Publications

2014

• Plasma Beta Dependence of Magnetic Compressibility in Solar Wind Turbulence
  
  • Chapman S. C.
  • Hnat B.
  • Kiyani K. H.
  • Sahraoui Fouad
  , 2014, 33, pp.SH33A-4141. The turbulent signature of MHD scales in the near-Earth solar wind are known to be primarily incompressible which manifests itself in magnetic field fluctuation vector components to be aligned primarily perpendicular to the background magnetic field − so-called "Variance Anisotropy". This, and other facts, have been seen as evidence for a majority Alfvenic turbulence cascade; with a small component (10%) of compressible fluctuations. When one approaches scales on the order of the ion-inertial length and the Larmor radius, this behaviour changes and it is now becoming increasingly evident that the spectral break at these scales is also accompanied by an increase in magnetic compressibility. This has been attributed to a phase change in the physics at these scales − from fluid to kinetic − and in particular to the dominant role of the Hall-effect at sub-ion scales. We will be presenting results from the Cluster mission to show how this increase in the compressibility is dependent on the ion plasma beta and what implications this has for the physics at sub-ion scales in the context of prominent theories and models for kinetic plasma turbulence.
• Observations of EMIC Waves in the Exterior Cusp Region and in the Nearby Magnetosheath
  
  • Grison B.
  • Escoubet C. Philippe
  • Santolík O.
  • Lavraud B.
  • Cornilleau-Wehrlin Nicole
  , 2014, 13, pp.SM13F-4220. In the early years (2000-2004) of the mission, Cluster crossed the most distant part of the polar cusps. On 05/01/2002, Cluster enters the distant cusp region on the duskside of the southern hemisphere (inbound). The spacecraft are successively crossing the magnetopause between 19:50 UT (SC4) and 20:15 UT (SC3). The interplanetary conditions during the crossing were stable with a dominant negative By. The magnetometer (FGM) data indicates that the entry into the cusp takes place in a region where the magnetic field lines in the magnetosheath are anti-parallel with the field lines in the magnetosphere. Despite this clear picture, the global encounter is rather complex: one can notice partial magnetopause crossings, magnetic null points, and intense monochromatic waves on both sides of the magnetopause.We investigate electromagnetic ion cyclotron (EMIC) waves observed in the cusp and in the nearby magnetosheath, just before the magnetopause crossing by the spacecraft. Left-handed monochromatic waves observed in the cusp display different duration and frequency (below and above the local proton gyrofrequency) on each spacecraft. Both the Poynting flux of these emissions and the simultaneously recorded ion flows propagate in the same direction - toward the Earth. The wavenumber are determined in two ways: considering the Doppler shift and from direct measurements of the refractive index. We analyze these wave parameters and the local plasma conditions to explain the wave generation process on each side of the magnetopause.
• Context-Aware Resources Placement for SRAM-based FPGA to minimize Checkpoint/Recovery overhead
  
  • Sahraoui Fouad
  • Ghaffari Fakhreddine
  • Benkhelifa Mohamed El Amine
  • Granado Bertrand
  , 2014. no abstract (10.1109/ReConFig.2014.7032506)
  DOI : 10.1109/ReConFig.2014.7032506
• Fast SRAM-FPGA Fault Injection Platform based On Dynamic Partial Reconfiguration
  
  • Ghaffari Fakhreddine
  • Sahraoui Fouad
  • Benkhelifa Mohamed El Amine
  • Granado Bertrand
  • Kacou Marc Alexandre
  • Romain Olivier
  , 2014. SRAM-based FPGAs are very sensitive to harsh conditions, like radiations or ionizations, and need to be hardened to insure correct running. To validate any fault tolerant solution for these SRAM-FPGA, fault injection campaigns must be conducted carefully. In this work, we present a new design flow to perform localized internal fault injection on specific parts of a Design Under Test (DUT). To achieve this, we combine between Partial Dynamic Reconfiguration (PDR) via Internal Configuration Access Port (ICAP) for rapid fault insertion on SRAM; Isolation Design Flow (IDF) to isolate both of placement and routing of Design Under Test into a specific partial region. Moreover, we applied realistic fault distribution laws deduced from ground-based radiation experiments to reflect realistic behavior of FPGA toward radiations. The implemented injection platform using this flow shows the importance of using distribution laws driven approach. Results show that our fault injection experiments are done more than 15 times faster than one of the traditional FPGA based fault injection methods with a speed-up on simulation time up to 8. (10.1109/ICM.2014.7071827)
  DOI : 10.1109/ICM.2014.7071827
• Transient variations of vertical total electron content over some African stations from 2002 to 2012
  
  • Shimeis Amira
  • Amory-Mazaudier Christine
  • Fleury Rolland
  • Mahrous A.M.
  • Hassan A.F.
  Advances in Space Research, Elsevier, 2014, 54 (11), pp.2159–2171. This paper presents the vertical total electron content vTEC variations for three African stations, located at mid-low and equatorial latitudes, and operating since more than 10 years. The vTEC of the middle latitude GPS station in Alexandria, Egypt (31.2167°N; 29.9667°E, geographic) is compared to the vTEC of two others GPS stations: the first one in Rabat/Morocco (33.9981°N; 353.1457°E, geographic), and the second in Libreville/Gabon (0.3539°N; 9.6721°E, geographic). Our results discussed the diurnal, seasonal, and solar cycle dependences of vTEC at the local ionospheric conditions, during different phases of solar cycle in the light of the classification of Legrand and Simon. The vTEC over Alexandria exhibits the well-known equinoctial asymmetry which changes with the phases of the solar cycle; the spring vTEC is larger than that of autumn during the maximum, decreasing and minimum phases of solar cycle 23. During the increasing phase of solar cycle 24, it is the contrary. The diurnal variation of the vTEC presents multiple maxima during the equinox from 2005 to 2008 and during the summer solstice from 2006 to 2012. A nighttime vTEC enhancement and winter anomaly are also observed. During the deep solar minimum (2006–2009) the diurnal variation of the vTEC observed over Alexandria is similar to the diurnal variation observed during quiet magnetic period at equatorial latitudes. We observed also that the amplitude of vTEC at Libreville is larger than the amplitude of vTEC observed at Alexandria and Rabat, indeed Libreville is near the southern crest of the Equatorial Ionization anomaly. Finally, the correlation coefficient between vTEC and the sunspot number Rz is high and changes with solar cycle phases. (10.1016/j.asr.2014.07.038)
  DOI : 10.1016/j.asr.2014.07.038
• Reliability assessment of backward error recovery for SRAM-based FPGAs
  
  • Sahraoui Fouad
  • Ghaffari Fakhreddine
  • Benkhelifa Mohamed El Amine
  • Granado Bertrand
  , 2014. no abstract (10.1109/IDT.2014.7038622)
  DOI : 10.1109/IDT.2014.7038622
• Influence of the external electrical circuit on the regimes of a nanosecond repetitively pulsed discharge in air at atmospheric pressure
  
  • Tholin Fabien
  • Bourdon Anne
  Plasma Physics and Controlled Fusion, IOP Publishing, 2014, 57 (1). This paper presents 2D simulations of nanosecond repetitively pulsed discharges in air at atmospheric pressure coupled with a model of the external electrical circuit used in experiments. Then, during the pulsed discharge, the voltage applied to the electrodes varies in time as a function of the time dependent value of the plasma channel conductivity. In this work, we have simulated several consecutive nanosecond pulsed discharges between two point electrodes in air initially at 1000 K at a frequency of 10 kHz. First, we have simulated three consecutive nanosecond spark discharges. We have shown that the air temperature increases significantly pulse after pulse in the discharge channel. As a consequence, for the three consecutive simulated nanosecond spark discharges, we have put forward a decrease in the discharge radius, pulse after pulse. Then, to further limit the discharge current, a ballast resistance R has been added into the electrical circuit and the results are presented for seven consecutive nanosecond discharges. For a value of R = 1000 Ω in the conditions studied in this work, we have shown that the first nanosecond discharges are in the glow regime, with a small gas heating per pulse. However, as the number of pulses increases due to the gas heating by each pulse, the discharge may transit to a multipulse nanosecond spark regime. For a higher value of R = 10 000 Ω, we have put forward that the gas heating by each nanosecond discharge becomes negligible and then the multipulse nanosecond discharge remains in this case in a stable 'quasi-periodic' multipulse glow regime. (10.1088/0741-3335/57/1/014016)
  DOI : 10.1088/0741-3335/57/1/014016
• Fluid simulations for atmospheric pressure low-temperature plasmas
  
  • Bourdon Anne
  , 2014.
• Control over the ion flux obtained by sawtooth-like waveforms in radiofrequency capacitively coupled plasmas
  
  • Bruneau Bastien
  • Novikova T.
  • Lafleur Trevor
  • Booth Jean-Paul
  • Johnson Erik
  , 2014.
• The NEPTUNE Bipolar Source: A New Instrument for Surface Treatment Applications
  
  • Rafalskyi D.V.
  • Aanesland Ane
  , 2014, pp.191.
• Diagnostics of Cl<SUB>2</SUB>/O<SUB>2</SUB> Inductively-Coupled Plasmas by Ultra-High sensitivity Broad-Band Absorption Spectroscopy
  
  • Foucher Mickaël
  • Marinov Daniil
  • Carbone Emile
  • Booth Jean-Paul
  • Chabert Pascal
  , 2014.
• Advanced ion mass spectrometer for giant planet ionospheres, magnetospheres and moons
  
  • Sittler E.
  • Cooper J.F.
  • Paschalidis N.
  • Mcdonald E.A.
  • Ali A.
  • Coplan M.A.
  • Chornay D.
  • Sranatos M.
  • Sturners S.J.
  • Bateman F.B.
  • Fontaine Dominique
  • Verdeil Christophe
  • André N.
  • Fedorov A. O.
  • Wurz Peter
  , 2014.
• Experimental Study of Pure Air-Plasma Bullets Propagating in Microcapillaries and Ambient Air
  
  • Lacoste D.A.
  • Bourdon Anne
  • Kuribara Koichi
  • Urabe Keiichiro
  • Stauss Sven
  • Terashima K.
  , 2014.
• Inductively-coupled plasmas (ICP) of Cl<SUB>2</SUB>, O<SUB>2</SUB> and mixtures : measurements of atoms, ClxOy and electron densities
  
  • Foucher Mickaël
  • Marinov Daniil
  • Carbone Emile
  • Booth Jean-Paul
  • Chabert Pascal
  , 2014.
• Using the DC self-bias effect for simultaneous ion-electron beam generation in space thruster applications
  
  • Rafalskyi D.V.
  • Aanesland Ane
  , 2014, 59 (9), pp.16.
• Inductively-coupled plasmas of Cl<SUB>2</SUB>, O<SUB>2</SUB> and mixtures : measurement of atoms, Cl<SUB>x</SUB>O<SUB>y</SUB> and electron densities
  
  • Foucher Mickaël
  • Marinov Daniil
  • Carbone Emile
  • Booth Jean-Paul
  • Chabert Pascal
  , 2014.
• Influence of the amount of N<SUB>2</SUB> admixture on the dynamics of atmospheric pressure helium discharges in capillary tubes
  
  • Bourdon Anne
  • Pechereau F.
  • Viegas Pedro
  , 2014.
• Iodine as propellant for electric space propulsion
  
  • Grondein Pascaline
  • Lafleur Trevor
  • Chabert Pascal
  • Aanesland Ane
  , 2014.
• High sensitivity ultra-broad-band absorption spectroscopy applied to etching plasmas
  
  • Foucher Mickaël
  • Marinov Daniil
  • Carbone Emile
  • Booth Jean-Paul
  • Chabert Pascal
  , 2014.
• The physics, performance and predictions of the PEGASES ion-ion thruster
  
  • Aanesland Ane
  , 2014.
• Hybrid Focal Stereo Networks for Pattern Analysis in Homogeneous Scenes
  
  • Aldea Emanuel
  • Kiyani K. H.
  , 2014. In this paper we address the problem of multiple camera calibration in the presence of a homogeneous scene, and without the possibility of employing calibration object based methods. The proposed solution exploits salient features present in a larger field of view, but instead of employing active vision we replace the cameras with stereo rigs featuring a long focal analysis camera, as well as a short focal registration camera. Thus, we are able to propose an accurate solution which does not require intrinsic variation models as in the case of zooming cameras. Moreover, the availability of the two views simultaneously in each rig allows for pose re-estimation between rigs as often as necessary. The algorithm has been successfully validated in an indoor setting, as well as on a difficult scene featuring a highly dense pilgrim crowd in Makkah.
• Coincident ion acceleration and electron extraction for space propulsion using the self-bias formed on a set of RF biased grids bounding a plasma source
  
  • Rafalskyi D.V.
  • Aanesland Ane
  Journal of Physics D: Applied Physics, IOP Publishing, 2014, 47 (49), pp.495-203. We propose an alternative method to accelerate ions in classical gridded ion thrusters and ion sources such that co-extracted electrons from the source may provide beam space charge neutralization. In this way there is no need for an additional electron neutralizer. The method consists of applying RF voltage to a two-grid acceleration system via a blocking capacitor. Due to the unequal effective area of the two grids in contact with the plasma, a dc self-bias is formed, rectifying the applied RF voltage. As a result, ions are continuously accelerated within the grid system while electrons are emitted in brief instants within the RF period when the RF space charge sheath collapses. This paper presents the first experimental results and a proof-of-principle. Experiments are carried out using the Neptune thruster prototype which is a gridded Inductively Coupled Plasma (ICP) source operated at 4 MHz, attached to a larger beam propagation chamber. The RF power supply is used both for the ICP discharge (plasma generation) and powering the acceleration grids via a capacitor for ion acceleration and electron extraction without any dc power supplies. The ion and electron energies, particle flux and densities are measured using retarding field energy analyzers (RFEA), Langmuir probes and a large beam target. The system operates in Argon and N2. The dc self-bias is found to be generated within the gridded extraction system in all the range of operating conditions. Broad quasi-neutral ion-electron beams are measured in the downstream chamber with energies up to 400 eV. The beams from the RF acceleration method are compared with classical dc acceleration with an additional external electron neutralizer. It is found that the two acceleration techniques provide similar performance, but the ion energy distribution function from RF acceleration is broader, while the floating potential of the beam is lower than for the dc accelerated beam. (10.1088/0022-3727/47/49/495203)
  DOI : 10.1088/0022-3727/47/49/495203
• Spatio-temporal Consistency for Head Detection in High-Density Scenes
  
  • Aldea Emanuel
  • Marastoni Davide
  • Kiyani K. H.
  , 2014. In this paper we address the problem of detecting reliably a subset of pedestrian targets (heads) in a high-density crowd exhibiting extreme clutter and homogeneity, with the purpose of obtaining tracking initializations. We investigate the solution provided by discriminative learning where we require that the detections in the image space be localized over most of the target area and temporally stable. The results of our tests show that discriminative learning strategies provide valuable cues about the target localization which may be combined with other complementary strategies in order to bootstrap tracking algorithms in these challenging environments.
• WHISTLER MODE WAVES AND THE ELECTRON HEAT FLUX IN THE SOLAR WIND: CLUSTER OBSERVATIONS
  
  • Lacombe C.
  • Alexandrova Olga
  • Matteini L
  • Santolik O.
  • Cornilleau-Wehrlin Nicole
  • Mangeney Anne
  • de Conchy Y.
  • Maksimovic M.
  The Astrophysical Journal, American Astronomical Society, 2014, 796 (1), pp.5. The nature of the magnetic field fluctuations in the solar wind between the ion and electron scales is still under debate. Using the Cluster/STAFF instrument, we make a survey of the power spectral density and of the polarization of these fluctuations at frequencies f in [1, 400] Hz, during five years (2001-2005), when Cluster was in the free solar wind. In ~10% of the selected data, we observe narrowband, right-handed, circularly polarized fluctuations, with wave vectors quasi-parallel to the mean magnetic field, superimposed on the spectrum of the permanent background turbulence. We interpret these coherent fluctuations as whistler mode waves. The lifetime of these waves varies between a few seconds and several hours. Here, we present, for the first time, an analysis of long-lived whistler waves, i.e., lasting more than five minutes. We find several necessary (but not sufficient) conditions for the observation of whistler waves, mainly a low level of background turbulence, a slow wind, a relatively large electron heat flux, and a low electron collision frequency. When the electron parallel beta factor β e∥ is larger than 3, the whistler waves are seen along the heat flux threshold of the whistler heat flux instability. The presence of such whistler waves confirms that the whistler heat flux instability contributes to the regulation of the solar wind heat flux, at least for β e∥ ≥ 3, in slow wind at 1 AU. (10.1088/0004-637X/796/1/5)
  DOI : 10.1088/0004-637X/796/1/5
• Laser guided discharges from a compact Marx generator
  
  • Houard Aurélien
  • Arantchouk Léonid
  • Point G.
  • Brelet Yohann
  • Larour Jean
  • Carbonnel Jérôme
  • André Y-B.
  • Mysyrowicz André
  , 2014.