A5081906563- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Magnetic confinement fusion research
- Solar Radiation and Photovoltaics
- Historical and Architectural Studies
- Magnetic Field Sensors Techniques
- Atomic and Subatomic Physics Research
- Earthquake Detection and Analysis
- Planetary Science and Exploration
- Geophysical and Geoelectrical Methods
- Quantum, superfluid, helium dynamics
- Superconducting Materials and Applications
- Nuclear Physics and Applications
- Magnetic and Electromagnetic Effects
- Integrated Circuits and Semiconductor Failure Analysis
- Aerodynamics and Acoustics in Jet Flows
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Risk and Safety Analysis
- Reservoir Engineering and Simulation Methods
- Power Transformer Diagnostics and Insulation
Observatoire de Paris
2012-2024
Sorbonne Université
2015-2024
Centre National de la Recherche Scientifique
2015-2024
École Polytechnique
2021-2024
Laboratoire de Physique des Plasmas
2006-2024
University of Oslo
2021-2024
Université Paris Sciences et Lettres
2015-2022
Université Paris-Saclay
2021-2022
Laboratoire d’études spatiales et d’instrumentation en astrophysique
2012-2021
Délégation Paris 7
2011-2020
We analyze the physical mechanisms that form a three-dimensional coronal flux rope and later cause its eruption. This is achieved by zero-β magnetohydrodynamic (MHD) simulation of an initially potential, asymmetric bipolar field, which evolves means simultaneous slow magnetic field diffusion sub-Alfvénic, line-tied shearing motions in photosphere. As similar models, flux-cancellation-driven photospheric reconnection bald-patch (BP) separatrix transforms sheared arcades into slowly rising...
Flare ribbons are commonly attributed to the low-altitude impact, along footprints of separatrices or quasi-separatrix layers (QSLs), particle beams accelerated through magnetic reconnection. If reconnection occurs at a three-dimensional coronal null point, footprint dome-shaped fan surface would map closed circular ribbon. This paper addresses following issues: does entire ribbon brighten simultaneously, as expected because all field lines pass point? And since spine singular lines, do...
The coronal magnetic configuration of an active region typically evolves quietly during few days before becoming suddenly eruptive and launching a mass ejection (CME). precise origin the eruption is still debated. Among several mechanisms, it has been proposed that loss equilibrium, or ideal magneto-hydrodynamic (MHD) instability such as torus instability, could be responsible for sudden eruptivity. Distinct approaches have also formulated limit cases having circular translation symmetry. We...
Context. The standard CSHKP model for eruptive flares is two-dimensional. Yet observational interpretations of photospheric currents in pre-eruptive sigmoids, shear post-flare loops, and relative positioning shapes flare ribbons, all together require three-dimensional extensions to the model.
Solar flares and coronal mass ejections are associated with rapid changes in field connectivity powered by the partial dissipation of electrical currents solar atmosphere. A critical unanswered question is whether involved induced motion pre-existing atmospheric magnetic flux subject to surface plasma flows, or these emergence from within convective zone. We address this problem applying state-of-the-art nonlinear force-free (NLFFF) modeling highest resolution quality vector-magnetographic...
On 1998 July 14, a class M3 flare occurred at 12:55 UT in AR 8270 near disk center. Kitt Peak line-of-sight magnetograms show that the δ spot. Mees vector strong shear localized portion of closed neutral line around parasitic polarity Observations 171, 195, and 1600 Å have been obtained by TRACE, with ≃40 s temporal 05 spatial resolutions. They reveal small-scale preflare loops above sheared region expanded disappeared for more than 1 hr before maximum. During flare, bright anchored ribbons...
During its 2000 January flight, the Flare Genesis Experiment observed gradual emergence of a bipolar active region, by recording series high-resolution photospheric vector magnetograms and images in blue wing Hα line. Previous analyses these data revealed occurrence many small-scale, transient brightenings identified as Ellerman bombs (EBs). They occur during flux emergence, them are located near moving magnetic dipoles which field is nearly tangential to photosphere. A linear force-free...
In 3D magnetic field configurations, quasi-separatrix layers (QSLs) are defined as volumes in which lines locally display strong gradients of connectivity. Considering QSLs both the preferential locations for current sheet development and reconnection, general, a natural model solar flares coronal heating, particular, has been strongly debated issues over past decade. this paper, we perform zero-β resistive MHD simulations electric currents smooth configurations are, strictly speaking,...
An isolated active region (AR) was observed on the Sun during seven rotations, starting from its birth in July 1996 to full dispersion December 1996. We analyse long-term budget of AR relative magnetic helicity. Firstly, we calculate helicity injected by differential rotation at photospheric level using MDI/SoHO magnetograms. Secondly, compute coronal field and selecting model which best fits soft X-ray loops with SXT/Yohkoh. Finally, identify all mass ejections (CMEs) that originated...
Context. A standard model for eruptive flares aims at describing observational 3D features of the reconnecting coronal magnetic field. Extensions to 2D require physical understanding reconnection processes origin configuration evolution. However, properties without null point and separatrices still need be analyzed.
Solar flares strongly affect the Sun's atmosphere as well Earth's environment. Quantifying maximum possible energy of solar present-day Sun, if any, is thus a key question in heliophysics. The largest observed over past few decades have reached energies times 10^{32} ergs, possibly up to 10^{33} ergs. Flares active Sun-like stars reach about 10^{36} In absence direct observations within this range, complementary methods investigation are needed. Using historical reports for region, we scaled...
The 2011 February 15 X2.2 flare and associated Earth-directed halo coronal mass ejection were observed in unprecedented detail with high resolution spatial, temporal, thermal dimensions by the Atmospheric Imaging Assembly (AIA) on Solar Dynamics Observatory, as well instruments two STEREO spacecraft, then at near-quadrature relative to Sun–Earth line. These observations enable us see expanding loops from a flux-rope-like structure over shearing polarity-inversion line between central δ-spot...
We present for the first time evolution of photospheric electric currents during an eruptive X-class flare, accurately predicted by standard 3D flare model. analyze this February 15, 2011 using HMI/SDO magnetic observations and find that localized in \J-shaped ribbons increase to double their pre-flare intensity. Our model, developed with OHM code, suggests these current ribbons, which develop at location EUV brightenings seen AIA imagery, are driven collapse flare's coronal layer. These...
We compute the three-dimensional magnetic field of an active region in order to study configuration filaments. The nonlinear force-free model is adopted above photosphere, where vector was observed by THEMIS/MTR on 2005 May 27. propose a new method remove 180° ambiguity transverse field. Next, we analyze implications preprocessing data minimizing total force and torque fields. This step provides consistent bottom boundary condition for model. Then, using optimization coronal field, find flux...
We address the formation of three-dimensional nullpoint topologies in solar corona by combining Hinode/X-ray Telescope (XRT) observations a small dynamic limb event, which occurred beside non-erupting prominence cavity, with (3D) zero-β magnetohydrodynamics (MHD) simulation. To this end, we model boundary-driven "kinematic" emergence compact, intense, and uniformly twisted flux tube into potential field arcade that overlies weakly coronal rope. The expansion emerging gives rise to at...
In this paper we show that when accurate nonlinear force-free field (NLFFF) models are analyzed together with high-resolution magnetohydrodynamic (MHD) simulations, can determine the physical causes for coronal mass ejection (CME) eruption on 2007 February 12. We compare geometrical and topological properties of three-dimensional magnetic fields given by both methods in their pre-eruptive phases. arrive at a consistent picture evolution sigmoid. Both MHD simulation observed flux cancellation...
We present SDO/AIA observations of an eruptive X-class flare July 12, 2012, and compare its evolution with the predictions a 3D numerical simulation. focus on dynamics loops that are seen to undergo slipping reconnection during flare. In AIA 131A observations, lower parts 10 MK exhibit apparent motion velocities several tens km/s along developing ribbons. early stages flare, ribbons consist compact, localized bright transition-region emission from footpoints loops. A DEM analysis shows have...