Publications

2020

Analysis of energy conversion processes at kinetic scales associated with a series of dipolarization fronts observed by MMS during a substorm
- Alqeeq Soboh
- Le Contel Olivier
- Canu Patrick
- Retinò Alessandro
- Chust Thomas
- Mirioni Laurent
, 2020. In July 2017, the MMS constellation was in the magnetotail with an apogee of 25 Earth radii and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23 July around 16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static state. Then, MMS suddenly entered in the central plasma sheet and detected the local onset of a small substorm as indicated by the AE index (~400 nT). Fast earthward plasma flows were measured for about 1 hour starting with a period of quasi-steady flow and followed by a saw-tooth like series of fast flows associated with dipolarization fronts. This plasma transport sequence finished with a flow reversal still occurring close to the magnetic equator. In the present study, we investigate the energy conversion processes at ion and electron scales for these different phases with particular attention on the processes in the vicinity of the dipolarization fronts. (10.5194/egusphere-egu2020-19750)
DOI : 10.5194/egusphere-egu2020-19750
MMS-Cluster conjugate observation of disturbance in the current sheet associated with localized fast flow in the near-Earth magnetotail
- Nakamura Rumi
- Baumjohann Wolfgang
- Birn Joachim
- Burch Jim
- Carr Chris
- Dandouras Iannis
- Escoubet Philippe
- Fazakerley Andrew
- Giles Barbara
- Kubyshkina Marina
- Le Contel Olivier
- Nagai Tsugunobu
- Nakamura Takuma
- Panov Evgeny
- Russell Chris
- Sergeev Victor
- Torbert Roy
, 2020. We report the evolution of the current sheet associated with a localized flow burst in the near-Earth magnetotail on Sep. 8, 2018 around 14 UT when MMS (Magnetospheric Multiscale) and Cluster at about X=17 RE, separated mainly in the dawn-dusk direction at a distance of about 4 RE, encountered at duskside and dawnside part of a dipolarization front, respectively.&#160; We analyzed the mesoscale current sheet disturbances based on multi-point data analysis between Cluster and MMS. It is shown that the current sheet thickens associated with the passage of the dipolarization front confirming results from previous statistical studies. The thickness of the current sheet, however, decreased subsequently, before recovering toward the original configuration. MMS observed enhanced field aligned currents exclusively during this thinning of the current sheet at the off-equatorial region. Multiple layers of small-scale, intense field-aligned currents accompanied by enhanced Hall-currents were detected at this region.&#160; Based on these mesoscale and microscale multipoint observations, we infer the current structures around the localized flow and discuss the role of these mesoscale flow processes in the larger-scale magnetotail dynamics.&#160;&#160; (10.5194/egusphere-egu2020-3254)
DOI : 10.5194/egusphere-egu2020-3254
In situ spacecraft observations of structured electron diffusion regions during magnetic reconnection
- Cozzani Giulia
- Retinò Alessandro
- Califano Francesco
- Alexandrova Alexandra
- Khotyaintsev Yuri
- André Mats
- Catapano Filomena
- Fu Huishan
- Le Contel Olivier
- Vaivads Andris
- Ahmadi Narges
- Breuillard Hugo
, 2020. Magnetic reconnection is a fundamental energy conversion process in plasmas. It occurs in thin current sheets, where a change in the magnetic field topology leads to rapid heating of plasma, plasma bulk acceleration and acceleration of plasma particles. To allow for magnetic field reconfiguration, both ions and electrons must be demagnetized. The ion and electron demagnetization &#160;take place in the ion and electron diffusion regions respectively, in both cases at kinetic scales. For the first time, Magnetospheric Multiscale (MMS) spacecraft observations, at inter-spacecraft separation comparable to the electron inertial length, allow for a multi-point analysis of the electron diffusion region (EDR). A key question is whether the EDR has a homogeneous or patchy structure.&#160;Here we report MMS observations at the magnetopause providing evidence of inhomogeneous current densities and energy conversion over a few (&#8764; 3 de) electron inertial lengths suggesting that the EDR can be structured at electron scales. In particular, the energy conversion is patchy and changing sign in the vicinity of the reconnection site implying that the EDR comprises regions where energy is transferred from the field to the plasma and regions with the opposite energy transition, which is unexpected during reconnection. The origin of the patchy energy conversion appears to be connected to the large ve,N &#8764; ve,M directed from the magnetosphere to magnetosheath. These observations are consistent with recent high-resolution and low-noise kinetic simulations of asymmetric reconnection.&#160;Patchy energy conversion is observed also in an EDR at the magnetotail, where the inter-spacecraft separation was &#8764; 1 de. Electric field measurements are different among the spacecraft suggesting inhomogeneities at the electron scale. However, in this case the current density appear homogeneous in the EDR suggesting that the structuring may be sourced from a different kind of electron dynamics in the magnetotail. (10.5194/egusphere-egu2020-13405)
DOI : 10.5194/egusphere-egu2020-13405
First observations of the Search Coil Magnetometer on Solar Orbiter / RPW: results and performances
- Kretschmar Matthieu
- Krasnoselskikh Volodya
- Brochot Jean-Yves
- Jannet Guillaume
- Dudok de Wit Thierry
- Froment Clara
- Maksimovic Milan
- Chust Thomas
- Le Contel Olivier
- Soucek Jan
- Pisa David
, 2020, pp.EGU2020-19143. (10.5194/egusphere-egu2020-19143)
DOI : 10.5194/egusphere-egu2020-19143
Reconnection site and ion scale turbulence generation
- Vaivads Andris
- Liu Chengming
- Khotyaintsev Yuri
- Graham Daniel
- Lindqvist Per-Arne
- Torbert Roy
- Burch Jim
- Russell Christopher
- Contel Olivier Le
- Giles Barbara
- Gershman Daniel
, 2020. We analyze in detail a reconnection site observed by the Magnetospheric Multiscale (MMS) mission in the magnetotail. The interval around the X-line is identified based on the ion jet reversal, Hall electric fields and other reconnection signatures. At the reconnection site strong electric fields with amplitudes above 100mV/m are observed. In addition, the region shows strong turbulent variations on ion scales, including magnetic island-like structures. We discuss the cause of strong electric fields, their relation to ion scale structures and associated particle acceleration in this region. Of particular interest is the relation of the reconnection site to the generation of kinetic Alfven waves. (10.5194/egusphere-egu2020-11451)
DOI : 10.5194/egusphere-egu2020-11451
The RPW Low Frequency Receiver (LFR) on Solar Orbiter: in-situ LF electric and magnetic field measurements of the solar wind expansion
- Chust Thomas
- Le Contel Olivier
- Berthomier Matthieu
- Retinò Alessandro
- Sahraoui Fouad
- Jeandet Alexis
- Leroy Paul
- Pellion Jean-Christophe
- Bouzid V.
- Katra Bruno
- Piberne Rodrigue
- Khotyaintsev Yuri
- Vaivads Andris
- Krasnoselskikh Volodya
- Kretzschmar Matthieu
- Souček Jan
- Santolík Ondřej
- Maksimovic Milan
- Bale Stuart D.
, 2020, pp.10050. (10.5194/egusphere-egu2020-10050)
DOI : 10.5194/egusphere-egu2020-10050
Turbulence driven widening of the near-SOL power width in ASDEX Upgrade H-Mode discharges
- Eich T.
- Manz P.
- Goldston R.J.
- Hennequin Pascale
- David P.
- Faitsch M.
- Kurzan B.
- Sieglin B.
- Wolfrum E.
Nuclear Fusion, IOP Publishing, 2020, 60 (5), pp.056016. (10.1088/1741-4326/ab7a66)
DOI : 10.1088/1741-4326/ab7a66
Latitudinal Dependence of the Kelvin‐Helmholtz Instability and Beta Dependence of Vortex‐Induced High‐Guide Field Magnetic Reconnection
- Vernisse Y.
- Lavraud B.
- Faganello M.
- Fadanelli S.
- Sisti M.
- Califano F.
- Eriksson S.
- Gershman D.
- Dorelli J.
- Pollock C.
- Giles B.
- Avanov L.
- Burch J.
- Dargent Jérémy
- Ergun R.
- Farrugia C. J.
- Génot V.
- Hasegawa H.
- Jacquey C.
- Kacem I.
- Kieokaew R.
- Kuznetsova M.
- Moore T.
- Nakamura T.
- Paterson W.
- Penou E.
- Phan T. D.
- Russell C. T.
- Saito Y.
- Sauvaud J.-A.
- Toledo‐redondo S.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2020, 125 (5), pp.e2019JA027333. We investigate both large‐ and small‐scale properties of a Kelvin‐Helmholtz (KH) event at the dusk flank magnetopause using Magnetospheric Multiscale observations on 8 September 2015. We first use two types of 3‐D simulations (global and local) to demonstrate that Magnetospheric Multiscale is close to the most KH unstable region, and so the occurrence of vortex‐induced reconnection may be expected. Because they produce low‐shear current sheets, KH vortices constitute a perfect laboratory to investigate magnetic reconnection with large guide field and low asymmetry. Recent works suggest that magnetic reconnection may be suppressed when a current sheet combines large guide field and pressure gradient (which induces a diamagnetic drift). We thus perform a statistical analysis of high‐resolution data for the 69 KH‐induced low‐shear magnetic reconnection events observed on that day. We find that the suppression mechanism is not at work for most of the observed reconnecting current sheets, as predicted, but we also find that almost all nonreconnecting current sheets should be reconnecting according to this model. This confirms the fact that the model provides a necessary but not sufficient condition for reconnection to occur. Finally, based on the same data set, we study the latitudinal distribution of these magnetic reconnection events combined with global magnetospheric modeling. We find that reconnection associated with KH vortices occurs over a significant range of latitudes at the flank magnetopause. It is not confined to the plane where the growth rate is maximum, in agreement with recent 3‐D simulations. (10.1029/2019JA027333)
DOI : 10.1029/2019JA027333
Observations of the Source Region of Whistler Mode Waves in Magnetosheath Mirror Structures
- Kitamura N.
- Omura Y.
- Nakamura S.
- Amano T.
- Boardsen S.
- Ahmadi N.
- Le Contel O.
- Lindqvist P.‐a.
- Ergun R.
- Saito Y.
- Yokota S.
- Gershman D.
- Paterson W.
- Pollock C.
- Giles B.
- Russell C. T.
- Strangeway R.
- Burch J.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2020, 125 (5). In the magnetosheath, intense whistler mode waves, called “Lion roars,” are often detected in troughs of magnetic field intensity in mirror mode structures. Using data obtained by the four Magnetospheric Multiscale (MMS) spacecraft, we show that reversals of gradient of magnetic field intensity along the magnetic field correspond to reversals of the field‐aligned component of Poynting flux of whistler mode waves in the troughs. Such a characteristic is consistent with the idea that the whistler mode waves are effectively generated near the local minima of magnetic field intensity because of the smallest cyclotron resonance velocity and propagate toward regions of larger magnetic field intensity along the magnetic field lines on both sides. We use the reversal of the Poynting flux as an indicator of wave source regions. In these regions, we find that pancake or an outer edge of butterfly electron distributions above ~100 eV are good candidates for wave generation. Unclear correlations of phase difference and amplitude variations of whistler mode waves in cases of ~40 km spacecraft separation indicate that a simple plane wave approximation with a constant amplitude is not valid at this spatial scale that is much smaller than the ion gyroradius. The whistler mode waves consist of small coherent wave packets from multiple sources with spatial scales smaller than tens of electron gyroradii transverse to the background magnetic field in a mirror mode structure. Publication cover image (10.1029/2019JA027488)
DOI : 10.1029/2019JA027488
Cold-Atmospheric Plasma Induces Tumor Cell Death in Preclinical In Vivo and In Vitro Models of Human Cholangiocarcinoma
- Vaquero Javier
- Judée Florian
- Vallette Marie
- Decauchy Henri
- Arbelaiz Ander
- Aoudjehane Lynda
- Scatton Olivier
- Gonzalez-Sanchez Ester
- Merabtene Fatiha
- Augustin Jeremy
- Housset Chantal
- Dufour Thierry
- Fouassier Laura
Cancers, MDPI, 2020, 12 (5), pp.1280. Through the last decade, cold atmospheric plasma (CAP) has emerged as an innovative therapeutic option for cancer treatment. Recently, we have set up a potentially safe atmospheric pressure plasma jet device that displays antitumoral properties in a preclinical model of cholangiocarcinoma (CCA), a rare and very aggressive cancer emerging from the biliary tree with few efficient treatments. In the present study, we aimed at deciphering the molecular mechanisms underlying the antitumor effects of CAP towards CCA both in an in vivo and in vitro context. In vivo, using subcutaneous xenografts into immunocompromised mice, CAP treatment of CCA induced DNA lesions and tumor cell apoptosis, as evaluated by 8-oxoguanine and cleaved caspase-3 immunohistochemistry, respectively. Analysis of the tumor microenvironment showed changes in markers related to macrophage polarization. In vitro, incubation of CCA cells with CAP-treated culture media (i.e. plasma-activated media, PAM) led to a dose response decrease in cell survival. At molecular level, CAP treatment induced double-strand DNA breaks, followed by an increased phosphorylation and activation of the cell cycle master regulators CHK1 and p53, leading to cell cycle arrest and cell death by apoptosis. In conclusion, CAP is a novel therapeutic option to consider for CCA in the future. (10.3390/cancers12051280)
DOI : 10.3390/cancers12051280
Inertial/kinetic-Alfvén wave turbulence: A twin problem in the limit of local interactions
- Galtier Sebastien
- David Vincent
Physical Review Fluids, American Physical Society, 2020, 5 (4), pp.044603. Inertial and kinetic-Alfvén wave turbulences have a priori little in common: indeed, the first one concerns rotating hydrodynamics in the limit of a small Rossby number (with 0 the rotating rate) while the second describes high frequency plasmas in the limit of a strong uniform magnetic field B 0. In this paper we show analytically that, in the limit of local interactions in the perpendicular direction to 0 , the inertial wave turbulence equation converges towards the same nonlinear diffusion equation as for kinetic-Alfvén waves when the same limit is taken; the only difference resides in the constants in front of the equations. Therefore, both systems share the same physical properties for the stationary phase with an energy spectrum in k −5/2 ⊥ ; it is preceded by a self-similar solution of the second kind during the nonstationary phase with a spectrum proportional to k −8/3 ⊥ which propagates explosively towards small scales. It is suggested that the proximity between these two problems may be used to better understand inertial or kinetic-Alfvén wave turbulence. (10.1103/PhysRevFluids.5.044603)
DOI : 10.1103/PhysRevFluids.5.044603
AME: A Cross-Scale Constellation of CubeSats to Explore Magnetic Reconnection in the Solar–Terrestrial Relation
- Dai Lei
- Wang Chi
- Cai Zhiming
- Gonzalez Walter
- Hesse Michael
- Escoubet Philippe
- Phan Tai
- Vasyliunas Vytenis
- Lu Quanming
- Li Lei
- Kong Linggao
- Dunlop Malcolm
- Nakamura Rumi
- He Jianshen
- Fu Huishan
- Zhou Meng
- Huang Shiyong
- Wang Rongsheng
- Khotyaintsev Yuri
- Graham Daniel
- Retinò Alessandro
- Zelenyi Lev
- Grigorenko Elena
- Runov Andrei
- Angelopoulos Vassilis
- Kepko Larry
- Hwang Kyoung-Joo
- Zhang Yongcun
Frontiers in Physics, Frontiers, 2020, 8. (10.3389/fphy.2020.00089)
DOI : 10.3389/fphy.2020.00089
Efficiency of Electromagnetic Emission by Electrostatic Turbulence in Solar Wind and Coronal Plasmas with Density Inhomogeneities
- Volokitin A.
- Krafft C.
The Astrophysical Journal Letters, Bristol : IOP Publishing, 2020, 893 (2). We present a new method to semianalytically calculate the radiation efficiency of electromagnetic waves emitted at specific frequencies by electrostatic wave turbulence in solar wind and coronal plasmas with random density fluctuations. This method is applied to the case of electromagnetic emission radiated at the fundamental plasma frequency ω p by beam-driven Langmuir wave turbulence during Type III solar bursts. It is supposed that the main radiation mechanism is the linear conversion of electrostatic to electromagnetic waves on the background plasma density fluctuations, at constant frequency. The radiation efficiency (emissivity) of such a process is larger than that obtained in the framework of models where the low frequency density fluctuations and the corresponding ion sound waves are not external but produced by the electrostatic wave turbulence itself through nonlinear wave-wave interactions. Results show that the radiation efficiency of Langmuir wave turbulence into electromagnetic emissions at ω p is nearly constant asymptotically, with the electromagnetic energy density growing linearly with time, and is proportional to the average level of density fluctuations. Comparisons with another analytical method developed by the authors and with space observations are satisfactory. (10.3847/2041-8213/ab74de)
DOI : 10.3847/2041-8213/ab74de
Antibiotics Degradation and Bacteria Inactivation in Water by Cold Atmospheric Plasma Discharges Above and Below Water Surface
- El Shaer Mohamed
- Eldaly Mohamed
- Heikal Ghada
- Sharaf Yasmine
- Diab Heba
- Mobasher Mona
- Rousseau Antoine
Plasma Chemistry and Plasma Processing, Springer Verlag, 2020, 40 (4), pp.971-983. (10.1007/s11090-020-10076-0)
DOI : 10.1007/s11090-020-10076-0
Rydberg spectra of singlet metastable states of O2
- Western C.
- Booth Jean-Paul
- Chatterjee A.
- de Oliveira N.
Molecular Physics, Taylor & Francis, 2020, pp.e1741714. Updated analyses of several singlet Rydberg states of O2 via spectra involving excitation from the metastable a1Δg and b1Σg+ states are presented. The high quality FT-VUV spectra available from the DESIRS beamline at the SOLEIL synchrotron gives significantly improved spectra compared to previous work. The Rydberg states analysed include 3pπ1Σu+ v=0-4, 3pσ1Πu v=0-2, 3pπ1u v=0-2, 4pπ1Σu+ v=0-1, 4pσ1Πu v=0 and 4pπ1Δu v=0. This is complemented by high quality ab initio calculations on the 1Σu+ and 1u Rydberg states to determine the transition moments providing the first quantitative cross sections for Rydberg – b1Σg+ transitions. These are validated against the experimental data. The results suggest the most promising candidate for determining b1Σg+ number density is likely to be the 1-0 band of the 4pπ1Σu+ – b1Σg+ transition at 131.3 nm. (10.1080/00268976.2020.1741714)
DOI : 10.1080/00268976.2020.1741714
Consistent transport properties in multicomponent two-temperature magnetized plasmas: Application to the Sun chromosphere
- Wargnier Quentin
- Alvarez-Laguna Alejandro
- Scoggins James B
- Mansour Nagi N
- Massot Marc
- Magin Thierry E.
Astronomy & Astrophysics - A&A, EDP Sciences, 2020, 635, pp.A87. A fluid model is developed for multicomponent two-temperature magnetized plasmas in chemical non-equilibrium from the partially- to fully-ionized collisional regimes. We focus on transport phenomena aiming at representing the chromosphere of the Sun. Graille et al. [M3AS 19(04):527-599, 2009] have derived an asymptotic fluid model for multicomponent plamas from kinetic theory, yielding a rigorous description of the dissipative effects. The governing equations and consistent transport properties are obtained using a multiscale Chapman-Enskog perturbative solution to the Boltzmann equation based on a non-dimensional analysis. The mass disparity between the electrons and heavy particles is accounted for, as well as the influence of the electromagnetic field. We couple this model to the Maxwell equations for the electromagnetic field and derive the generalized Ohm's law for multicomponent plasmas. The model inherits a well-identified mathematical structure leading to an extended range of validity for the Sun chromosphere conditions. We compute consistent transport properties by means of a spectral Galerkin method using the Laguerre-Sonine polynomial approximation. Two non-vanishing polynomial terms are used when deriving the transport systems for electrons, whereas only one term is retained for heavy particles. In a simplified framework where the plasma is fully ionized, we compare the transport properties for the Sun chromosphere to conventional expressions for magnetized plasmas due to Braginskii, showing a good agreement between both results. For more general partially ionized conditions, representative of the Sun chromosphere, we compute the muticomponent transport properties corresponding to the species diffusion velocities, heavy-particle and electron heat fluxes, and viscous stress tensor of the model, for a Helium-Hydrogen mixture in local thermodynamic equilibrium. The model is assessed for the 3D radiative magnetohydrodynamic simulation of a pore, in the highly turbulent upper layer of the solar convective zone. The resistive term is found to dominate mainly the dynamics of the electric field at the pore location. The battery term for heavy particles appears to be higher at the pore location and at some intergranulation boundaries. (10.1051/0004-6361/201834686)
DOI : 10.1051/0004-6361/201834686
Characterization of a kHz atmospheric pressure plasma jet: comparison of discharge propagation parameters in experiments and simulations without target
- Hofmans Marlous
- Viegas Pedro
- Rooij Olivier Van
- Klarenaar Bart
- Guaitella Olivier
- Bourdon Anne
- Sobota Ana
Plasma Sources Science and Technology, IOP Publishing, 2020, 29 (3), pp.034003. (10.1088/1361-6595/ab6d49)
DOI : 10.1088/1361-6595/ab6d49
Characterization of an Optical Pulse Slicer for Gas-Phase Electric Field Measurements Using Field-Induced Second Harmonic Generation
- Chng Tat Loon
- Ding C.
- Naphade M.
- Goldberg B.M. M
- Adamovich I.V. V
- Starikovskaia Svetlana
Journal of Instrumentation, IOP Publishing, 2020, 15 (03), pp.C03005-C03005. (10.1088/1748-0221/15/03/C03005)
DOI : 10.1088/1748-0221/15/03/C03005
TALIF measurements of atomic nitrogen in the afterglow of a nanosecond capillary discharge
- Chng Tat Loon
- Lepikhin N D
- Orel Inna
- Popov N A
- Starikovskaia Svetlana M
Plasma Sources Science and Technology, IOP Publishing, 2020, 29 (3), pp.035017. (10.1088/1361-6595/ab6f9c)
DOI : 10.1088/1361-6595/ab6f9c
Constraining the cosmic ray spectrum in the vicinity of the supernova remnant W28: from sub-GeV to multi-TeV energies
- Phan V. H. M.
- Gabici S.
- Morlino G.
- Terrier R.
- Vink J.
- Krause J.
- Menu Mélissa
Astronomy & Astrophysics - A&A, EDP Sciences, 2020, 635, pp.A40. Context. Supernova remnants interacting with molecular clouds are ideal laboratories to study the acceleration of particles at shock waves and their transport and interactions in the surrounding interstellar medium.Aims. Here, we focus on the supernova remnant W28, which over the years has been observed in all energy domains from radio waves to very-high-energy gamma rays. The bright gamma-ray emission detected from molecular clouds located in its vicinity revealed the presence of accelerated GeV and TeV particles in the region. An enhanced ionization rate has also been measured by means of millimeter observations, but such observations alone cannot tell us whether the enhancement is due to low-energy (MeV) cosmic rays (either protons or electrons) or the X-ray photons emitted by the shocked gas. The goal of this study is to determine the origin of the enhanced ionization rate and to infer from multiwavelength observations the spectrum of cosmic rays accelerated at the supernova remnant shock in an unprecedented range spanning from MeV to multi-TeV particle energies.Methods. We developed a model to describe the transport of X-ray photons into the molecular cloud, and we fitted the radio, millimeter, and gamma-ray data to derive the spectrum of the radiating particles.Results. The contribution from X-ray photons to the enhanced ionization rate is negligible, and therefore the ionization must be due to cosmic rays. Even though we cannot exclude a contribution to the ionization rate coming from cosmic-ray electrons, we show that a scenario where cosmic-ray protons explain both the gamma-ray flux and the enhanced ionization rate provides the most natural fit to multiwavelength data. This strongly suggests that the intensity of CR protons is enhanced in the region for particle energies in a very broad range covering almost six orders of magnitude: from ≲100 MeV up to several tens of TeV. (10.1051/0004-6361/201936927)
DOI : 10.1051/0004-6361/201936927
Simulation of Plasmaspheric Plume Impact on Dayside Magnetic Reconnection
- Dargent J.
- Aunai N.
- Lavraud B.
- Toledo‐redondo S.
- Califano F.
Geophysical Research Letters, American Geophysical Union, 2020, 47 (4). • We perform Particle-In-Cell simulation of asymmetric magnetic reconnection including the impact of cold plasmaspheric plume • Inclusion of the plume reduces the reconnection rate, the reduction is explained by the additional mass in the system (mass-loading effect) • The temperature of the plume does not influence the reconnection rate (10.1029/2019GL086546)
DOI : 10.1029/2019GL086546
Étude et développement d'un oscillateur paramétrique optique picoseconde rapidement accordable utilisant des cristaux à quasi-accord de phase apériodique : application à la détection de gaz par imagerie active
- Walter Guillaume
, 2020. Nous rapportons l'étude d'un Oscillateur Paramétrique Optique (OPO) picoseconde à base de cristaux apériodiques à large bande, utilisé pour des applications en spectroscopie rapide. Cette source paramétrique permet de sonder des gaz possédant des raies d’absorptions dans le moyen infrarouge, sur une plage spectrale difficilement accessible avec un laser solide conventionnel. La spécificité de l’OPO étudié est, outre son régime temporel picoseconde, son cristal non linéaire à quasi-accord de phase apériodique. Cette apériodicité élargit intrinsèquement la bande de gain paramétrique. Les travaux entrepris dans cette thèse portent dans un premier temps sur la caractérisation et l’explication des comportements propres à ce type d’OPO non contraint par filtre spectral. Nous étudions plus particulièrement l’origine du profil spectral cannelé observé dès que la puissance seuil d’oscillation est dépassée : ce profil est composé d’un pic principal et d’une succession de pics latéraux et n’est pas reporté dans la littérature. La deuxième partie de l’étude consiste au contrôle de la longueur d’onde de l’OPO picoseconde en utilisant la condition de pompage synchrone intrinsèque à ce régime temporel, et un réseau de Bragg en volume chirpé (CVBG) : un déplacement du CVBG autour de la position respectant la condition de pompage synchrone, modifie la longueur d’onde oscillant dans la cavité. Cet OPO contraint permet l’étude d’émissions de gaz (N₂O, CO₂, etc.) dans l’atmosphère par imagerie active.
Polynomial Reconstruction of the Reconnection Magnetic Field Observed by Multiple Spacecraft
- Denton R.
- Torbert R. B
- Hasegawa H.
- Dors I.
- Genestreti K. J
- Argall M.
- Gershman D.
- Le Contel O.
- Burch J.
- Russell C. T.
- Strangeway R.
- Giles B.
- Fischer D.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2020, 125 (2). (10.1029/2019JA027481)
DOI : 10.1029/2019JA027481
Plasma-sheath transition in multi-fluid models with inertial terms under low pressure conditions: Comparison with the classical and kinetic theory
- Alvarez-Laguna Alejandro
- Magin Thierry E.
- Massot Marc
- Bourdon Anne
- Chabert Pascal
Plasma Sources Science and Technology, IOP Publishing, 2020. (10.1088/1361-6595/ab6242)
DOI : 10.1088/1361-6595/ab6242
Electromagnetic radiation from upper-hybrid wave turbulence in inhomogeneous solar plasmas
- Krafft C
- Volokitin A
Plasma Physics and Controlled Fusion, IOP Publishing, 2020, 62 (2), pp.024007. Type III solar radio bursts have been commonly observed in the solar wind and coronal plasmas. Electron beams accelerated in the Sun's atmosphere generate weakly magnetized Langmuir (upper-hybrid) wave turbulence producing in turn electromagnetic emissions at the electron plasma frequency ωp and its harmonic 2ωp, via successive processes involving interactions between the background plasma, the waves and the beam particles. The impact of the random density fluctuations inherent to the background plasma on these processes requires the development of novel approaches and models. Owing to a new theoretical modeling, the radiation efficiency of electromagnetic waves radiated at ωp from a plasma source with random density fluctuations and developed upper-hybrid wave turbulence is calculated analytically and numerically. It is shown that the maximum radiation efficiency at frequency ωp scales as the average level of density fluctuations and as the ratio (c/vT)–2 (where vT is the thermal velocity). These scaling laws are found owing to two different and novel methods of determination of the electromagnetic radiation by turbulent inhomogeneous plasma sources through waves' transformations on randomly fluctuating density irregularities. These results contribute significantly to the understanding of the processes involved in the generation of Type III solar radio bursts. Their presentation is preceded by a summary of previous studies on the dynamics of beam-driven Langmuir turbulence in inhomogeneous solar plasmas. (10.1088/1361-6587/ab569d)
DOI : 10.1088/1361-6587/ab569d

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