Publications

Journal article

Cheung JCH, Haigh JD, Jackson DR, 2014,

Impact of EOS MLS ozone data on medium-extended range ensemble weather forecasts

, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, Vol: 119, Pages: 9253-9266, ISSN: 2169-897X

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Citations: 27

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.

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Journal article

Pulupa MP, Salem C, Phan TD, Gosling JT, Bale SDet al., 2014,

CORE ELECTRON HEATING IN SOLAR WIND RECONNECTION EXHAUSTS

, ASTROPHYSICAL JOURNAL LETTERS, Vol: 791, ISSN: 2041-8205

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Citations: 12

Journal article

Oieroset M, Sundkvist D, Chaston CC, Phan TD, Mozer FS, McFadden JP, Angelopoulos V, Andersson L, Eastwood JPet al., 2014,

Observations of plasma waves in the colliding jet region of amagnetic flux rope flanked by two active X lines at the subsolar magnetopause

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

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Citations: 30

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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Citations: 9

Journal article

Landi S, Matteini L, Pantellini F, 2014,

ELECTRON HEAT FLUX IN THE SOLAR WIND: ARE WE OBSERVING THE COLLISIONAL LIMIT IN THE 1 AU DATA?

, ASTROPHYSICAL JOURNAL LETTERS, Vol: 790, ISSN: 2041-8205

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Citations: 26

Journal article

Alconcel LNS, Fox P, Brown P, Oddy TM, Lucek EL, Carr CMet al., 2014,

An initial investigation of the long-term trends in the fluxgate magnetometer (FGM) calibration parameters on the four Cluster spacecraft

, GEOSCIENTIFIC INSTRUMENTATION METHODS AND DATA SYSTEMS, Vol: 3, Pages: 95-109, ISSN: 2193-0856

Journal article

Ruffoni MP, Den Hartog EA, Lawler JE, Brewer NR, Lind K, Nave G, Pickering JCet al., 2014,

Fe i oscillator strengths for the Gaia-ESO survey

, Monthly Notices of the Royal Astronomical Society, Vol: 441, Pages: 3127-3136, ISSN: 0035-8711

The Gaia-ESO Public Spectroscopic Survey (GES) is conducting a large-scale study of multi-element chemical abundances of some 100 000 stars in the Milky Way with the ultimate aim of quantifying the formation history and evolution of young, mature and ancient Galactic populations. However, in preparing for the analysis of GES spectra, it has been noted that atomic oscillator strengths of important Fe I lines required to correctly model stellar line intensities are missing from the atomic data base. Here, we present new experimental oscillator strengths derived from branching fractions and level lifetimes, for 142 transitions of Fe I between 3526 and 10 864 Å, of which at least 38 are urgently needed by GES. We also assess the impact of these new data on solar spectral synthesis and demonstrate that for 36 lines that appear unblended in the Sun, Fe abundance measurements yield a small line-by-line scatter (0.08 dex) with a mean abundance of 7.44 dex in good agreement with recent publications.

Journal article

Masters A, 2014,

Magnetic reconnection at Uranus' magnetopause

, Journal of Geophysical Research: Space Physics, Vol: 119, Pages: 5520-5538, ISSN: 2169-9380

The magnetosphere of Uranus has barely been explored by spacecraft but is distinct from other solar system magnetospheres in many respects. Determining how this magnetosphere is coupled to the solar wind is central to understanding energy flow through the system. Here we assess how the solar wind interacts with the Uranian magnetosphere via magnetic reconnection. Analytical models of conditions at the magnetopause are combined with current understanding of reconnection onset to predict where reconnection may occur on the boundary. The results suggest that conditions at Uranus' magnetopause are generally less favorable for reconnection than those at the magnetopause of any planet closer to the Sun, as a result of how typical solar wind parameters vary with heliocentric distance. The location of reconnection sites on the Uranian magnetopause is likely to be highly dependent on not only the interplanetary magnetic field orientation but also planetary longitude and season. Solar wind–magnetosphere coupling via magnetic reconnection may be stronger under near‐solstice conditions than under near‐equinox conditions. We discuss the typical reconnection electric field strength at Uranus' magnetopause and suggest that the typical reconnection voltage is considerably less than 40 kV. Complimentary assessments of other means of coupling to the solar wind (e.g., via a “viscous‐like” interaction) are needed to establish the overall nature of solar wind–magnetosphere coupling at Uranus.

Journal article

Sulaiman AH, Masters A, Dougherty MK, Jia Xet al., 2014,

The magnetic structure of Saturn's magnetosheath

, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, Pages: 5651-5661, ISSN: 2169-9380

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Citations: 21

Journal article

McAndrews HJ, Thomsen MF, Arridge CS, Jackman CM, Wilson RJ, Henderson MG, Tokar RL, Khurana KK, Sittler EC, Coates AJ, Dougherty MKet al., 2014,

Plasma in Saturn's nightside magnetosphere and the implications for global circulation (vol 57, pg 1714, 2009)

, PLANETARY AND SPACE SCIENCE, Vol: 97, Pages: 86-87, ISSN: 0032-0633

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Citations: 5

Journal article

Jackman CM, Slavin JA, Kivelson MG, Southwood DJ, Achilleos N, Thomsen MF, DiBraccio GA, Eastwood JP, Freeman MP, Dougherty MK, Vogt MFet al., 2014,

Saturn's dynamic magnetotail: A comprehensive magnetic field and plasma survey of plasmoids and traveling compression regions and their role in global magnetospheric dynamics

, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, Pages: 5465-5494, ISSN: 2169-9380

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Citations: 67

Journal article

Selzer LA, Hnat B, Osman KT, Nakariakov VM, Eastwood JP, Burgess Det al., 2014,

TEMPERATURE ANISOTROPY IN THE PRESENCE OF ULTRA LOW FREQUENCY WAVES IN THE TERRESTRIAL FORESHOCK

, ASTROPHYSICAL JOURNAL LETTERS, Vol: 788, ISSN: 2041-8205

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Citations: 5

Journal article

Owens MJ, Horbury TS, Wicks RT, McGregor SL, Savani NP, Xiong Met al., 2014,

Ensemble downscaling in coupled solar wind-magnetosphere modeling for space weather forecasting

, Space Weather, Vol: 12, Pages: 395-405, ISSN: 1539-4956

Advanced forecasting of space weather requires simulation of the whole Sun-to-Earth system, which necessitates driving magnetospheric models with the outputs from solar wind models. This presents a fundamental difficulty, as the magnetosphere is sensitive to both large-scale solar wind structures, which can be captured by solar wind models, and small-scale solar wind “noise,” which is far below typical solar wind model resolution and results primarily from stochastic processes. Following similar approaches in terrestrial climate modeling, we propose statistical “downscaling” of solar wind model results prior to their use as input to a magnetospheric model. As magnetospheric response can be highly nonlinear, this is preferable to downscaling the results of magnetospheric modeling. To demonstrate the benefit of this approach, we first approximate solar wind model output by smoothing solar wind observations with an 8 h filter, then add small-scale structure back in through the addition of random noise with the observed spectral characteristics. Here we use a very simple parameterization of noise based upon the observed probability distribution functions of solar wind parameters, but more sophisticated methods will be developed in the future. An ensemble of results from the simple downscaling scheme are tested using a model-independent method and shown to add value to the magnetospheric forecast, both improving the best estimate and quantifying the uncertainty. We suggest a number of features desirable in an operational solar wind downscaling scheme.

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Journal article

Hietala H, Eastwood JP, Isavnin A, 2014,

Sequentially released tilted flux ropes in the Earth's magnetotail

, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335

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Citations: 17

Journal article

Miller RL, Schmidt GA, Nazarenko LS, Tausnev N, Bauer SE, DelGenio AD, Kelley M, Lo KK, Ruedy R, Shindell DT, Aleinov I, Bauer M, Bleck R, Canuto V, Chen Y, Cheng Y, Clune TL, Faluvegi G, Hansen JE, Healy RJ, Kiang NY, Koch D, Lacis AA, LeGrande AN, Lerner J, Menon S, Oinas V, Garcia-Pando CP, Perlwitz JP, Puma MJ, Rind D, Romanou A, Russell GL, Sato M, Sun S, Tsigaridis K, Unger N, Voulgarakis A, Yao M-S, Zhang Jet al., 2014,

CMIP5 historical simulations (1850-2012) with GISS ModelE2

, JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS, Vol: 6, Pages: 441-477

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Citations: 136

Journal article

Marlier ME, Voulgarakis A, Shindell DT, Faluvegi G, Henry CL, Randerson JTet al., 2014,

The role of temporal evolution in modeling atmospheric emissions from tropical fires

, ATMOSPHERIC ENVIRONMENT, Vol: 89, Pages: 158-168, ISSN: 1352-2310

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Citations: 12

Journal article

Gryspeerdt E, Stier P, Grandey BS, 2014,

Cloud fraction mediates the aerosol optical depth-cloud top height relationship

, GEOPHYSICAL RESEARCH LETTERS, Vol: 41, Pages: 3622-3627, ISSN: 0094-8276

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Citations: 44

Journal article

Nichols JD, Badman SV, Baines KH, Brown RH, Bunce EJ, Clarke JT, Cowley SWH, Crary FJ, Dougherty MK, Gerard J-C, Grocott A, Grodent D, Kurth WS, Melin H, Mitchell DG, Pryor WR, Stallard TSet al., 2014,

Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope

, Geophysical Research Letters, Vol: 41, Pages: 3323-3330, ISSN: 1944-8007

We present observations of significant dynamics within two UV auroral storms observedon Saturn using the Hubble Space Telescope in April/May 2013. Specifically, we discuss bursts of auroralemission observed at the poleward boundary of a solar wind-induced auroral storm, propagating at ∼330%rigid corotation from near ∼01 h LT toward ∼08 h LT. We suggest that these are indicative of ongoing, burstyreconnection of lobe flux in the magnetotail, providing strong evidence that Saturn’s auroral storms arecaused by large-scale flux closure. We also discuss the later evolution of a similar storm and show that theemission maps to the trailing region of an energetic neutral atom enhancement. We thus identify the auroralform with the upward field-aligned continuity currents flowing into the associated partial ring current.

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Journal article

Simon S, Saur J, van Treeck SC, Kriegel H, Dougherty MKet al., 2014,

Discontinuities in the magnetic field near Enceladus

, GEOPHYSICAL RESEARCH LETTERS, Vol: 41, Pages: 3359-3366, ISSN: 0094-8276

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Citations: 14

Journal article

Ceppi P, Zelinka MD, Hartmann DL, 2014,

The response of the Southern Hemispheric eddy-driven jet to future changes in shortwave radiation in CMIP5

, Geophysical Research Letters, Vol: 41, Pages: 3244-3250, ISSN: 0094-8276

A strong relationship is found between changes in the meridional gradient of absorbed shortwave radiation (ASR) and Southern Hemispheric jet shifts in 21st century climate simulations of CMIP5 (Coupled Model Intercomparison Project phase 5) coupled models. The relationship is such that models with increases in the meridional ASR gradient around the southern midlatitudes, and therefore increases in midlatitude baroclinicity, tend to produce a larger poleward jet shift. The ASR changes are shown to be dominated by changes in cloud properties, with sea ice declines playing a secondary role. We demonstrate that the ASR changes are the cause, and not the result, of the intermodel differences in jet response by comparing coupled simulations with experiments in which sea surface temperature increases are prescribed. Our results highlight the importance of reducing the uncertainty in cloud feedbacks in order to constrain future circulation changes.

Book chapter

Galand MIF, Coates A, Cravens T, Wahlund J-Eet al., 2014,

Titan's Ionosphere

, Titan: Interior, Surface, Atmosphere, and Space Environment, Editors: Mueller-Wodarg, Griffith, Lellouch, Cravens, Publisher: Cambridge University Press, Pages: 376-418, ISBN: 9780521199926

Journal article

Vigren E, Galand M, Shebanits O, Wahlund J-E, Geppert WD, Lavvas P, Vuitton V, Yelle RVet al., 2014,

INCREASING POSITIVE ION NUMBER DENSITIES BELOW THE PEAK OF ION-ELECTRON PAIR PRODUCTION IN TITAN'S IONOSPHERE

, ASTROPHYSICAL JOURNAL, Vol: 786, ISSN: 0004-637X

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Citations: 10

Journal article

Southwood D, 2014,

Crowded Orbits: Conflict and Cooperation in Space

, NATURE, Vol: 509, Pages: 32-32, ISSN: 0028-0836

Journal article

Bunce EJ, Grodent DC, Jinks SL, Andrews DJ, Badman SV, Coates AJ, Cowley SWH, Dougherty MK, Kurth WS, Mitchell DG, Provan Get al., 2014,

Cassini nightside observations of the oscillatory motion of Saturn's northern auroral oval

, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, Pages: 3528-3543, ISSN: 2169-9380

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Citations: 17

Journal article

Ansell C, Brindley HE, Pradhan Y, Saunders Ret al., 2014,

Mineral dust aerosol net direct radiative effect during GERBILS field campaign period derived from SEVIRI and GERB

, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, Vol: 119, Pages: 4070-4086, ISSN: 2169-897X

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Citations: 15

Journal article

Goldman MV, Newman DL, Lapenta G, Andersson L, Gosling JT, Eriksson S, Markidis S, Eastwood JP, Ergun Ret al., 2014,

Cerenkov Emission of Quasiparallel Whistlers by Fast Electron Phase-Space Holes during Magnetic Reconnection

, PHYSICAL REVIEW LETTERS, Vol: 112, ISSN: 0031-9007

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Citations: 56

Journal article

Badman SV, Branduardi-Raymont G, Galand M, Hess SLG, Krupp N, Lamy L, Melin H, Tao Cet al., 2014,

Auroral Processes at the Giant Planets: Energy Deposition, Emission Mechanisms, Morphology and Spectra

, Space Science Reviews, Vol: 187, Pages: 99-179, ISSN: 1572-9672

The ionospheric response to auroral precipitation at the giant planets is reviewed,using models and observations. The emission processes for aurorae at radio, infrared, visible,ultraviolet, and X-ray wavelengths are described, and exemplified using ground- andspace-based observations. Comparisons between the emissions at different wavelengths are made, where possible, and interpreted in terms of precipitating particle characteristics oratmospheric conditions. Finally, the spatial distributions and dynamics of the various componentsof the aurorae (moon footprints, low-latitude, main oval, polar) are related to magnetosphericprocesses and boundaries, using theory, in situ, and remote observations, withthe aim of distinguishing between those related to internally-driven dynamics, and thoserelated to the solar wind interaction.