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  • Journal article
    Krupp N, Roussos E, Kollmann P, Mitchell DG, Paranicas CP, Krimigis SM, Hamilton DC, Hedman M, Dougherty MKet al., 2018,

    Energetic Neutral and Charged Particle Measurements in the Inner Saturnian Magnetosphere During the Grand Finale Orbits of Cassini 2016/2017

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 45, Pages: 10847-10854, ISSN: 0094-8276
  • Book chapter
    Dougherty M, Buratti BJ, Seidelmann PK, Spencer JRet al., 2018,

    Enceladus as an active world: History and discovery. In Enceladus and the Icy

    , Enceladus and the Icy Moons of Saturn, Editors: Schenk, Clark, Howett, Verbiscer, Waite, Publisher: University of Arizona Press, Pages: 3-16, ISBN: 9780816537075

    Dougherty M. K., Buratti B. J., Seidelmann P. K., and Spencer J. R. (2018) Enceladus as an active world: History and discovery. In Enceladus and the Icy Moons of Saturn (P. M. Schenk et al., eds.), pp. 3–16. Univ. of Arizona, Tucson, DOI: ...
  • Journal article
    Inai Y, Fujita R, Machida T, Matsueda H, Sawa Y, Tsuboi K, Katsumata K, Morimoto S, Aoki S, Nakazawa Tet al., 2018,

    Seasonal characteristics of chemical and dynamical transports into the extratropical upper troposphere/lower stratosphere

    <jats:p>Abstract. To investigate the seasonal characteristics of chemical tracer distributions in the extratropical upper troposphere and lower stratosphere (ExUTLS) as well as stratosphere–troposphere exchange processes, mixing fractions of air masses originating in the stratosphere, tropical troposphere, mid-latitude lower troposphere (LT), and high-latitude LT in the ExUTLS are estimated using 90-day backward trajectories calculated with European Centre For Medium-Range Weather Forecasts (ECMWF) ERA-Interim data as the meteorological input. Time-series of chemical tracers obtained from ground-based and airborne observations are incorporated into the estimated mixing fractions, thus reconstructing spatiotemporal distributions of chemical tracers in the ExUTLS. The reconstructed tracer distributions are analysed with the mixing fractions and the stratospheric age of air (AoA) estimated using a 10-year backward trajectory. The reconstructed distributions of CO and CO2 in the ExUTLS are affected primarily by tropospheric air masses because of the short chemical lifetime of the former and large seasonal variations in the troposphere of the latter. Distributions of CH4, N2O, and SF6 are controlled primarily by seasonally varying air masses transported from the stratosphere. For CH4 and N2O distributions, air masses transported via the deep branch of the Brewer–Dobson circulation are particularly important. This interpretation is qualitatively and quantitatively supported by the estimated spatiotemporal distributions of AoA. </jats:p>
  • Journal article
    Stansby D, Salem C, Matteini L, Horbury Tet al., 2018,

    A new inner heliosphere proton parameter dataset from the Helios mission

    , Solar Physics, Vol: 293, ISSN: 0038-0938

    In the near future, Parker Solar Probe and Solar Orbiter will provide the first comprehensive in-situ measurements of the solar wind in the inner heliosphere since the Helios mission in the 1970s. We describe a reprocessing of the original Helios ion distribution functions to provide reliable and reproducible data to characterise the proton core population of the solar wind in the inner heliosphere. A systematic fitting of bi-Maxwellian distribution functions was performed to the raw Helios ion distribution function data to extract the proton core number density, velocity, and temperatures parallel and perpendicular to the magnetic field. We present radial trends of these derived proton parameters, forming a benchmark to which new measurements in the inner heliosphere will be compared. The new dataset has been made openly available for other researchers to use, along with the source code used to generate it.
  • Journal article
    Sorba AM, Achilleos NA, Guio P, Arridge CS, Sergis N, Dougherty MKet al., 2018,

    The Periodic Flapping and Breathing of Saturn's Magnetodisk During Equinox

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 8292-8316, ISSN: 2169-9380
  • Journal article
    Hwang KJ, Sibeck DG, Burch JL, Choi E, Fear RC, Lavraud B, Giles BL, Gershman D, Pollock CJ, Eastwood JP, Khotyaintsev Y, Escoubet P, Fu H, Toledo-Redondo S, Torbert RB, Ergun RE, Paterson WR, Dorelli JC, Avanov L, Russell CT, Strangeway RJet al., 2018,

    Small-scale flux transfer events formed in the reconnection exhaust region between two X lines

    , Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 8473-8488, ISSN: 2169-9380

    We report MMS observations of the ion-scale flux transfer events (FTEs) that may involve two main X lines and tearing instability between the two X lines. The four spacecraft detected multiple isolated regions with enhanced magnetic field strength and bipolar Bn signatures normal to the nominal magnetopause, indicating FTEs. The currents within the FTEs flow mostly parallel to B, and the magnetic tension force is balanced by the total pressure gradient force. During these events, the plasma bulk flow velocity was directed southward. Detailed analysis of the magnetic and electric field and plasma moments variations suggests that the FTEs were initially embedded within the exhaust region north of an X line but were later located southward/downstream of a subsequent X line. The cross sections of the individual FTEs are in the range of ~2.5–6.8 ion inertial lengths. The observations suggest the formation of multiple secondary FTEs. The presence of an X line in the exhaust region southward of a second X line results from the southward drift of an old X line and the reformation of a new X line. The current layer between the two X lines is unstable to the tearing instability, generating multiple ion-scale flux-rope-type secondary islands.
  • Journal article
    Yao ZH, Radioti A, Grodent D, Ray LC, Palmaerts B, Sergis N, Dialynas K, Coates AJ, Arridge CS, Roussos E, Badman SV, Ye S-Y, Gerard J-C, Delamere PA, Guo RL, Pu ZY, Waite JH, Krupp N, Mitchell DG, Dougherty MKet al., 2018,

    Recurrent Magnetic Dipolarization at Saturn: Revealed by Cassini

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 8502-8517, ISSN: 2169-9380
  • Journal article
    Tong Y, Vasko I, Mozer FS, Bale SD, Roth I, Artemyev AV, Ergun R, Giles B, Lindqvist P-A, Russell CT, Strangeway R, Torbert RBet al., 2018,

    Simultaneous Multispacecraft Probing of Electron Phase Space Holes

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 45, Pages: 11513-11519, ISSN: 0094-8276
  • Journal article
    Smith CJ, Kramer RJ, Myhre G, Forster PM, Soden BJ, Andrews T, Boucher O, Faluvegi G, Fläschner D, Hodnebrog, Kasoar M, Kharin V, Kirkevåg A, Lamarque JF, Mülmenstädt J, Olivié D, Richardson T, Samset BH, Shindell D, Stier P, Takemura T, Voulgarakis A, Watson-Parris Det al., 2018,

    Understanding rapid adjustments to diverse forcing agents

    , Geophysical Research Letters, Vol: 45, Pages: 12023-12031, ISSN: 0094-8276

    Rapid adjustments are responses to forcing agents that cause a perturbation to the top of atmosphere energy budget but are uncoupled to changes in surface warming. Different mechanisms are responsible for these adjustments for a variety of climate drivers. These remain to be quantified in detail. It is shown that rapid adjustments reduce the effective radiative forcing (ERF) of black carbon by half of the instantaneous forcing, but for CO2 forcing, rapid adjustments increase ERF. Competing tropospheric adjustments for CO2 forcing are individually significant but sum to zero, such that the ERF equals the stratospherically adjusted radiative forcing, but this is not true for other forcing agents. Additional experiments of increase in the solar constant and increase in CH4 are used to show that a key factor of the rapid adjustment for an individual climate driver is changes in temperature in the upper troposphere and lower stratosphere.
  • Journal article
    Schwartz SJ, Avanov L, Turner D, Zhang H, Gingell I, Eastwood JP, Gershman DJ, Johlander A, Russell CT, Burch JL, Dorelli JC, Eriksson S, Ergun RE, Fuselier SA, Giles BL, Goodrich KA, Khotyaintsev YV, Lavraud B, Lindqvist PA, Oka M, Phan TD, Strangeway RJ, Trattner KJ, Torbert RB, Vaivads A, Wei H, Wilder Fet al., 2018,

    Ion kinetics in a hot flow anomaly: MMS observations

    , Geophysical Research Letters, Vol: 45, Pages: 11520-11529, ISSN: 0094-8276

    Hot Flow Anomalies (HFAs) are transients observed at planetary bow shocks, formed by the shock interaction with a convected interplanetary current sheet. The primary interpretation relies on reflected ions channeled upstream along the current sheet. The short duration of HFAs has made direct observations of this process difficult. We employ high resolution measurements by NASA's Magnetospheric Multiscale Mission to probe the ion microphysics within a HFA. Magnetospheric Multiscale Mission data reveal a smoothly varying internal density and pressure, which increase toward the trailing edge of the HFA, sweeping up particles trapped within the current sheet. We find remnants of reflected or other backstreaming ions traveling along the current sheet, but most of these are not fast enough to out-run the incident current sheet convection. Despite the high level of internal turbulence, incident and backstreaming ions appear to couple gyro-kinetically in a coherent manner.
  • Journal article
    Vasquez BJ, Forman MA, Coburn JT, Smith CW, Stawarz JEet al., 2018,

    The Turbulent Cascade for High Cross-helicity States at 1 au. II. Minor Energy

    , ASTROPHYSICAL JOURNAL, Vol: 867, ISSN: 0004-637X
  • Journal article
    Tinetti G, Drossart P, Eccleston P, Hartogh P, Heske A, Leconte J, Micela G, Ollivier M, Pilbratt G, Puig L, Turrini D, Vandenbussche B, Wolkenberg P, Beaulieu J-P, Buchave LA, Ferus M, Griffin M, Guedel M, Justtanont K, Lagage P-O, Machado P, Malaguti G, Min M, Norgaard-Nielsen HU, Rataj M, Ray T, Ribas I, Swain M, Szabo R, Werner S, Barstow J, Burleigh M, Cho J, du Foresto VC, Coustenis A, Decin L, Encrenaz T, Galand M, Gillon M, Helled R, Carlos Morales J, Munoz AG, Moneti A, Pagano I, Pascale E, Piccioni G, Pinfield D, Sarkar S, Selsis F, Tennyson J, Triaud A, Venot O, Waldmann I, Waltham D, Wright G, Amiaux J, Augueres J-L, Berthe M, Bezawada N, Bishop G, Bowles N, Coffey D, Colome J, Crook M, Crouzet P-E, Da Peppo V, Sanz IE, Focardi M, Frericks M, Hunt T, Kohley R, Middleton K, Morgante G, Ottensamer R, Pace E, Pearson C, Stamper R, Symonds K, Rengel M, Renotte E, Ade P, Affer L, Alard C, Allard N, Altieri F, Andre Y, Arena C, Argyriou I, Aylward A, Baccani C, Bakos G, Banaszkiewicz M, Barlow M, Batista V, Bellucci G, Benatti S, Bernardi P, Bezard B, Blecka M, Bolmont E, Bonfond B, Bonito R, Bonomo AS, Brucato JR, Brun AS, Bryson I, Bujwan W, Casewell S, Charnay B, Pestellini CC, Chen G, Ciaravella A, Claudi R, Cledassou R, Damasso M, Damiano M, Danielski C, Deroo P, Di Giorgio AM, Dominik C, Doublier V, Doyle S, Doyon R, Drummond B, Duong B, Eales S, Edwards B, Farina M, Flaccomio E, Fletcher L, Forget F, Fossey S, Fraenz M, Fujii Y, Garcia-Piquer A, Gear W, Geoffray H, Gerard JC, Gesa L, Gomez H, Graczyk R, Griffith C, Grodent D, Guarcello MG, Gustin J, Hamano K, Hargrave P, Hello Y, Heng K, Herrero E, Hornstrup A, Hubert B, Ida S, Ikoma M, Iro N, Irwin P, Jarchow C, Jaubert J, Jones H, Julien Q, Kameda S, Kerschbaum F, Kervella P, Koskinen T, Krijger M, Krupp N, Lafarga M, Landini F, Lellouch E, Leto G, Luntzer A, Rank-Luftinger T, Maggio A, Maldonado J, Maillard J-P, Mall U, Marquette J-B, Mathis S, Maxted P, Matsuo T, Medvedev A, Miguel Y, Minier V, Moreet al., 2018,

    A chemical survey of exoplanets with ARIEL

    , Experimental Astronomy, Vol: 46, Pages: 135-209, ISSN: 0922-6435

    Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using know
  • Journal article
    Weiss Z, Pickering JC, Hoffmann V, 2018,

    Obituary Prof. Edward B. M. Steers (1931-2018)

    , SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY, Vol: 149, Pages: 241-242, ISSN: 0584-8547
  • Journal article
    Hajra R, Henri P, Myllys M, Heritier KL, Galand M, Wedlund CS, Breuillard H, Behar E, Edberg NJT, Goetz C, Nilsson H, Eriksson AI, Goldstein R, Tsurutani BT, More J, Vallieres X, Wattieauxu Get al., 2018,

    Cometary plasma response to interplanetary corotating interaction regions during 2016 June-September: a quantitative study by the Rosetta Plasma Consortium

    , Monthly Notices of the Royal Astronomical Society, Vol: 480, Pages: 4544-4556, ISSN: 0035-8711

    Four interplanetary corotating interaction regions (CIRs) were identified during 2016 June–September by the Rosetta Plasma Consortium (RPC) monitoring in situ the plasma environment of the comet 67P/Churyumov–Gerasimenko (67P) at heliocentric distances of ∼3–3.8 au. The CIRs, formed in the interface region between low- and high-speed solar wind streams with speeds of ∼320–400 km s−1 and ∼580–640 km s−1, respectively, are characterized by relative increases in solar wind proton density by factors of ∼13–29, in proton temperature by ∼7–29, and in magnetic field by ∼1–4 with respect to the pre-CIR values. The CIR boundaries are well defined with interplanetary discontinuities. Out of 10 discontinuities, four are determined to be forward waves and five are reverse waves, propagating at ∼5–92 per cent of the magnetosonic speed at angles of ∼20°–87° relative to ambient magnetic field. Only one is identified to be a quasi-parallel forward shock with magnetosonic Mach number of ∼1.48 and shock normal angle of ∼41°. The cometary ionosphere response was monitored by Rosetta from cometocentric distances of ∼4–30 km. A quiet time plasma density map was developed by considering dependences on cometary latitude, longitude, and cometocentric distance of Rosetta observations before and after each of the CIR intervals. The CIRs lead to plasma density enhancements of ∼500–1000 per cent with respect to the quiet time reference level. Ionospheric modelling shows that increased ionization rate due to enhanced ionizing (>12–200 eV) electron impact is the prime cause of the large cometary plasma density enhancements during the CIRs. Plausible origin mechanisms of the cometary ionizing electron enhancements are discussed.
  • Journal article
    Archer MO, Hartinger MD, Redmon R, Angelopoulos V, Walsh BMet al., 2018,

    First results from sonification and exploratory cttizen science of magnetospheric ULF waves: long-lasting decreasing-frequency poloidal Field line resonance following geomagnetic storms

    , Space Weather, Vol: 16, Pages: 1753-1769, ISSN: 1539-4956

    Magnetospheric ultralow‐frequency (ULF) waves contribute to space weather in the solar wind‐magnetosphere‐ionosphere system. The monitoring of these waves by space‐ and ground‐based instruments, however, produces big data, which are difficult to navigate, mine, and analyze effectively. We present sonification, the process of converting an oscillatory time series into audible sound, and citizen science, where members of the public contribute to scientific investigations, as a means to potentially help tackle these issues. Magnetometer data in the ULF range at geostationary orbit have been sonified and released to London high schools as part of exploratory projects. While this approach reduces the overall likelihood of useful results from any particular group of citizen scientists compared to typical citizen science projects, it promotes independent learning and problem solving by all participants and can result in a small number of unexpected research outcomes. We present one such example, a case study identified by a group of students of decreasing‐frequency poloidal field line resonances over multiple days found to occur during the recovery phase of a coronal mass ejection‐driven geomagnetic storm. Simultaneous plasma density measurements show that the decreasing frequencies were due to the refilling of the plasmasphere following the storm. The waves were likely generated by internal plasma processes. Further exploration of the audio revealed many similar events following other major storms; thus, they are much more common than previously thought. We therefore highlight the potential of sonification and exploratory citizen science in addressing some of the challenges facing ULF wave research.
  • Journal article
    Liu F, Wienke C, Fiencke C, Guo J, Dong R, Pfeiffer E-Met al., 2018,

    Biofilter with mixture of pine bark and expanded clay as packing material for methane treatment in lab-scale experiment and field-scale implementation

    , Environmental Science and Pollution Research, Vol: 25, Pages: 31297-31306, ISSN: 0944-1344
  • Journal article
    Goodrich KA, Ergun R, Schwartz SJ, Wilson LB, Newman D, Wilder FD, Holmes J, Johlander A, Burch J, Torbert R, Khotyaintsev Y, Lindqvist P-A, Strangeway R, Russell C, Gershman D, Giles B, Andersson Let al., 2018,

    MMS Observations of Electrostatic Waves in an Oblique Shock Crossing

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 9430-9442, ISSN: 2169-9380
  • Journal article
    Myhre G, Kramer RJ, Smith CJ, Hodnebrog, Forster P, Soden BJ, Samset BH, Stjern CW, Andrews T, Boucher O, Faluvegi G, Fläschner D, Kasoar M, Kirkevåg A, Lamarque JF, Olivié D, Richardson T, Shindell D, Stier P, Takemura T, Voulgarakis A, Watson-Parris Det al., 2018,

    Quantifying the importance of rapid adjustments for global precipitation changes

    , Geophysical Research Letters, Vol: 20, Pages: 11399-11405, ISSN: 0094-8276

    Different climate drivers influence precipitation in different ways. Here we use radiative kernels to understand the influence of rapid adjustment processes on precipitation in climate models. Rapid adjustments are generally triggered by the initial heating or cooling of the atmosphere from an external climate driver. For precipitation changes, rapid adjustments due to changes in temperature, water vapor, and clouds are most important. In this study we have investigated five climate drivers (CO2, CH4, solar irradiance, black carbon, and sulfate aerosols). The fast precipitation responses to a doubling of CO2 and a 10-fold increase in black carbon are found to be similar, despite very different instantaneous changes in the radiative cooling, individual rapid adjustments, and sensible heating. The model diversity in rapid adjustments is smaller for the experiment involving an increase in the solar irradiance compared to the other climate driver perturbations, and this is also seen in the precipitation changes.
  • Journal article
    Shawki D, Voulgarakis A, Chakraborty A, Kasoar MR, Srinivasan JSet al., 2018,

    The South Asian monsoon response to remote aerosols: global and regional mechanisms

    , Journal of Geophysical Research, Vol: 123, Pages: 11585-11601, ISSN: 0148-0227

    The South Asian summer monsoon has been suggested to be influenced by atmospheric aerosols, and this influence can be the result of either local or remote emissions. We have used the Hadley Centre Global Environment Model Version 3 (HadGEM3) coupled atmosphere‐ocean climate model to investigate for the first time the centennial‐scale South Asian precipitation response to emissions of sulfur dioxide (SO2), the dominant anthropogenic precursor of sulfate aerosol, from different midlatitude regions. Despite the localized nature of the regional heating that results from removing SO2 emissions, all experiments featured a similar large‐scale precipitation response over South Asia, driven by ocean‐modulated changes in the net cross‐equatorial heat transport and an opposing cross‐equatorial northward moisture transport. The effects are linearly additive, with the sum of the responses from the experiments where SO2 is removed from the United States, Europe, and East Asia resembling the response seen in the experiment where emissions are removed from the northern midlatitudes as a whole, but with East Asia being the largest contributor, even per unit of emission or top‐of‐atmosphere radiative forcing. This stems from the fact that East Asian emissions can more easily influence regional land‐sea thermal contrasts and sea level pressure differences that drive the monsoon circulation, compared to emissions from more remote regions. Our results suggest that radiative effects of remote pollution should not be neglected when examining changes in South Asian climate and that and it is important to examine such effects in coupled ocean‐atmosphere modeling frameworks.
  • Conference paper
    Smith CW, Coburn JT, Vasquez BJ, Forman MA, Stawarz JEet al., 2018,

    Correlation Scales of the Turbulent Cascade at 1 AU

    , 17th Annual International Astrophysics Conference (AIAC) on Dissipative and Heating Processes in Collisionless Plasma - The Solar Corona, The Solar Wind, and The Interstellar Medium, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
  • Journal article
    Bandyopadhyay R, Chasapis A, Chhiber R, Parashar TN, Maruca BA, Matthaeus WH, Schwartz SJ, Eriksson S, Le Contel O, Breuillard H, Burch JL, Moore TE, Pollock CJ, Giles BL, Paterson WR, Dorelli J, Gershman DJ, Torbert RB, Russell CT, Strangeway RJet al., 2018,

    Solar Wind Turbulence Studies Using MMS Fast Plasma Investigation Data

    , ASTROPHYSICAL JOURNAL, Vol: 866, ISSN: 0004-637X
  • Journal article
    Khurana KK, Dougherty MK, Provan G, Hunt GJ, Kivelson MG, Cowley SWH, Southwood DJ, Russell CTet al., 2018,

    Discovery of atmospheric-wind-driven electric currents in Saturn's magnetosphere in the gap between Saturn and its rings

    , Geophysical Research Letters, Vol: 45, Pages: 10068-10074, ISSN: 0094-8276

    Magnetic field observations obtained by the Cassini spacecraft as it traversed regions inside of Saturn's D ring packed a genuine surprise. The azimuthal component of the magnetic field recorded a consistent positive perturbation with a strength of 15–25 nT near closest approach. The closest approaches were near the equatorial plane of Saturn and were distributed narrowly around local noon and brought the spacecraft to within 2,550 km of Saturn's cloud tops. Modeling of this perturbation shows that it is not of internal origin but is produced by external currents that couple the low‐latitude northern ionosphere to the low‐latitude southern ionosphere. The azimuthal perturbations diminish at higher latitudes on field lines that connect to Saturn's icy rings. The sense of the current system suggests that the southern feet of the field lines in the ionosphere leads their northern counterparts. We show that the observed field perturbations are consistent with a field‐aligned current whose strength is ~1 MA/radian, that is, comparable in strength to the planetary‐period‐oscillation‐related current systems observed in the auroral zone. We show that the Lorentz force in the ionosphere extracts momentum from the faster moving low‐latitude zonal belt and delivers it to the northern ionosphere. We further show that the electric current is generated when the two ends of a field line are embedded in zonal flows with differing wind speeds in the low‐latitude thermosphere. The wind‐generated currents dissipate 2 × 1011W of thermal power, similar to the input from the solar extreme ultraviolet flux in this region.
  • Journal article
    Hanna E, Fettweis X, Hall RJ, 2018,

    Brief communication: Recent changes in summer Greenland blocking captured by none of the CMIP5 models

    , CRYOSPHERE, Vol: 12, Pages: 3287-3292, ISSN: 1994-0416
  • Journal article
    Gewin V, Keith D, Haigh J, Lattin Cet al., 2018,

    Tackling harassment

    , NATURE, Vol: 562, Pages: 449-450, ISSN: 0028-0836
  • Journal article
    Jones G, Agarwal J, Bowles N, Burchell M, Coates A, Fitzsimmons A, Graps A, Hsieh H, Lisse C, Lowry S, Masters A, Snodgrass C, Tubiana Cet al., 2018,

    The proposed Caroline ESA M3 mission to a Main Belt Comet

    , Advances in Space Research, Vol: 62, Pages: 1921-1946, ISSN: 0273-1177

    We describe Caroline, a mission proposal submitted to the European Space Agency in 2010 in response to the Cosmic Visions M3 call for medium-sized missions. Caroline would have travelled to a Main Belt Comet (MBC), characterizing the object during a flyby, and capturing dust from its tenuous coma for return to Earth. MBCs are suspected to be transition objects straddling the traditional boundary between volatile–poor rocky asteroids and volatile–rich comets. The weak cometary activity exhibited by these objects indicates the presence of water ice, and may represent the primary type of object that delivered water to the early Earth. The Caroline mission would have employed aerogel as a medium for the capture of dust grains, as successfully used by the NASA Stardust mission to Comet 81P/Wild 2. We describe the proposed mission design, primary elements of the spacecraft, and provide an overview of the science instruments and their measurement goals. Caroline was ultimately not selected by the European Space Agency during the M3 call; we briefly reflect on the pros and cons of the mission as proposed, and how current and future mission MBC mission proposals such as Castalia could best be approached.
  • Journal article
    Snodgrass C, Jones GH, Boehnhardt H, Gibbings A, Homeister M, Andre N, Beck P, Bentley MS, Bertini I, Bowles N, Capria MT, Carr C, Ceriotti M, Coates AJ, Della Corte V, Donaldson Hanna KL, Fitzsimmons A, Gutiérrez PJ, Hainaut OR, Herique A, Hilchenbach M, Hsieh HH, Jehin E, Karatekin O, Kofman W, Lara LM, Laudan K, Licandro J, Lowry SC, Marzari F, Masters A, Meech KJ, Moreno F, Morse A, Orosei R, Pack A, Plettemeier D, Prialnik D, Rotundi A, Rubin M, Sánchez JP, Sheridan S, Trieloff M, Winterboer Aet al., 2018,

    The Castalia mission to Main Belt Comet 133P/Elst-Pizarro

    , Advances in Space Research, Vol: 62, Pages: 1947-1976, ISSN: 0273-1177

    We describe Castalia, a proposed mission to rendezvous with a Main Belt Comet (MBC), 133P/Elst-Pizarro. MBCs are a recently discovered population of apparently icy bodies within the main asteroid belt between Mars and Jupiter, which may represent the remnants of the population which supplied the early Earth with water. Castalia will perform the first exploration of this population by characterising 133P in detail, solving the puzzle of the MBC’s activity, and making the first in situ measurements of water in the asteroid belt. In many ways a successor to ESA’s highly successful Rosetta mission, Castalia will allow direct comparison between very different classes of comet, including measuring critical isotope ratios, plasma and dust properties. It will also feature the first radar system to visit a minor body, mapping the ice in the interior. Castalia was proposed, in slightly different versions, to the ESA M4 and M5 calls within the Cosmic Vision programme. We describe the science motivation for the mission, the measurements required to achieve the scientific goals, and the proposed instrument payload and spacecraft to achieve these.
  • Journal article
    Belmonte MT, Pickering JC, Clear CP, Mairey FC, Liggins Fet al., 2018,

    The laboratory astrophysics spectroscopy programme at Imperial College London

    , Galaxies, Vol: 6, ISSN: 2075-4434

    Accurate atomic parameters, such as transition probabilities, wavelengths, and energy levels, are indispensable for the analysis of stellar spectra and the obtainment of chemical abundances. However, the quantity and quality of the existing data in many cases lie far from the current needs of astronomers, creating an acute need for laboratory measurements of matching accuracy and completeness to exploit the full potential of the very expensively acquired astrophysical spectra. The Fourier Transform Spectrometer at Imperial College London works in the vacuum ultraviolet-visible region with a resolution of 2,000,000 at 200 nm. We can acquire calibrated spectra of neutral, singly, and doubly ionized species. We collaborate with the National Institute of Standards and Technology (NIST) and the University of Lund to extend our measurements into the infrared region. The aim of this review is to explain the current capabilities of our experiment in an understandable way to bring the astronomy community closer to the field of laboratory astrophysics and encourage further dialogue between our laboratory and all those astronomers who need accurate atomic data. This exchange of ideas will help us to focus our efforts on the most urgently needed data.
  • Journal article
    Heritier K, Galand M, Henri P, Johansson FL, Beth A, Eriksson AI, Vallières X, Altwegg K, Burch JL, Carr C, Ducrot E, Hajra R, Rubin Met al., 2018,

    Plasma source and loss at comet 67P during the Rosetta mission

    , Astronomy and Astrophysics, Vol: 618, ISSN: 0004-6361

    Context.The Rosetta spacecraft provided us with a unique opportunity to study comet 67P/Churyumov-Gerasimenko from a closeperspective and over a two-year time period. Comet 67P is a weakly active comet. It was therefore unexpected to find an active anddynamic ionosphere where the cometary ions were largely dominant over the solar wind ions, even at large heliocentric distances.Aims.Our goal is to understand the different drivers of the cometary ionosphere and assess their variability over time and over thedifferent conditions encountered by the comet during the Rosetta mission.Methods.We used a multi-instrument data-based ionospheric model to compute the total ion number density at the position ofRosetta. In-situ measurements from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the Rosetta PlasmaConsortium (RPC)–Ion and Electron Sensor (IES), together with the RPC–LAngmuir Probe instrument (LAP) were used to computethe local ion total number density. The results are compared to the electron densities measured by RPC–Mutual Impedance Probe(MIP) and RPC–LAP.Results.We were able to disentangle the physical processes responsible for the formation of the cometary ions throughout thetwo-year escort phase and we evaluated their respective magnitudes. The main processes are photo-ionization and electron-impactionization. The latter is a significant source of ionization at large heliocentric distance (>2 au) and was predominant during the lastfour months of the mission. The ionosphere was occasionally subject to singular solar events, temporarily increasing the ambientenergetic electron population. Solar photons were the main ionizer near perihelion at 1.3 au from the Sun, during summer 2015.
  • Journal article
    Dougherty MK, Cao H, Khurana KK, Hunt GJ, Provan G, Kellock S, Burton ME, Burk TA, Bunce EJ, Cowley SWH, Kivelson MG, Russell CT, Southwood DJet al., 2018,

    Erratum for the Research Article “Saturn’s magnetic field revealed by the Cassini Grand Finale” by M. K. Dougherty, H. Cao, K. K. Khurana, G. J. Hunt, G. Provan, S. Kellock, M. E. Burton, T. A. Burk, E. J. Bunce, S. W. H. Cowley, M. G. Kivelson, C. T. Russell, D. J. Southwood

    , Science, Vol: 362, ISSN: 0036-8075
  • Journal article
    Sourdeval O, Gryspeerdt E, Krämer M, Goren T, Delanoë J, Afchine A, Hemmer F, Quaas Jet al., 2018,

    Ice crystal number concentration estimates from lidar–radar satellite remote sensing – Part 1: Method and evaluation

    , Atmospheric Chemistry and Physics, Vol: 18, Pages: 14327-14350, ISSN: 1680-7316

    The number concentration of cloud particles is a key quantity for understanding aerosol–cloud interactions and describing clouds in climate and numerical weather prediction models. In contrast with recent advances for liquid clouds, few observational constraints exist regarding the ice crystal number concentration (Ni). This study investigates how combined lidar–radar measurements can be used to provide satellite estimates of Ni, using a methodology that constrains moments of a parameterized particle size distribution (PSD). The operational liDAR–raDAR (DARDAR) product serves as an existing base for this method, which focuses on ice clouds with temperatures Tc < −30°C.Theoretical considerations demonstrate the capability for accurate retrievals of Ni, apart from a possible bias in the concentration in small crystals when Tc≳ − 50°C, due to the assumption of a monomodal PSD shape in the current method. This is verified via a comparison of satellite estimates to coincident in situ measurements, which additionally demonstrates the sufficient sensitivity of lidar–radar observations to Ni. Following these results, satellite estimates of Ni are evaluated in the context of a case study and a preliminary climatological analysis based on 10 years of global data. Despite a lack of other large-scale references, this evaluation shows a reasonable physical consistency in Ni spatial distribution patterns. Notably, increases in Ni are found towards cold temperatures and, more significantly, in the presence of strong updrafts, such as those related to convective or orographic uplifts. Further evaluation and improvement of this method are necessary, although these results already constitute a first encouraging step towards large-scale observational constraints for Ni. Part 2 of this series uses this new dataset to examine the controls on Ni.

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