Publications

2019

• Event detection from multiple spacecraft in-situ measurement using Deep Learning
  
  • Nguyen Gautier
  • Fontaine Dominique
  • Aunai Nicolas
  • Jeandet Alexis
  • Choimet Vianney
  , 2019, pp.15161.
• Fire hose instability observed between the reconnection sites in the Earth's magnetotail
  
  • Alexandrova Alexandra
  • Retinò Alessandro
  • Divin A. V.
  • Matteini Lorenzo
  • Le Contel Olivier
  • Breuillard Hugo
  • Catapano F.
  • Cozzani Giulia
  • Deca J.
  , 2019, pp.16083.
• Optimal Use of Time Lags Between MMS Spacecraft : Application to the Estimation of Wave-Vectors
  
  • Chanteur Gérard
  • Le Contel Olivier
  • Retinò Alessandro
  • Turner Drew L.
  , 2019, pp.5561.
• The Search-Coil Magnetometer onboard ESA JUICE mission
  
  • Retinò Alessandro
  • Mansour Malik
  • Chust Thomas
  • Le Contel Olivier
  • Canu Patrick
  • Sahraoui Fouad
  • Alison Dominique
  • Varizat Laurent
  • Lebassard Mathieu
  • Jeandet Alexis
  • Geyskens N.
  • Berthod Christophe
  • Chariet M.
  • Leray Vincent
  • Techer Jean-Denis
  • Sou Gérard
  • Cecconi B.
  • Bergman J.
  • Wahlund Jan Erik
  , 2019, pp.9398.
• MMS-Cluster joint observations of plasma sheet boundary layer crossings
  
  • Le Contel Olivier
  • Retinò Alessandro
  • Alexandrova Alexandra
  • Chust Thomas
  • Canu Patrick
  • Fontaine Dominique
  • Toledo-Redondo Sergio
  • Jacquey C.
  • Lavraud Benoit
  • Kiehas Stefan
  • Nakamura R.
  • Khotyaintsev Y. V.
  • Wilder Frederick D.
  • Gershman D. J.
  • Strangeway Robert J.
  • Plaschke Ferdinand
  • Argall Matthew R.
  • Turner Drew L.
  • Cohen Ian J.
  • Burch James L.
  , 2019, pp.14922.
• Structure of the Electron Diffusion Region in Vlasov-Darwin simulations of magnetic reconnection
  
  • Cozzani Giulia
  • Califano F.
  • Pezzi O.
  • Retinò Alessandro
  • Valentini F.
  • Guarrasi Massimiliano
  , 2019, pp.18807.
• Plasma transport at Mercury and its relation with Hermean space weather
  
  • Delcourt Dominique
  , 2019. Space weather deals with a number of aspects of the solar wind interaction with planetary environments, be they magnetized or not. In this talk, I will review some of these aspects in the miniature magnetosphere of Mercury. In this magnetosphere, MESSENGER observations have revealed a variety of structural and dynamical features similar to those at Earth such as dayside cusps at high latitudes and a nightside magnetotail due to the weak (northward shifted) intrinsic magnetic field of the planet, or global topological reconfigurations with frequent reconnection events in the frontside and tail regions as well as short-lived dipolarizations. However, the characteristic spatial and temporal scales of these events are here much smaller than those occurring at Earth. I will discuss some features of plasma transport and acceleration in this miniature magnetosphere of Mercury, starting from solar wind entry in the cusp and subsequent transport in the plasma mantle and plasma sheet, then addressing circulation of planetary material and its energization due to convection or impulsive electric fields, followed by magnetospheric escape or precipitation onto the planet surface. The common knowledge of Mercury's magnetized environment that has been acquired from MESSENGER datasets and theoretical/numerical studies will be considerably expanded with the forthcoming observations of the extensive plasma payload onboard the BepiColombo mission that was launched on October 20, 2018 and that will reach Mercury in December 2025.
• Acceleration of plasma in current sheet during substorm dipolarizations in the Earth’s magnetotail : Comparison of different mechanisms
  
  • Parkhomenko E.
  • Malova Helmi
  • Delcourt Dominique
  • Zelenyi Lev
  , 2019.
• Comparison of current sheets in solar wind and planetary magnetospheres
  
  • Malova Helmi
  • Delcourt Dominique
  • Zelenyi Lev
  , 2019. Current sheets are structures that can be formed at the boundaries of different plasmas, magnetic fluxes and in areas with strong field gradients. When current sheets thicknesses become comparable with proton gyroradii they can play a key role of reservoirs of a free magnetic energy that can be released due to development of different current sheet instabilities. Such comparatively thin current sheets were relatively recently discovered by space missions in the magnetospheres of the Earth and planets, as well as in the solar wind. The development of a self-consistent current sheet theory in collisionless plasma has relatively long and dramatic history. The solution of the problem of thin current sheet structure and stability become possible in a frame of a kinetic quasi-adiabatic approach explaining multiscale embedded structure of thin current sheets and their metastability. We showed that the structure and stability of current structures are completely determined by the nonlinear dynamics of plasma particles within them. The similarity and difference of the current sheets in the solar wind and planetary magnetospheres are presented. Development of theoretical approaches to investigation of different current systems in space are discussed.
• Automatic Detection of Interplanetary Coronal Mass Ejections from In Situ Data: A Deep Learning Approach
  
  • Nguyen Gautier
  • Aunai Nicolas
  • Fontaine Dominique
  • Le Pennec Erwan
  • van den Bossche Joris
  • Jeandet Alexis
  • Bakkali Brice
  • Vignoli Louis
  • Regaldo-Saint Blancard Bruno
  The Astrophysical Journal, American Astronomical Society, 2019, 874 (2), pp.145. Decades of studies have suggested several criteria to detect Interplanetary coronal mass ejections (ICME) in time series from in-situ spacecraft measurements. Among them the most common are an enhanced and smoothly rotating magnetic field, a low proton temperature and a low plasma beta. However, these features are not all observed for each ICME due to their strong variability. Visual detection is time-consuming and biased by the observer interpretation leading to non exhaustive, subjective and thus hardly reproducible catalogs. Using convolutional neural networks on sliding windows and peak detection, we provide a fast, automatic and multi-scale detection of ICMEs. The method has been tested on the in-situ data from WIND between 1997 and 2015 and on the 657 ICMEs that were recorded during this period. The method offers an unambiguous visual proxy of ICMEs that gives an interpretation of the data similar to what an expert observer would give. We found at a maximum 197 of the 232 ICMEs of the 2010-2015 period (recall 84 +-4.5 % including 90% of the ICMEs present in the lists of Nieves-Chinchilla et al. (2015) and Chi et al. (2016). The minimal number of False Positives was 25 out of 158 predicted ICMEs (precision 84+-2.6%). Although less accurate, the method also works with one or several missing input parameters. The method has the advantage of improving its performance by just increasing the amount of input data. The generality of the method paves the way for automatic detection of many different event signatures in spacecraft in-situ measurements. (10.3847/1538-4357/ab0d24)
  DOI : 10.3847/1538-4357/ab0d24
• In situ spacecraft observations of a structured electron diffusion region during magnetopause reconnection
  
  • Cozzani Giulia
  • Retinò Alessandro
  • Califano Francesco
  • Alexandrova Alexandra
  • Le Contel Olivier
  • Khotyaintsev Yuri
  • Vaivads Andris
  • Fu Huishan S
  • Catapano F.
  • Breuillard Hugo
  • Ahmadi Narges
  • Lindqvist Per-Arne
  • Ergun Robert E. E
  • Torbert Robert B. B
  • Giles Barbara L. L
  • Russell Christopher T. T
  • Nakamura Rumi
  • Fuselier Stephen
  • Mauk Barry H. H
  • Moore Thomas
  • Burch James L. L
  Physical Review E, American Physical Society (APS), 2019, 99 (4), pp.043204 (2019). The Electron Diffusion Region (EDR) is the region where magnetic reconnection is initiated and electrons are energized. Because of experimental difficulties, the structure of the EDR is still poorly understood. A key question is whether the EDR has a homogeneous or patchy structure. Here we report Magnetospheric MultiScale (MMS) novel spacecraft observations providing evidence of inhomogeneous current densities and energy conversion over a few electron inertial lengths within an EDR at the terrestrial magnetopause, suggesting that the EDR can be rather structured. These inhomogenenities are revealed through multi-point measurements because the spacecraft separation is comparable to a few electron inertial lengths, allowing the entire MMS tetrahedron to be within the EDR most of the time. These observations are consistent with recent high-resolution and low-noise kinetic simulations. (10.1103/PhysRevE.99.043204)
  DOI : 10.1103/PhysRevE.99.043204
• États stationnaires des plasmas de tokamak en MHD visco-résistive
  
  • Oueslati Hanen
  • Firpo Marie-Christine
  • Salhi A.
  , 2019.
• On the necessity of GPS networking in Africa
  
  • Amory-Mazaudier Christine
  • Fleury Rolland
  • Masson F.
  , 2019.
• CF 4 /H 2 Plasma Cleaning of Graphene Regenerates Electronic Properties of the Pristine Material
  
  • Ferrah Djawhar
  • Renault Olivier
  • Marinov Daniil
  • Arias-Zapata Javier
  • Chevalier Nicolas
  • Mariolle Denis
  • Rouchon Denis
  • Okuno Hanako
  • Bouchiat Vincent
  • Cunge Gilles
  ACS Applied Nano Materials, American Chemical Society, 2019, 2 (3), pp.1356-1366. The impact on the electronic and structural properties of chemical vapor deposition (CVD) graphene transferred onto SiO2/silicon (Si) of continuous H2-based plasmas, used to remove sticky residues composed of poly(methyl methacrylate) (PMMA) and Si-based nanoparticles at the surface, was investigated. By combining X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), we found that H2 plasma treatment, which allows the simultaneous etching of Si-based nanoparticles and PMMA, causes fragmentation of a CVD graphene layer into nanoplatelets and subsequent etching of the uncovered SiO2/Si surface. We added CF4 to the H2 plasma to allow the selective etching of Si-based impurities while maintaining the quality and stability of the CVD graphene. The increase in the sp2/sp3 ratio and decrease in the Si–C bonds, evaluated from XPS analysis, reveal the removal of all residual contamination. AFM analysis confirms the efficient and selective etching of residues from the surface of graphene, which displays a microscopic corrugation due to a weak coupling with the SiO2/Si substrate. The established CF4/H2 plasma processing generates, however, cracks along the grain boundaries in CVD graphene, which is responsible for the unusual transport properties. Characterization of local chemical structures using Raman spectroscopy reveals that the CVD graphene layer is essentially undamaged under the CF4/H2 plasma and dehydrogenation is incomplete in the subsequent annealing at 400 °C. The local electronic structure is probed using reciprocal-space photoemission electron microscopy (k-PEEM) and reveals a small, negative shift below 0.1 eV of the Dirac point with respect to the Fermi level, which is consistent with n doping caused by trapped hydrogen species at the interface. Threshold photoemission electron microscopy (PEEM) analysis establishes the work function of CVD graphene as 4.57 eV. This study reveals that the optimized cleaning process almost recovers the original properties of quasi-freestanding graphene. (10.1021/acsanm.8b02249)
  DOI : 10.1021/acsanm.8b02249
• Kinetics of N2:O2 mixtures at high specific delivered energy: peculiarities of the fast gas heating and dissociation of molecular nitrogen by a high-current nanosecond discharge
  
  • Lepikhin N D
  • Popov N.A.
  • Starikovskaia Svetlana
  , 2019.
• Opening chemical reaction paths in a plasma global model: an uncertainty quantification approach
  
  • Marmuse Florian
  • Lucken Romain
  • Le Maitre Olivier
  • Congedo Pietro
  • Sisourat Nicolas
  • Bourdon Anne
  , 2019.
• Performance of the new formulation of the bottomside B2 parameter in NeQuick model under disturbed geomagnetic conditions
  
  • Alazo-Cuartas K.
  • Migoya-Orué Yenca
  • Radicella S.
  • Nava B.
  • Amory-Mazaudier Christine
  , 2019.
• Investigation of electron beam effects on L -shell Mo plasma produced by a compact LC generator using pattern recognition
  
  • Yilmaz M.
  • Danisman Y.
  • Ozdemir M.
  • Karlık B.
  • Larour J.
  Matter and Radiation at Extremes, AIP Publishing, 2019, 4 (2). In this paper, the effects of an electron beam on X-pinch-produced spectra of L-shell Mo plasma are investigated for the first time by principal component analysis (PCA); this analysis is compared with that of line ratio diagnostics. A spectral database for PCA extraction is arranged using a non-Local Thermodynamic Equilibrium (non-LTE) collisional radiative L-shell Mo model. PC vector spectra of L-shell Mo, including F, Ne, Na and Mg-like transitions are studied to investigate the polarization types of these transitions. PC1 vector spectra of F, Ne, Na and Mg-like transitions result in linear polarization of Stokes Q profiles. Besides, PC2 vector spectra show linear polarization of Stokes U profiles of 2p53s of Ne-like transitions which are known as responsive to a magnetic field [Träbert, Beiersdorfer, and Crespo López-Urrutia, Nucl. Instrum Methods Phys. Res., Sect. B 408, 107–109 (2017)]. A 3D representation of PCA coefficients demonstrates that addition of an electron beam to the non-LTE model generates quantized, collective clusters which are translations of each other that follow V-shaped cascade trajectories, except for the case f = 0.0. The extracted principal coefficients are used as a database for an Artificial Neural Network (ANN) to estimate the plasma electron temperature, density and beam fractions of the time-integrated, spatially resolved L-shell Mo X-pinch plasma spectrum. PCA-based ANNs provide an advantage in reducing the network topology, with a more efficient backpropagation supervised learning algorithm. The modeled plasma electron temperature is about Te ∼ 660 eV and density ne = 1 × 1020 cm−3, in the presence of the fraction of the beams with f ∼ 0.1 and centered energy of 5 keV. (10.1063/1.5081676)
  DOI : 10.1063/1.5081676
• Novel diagnostics to unravel fundamental processes in oxygen plasmas
  
  • Booth Jean-Paul
  , 2019. Electrical discharges in oxygen gas are widespread in nature and occur in many plasma applications such as surface treatment and plasma medicine. They are also an ideal archetype for the understanding of molecular plasmas, showing the effects of dissociation/surface recombination, electron attachment, high densities of molecular and atomic metastable states, vibrational excitation and gas heating. Nevertheless, many uncertainties remain about the cross-section and reaction sets, as well as the surface processes, all essential for reliable modelling. We are making comprehensive measurements absolute densities and kinetics of the principal transient species in a well-characterised and reproducible system, a DC positive column in pure O2. This provides a uniform plasma column with constant reduced field over a wide range of gas pressure and electron density (pressure 0.2-10 Torr, current 5-40 mA), ideal for model validation or improvement. A range of powerful diagnostic techniques are employed, including vacuum ultraviolet (120-200nm) absorption spectroscopy, cavity ringdown spectroscopy (CRDS), time resolved optical emission spectroscopy and high resolution two-photon laser-induced fluorescence (HR-TALIF) The Fourier-Transform branch of the unique DESIRS beamline at synchrotron Soleil was used to record absorption spectra with a resolution of 106, giving complete high-resolution spectra of O2 in the X, a and b states. The absorption cross-sections of O2 X and a are known, allowing absolute densities to be determined. Using a combination of ab-initio calculations and absolute emission spectrometry, we have derived the first absolute absorption cross-sections of O2 b, and therefore made the first the absolute measurements of density in this state. Time-resolved measurements of O2 X, a and b during both full and partial modulation of the discharge current, using the monochromatic branch of the VUV beamline, allowing their creation and loss kinetics (in the gas phase and on the tube surface) to be probed. The electron-impact dissociation coefficient is poorly known at low reduced electric field, but it can be determined from measurements of the absolute density of oxygen atoms, combined with loss rate measurements (from time-resolved emission). However, the absolute density is hard to measure accurately. Unfortunately, the resonance lines at 130nm are entirely saturated and therefore useless. Therefore we have developed cavity-ringdown spectroscopy at 630nm (using the forbidden 1D ← 3P transition), allowing the density to be determined with an accuracy better than 10%. Additionally the O- negative ion density can be determined from the photodetachment continuum in this spectral region.
• Novel diagnostics to unravel fundamental processes in oxygen plasmas
  
  • Booth Jean-Paul
  • Chatterjee Abhyuday
  • Guaitella Olivier
  • Drag Cyril
  • Lopaev Dmitry
  • Zyryanov Sergey
  • Rakhimova Tatyana
  • de Oliveira N.
  • Nahon L.
  • Western Colin
  , 2019.
• Transport and energization of planetary ions in the magnetospheric flanks of Mercury
  
  • Aizawa Sae
  , 2019. The transport and energization of planetary ions within Kelvin-Helmholtz (KH) vortices developing in the magnetospheric flanks of Mercury are investigated using both numerical methods and data analysis. Due to the presence of heavy ions of planetary origin (e.g., O^+, Na^+, and K^+) and the complicated field structure present during the KH vortex development, the scale of electric field variations can be comparable to that of the ion gyromotion. Therefore, ions may experience non-adiabatic energization as they drift across the magnetopause. In this study, we focus on the effects of the spatial/temporal variations of the electric field along the ion path. We show that the intensification, rather than the change in orientation, is responsible for large non-adiabatic energization of heavy ions of planetary origin. This energization systematically occurs for ions with low initial energies in the direction perpendicular to the magnetic field. The energy gain is of the order of the energy corresponding to the maximum ExB drift speed. It is also found that the ion transport across the magnetopause is controlled by the orientation of the magnetosheath electric field. Analyzing data from MESSENGER allow us to compare the observational facts with our numerical results. We find that the counts of Na^+-group detected by FIPS increase with the existence of KH waves, which is consistent with our numerical results. Although some differences in the energy distribution are expected in our numerical results, the data show no significant differences. This will be the subject of further studies using the newly developed BepiColombo instruments.
• Turbulence-Driven Ion Beams in the Magnetospheric Kelvin-Helmholtz Instability
  
  • Sorriso-Valvo L.
  • Catapano F.
  • Retinò Alessandro
  • Le Contel Olivier
  • Perrone Denise
  • Roberts Owen W.
  • Coburn Jesse T.
  • Panebianco Vincenzo
  • Valentini F.
  • Perri S.
  • Greco A.
  • Malara Francesco
  • Carbone V.
  • Veltri P.
  • Pezzi O.
  • Fraternale Federico
  • Di Mare Francesca
  • Marino Raffaele
  • Giles B. L.
  • Moore T. E.
  • Russell Christopher T.
  • Torbert Roy B.
  • Burch Jim L.
  • Khotyaintsev Y. V.
  Physical Review Letters, American Physical Society, 2019, 122, pp.035102. The description of the local turbulent energy transfer and the high-resolution ion distributions measured by the Magnetospheric Multiscale mission together provide a formidable tool to explore the cross-scale connection between the fluid-scale energy cascade and plasma processes at subion scales. When the small-scale energy transfer is dominated by Alfvénic, correlated velocity, and magnetic field fluctuations, beams of accelerated particles are more likely observed. Here, for the first time, we report observations suggesting the nonlinear wave-particle interaction as one possible mechanism for the energy dissipation in space plasmas. (10.1103/PhysRevLett.122.035102)
  DOI : 10.1103/PhysRevLett.122.035102
• Observations of Flux Ropes With Strong Energy Dissipation in the Magnetotail
  
  • Huang S. y
  • Jiang K.
  • Yuan Z.
  • Zhou M.
  • Sahraoui Fouad
  • Fu H.
  • Deng X. H
  • Khotyaintsev Yu.
  • Yu X. D
  • He L. H
  • Deng D.
  • Pollock C. J
  • Torbert R. B
  • Burch J. L
  Geophysical Research Letters, American Geophysical Union, 2019, 46 (2), pp.580-589. An ion-scale flux rope (FR), embedded in a high-speed electron flow (possibly an electron vortex), is investigated in the magnetotail using observations from the Magnetospheric Multiscale (MMS) spacecraft. Intense electric field and current and abundant waves are observed in the exterior and interior regions of the FR. Comparable parallel and perpendicular currents in the interior region imply that the FR has a non-force-free configuration. Electron demagnetization occurs in some subregions of the FR. It is surprising that strong dissipation (J × E' up to 2,000 pW/m 3) occurs in the center of the FR without signatures of secondary reconnection or coalescence of two FRs, implying that FR may provide another important channel for energy dissipation in space plasmas. These features indicate that the observed FR is still highly dynamical, and hosts multiscale coupling processes, even though the FR has a very large scale and is far away from the reconnection site. Plain Language Summary Flux ropes, 3-D helical magnetic structures, in which magnetic field lines twist with each other, play an important role in the macroscopic and microscopic physical process during magnetic reconnection. Most of previous studies focused on the flux ropes in the reconnection region. However, some physical process inside macroscopic flux ropes far away from the reconnection site in the magnetotail is still unclear due to the lack of high time resolution data. In this letter, thanks to the unprecedented high time resolution data of the Magnetospheric Multiscale (MMS) mission, we report an ion-scale flux rope and study its dynamics. Our observations demonstrate that the observed flux rope is still highly dynamical, and hosting multiscale coupling processes and strong energy dissipation, even though the flux rope has very large scale and is far away from the reconnection site. (10.1029/2018GL081099)
  DOI : 10.1029/2018GL081099
• Streamer-to-filamentary transition and electron temperature measurement in positive polarity nanosecond surface discharge between 1 and 10 bar
  
  • Ding Chenyang
  • Shcherbanev S.A.
  • Chng Tat Loon
  • Popov N.A.
  • Starikovskaia Svetlana
  , 2019, pp.AIAA 2019-0462.
• Atomic nitrogen density measurements in a nanosecond capillary discharge
  
  • Chng Tat Loon
  • Lepikhin N D
  • Orel Inna
  • Popov N.A.
  • Starikovskaia Svetlana
  , 2019. This paper forms part of a larger study geared towards examining the atomic nitrogen production as a function of reduced electric fields, particularly in nanosecond type discharges. In this study, the atomic nitrogen density in a pure molecular nitrogen capillary discharge at 27 mbar is measured using two-photon absorption laser induced fluorescence (TALIF). Due to its small volume, the capillary provides an ideal geometry for achieving high levels of specific deposited energy into the plasma (> 1 eV per molecule) as well as high peak reduced electric fields (> 500 Td). Under these conditions, our results show that unusually high densities of atomic nitrogen are recorded, with the time evolution measurements indicating a peak dissociation fraction of slightly more than 10%. Further validation of these results with numerical simulations are ongoing, but on the current basis, support the notion that the capillary discharge is an extremely efficient configuration for the generation of nitrogen atoms. (10.2514/6.2019-0745)
  DOI : 10.2514/6.2019-0745