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  PEACE Team Meeting 2010 Cluster and Double Star PEACE MSSL, 9th-11th March 2010
Workshop Abstracts The abstracts that have been submitted so far are below.
Chris Gurgiolo et al. Chris Gurgiolo, Mel Goldstein, Adolfo Vinas First Measurements of Plasma Vorticity in the Solar Wind: An Unexpected Source Direct measurements of electron vorticity in the solar wind has been carried out using data from the Cluster PEACE instrument. One unexpected result was the almost continuous presence of vorticity at different intensity levels. A simple model shows that this results from a cross coupling of the strahl and returned electron populations with the magnetic field. Changes in orientation in the local magnetic field results in corresponding changes in the velocity of the strahl and reflected populations. This results in deflections in the overall electron bulk velocity which appears as a vorticity. The presentation will consist of explaining the methodology used to derive the vorticity, showing the resultant computations and linking the computations to a simple model to demonstrate the proposed source. Chris Gurgiolo et al. Chris Gurgiolo, Mel Goldstein, Adolfo Vinas Direct Observations of the Formation of the Solar Wind Halo by Scattering of the Strahl It has been suggested by a number of authors that the solar wind halo is formed by the strahl. On numerous occasions we have observed in Phi/Theta plots of electrons at discrete energies a filament of particles connecting the strahl to the solar wind core. When the magnetic field is well off the nominal nominal solar wind flow direction such filaments are inconsistent any local forces and are probably the result of strong scattering. The obvious solution between the halo and strahl suggests that the strahl may be, at least in part, the source of the halo. Jiankui Shi et al. Inter-hemispheric asymmetry of dipole tilt angle effects on Cusps latitude location: Cluster observation J.K.Shi(1), T. L.Zhang(2), Z. X. Liu(1), M. Dunlop(3), E. Lucek(4), A. Fazakerley(5), H. Rème(6), I. Dandouras(6) (1) State Key Laboratory of Space Weather, CSSAR, Chinese Academy of Sciences, Beijing, China (2) Space Research Institute, Austrian Academy of Sciences, Graz, Austria (3) RAL, UK (4) Imperial College London, UK (5) MSSL, University College London, UK (6) CESR, Toulouse, France A data set of the Cluster cusp crossings over a 5-year period is studied for the inter-hemispheric comparison of the dipole tilt angle effect on the latitude of the mid-altitude cusp. The result shows that the dipole tilt angle has a clear control of the cusp latitudinal location. The northern cusp moves 0.065° ILAT for every increase 1° in the dipole tilt angle, while the southern cusp moves 0.048° ILAT for every 1° increase in the dipole tilt angle. This suggests an inter-hemispheric difference in the dependence of cusp latitudinal location on the dipole tilt angle. Robert Fear et al. Asymmetry in the bipolar signatures of flux transfer events Several conceptual models have been proposed for the formation of flux transfer events (FTEs), including models based on reconnection at a single reconnection line (X-line) and at multiple X-lines. Two-dimensional magnetohydrodynamic models have previously been used to simulate both scenarios and have found a tendency for FTEs generated by single X-line reconnection to exhibit an asymmetry in the bipolar Bn signature that is the major in situ signature of FTE structures, with the leading peak being substantially smaller in magnitude than the trailing peak. On the other hand, simulated FTEs generated by multiple X-line reconnection led to more symmetric signatures. We present a comparison of these simulation results with observations made at the Earth's magnetopause by the Cluster spacecraft, using a dataset of 213 FTEs which were observed by all four spacecraft in 2002/3. A tendency is found for the Bn signatures to be asymmetric, but with the leading peak stronger than the trailing peak -- opposite to the prediction made by the 2D models. We also compare the observations with the results of a more recent global MHD simulation and find similar trends to those observed by Cluster. Wayne Keith et al. Drift-corrected CIS Pitch Angle Data The current status of CIS ion data in the IDFS format will be discussed, both the original data and pitch angle sorted data including a prototype drift velocity correction. The IDFS Data will also be compared to the Cluster Active Archive files, along with a word about the readability of CAA files in SDDAS applications. Wayne Keith et al. Cluster and DMSP Conjunctions in the Cusps An ongoing difficulty with comparing particle datasets in the cusps at low DMSP altitudes with those of Cluster at mid and high altitudes is the very different nature of the measurements. The single upward look direction and quick cusp passage of DMSP requires that the pitch angle at higher altitudes be known accurately for comparison. Cluster Pitch angle data that is corrected for bulk velocity is now making it possible to have greater confidence in this ongoing work of mapping between cusp altitudes. Jan Soucek et al. Langmuir waves and electron distributions inside solar wind magnetic holes J. Soucek, C. Briand, A. Mangeney, J. S. Pickett Magnetic holes, solitary large amplitude depressions in the interplanetary magnetic field, are commonly observed in the solar wind. Some of these magnetic structures are accompanied by bursts of electrostatic waves close to the electron plasma frequency localized inside the magnetic holes. We present detailed analysis of the waves from STEREO (S/WAVES instrument) and Cluster (WBD and Whisper) and of the electron distributions observed by PEACE inside and outside the holes. We discuss possible mechanisms responsible for generation of these waves and instrumental constraints associated with Cluster observations. Iannis Dandouras et al. Inner magnetosphere science objectives: some previous achievements with Cluster and new targets for 2011 - 2012 The inner magnetosphere is a region where multiple particle populations coexist and interact (plasmasphere, ring current, exosphere), and where most of the energy is dissipated during magnetospheric storms and substorms. During the first years of Cluster operation the spacecraft orbit, with a 4 RE perigee, allowed an analysis of the westward ring current and the outer plasmasphere. The recent orbit evolution, with a substantial lowering of the perigee, gives access to the more "inner part" of the magnetosphere, opening the possibility to address some new key science objectives. Melvin Goldstein et al. Observing Magnetic Reconnection at Small-Scales and at Small Time Scales: NASA's Magnetospheric Multiscale Mission While Cluster has provided invaluable insights as to the location and physics of magnetic reconnection in and around Earth's magnetosphere, the best-documented properties from Cluster observations relate to the physics of ion (mainly, proton) motion. Many of the fundamental physical processes related to magnetic reconnection occur on the time scales of electron dynamics in a narrow region known as the electron diffusion region. Observing the physics of the electron diffusion region, especially the details of the electron distribution function, requires very fast simultaneous measurements by several spacecraft. NASA has embarked on a project, the Magnetospheric Multiscale Mission (MMS), to launch four identical spacecraft into an equatorial orbit. The instrumentation is designed specifically to address questions about the physics of magnetic reconnection. The spacecraft will have separations that can be as close as 10 km and time resolutions for determining the electron distribution function as fast as 30 ms and thermal proton distributions as fast as 150 ms. A full complement of magnetic and electric field sensors as well as high energy ion and composition measurements are part of the payload. I will review the components of the mission and its present status. Ondrej Santolik et al. Analysis of wave-Particle Interactions in a source region of Whistler-mode waves Wave-particle interactions can play a key role in the process of transfer of energy between different electron populations in the outer Van Allen radiation belt. We present a case study of wave-particle interactions in the equatorial source region of whistler-mode missions with characteristics similar to previously analyzed cases of whistler-mode chorus. We show that the injected electrons at lower energies can be responsible for a part of the waves that propagate obliquely at frequencies above one half of the electron cyclotron frequency. Our model of the trapped electrons at higher energies gives insufficient growth of the waves below one half of the electron cyclotron frequency and a nonlinear generation mechanism might be necessary to explain their presence. Claire Foullon et al. Signatures of Outflowing Transients Adjacent to the Heliospheric Current Sheet: Multi-spacecraft Observations C. Foullon (1,2) B. Lavraud (3,4) C.J. Owen (2) A.N. Fazakerley (2) and R.M. Skoug (5) (1) Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, U.K. (2) Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, U.K. (3) Centre d'Etudes Spatiales des Rayonnements (CESR), Universit\'e de Toulouse (UPS), Toulouse, France (4) Centre National de la Recherche Scientifique, UMR 5187, Toulouse, France (5) Los Alamos National Lab, MS D466, Los Alamos, NM 87545, U.S.A. The heliospheric current sheet (HCS) is a permanent solar wind feature, with well predicted Earth passages, but it can be structured and its main orientation can be highly distorted. We discuss two complementary sector crossings during the recent solar minimum, each one analysed by comparison of multi-point observations in the solar wind from spacecraft such as STEREO, ACE, Wind and Cluster. In one case, the field inversion structure can be assumed to be well preserved and close to planar on the scale of the magnetospheric cross-section, while in the other case we show an evolution across the Sun-Earth line of large field reversals adjacent to the HCS. However, both cases indicate the presence of field reversals in an away sector that is connected to the southern solar magnetic hemisphere but lies unexpectedly above a toward sector. Following the interpretation of the reversals as transient outflowing loops, associated initial flow deviations can be envisaged to account for the HCS deformations. The number and age of the transients channeled along the sector boundary may be gaged by the presence or lack of flow accelerations within the apparent layered structure and the extent of associated heat flux dropout. Bertalan Zieger et al. Multi-scale multi-point observations of dipolarization front near the flow-breaking region Bertalan Zieger, Rumi Nakamura, Alessandro Retino - Space Research Institute, Austrian Academy of Sciences Dipolarization (sudden enhancement in Bz) is one of the key signatures in the magnetotail indicating enhanced magnetic flux transported from the tail and/or change in the local/global configuration of the tail current sheet associated with substorms. During summer 2007, Cluster crossed the night-side plasma sheet closer to the Earth, inside of X~ -10 RE, which is an ideal location to study the flow-breaking region. We present an observation of a multiple dipolarization event on 2007-10-27 by examining the gradients in the fields at different scales as well as by analyzing the detailed particle signatures around the dipolarization front. Three topics will be mainly discussed in this talk (1) current sheet disturbances associated with dipolarization (2) electron acceleration around the flow-breaking region (3) shock-like signatures of the dipolarization front. Jeremy Mitchell et al. Electron Cross Talk Near the Bowshock and Electron Distribution Asymmetries Electron distributions in the magnetosheath display a number of far from equilibrium features. It has been suggested that one factor influencing these distributions may be the large distances separating locations at which electrons with different pitch angles must cross the bowshock in order to reach a given point in the magnetosheath. Due to differences in shock geometry at these distant crossing points electron heating at the shock, and therefore the observed electron velocity distributions, might be expected to vary with pitch angle. Here, we study electron distributions measured simultaneously by the Plasma Electron and Current Experiment (PEACE) on board the Cluster spacecraft and the Electrostatic Analyzer (ESA) on board THEMIS b during a time interval in which both the Cluster spacecraft and THEMIS b are (a) in the magnetosheath, (b) close to the bowshock, and (c) that the local magnetic field orientation makes it likely that electron trajectories may connect both spacecraft. We find that the velocity distributions of such electrons measured by each spacecraft display remarkable similarities. Trajectories of electrons arriving at each spacecraft are mapped back to the location at which they crossed the bowshock. The Rankine-Hugoniot relations are used to estimate the heating of electrons as a function of pitch angle and energy and compare with temperature asymmetries. Malcolm Dunlop et al. Multi-point perspectives of reconnection induced boundary layers M. W. Dunlop1,2,3, and the ISSI Themis-Cluster team [Q.-H Zhang(1), Y. Bogdanova(4), H. Hasegawa(5), K-H. Trattner(6), J. Wang(7), J-S. He(7), M. G. G. T. Taylor(8), J. Berchem(9), D. Constantinescu(10), A. N. Fazakerley(11), H. Frey(12), Z. Pu(5), C. Shen(6), J-K Shi(6), D. Sibeck(13), M. Volverk(14), P. Escoubet(8), J. Eastwood(15), B. Lavraud(16), J Wild(17)] (1) Space Science and Technology Department, RAL, Chilton, Didcot, Oxfordshire, OX11 0QX, UK (2) Center for Space Science and Applied Research, CAS, Beijing 100080, China (3) The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK. (4) Department of Physics, La Trobe University, Victoria, 3086, Australia. (5) Department of Space Plasma Physics, ISAS/JAXA, Japan. (6) Lockheed Martin, Palo Alto, California, USA. (7) School of Earth and Space Sciences, Peking University, Beijing 100871, China (8) ESA/ESTEC, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands (9) IGPP – UCLA, 3877 Slichter Hall, Los Angeles, CA 90095-1567, USA. (10) Institut für Geophysik und Meteorologie, TU-BS, D-38106 Braunschweig, Germany. (11) Mullard Space Science Laboratory, University College London, Dorking, Surrey, RH5 6NT, UK (12) Space Sciences Lab., University of California, 7 Gauss Way, Berkeley, CA 94720-7450, USA. (13) Code 674, NASA/GSFC, Greenbelt, MD 20771 USA. (14) Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz, Austria (15) UC Berkeley Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 USA (16) CESR–CNRS, 9 Ave. du Colonel Roche, 31028 Toulouse Cedex 4, France. (17) Space Plasma Environment and Radio Science group, Lancaster University, LA1 4WA, UK Cluster, Double Star and THEMIS close conjunctions at the magnetopause allow exploration of the conjugate response of the dayside magnetopause on the dawn/dusk flanks. In particular, during the April to July 2007 epoch, the array of four Cluster spacecraft, separated at large distances (10,000 km), were traversing the dawn-side magnetopause at high and low latitudes; the five THEMIS spacecraft were often in a 4+1 configuration, traversing the low latitude, dusk-side magnetosphere, and the Double star, TC-1 spacecraft was in an equatorial orbit between the local times of the THEMIS and Cluster orbits. This combination of 10 spacecraft provided simultaneous monitoring across a wide range of local times. The distribution and grouping of spacecraft allow multi-scale analysis of local phenomena operating on both flanks of the magnetopause, such as the occurrence and location of reconnection sites; extent and orientation of the X-line, and associated boundary layer properties. The near simultaneous encounters with reconnection sites are consistent with both a tilted X-line in the LLBL, together with anti-parallel sites extending to flank locations. Smaller scale configurations of Cluster and TC-1 have shown evidence (centering on repeated multi-point sampling of the ion diffusion region and associated null magnetic field) for high-latitude reconnection at a dayside location where the magnetic field orientations inside and outside the magnetopause lie close to anti-parallel, which is closely following a period of low latitude reconnection. Keith Yearby et al. The Cluster / Double Star particle correlators The particle correlator is a software application implemented within the Digital Wave Processor (DWP) instruments on the four Cluster spacecraft and on Double Star TC1. The correlator forms autocorrelation functions of time series of electron counts measured by the PEACE HEEA sensor. The objective of the correlator was the observation of the particle time structure associated with wave-particle interactions. Whilst the correlator technically functions to specifications, and there have been some results on the statistics of particle populations, particle time structures related to wave-particle interactions have not been observed. The instrument and data products will be described, together with a discussion of the reasons for the limited results obtained so far. Deirdre Wendel et al. Impact of Magnetic Draping, Convection, and Field Line Tying on Magnetopause Reconnection Under Northward IMF Deirdre E. Wendel (1), Patricia H. Reiff,(2) and Melvyn L. Goldstein(1) (1) NASA Goddard Space Flight Center, Greenbelt, MD (2) Rice University, Houston, TX We simulate a northward IMF cusp reconnection event at the Earth’s magnetopause using the OpenGGCM resistive MHD code. The ACE input data, solar wind parameters, and dipole tilt belong to a 2002 reconnection event observed by IMAGE and Cluster. Based on a fully three-dimensional global skeleton of separators, nulls, and parallel electric fields, we show how magnetic draping, convection, and ionospheric field line-tying play a role in producing a series of locally reconnecting nulls with flux ropes. The flux ropes lie in the cusp along the global separator line of symmetry. In 2D projection, the flux ropes have the appearance of a tearing mode with a series of ‘x’s’ and ‘o’s’ but bearing a kind of ‘guide field’ that exists only within the magnetopause. The reconnecting field lines in the string of flux ropes involve IMF and both open and closed Earth magnetic field lines. The observed magnetic geometry reproduces the findings of a superposed epoch and impact parameter study derived from the Cluster magnetometer data for the same event. The observed geometry has repercussions for spacecraft observations of cusp reconnection and for the imposed boundary conditions of reconnection simulations. Yuri Khotyaintsev et al. Cold plasma and magnetic reconnection at the magnetopause We report on detailed observations of magnetic reconnection and Flux Transfer Events at the magnetopause. We use observations from the fourCluster spacecraft at different simultaneous separations (about 35 km and 8000 km, i. e. the electron/ion and MHD scales, respectively). We confirm previous observations of cold (eV) plasma in reconnection regions, now using a method based on detection of the wake electric fieldcaused by cold ions streaming past a charged spacecraft. This method allows an estimate of the ion energy, and can reliably indicate changes at boundaries with high resolution. Multi-satellite observations are used to investigate the influence of the cold plasma on the reconnection process. We find that the potential drop accelerating plasma at the edges of a reconnection jet (in the separatrix region) depends on the ion temperature. A cold plasma gives a small potential drop (100 V) while in other events a hot keV plasma gives a larger (kV) potential difference. Yuri Khotyaintsev et al. Electrostatic solitary waves at reconnection site We present observation of electrostatic solitary waves (ESW) close to a reconnection site in the Earth's magnetotail. ESW are observed at time scales ~20 msec, and have amplitudes up to 50 mV/m. Interferometry analysis give speeds of the ESW about the local ion sound velocity (1500-2000 km/sec). The ESW are positive potential structures, i.e. electron holes. The amplitude of the potential change ranges from 50 to 300 V, which is at maximum one percent of electron thermal energy. Some of the ESW have a net potential jump up to 50 V. The ESW are observed inside a magnetic island (flux rope) which is formed by a coalescence of two smaller islands. ESW are observed in the rope center where there is a peak of the core magnetic field and a localized region of parallel electric field ~3 mV/m. This suggests that ESW are produced by the Bunemann instability. George Parks et al. Solar Wind Transport across Earth’s Bow Shock G. Parks(1), E. Lee(1), N. Lin(1), A. Teste(1), M. Wilber(1), I. Dandouras(2), H. RÈme(2), J. A. Sauvaud(2), S. Y. Fu(3), J. B. Cao(4), P. Canu(5) (1) Space Sciences Laboratory, University of California, Berkeley, CA (2) C. E. S. R., UniversitÈ Paul Sabatier, Toulouse, France (3) Earth and Space Sciences Department, Peking University, Beijing, China (4) Key Laboratory for Space Weather, Beijing, China (5) Laboratory for Plasma Physics, Ecole Polytechnique, France New observations are presented that shed light on how the SW changes across the bow shock. The cold solar wind (SW) ion beam is found to penetrate deep into the magnetosheath (MS) with temperature (T) change as small as ~1.5 eV, indicating very little thermalization occurs across the bow shock. Significant heat flux is also measured in the MS indicating MS is not in thermal equilibrium. Moreover, the flow speed in the MS is super-AlfvÈnic (AlfvÈn speed, VA= B (monm)-1/2) most of the time (~80-90%) with typical AlfvÈnic Mach number (MA = Vsw/VA) ~2-3. Entropy S and dS/dt abruptly increase at the magnetic ramp where intense electromagnetic waves are detected but dS/dt abruptly recovers in one data point (4s). We propose that the hotter MS plasma may be produced from heating of SW by waves generated by the unstable currents and plasma distributions. Rudy Frahm et al. Electron View of the Bow Shock: A Comparison Between Unmagnetized and Magnetized Planets (Mars, Venus, Earth) for Slow Shock Conditions The electron spectrum in the solar wind can penetrate the bow shock, showing a multiplicative energy signature in the magnetosheath. Similar effects are observed at Mars, Venus, and the Earth during slow shocks. Betatron acceleration will be examined and discussed as a possible mechanism for plasma transition from the solar wind into the magnetosheath. Yuri Khotyaintsev et al. EFW data in the CAA Dominique Fontaine et al. Analysis of outflowing electron beams correlated to broadband electrostatic emissions above the polar cap At a few Earth’s radii above the polar cap, CLUSTER observed electrons beams outflowing from the ionosphere and accelerated at weak energies, typically less than 100 eV, just above the photo-electron range. Their fluxes are both intense and variable, with large variations from one spin to the other one. We investigate here an excellent correlation of these outflowing beams with broadband electrostatic emissions at low frequencies, typically below 6 kHz. Broadband electrostatic noise has been observed in different regions of the magnetosphere, and waveform observations revealed the presence of electrostatic solitary waves on short time scales, a few milliseconds. However, in regions connected to the lobes, we did not get any conjunction with detailed wave data. If we turn to particle data, a careful analysis shows that these electron outflowing beams generally present a Maxwellian core with a more or less important supra-thermal tail. Events with several peaks, or without any defined peak, are also occasionally observed. Finally, this suggests that the involved wave-particle processes might occur on very short time-scales, of the order of the sampling rate, typically 100 ms. Arnaud Masson et al. Electron density estimation in the magnetotail: a multi-instrument approach A. Masson(1), O. SantolÌk(2), M.G.G.T. Taylor(1), C. P. Escoubet(1), A. N. Fazakerley(3), J. Pickett(4), A. _snes(1), X. ValliËres(5), H. Laakso(1) and J.-G. Trotignon(5) (1) ESA/ESTEC, D-SRE, Noordwijk, The Netherlands (2) Institute of Atmospheric Physics and Charles University, Faculty of Mathematics and Physics, Prague, Czech Republic (3) UCL, Mullard Space Science Laboratory, Surrey, UK (4) University of Iowa, Iowa, USA (5) LPCE/CNRS and UniversitÈ d’OrlÈans, OrlÈans, France Electron density is a key physical quantity to characterize any plasma medium. Its measurement is thus essential to understand the physical processes occurring in the environment of a magnetized planet, both macroscopic and microscopic. Since 2000, the four satellites of the European Space Agency (ESA) Cluster mission have been orbiting the Earth from 4 RE to 20 RE and probing the density with several types of instruments. In the magnetotail, this rare combination of experiments is particularly useful since the electron density and the temperature fluctuate over several decades. Two of these experiments, a relaxation sounder and a high-time resolution wide-band receiver, have rarely been flown together in the far tail. Such wave data can be used as a means to estimate the electron density via the identification of triggered resonances or the cutoffs of natural wave emissions, typically with an accuracy of a few percent. For the first time in the magnetotail (~ 20 RE), the Z-mode is proposed as the theoretical interpretation of the cutoff observed on spectrograms of wave measurements when the plasma frequency is greater than the electron gyrofrequency. We present examples found in the main regions of the magnetotail, comparing simultaneous density estimation from active and passive wave measurements with a particle instrument and calibrated spacecraft-to-probe potential difference data. With these examples, we illustrate the benefit of a multi-instrument approach for the estimation of the electron density in the magnetotail and the care that should be taken when determining the electron density from wave data. Colin Forsyth et al. Multi-spacecraft observations of auroral electron acceleration by Cluster C. Forsyth (1), A.N. Fazakerley (1), A.P. Walsh (1), K. Garza (1), C.J. Owen (1), I. Dandouras (2,3), K-H. Fornacon (4), E. Lucek (5), (1) UCL MSSL, Dorking UK, (2) Universite de Toulouse, France, (3) CNRS, Toulouse, France, (4) Technische Universitat Braunschweig, Germany, (5) Imperial College, London, UK During recent years the orbit of the Cluster spacecraft has evolved such that the spacecraft pass through the auroral acceleration region close to perigee during the dayside season. This presents the opportunity to make multi-spacecraft measurements of this region for the first time. We present a case study of an upward auroral current region observed by Cluster in December 2009. During this event, Cluster 1 and Cluster 3 were approximately located on the same magnetic field-line but separated by 1000 km. We show that the electron population was accelerated along the field-line between Cluster 1 and 3. Magnetic field observations confirm the presence of an upward current system. Based on these observations we estimate the size of the length of the acceleration region. Andrew Walsh et al. The Magnetotail Plasma Sheet Revisited: Cluster PEACE Statistics A. P. Walsh, A. N. Fazakerley, C. Forsyth, C. J. Owen Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey, RH5 6NT, UK. With the Cluster Active Archive now containing a large variety of high-quality, validated, data products, there is an opportunity to carry out large, multi-instrument statistical studies using Cluster measurements. We present first results from one such study: a survey of electron pitch angle distributions measured by Cluster PEACE during the 2002 tail season (~July - October). In total ~850,000 distributions have been examined in terms of magnetic field strength, auroral indices and other parameters. We find that the magnetotail plasma sheet is only routinely isotropic when |B| < 3nT, i.e. close to the neutral sheet. Outside this region a low-energy field-aligned population, presumably that identified by Asnes et al. (2008), was present at all levels of |B|. Significant electron fluxes were found to extend to higher |B| at higher AL/AE and exhibited energy-dispersed behaviour at the high |B| edge. The slope of this dispersion also changed with AL/AE. Matt Taylor Leading a discussion on future Cluster operations with audience participation I will show some plots of the Cluster spacecraft orbit in 2010-2012 and 2013-2014, in particular highlighting the constraints due to eclipses. 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