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Shebanits O, Wahlund JE, Edberg NJT, Crary FJ, Wellbrock A, Andrews DJ, Vigren E, Desai RT, Coates AJ, Mandt KE, Waite JH. Ion and aerosol precursor densities in Titan's ionosphere: A multi-instrument case study. J Geophys Res Space Phys 2016; 121:10075-10090. [PMID: 31106104 PMCID: PMC6525009 DOI: 10.1002/2016ja022980] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The importance of the heavy ions and dust grains for the chemistry and aerosol formation in Titan's ionosphere has been well established in the recent years of the Cassini mission. In this study we combine independent in situ plasma (Radio Plasma and Wave Science Langmuir Probe (RPWS/LP)) and particle (Cassini Plasma Science Electron Spectrometer, Cassini Plasma Science Ion Beam Spectrometer, and Ion and Neutral Mass Spectrometer) measurements of Titan's ionosphere for selected flybys (T16, T29, T40, and T56) to produce altitude profiles of mean ion masses including heavy ions and develop a Titan-specific method for detailed analysis of the RPWS/LP measurements (applicable to all flybys) to further constrain ion charge densities and produce the first empirical estimate of the average charge of negative ions and/or dust grains. Our results reveal the presence of an ion-ion (dusty) plasma below ~1100 km altitude, with charge densities exceeding the primary ionization peak densities by a factor ≥2 in the terminator and nightside ionosphere (n e /n i ≤ 0.1). We suggest that ion-ion (dusty) plasma may also be present in the dayside ionosphere below 900 km (n e /n i < 0.5 at 1000 km altitude). The average charge of the dust grains (≥1000 amu) is estimated to be between -2.5 and -1.5 elementary charges, increasing toward lower altitudes.
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Affiliation(s)
- O. Shebanits
- Swedish Institute of Space Physics, Uppsala, Sweden
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | | | | | - F. J. Crary
- University of Colorado Boulder, Boulder, Colorado, USA
| | - A. Wellbrock
- Mullard Space Science Laboratory, University College London, London, UK
- Centre for Planetary Sciences, University College London/Birkbeck, London, UK
| | | | - E. Vigren
- Swedish Institute of Space Physics, Uppsala, Sweden
| | - R. T. Desai
- Mullard Space Science Laboratory, University College London, London, UK
- Centre for Planetary Sciences, University College London/Birkbeck, London, UK
| | - A. J. Coates
- Mullard Space Science Laboratory, University College London, London, UK
- Centre for Planetary Sciences, University College London/Birkbeck, London, UK
| | - K. E. Mandt
- Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas, USA
| | - J. H. Waite
- Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA
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2
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Nichols JD, Badman SV, Baines KH, Brown RH, Bunce EJ, Clarke JT, Cowley SWH, Crary FJ, Dougherty MK, Gérard JC, Grocott A, Grodent D, Kurth WS, Melin H, Mitchell DG, Pryor WR, Stallard TS. Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope. Geophys Res Lett 2014; 41:3323-3330. [PMID: 26074636 PMCID: PMC4459195 DOI: 10.1002/2014gl060186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 04/28/2014] [Indexed: 05/29/2023]
Abstract
We present observations of significant dynamics within two UV auroral storms observed on Saturn using the Hubble Space Telescope in April/May 2013. Specifically, we discuss bursts of auroral emission 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, bursty reconnection of lobe flux in the magnetotail, providing strong evidence that Saturn's auroral storms are caused by large-scale flux closure. We also discuss the later evolution of a similar storm and show that the emission maps to the trailing region of an energetic neutral atom enhancement. We thus identify the auroral form with the upward field-aligned continuity currents flowing into the associated partial ring current.
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Affiliation(s)
- J D Nichols
- Department of Physics and Astronomy, University of Leicester Leicester, UK
| | - S V Badman
- Department of Physics and Astronomy, University of Leicester Leicester, UK ; Department of Physics, Lancaster University Lancaster, UK
| | - K H Baines
- Space Science and Engineering Center, University of Wisconsin-Madison Madison, Wisconsin, USA
| | - R H Brown
- Lunar and Planetary Lab, University of Arizona Tucson, Arizona, USA
| | - E J Bunce
- Department of Physics and Astronomy, University of Leicester Leicester, UK
| | - J T Clarke
- Center for Space Physics, Boston University Boston, Massachusetts, USA
| | - S W H Cowley
- Department of Physics and Astronomy, University of Leicester Leicester, UK
| | - F J Crary
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder Boulder, Colorado, USA
| | - M K Dougherty
- Blackett Laboratory, Imperial College London London, UK
| | - J-C Gérard
- Laboratoire de Physique Atmospherique et Planetaire, Universite de Liege Liege, Belgium
| | - A Grocott
- Department of Physics and Astronomy, University of Leicester Leicester, UK ; Department of Physics, Lancaster University Lancaster, UK
| | - D Grodent
- Laboratoire de Physique Atmospherique et Planetaire, Universite de Liege Liege, Belgium
| | - W S Kurth
- Department of Physics and Astronomy, University of Iowa Iowa City, Iowa, USA
| | - H Melin
- Department of Physics and Astronomy, University of Leicester Leicester, UK
| | - D G Mitchell
- Applied Physics Laboratory, Johns Hopkins University Laurel, Maryland, USA
| | - W R Pryor
- Department of Science, Central Arizona College Coolidge, Arizona, USA
| | - T S Stallard
- Department of Physics and Astronomy, University of Leicester Leicester, UK
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3
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Hill TW, Thomsen MF, Tokar RL, Coates AJ, Lewis GR, Young DT, Crary FJ, Baragiola RA, Johnson RE, Dong Y, Wilson RJ, Jones GH, Wahlund JE, Mitchell DG, Horányi M. Charged nanograins in the Enceladus plume. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011ja017218] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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4
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Wellbrock A, Coates AJ, Sillanpää I, Jones GH, Arridge CS, Lewis GR, Young DT, Crary FJ, Aylward AD. Cassini observations of ionospheric photoelectrons at large distances from Titan: Implications for Titan's exospheric environment and magnetic tail. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011ja017113] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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5
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Richard MS, Cravens TE, Robertson IP, Waite JH, Wahlund JE, Crary FJ, Coates AJ. Energetics of Titan's ionosphere: Model comparisons with Cassini data. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011ja016603] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- M. S. Richard
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - T. E. Cravens
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - I. P. Robertson
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - J. H. Waite
- Southwest Research Institute; San Antonio Texas USA
| | | | - F. J. Crary
- Southwest Research Institute; San Antonio Texas USA
| | - A. J. Coates
- Mullard Space Science Laboratory, Holmbury St. Mary; University College London; Dorking, Surrey UK
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6
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Teolis BD, Jones GH, Miles PF, Tokar RL, Magee BA, Waite JH, Roussos E, Young DT, Crary FJ, Coates AJ, Johnson RE, Tseng WL, Baragiola RA. Cassini Finds an Oxygen-Carbon Dioxide Atmosphere at Saturn's Icy Moon Rhea. Science 2010; 330:1813-5. [DOI: 10.1126/science.1198366] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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7
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Thomsen MF, Reisenfeld DB, Delapp DM, Tokar RL, Young DT, Crary FJ, Sittler EC, McGraw MA, Williams JD. Survey of ion plasma parameters in Saturn's magnetosphere. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010ja015267] [Citation(s) in RCA: 207] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- M. F. Thomsen
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | | | - D. M. Delapp
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - R. L. Tokar
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - D. T. Young
- Southwest Research Institute; San Antonio Texas USA
| | - F. J. Crary
- Southwest Research Institute; San Antonio Texas USA
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8
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Ma YJ, Russell CT, Nagy AF, Toth G, Bertucci C, Dougherty MK, Neubauer FM, Wellbrock A, Coates AJ, Garnier P, Wahlund JE, Cravens TE, Crary FJ. Time-dependent global MHD simulations of Cassini T32 flyby: From magnetosphere to magnetosheath. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013676] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Y. J. Ma
- Institute of Geophysics and Planetary Physics; University of California Los Angeles; Los Angeles California USA
| | - C. T. Russell
- Institute of Geophysics and Planetary Physics; University of California Los Angeles; Los Angeles California USA
| | - A. F. Nagy
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - G. Toth
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - C. Bertucci
- Blackett Laboratory, Space and Atmospheric Physics Group; Imperial College London; London UK
| | - M. K. Dougherty
- Blackett Laboratory, Space and Atmospheric Physics Group; Imperial College London; London UK
| | - F. M. Neubauer
- Institute of Geophysics and Meteorology; University of Cologne; Cologne Germany
| | - A. Wellbrock
- Mullard Space Science Laboratory, Department of Space and Climate Physics; University College London; London UK
| | - A. J. Coates
- Mullard Space Science Laboratory, Department of Space and Climate Physics; University College London; London UK
| | - P. Garnier
- Swedish Institute of Space Physics; Uppsala Sweden
| | | | - T. E. Cravens
- Department of Physics and Astronomy; University of Kansas; Lawrence Kansas USA
| | - F. J. Crary
- Southwest Research Institute; San Antonio Texas USA
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9
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Smith HT, Shappirio M, Johnson RE, Reisenfeld D, Sittler EC, Crary FJ, McComas DJ, Young DT. Enceladus: A potential source of ammonia products and molecular nitrogen for Saturn's magnetosphere. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008ja013352] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- H. T. Smith
- Engineering Physics; University of Virginia; Charlottesville Virginia USA
- Applied Physics Laboratory; Johns Hopkins University; Laurel Maryland USA
| | - M. Shappirio
- NASA Goddard Space Flight Center; Greenbelt Maryland USA
| | - R. E. Johnson
- Engineering Physics; University of Virginia; Charlottesville Virginia USA
| | - D. Reisenfeld
- Department of Physics and Astronomy; University of Montana; Missoula Montana USA
| | - E. C. Sittler
- NASA Goddard Space Flight Center; Greenbelt Maryland USA
| | - F. J. Crary
- Division of Space Science and Engineering; Southwest Research Institute; San Antonio Texas USA
| | - D. J. McComas
- Division of Space Science and Engineering; Southwest Research Institute; San Antonio Texas USA
| | - D. T. Young
- Division of Space Science and Engineering; Southwest Research Institute; San Antonio Texas USA
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10
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Hill TW, Thomsen MF, Henderson MG, Tokar RL, Coates AJ, McAndrews HJ, Lewis GR, Mitchell DG, Jackman CM, Russell CT, Dougherty MK, Crary FJ, Young DT. Plasmoids in Saturn's magnetotail. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007ja012626] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- T. W. Hill
- Physics and Astronomy Department; Rice University; Houston Texas USA
| | - M. F. Thomsen
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | | | - R. L. Tokar
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - A. J. Coates
- Mullard Space Science Laboratory; University College London; Surrey UK
| | | | - G. R. Lewis
- Mullard Space Science Laboratory; University College London; Surrey UK
| | - D. G. Mitchell
- Johns Hopkins University; Applied Physics Laboratory; Laurel Maryland USA
| | | | - C. T. Russell
- Institute of Geophysics; University of California; Los Angeles California USA
| | | | - F. J. Crary
- Space Science and Engineering; Southwest Research Institute; San Antonio Texas USA
| | - D. T. Young
- Space Science and Engineering; Southwest Research Institute; San Antonio Texas USA
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11
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Thomsen MF, DiLorenzo JP, McComas DJ, Young DT, Crary FJ, Delapp D, Reisenfeld D, Andre N. Assessment of the magnetospheric contribution to the suprathermal ions in Saturn's foreshock region. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006ja012084] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- M. F. Thomsen
- Space Science and Applications; Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - J. P. DiLorenzo
- Space Science and Applications; Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - D. J. McComas
- Instrumentation and Space Research Division; Southwest Research Institute; San Antonio Texas USA
| | - D. T. Young
- Instrumentation and Space Research Division; Southwest Research Institute; San Antonio Texas USA
| | - F. J. Crary
- Instrumentation and Space Research Division; Southwest Research Institute; San Antonio Texas USA
| | - D. Delapp
- Space Science and Applications; Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - D.B. Reisenfeld
- Department of Physics and Astronomy; University of Montana; Missoula Montana USA
| | - N. Andre
- Mullard Space Science Laboratory; University College London; Holmbury-St. Mary UK
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12
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Abstract
Titan's lower atmosphere has long been known to harbor organic aerosols (tholins) presumed to have been formed from simple molecules, such as methane and nitrogen (CH4 and N2). Up to now, it has been assumed that tholins were formed at altitudes of several hundred kilometers by processes as yet unobserved. Using measurements from a combination of mass/charge and energy/charge spectrometers on the Cassini spacecraft, we have obtained evidence for tholin formation at high altitudes (approximately 1000 kilometers) in Titan's atmosphere. The observed chemical mix strongly implies a series of chemical reactions and physical processes that lead from simple molecules (CH4 and N2) to larger, more complex molecules (80 to 350 daltons) to negatively charged massive molecules (approximately 8000 daltons), which we identify as tholins. That the process involves massive negatively charged molecules and aerosols is completely unexpected.
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Affiliation(s)
- J H Waite
- Space Science and Engineering Division, Southwest Research Institute (SWRI), 6220 Culebra Road, San Antonio, TX 78238, USA.
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13
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Gérard JC, Grodent D, Cowley SWH, Mitchell DG, Kurth WS, Clarke JT, Bunce EJ, Nichols JD, Dougherty MK, Crary FJ, Coates AJ. Saturn's auroral morphology and activity during quiet magnetospheric conditions. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2006ja011965] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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14
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Tokar RL, Johnson RE, Hill TW, Pontius DH, Kurth WS, Crary FJ, Young DT, Thomsen MF, Reisenfeld DB, Coates AJ, Lewis GR, Sittler EC, Gurnett DA. The Interaction of the Atmosphere of Enceladus with Saturn's Plasma. Science 2006; 311:1409-12. [PMID: 16527967 DOI: 10.1126/science.1121061] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 x 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data are consistent with ion formation via charge exchange and pickup by Saturn's magnetic field. The charge exchange occurs between neutrals in the Enceladus atmosphere and corotating ions in Saturn's inner magnetosphere. Pickup ions are observed near Enceladus, and a total mass loading rate of about 100 kilograms per second (3 x 10(27) H(2)O molecules per second) is inferred.
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Affiliation(s)
- R L Tokar
- Space Science and Applications, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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15
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Young DT, Berthelier JJ, Blanc M, Burch JL, Bolton S, Coates AJ, Crary FJ, Goldstein R, Grande M, Hill TW, Johnson RE, Baragiola RA, Kelha V, McComas DJ, Mursula K, Sittler EC, Svenes KR, Szegö K, Tanskanen P, Thomsen MF, Bakshi S, Barraclough BL, Bebesi Z, Delapp D, Dunlop MW, Gosling JT, Furman JD, Gilbert LK, Glenn D, Holmlund C, Illiano JM, Lewis GR, Linder DR, Maurice S, McAndrews HJ, Narheim BT, Pallier E, Reisenfeld D, Rymer AM, Smith HT, Tokar RL, Vilppola J, Zinsmeyer C. Composition and Dynamics of Plasma in Saturn's Magnetosphere. Science 2005; 307:1262-6. [PMID: 15731443 DOI: 10.1126/science.1106151] [Citation(s) in RCA: 257] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where RS is the radial distance from the center of Saturn), whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with approximately 3% N+. Over the A and B rings, we found an ionosphere in which O2+ and O+ are dominant, which suggests the possible existence of a layer of O2 gas similar to the atmospheres of Europa and Ganymede.
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Affiliation(s)
- D T Young
- Southwest Research Institute, San Antonio, TX 78238, USA.
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16
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Kurth WS, Gurnett DA, Clarke JT, Zarka P, Desch MD, Kaiser ML, Cecconi B, Lecacheux A, Farrell WM, Galopeau P, Gérard JC, Grodent D, Prangé R, Dougherty MK, Crary FJ. An Earth-like correspondence between Saturn's auroral features and radio emission. Nature 2005; 433:722-5. [PMID: 15716947 DOI: 10.1038/nature03334] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2004] [Accepted: 12/04/2004] [Indexed: 11/09/2022]
Abstract
Saturn is a source of intense kilometre-wavelength radio emissions that are believed to be associated with its polar aurorae, and which provide an important remote diagnostic of its magnetospheric activity. Previous observations implied that the radio emission originated in the polar regions, and indicated a strong correlation with solar wind dynamic pressure. The radio source also appeared to be fixed near local noon and at the latitude of the ultraviolet aurora. There have, however, been no observations relating the radio emissions to detailed auroral structures. Here we report measurements of the radio emissions, which, along with high-resolution images of Saturn's ultraviolet auroral emissions, suggest that although there are differences in the global morphology of the aurorae, Saturn's radio emissions exhibit an Earth-like correspondence between bright auroral features and the radio emissions. This demonstrates the universality of the mechanism that results in emissions near the electron cyclotron frequency narrowly beamed at large angles to the magnetic field.
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Affiliation(s)
- W S Kurth
- Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242, USA.
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17
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Crary FJ, Clarke JT, Dougherty MK, Hanlon PG, Hansen KC, Steinberg JT, Barraclough BL, Coates AJ, Gérard JC, Grodent D, Kurth WS, Mitchell DG, Rymer AM, Young DT. Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae. Nature 2005; 433:720-2. [PMID: 15716946 DOI: 10.1038/nature03333] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2004] [Accepted: 12/27/2004] [Indexed: 11/09/2022]
Abstract
The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms, but the relation between the solar wind and the dynamics of the outer planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system, whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere.
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Affiliation(s)
- F J Crary
- Southwest Research Institute, Culebra Road, San Antonio, Texas 78288, USA.
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18
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McComas DJ, Schwadron NA, Crary FJ, Elliott HA, Young DT, Gosling JT, Thomsen MF, Sittler E, Berthelier JJ, Szego K, Coates AJ. The interstellar hydrogen shadow: Observations of interstellar pickup ions beyond Jupiter. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003ja010217] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | | | - F. J. Crary
- Southwest Research Institute; San Antonio Texas USA
| | | | - D. T. Young
- Southwest Research Institute; San Antonio Texas USA
| | - J. T. Gosling
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - M. F. Thomsen
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - E. Sittler
- NASA Goddard Space Flight Center; Greenbelt Maryland USA
| | | | - K. Szego
- KFKI Research Institute for Particles and Nuclear Physics; Budapest Hungary
| | - A. J. Coates
- Mullard Space Science Laboratory; University College London; Surrey UK
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19
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Gladstone GR, Waite JH, Grodent D, Lewis WS, Crary FJ, Elsner RF, Weisskopf MC, Majeed T, Jahn JM, Bhardwaj A, Clarke JT, Young DT, Dougherty MK, Espinosa SA, Cravens TE. A pulsating auroral X-ray hot spot on Jupiter. Nature 2002; 415:1000-3. [PMID: 11875561 DOI: 10.1038/4151000a] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Jupiter's X-ray aurora has been thought to be excited by energetic sulphur and oxygen ions precipitating from the inner magnetosphere into the planet's polar regions. Here we report high-spatial-resolution observations that demonstrate that most of Jupiter's northern auroral X-rays come from a 'hot spot' located significantly poleward of the latitudes connected to the inner magnetosphere. The hot spot seems to be fixed in magnetic latitude and longitude and occurs in a region where anomalous infrared and ultraviolet emissions have also been observed. We infer from the data that the particles that excite the aurora originate in the outer magnetosphere. The hot spot X-rays pulsate with an approximately 45-min period, a period similar to that reported for high-latitude radio and energetic electron bursts observed by near-Jupiter spacecraft. These results invalidate the idea that jovian auroral X-ray emissions are mainly excited by steady precipitation of energetic heavy ions from the inner magnetosphere. Instead, the X-rays seem to result from currently unexplained processes in the outer magnetosphere that produce highly localized and highly variable emissions over an extremely wide range of wavelengths.
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Affiliation(s)
- G R Gladstone
- Southwest Research Institute, San Antonio, Texas 78228, USA.
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Kurth WS, Gurnett DA, Hospodarsky GB, Farrell WM, Roux A, Dougherty MK, Joy SP, Kivelson MG, Walker RJ, Crary FJ, Alexander CJ. The dusk flank of Jupiter's magnetosphere. Nature 2002; 415:991-4. [PMID: 11875558 DOI: 10.1038/415991a] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Limited single-spacecraft observations of Jupiter's magnetopause have been used to infer that the boundary moves inward or outward in response to variations in the dynamic pressure of the solar wind. At Earth, multiple-spacecraft observations have been implemented to understand the physics of how this motion occurs, because they can provide a snapshot of a transient event in progress. Here we present a set of nearly simultaneous two-point measurements of the jovian magnetopause at a time when the jovian magnetopause was in a state of transition from a relatively larger to a relatively smaller size in response to an increase in solar-wind pressure. The response of Jupiter's magnetopause is very similar to that of the Earth, confirming that the understanding built on studies of the Earth's magnetosphere is valid. The data also reveal evidence for a well-developed boundary layer just inside the magnetopause.
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Affiliation(s)
- W S Kurth
- Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA.
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Crary FJ, Bagenal F, Frank LA, Paterson WR. Galileo plasma spectrometer measurements of composition and temperature in the Io plasma torus. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/1998ja900003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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