Imperial College London

ProfessorMicheleDougherty

Faculty of Natural SciencesDepartment of Physics

Head of Department of Physics, Professor of Space Physics
 
 
 
//

Contact

 

+44 (0)20 7594 7770m.dougherty Website

 
 
//

Assistant

 

Mrs Caroline Jackson +44 (0)20 7594 7503

 
//

Location

 

Blackett 900aBlackett LaboratorySouth Kensington Campus

//

Summary

 

Publications

Publication Type
Year
to

322 results found

Carbary JF, Mitchell DG, Kollmann P, Krupp N, Roussos E, Dougherty MKet al., 2018, Energetic Electron Pitch Angle Distributions During the Cassini Final Orbits, Geophysical Research Letters, Vol: 45, Pages: 2911-2917, ISSN: 0094-8276

©2018. American Geophysical Union. All Rights Reserved. Pitch angle distributions (PADs) of very energetic electrons (110–365 keV) are examined during the ring-grazing and proximal orbits of the Cassini spacecraft, from day 320 2016 (15 November) to day 257 2017 (14 September). These repeating orbits allowed a statistical evaluation of the PADs within the magnetopause on the nightside of Saturn. Along L-shells (i.e., equatorial crossing distances of magnetic field lines) near and outside that of Titan and north of the equator, the electron fluxes were unidirectionally field-aligned going away from Saturn. Along L-shells inside Titan's and south of the equator, the electrons had bidirectional or pancake (trapping) PADs. This behavior suggests that the field lines within Titan's L-shell are generally closed, while those outside of that L-shell are generally open. This result strictly applies only to the nightside local times sampled during the final Cassini orbits, but one may infer a similar behavior at other times.

JOURNAL ARTICLE

Dougherty MK, Spilker LJ, 2018, Review of Saturn's icy moons following the Cassini mission, REPORTS ON PROGRESS IN PHYSICS, Vol: 81, ISSN: 0034-4885

JOURNAL ARTICLE

Davies EH, Masters A, Dougherty MK, Hansen KC, Coates AJ, Hunt GJet al., 2017, Swept Forward Magnetic Field Variability in High-Latitude Regions of Saturn's Magnetosphere, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 12328-12337, ISSN: 2169-9380

JOURNAL ARTICLE

Dougherty MK, 2017, CASSINI-HUYGENS Saturn in the infrared, NATURE ASTRONOMY, Vol: 1, Pages: 579-579, ISSN: 2397-3366

JOURNAL ARTICLE

Khurana KK, Fatemi S, Lindkvist J, Roussos E, Krupp N, Holmstroem M, Russell CT, Dougherty MKet al., 2017, The role of plasma slowdown in the generation of Rhea's Alfven wings, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 1778-1788, ISSN: 2169-9380

JOURNAL ARTICLE

Kinrade J, Badman SV, Bunce EJ, Tao C, Provan G, Cowley SWH, Grocott A, Gray RL, Grodent D, Kimura T, Nichols JD, Arridge CS, Radioti A, Clarke JT, Crary FJ, Pryor WR, Melin H, Baines KH, Dougherty MKet al., 2017, An isolated, bright cusp aurora at Saturn, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 6121-6138, ISSN: 2169-9380

Saturn's dayside aurora displays a number of morphological features poleward of the main emission region. We present an unusual morphology captured by the Hubble Space Telescope on 14 June 2014 (day 165), where for 2 h, Saturn's FUV aurora faded almost entirely, with the exception of a distinct emission spot at high latitude. The spot remained fixed in local time between 10 and 15 LT and moved poleward to a minimum colatitude of ~4°. It was bright and persistent, displaying intensities of up to 49 kR over a lifetime of 2 h. Interestingly, the spot constituted the entirety of the northern auroral emission, with no emissions present at any other local time—including Saturn's characteristic dawn arc, the complete absence of which is rarely observed. Solar wind parameters from propagation models, together with a Cassini magnetopause crossing and solar wind encounter, indicate that Saturn's magnetosphere was likely to have been embedded in a rarefaction region, resulting in an expanded magnetosphere configuration during the interval. We infer that the spot was sustained by reconnection either poleward of the cusp or at low latitudes under a strong component of interplanetary magnetic field transverse to the solar wind flow. The subsequent poleward motion could then arise from either reconfiguration of successive open field lines across the polar cap or convection of newly opened field lines. We also consider the possible modulation of the feature by planetary period rotating current systems.

JOURNAL ARTICLE

Masters A, Sulaiman AH, Stawarz L, Reville B, Sergis N, Fujimoto M, Burgess D, Coates AJ, Dougherty MKet al., 2017, An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations, ASTROPHYSICAL JOURNAL, Vol: 843, ISSN: 0004-637X

JOURNAL ARTICLE

Omidi N, Sulaiman AH, Kurth W, Madanian H, Cravens T, Sergis N, Dougherty MK, Edberg NJTet al., 2017, A Single Deformed Bow Shock for Titan-Saturn System, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 11058-11075, ISSN: 2169-9380

During periods of high solar wind pressure, Saturn’s bow shock is pushed inside Titan’s orbitexposing the moon and its ionosphere to the solar wind. The Cassini spacecraft’s T96 encounter with Titanoccurred during such a period and showed evidence for shocks associated with Saturn and Titan. It alsorevealed the presence of two foreshocks: one prior to the closest approach (foreshock 1) and one after(foreshock 2). Using electromagnetic hybrid (kinetic ions and fluid electrons) simulations and Cassiniobservations,we showthat the origin of foreshock 1 is tied to the formation of a single deformed bow shock forthe Titan-Saturn system. We also report the observations of a structure in foreshock 1 with properties consistentwith those of spontaneous hot flow anomalies formed in the simulations and previously observed at Earth,Venus, and Mars. The results of hybrid simulations also show the generation of oblique fast magnetosonicwaves upstream of the outbound Titan bow shock in agreement with the observations of large-amplitudemagnetosonic pulsations in foreshock 2. We also discuss the implications of a single deformed bow shock fornew particle acceleration mechanisms and also Saturn’s magnetopause and magnetosphere.

JOURNAL ARTICLE

Sergis N, Jackman CM, Thomsen MF, Krimigis SM, Mitchell DG, Hamilton DC, Dougherty MK, Krupp N, Wilson RJet al., 2017, Radial and local time structure of the Saturnian ring current, revealed by Cassini, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 1803-1815, ISSN: 2169-9380

JOURNAL ARTICLE

Sorba AM, Achilleos NA, Guio P, Arridge CS, Pilkington NM, Masters A, Sergis N, Coates AJ, Dougherty MKet al., 2017, Modeling the compressibility of Saturn's magnetosphere in response to internal and external influences, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 1572-1589, ISSN: 2169-9380

JOURNAL ARTICLE

Sulaiman AH, Gurnett DA, Halekas JS, Yates JN, Kurth WS, Dougherty MKet al., 2017, Whistler mode waves upstream of Saturn, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 227-234, ISSN: 2169-9380

JOURNAL ARTICLE

Witasse O, Sanchez-Cano B, Mays ML, Kajdic P, Opgenoorth H, Elliott HA, Richardson IG, Zouganelis I, Zender J, Wimmer-Schweingruber RF, Turc L, Taylor MGGT, Roussos E, Rouillard A, Richter I, Richardson JD, Ramstad R, Provan G, Posner A, Plaut JJ, Odstrcil D, Nilsson H, Niemenen P, Milan SE, Mandt K, Lohf H, Lester M, Lebreton J-P, Kuulkers E, Krupp N, Koenders C, James MK, Intzekara D, Holmstrom M, Hassler DM, Hall BES, Guo J, Goldstein R, Goetz C, Glassmeier KH, Genot V, Evans H, Espley J, Edberg NJT, Dougherty M, Cowley SWH, Burch J, Behar E, Barabash S, Andrews DJ, Altobelli Net al., 2017, Interplanetary coronal mass ejection observed at STEREO-A, Mars, comet 67P/Churyumov-Gerasimenko, Saturn, and New Horizons en route to Pluto: Comparison of its Forbush decreases at 1.4, 3.1, and 9.9 AU, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 7865-7890, ISSN: 2169-9380

We discuss observations of the journey throughout the Solar System of a large interplanetary coronal mass ejection (ICME) that was ejected at the Sun on 14 October 2014. The ICME hit Mars on 17 October, as observed by the Mars Express, Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), Mars Odyssey, and Mars Science Laboratory (MSL) missions, 44 h before the encounter of the planet with the Siding-Spring comet, for which the space weather context is provided. It reached comet 67P/Churyumov-Gerasimenko, which was perfectly aligned with the Sun and Mars at 3.1 AU, as observed by Rosetta on 22 October. The ICME was also detected by STEREO-A on 16 October at 1 AU, and by Cassini in the solar wind around Saturn on the 12 November at 9.9 AU. Fortuitously, the New Horizons spacecraft was also aligned with the direction of the ICME at 31.6 AU. We investigate whether this ICME has a nonambiguous signature at New Horizons. A potential detection of this ICME by Voyager 2 at 110–111 AU is also discussed. The multispacecraft observations allow the derivation of certain properties of the ICME, such as its large angular extension of at least 116°, its speed as a function of distance, and its magnetic field structure at four locations from 1 to 10 AU. Observations of the speed data allow two different solar wind propagation models to be validated. Finally, we compare the Forbush decreases (transient decreases followed by gradual recoveries in the galactic cosmic ray intensity) due to the passage of this ICME at Mars, comet 67P, and Saturn.

JOURNAL ARTICLE

Yao ZH, Coates AJ, Ray LC, Rae IJ, Grodent D, Jones GH, Dougherty MK, Owen CJ, Guo RL, Dunn WR, Radioti A, Pu ZY, Lewis GR, Waite JH, Gerard J-Cet al., 2017, Corotating Magnetic Reconnection Site in Saturn's Magnetosphere, ASTROPHYSICAL JOURNAL LETTERS, Vol: 846, ISSN: 2041-8205

Using measurements from theCassinispacecraft in Saturn’s magnetosphere, we propose a 3D physical picture of acorotating reconnection site, which can only be driven by an internally generated source. Our results demonstratethat the corotating magnetic reconnection can drive an expansion of the current sheet in Saturn’s magnetosphereand, consequently, can produce Fermi acceleration of electrons. This reconnection site lasted for longer than one ofSaturn’s rotation period. The long-lasting and corotating natures of the magnetic reconnection site at Saturnsuggest fundamentally different roles of magnetic reconnection in driving magnetospheric dynamics(e.g., theauroral precipitation)from the Earth. Our corotating reconnection picture could also potentially shed light on thefast rotating magnetized plasma environments in the solar system and beyond.

JOURNAL ARTICLE

Yao ZH, Radioti A, Rae IJ, Liu J, Grodent D, Ray LC, Badman SV, Coates AJ, Gerard J-C, Waite JH, Yates JN, Shi QQ, Wei Y, Bonfond B, Dougherty MK, Roussos E, Sergis N, Palmaerts Bet al., 2017, Mechanisms of Saturn's Near-Noon Transient Aurora: In Situ Evidence From Cassini Measurements, GEOPHYSICAL RESEARCH LETTERS, Vol: 44, Pages: 11217-11228, ISSN: 0094-8276

Although auroral emissions at giant planets have been observed for decades, the physical mechanisms of aurorae at giant planets remain unclear. One key reason is the lack of simultaneous measurements in the magnetosphere while remote sensing of the aurora. We report a dynamic auroral event identified with the Cassini Ultraviolet Imaging Spectrograph (UVIS) at Saturn on 13 July 2008 with coordinated measurements of the magnetic field and plasma in the magnetosphere. The auroral intensification was transient, only lasting for ∼30 min. The magnetic field and plasma are perturbed during the auroral intensification period. We suggest that this intensification was caused by wave mode conversion generated field-aligned currents, and we propose two potential mechanisms for the generation of this plasma wave and the transient auroral intensification. A survey of the Cassini UVIS database reveals that this type of transient auroral intensification is very common (10/11 time sequences, and ∼10% of the total images).

JOURNAL ARTICLE

Arridge CS, Eastwood JP, Jackman CM, Poh G-K, Slavin JA, Thomsen MF, Andre N, Jia X, Kidder A, Lamy L, Radioti A, Reisenfeld DB, Sergis N, Volwerk M, Walsh AP, Zarka P, Coates AJ, Dougherty MKet al., 2016, Cassini in situ observations of long-duration magnetic reconnection in Saturn's magnetotail, NATURE PHYSICS, Vol: 12, Pages: 268-271, ISSN: 1745-2473

JOURNAL ARTICLE

Arridge CS, Jasinski JM, Achilleos N, Bogdanova YV, Bunce EJ, Cowley SWH, Fazakerley AN, Khurana KK, Lamy L, Leisner JS, Roussos E, Russell CT, Zarka P, Coates AJ, Dougherty MK, Jones GH, Krimigis SM, Krupp Net al., 2016, Cassini observations of Saturn's southern polar cusp, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 121, Pages: 3006-3030, ISSN: 2169-9380

JOURNAL ARTICLE

Badman SV, Provan G, Bunce EJ, Mitchell DG, Melin H, Cowley SWH, Radioti A, Kurth WS, Pryor WR, Nichols JD, Jinks SL, Stallard TS, Brown RH, Baines KH, Dougherty MKet al., 2016, Saturn's auroral morphology and field-aligned currents during a solar wind compression, ICARUS, Vol: 263, Pages: 83-93, ISSN: 0019-1035

JOURNAL ARTICLE

Felici M, Arridge CS, Coates AJ, Badman SV, Dougherty MK, Jackman CM, Kurth WS, Melin H, Mitchell DG, Reisenfeld DB, Sergis Net al., 2016, Cassini observations of ionospheric plasma in Saturn's magnetotail lobes, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 121, Pages: 338-357, ISSN: 2169-9380

JOURNAL ARTICLE

Hunt GJ, Cowley SWH, Provan G, Bunce EJ, Alexeev II, Belenkaya ES, Kalegaev VV, Dougherty MK, Coates AJet al., 2016, Field-aligned currents in Saturn's magnetosphere: Local time dependence of southern summer currents in the dawn sector between midnight and noon, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 121, Pages: 7785-7804, ISSN: 2169-9380

JOURNAL ARTICLE

Kurth WS, Hospodarsky GB, Gurnett DA, Lamy L, Dougherty MK, Nichols J, Bunce EJ, Pryor W, Baines K, Stallard T, Melin H, Crary FJet al., 2016, Saturn kilometric radiation intensities during the Saturn auroral campaign of 2013, ICARUS, Vol: 263, Pages: 2-9, ISSN: 0019-1035

JOURNAL ARTICLE

Lai HR, Russell CT, Jia YD, Wei HY, Dougherty MKet al., 2016, Transport of magnetic flux and mass in Saturn's inner magnetosphere, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 121, Pages: 3050-3057, ISSN: 2169-9380

JOURNAL ARTICLE

Masters A, Sulaiman AH, Sergis N, Stawarz L, Fujimoto M, Coates AJ, Dougherty MKet al., 2016, SUPRATHERMAL ELECTRONS AT SATURN'S BOW SHOCK, ASTROPHYSICAL JOURNAL, Vol: 826, ISSN: 0004-637X

JOURNAL ARTICLE

Provan G, Cowley SWH, Lamy L, Bunce EJ, Hunt GJ, Zarka P, Dougherty MKet al., 2016, Planetary period oscillations in Saturn's magnetosphere: Coalescence and reversal of northern and southern periods in late northern spring, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 121, Pages: 9829-9862, ISSN: 2169-9380

JOURNAL ARTICLE

Regoli LH, Roussos E, Feyerabend M, Jones GH, Krupp N, Coates AJ, Simon S, Motschmann U, Dougherty MKet al., 2016, Access of energetic particles to Titan's exobase: A study of Cassini's T9 flyby, PLANETARY AND SPACE SCIENCE, Vol: 130, Pages: 40-53, ISSN: 0032-0633

JOURNAL ARTICLE

Roussos E, Krupp N, Mitchell DG, Paranicas C, Krimigis SM, Andriopoulou M, Palmaerts B, Kurth WS, Badman SV, Masters A, Dougherty MKet al., 2016, Quasi-periodic injections of relativistic electrons in Saturn's outer magnetosphere, ICARUS, Vol: 263, Pages: 101-116, ISSN: 0019-1035

JOURNAL ARTICLE

Russell CT, Wei HY, Cowee MM, Neubauer FM, Dougherty MKet al., 2016, Ion cyclotron waves at Titan, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 121, Pages: 2095-2103, ISSN: 2169-9380

JOURNAL ARTICLE

Sulaiman AH, Masters A, Dougherty MK, 2016, Characterization of Saturn's bow shock: Magnetic field observations of quasi-perpendicular shocks, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 121, Pages: 4425-4434, ISSN: 2169-9380

JOURNAL ARTICLE

Yates JN, Southwood DJ, Dougherty MK, Sulaiman AH, Masters A, Cowley SWH, Kivelson MG, Chen CHK, Provan G, Mitchell DG, Hospodarsky GB, Achilleos N, Sorba AM, Coates AJet al., 2016, Saturn's quasiperiodic magnetohydrodynamic waves, GEOPHYSICAL RESEARCH LETTERS, Vol: 43, Pages: 11102-11111, ISSN: 0094-8276

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

Engelhardt IAD, Wahlund J-E, Andrews DJ, Eriksson AI, Ye S, Kurth WS, Gurnett DA, Morooka MW, Farrell WM, Dougherty MKet al., 2015, Plasma regions, charged dust and field-aligned currents near Enceladus, PLANETARY AND SPACE SCIENCE, Vol: 117, Pages: 453-469, ISSN: 0032-0633

JOURNAL ARTICLE

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: respub-action=search.html&id=00029186&limit=30&person=true