Picard space mission aimed measure with...
The recent claimed detection of g modes was obtained from the analysis power spectrum time series round-trip travel p modes. goal this paper is to reproduce these results on which claims are based for confirming or invalidating with method used make claims. We computed using procedure given in Fossat et al. (2017), and different variations times comparison. recently calibrated GOLF data (published Paper I) sampling, photomultipliers, length reproducing analysis. also correlated an asymptotic...