Publications

2013

• Collisionless Plasmas in Astrophysics
  
  • Belmont Gérard
  • Grappin Roland
  • Mottez Fabrice
  • Pantellini F.
  • Pelletier Guy
  , 2013 (ISBN: 978-3-527-41074-3).
• Non thermal Pasma regeneration of Acetone adsorbed TiO<SUB>2</SUB> Surface
  
  • Sivachandiran Loganathan
  • Thévenet Frédéric
  • Rousseau Antoine
  Plasma Chemistry and Plasma Processing, Springer Verlag, 2013. Improvement of indoor air quality regarding volatile organic compounds (VOCs) requires the development of innovative oxidation processes. This paper investigates the coupling of a metal oxide sorbent with non-thermal plasma (NTP) in an especially designed reactor. TiO2 was selected as model sorbent and acetone was used as model VOC. The analyses of gas phase species at the reactor downstream have been performed using FTIR spectroscopy. In a first step, acetone adsorption on TiO2 surface under dry air was characterized in terms of total amount adsorbed, as well as reversibly and irreversibly adsorbed fractions. Obtained results were compared and discussed with literature in terms of acetone reactive adsorption on TiO2 surface. Mesityloxide was proposed as the major compound in the irreversibly adsorbed fraction. In a second time, acetone saturated TiO2 surface was exposed to NTP surface discharge. Irrespectively of the injected power, <30 % of the initially adsorbed acetone has been recovered as CO, CO2 and desorbed acetone. Finally, thermal desorptions have been performed. They evidenced that (1) NTP treatment modifies the nature of the adsorbed organic species, (2) mineralization rate is considerably improved. Based on desorbed species temporal profile analysis, carboxylates and more especially formates are suggested as major adsorbed species after NTP treatment (Pinj > 0.2 W). This hypothesis has been evaluated and confirmed. This paper finally evidenced that NTP can be used as an efficient pretreatment technique to promote the mineralization of adsorbed acetone for further thermal treatment (10.1007/s11090-013-9463-7)
  DOI : 10.1007/s11090-013-9463-7
• Investigation of NO and NO<SUB>2</SUB> adsorption mechanisms on TiO<SUB>2</SUB> at room temperature
  
  • Sivachandiran Loganathan
  • Thévenet Frédéric
  • Gravelat Paul
  • Rousseau Antoine
  Applied Catalysis B: Environmental, Elsevier, 2013, 142-143, pp.196-204. In this study, NO and NO2 adsorption mechanisms on TiO2 at room temperature have been investigated separately. Atmospheric pressure gas phase Fourier Transform Infrared Spectroscopy (FTIR) coupled to adsorption and temperature programmed desorption (TPD) experiments have been used to characterize gas phase and adsorbed phase species. TiO2 coated glass beads packed-bed reactor has been designed and used for NO and NO2 adsorption and storage capacity under dark and gas-flowing conditions at room temperature. For NO adsorption, experimental data suggests that, at room temperature, NO shows no significant adsorption on TiO2. On the other hand NO2 adsorbs in a reactive way by evolving NO in the gas phase. We quantitatively evidenced that, the ratio between consumed NO2, desorbed NO2 by TPD after adsorption and produced NO during NO2 adsorption is 3:2:1, by a qualitative and quantitative analysis performed downstream the reactor. Based on the quantitative analysis, a new NO2 adsorption mechanism on TiO2 at room temperature has been proposed, and validated for various NO2 inlet concentrations. The proposed mechanism is valid on the investigated NO2 inlet concentration range. In addition, it was found that, NO formation time, during NO2 adsorption, is rather controlled by TiO2 surface coverage than NO2 inlet concentration; similarly, adsorption time i.e. surface coverage, significantly modifies the nature of adsorbed species on TiO2 surface. (10.1016/j.apcatb.2013.04.073)
  DOI : 10.1016/j.apcatb.2013.04.073
• Radio frequency current-voltage probe for impedance and power measurements in multi-frequency unmatched loads
  
  • Lafleur Trevor
  • Delattre Pierre-Alexandre
  • Johnson E.V.
  • Booth Jean-Paul
  • Diné Sébastien
  Review of Scientific Instruments, American Institute of Physics, 2013, 84, pp.015001. A broad-band, inline current-voltage probe, with a characteristic impedance of 50 &#937;, is presented for the measurement of voltage and current waveforms, impedance, and power in rf systems. The probe, which uses capacitive and inductive sensors to determine the voltage and current, respectively, can be used for the measurement of single or multi-frequency signals into both matched and unmatched loads, over a frequency range of about 1100 MHz. The probe calibration and impedance/power measurement technique are described in detail, and the calibrated probe results are compared with those obtained from a vector network analyzer and other commercial power meters. Use of the probe is demonstrated with the measurement of power into an unmatched capacitively coupled plasma excited by multi-frequency tailored voltage waveforms. (10.1063/1.4773540)
  DOI : 10.1063/1.4773540
• Frequency dependence of the electrical asymmetry effect in dual-frequency capacitively coupled discharges
  
  • Booth Jean-Paul
  • Lafleur Trevor
  Applied Physics Letters, American Institute of Physics, 2013, 102, pp.154104. Using experimental measurements complemented with particle-in-cell (PIC) simulations, we demonstrate a reduction in the electrical asymmetry effect in capacitively coupled discharges for low excitation frequencies (0.8&#8201;MHz&#8201;<&#8201;f<10&#8201;MHz). These results confirm PIC simulation predictions made by [I. Korolov, Z. Donkó, U. Czarnetzki, and J. Schulze, J. Phys. D: Appl. Phys. 45, 465205 (2012)], where this effect was investigated for dual-frequency discharges in which the driving frequencies are phase-shifted harmonics. Because the reduction in electrical asymmetry is a sensitive function of the secondary electron emission coefficient, we are able to non-invasively estimate this coefficient as 0.035 for argon ions incident on aluminium electrodes. (10.1063/1.4802241)
  DOI : 10.1063/1.4802241
• Modes of underwater discharge propagation in a series of nanosecond successive pulses
  
  • Marinov Ilya
  • Guaitella Olivier
  • Rousseau Antoine
  • Starikovskaia Svetlana
  Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.464013. Initiation and development of nanosecond electric discharges in deionized water was studied by time-resolved shadowgraphy and emission imaging. Pulses of 410 kV in amplitude, 5 ns rise time and 30 ns duration were applied to a high-voltage (HV) pin-like electrode with the diameter of the pin tip about 2&#956;m. Two distinct bush-like and tree-like modes of the discharge propagation were observed in the same conditions already at the rising slope of HV pulse. Both the modes are supersonic. The probability of finding one of them depends on applied voltage. Bush-mode propagates at 4 kms&#8722;1 at the initial stage; the deposited energy is less than 0.05 mJ. For the tree-like mode, propagation velocity, number of branches and deposited energy show well-prononced dependence on applied voltage. It is suggested that the bush-like discharge ignites in the gaseous cavity, whereas the tree-like discharge propagates in bulk liquid. The role of electrostriciton in the initiation and propagation of two modes is discussed, and comparison with microsecond discharges is given. Transition from bush-like discharge to tree-like mode may occur in successive positive pulse coming 500 ns after initial pulse. (10.1088/0022-3727/46/46/464013)
  DOI : 10.1088/0022-3727/46/46/464013
• Cluster Observations of Ion-Scale Magnetic Structures and their Coupling with Whistler Waves During the August 17th 2003 Substorm Event
  
  • Tenerani Anna
  • Le Contel Olivier
  • Califano F.
  • Robert Patrick
  • Fontaine Dominique
  • Cornilleau-Wehrlin Nicole
  • Sauvaud J.-A.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118, pp.6072-6089. We provide evidence of the simultaneous occurrence of large-amplitude, quasi-parallel whistler mode waves and ion-scale magnetic structures, which have been observed by the Cluster spacecraft in the plasma sheet at 17 Earth radii, during a substorm event. It is shown that the magnetic structures are characterized by both a magnetic field strength minimum and a density hump and that they propagate in a direction quasi-perpendicular to the average magnetic field. The observed whistler mode waves are efficiently ducted by the inhomogeneity associated with such ion-scale magnetic structures. The large amplitude of the confined whistler waves suggests that electron precipitations could be enhanced locally via strong pitch angle scattering. Furthermore, electron distribution functions indicate that a strong parallel heating of electrons occurs within these ion-scale structures. This study provides new insights on the possible multiscale coupling of plasma dynamics during the substorm expansion, on the basis of the whistler mode wave trapping by coherent ion-scale structures. (10.1002/jgra.50562)
  DOI : 10.1002/jgra.50562
• Study of the Equatorial Ionosphere in the research network GIRGEA
  
  • Amory-Mazaudier Christine
  • Fleury Rolland
  • Ouattara Frédéric Martial
  • Zerbo J.-L.
  • Pham Hong Thi Thu
  • Shimeis Amira
  • Zoundi C.
  • Fathy Ibrahim
  • Le Huy Minh
  • Mahrous A. M.
  , 2013.
• Propagation of plasma bullets in helium within a dielectric capillary - influence of the interaction with surfaces
  
  • Dang van Sung Mussard Marguerite
  • Guaitella Olivier
  • Rousseau Antoine
  Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.302001. This paper reports an experimental study on the propagation of an ionization wave inside a thin capillary, called plasma bullet. A low-frequency sinusoidal voltage is applied and several bullets are emitted during each cycle. The delay between two successive discharges is short enough so the propagation of one bullet is influenced by the charges deposited on surfaces by the previous one. It was shown that the propagation length increases during the cycle. An interesting result is that a discontinuity during the propagation of a bullet has been clearly pointed out. When it crosses the discontinuity, the bullet has been shown to increase its light emission and its propagation velocity. It was explained by a transition between regions of different potential, due to charges deposited by the previous bullets. (10.1088/0022-3727/46/30/302001)
  DOI : 10.1088/0022-3727/46/30/302001
• Langmuir probe analysis of highly electronegative plasmas
  
  • Bredin Jérôme
  • Chabert Pascal
  • Aanesland Ane
  Applied Physics Letters, American Institute of Physics, 2013, 102, pp.154107. A Langmuir probe analysis of highly electronegative plasmas is proposed. Analytical models are used to fit the IV-characteristics and their second derivatives above and below the plasma potential. Ion and electron densities are obtained for &#945; (negative ion to electron density ratio) up to 3000, and the temperature of negative and positive ions is obtained for &#945; ranging from 100 to 3000. The transport across a localized magnetic barrier is studied using this technique. It is shown that an ion-ion (electron free) plasma is formed downstream from the barrier at the highest magnetic field. (10.1063/1.4802252)
  DOI : 10.1063/1.4802252
• Reduced electron temperature in a magnetized inductively-coupled plasma with internal coil
  
  • Arancibia Monreal J.
  • Chabert Pascal
  • Godyak V.
  Physics of Plasmas, American Institute of Physics, 2013, 20, pp.103504. The effect of magnetic filtering on the electron energy distribution function is studied in an inductive discharge with internal coil coupling. The coil is placed inside the plasma and driven by a low-frequency power supply (5.8&#8201;MHz) which leads to a very high power transfer efficiency. A permanent dipole magnet may be placed inside the internal coil to produce a static magnetic field around 100 Gauss. The coil and the matching system are designed to minimize the capacitive coupling to the plasma. Capacitive coupling is quantified by measuring the radiofrequency (rf) plasma potential with a capacitive probe. Without the permanent magnet, the rf plasma potential is significantly smaller than the electron temperature. When the magnet is present, the rf plasma potential increases. The electron energy distribution function is measured as a function of space with and without the permanent magnet. When the magnet is present, electrons are cooled down to low temperature in the downstream region. This region of low electron temperature may be useful for plasma processing applications, as well as for efficient negative ion production. (10.1063/1.4825135)
  DOI : 10.1063/1.4825135
• Scaling of the electron dissipation range of solar wind turbulence
  
  • Sahraoui Fouad
  • Huang S. Y.
  • Belmont Gérard
  • Goldstein M. L.
  • Retinò Alessandro
  • Robert Patrick
  • de Patoul Judith
  The Astrophysical Journal, American Astronomical Society, 2013, 777 (1), pp.15. Electron scale solar wind (SW) turbulence has attracted great interest in recent years. Considerable evidence exists that the turbulence is not fully dissipated near the proton scale, but continues cascading down to electron scales. However, the scaling of the magnetic energy spectra as well as the nature of the plasma modes involved at those small scales are still not fully determined. Here we survey 10 yr of the Cluster STAFF search-coil magnetometer waveforms measured in the SW and perform a statistical study of the magnetic energy spectra in the frequency range [1, 180] Hz. We found that 75% of the analyzed spectra exhibit breakpoints near the electron gyroscale &#961; e , followed by steeper power-law-like spectra. We show that the scaling below the electron breakpoint cannot be determined unambiguously due to instrumental limitations that we discuss in detail. We compare our results to those reported in other studies and discuss their implications for the physical mechanisms involved and for theoretical modeling of energy dissipation in the SW. (10.1088/0004-637X/777/1/15)
  DOI : 10.1088/0004-637X/777/1/15
• The relation between reconnected flux, the parallel electric field, and the reconnection rate in a three-dimensional kinetic simulation of magnetic reconnection
  
  • Wendel D. E.
  • Olson D. K.
  • Hesse Michael
  • Aunai Nicolas
  • Kuznetsova M. M.
  • Karimabadi H.
  • Daughton W.
  • Adrian M. L.
  Physics of Plasmas, American Institute of Physics, 2013, 20, pp.2105. We investigate the distribution of parallel electric fields and their relationship to the location and rate of magnetic reconnection in a large particle-in-cell simulation of 3D turbulent magnetic reconnection with open boundary conditions. The simulation's guide field geometry inhibits the formation of simple topological features such as null points. Therefore, we derive the location of potential changes in magnetic connectivity by finding the field lines that experience a large relative change between their endpoints, i.e., the quasi-separatrix layer. We find a good correspondence between the locus of changes in magnetic connectivity or the quasi-separatrix layer and the map of large gradients in the integrated parallel electric field (or quasi-potential). Furthermore, we investigate the distribution of the parallel electric field along the reconnecting field lines. We find the reconnection rate is controlled by only the low-amplitude, zeroth and first-order trends in the parallel electric field while the contribution from fluctuations of the parallel electric field, such as electron holes, is negligible. The results impact the determination of reconnection sites and reconnection rates in models and in situ spacecraft observations of 3D turbulent reconnection. It is difficult through direct observation to isolate the loci of the reconnection parallel electric field amidst the large amplitude fluctuations. However, we demonstrate that a positive slope of the running sum of the parallel electric field along the field line as a function of field line length indicates where reconnection is occurring along the field line. (10.1063/1.4833675)
  DOI : 10.1063/1.4833675
• Aspects of collisionless magnetic reconnection in asymmetric systems
  
  • Hesse Michael
  • Aunai Nicolas
  • Zenitani Seiji
  • Kuznetsova M. M.
  • Birn Joachim
  Physics of Plasmas, American Institute of Physics, 2013, 20, pp.1210. Asymmetric reconnection is being investigated by means of particle-in-cell simulations. The research has two foci: the direction of the reconnection line in configurations with nonvanishing magnetic fields; and the question why reconnection can be faster if a guide field is added to an otherwise unchanged asymmetric configuration. We find that reconnection prefers a direction, which maximizes the available magnetic energy, and show that this direction coincides with the bisection of the angle between the asymptotic magnetic fields. Regarding the difference in reconnection rates between planar and guide field models, we demonstrate that a guide field can provide essential confinement for particles in the reconnection region, which the weaker magnetic field in one of the inflow directions cannot necessarily provide. (10.1063/1.4811467)
  DOI : 10.1063/1.4811467
• CLUSTER STAFF search coils magnetometer calibration - comparisons with FGM
  
  • Robert P.
  • Cornilleau-Wehrlin Nicole
  • Piberne Rodrigue
  • de Conchy Yvonne
  • Lacombe Catherine
  • Bouzid V.
  • Grison B.
  • Alison Dominique
  • Canu Patrick
  , 2013, pp.679-751. The main part of Cluster Spatio Temporal Analysis of Field Fluctuations (STAFF) experiment consists of triaxial search coils allowing the measurements of the three magnetic components of the waves from 0.1 Hz up to 4 kHz. Two sets of data are produced, one by a module to filter and transmit the corresponding waveform up to either 10 or 180 Hz (STAFF-SC) and the second by an onboard Spectrum Analyser (STAFF-SA) to compute the elements of the spectral matrix for five components of the waves, 3 × B and 2 × E (from EFW experiment) in the frequency range 8 Hz to 4 kHz. In order to understand the way the output signal of the search coils are calibrated, the transfer functions of the different parts of the instrument are described as well as the way to transform telemetry data into physical units, across various coordinate systems from the spinning sensors to a fixed and known frame. The instrument sensitivity is discussed. Cross-calibration inside STAFF (SC and SA) is presented. Results of cross-calibration between the STAFF search coils and the Cluster Flux Gate Magnetometer (FGM) data are discussed. It is shown that these cross-calibrations lead to an agreement between both data sets at low frequency within a 2% error. By means of statistics done over 10 yr, it is shown that the functionalities and characteristics of both instruments have not changed during this period. (10.5194/gid-3-679-2013)
  DOI : 10.5194/gid-3-679-2013
• Anomalous k&#8869;-8/3 Spectrum in Electron Magnetohydrodynamic Turbulence
  
  • Meyrand Romain
  • Galtier Sébastien
  Physical Review Letters, American Physical Society, 2013, 111, pp.264501. Electron magnetohydrodynamic turbulence is investigated under the presence of a relatively strong external magnetic field b<SUB>0</SUB>e<SUB>||</SUB> and through three-dimensional direct numerical simulations. Our study reveals the emergence of a k<SUB>&#8869;</SUB><SUP>-8/3</SUP> scaling for the magnetic energy spectrum at scales k<SUB>||D<=k<SUB>&#8869;</SUB><SUP><=k</SUP> &#8869;D, where k||D and k<SUB>&#8869;</SUB><SUP>D</SUP> are, respectively, the typical largest dissipative scales along and transverse to the b0</SUB> direction. Unlike standard magnetohydrodynamic, this turbulence regime is characterized by filaments of electric currents parallel to b<SUB>0</SUB>. The anomalous scaling is in agreement with a heuristic model in which the transfer in the parallel direction is negligible. Implications for solar wind turbulence are discussed. (10.1103/PhysRevLett.111.264501)
  DOI : 10.1103/PhysRevLett.111.264501
• Characteristics of the Poynting flux and wave normal vectors of whistler-mode waves observed on THEMIS
  
  • Li W.
  • Bortnik J.
  • Thorne R. M.
  • Cully C. M.
  • Chen Lin
  • Angelopoulos V.
  • Nishimura Y.
  • Tao J. B.
  • Bonnell J. W.
  • Le Contel Olivier
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118 (4), pp.1461-1471. The characteristics of the Poynting flux and wave normal vectors of whistler-mode waves outside the plasmapause are investigated for the lower (0.1-0.5 f<SUB>ce</SUB>) and upper bands (0.5-0.8 f<SUB>ce</SUB>), where f<SUB>ce</SUB> is the equatorial electron cyclotron frequency. To analyze the wave properties, we utilized high-resolution waveform data from multiple THEMIS spacecraft in the near-equatorial magnetosphere from June 2008 to November 2012. Full measurements of the wave electric and magnetic fields are used to calculate the Poynting fluxes and construct the wave normal vectors, which are then used to calculate the polar and azimuthal angles with respect to the background magnetic field. Statistical results show that the majority of whistler-mode waves propagate away from the magnetic equator, suggesting that the major source region is very close to the equator. The lower band wave normal angle distribution shows a major peak close to the field line direction and a secondary peak near the resonance cone. In contrast, the wave normal distribution of upper band waves exhibits a broad distribution between 0° and 60° with the largest probability at ~0°. The azimuthal component of the wave normal vector predominantly points radially outward for both lower and upper band waves, but a tendency for azimuthal propagation is observed for lower band waves in the day and dusk sectors probably due to pronounced azimuthal density gradients in the afternoon sector. Our statistical results provide crucial information on the Poynting fluxes and wave normal vectors of whistler-mode waves, which play a significant role in radiation belt electron dynamics. (10.1002/jgra.50176)
  DOI : 10.1002/jgra.50176
• EMIC triggered chorus emissions in Cluster data
  
  • Grison B.
  • Santolík O.
  • Cornilleau-Wehrlin Nicole
  • Masson A.
  • Engebretson M. J.
  • Pickett J. S.
  • Omura Y.
  • Robert Patrick
  • Nomura R.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118 (3), pp.1159-1169. Electromagnetic ion cyclotron (EMIC) triggered chorus emissions have recently been a subject of several experimental, theoretical and simulation case studies, noting their similarities with whistler-mode chorus. We perform a survey of 8 years of Cluster data in order to increase the database of EMIC triggered emissions. The results of this is that EMIC triggered emissions have been unambiguously observed for only three different days. These three events are studied in detail. All cases have been observed at the plasmapause between 22 and 24 magnetic local time (MLT) and between&#8201;&#8722;&#8201;15&#8728; and 15&#8728; magnetic latitude (&#955;m). Triggered emissions are also observed for the first time below the local He gyrofrequency math formula. The number of events is too low to produce statistical results, nevertheless we point out a variety of common properties of those waves. The rising tones have a high level of coherence and the waves propagate away from the equatorial region. The propagation angle and degree of polarization are related to the distance from the equator, whereas the slope and the frequency extent vary from one event to the other. From the various spacecraft separations, we determine that the triggering process is a localized phenomenon in space and time. However, we are unable to determine the occurrence rates of these waves. Small frequency extent rising tones are more common than large ones. The newly reported EMIC triggered events are generally observed during periods of large AE index values and in time periods close to solar maximum. (10.1002/jgra.50178)
  DOI : 10.1002/jgra.50178
• Quasiperiodic emissions observed by the Cluster spacecraft and their association with ULF magnetic pulsations
  
  • Němec F
  • Santolík O
  • Pickett J.S.
  • Parrot Michel
  • Cornilleau-Wehrlin Nicole
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118, pp.4210–4220. [1] Quasiperiodic (QP) emissions are electromagnetic waves at frequencies of about 0.5–4 kHz characterized by a periodic time modulation of the wave intensity, with a typical modulation period on the order of minutes. We present results of a survey of QP emissions observed by the Wide-Band Data (WBD) instruments on board the Cluster spacecraft. All WBD data measured in the appropriate frequency range during the first 10 years of operation (2001–2010) at radial distances lower than 10 R E were visually inspected for the presence of QP emissions, resulting in 21 positively identified events. These are systematically analyzed, and their frequency ranges and modulation periods are determined. Moreover, a detailed wave analysis has been done for the events that were strong enough to be seen in low-resolution Spatio-Temporal Analysis of Field Fluctuations-Spectrum Analyzer data. Wave vectors are found to be nearly field-aligned in the equatorial region, but they become oblique at larger geomagnetic latitudes. This is consistent with a hypothesis of unducted propagation. ULF magnetic field pulsations were detected at the same time as QP emissions in 4 out of the 21 events. They were polarized in the plane perpendicular to the ambient magnetic field, and their frequencies roughly corresponded to the modulation period of the QP events. Citation: Němec , F., O. Santolík, J. S. Pickett, M. Parrot, and N. Cornilleau-Wehrlin (2013), Quasiperiodic emissions observed by the Cluster spacecraft and their association with ULF magnetic pulsations, (10.1002/jgra.50406)
  DOI : 10.1002/jgra.50406
• Conjugate observations of quasi-periodic emissions by Cluster and DEMETER spacecraft
  
  • Němec F.
  • Santolík O.
  • Parrot Michel
  • Pickett J. S.
  • Hayosh M.
  • Cornilleau-Wehrlin Nicole
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118 (1), pp.198–208. Quasi-periodic (QP) emissions are electromagnetic emissions at frequencies of about 0.5-4 kHz that are characterized by a periodic time modulation of the wave intensity. Typical periods of this modulation are on the order of minutes. We present a case study of a large-scale long-lasting QP event observed simultaneously on board the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) and the Cluster spacecraft. The measurements by the Wide-Band Data instrument on board the Cluster spacecraft enabled us to obtain high-resolution frequency-time spectrograms of the event close to the equatorial region over a large range of radial distances, while the measurements by the STAFF-SA instrument allowed us to perform a detailed wave analysis. Conjugate observations by the DEMETER spacecraft have been used to estimate the spatial and temporal extent of the emissions. The analyzed QP event lasted as long as 5 h and it spanned over the L-shells from about 1.5 to 5.5. Simultaneous observations of the same event by DEMETER and Cluster show that the same QP modulation of the wave intensity is observed at the same time at very different locations in the inner magnetosphere. ULF magnetic field fluctuations with a period roughly comparable to, but somewhat larger than the period of the QP modulation were detected by the fluxgate magnetometers instrument on board the Cluster spacecraft near the equatorial region, suggesting these are likely to be related to the QP generation. Results of a detailed wave analysis show that the QP emissions detected by Cluster propagate unducted, with oblique wave normal angles at higher geomagnetic latitudes. (10.1029/2012JA018380)
  DOI : 10.1029/2012JA018380