Publications

2011

• Lower hybrid resonances stimulated by the four CLUSTER relaxation sounders deep inside the plasmasphere: observations and inferred plasma characteristics
  
  • Kougblénou S
  • Lointier G
  • Décréau Pierrette
  • Trotignon Jean-Gabriel
  • Rauch Jean-Louis
  • Vallières Xavier
  • Canu Patrick
  • Masson A
  • Pickett J
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.2003–2018. The frequency range of the WHISPER relaxation sounder instrument on board CLUSTER, 4–80 kHz, has been chosen so as to encompass the electron gyro-frequency, F ce , and the electron plasma frequency, F p , in most regions to be explored. Measurement of those frequencies, which are triggered as resonances by the sounder, provides a direct estimation of in situ fundamental plasma characteristics: electron density and magnetic field intensity. In the late mission phase, CLUSTER penetrated regions deep inside the plas-masphere where F ce and F p are much higher than the upper frequency of the sounder's range. However, they are of the right order of magnitude as to place the lower hybrid frequency , F lh , in the 4–15 kHz band. This characteristic frequency , placed at a resonance of the medium, is triggered by the sounder's transmitter and shows up as an isolated peak in the received spectrum, not present in spectra of naturally occuring VLF waves. This paper illustrates, from analysis of case events, how measured F lh values give access to a plasma diagnostic novel of its kind. CLUSTER, travelling along its orbit, encounters favourable conditions where F ce is increasing and F p decreasing, such that F ce /F p increases from values below unity to values above unity. Measured F lh values thus give access, in turn, to the effective mass, M eff , indicative of plasma ion composition, and to the core plasma-sphere electron density value, a parameter difficult to measure. The analysed case events indicate that the estimated quantities (M eff in the 1.0–1.4 range, N e in the 5 × 10 2 – 10 4 cm −3 range) are varying with external factors (altitude, L value, geomagnetic activity) in a plausible way. Although covering only a restricted region (mid-latitude, low altitude inner plasmasphere), these measurements are available, since Correspondence to: S. Kougblénou (sena.kougblenou@cnrs-orleans.fr) late 2009, for all CLUSTER perigee passes not affected by eclipses (on average, roughly a third of a total of ∼200 passes per year) and offer multipoint observations previously unavailable in this region. (10.5194/angeo-29-2003-2011)
  DOI : 10.5194/angeo-29-2003-2011
• Triple Q : A three channel quantum cascade laser absorption spectrometer for fast multiple species concentration measurements
  
  • Hübner M.
  • Welzel S.
  • Marinov Daniil
  • Guaitella Olivier
  • Glitsch S.
  • Rousseau Antoine
  • Röpcke J.
  Review of Scientific Instruments, American Institute of Physics, 2011, 82, pp.093102. A compact and transportable three channel quantum cascade laser system (TRIPLE Q) based on mid-infrared absorption spectroscopy has been developed for time-resolved plasma diagnostics. The TRIPLE Q spectrometer encompasses three independently controlled quantum cascade lasers (QCLs), which can be used for chemical sensing, particularly for gas phase analysis of plasmas. All three QCLs are operated in the intra-pulse mode with typical pulse lengths of the order of 150 ns. Using a multiplexed detection, a time resolution shorter than 1 μs can be achieved. Hence, the spectrometer is well suited to study kinetic processes of multiple infrared active compounds in reactive plasmas. A special data processing and analysis technique has been established to account for time jitter effects of the infrared emission of the QCLs. The performance of the TRIPLE Q system has been validated in pulsed direct current plasmas containing N2O/air and NO2/air. (10.1063/1.3633952)
  DOI : 10.1063/1.3633952
• Observation and theoretical modeling of electron scale solar wind turbulence
  
  • Sahraoui Fouad
  • Goldstein M. L.
  • Abdul-Kader K.
  • Belmont Gérard
  • Rezeau Laurence
  • Robert Patrick
  • Canu Patrick
  Comptes Rendus. Physique, Académie des sciences (Paris), 2011, 12 (2), pp.132-140. Turbulence at MagnetoHydroDynamics (MHD) scales in the solar wind has been studied for more than three decades, using data analysis, theoretical and numerical modeling. However, smaller scales have not been explored until very recently. Here, we review recent results on the first observation of cascade and dissipation of the solar wind turbulence at the electron scales. Thanks to the high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectra of turbulence up to (in the spacecraft reference frame) and found evidence of energy dissipation around the Doppler-shifted electron gyroscale . Before its dissipation, the energy is shown to undergo two cascades: a Kolmogorov-like cascade with a scaling above the proton gyroscale, and a new cascade at the sub-proton and electron gyroscales. Above the spectrum has a steeper power law down to the noise level of the instrument. Solving numerically the linear MaxwellVlasov equations combined with recent theoretical predictions of the Gyro-Kinetic theory, we show that the present results are consistent with a scenario of a quasi-two-dimensional cascade into Kinetic Alfvén modes (KAW). New analyses of other data sets, where the Cluster separation (of about ) allowed us to explore the sub-proton scales using the k-filtering technique, and to confirm the 2D nature of the turbulence at those scales. (10.1016/j.crhy.2010.11.008)
  DOI : 10.1016/j.crhy.2010.11.008
• Physics of Radio-Frequency Plasmas
  
  • Chabert Pascal
  • Braithwaite Nicholas
  , 2011. Low-temperature radio frequency plasmas are essential in various sectors of advanced technology, from micro-engineering to spacecraft propulsion systems and efficient sources of light. The subject lies at the complex interfaces between physics, chemistry and engineering. Focusing mostly on physics, this book will interest graduate students and researchers in applied physics and electrical engineering. The book incorporates a cutting-edge perspective on RF plasmas. It also covers basic plasma physics including transport in bounded plasmas and electrical diagnostics. Its pedagogic style engages readers, helping them to develop physical arguments and mathematical analyses. Worked examples apply the theories covered to realistic scenarios, and over 100 in-text questions let readers put their newly acquired knowledge to use and gain confidence in applying physics to real laboratory situations.
• Control of Nanocrystalline Silicon Growth Phase and Deposition Rate through Voltage Waveform Tailoring during PECVD
  
  • Johnson E.V.
  • Pouliquen S.
  • Delattre Pierre-Alexandre
  • Booth Jean-Paul
  MRS Online Proceedings Library, Cambridge University Press, 2011, 1339, pp.mrss11-1339-s04-5. The use of Voltage Waveform Tailoring (VWT) that is the use of non-sinusoidal waveforms with a period equivalent to RF frequencies is shown to be effective in modifying the electric field distribution in a parallel plate, capacitively coupled laboratory plasma deposition reactor, and thus in changing the growth mode of silicon thin films from amorphous to nanocrystalline. The use of the VWT technique allows one to decouple the power injected into the plasma from the ion-bombardment energy at the film surface without changing any other deposition parameters, such as pressure or gas mixture. Material results are presented for an H2/SiH4 gas composition. A peaks type waveform increases the ion-bombardment energy at the RF electrode and reduces it at the substrate, resulting in more nanocrystalline growth. The use of a valleys-type waveform has the opposite effect, and results in more amorphous growth. We show the dependence of the process on silane dilution and pressure, including results on changes to the deposition rate when changing the excitation voltage waveform. (10.1557/opl.2011.993)
  DOI : 10.1557/opl.2011.993
• Successive Nanosecond Discharges in Water
  
  • Marinov Ilya
  • Guaitella Olivier
  • Rousseau Antoine
  • Starikovskaia Svetlana
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2011, 39 (11), pp.2672-2673. Successive discharges of alternating polarities in distilled water have been studied. Cathode-initiated discharges develop in two possible configurations: slow and weakly luminescent bushlike mode or fast and luminous treelike mode with well-pronounced branching. Under our experimental conditions, the two modes originate with approximately equal probability. Positive discharge demonstrates only one discharge morphology with two hemispherical weakly luminescent structures. Successive negative pulse results in the formation of one of the negative modes, bushlike or treelike. (10.1109/TPS.2011.2147337)
  DOI : 10.1109/TPS.2011.2147337
• Turbulence propagation in heat flux-driven plasmas: implications for temperature profile structure
  
  • Wang Z.H.
  • Diamond P.H.
  • Gürcan Özgür D.
  • Garbet X.
  • Wang X.G.
  Nuclear Fusion, IOP Publishing, 2011, 51, pp.073009. Turbulence propagation and temperature profile evolution are studied in heat flux-driven plasmas. A simple model consisting of coupled non-linear reactiondiffusion equations for both turbulence and heat transport is proposed to elucidate several aspects of apparent non-local profile dynamics. Self-consistent E × B shear feedback on turbulence intensity growth and transport is also included in the model. Temperature profile evolution is studied in the presence of an intensity pulse propagating inwards but also interacting with an outward propagating heat pulse. It is found that as the heat flux Q increases, the intensity pulse speed first grows as √ Q and then decays as 1/Q, while the heat pulse speed finally saturates at the level given by neoclassical transport. Intensity pulse propagation can be effectively saturated at or above a critical heat flux, so that the formation of an internal transport barrier (ITB) can be triggered. This suggests that the ITB location is ultimately determined by both heat flux and edge turbulence conditions, and thus the ITB inhibits both the inward turbulence propagation and the outward turbulent heat transport. As a test of turbulence spreading dynamics, the intensity pulse propagation through gaps in turbulence excitation and its implications for profile response to off-axis heat deposition are also investigated. It is shown that the profile resilience phenomena can be recovered by taking into account intensity pulse propagation. (10.1088/0029-5515/51/7/073009)
  DOI : 10.1088/0029-5515/51/7/073009
• INCLINE - Inductively coupled plasma for CMOS-compatible etching of III-V integrated laser sources
  
  • Bouchoule S.
  • Gatilova L.
  • Patriarche G.
  • Guilet S.
  • Le Gratiet L.
  • Vallier L.
  • Chabert Pascal
  • Booth Jean-Paul
  • Chanson R.
  • Rhallabi A.
  • Cardinaud C.
  • Rojo-Romeo P.
  • Leclercq J.-L.
  • Letartre X.
  , 2011.
• Reactivity of atoms adsorbed on catalytic surfaces under plasma exposure
  
  • Marinov Daniil
  • Guaitella Olivier
  • Rousseau Antoine
  , 2011.
• Reactivity and adsorption of N atoms on catalytic surfaces
  
  • Marinov Daniil
  • Guaitella Olivier
  • Rousseau Antoine
  , 2011.
• Solar wind, mass and momentum losses during the solar cycle
  
  • Pinto Rui
  • Brun Allan Sacha
  • Jouve Laurène
  • Grappin Roland
  , 2011, 271 (2010-06-21 / 2010-06-25), pp.395-396. We study the connections between the sun's convection zone evolution and the dynamics of the solar wind and corona. We input the magnetic fields generated by a 2.5D axisymmetric kinematic dynamo code (STELEM) into a 2.5D axisymmetric coronal MHD code (DIP). The computations were carried out for an 11 year cycle. We show that the solar wind's velocity and mass flux vary in latitude and in time in good agreement with the well known time-latitude assymptotic wind speed diagram. Overall sun's mass loss rate, momentum flux and magnetic breaking torque are maximal near the solar minimum. (10.1017/S1743921311017960)
  DOI : 10.1017/S1743921311017960
• Cluster Observations of Magnetopause Reconnection at Sub-Proton Scales
  
  • Retinò Alessandro
  • Vaivads A.
  • Sahraoui Fouad
  • Le Contel Olivier
  • Zieger B.
  • Nakamura R.
  • Mozer F. S.
  , 2011.
• Space Exploration Technologies Pegases A new promising electric propulsion concept
  
  • Aanesland Ane
  • Mazouffre S.
  • Chabert Pascal
  Europhysics News, EDP Sciences, 2011, 42 (6), pp.28-31. This article has no abstract (10.1051/epn/2011604)
  DOI : 10.1051/epn/2011604
• Edge Temperature Gradient as Intrinsic Rotation Drive in Alcator C-Mod Tokamak Plasmas
  
  • Rice J.E.
  • Hughes J.W.
  • Diamond P.H.
  • Kosuga Y.
  • Podpaly Y.A.
  • Reinke M.L.
  • Greenwald M.J.
  • Gürcan Özgür D.
  • Hahm T.S.
  • Hubbard A.E.
  • Marmar E.S.
  • Mcdevitt C.J.
  • Whyte D.G.
  Physical Review Letters, American Physical Society, 2011, 106, pp.215001. Intrinsic rotation has been observed in I-mode plasmas from the C-Mod tokamak, and is found to be similar to that in H mode, both in its edge origin and in the scaling with global pressure. Since both plasmas have similar edge ∇T, but completely different edge ∇n, it may be concluded that the drive of the intrinsic rotation is the edge ∇T rather than ∇P. Evidence suggests that the connection between gradients and rotation is the residual stress, and a scaling for the rotation from conversion of free energy to macroscopic flow is calculated. (10.1103/PhysRevLett.106.215001)
  DOI : 10.1103/PhysRevLett.106.215001
• Global distribution of electrostatic electron cyclotron harmonic waves observed on THEMIS
  
  • Ni B.
  • Thorne R. M.
  • Liang Jun
  • Angelopoulos V.
  • Cully C. M.
  • Li W.
  • Zhang Xiaojia
  • Hartinger Michael
  • Le Contel Olivier
  • Roux A.
  Geophysical Research Letters, American Geophysical Union, 2011, 38, pp.17105. A global, statistical analysis of electrostatic electron cyclotron harmonic (ECH) waves is performed using THEMIS wave data. Our results confirm the high occurrence of <1 mV/m ECH emissions throughout the outer magnetosphere (L > 5). The strongest (>=1 mV/m) ECH waves are enhanced during geomagnetically disturbed periods, and are mainly confined close to the magnetic equator (|lambda| < 3°) over the region L <= 10 in the night and dawn MLT sector. ECH wave intensities within 3° <= |lambda| < 6° are generally much weaker but not negligible especially for L < 12 on the midnight side. Furthermore, the occurrence rates and variability of moderately intense (>=0.1 mV/m) ECH emissions suggest that ECH wave scattering could contribute to diffuse auroral precipitation in the outer (L > 8) magnetosphere where chorus emissions are statistically weak. (10.1029/2011GL048793)
  DOI : 10.1029/2011GL048793
• Plasmoid Releases in the Heliospheric Current Sheet and Associated Coronal Hole Boundary Layer Evolution
  
  • Foullon C.
  • Lavraud B.
  • Luhmann J. G.
  • Farrugia C. J.
  • Retinò Alessandro
  • Simunac K. D. C.
  • Wardle N. C.
  • Galvin A. B.
  • Kucharek H.
  • Owen C. J.
  • Popecki M.
  • Opitz A.
  • Sauvaud J.-A.
  The Astrophysical Journal, American Astronomical Society, 2011, 737, pp.16. As the heliospheric current sheet (HCS) is corotating past STEREO-B, near-Earth spacecraft ACE, Wind and Cluster, and STEREO-A over more than three days between 2008 January 10 and 14, we observe various sections of (near-pressure-balanced) flux-rope- and magnetic-island-type plasmoids in the associated heliospheric plasma sheet (HPS). The plasmoids can qualify as slow interplanetary coronal mass ejections and are relatively low proton beta (<0.5) structures, with small length scales (an order of magnitude lower than typical magnetic cloud values) and low magnetic field strengths (2-8 nT). One of them, in particular, detected at STEREO-B, corresponds to the first reported evidence of a detached plasmoid in the HPS. The in situ signatures near Earth are associated with a long-decay X-ray flare and a slow small-scale streamer ejecta, observed remotely with white-light coronagraphs aboard STEREO-B and SOHO and tracked by triangulation. Before the arrival of the HPS, a coronal hole boundary layer (CHBL) is detected in situ. The multi-spacecraft observations indicate a CHBL stream corotating with the HCS but with a decreasing speed distribution suggestive of a localized or transient nature. While we may reasonably assume that an interaction between ejecta and CHBL provides the source of momentum for the slow ejecta's acceleration, the outstanding composition properties of the CHBL near Earth provide here circumstantial evidence that this interaction or possibly an earlier one, taking place during streamer swelling when the ejecta rises slowly, results in additional mixing processes. (10.1088/0004-637X/737/1/16)
  DOI : 10.1088/0004-637X/737/1/16
• A new 3D parallel multi-species hybrid model for Solar Wind - Mars interaction
  
  • Hess Sebastien
  • Modolo Ronan
  • Mancini Marco
  • Leblanc François
  • Chaufray Jean-Yves
  • Yagi Manabu
  • Allioux R.
  • Richer Emilie
  • Chanteur Gérard
  , 2011, pp.EPSC-DPS2011-770. In the frame of the HELIOSARES project (PI F. Leblanc) dedicated to the modeling of Mars environment (neutral and charged species) from the lower atmosphere to the solar wind, a modeling effort of parallelization has been conducted. Such model allows having a kinetic description of the ions with a rather improved spatial resolution (smaller than the ion inertial less). The latest progresses are reported and simulations results with a uniform spatial resolution of 75 km are presented.
• Anisotropic shell model of turbulence
  
  • Gürcan Özgür D.
  • Grappin Roland
  Physical Review E, American Physical Society (APS), 2011, 84, pp.066308. An anisotropic shell model has been proposed for two-dimensional (2D) turbulence. It is similar to the 2D version of the Gledzer-Ohkitani-Yamada model but with the angular variable in wave-number space divided into three distinct directions representing structures elongated in different directions. In the case when the drive is isotropic the usual isotropic solution is recovered as the fixed point of this model. The Hasegawa-Mima limit of the model is considered in particular due to its relevance for 2D anisotropic systems such a quasigeostrophic and plasma turbulence. It is observed from this simple model that the anisotropy diminishes as a function of scale during the cascade process, and the maximum of the energy is not at the node that has maximum drive, but at a nearby node that is directly coupled to that one. (10.1103/PhysRevE.84.066308)
  DOI : 10.1103/PhysRevE.84.066308
• NO kinetics in pulsed low-pressure plasmas studied by time-resolved quantum cascade laser absorption spectroscopy
  
  • Welzel S.
  • Guaitella Olivier
  • Lazzaroni Claudia
  • Pintassilgo C.D.
  • Rousseau Antoine
  • Röpcke J.
  Plasma Sources Science and Technology, IOP Publishing, 2011, 20, pp.015020. Time-resolved quantum cascade laser absorption spectroscopy at 1897&#8201;cm&#8722;1 (5.27&#8201;µm) has been applied to study the NO(X) kinetics on the micro- and millisecond time scale in pulsed low-pressure N2/NO dc discharges. Experiments have been performed under flowing and static gas conditions to infer the gas temperature increase and the consequences for the NO line strength. A relatively small increase of ~20&#8201;K is observed during the early plasma phase of a few milliseconds. After some 10&#8201;ms gas temperatures up to 500&#8201;K can be deduced. The experimental data for the NO mixing ratio were compared with the results from a recently developed time-dependent model for pulsed N2O2 plasmas which are well in accord. The early plasma pulse is determined by vibrational heating of N2 while the excitation of NO(X) by N2 metastables is almost completely balanced. Efficient NO depletion occurs after several milliseconds by N atom impact. (10.1088/0963-0252/20/1/015020)
  DOI : 10.1088/0963-0252/20/1/015020
• Role of charge photodesorption in self-synchronized breakdown of surface streamers in air at atmospheric pressure
  
  • Guaitella Olivier
  • Marinov Ilya
  • Rousseau Antoine
  Applied Physics Letters, American Institute of Physics, 2011, 98, pp.071502. A surface dielectric barrier discharge configuration with two identical high voltage electrodes is investigated in air at atmospheric pressure. Synchronized breakdown of streamers on both electrodes is evidenced by statistical study. The light emitted by plasma filament on one electrode can trigger the breakdown of streamers on the other electrode. The role of photodesorption of negative charges deposited on the Pyrex dielectric barrier is responsible for these self-synchronized breakdowns. The binding energy of negative charges photodesorbed is estimated to be lower than 3.5 eV. (10.1063/1.3552965)
  DOI : 10.1063/1.3552965
• Impact of collisionality on fluctuation characteristics of micro-turbulence
  
  • Vermare Laure
  • Hennequin Pascale
  • Gürcan Özgür D.
  • Bourdelle C.
  • Clairet F.
  • Garbet X.
  • Sabot R.
  • Tore Supra Team
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.012306. The influence of changing collisionality on density fluctuation characteristics is studied during dedicated &#957;&#8727; scaling experiments, using Doppler backscattering system. First, the repartition of fluctuation energy over different spatial scales, as represented by the wavenumber spectrum, is investigated and a modification of the shape of the perpendicular wavenumber spectrum in the low wavenumber part of the spectrum is observed when changing collisionality. In addition, a new procedure to evaluate the dispersion relation of micro-turbulence is presented. From the behavior of the perpendicular mean velocity of density fluctuations with the perpendicular wavenumber, different dispersion relations are obtained between low and high collisionality cases. (10.1063/1.3536648)
  DOI : 10.1063/1.3536648
• Observations and modeling of forward and reflected chorus waves captured by THEMIS
  
  • Agapitov O
  • Krasnoselskikh V
  • Zaliznyak Yu
  • Angelopoulos V
  • Le Contel Olivier
  • Rolland G
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.541-550. Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms) spacecraft Search Coil Magnetome-ter (SCM) and Electric Field Instrument (EFI) at ELF/VLF frequencies up to 4 kHz at L ≥ 8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar , discrete structure and rising tones, reflected waves are attenuated by a factor of 10–30 and have 10% higher frequency than concurrently-observed forward waves. Model-ing of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger. (10.5194/angeo-29-541-2011)
  DOI : 10.5194/angeo-29-541-2011
• On the effect of IMF turning on ion dynamics at Mercury
  
  • Delcourt Dominique C.
  • Moore T. E.
  • Fok M.-C. H.
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.987-996. We investigate the effect of a rotation of the Interplanetary Magnetic Field (IMF) on the transport of magnetospheric ion populations at Mercury. We focus on ions of planetary origin and investigate their large-scale circulation using three-dimensional single-particle simulations. We show that a nonzero B<SUB>X</SUB> component of the IMF leads to a pronounced asymmetry in the overall circulation pattern. In particular, we demonstrate that the centrifugal acceleration due to curvature of the E × B drift paths is more pronounced in one hemisphere than the other, leading to filling of the magnetospheric lobes and plasma sheet with more or less energetic material depending upon the hemisphere of origin. Using a time-varying electric and magnetic field model, we investigate the response of ions to rapid (a few tens of seconds) re-orientation of the IMF. We show that, for ions with gyroperiods comparable to the field variation time scale, the inductive electric field should lead to significant nonadiabatic energization, up to several hundreds of eVs or a few keVs. It thus appears that IMF turning at Mercury should lead to localized loading of the magnetosphere with energetic material of planetary origin (e.g., Na<SUP> </SUP>). (10.5194/angeo-29-987-2011)
  DOI : 10.5194/angeo-29-987-2011
• Estimation of magnetic field mapping accuracy using the pulsating aurora-chorus connection
  
  • Nishimura Y.
  • Bortnik J.
  • Li W.
  • Thorne R. M.
  • Lyons L.R.
  • Angelopoulos V.
  • Mende S. B.
  • Bonnell J. W.
  • Le Contel Olivier
  • Cully C. M.
  • Ergun R.
  • Auster U.
  Geophysical Research Letters, American Geophysical Union, 2011, 38, pp.14110. Although magnetic field models are widely used in magnetosphere-ionosphere coupling studies to perform field-line mapping, their accuracy has been difficult to estimate experimentally. Taking advantage of the high correlation between lower-band chorus and pulsating aurora, we located the THEMIS spacecraft footprint within km accuracy and calculated the differences from mappings given in widely-used Tsyganenko models. Using 13 conjunctions of the THEMIS spacecraft and ground-based imagers, we found that the Tsyganenko model footprints were located within 1°-2° magnetic latitude and 0.1-0.2 h magnetic local time of our derived footprint. The deviation between the footprints has a consistent dependence on geomagnetic activity. Our results showed that the real magnetic field tends to be less stretched than that in the Tsyganenko models during quiet times and comparable to or more stretched during disturbed times. This approach can be used to advance modeling of field lines that connect to the near-Earth plasma sheet. (10.1029/2011GL048281)
  DOI : 10.1029/2011GL048281
• Jet front-driven mirror modes and shocklets in the near-Earth flow-braking region
  
  • Zieger B.
  • Retinò Alessandro
  • Nakamura R.
  • Baumjohann W.
  • Vaivads A.
  • Khotyaintsev Y. V.
  Geophysical Research Letters, American Geophysical Union, 2011, 38, pp.22103. We investigate the small-scale structure of jet fronts through a case study of multi-spacecraft Cluster observations in the near-Earth flow-braking region at -10 RE. We find that the interaction between the earthward moving fast plasma jet and the high-&#946; ambient plasma in the plasma sheet results in magnetic pileup and compression ahead of the jet and rarefaction trailing the jet. It is shown that mirror-mode structures of ion gyroradius scale develop within the pileup region due to the observed ion temperature anisotropy (Ti⊥ > Ti\parallel). We suggest that the growth of these mirror modes is driven by the perpendicular total pressure perturbation (&#916;p⊥) generated by the braking jet. When &#916;p⊥ becomes too large, the mirror-mode structure cannot maintain pressure balance any longer, and consequently a shocklet is formed in the pileup region ahead of the jet front. We present the first evidence for such a kinetic shocklet in the flow-braking region. (10.1029/2011GL049746)
  DOI : 10.1029/2011GL049746