Publications

2019

• 72th Gaseous Electronic Conference (GEC)
  
  • Guaitella Olivier
  , 2019.
• Hall thrusters instabilities analysis with 2D (axial-azimuthal) Particle-In-Cell simulations
  
  • Charoy Thomas
  • Lafleur Trevor
  • Tavant Antoine
  • Chabert Pascal
  • Bourdon Anne
  , 2019.
• A Survey of Plasma Waves Appearing Near Dayside Magnetopause Electron Diffusion Region Events
  
  • Wilder F.
  • Ergun R.
  • Hoilijoki S.
  • Webster J.
  • Argall M.
  • Ahmadi N.
  • Eriksson S.
  • Burch J.
  • Torbert R.
  • Le Contel O.
  • Strangeway R.
  • Giles B.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2019, 124 (10), pp.7837-7849. (10.1029/2019JA027060)
  DOI : 10.1029/2019JA027060
• Current challenges in the modeling and validation of PIC and fluid simu- lations for low-temperature plasmas
  
  • Bourdon Anne
  , 2019.
• Fitting a high total impulse electric propulsion system in a student CubeSat to compensate the atmosphericdrag in low-earth orbit
  
  • Marmuse Florian
  • Darcet Timothée
  • Francois Victor
  • Delgado Julie
  • Esmieu-Fourmel Maixent
  • Gourcerol Etienne
  • Magnan Nathan
  • Bellier Thomas
  • Langlois Lucas
  • Decorde Baptiste
  • Thirion Samuel
  • Ponchon Paul
  • Schweizer Jonas
  • Oriol Benoit
  • Gaynullin Dimitri
  • Schnitzler Bastien
  • Solovyeva Lilia
  , 2019. In this era where the interest in nanosatellites is growing rapidly, the next big step for them is to integrate a propulsion subsystem in order to accomplish more complex missions. With electric propulsion in particular, nanosatellites will be able to perform new maneuvers and new missions, such as missions in LEO by compensating the drag with a thruster. However, designing such a mission and the satellite for it is not easily feasible for a student project. Here we present a preliminary design for a 6U CubeSat capable of maintaining an altitude of about 300 km for more than several months. This project is a fully student project, and it is supported by the CNES and École polytechnique in Paris. It is planned to be ready for launch in the early 2020s. The phase B planning of this project allowed us to design a nanosat capable of withstanding the high demand for power and capable of performing all maneuvers necessary to reach the target altitude and maintain it. All the technical choices allowing these performances are explained: high-capacity batteries capable of providing energy for one whole thrust sequence (50Wh), large, deployable but not steerable solar panels to recharge them and a balanced ADCS strategy allowing both a high energy intake and regular thrust phases to keep a stable altitude. It is shown that a three-axis reaction wheels stabilization is necessary for such a mission, even while rotating the satellite only around a fixed thrust axis. Finally, the trajectography algorithm, for now based on periapsis raising based on GPS data, under constraints of battery charge and eccentricity, is described, as well as the structure of the on-board computer and the technical choices around them. This preliminary design shows how a satellite can handle atmospheric drag at around 300 km for several months with the constraints of a student-designed CubeSat.
• A plausible model of inflation driven by strong gravitational wave turbulence
  
  • Galtier Sébastien
  • Laurie Jason
  • Nazarenko Sergey V.
  , 2019. It is widely accepted that the primordial universe experienced a brief period of accelerated expansion called inflation. This scenario provides a plausible solution to the horizon and flatness problems. However, the particle physics mechanism responsible for inflation remains speculative with, in particular , the assumption of a scalar field called inflaton. Furthermore, the comparison with the most recent data raises new questions that encourage the consideration of alternative hypotheses. Here, we propose a completely different scenario based on a mechanism whose origins lie in the nonlin-earities of the Einstein field equations. We use the analytical results of weak gravitational wave turbulence to develop a phenomenological theory of strong gravitational wave turbulence where the inverse cascade of wave action plays a key role. In this scenario, the space-time metric excitation triggers an explosive inverse cascade followed by the formation of a condensate in Fourier space whose growth is interpreted as an expansion of the universe. Contrary to the idea that gravitation can only produce a decelerating expansion, our study reveals that gravitational wave turbulence could be a source of inflation. The fossil spectrum that emerges from this scenario is shown to be in agreement with the cosmic microwave background radiation measured by the Planck mission.
• Multi-point observations of whistler mode waves in the outer radiation belt region
  
  • Santolík Ondřej
  • Pickett J S
  • Yearby K H
  • Canu Patrick
  • Cornilleau-Wehrlin Nicole
  • Carr C M
  , 2019. Natural emissions of whistler-mode electromagnetic waves, especially chorus and hiss, can influence the dynamics of the Van Allen radiation belts via quasi-linear or nonlinear wave particle interactions. They can play a role in complex processes of the energy transfer between different electron populations. To separate temporal and spatial variations of their characteristics, measurements at different points in space are necessary. We show initial results of measurements of the Cluster space fleet during the period of close separations between Cluster 3 and Cluster 4 from September to December 2018. As the separations of these spacecraft decrease down to 3 km in the equatorial source region of chorus we can perform systematic phase measurements of nonlinear wave packets of chorus. The embedded fine structure of sub-packets is particularly interesting in this context because their spatio-temporal scales have been shown to be much shorter compared to scales of the chorus wave packets. We use detailed waveform measurements of the WBD instruments onboard Cluster 3 and Cluster 4 close to the equator, with Cluster 1 and/or Cluster 2 located at much larger separations at higher latitudes. These detailed measurements are put in the context of overall wave propagation and polarization patterns by multi-component data of the STAFF-SA instruments onboard all the 4 Cluster spacecraft, with the FGM instruments used to define the magnetic field-aligned coordinate system and to normalize the measured frequencies by the electron cyclotron frequency.
• Latitudinal extension of the sources of continuum radiations
  
  • Canu Patrick
  • Fazakerley A N
  • Vallières Xavier
  • Rauch Jean-Louis L
  • Décréau Pierrette
  • Fontaine Dominique
  • Carr C
  • Piberne Rodrigue
  , 2019. The electromagnetic radio emissions known as 'continuum radiation' are widely observed for decades in planetary magnetospheres. Although their main source location is well identified for Earth in the vicinity of the equatorial plasmapause and its generation mechanism generally associated with electrostatic emissions arising between half harmonics of the electron gyro harmonics, many details of their characteristics and source are still missing. Recent observations had suggested new features in their description. For example, studies based on the Whisper instruments have shown that continuum sources can also be located at mid latitudes and can be generated at exact harmonics of the electron frequency. The higher perigee of the present phase of the Cluster extended mission allows the spacecraft to skim the sources regions close to the plasmapause and to explore their latitudinal extension thanks to its polar orbit. This higher perigee also allows to get Peace data, seldom available at the lower perigees earlier in the mission, to characterize the electrons populations at the origin of these emissions. We present here the first analysis of the best events observed so far.
• Large and micro-scale MMS/Cluster joint measurements of plasma sheet boundary layer crossings: a case study
  
  • Le Contel Olivier
  • Retinò A.
  • Alexandrova Alexandra
  • Chust T.
  • Steinvall K
  • Canu Patrick
  • Fontaine D.
  • Dandouras I.
  • Carr C. M
  • Toledo S
  • Kiehas S
  • Nakamura R
  • Khotyaintsev Yu
  • Wilder F D
  • Ahmadi N
  • Gershman D J
  • Strangeway R J
  • Plaschke F
  • Argall M R
  • Turner D L
  • Cohen I J
  • Burch J L
  • Torbert R B
  • Fuselier S A
  • Giles B J
  • Ergun R E
  • Lindqvist P.-A
  • Escoubet P
  , 2019.
• Cold-atmospheric plasma improves burn injury repair via modulation of angiogenesis, extracellular matrix formation and antibacterial effect
  
  • Duchesne Constance
  , 2019. Thermal injuries affect millions of adults and children worldwide. In the last 30 years little progress has been made in the management of major burns and despite improved rates of survival, patients continue to suffer debilitating consequences such as infections, hypertrophic scars, contractures, post-traumatic stress disorder and immunometabolic dysfunctions.Cold-atmospheric plasmas (CAP) are partially ionized gases which showed ability to promote wound closure and possess bactericidal properties. They safely deliver to the wounds a therapeutic mixture of reactive oxygen and nitrogen species at body temperature.This PhD study aimed to assess the therapeutic potential of CAP to improve healing of burn wounds under aseptic and septic conditions.First, we designed a plasma source that could be used for in vitro and in vivo studies. Although the first in vitro experiments showed that CAP treatment can improve cellular migration, we couldn’t see any beneficial of CAP on the healing of full-thickness excisional wounds in mice. Second, using a model of third degree burn reconstructed with an allogeneic graft, we assessed both effectiveness and mechanism of action of CAP compared to a placebo control (helium). Indeed, it was shown that through the promotion of pro-angiogenic activities as well as stimulation of the extracellular matrix formation, CAP improved engraftment and healing of the burn wounds. These effects are at least partly mediated by the TGF-β signaling pathway and eNOS modulation. Third, the bactericidal activity of CAP was evaluated in vitro using S. aureus strains and macrophages and in vivo using an infected burn wound model. We showed that CAP had the ability to significantly inactivate S. aureus compared to the helium control. Capacities of CAP treatment to activate macrophages were also evident.This proof-of-concept study demonstrated the therapeutic potential of CAP on tissue repair and burn wound healing. Given that mouse skin does not perfectly mimic wound healing patterns observed in human skin, further investigations are warranted using large animal models with greater similarity to human skin.
• Spiral chain models of two-dimensional turbulence
  
  • Gürcan Özgür D.
  • Xu Shaokang
  • Morel Pierre
  Physical Review E, American Physical Society (APS), 2019, 100 (4). (10.1103/PhysRevE.100.043113)
  DOI : 10.1103/PhysRevE.100.043113
• 2D axial-azimuthal particle-in-cell benchmark for low-temperature partially magnetized plasmas
  
  • Charoy Thomas
  • Boeuf Jean-Pierre
  • Bourdon A.
  • Carlsson J.
  • Chabert Pascal
  • Cuenot B.
  • Eremin D
  • Garrigues Laurent
  • Hara K
  • Kaganovich I D
  • Powis A. T.
  • Smolyakov A
  • Sydorenko D
  • Tavant Antoine
  • Vermorel O.
  • Villafana W
  Plasma Sources Science and Technology, IOP Publishing, 2019, 28 (10), pp.105010. The increasing need to demonstrate the correctness of computer simulations has highlighted the importance of benchmarks. We define in this paper a representative simulation case to study low-temperature partially-magnetized plasmas. Seven independently developed Particle-In-Cell codes have simulated this benchmark case, with the same specified conditions. The characteristics of the codes used, such as implementation details or computing times and resources, are given. First, we compare at steady-state the time-averaged axial profiles of three main discharge parameters (axial electric field, ion density and electron temperature). We show that the results obtained exhibit a very good agreement within 5% between all the codes. As ExB discharges are known to cause instabilities propagating in the direction of electron drift, an analysis of these instabilities is then performed and a similar behaviour is retrieved between all the codes. A particular attention has been paid to the numerical convergence by varying the number of macroparticles per cell and we show that the chosen benchmark case displays a good convergence. Detailed outputs are given in the supplementary data, to be used by other similar codes in the perspective of code verification. 2D axial-azimuthal Particle-In-Cell benchmark for low-temperature partially .. (10.1088/1361-6595/ab46c5)
  DOI : 10.1088/1361-6595/ab46c5
• Microphysics of magnetic reconnection in near-Earth space : spacecraft observations and numerical simulations
  
  • Cozzani Giulia
  , 2019. Magnetic reconnection is a fundamental energy conversion process occurring in space and laboratory plasmas. Reconnection takes place in thin current sheets leading to thereconfiguration of magnetic field topology and to conversion of magnetic energy into acceleration and heating of particles. Today reconnection is recognized to play a key role in the Earth-solar environment, from the solar corona to the solar wind, to magnetosheath, at the Earth's magnetopause, and in the magnetotail. Reconnection is initiated in the Electron Diffusion Region (EDR), where electrons decouple from the magnetic field and are energized by electric fields. Despite the very significant advances that have been made in the understanding of the magnetic reconnection process by means of in-situ measurements (notably provided by the Cluster mission) and by numerical simulations, the small electron scale physics of the dissipation region remains basically unsolved.It is only in the last years, with the launch of the Magnetospheric MultiScale mission (MMS) together with the recent impressive increasing of computational capabilities of supercomputers, that the dynamics of the Electron Diffusion Region has started to be enlightened. One of the key, yet still open questions, is whether the EDR has a preferred homogeneous or inhomogeneous structure at electron scales and below. The purpose of this Thesis is to advance in the understanding of the structure of the Electron Diffusion Region using two different approaches, notably MMS spacecraft observations and kinetic full Vlasov simulations. The first part presents MMS observations of an EDR encounter at the subsolar magnetopause when the four MMS probes were located at the smallest interspacecraft separationof ∼ 6 km, which is comparable to a few electron inertial length (d_e ∼ 2 km).We find that the EDR is rather inhomogeneous at electron scales in terms of current density and electric field which appear to be different at different spacecraft. In addition, the pattern of the energy conversion is patchy, showing that the structure of the EDR at the magnetopause can be much more complex than it has been found in other MMS events and than it is usually depicted by kinetic PIC simulations.Our MMS data analysis has pointed out the need of simulations with better spatial resolution and low noise on the electron scales, in particular on the electric field, in order to better understand the kinetic physics at play at electron scales. Following this motivation, the second part of the Thesis aims at studying the EDR by using a novel fully-kinetic Eulerian Vlasov-Darwin model which we have implemented in the numerical ViDA code.The ViDA code is specifically designed to improve our understanding of the kinetic dynamics of collisionless plasma at electron scales by giving access to the fine phase space details of the electron distribution function. A first part is devoted to the testing of the code by performing 2D symmetric magnetic reconnection simulations. Then, low-noise simulation data have been used to investigate the contribution of the different terms in the Ohm's law in the EDR, focusing on the contribution of the electron inertia term which is responsible for the decoupling of the electron dynamics from the magnetic field.
• Theory and simulation of low-pressure plasma transport phenomena : Application to the PEGASES Thruster
  
  • Lucken Romain
  , 2019. The field of low temperature plasma physics has emerged from the first fundamental discoveries in atom and plasma physics more than a century ago. However, it has soon become very much driven by applications. One of the most important of them in the first half of the XXth century is the "Calutron" (California University Cyclotron) invented by E.~Lawrence in Berkeley, that was part of the Manhattan project, and operated as a mass spectrometer to separate uranium isotopes. In a 1949 report of the Manhattan project, D.~Bohm makes two observations that are fundamental for low-temperature plasma physics.(i) The ions must have minimum kinetic energy when they enter the plasma sheath estimated to T_e/2 , Te being the electron temperature in eV ;(ii) Plasma transport across a magnetic field is enhanced by instabilities.Plasma electric propulsion is used on military satellites and space probes since the 1960s and has gained more and more interest for the last twenty years as space commercial applications were developing. However, the same questions as the ones D.~Bohm was faced with, namely multi-dimensional transport, plasma sheath interaction, and instabilities, arise. Theory and simulation are even more important for electric space propulsion systems design since testing in real conditions involves to launch a satellite into space.In this work, we derive the equations of the multi-dimensional isothermal plasma transport, we establish a sheath criterion that causes the magnetic confinement to saturate in low-temperature, weakly ionized plasmas, and we model the electron cooling through the magnetic filter of the PEGASES (Plasma Propulsion with Electronegative Gases) thruster. All the theories are driven and validated with extensive two-dimensional particle-in-cell (PIC) simulations, using the LPPic code that was partially developed in the frame of this project. Finally, the simulation cases are extended to an iodine inductively coupled plasma (ICP) discharge with a new set of reaction cross sections.
• Numerical modeling of magnetic reconnection in laser-induced high energy density plasmas
  
  • Sladkov Andrey
  , 2019. This thesis is a numerical study of the magnetic reconnection in collisionless plasmas using a kinetic code. We can study the magnetic reconnection process during experiments for which the plasma is created by interaction of a power laser on a solid target. During this thesis, we included in the HECKLE code the elements allowing to make these simulations more realistic for the laser conditions: the effects of the electron six-component pressure tensor as well as the super-Alfvénic expansion of the plasma. We have thus highlighted the role of the pressure tensor to reduce the efficiency of the reconnection, as well as the plasma temperature effects making it more impulsive.
• Electric field evolution in a diffuse ionization wave nanosecond pulse discharge in atmospheric pressure air
  
  • Chng Tat Loon
  • Brisset Alexandra
  • Jeanney Pascal
  • Starikovskaia Svetlana
  • Adamovich Igor
  • Tardiveau Pierre
  Plasma Sources Science and Technology, IOP Publishing, 2019, 28 (9), pp.09LT02. The time-resolved electric field in a fast ionization wave discharge in a diffuse nanosecond pulse discharge plasma in atmospheric pressure air is measured using the Electric Field Induced Second Harmonic (E-FISH) diagnostic. The electric field is placed on an absolute scale by calibration against a Laplacian field. At relatively low peak voltages, when the plasma is generated only near the pin high-voltage electrode, the electric field is measured ahead of the ionization wave during the entire voltage pulse, exhibiting a strong field enhancement compared to the Laplacian field, by about an order of magnitude. As the peak voltage is increased and the ionization wave traverses the laser beam, the electric field is measured both ahead of the wave and behind the ionization front, where the field drops rapidly due to the charge separation and plasma selfshielding. When the wave reaches the grounded electrode, the discharge transitions into a conduction phase in which the potential is redistributed within the gap. The electric field in the vicinity of the pin then increases again, following the applied voltage waveform for the rest of the pulse. The effective time resolution of the present measurements is 150 ps. Based on the single shot data, we find that the peak electric field in the wave front is moderately influenced by the applied voltage and varies between 160 to 210 kV/cm. This study demonstrates the viability of the E-FISH diagnostic for this class of atmospheric pressure discharges and paves the way for future in-depth studies of this particular problem. (10.1088/1361-6595/ab3cfc)
  DOI : 10.1088/1361-6595/ab3cfc
• Non-thermal atmospheric pressure plasma interacting with water for biological applications
  
  • Liu Bo
  , 2019. Non-Thermal-Plasmas (NTP) produced by electric discharges are weakly ionized gases, which keeps the gas temperature at near room temperature contrary to the electron temperature which can reach several electron-Volts. Applications of NTP to medicine and agriculture are new multidisciplinary research fields based on interactions of the Non-Thermal-Plasmas with living organisms. Electric field as well as Reactive Oxygen and Nitrogen Species produced by NTP may inactivate bacteria, stimulate skin regeneration (dermatology), tumor reduction (oncology) and seeds germination (agriculture). These new fields of research are based on the plasma-liquid chemistry. The objective of this work is to study the NTP interacting with water for biological applications including on one hand, the promotion of the germination of seeds using a Dielectric Barrier Discharge (DBD) and on the other hand, the effect of a plasma jet treatment ex vivo on skinThis manuscript is divided in five chapters: i) First a literature review is presented showing the state of the art of the plasma-liquid interaction, and the main advances of the application of non thermal plasmas to seed germination. Ii) Second, experimental set ups are described, in particular the manufacturing of plasma reactors using 3D printing. Iii) then , the production of gaseous and aqueous reactive species formed by DBD plasmas was measured quantitatively and plasma-liquid interaction was analyzed. Iv) Next, different varieties of seeds were selected to evaluate the effect of a DBD plasma treatment and the study of the mechanisms of plasma germination promotion was specifically investigated by treating mung bean seeds in different discharge conditions, in different mediums, in electric field alone and in different hydration levels of seeds.v) Finally, Muller parametric imaging (MPI) was applied to study the modification of ex vivo mice skin treated by a helium jet plasma.
• Laboratory simulation of plasma-aerosols interaction in Titan's ionosphere
  
  • Chatain Audrey
  • Carrasco Nathalie
  • Vettier Ludovic
  • Gautier Thomas
  • Guaitella Olivier
  , 2019, 13, pp.EPSC-DPS2019-1317-1. Organic aerosols formed in Titan's upper atmosphere are surrounded by very reactive plasma species. The present work aims to study the potential interactions between aerosols and plasma species. The exposure of aerosols to plasma is simulated in a cold plasma reactor. IR transmission spectroscopy gives clues about the chemical modifications of the aerosols. Mass spectrometry simultaneously measures the neutral species and positive ions in the gas phase. We observe the formation of HCN and carbocations while ammonia density is decreased by the addition of organic aerosols in the N2-H2 plasma.
• MESSENGER observations of planetary ion characteristics within Kelvin-Helmholtz vortices
  
  • Aizawa Sae
  • Raines Jim
  • Terada Naoki
  • Delcourt Dominique
  • Andre Nicolas
  , 2019, 2019. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft regularly observed the magnetospheric flanks of Mercury during its orbital phase, 2011-2015. Data from the magnetometer (MAG) and Fast Imaging Plasma Spectrometer (FIPS) allow us to investigate the statistical properties of planetary ions in the presence of Kelvin-Helmholtz (KH) vortices near the duskside magnetopause. We collect data from orbits with clear signatures of KH waves, as well as consecutive orbits that do not have KH signatures, and we compare energy characteristics between KH and non-KH events. Although low planetary counts in FIPS data make the comparison of these characteristics difficult, we find that : (1) large counts of planetary ions are observed in the presence of KH waves, (2) differences in Na+ energy spectra are only seen inside the magnetosphere, where they show a decelerating signature for KH events for ions with energies above 2.0 keV/e. These results suggest that planetary ions can stagnate within KH vortices and that electric field structures related to KH waves can decelerate planetary ions originating from the magnetotail region. In this study, I analyzed the whole data by myself and compared with my previous numerical studies.
• Oscillation analysis in Hall thrusters with 2D (axial-azimuthal) Particle-In-Cell simulations
  
  • Charoy Thomas
  • Bourdon A.
  • Chabert Pascal
  • Lafleur Trevor
  • Tavant Antoine
  , 2019.
• Global model of a magnetized ion thruster with xenon and iodine
  
  • Lucken Romain
  • Marmuse Florian
  • Tavant Antoine
  • Bourdon Anne
  • Chabert Pascal
  , 2019 (IEPC-2019-678). Gridded ion thrusters are proven technologies for spacecraft propulsion in the Earth environment and beyond for commercial, scientific and exploratory missions. Experimental works and theoretical investigations have shown that the efficiency of these thrusters canbe improved by magnetic confinement. However, it is known that instabilities develop in magnetized plasmas that deconfine the electrons and decrease the efficiency with respect to what the classical theory of stable plasma transport predicts. Using recent theories of instability enhanced plasma transport, and based on former works performed on the global modeling of plasma discharges in the non-magnetized case, we develop a global model of a gridded ion thruster where the plasma is sustained by a radio-frequency antenna, and confined by a magnetic field oriented along the thrust axis. The unstable xenon plasma is simulated using 2D PIC simulation in simplified geometry. Iodine and xenon thrusters are both simulated using the global model, with a magnetic field varying between 0 and 20 mT. The plasma properties predicted by the classical and the instability enhanced transport models are given. The performances of the thrusters are also compared.
• Optical and electrical diagnostics in an iodine plasma
  
  • Marmuse Florian
  • Lucken Romain
  • Drag Cyril
  • Booth Jean-Paul
  • Bourdon Anne
  • Chabert Pascal
  • Aanesland Ane
  , 2019. Iodine is being studied as the next generation propellant for electric propulsion: dense, stored as a solid, it is also much cheaper than xenon for similar mass and ionization potential. Iodine plasmas are more complex and less studied than noble gases plasmas, leaving electric propulsion engineers with few models and diagnostics in their toolkits. Here we present three experimental diagnostics deployed on a low pressure Radio-Frequency inducted Inductively Coupled iodine plasma discharge. Two optical diagnostics are used to probe the I atom and the I2 molecule: classical absorption at 1.3 µm gives the line-of-sight integrated temperature and density of I; low-resolution broadband absorption spectroscopy between 480 and 500 nm gives the line-of-sight integrated density of I2. A Langmuir probe is used to determine the electron temperature and the negative species density at the centre of the plasma, provided that the data are treated by taking in consideration the electronegativity of the plasma. Comparisons with a global model derived from Grondein et al., 2016 tends to suggest that the recombination coefficient at the walls is underestimated for our setup.
• Electron temperature(s) in Titan's ionosphere: re-analysis of the Cassini RPWS/LP data
  
  • Chatain Audrey
  • Wahlund Jan-Erik
  • Morooka Michiko
  • Shebanits Oleg
  • Hadid Lina
  • Eriksson Anders I.
  • Carrasco Nathalie
  , 2019, 13, pp.EPSC-DPS2019-1382-1. The Cassini Langmuir Probe (LP) data, part of the Radio and Plasma Wave Science (RPWS) investigation, in Titan's ionosphere are re-analyzed with the main goal to finely measure the electron temperature on all the dataset. The LP sweeps in this region are particularly difficult to fit and interpret. We have found that several maxwellian electron components were needed to correctly fit the data. It seems that at least two electron populations of different temperatures are present. Statistical studies show that the main component gives an electron temperature slowly varying with Solar Zenith Angle. However, a second electron population often appears at lower altitudes and has a temperature more dependent on solar irradiation.
• Analogues of Titan's aerosols: the different steps of formation in a N₂-CH₄ plasma
  
  • Perrin Zoé
  • Chatain Audrey
  • Ruscassier Nathalie
  • Vettier Ludovic
  , 2019, 13, pp.EPSC-DPS2019-2035. Observations by the Cassini mission show the presence of aerosols in Titan's atmosphere. According to models, these aerosols should reside there during several years. A plasma reactor is used to simulate the production of aerosols in the upper atmosphere of Titan. Five productions of aerosols were carried out with different residence times in the plasma, corresponding to different stages of evolution. These analogues were then analyzed by electron microscopy and infrared spectroscopy. Our results show that aerosols undergo morphological evolution in time. They grow and start forming aggregates at a certain stage. In addition, we also observed evolutions of the chemical functions present in the aerosols of different formation times.
• 2D (axial-azimuthal) Particle-In-Cell Benchmark for ExB Discharges
  
  • Charoy Thomas
  • Boeuf Jean-Pierre
  • Bourdon Anne
  • Carlsson J.A.
  • Chabert Pascal
  • Cuenot Bénédicte
  • Eremin Denis
  • Garrigues Laurent
  • Hara Kentaro
  • Kaganovich I.
  • Powis Andrew Tasman
  • Smolyakov Andrei
  • Sydorenko D
  • Tavant Antoine
  • Vermorel Olivier
  • Villafana Willca
  , 2019.