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  • Journal article
    Goldberg SJ, Ball GI, Allen BC, Schladow SG, Simpson AJ, Masoom H, Soong R, Graven HD, Aluwihare LIet al., 2015,

    Refractory dissolved organic nitrogen accumulation in high-elevation lakes

    , Nature Communications, Vol: 6, ISSN: 2041-1723

    The role of dissolved organic matter (DOM) as either a sink for inorganic nutrients or anadditional nutrient source is an often-neglected component of nutrient budgets in aquaticenvironments. Here, we examined the role of DOM in reactive nitrogen (N) storage in SierraNevada (California, USA) lakes where atmospheric deposition of N has shifted the lakestoward seasonal phosphorus (P)-limitation. Nuclear magnetic resonance (NMR) spectroscopyand isotope analyses performed on DOM isolated from Lake Tahoe reveal the accumulationof refractory proteinaceous material with a 100–200-year residence time. Incontrast, smaller lakes in the same watershed contain DOM with typical terrestrial characteristics,indicating that proteins in Lake Tahoe are autochthonously produced. These datasupport the role of DOM as a possible sink for reactive N in these lake ecosystems andidentify a potential role for DOM in affecting the inorganic nutrient stoichiometry of theseenvironments.
  • Book chapter
    Southwood DJ, 2015,

    Formation of Magnetotails: Fast and Slow Rotators Compared

    , Magnetotails in the Solar System, Editors: Keiling, Jackman, Publisher: John Wiley & Sons, Pages: 199-215, ISBN: 9781118842348
  • 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
    Bertucci C, Hamilton DC, Kurth WS, Hospodarsky G, Mitchell D, Sergis N, Edberg NJT, Dougherty MKet al., 2015,

    Titan's interaction with the supersonic solar wind

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 42, Pages: 193-200, ISSN: 0094-8276
  • Journal article
    Hassig M, Altwegg K, Balsiger H, Bar-Nun A, Berthelier JJ, Bieler A, Bochsler P, Briois C, Calmonte U, Combi M, De Keyser J, Eberhardt P, Fiethe B, Fuselier SA, Galand M, Gasc S, Gombosi TI, Hansen KC, Jackel A, Keller HU, Kopp E, Korth A, Kuehrt E, Le Roy L, Mall U, Marty B, Mousis O, Neefs E, Owen T, Reme H, Rubin M, Semon T, Tornow C, Tzou C-Y, Waite JH, Wurz Pet al., 2015,

    Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko

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

    Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface.
  • 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
    Vigren E, Galand M, Lavvas P, Eriksson AI, Wahlund J-Eet al., 2015,

    On the possibility of significant electron depletion due to nanograin charging in the coma of comet 67p/churyumov-gerasimenko near perihelion

    , Astrophysical Journal, Vol: 798, ISSN: 1538-4357
  • Book chapter
    Eastwood JP, Kiehas SA, 2015,

    Origin and Evolution of Plasmoids and Flux Ropes in the Magnetotails of Earth and Mars

    , Magnetotails in the Solar System, Pages: 269-287

    This chapter discusses the origin and evolution of plasmoids and flux ropes in Earth's magnetotail, providing an overview of author's current understanding based on recent multipoint and multimission data analysis. It also presents recent results concerning observations of flux ropes in the vicinity of Mars. Understanding the Mars solar wind interaction is very important for determining its atmospheric history, and recent discoveries show that magnetic reconnection-generated structures may play a significant role, particularly in the vicinity of the crustal field regions. The chapter briefly discusses some of the different terms used to describe reconnection-generated structures. It describes the production of islands, plasmoids, and secondary islands by antiparallel reconnection.
  • 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.
  • Book chapter
    Marino R, Baerenzung J, Mininni PD, Pouquet A, Rorai C, Rosenberg D, Stawarz Jet al., 2015,

    Helical turbulence in fluids and MHD

    , Pages: 549-559
  • Journal article
    Del Zanna L, Matteini L, Landi S, Verdini A, Velli Met al., 2015,

    Parametric decay of parallel and oblique Alfvén waves in the expanding solar wind

    , Journal of Plasma Physics, Vol: 81, ISSN: 0022-3778

    <jats:p>The long-term evolution of large-amplitude Alfvén waves propagating in the solar wind is investigated by performing two-dimensional MHD simulations within the expanding box model. The linear and nonlinear phases of the parametric decay instability are studied for both circularly polarized waves in parallel propagation and for arc-polarized waves in oblique propagation. The non-monochromatic case is also considered. In the oblique case, the direct excitation of daughter modes transverse to the local background field is found for the first time in an expanding environment, and this transverse cascade seems to be favored for monochromatic mother waves. The expansion effect reduces the instability growth rate, and it can even suppress its onset for the lowest frequency modes considered here, possibly explaining the persistence of these outgoing waves in the solar wind.</jats:p>
  • 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
    Masters A, 2015,

    Magnetic reconnection at Neptune's magnetopause

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 120, Pages: 479-493, ISSN: 2169-9380
  • 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
    Sparks N, Toumi R, 2015,

    Numerical Simulations of Daytime Temperature and Humidity Crossover Effects in London

    , BOUNDARY-LAYER METEOROLOGY, Vol: 154, Pages: 101-117, ISSN: 0006-8314
  • Book chapter
    Mitchell DG, Brandt PC, Carbary JF, Kurth WS, Krimigis SM, Paranicas C, Krupp N, Hamilton DC, Mauk BH, Hospodarsky GB, Dougherty MK, Pryor WRet al., 2015,

    Injection, Interchange, and Reconnection: Energetic Particle Observations in Saturn's Magnetosphere

    , MAGNETOTAILS IN THE SOLAR SYSTEM, Editors: Keiling, Jackman, Delamere, Publisher: BLACKWELL SCIENCE PUBL, Pages: 327-343, ISBN: 978-1-118-84234-8
  • Journal article
    Mushtaq S, Steers EBM, Whitby JA, Horvath P, Michler J, Pickering JCet al., 2015,

    A glow discharge time-of-flight mass spectrometry (GD-TOFMS) study of the 'hydrogen effect' using copper, iron and titanium cathodes

    , JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, Vol: 30, Pages: 1774-1781, ISSN: 0267-9477
  • Journal article
    Sitch S, Friedlingstein P, Gruber N, Jones SD, Murray-Tortarolo G, Ahlstrom A, Doney SC, Graven H, Heinze C, Huntingford C, Levis S, Levy PE, Lomas M, Poulter B, Viovy N, Zaehle S, Zeng N, Arneth A, Bonan G, Bopp L, Canadell JG, Chevallier F, Ciais P, Ellis R, Gloor M, Peylin P, Piao SL, Le Quere C, Smith B, Zhu Z, Myneni Ret al., 2015,

    Recent trends and drivers of regional sources and sinks of carbon dioxide

    , BIOGEOSCIENCES, Vol: 12, Pages: 653-679, ISSN: 1726-4170
  • Book chapter
    Cargill P, 2015,

    Magnetic Reconnection in the Solar Corona: Historical Perspective and Modern Thinking

    , MAGNETOSPHERIC PLASMA PHYSICS: THE IMPACT OF JIM DUNGEY'S RESEARCH, Editors: Southwood, Cowley, Mitton, Publisher: SPRINGER, Pages: 221-251, ISBN: 978-3-319-18358-9
  • 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
    Den Hartog EA, Ruffoni MP, Lawler JE, Pickering JC, Lind K, Brewer NRet al., 2014,

    Fe I oscillator strengths for transitions from high-lying even-parity levels

    , Astrophysical Journal Supplement Series, Vol: 215, Pages: 1-13, ISSN: 0067-0049

    New radiative lifetimes, measured to ±5% accuracy, are reported for 31 even-parity levels of Fe I ranging from 45061 cm–1 to 56842 cm–1. These lifetimes have been measured using single-step and two-step time-resolved laser-induced fluorescence on a slow atomic beam of iron atoms. Branching fractions have been attempted for all of these levels, and completed for 20 levels. This set of levels represents an extension of the collaborative work reported in Ruffoni et al. The radiative lifetimes combined with the branching fractions yields new oscillator strengths for 203 lines of Fe I. Utilizing a 1D-LTE model of the solar photosphere, spectral syntheses for a subset of these lines which are unblended in the solar spectrum yields a mean iron abundance of langlog[ε(Fe)]rang = 7.45 ± 0.06.
  • Journal article
    Southwood D, 2014,

    Space science and policy

    , ASTRONOMY & GEOPHYSICS, Vol: 55, Pages: 26-32, ISSN: 1366-8781
  • 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
    Qureshi MNS, Nasir W, Masood W, Yoon PH, Shah HA, Schwartz SJet al., 2014,

    Terrestrial lion roars and non-Maxwellian distribution

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, ISSN: 2169-9380

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