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Smith AW, Jackman CM, Thomsen MF. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2016; 121:2984-3005. [PMID: 27867795 PMCID: PMC5111619 DOI: 10.1002/2015ja022005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 02/01/2016] [Accepted: 03/03/2016] [Indexed: 05/04/2023]
Abstract
Reconnection within planetary magnetotails is responsible for locally energizing particles and changing the magnetic topology. Its role in terms of global magnetospheric dynamics can involve changing the mass and flux content of the magnetosphere. We have identified reconnection related events in spacecraft magnetometer data recorded during Cassini's exploration of Saturn's magnetotail. The events are identified from deflections in the north-south component of the magnetic field, significant above a background level. Data were selected to provide full tail coverage, encompassing the dawn and dusk flanks as well as the deepest midnight orbits. Overall 2094 reconnection related events were identified, with an average rate of 5.0 events per day. The majority of events occur in clusters (within 3 h of other events). We examine changes in this rate in terms of local time and latitude coverage, taking seasonal effects into account. The observed reconnection rate peaks postmidnight with more infrequent but steady loss seen on the dusk flank. We estimate the mass loss from the event catalog and find it to be insufficient to balance the input from the moon Enceladus. Several reasons for this discrepancy are discussed. The reconnection X line location appears to be highly variable, though a statistical separation between events tailward and planetward of the X line is observed at a radial distance of between 20 and 30RS downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.
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Affiliation(s)
- A. W. Smith
- Department of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
| | - C. M. Jackman
- Department of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
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Felici M, Arridge CS, Coates AJ, Badman SV, Dougherty MK, Jackman CM, Kurth WS, Melin H, Mitchell DG, Reisenfeld DB, Sergis N. Cassini observations of ionospheric plasma in Saturn's magnetotail lobes. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2016; 121:338-357. [PMID: 27610291 PMCID: PMC4994772 DOI: 10.1002/2015ja021648] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 12/13/2015] [Accepted: 12/28/2015] [Indexed: 05/20/2023]
Abstract
Studies of Saturn's magnetosphere with the Cassini mission have established the importance of Enceladus as the dominant mass source for Saturn's magnetosphere. It is well known that the ionosphere is an important mass source at Earth during periods of intense geomagnetic activity, but lesser attention has been dedicated to study the ionospheric mass source at Saturn. In this paper we describe a case study of data from Saturn's magnetotail, when Cassini was located at ≃ 2200 h Saturn local time at 36 RS from Saturn. During several entries into the magnetotail lobe, tailward flowing cold electrons and a cold ion beam were observed directly adjacent to the plasma sheet and extending deeper into the lobe. The electrons and ions appear to be dispersed, dropping to lower energies with time. The composition of both the plasma sheet and lobe ions show very low fluxes (sometimes zero within measurement error) of water group ions. The magnetic field has a swept-forward configuration which is atypical for this region, and the total magnetic field strength is larger than expected at this distance from the planet. Ultraviolet auroral observations show a dawn brightening, and upstream heliospheric models suggest that the magnetosphere is being compressed by a region of high solar wind ram pressure. We interpret this event as the observation of ionospheric outflow in Saturn's magnetotail. We estimate a number flux between (2.95 ± 0.43) × 109 and (1.43 ± 0.21) × 1010 cm-2 s-1, 1 or about 2 orders of magnitude larger than suggested by steady state MHD models, with a mass source between 1.4 ×102 and 1.1 ×103 kg/s. After considering several configurations for the active atmospheric regions, we consider as most probable the main auroral oval, with associated mass source between 49.7 ±13.4 and 239.8 ±64.8 kg/s for an average auroral oval, and 10 ±4 and 49 ±23 kg/s for the specific auroral oval morphology found during this event. It is not clear how much of this mass is trapped within the magnetosphere and how much is lost to the solar wind.
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Affiliation(s)
- M. Felici
- Mullard Space Science LaboratoryUniversity College LondonDorkingUK
- Centre for Planetary Sciences at UCL/BirkbeckLondonUK
- Department of PhysicsLancaster UniversityLancasterUK
| | - C. S. Arridge
- Department of PhysicsLancaster UniversityLancasterUK
| | - A. J. Coates
- Mullard Space Science LaboratoryUniversity College LondonDorkingUK
- Centre for Planetary Sciences at UCL/BirkbeckLondonUK
| | - S. V. Badman
- Department of PhysicsLancaster UniversityLancasterUK
| | - M. K. Dougherty
- Space and Atmospheric Physics Group, The Blackett LaboratoryImperial College LondonLondonUK
| | - C. M. Jackman
- Department of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
| | - W. S. Kurth
- Department of Physics and AstronomyUniversity of IowaIowa CityIowaUSA
| | - H. Melin
- Department of Physics and AstronomyUniversity of LeicesterLeicesterUK
| | - D. G. Mitchell
- The Johns Hopkins University Applied Physics LaboratoryLaurelMarylandUSA
| | - D. B. Reisenfeld
- Department of Physics and AstronomyUniversity of MontanaMissoulaMontanaUSA
| | - N. Sergis
- Mullard Space Science LaboratoryUniversity College LondonDorkingUK
- Office for Space ResearchAcademy of AthensAthensGreece
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Jackman CM, Thomsen MF, Mitchell DG, Sergis N, Arridge CS, Felici M, Badman SV, Paranicas C, Jia X, Hospodarksy GB, Andriopoulou M, Khurana KK, Smith AW, Dougherty MK. Field dipolarization in Saturn's magnetotail with planetward ion flows and energetic particle flow bursts: Evidence of quasi-steady reconnection. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2015; 120:3603-3617. [PMID: 27570722 PMCID: PMC4981121 DOI: 10.1002/2015ja020995] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 04/01/2015] [Accepted: 04/01/2015] [Indexed: 05/20/2023]
Abstract
We present a case study of an event from 20 August (day 232) of 2006, when the Cassini spacecraft was sampling the region near 32 RS and 22 h LT in Saturn's magnetotail. Cassini observed a strong northward-to-southward turning of the magnetic field, which is interpreted as the signature of dipolarization of the field as seen by the spacecraft planetward of the reconnection X line. This event was accompanied by very rapid (up to ~1500 km s-1) thermal plasma flow toward the planet. At energies above 28 keV, energetic hydrogen and oxygen ion flow bursts were observed to stream planetward from a reconnection site downtail of the spacecraft. Meanwhile, a strong field-aligned beam of energetic hydrogen was also observed to stream tailward, likely from an ionospheric source. Saturn kilometric radiation emissions were stimulated shortly after the observation of the dipolarization. We discuss the field, plasma, energetic particle, and radio observations in the context of the impact this reconnection event had on global magnetospheric dynamics.
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Affiliation(s)
- C. M. Jackman
- School of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
| | | | - D. G. Mitchell
- The Johns Hopkins University Applied Physics LaboratoryLaurelMarylandUSA
| | | | | | - M. Felici
- Department of PhysicsLancaster UniversityBailriggUK
- Mullard Space Science LaboratoryUniversity College LondonSurreyUK
- The Centre for Planetary Sciences at UCL/BirkbeckLondonUK
| | - S. V. Badman
- Department of PhysicsLancaster UniversityBailriggUK
| | - C. Paranicas
- The Johns Hopkins University Applied Physics LaboratoryLaurelMarylandUSA
| | - X. Jia
- Atmospheric, Oceanic and Space SciencesUniversity of MichiganAnn ArborMichiganUSA
| | - G. B. Hospodarksy
- Department of Physics and AstronomyUniversity of IowaIowa CityIowaUSA
| | - M. Andriopoulou
- Space Research InstituteAustrian Academy of SciencesGrazAustria
| | - K. K. Khurana
- Institute of Geophysics and Planetary PhysicsUniversity of CaliforniaLos AngelesCaliforniaUSA
| | - A. W. Smith
- School of Physics and AstronomyUniversity of SouthamptonSouthamptonUK
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Szego K, Nemeth Z, Erdos G, Foldy L, Bebesi Z, Thomsen M, Delapp D. Location of the magnetodisk in the nightside outer magnetosphere of Saturn near equinox based on ion densities. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012ja017817] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Thomsen MF, Roussos E, Andriopoulou M, Kollmann P, Arridge CS, Paranicas CP, Gurnett DA, Powell RL, Tokar RL, Young DT. Saturn's inner magnetospheric convection pattern: Further evidence. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011ja017482] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Jia X, Hansen KC, Gombosi TI, Kivelson MG, Tóth G, DeZeeuw DL, Ridley AJ. Magnetospheric configuration and dynamics of Saturn's magnetosphere: A global MHD simulation. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012ja017575] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Jia X, Kivelson MG, Gombosi TI. Driving Saturn's magnetospheric periodicities from the upper atmosphere/ionosphere. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011ja017367] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Jackman CM, Slavin JA, Cowley SWH. Cassini observations of plasmoid structure and dynamics: Implications for the role of magnetic reconnection in magnetospheric circulation at Saturn. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011ja016682] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- C. M. Jackman
- Department of Physics and Astronomy; University College London; London UK
| | - J. A. Slavin
- NASA Goddard Space Flight Center; Greenbelt Maryland USA
| | - S. W. H. Cowley
- Department of Physics and Astronomy; University of Leicester; Leicester UK
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Jackman CM, Arridge CS. Statistical properties of the magnetic field in the Kronian magnetotail lobes and current sheet. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010ja015973] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- C. M. Jackman
- Blackett Laboratory; Imperial College London; London UK
| | - C. S. Arridge
- Mullard Space Science Laboratory; University College London; Dorking UK
- Centre for Planetary Sciences at UCL/Birkbeck; London UK
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Bagenal F, Delamere PA. Flow of mass and energy in the magnetospheres of Jupiter and Saturn. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010ja016294] [Citation(s) in RCA: 222] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Fran Bagenal
- Laboratory for Atmospheric and Space Physics; University of Colorado at Boulder; Boulder Colorado USA
| | - Peter A. Delamere
- Laboratory for Atmospheric and Space Physics; University of Colorado at Boulder; Boulder Colorado USA
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Jackman CM, Arridge CS, Slavin JA, Milan SE, Lamy L, Dougherty MK, Coates AJ. In situ observations of the effect of a solar wind compression on Saturn's magnetotail. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010ja015312] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- C. M. Jackman
- Blackett Laboratory; Imperial College London; London UK
| | - C. S. Arridge
- Mullard Space Science Laboratory, Department of Space and Climate Physics; University College London; Dorking UK
- The Centre for Planetary Sciences at UCL/Birkbeck; London UK
| | - J. A. Slavin
- Heliophysics Science Division; NASA Goddard Space Flight Center; Greenbelt Maryland USA
| | - S. E. Milan
- Radio and Space Plasma Physics Group; University of Leicester; Leicester UK
| | - L. Lamy
- Blackett Laboratory; Imperial College London; London UK
| | | | - A. J. Coates
- Mullard Space Science Laboratory, Department of Space and Climate Physics; University College London; Dorking UK
- The Centre for Planetary Sciences at UCL/Birkbeck; London UK
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Zieger B, Hansen KC, Gombosi TI, De Zeeuw DL. Periodic plasma escape from the mass-loaded Kronian magnetosphere. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009ja014951] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- B. Zieger
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - K. C. Hansen
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - T. I. Gombosi
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
| | - D. L. De Zeeuw
- Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
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Jackman CM, Lamy L, Freeman MP, Zarka P, Cecconi B, Kurth WS, Cowley SWH, Dougherty MK. On the character and distribution of lower-frequency radio emissions at Saturn and their relationship to substorm-like events. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013997] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- C. M. Jackman
- Blackett Laboratory; Imperial College London; London UK
| | - L. Lamy
- LESIA, Observatoire de Paris; Université Paris Diderot, UPMC, CNRS; Meudon France
| | | | - P. Zarka
- LESIA, Observatoire de Paris; Université Paris Diderot, UPMC, CNRS; Meudon France
| | - B. Cecconi
- LESIA, Observatoire de Paris; Université Paris Diderot, UPMC, CNRS; Meudon France
| | - W. S. Kurth
- Department of Physics and Astronomy; University of Iowa; Iowa City Iowa USA
| | - S. W. H. Cowley
- Department of Physics and Astronomy; University of Leicester; Leicester UK
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Jackman CM, Arridge CS, Krupp N, Bunce EJ, Mitchell DG, McAndrews HJ, Dougherty MK, Russell CT, Achilleos N, Jones GH, Coates AJ. A multi-instrument view of tail reconnection at Saturn. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008ja013592] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- C. M. Jackman
- Space and Atmospheric Physics Group; Imperial College London; London UK
| | - C. S. Arridge
- Mullard Space Science Laboratory; University College London; Surrey UK
- Centre for Planetary Sciences; University College London; London UK
| | - N. Krupp
- Max Planck Institute for Solar System Research; Katlenburg-Lindau Germany
| | - E. J. Bunce
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | - D. G. Mitchell
- Applied Physics Laboratory; Johns Hopkins University; Baltimore Maryland USA
| | | | - M. K. Dougherty
- Space and Atmospheric Physics Group; Imperial College London; London UK
| | - C. T. Russell
- Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
| | - N. Achilleos
- Centre for Planetary Sciences; University College London; London UK
- Department of Physics and Astronomy; University College London; London UK
| | - G. H. Jones
- Mullard Space Science Laboratory; University College London; Surrey UK
- Centre for Planetary Sciences; University College London; London UK
| | - A. J. Coates
- Mullard Space Science Laboratory; University College London; Surrey UK
- Centre for Planetary Sciences; University College London; London UK
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