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  • Journal article
    Dunlop MW, Yang J-Y, Yang Y-Y, Xiong C, Lühr H, Bogdanova YV, Shen C, Olsen N, Zhang Q-H, Cao J-B, Fu H-S, Liu W-L, Carr CM, Ritter P, Masson A, Haagmans Ret al., 2015,

    Simultaneous field-aligned currents at Swarm and Cluster satellites

    , Geophysical Research Letters, Vol: 42, Pages: 3683-3691, ISSN: 1944-8007

    We show for the first time, with direct, multispacecraft calculations of electric current density, and other methods, matched signatures of field-aligned currents (FACs) sampled simultaneously near the ionosphere at low (~500 km altitude) orbit and in the magnetosphere at medium (~2.5 RE altitude) orbits using a particular Swarm and Cluster conjunction. The Cluster signatures are interpreted and ordered through joint mapping of the ground/magnetospheric footprints and estimation of the auroral zone boundaries (taken as indication of the boundaries of Region 1 and Region 2 currents). We find clear evidence of both small-scale and large-scale FACs and clear matching of the behavior and structure of the large-scale currents at both Cluster and Swarm. The methodology is made possible through the joint operations of Cluster and Swarm, which contain, in the first several months of Swarm operations, a number of close three-spacecraft configurations.
  • Journal article
    Carr CM, Erikksson S, Lapenta G, Newman DL, Phan TD, Gosling JT, Lavraud B, Khotyaintsev YV, Markidis S, Goldman MVet al., 2015,

    On Multiple Reconnection X-lines and Tripolar Perturbations of Strong Guide Magnetic Fields

    , The Astrophysical Journal, Vol: 805, ISSN: 0004-637X

    We report new multi-spacecraft Cluster observations of tripolar guide magnetic field perturbations at a solar windreconnection exhaust in the presence of a guide field BM which is almost four times as strong as the reversing fieldBL. The novel tripolar field consists of two narrow regions of depressed BM, with an observed 7%–14% ΔBMmagnitude relative to the external field, which are found adjacent to a wide region of enhanced BM within theexhaust. A stronger reversing field is associated with each BM depression. A kinetic reconnection simulation forrealistic solar wind conditions and the observed strong guide field reveals that tripolar magnetic fields preferentiallyform across current sheets in the presence of multiple X-lines as magnetic islands approach one another and mergeinto fewer and larger islands. The simulated ΔBM/ΔXN over the normal width ΔXN between a BM minimum andthe edge of the external region agree with the normalized values observed by Cluster. We propose that a tripolarguide field perturbation may be used to identify candidate regions containing multiple X-lines and interactingmagnetic islands at individual solar wind current sheets with a strong guide field.
  • Journal article
    Eastwood JP, Hietala H, Toth G, Phan TD, Fujimoto Met al., 2015,

    What Controls the Structure and Dynamics of Earth's Magnetosphere?

    , SPACE SCIENCE REVIEWS, Vol: 188, Pages: 251-286, ISSN: 0038-6308
  • Journal article
    Balogh A, Bykov A, Eastwood J, Kaastra Jet al., 2015,

    Multi-scale Structure Formation and Dynamics in Cosmic Plasmas

    , SPACE SCIENCE REVIEWS, Vol: 188, Pages: 1-2, ISSN: 0038-6308
  • Journal article
    Czaja A, Marshall J, 2015,

    Why is there net surface heating over the Antarctic Circumpolar Current?

    , OCEAN DYNAMICS, Vol: 65, Pages: 751-760, ISSN: 1616-7341
  • Journal article
    Hu F, Sun J, Brindley HE, Liang X, Lucyszyn Set al., 2015,

    Systems Analysis for Thermal Infrared 'THz Torch' Applications

    , JOURNAL OF INFRARED MILLIMETER AND TERAHERTZ WAVES, Vol: 36, Pages: 474-495, ISSN: 1866-6892
  • Journal article
    Nazarenko L, Schmidt GA, Miller RL, Tausnev N, Kelley M, Ruedy R, Russell GL, Aleinov I, Bauer M, Bauer S, Bleck R, Canuto V, Cheng Y, Clune TL, Del Genio AD, Faluvegi G, Hansen JE, Healy RJ, Kiang NY, Koch D, Lacis AA, LeGrande AN, Lerner J, Lo KK, Menon S, Oinas V, Perlwitz J, Puma MJ, Rind D, Romanou A, Sato M, Shindell DT, Sun S, Tsigaridis K, Unger N, Voulgarakis A, Yao M-S, Zhang Jet al., 2015,

    Future climate change under RCP emission scenarios with GISS ModelE2

    , JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS, Vol: 7, Pages: 244-267
  • Journal article
    Brindley H, Bantges R, Russell J, Murray J, Dancel C, Belotti C, Harries Jet al., 2015,

    Spectral Signatures of Earth's Climate Variability over 5 Years from IASI

    , JOURNAL OF CLIMATE, Vol: 28, Pages: 1649-1660, ISSN: 0894-8755
  • Journal article
    Eastwood JP, Goldman MV, Hietala H, Newman DL, Mistry R, Lapenta Get al., 2015,

    Ion reflection and acceleration near magnetotail dipolarization fronts associated with magnetic reconnection

    , Journal of Geophysical Research: Space Physics, Vol: 120, Pages: 511-525, ISSN: 2169-9402

    Dipolarization fronts (DFs) are often associated with the leading edge of earthward bursty bulk flows in the magnetotail plasma sheet. Here multispacecraft Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations are used to show that a spatially limited region of counterpropagating ion beams, whose existence is not evident in either the plasma moments or the electric field, is observed on the low-density side of DFs. The THEMIS magnetic field data are used to establish appropriate comparison cuts through a particle-in-cell simulation of reconnection, and very good agreement is found between the observed and simulated ion distributions on both sides of the DF. Self-consistent back tracing shows that the ion beams originate from the thermal component of the preexisting high-density plasma into which the DF is propagating; they do not originate from the inflow region in the traditional sense. Forward tracing shows that some of these ions can subsequently overtake the DF and pass back into the high-density preexisting plasma sheet with an order-of-magnitude increase in energy; this process is distinct from other ion reflection processes that occur directly at the DF. The interaction of the reconnection jet with the preexisting plasma sheet therefore occurs over a macroscopic region, rather than simply being limited to the thin DF interface. A more general consequence of this study is the conclusion that reconnection jets are not simply fed by plasma inflow across the separatrices but are also fed by plasma from the region into which the jet is propagating; the implications of this finding are discussed.
  • Journal article
    Nilsson H, Wieser GS, Behar E, Wedlund CS, Gunell H, Yamauchi M, Lundin R, Barabash S, Wieser M, Carr C, Cupido E, Burch JL, Fedorov A, Sauvaud J-A, Koskinen H, Kallio E, Lebreton J-P, Eriksson A, Edberg N, Goldstein R, Henri P, Koenders C, Mokashi P, Nemeth Z, Richter I, Szego K, Volwerk M, Vallat C, Rubin Met al., 2015,

    Birth of a comet magnetosphere: A spring of water ions

    , Science, Vol: 347, ISSN: 0036-8075

    The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (~3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (<800 electron volts), produced upstream of Rosetta, and lower energy locally produced ions; we estimate the fluxes of both ion species and energetic neutral atoms.
  • Journal article
    O'Reilly CH, Czaja A, 2015,

    The response of the Pacific storm track and atmospheric circulation to Kuroshio Extension variability

    , Quarterly Journal of the Royal Meteorological Society, Vol: 141, Pages: 52-66, ISSN: 0035-9009

    An index of the Kuroshio Extension front strength is produced using a maximum covariance analysis between sea‐surface temperature (SST) and sea‐surface height (SSH) gradient observations, and composites of the atmospheric state are presented during its positive and negative phases using reanalysis data (1992–2011).It is found that when the Kuroshio Extension is less (more) meandering, with a stronger (weaker) SST front, the atmospheric heat transport by transient eddies is increased in the western (eastern) Pacific region, consistent with an increase (decrease) in low‐level baroclinicity. Analysis of the eddy–mean flow interaction shows that this zonal shift in heat transport forces anomalous barotropic flow in the Eastern Pacific, where blocking frequency is strongly influenced.The above relationships cannot be reconciled with the known response of the North Pacific storm track to remote forcing from the Tropical Pacific, nor can they be explained by the response of the ocean to atmospheric forcing via surface heat fluxes or winds. Rather, the zonal shift in the storm track highlighted here, and the associated changes in the large‐scale circulation, are interpreted as a response to the interannual variability of the Kuroshio Extension front.
  • Journal article
    Leitner S, Valavanoglou A, Brown P, Hagen C, Magnes W, Whiteside BJ, Carr CM, Delva M, Baumjohann Wet al., 2015,

    Design of the Magnetoresistive Magnetometer for ESA's SOSMAG Project

    , IEEE TRANSACTIONS ON MAGNETICS, Vol: 51, ISSN: 0018-9464
  • Journal article
    Eastwood JP, Kataria DO, McInnes CR, Barnes NC, Mulligan Pet al., 2015,

    Sunjammer

    , WEATHER, Vol: 70, Pages: 27-30, ISSN: 0043-1656
  • Journal article
    Klueser L, Banks JR, Martynenko D, Bergemann C, Brindley HE, Holzer-Popp Tet al., 2015,

    Information content of space-borne hyperspectral infrared observations with respect to mineral dust properties

    , REMOTE SENSING OF ENVIRONMENT, Vol: 156, Pages: 294-309, ISSN: 0034-4257
  • Journal article
    Forsyth C, Watt CEJ, Rae IJ, Fazakerley AN, Kalmoni NME, Freeman MP, Boakes PD, Nakamura R, Dandouras I, Kistler LM, Jackman CM, Coxon JC, Carr CMet al., 2014,

    Increases in plasma sheet temperature with solar wind driving during substorm growth phases

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 41, Pages: 8713-8721, ISSN: 0094-8276
  • Journal article
    Banks JR, Brindley HE, Hobby M, Marsham JHet al., 2014,

    The daytime cycle in dust aerosol direct radiative effects observed in the central Sahara during the Fennec campaign in June 2011

    , JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, Vol: 119, Pages: 13861-13876, ISSN: 2169-897X
  • Journal article
    Brown P, Whiteside BJ, Beek TJ, Fox P, Horbury TS, Oddy TM, Archer MO, Eastwood JP, Sanz-Hernndez D, Sample JG, Cupido E, O'Brien H, Carr CMet al., 2014,

    Space magnetometer based on an anisotropic magnetoresistive hybrid sensor

    , Review of Scientific Instruments, Vol: 85, ISSN: 1089-7623
  • Journal article
    Mistry R, Eastwood JP, Hietala H, 2014,

    Detection of small-scale folds at a solar wind reconnection exhaust

    , Journal of Geophysical Research: Space Physics, Vol: 120, Pages: 30-42, ISSN: 2169-9402

    Observations of reconnection in the solar wind over the last few years appear to indicate that the majority of large-scale reconnecting current sheets are roughly planar, and that reconnection itself is quasi-steady. Most studies of solar wind exhausts have used spacecraft with large separations and relatively low time cadence ion measurements. Here we present multipoint Cluster observations of a reconnection exhaust and the associated current sheet at ACE and Wind, enabling it to be studied on multiple length scales and at high time resolution. While analysis shows that on large scales the current sheet is planar, detailed measurements using the four closely spaced Cluster spacecraft show that the trailing edge of the reconnection jet is nonplanar with folds orthogonal to the reconnection plane, with length scales of approximately 230 ion inertial lengths. Our findings thus suggest that while solar wind current sheets undergoing reconnection may be planar on large scales, they may also exhibit complex smaller-scale structure. Such structure is difficult to observe and has rarely been detected because exhausts are rapidly convected past the spacecraft in a single cut; there is therefore a limited set of spacecraft trajectories through the exhaust which would allow the nonplanar features to be intercepted. We consider how such nonplanar reconnection current sheets can form and the processes which may have generated the 3-D structure that was observed.
  • Journal article
    Archer MO, Turner DL, Eastwood JP, Schwartz SJ, Horbury TSet al., 2014,

    Global impacts of a Foreshock Bubble: Magnetosheath, magnetopause and ground-based observations

    , Planetary and Space Science, Vol: 106, Pages: 56-66, ISSN: 1873-5088

    Using multipoint observations we show, for the first time, that Foreshock Bubbles (FBs) have a global impact on Earth׳s magnetosphere. We show that an FB, a transient kinetic phenomenon due to the interaction of backstreaming suprathermal ions with a discontinuity, modifies the total pressure upstream of the bow shock showing a decrease within the FB׳s core and sheath regions. Magnetosheath plasma is accelerated towards the intersection of the FB׳s current sheet with the bow shock resulting in fast, sunward, flows as well as outward motion of the magnetopause. Ground-based magnetometers also show signatures of this magnetopause motion simultaneously across at least 7 h of magnetic local time, corresponding to a distance of 21.5RE transverse to the Sun–Earth line along the magnetopause. These observed global impacts of the FB are in agreement with previous simulations and in stark contrast to the known localised, smaller scale effects of Hot Flow Anomalies (HFAs).
  • Journal article
    Hunt GJ, Cowley SWH, Provan G, Bunce EJ, Alexeev II, Belenkaya ES, Kalegaev VV, Dougherty MK, Coates AJet al., 2014,

    Field-aligned currents in Saturn's southern nightside magnetosphere: Subcorotation and planetary period oscillation components

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, ISSN: 2169-9380
  • Journal article
    Genestreti KJ, Fuselier SA, Goldstein J, Nagai T, Eastwood JPet al., 2014,

    The location and rate of occurrence of near-Earth magnetotail reconnection as observed by Cluster and Geotail

    , JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, Vol: 121, Pages: 98-109, ISSN: 1364-6826
  • Journal article
    Arridge CS, Achilleos N, Agarwal J, Agnor CB, Ambrosi R, Andre N, Badman SV, Baines K, Banfield D, Barthelemy M, Bisi MM, Blum J, Bocanegra-Bahamon T, Bonfond B, Bracken C, Brandt P, Briand C, Briois C, Brooks S, Castillo-Rogez J, Cavalie T, Christophe B, Coates AJ, Collinson G, Cooper JF, Costa-Sitja M, Courtin R, Daglis IA, De Pater I, Desai M, Dirkx D, Dougherty MK, Ebert RW, Filacchione G, Fletcher LN, Fortney J, Gerth I, Grassi D, Grodent D, Grun E, Gustin J, Hedman M, Helled R, Henri P, Hess S, Hillier JK, Hofstadter MH, Holme R, Horanyi M, Hospodarsky G, Hsu S, Irwin P, Jackman CM, Karatekin O, Kempf S, Khalisi E, Konstantinidis K, Kruger H, Kurth WS, Labrianidis C, Lainey V, Lamy LL, Laneuville M, Lucchesi D, Luntzer A, MacArthur J, Maier A, Masters A, McKenna-Lawlor S, Melin H, Milillo A, Moragas-Klostermeyer G, Morschhauser A, Moses JI, Mousis O, Nettelmann N, Neubauer FM, Nordheim T, Noyelles B, Orton GS, Owens M, Peron R, Plainaki C, Postberg F, Rambaux N, Retherford K, Reynaud S, Roussos E, Russell CT, Rymer A, Sallantin R, Sanchez-Lavega A, Santolik O, Saur J, Sayanagi K, Schenk P, Schubert J, Sergis N, Sittler EC, Smith A, Spahn F, Srama R, Stallard T, Sterken V, Sternovsky Z, Tiscareno M, Tobie G, Tosi F, Trieloff M, Turrini D, Turtle EP, Vinatier S, Wilson R, Zarkat Pet al., 2014,

    The science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets

    , PLANETARY AND SPACE SCIENCE, Vol: 104, Pages: 122-140, ISSN: 0032-0633
  • Journal article
    Nordheim TA, Jones GH, Roussos E, Leisner JS, Coates AJ, Kurth WS, Khurana KK, Krupp N, Dougherty MK, Waite JHet al., 2014,

    Detection of a strongly negative surface potential at Saturn's moon Hyperion

    , Geophysical Research Letters, Vol: 41, Pages: 7011-7018, ISSN: 1944-8007

    On 26 September 2005, Cassini conducted its only close targeted flyby of Saturn’s small, irregularlyshaped moon Hyperion. Approximately 6 min before the closest approach, the electron spectrometer (ELS),part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating fromthe direction of the moon’s surface. Plasma wave activity detected by the Radio and Plasma Wave instrumentsuggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and theMagnetospheric Imaging Instrument Low-Energy Magnetospheric Measurement System, indicating that themoon and the spacecraft were magnetically connected when the field-aligned electron population wasobserved. We show that this constitutes a remote detection of a strongly negative (~ 200 V) surface potentialon Hyperion, consistent with the predicted surface potential in regions near the solar terminator.
  • Journal article
    Phan TD, Drake JF, Shay MA, Gosling JT, Paschmann G, Eastwood JP, Oieroset M, Fujimoto M, Angelopoulos Vet al., 2014,

    Ion bulk heating in magnetic reconnection exhausts at Earth's magnetopause: Dependence on the inflow Alfven speed and magnetic shear angle

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 41, Pages: 7002-7010, ISSN: 0094-8276
  • Journal article
    Archer MO, Turner DL, Eastwood JP, Horbury TS, Schwartz SJet al., 2014,

    The role of pressure gradients in driving sunward magnetosheath flows and magnetopause motion

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, Pages: 8117-8125, ISSN: 2169-9380
  • Journal article
    Varsani A, Owen CJ, Fazakerley AN, Forsyth C, Walsh AP, Andre M, Dandouras I, Carr CMet al., 2014,

    Cluster observations of the substructure of a flux transfer event: analysis of high-time-resolution particle data

    , ANNALES GEOPHYSICAE, Vol: 32, Pages: 1093-1117, ISSN: 0992-7689
  • Journal article
    Newton B, Cowie S, Rijks D, Banks J, Brindley H, Marsham JHet al., 2014,

    SOLAR COOKING IN THE SAHEL

    , BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, Vol: 95, Pages: 1325-1328, ISSN: 0003-0007
  • Journal article
    Provan G, Lamy L, Cowley SWH, Dougherty MKet al., 2014,

    Planetary period oscillations in Saturn's magnetosphere: Comparison of magnetic oscillations and SKR modulations in the postequinox interval

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, ISSN: 2169-9380
  • Journal article
    Yang YY, Shen C, Zhang YC, Rong ZJ, Li X, Dunlop M, Ma YH, Liu ZX, Carr CM, Reme Het al., 2014,

    The force-free configuration of flux ropes in geomagnetotail: Cluster observations

    , Journal of Geophysical Research: Space Physics, Vol: 119, Pages: 6327-6341, ISSN: 2169-9402

    Unambiguous knowledge of magnetic field structure and the electric current distribution is critical for understanding the origin, evolution, and related dynamic properties of magnetic flux ropes (MFRs). In this paper, a survey of 13 MFRs in the Earth's magnetotail are conducted by Cluster multipoint analysis, so that their force-free feature, i.e., the kind of magnetic field structure satisfying J × B = 0, can be probed directly. It is showed that the selected flux ropes with the bipolar signature of the south-north magnetic field component generally lie near the equatorial plane, as expected, and that the magnetic field gradient is rather weak near the axis center, where the curvature radius is large. The current density (up to several tens of nA/m2) reaches their maximum values as the center is approached. It is found that the stronger the current density, the smaller the angles between the magnetic field and current in MFRs. The direct observations show that only quasi force-free structure is observed, and it tends to appear in the low plasma beta regime (in agreement with the theoretic results). The quasi force-free region is generally found to be embedded in the central portion of the MFRs, where the current is approximately field aligned and proportional to the strength of core field. It is shown that ~60% of surveyed MFRs can be globally approximated as force free. The force-free factor α is found to be nonconstantly varied through the quasi force-free MFR, suggesting that the force-free structure is nonlinear.
  • Journal article
    Reveret V, de la Broise X, Fermon C, Pannetier-Lecoeur M, Pigot C, Rodriguez L, Sauvageot J-L, Jin Y, Marnieros S, Bouchier D, Putzeys J, Long Y, Kiss C, Kiraly S, Barbera M, Lo Cicero U, Brown P, Carr C, Whiteside Bet al., 2014,

    CESAR: Cryogenic Electronics for Space Applications

    , JOURNAL OF LOW TEMPERATURE PHYSICS, Vol: 176, Pages: 446-452, ISSN: 0022-2291

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