Publications

2016

• Kinetics of excited species at high specific energy deposition: quenching by electrons in the afterglow of a nanosecond capillary discharge
  
  • Lepikhin N D
  • Klochko A.V.
  • Popov N A
  • Starikovskaia Svetlana
  , 2016, pp.AIAA-2016-1213.
• Multi-point ignition of Hydrogen/Air mixtures with single pulsed nanosecond surface dielectric barrier discharge. Morphology of the discharge at elevated pressures
  
  • Shcherbanev S.A.
  • Popov N A
  • Starikovskaia Svetlana
  , 2016, pp.AIAA-2016-1692.
• Etude in-situ de la magnétopause Terrestre, de Cluster à MMS
  
  • Rezeau Laurence
  • Manuzzo Roberto
  • Belmont Gérard
  • Califano F.
  , 2016.
• Impact of the Eulerian chaos of magnetic field lines in magnetic reconnection
  
  • Firpo Marie-Christine
  • Ettoumi Wahb
  • Lifschitz A. F.
  • Retinò Alessandro
  • Farengo R F
  • Ferrari H E
  • García-Martínez P L
  Physics of Plasmas, American Institute of Physics, 2016, 23 (12). Stochasticity is an ingredient that may allow the breaking of the frozen-in law in the reconnec-tion process. It will first be argued that non-ideal effects may be considered as an implicit way to introduce stochasticity. Yet there also exists an explicit stochasticity that does not require the invocation of non-ideal effects. This comes from the spatial (or Eulerian) chaos of magnetic field lines that can show up only in a truly three-dimensional description of magnetic reconnection since two-dimensional models impose the integrability of the magnetic field lines. Some implications of this magnetic braiding, such as the increased particle finite-time Lyapunov exponents and increased acceleration of charged particles, are discussed in the frame of tokamak sawteeth that form a laboratory prototype of spontaneous magnetic reconnection. A justification for an increased reconnection rate with chaotic vs integrable magnetic field lines is proposed. Moreover, in 3D, the Eulerian chaos of magnetic field lines may coexist with the Eulerian chaos of velocity field lines, that is more commonly named turbulence. (10.1063/1.4972544)
  DOI : 10.1063/1.4972544
• Solar wind test of the de Broglie-Proca massive photon with Cluster multi-spacecraft data
  
  • Retinò Alessandro
  • Spallicci Alessandro D. A. M.
  • Vaivads Andris
  Astroparticle Physics, Elsevier, 2016, 82, pp.49–55. Our understanding of the universe at large and small scales relies largely on electromagnetic observations. As photons are the messengers, fundamental physics has a concern in testing their properties, including the absence of mass. We use Cluster four spacecraft data in the solar wind at 1 AU to estimate the mass upper limit for the photon. We look for deviations from Ampère’s law, through the curlometer technique for the computation of the magnetic field, and through the measurements of ion and electron velocities for the computation of the current. We show that the upper bound for mγ lies between 1.4×10−491.4×10−49 and 3.4×10−513.4×10−51 kg, and thereby discuss the currently accepted lower limits in the solar wind. (10.1016/j.astropartphys.2016.05.006)
  DOI : 10.1016/j.astropartphys.2016.05.006
• Distinct responses of the low-latitude ionosphere to CME and HSSWS: The role of the IMF B^z oscillation frequency
  
  • Rodríguez-Zuluaga J.
  • Radicella S. M.
  • Nava B.
  • Amory-Mazaudier Christine
  • Mora-Páez H.
  • Alazo-Cuartas K.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2016. In this work an attempt to identify the role of the interplanetary magnetic field (IMF) in the response of the ionosphere to different solar phenomena is presented. For this purpose, the day-today variability of the equatorial ionospheric anomaly (EIA) and the main ionospheric disturbances are analyzed during one coronal mass ejection (CME) and two high-speed solar wind streams (HSSWSs). The EIA parameters considered are the zonal electric field and both the strength and position of its northern crest. The disturbances being the prompt penetration of magnetospheric electric field (PPMEF) and disturbance dynamo electric field (DDEF) are studied using the magnetic response of their equivalent current systems. In accordance, ground-based Global Navigation Satellite Systems receivers and magnetometers at geomagnetic low latitudes in the American sector are used. During both phenomena, patterns of PPMEF related to fluctuations of the IMF are observed. Diurnal and semidiurnal magnetic oscillations are found to be likely related to DDEF. Comparisons among the EIA parameters and the DDEF magnetic response exhibit poor relation during the CME in contrast to good relation during the HSSWSs. It is concluded that the response of the low-latitude ionosphere to solar phenomena is largely determined through the oscillation frequency of the IMF B z by affecting the generation of the PPMEF and DDEF differently. This is seen as an effect of how the energy from the solar wind is transferred into the magnetosphere-ionosphere system. (10.1002/2016JA022539)
  DOI : 10.1002/2016JA022539
• Equatorial noise emissions with a quasi-periodic modulation observed by DEMETER at harmonics of the O⁺ ion gyrofrequency
  
  • Parrot Michel
  • Nĕmec František
  • Santolík Ondřej
  • Cornilleau-Wehrlin Nicole
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2016, 121 (10), pp.10,289–10,302. The analysis of ionospheric equatorial noise (EN) with a quasi-periodic (QP) modulation observed by the DEMETER spacecraft is presented. These EN emissions also called whistler mode or fast magnetosonic waves play an important role in acceleration of radiation belt electrons. A statistical analysis with 103 events shows that they occur just after intense magnetic storms. Usually, they are generated by unstable proton ring distribution close to the magnetic equator at harmonics of the proton gyrofrequency in the inner magnetosphere (2 < L < 8). But at lower L values down in the ionosphere three events have been analyzed and it appears that the EN waves are at harmonics of - or very close to - a O⁺ ion gyrofrequency which can be found close or slightly above the satellite. The wave propagation analysis indicates that these emissions are coming from an area above the satellite. Concerning one event, the EN emissions are observed on several consecutive orbits and there is a temporal coincidence with observations performed by the CLUSTER satellites at higher altitudes in the magnetosphere. EN emissions at lower frequencies have been also observed by the CLUSTER satellites in the same longitudinal sector as DEMETER but at ~5 R_E. The analysis of the STAFF data onboard C1 reveals that the magnetic field spectrogram has peaks close to harmonics of the local proton gyrofrequency as usually reported. It is shown that the DEMETER and CLUSTER EN waves have a similar QP modulation but with slightly different period and frequency. (10.1002/2016JA022989)
  DOI : 10.1002/2016JA022989
• Ion injection at Quasi-parallel Shocks Seen by the Cluster Spacecraft
  
  • Johlander A.
  • Vaivads A.
  • Khotyaintsev Y. V.
  • Retinò Alessandro
  • Dandouras I.
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2016, 817 (1), pp.L4. Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) and obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas. (10.3847/2041-8205/817/1/L4)
  DOI : 10.3847/2041-8205/817/1/L4
• Beyond the Maltese Cross: Geometry of Turbulence Between 0.2 and 1 au
  
  • Verdini Andrea
  • Grappin Roland
  The Astrophysical Journal, American Astronomical Society, 2016, 831. The spectral anisotropy of turbulent structures has been measured in the solar wind since 1990, relying on the assumption of axisymmetry about the mean magnetic field, B <SUB>0</SUB>. However, several works indicate that this hypothesis might be partially wrong, thus raising two questions: (i) is it correct to interpret measurements at 1 au (the so-called Maltese cross) in term of a sum of slab and two-dimensional (2D) turbulence; and (ii) what information is really contained in the Maltese cross? We solve direct numerical simulations of the magnetohydrodynamic equations including the transverse stretching exerted by the solar wind flow and study the genuine 3D anisotropy of turbulence as well as that one resulting from the assumption of axisymmetry about B <SUB>0</SUB>. We show that the evolution of the turbulent spectrum from 0.2 to 1 au depends strongly on its initial anisotropy. An axisymmetric spectrum with respect to B <SUB>0</SUB> keeps its axisymmetry, i.e., resists stretching perpendicular to radial, while an isotropic spectrum becomes essentially axisymmetric with respect to the radial direction. We conclude that close to the Sun, slow-wind turbulence has a spectrum that is axisymmetric around B <SUB>0</SUB> and the measured 2D component at 1 au describes the real shape of turbulent structures. In contrast, fast-wind turbulence has a more isotropic spectrum at the source and becomes radially symmetric at 1 au. Such structure is hidden by the symmetrization applied to the data that instead returns a slab geometry. (10.3847/0004-637X/831/2/179)
  DOI : 10.3847/0004-637X/831/2/179
• Emission spectroscopy of partial discharges in air-filled voids in Unfilled epoxy
  
  • Shcherbanev S.A.
  • Nadinov I.U.
  • Auvray Philippe
  • Starikovskaia Svetlana
  • Pancheshnyi Sergey V.
  • Herrmann L.G.
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2016, 44 (7), pp.1219-1227. Emission optical spectroscopy is used as a technique to study partial discharges (PDs) in four unfilled epoxy samples encompassing an artificial air-filled cavity. It is shown that emission spectroscopy can be used to estimate the density and the chemical composition of a gas from the spectrally resolved emission and time-resolved pulse shape of the PDs at any time during the aging process. Two scenarios are observed: either PD continues until the sample breaks down (observed in 1 out of 4 samples) or PD stops at a certain point without sample breakdown (3 out of 4 samples). For both the scenarios, a stable initial phase with a gradual decrease of emission intensity from the discharge is typical for a few hundreds of hours of continuous discharge operation. At this stage, the spectrum of the second positive system of molecular nitrogen dominates in the entire spectral range of 350500 nm studied in this work. Furthermore, time-resolved measurements indicate two types of discharges of very different frequencies and magnitudes as well as a decrease of the pressure in the voids as a function of aging time. Then, a sharp 500% increase of the N2 emission is observed 2 days before the breakdown; during the last day a spectrum of CO and some other C-N-O-H containing molecules is observed instead of the spectrum of molecular nitrogen. This allows predicting a breakdown at least a few hours before it happens by analyzing the broad emission spectra behavior. Additionally, the possible role of surface conductivity increase during aging on PD inhibition is discussed. (10.1109/TPS.2016.2576560)
  DOI : 10.1109/TPS.2016.2576560
• A computational analysis of the vibrational levels of molecular oxygen in low-pressure stationary and transient radio-frequency oxygen plasma
  
  • Kemaneci Efe
  • Booth Jean-Paul
  • Chabert Pascal
  • van Dijk Jan
  • Mussenbrock Thomas
  • Brinkmann Ralf Peter
  Plasma Sources Science and Technology, IOP Publishing, 2016, 25 (2), pp.025025. Vibrational levels of molecular oxygen, O 2 ( v &#8201;&#8201;<&#8201;&#8201;42), are investigated in continuous and pulse-modulated low-pressure radio-frequency oxygen plasma with a global modelling approach. The model is benchmarked against a variety of pressure-, power- and time-resolved measurements of several inductive and asymmetric capacitive discharges available in the literature, and a good agreement is obtained. The sensitivity of the model with respect to the vibrational kinetics, the wall reactions and the spatial inhomogeneity of the charged particles are presented. The simulations without the vibrational levels are also shown for the sake of comparison. (10.1088/0963-0252/25/2/025025)
  DOI : 10.1088/0963-0252/25/2/025025
• Influence of the angular scattering of electrons on the runaway threshold in air
  
  • Chanrion Olivier
  • Bonaventura Z.
  • Bourdon Anne
  • Neubert Torsten
  Plasma Physics and Controlled Fusion, IOP Publishing, 2016, 58, pp.044001. The runaway electron mechanism is of great importance for the understanding of the generation of x- and gamma rays in atmospheric discharges. In 1991, terrestrial gamma-ray flashes (TGFs) were discovered by the Compton Gamma-Ray Observatory. Those emissions are bremsstrahlung from high energy electrons that run away in electric fields associated with thunderstorms. In this paper, we discuss the runaway threshold definition with a particular interest in the influence of the angular scattering for electron energy close to the threshold. In order to understand the mechanism of runaway, we compare the outcome of different FokkerPlanck and Monte Carlo models with increasing complexity in the description of the scattering. The results show that the inclusion of the stochastic nature of collisions smooths the probability to run away around the threshold. Furthermore, we observe that a significant number of electrons diffuse out of the runaway regime when we take into account the diffusion in angle due to the scattering. Those results suggest using a runaway threshold energy based on the FokkerPlanck model assuming the angular equilibrium that is 1.6 to 1.8 times higher than the one proposed by [1, 2], depending on the magnitude of the ambient electric field. The threshold also is found to be 5 to 26 times higher than the one assuming forward scattering. We give a fitted formula for the threshold field valid over a large range of electric fields. Furthermore, we have shown that the assumption of forward scattering is not valid below 1 MeV where the runaway threshold usually is defined. These results are important for the thermal runaway and the runaway electron avalanche discharge mechanisms suggested to participate in the TGF generation. (10.1088/0741-3335/58/4/044001)
  DOI : 10.1088/0741-3335/58/4/044001
• Larger sized planar wire arrays of complex configuration on 1.51.8 MA Z-pinch generator
  
  • Safronova Alla S.
  • Kantsyrev Viktor L.
  • Weller Michael E.
  • Shlyaptseva V. V.
  • Shrestha I. K.
  • Stafford A.
  • Schmidt-Petersen M. T.
  • Lorance M. Y.
  • Schultz K. A.
  • Chuvatin Alexandre S.
  Physics of Plasmas, American Institute of Physics, 2016, 23, pp.101210. Two new approaches of (i) simultaneous study of implosion and radiative characteristics of different materials in wire array Z-pinch plasmas in one shot and (ii) investigation of larger sized wire arrays (to enhance energy coupling to plasmas and provide better diagnostic access) were developed in experiments with 1.51.8 MA Zebra with a Load Current Multiplier. In particular, the larger sized multi-plane Planar Wire Arrays with two outer planes placed at 9 and 15&#8201;mm from each other and then as far as at 19&#8201;mm (compared with 6&#8201;mm studied before at standard 1 MA current) and with a modified central plane with 8 to 12 empty slots were investigated. Though K-shell Al and L-shell Ni, Cu plasmas have similar electron temperatures and densities, the ablation dynamics and radiation of Al and Ni, Cu planes are somewhat different, which was investigated in detail using the full set of diagnostics and modeling. Advantages of using such wire arrays at higher currents to study plasma flow and radiation from different materials and jets are highlighted. (10.1063/1.4965239)
  DOI : 10.1063/1.4965239
• Double and Single Planar Wire Arrays on University-Scale Low-Impedance LTD Generator
  
  • Safronova Alla S.
  • Kantsyrev Viktor L.
  • Weller Michael E.
  • Shlyaptseva V. V.
  • Shrestha I. K.
  • Lorance M. Y.
  • Schmidt-Petersen M. T.
  • Stafford A.
  • Cooper M. C.
  • Steiner A. M.
  • Yager-Elorriaga D. A.
  • Patel S. G.
  • Jordan N. M.
  • Gilgenbach R. M.
  • Chuvatin Alexandre S.
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2016, 44 (4), pp.432-440. Planar wire array (PWA) experiments were performed on Michigan Accelerator for Inductive Z-pinch Experiments, the University of Michigan's low-impedance linear transformer driver (LTD)-driven generator (0.1 &#937;, 0.5-1 MA, and 100-200 ns), for the first time. It was demonstrated that Al wire arrays [both double PWA (DPWA) and single PWA (SPWA)] can be successfully imploded at LTD generator even at the relatively low current of 0.3-0.5 MA. In particular, implosion characteristics and radiative properties of PWAs of different load configurations [for DPWA from Al and stainless steel wires with different wire diameters, interwire gaps, and interplanar gaps (IPGs) and for Al SPWA of different array widths and number of wires] were studied. The major difference from the DPWA experiments on high-impedance Zebra accelerator was in the current rise time that was influenced by the load inductance and was increased up to about 150 ns during the first campaign (and was even longer in the second campaign). The implosion dynamics of DPWAs strongly depends on the critical load parameter, the aspect ratio (the ratio of the array width to IPG) as for Al DPWAs on high-impedance Zebra, but some differences were observed, for low-aspect ratio loads in particular. Analysis of X-ray images and spectroscopy indicates that K-shell Al plasmas from Al PWAs reached the electron temperatures up to more than 450 eV and densities up to 2 x 10²&#8304; cm&#8315;³. Despite the low mass of the loads, opacity effects were observed in the most prominent K-shell Al lines almost in every shot. (10.1109/TPS.2016.2538291)
  DOI : 10.1109/TPS.2016.2538291
• Electron scale structures and magnetic reconnection signatures in the turbulent magnetosheath
  
  • Yordanova E.
  • Vörös Z.
  • Varsani A.
  • Graham D. B.
  • Norgren C.
  • Khotyaintsev Y. V.
  • Vaivads A.
  • Eriksson E.
  • Nakamura R.
  • Lindqvist P.-A.
  • Marklund G.
  • Ergun R. E.
  • Magnes W.
  • Baumjohann W.
  • Fischer D.
  • Plaschke F.
  • Narita Y.
  • Russell C. T.
  • Strangeway R. J.
  • Le Contel Olivier
  • Pollock C.
  • Torbert R. B.
  • Giles B. J.
  • Burch J. L.
  • Avanov L. A.
  • Dorelli J. C.
  • Gershman D. J.
  • Paterson W. R.
  • Lavraud B.
  • Saito Y.
  Geophysical Research Letters, American Geophysical Union, 2016, 43 (12), pp.5969-5978. Collisionless space plasma turbulence can generate reconnecting thin current sheets as suggested by recent results of numerical magnetohydrodynamic simulations. The Magnetospheric Multiscale (MMS) mission provides the first serious opportunity to verify whether small ion-electron-scale reconnection, generated by turbulence, resembles the reconnection events frequently observed in the magnetotail or at the magnetopause. Here we investigate field and particle observations obtained by the MMS fleet in the turbulent terrestrial magnetosheath behind quasi-parallel bow shock geometry. We observe multiple small-scale current sheets during the event and present a detailed look of one of the detected structures. The emergence of thin current sheets can lead to electron scale structures. Within these structures, we see signatures of ion demagnetization, electron jets, electron heating, and agyrotropy suggesting that MMS spacecraft observe reconnection at these scales. (10.1002/2016GL069191)
  DOI : 10.1002/2016GL069191
• Cone angle control of the interaction of magnetic clouds with the Earth's bow shock
  
  • Turc Lucile
  • Escoubet C. Philippe
  • Fontaine Dominique
  • Kilpua E. K. J.
  • Enestam S.
  Geophysical Research Letters, American Geophysical Union, 2016, 43, pp.4781-4789. Not Available (10.1002/2016GL068818)
  DOI : 10.1002/2016GL068818
• Orientation of the X-line in asymmetric magnetic reconnection
  
  • Aunai Nicolas
  • Hesse Michael
  • Lavraud B.
  • Dargent Jérémy
  • Smets Roch
  Journal of Plasma Physics, Cambridge University Press (CUP), 2016, 82 (4), pp.535820401. Magnetic reconnection can occur in current sheets separating magnetic fields sheared by any angle and of arbitrarily different amplitudes. In such asymmetric and non-coplanar systems, it is not yet understood what the orientation of the X-line will be. Studying how this orientation is determined locally by the reconnection process is important to understand systems such as the Earth magnetopause, where reconnection occurs in regions with large differences in upstream plasma and field properties. This study aims at determining what the local X-line orientation is for different upstream magnetic shear angles in an asymmetric set-up relevant to the Earth's magnetopause. We use two-dimensional hybrid simulations and vary the simulation plane orientation with regard to the fixed magnetic field profile and search for the plane maximizing the reconnection rate. We find that the plane defined by the bisector of upstream fields maximizes the reconnection rate and this appears not to depend on the magnetic shear angle, domain size or upstream plasma and asymmetries. (10.1017/S0022377816000647)
  DOI : 10.1017/S0022377816000647
• Ionospheric and magnetic signatures of a high speed solar wind in low latitudes on 13 October 2012
  
  • Migoya-Orué Yenca
  • Azzouzi Ilyasse
  • Coisson Pierdavide
  • Amory-Mazaudier Christine
  • Fleury Rolland
  • Radicella Sandro M.
  Sun and Geosphere, BBC SWS Regional Network, 2016, 11 (1), pp.23-35. This paper presents the impact of a fast solar wind on the ionosphere, in low latitudes, on 13 October 2012. On that day, the high speed solar wind reached the Earth around 16:00UT, during the recovery phase of a geomagnetic storm which started around 00:00UT. The solar wind speed was determined to be 580km/s, on the same day, around 17:00UT. Its impact was observed in low and equatorial latitudes, in Africa and in Eastern South America, on the F layer and on the geomagnetic field variations. Through the analysis of magnetic indices, ionosonde characteristics and the horizontal component of the geomagnetic field, we found that the 13 October 2012 event exhibited a local impact, affecting the observatories situated in a longitude sector between 315°E and 45°E. Particularly, the F layer in Africa (observed by the ionosonde at Ascension Island) did not present any lift, and there was a delay for approximately two hours of the ascent of the F layer in America (the ionosonde at Fortaleza). In this case, there was an evident inhibition on the development of spread F at the time of the Pre Reversal Enhancement (PRE) in Africa and Eastern America, while the ionograms of the days before and after presented clear spread F traces. The disturbances of the ionospheric equivalent electric current (Diono) deduced from the variations of the geomagnetic field at M'Bour near Dakar (Africa) and at Kourou (Eastern America) exhibited on the dayside, an anti Sq current which is signature of the influence of the Disturbance Dynamo Electric Field (DDEF).
• Theory for the anomalous electron transport in Hall effect thrusters. I. Insights from particle-in-cell simulations
  
  • Lafleur Trevor
  • Baalrud S. D.
  • Chabert Pascal
  Physics of Plasmas, American Institute of Physics, 2016, 23 (5), pp.053502. Using a 1D particle-in-cell simulation with perpendicular electric, E0, and magnetic, B0, fields, and modelling the azimuthal direction (i.e., the E0&#8201;×&#8201;B0 direction), we study the cross-field electron transport in Hall effect thrusters (HETs). For low plasma densities, the electron transport is found to be well described by classical electron-neutral collision theory, but at sufficiently high densities (representative of typical HETs), a strong instability is observed to significantly enhance the electron mobility, even in the absence of electron-neutral collisions. This instability is associated with correlated high-frequency (of the order of MHz) and short-wavelength (of the order of mm) fluctuations in both the electric field and the plasma density, which are shown to be the cause of the anomalous transport. Saturation of the instability is observed to occur due to a combination of ion-wave trapping in the E0&#8201;×&#8201;B0 direction, and convection in the E0 direction. (10.1063/1.4948495)
  DOI : 10.1063/1.4948495
• Theory for the anomalous electron transport in Hall effect thrusters. II. Kinetic model
  
  • Lafleur Trevor
  • Baalrud S. D.
  • Chabert Pascal
  Physics of Plasmas, American Institute of Physics, 2016, 23 (5), pp.053503. In Paper I [T. Lafleur et al., Phys. Plasmas 23, 053502 (2016)], we demonstrated (using particle-in-cell simulations) the definite correlation between an anomalously high cross-field electron transport in Hall effect thrusters (HETs), and the presence of azimuthal electrostatic instabilities leading to enhanced electron scattering. Here, we present a kinetic theory that predicts the enhanced scattering rate and provides an electron cross-field mobility that is in good agreement with experiment. The large azimuthal electron drift velocity in HETs drives a strong instability that quickly saturates due to a combination of ion-wave trapping and wave-convection, leading to an enhanced mobility many orders of magnitude larger than that expected from classical diffusion theory. In addition to the magnetic field strength, B0, this enhanced mobility is a strong function of the plasma properties (such as the plasma density) and therefore does not, in general, follow simple 1/B20 or 1/B0 scaling laws. (10.1063/1.4948496)
  DOI : 10.1063/1.4948496
• Time-resolved electric field measurements during and after the initialization of a kHz plasma jetfrom streamers to guided streamers
  
  • Slikboer Elmar
  • Guaitella Olivier
  • Sobota Ana
  Plasma Sources Science and Technology, IOP Publishing, 2016, 25 (3), pp.03LT04. This work presents the investigation of a 30&#8201;kHz operated atmospheric pressure plasma jet impinging a dielectric BSO-crystal, allowing time-resolved electric field measurements based on the Pockels effect. Observations indicate that from the time the voltage is applied, the plasma first develops through unstable branching before a stable periodic behavior is established. This initialization of the plasma jet suggests the importance of the build-up of leftover ionization, which creates a preferred pathway for the streamer-like discharges. After initialization the time and spatially resolved electric field of guided ionization waves induced in the crystal is obtained, showing a highly periodic charging and discharging at the surface of the crystal. When the ionization wave arrives at the crystal charge is deposited and constant electric fields are generated for approximately 14 &#956;s. Then a (back) discharge will remove the deposited charge at the surface, related to the moment when the applied voltage changes polarity and it agrees with imaging reported on in other literature. (10.1088/0963-0252/25/3/03LT04)
  DOI : 10.1088/0963-0252/25/3/03LT04
• Dynamical Monte Carlo methods for plasma-surface reactions
  
  • Guerra V.
  • Marinov Daniil
  Plasma Sources Science and Technology, IOP Publishing, 2016, 25 (4), pp.045001. Different dynamical Monte Carlo algorithms to investigate molecule formation on surfaces are developed, evaluated and compared with the deterministic approach based on reaction-rate equations. These include a null event algorithm, the n-fold way/BKL algorithm and an 'hybrid' variant of the latter. NO2 formation by NO oxidation on Pyrex and O recombination on silica with the formation of O2 are taken as case studies. The influence of the grid size on the CPU calculation time and the accuracy of the results is analysed. The role of LangmuirHinsehlwood recombination involving two physisorbed atoms and the effect of back diffusion and its inclusion in a deterministic formulation are investigated and discussed. It is shown that dynamical Monte Carlo schemes are flexible, simple to implement, describe easily elementary processes that are not straightforward to include in deterministic simulations, can run very efficiently if appropriately chosen and give highly reliable results. Moreover, the present approach provides a relatively simple procedure to describe fully coupled surface and gas phase chemistries. (10.1088/0963-0252/25/4/045001)
  DOI : 10.1088/0963-0252/25/4/045001
• Cluster observations of reflected EMIC-triggered emission
  
  • Grison B.
  • Darrouzet F.
  • Santolík O.
  • Cornilleau-Wehrlin Nicole
  • Masson A.
  Geophysical Research Letters, American Geophysical Union, 2016, 43, pp.4164-4171. On 19 March 2001, the Cluster fleet recorded an electromagnetic rising tone on the nightside of the plasmasphere. The emission was found to propagate toward the Earth and toward the magnetic equator at a group velocity of about 200 km/s. The Poynting vector is mainly oblique to the background magnetic field and directed toward the Earth. The propagation angle thetak,B<SUB>0</SUB> becomes more oblique with increasing magnetic latitude. Inside each rising tone thetak,B<SUB>0</SUB> is more field aligned for higher frequencies. Comparing our results to previous ray tracing analysis we conclude that this emission is a triggered electromagnetic ion cyclotron (EMIC) wave generated at the nightside plasmapause. We detect the wave just after its reflection in the plasmasphere. The reflection makes the tone slope shallower. This process can contribute to the formation of pearl pulsations. (10.1002/2016GL069096)
  DOI : 10.1002/2016GL069096
• Signatures of complex magnetic topologies from multiple reconnection sites induced by Kelvin-Helmholtz instability
  
  • Vernisse Y.
  • Lavraud B.
  • Eriksson S.
  • Gershman D. J.
  • Dorelli J. C.
  • Pollock C.
  • Giles B. L.
  • Aunai Nicolas
  • Avanov L.
  • Burch J. L.
  • Chandler Michael O.
  • Coffey Victoria
  • Dargent Jérémy
  • Ergun R. E.
  • Farrugia C. J.
  • Génot V.
  • Graham D. B.
  • Hasegawa H.
  • Jacquey C.
  • Kacem I.
  • Khotyaintsev Y. V.
  • Li W.
  • Magnes W.
  • Marchaudon A.
  • Moore T. E.
  • Paterson W. R.
  • Penou E.
  • Phan T. D.
  • Retinò Alessandro
  • Russell C. T.
  • Saito Y.
  • Sauvaud J.-A.
  • Torbert R.
  • Wilder F. D.
  • Yokota S.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2016, 121 (10), pp.9926-9939. The Magnetospheric Multiscale mission has demonstrated the frequent presence of reconnection exhausts at thin current sheets within Kelvin-Helmholtz (KH) waves at the flank magnetopause. Motivated by these recent observations, we performed a statistical analysis of the boundary layers on the magnetosheath side of all KH current sheets on 8 September 2015. We show 86% consistency between the exhaust flows and particle leakage in the magnetosheath boundary layers but further highlight the very frequent presence of additional boundary layer signatures that do not come from the locally observed reconnection exhausts. These additional electron and ion boundary layers, of various durations and at various positions with respect to the leading and trailing boundaries of the KH waves, signal connections to reconnection sites at other locations. Based on the directionality and extent of these layers, we provide an interpretation whereby complex magnetic topologies can arise within KH waves from the combination of reconnection in the equatorial plane and at midlatitudes in the Southern and Northern Hemispheres, where additional reconnection sites are expected to be triggered by the three-dimensional field lines interweaving induced by the KH waves at the flanks (owing to differential flow and magnetic field shear with latitude). The present event demonstrates that the three-dimensional development of KH waves can induce plasma entry (through reconnection at both midlatitude and equatorial regions) already sunward of the terminator where the instability remains in its linear stage. (10.1002/2016JA023051)
  DOI : 10.1002/2016JA023051
• Combined use of LIDAR and hyperspectral measurements for remote sensing of fluorescence and vertical profile of canopies
  
  • Ounis A.
  • Bach J.
  • Mahjoub A.
  • Daumard Fabrice
  • Moya I
  • Goulas Y.
  Revista de Teledetección, 2016 (45), pp.87-94. We report the development of a new LIDAR system (LASVEG) for airborne remote sensing of chlorophyll fluorescence (ChlF) and vertical profile of canopies. By combining laser-induced fluorescence (LIF), sun-induced fluorescence (SIF) and canopy height distribution, the new instrument will allow the simultaneous assessment of gross primary production (GPP), photosynthesis efficiency and above ground carbon stocks. Technical issues of the fluorescence LIDAR development are discussed and expected performances are presented. (10.4995/raet.2015.3982)
  DOI : 10.4995/raet.2015.3982