Publications

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.

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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).

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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

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Citations: 33

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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Citations: 81

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

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Citations: 91

Journal article

Masters A, Achilleos N, Agnor CB, Campagnola S, Charnoz S, Christophe B, Coates AJ, Fletcher LN, Jones GH, Lamy L, Marzari F, Nettelmann N, Ruiz J, Ambrosi R, Andre N, Bhardwaj A, Fortney J, Hansen CJ, Helled R, Moragas-Klostermeyer G, Orton G, Ray L, Reynaud S, Sergis N, Srama R, Volwerk Met al., 2014,

Neptune and Triton: Essential pieces of the Solar System puzzle

, PLANETARY AND SPACE SCIENCE, Vol: 104, Pages: 108-121, ISSN: 0032-0633

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Citations: 32

Journal article

Coustenis A, Atreya S, Castillo J, Coll P, Mueller-Wodarg I, Spilker Let al., 2014,

Surfaces, atmospheres and magnetospheres of the outer planets and their satellites and ring systems: Part X Preface

, PLANETARY AND SPACE SCIENCE, Vol: 104, Pages: 1-2, ISSN: 0032-0633

Journal article

Balogh A, Hudson HS, Petrovay K, von Steiger Ret al., 2014,

Introduction to the Solar Activity Cycle: Overview of Causes and Consequences

, SPACE SCIENCE REVIEWS, Vol: 186, Pages: 1-15, ISSN: 0038-6308

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Citations: 47

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

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Citations: 59

Journal article

Chen CHK, Leung L, Boldyrev S, Maruca BA, Bale SDet al., 2014,

Ion-scale spectral break of solar wind turbulence at high and low beta

, GEOPHYSICAL RESEARCH LETTERS, Vol: 41, Pages: 8081-8088, ISSN: 0094-8276

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Citations: 156

Journal article

Vigren E, Galand M, Yelle RV, Wellbrock A, Coates AJ, Snowden D, Cui J, Lavvas P, Edberg NJT, Shebanits O, Wahlund J-E, Vuitton V, Mandt Ket al., 2014,

Ionization balance in Titan's nightside ionosphere

, Icarus, Vol: 248, Pages: 539-546, ISSN: 0019-1035

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Journal article

Lacombe C, Alexandrova O, Matteini L, Santolik O, Cornilleau-Wehrlin N, Mangeney A, de Conchy Y, Maksimovic Met al., 2014,

Whistler mode waves and the electron heat flux in the Solar wind: cluster observations

, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 796, Pages: 1-11, ISSN: 0004-637X

The nature of the magnetic field fluctuations in the solar wind between the ion and electron scales is still under debate. Using the Cluster/STAFF instrument, we make a survey of the power spectral density and of the polarization of these fluctuations at frequencies f in [1, 400] Hz, during five years (2001-2005), when Cluster was in the free solar wind. In ~10% of the selected data, we observe narrowband, right-handed, circularly polarized fluctuations, with wave vectors quasi-parallel to the mean magnetic field, superimposed on the spectrum of the permanent background turbulence. We interpret these coherent fluctuations as whistler mode waves. The lifetime of these waves varies between a few seconds and several hours. Here, we present, for the first time, an analysis of long-lived whistler waves, i.e., lasting more than five minutes. We find several necessary (but not sufficient) conditions for the observation of whistler waves, mainly a low level of background turbulence, a slow wind, a relatively large electron heat flux, and a low electron collision frequency. When the electron parallel beta factor β e∥ is larger than 3, the whistler waves are seen along the heat flux threshold of the whistler heat flux instability. The presence of such whistler waves confirms that the whistler heat flux instability contributes to the regulation of the solar wind heat flux, at least for β e∥ ≥ 3, in slow wind at 1 AU.

Journal article

Weiss Z, Steers EBM, Pickering JC, Mushtaq Set al., 2014,

Excitation and transition rate diagrams of singly ionized iron in analytical glow discharges in argon, neon and an argon-hydrogen mixture

, JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, Vol: 29, Pages: 2078-2090, ISSN: 0267-9477

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Citations: 11

Journal article

Ball WT, Krivova NA, Unruh YC, Haigh JD, Solanki SKet al., 2014,

A new SATIRE-S spectral solar irradiance reconstruction for solar cycles 21-23 and its implications for stratospheric Ozone

, Journal of the Atmospheric Sciences, Vol: 71, Pages: 4086-4101, ISSN: 0022-4928

The authors present a revised and extended total and spectral solar irradiance (SSI) reconstruction, which includes a wavelength-dependent uncertainty estimate, spanning the last three solar cycles using the Spectral and Total Irradiance Reconstruction—Satellite era (SATIRE-S) model. The SSI reconstruction covers wavelengths between 115 and 160 000 nm and all dates between August 1974 and October 2009. This represents the first full-wavelength SATIRE-S reconstruction to cover the last three solar cycles without data gaps and with an uncertainty estimate. SATIRE-S is compared with the Naval Research Laboratory Spectral Solar Irradiance (NRLSSI) model and ultraviolet (UV) observations from the Solar Radiation and Climate Experiment (SORCE) Solar Stellar Irradiance Comparison Experiment (SOLSTICE). SATIRE-S displays similar cycle behavior to NRLSSI for wavelengths below 242 nm and almost twice the variability between 242 and 310 nm. During the decline of the last solar cycle, between 2003 and 2008, the SSI from SORCE SOLSTICE versions 12 and 10 typically displays more than 3 times the variability of SATIRE-S between 200 and 300 nm. All three datasets are used to model changes in stratospheric ozone within a 2D atmospheric model for a decline from high solar activity to solar minimum. The different flux changes result in different modeled ozone trends. Using NRLSSI leads to a decline in mesospheric ozone, while SATIRE-S and SORCE SOLSTICE result in an increase. Recent publications have highlighted increases in mesospheric ozone when considering version 10 SORCE SOLSTICE irradiances. The recalibrated SORCE SOLSTICE version 12 irradiances result in a much smaller mesospheric ozone response than that of version 10, and this smaller mesospheric ozone response is similar in magnitude to that of SATIRE-S. This shows that current knowledge of variations in spectral irradiance is not sufficient to warrant robust conclusions concerning the impact of solar variability on th

Journal article

Mushtaq S, Steers EBM, Pickering JC, Smid Pet al., 2014,

Enhancement of analyte atomic lines with excitation energies of about 5 eV in the presence of molecular gases in analytical glow discharges

, JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, Vol: 29, Pages: 2022-2026, ISSN: 0267-9477

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Citations: 8

Journal article

Mushtaq S, Steers EBM, Pickering JC, Weinstein Vet al., 2014,

Effect of small quantities of oxygen in a neon glow discharge

, JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, Vol: 29, Pages: 2027-2041, ISSN: 0267-9477

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Citations: 12

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.

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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

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Citations: 83

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

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Citations: 50

Journal article

Slavin JA, DiBraccio GA, Gershman DJ, Imber SM, Poh GK, Raines JM, Zurbuchen TH, Jia X, Baker DN, Glassmeier K-H, Livi SA, Boardsen SA, Cassidy TA, Sarantos M, Sundberg T, Masters A, Johnson CL, Winslow RM, Anderson BJ, Korth H, McNutt RL, Solomon SCet al., 2014,

MESSENGER observations of Mercury's dayside magnetosphere under extreme solar wind conditions

, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, Pages: 8087-8116, ISSN: 2169-9380

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Citations: 130

Journal article

Rieutord M, Beth A, 2014,

Dynamics of the radiative envelope of rapidly rotating stars: Effects of spin-down driven by mass loss

, ASTRONOMY & ASTROPHYSICS, Vol: 570, ISSN: 0004-6361

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Citations: 9

Journal article

Jinks SL, Bunce EJ, Cowley SWH, Provan G, Yeoman TK, Arridge CS, Dougherty MK, Gurnett DA, Krupp N, Kurth WS, Mitchell DG, Morooka M, Wahlund J-Eet al., 2014,