1
|
Andrews DJ, Cecconi B, Cowley SWH, Dougherty MK, Lamy L, Provan G, Zarka P. Planetary period oscillations in Saturn's magnetosphere: Evidence in magnetic field phase data for rotational modulation of Saturn kilometric radiation emissions. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011ja016636] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- D. J. Andrews
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | - B. Cecconi
- LESIA, Observatoire de Paris, CNRS, UPMC; Université Paris VII - Denis Diderot; Meudon France
| | - S. W. H. Cowley
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | | | - L. Lamy
- LESIA, Observatoire de Paris, CNRS, UPMC; Université Paris VII - Denis Diderot; Meudon France
| | - G. Provan
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | - P. Zarka
- LESIA, Observatoire de Paris, CNRS, UPMC; Université Paris VII - Denis Diderot; Meudon France
| |
Collapse
|
2
|
Lamy L, Cecconi B, Prangé R, Zarka P, Nichols JD, Clarke JT. An auroral oval at the footprint of Saturn's kilometric radio sources, colocated with the UV aurorae. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2009ja014401] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- L. Lamy
- LESIA, Observatoire de Paris, UPMC, CNRS; Université Paris Diderot; Meudon France
- Space and Atmospheric Physics Group, Blackett Laboratory; Imperial College London; London UK
| | - B. Cecconi
- LESIA, Observatoire de Paris, UPMC, CNRS; Université Paris Diderot; Meudon France
| | - R. Prangé
- LESIA, Observatoire de Paris, UPMC, CNRS; Université Paris Diderot; Meudon France
| | - P. Zarka
- LESIA, Observatoire de Paris, UPMC, CNRS; Université Paris Diderot; Meudon France
| | - J. D. Nichols
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | - J. T. Clarke
- Center for Space Physics; Boston University; Boston Massachusetts USA
| |
Collapse
|
3
|
Clarke JT, Nichols J, Gérard JC, Grodent D, Hansen KC, Kurth W, Gladstone GR, Duval J, Wannawichian S, Bunce E, Cowley SWH, Crary F, Dougherty M, Lamy L, Mitchell D, Pryor W, Retherford K, Stallard T, Zieger B, Zarka P, Cecconi B. Response of Jupiter's and Saturn's auroral activity to the solar wind. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013694] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- J. T. Clarke
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - J. Nichols
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | | | - D. Grodent
- LPAP; Université de Liège; Liege Belgium
| | - K. C. Hansen
- AOSS Department; University of Michigan; Ann Arbor Michigan USA
| | - W. Kurth
- Department of Physics and Astronomy; University of Iowa; Iowa City Iowa USA
| | | | - J. Duval
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - S. Wannawichian
- Center for Space Physics; Boston University; Boston Massachusetts USA
| | - E. Bunce
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | - S. W. H. Cowley
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | - F. Crary
- Southwest Research Institute; San Antonio Texas USA
| | - M. Dougherty
- Blackett Laboratory; Imperial College; London UK
| | - L. Lamy
- LESIA, Observatoire de Paris; UPMC, CNRS, Université Paris Diderot; Meudon France
| | - D. Mitchell
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| | - W. Pryor
- Department of Science; Central Arizona College; Coolidge Arizona USA
| | | | - T. Stallard
- Department of Physics and Astronomy; University of Leicester; Leicester UK
| | - B. Zieger
- AOSS Department; University of Michigan; Ann Arbor Michigan USA
| | - P. Zarka
- LESIA, Observatoire de Paris; UPMC, CNRS, Université Paris Diderot; Meudon France
| | - B. Cecconi
- LESIA, Observatoire de Paris; UPMC, CNRS, Université Paris Diderot; Meudon France
| |
Collapse
|
4
|
Cecconi B, Lamy L, Zarka P, Prangé R, Kurth WS, Louarn P. Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008ja013830] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- B. Cecconi
- LESIA, Observatoire de Paris; CNRS, UPMC, Université Paris Diderot; Meudon France
| | - L. Lamy
- LESIA, Observatoire de Paris; CNRS, UPMC, Université Paris Diderot; Meudon France
| | - P. Zarka
- LESIA, Observatoire de Paris; CNRS, UPMC, Université Paris Diderot; Meudon France
| | - R. Prangé
- LESIA, Observatoire de Paris; CNRS, UPMC, Université Paris Diderot; Meudon France
| | - W. S. Kurth
- Department of Physics and Astronomy; University of Iowa; Iowa City Iowa USA
| | - P. Louarn
- Centre d'Etude Spatiale des Rayonnements; Université Paul Saltier, CNRS; Toulouse France
| |
Collapse
|
5
|
Complex structure within Saturn's infrared aurora. Nature 2008; 456:214-7. [PMID: 19005549 DOI: 10.1038/nature07440] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Accepted: 09/12/2008] [Indexed: 11/09/2022]
Abstract
The majority of planetary aurorae are produced by electrical currents flowing between the ionosphere and the magnetosphere which accelerate energetic charged particles that hit the upper atmosphere. At Saturn, these processes collisionally excite hydrogen, causing ultraviolet emission, and ionize the hydrogen, leading to H(3)(+) infrared emission. Although the morphology of these aurorae is affected by changes in the solar wind, the source of the currents which produce them is a matter of debate. Recent models predict only weak emission away from the main auroral oval. Here we report images that show emission both poleward and equatorward of the main oval (separated by a region of low emission). The extensive polar emission is highly variable with time, and disappears when the main oval has a spiral morphology; this suggests that although the polar emission may be associated with minor increases in the dynamic pressure from the solar wind, it is not directly linked to strong magnetospheric compressions. This aurora appears to be unique to Saturn and cannot be explained using our current understanding of Saturn's magnetosphere. The equatorward arc of emission exists only on the nightside of the planet, and arises from internal magnetospheric processes that are currently unknown.
Collapse
|
6
|
Stallard T, Miller S, Melin H, Lystrup M, Cowley SWH, Bunce EJ, Achilleos N, Dougherty M. Jovian-like aurorae on Saturn. Nature 2008; 453:1083-5. [PMID: 18563160 DOI: 10.1038/nature07077] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Accepted: 04/29/2008] [Indexed: 11/09/2022]
Abstract
Planetary aurorae are formed by energetic charged particles streaming along the planet's magnetic field lines into the upper atmosphere from the surrounding space environment. Earth's main auroral oval is formed through interactions with the solar wind, whereas that at Jupiter is formed through interactions with plasma from the moon Io inside its magnetic field (although other processes form aurorae at both planets). At Saturn, only the main auroral oval has previously been observed and there remains much debate over its origin. Here we report the discovery of a secondary oval at Saturn that is approximately 25 per cent as bright as the main oval, and we show this to be caused by interaction with the middle magnetosphere around the planet. This is a weak equivalent of Jupiter's main oval, its relative dimness being due to the lack of as large a source of ions as Jupiter's volcanic moon Io. This result suggests that differences seen in the auroral emissions from Saturn and Jupiter are due to scaling differences in the conditions at each of these two planets, whereas the underlying formation processes are the same.
Collapse
Affiliation(s)
- Tom Stallard
- Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK.
| | | | | | | | | | | | | | | |
Collapse
|
7
|
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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
8
|
Sittler EC, Blanc MF, Richardson JD. Proposed model for Saturn's auroral response to the solar wind: Centrifugal instability model. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005ja011191] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
9
|
Esposito LW, Colwell JE, Larsen K, McClintock WE, Stewart AIF, Hallett JT, Shemansky DE, Ajello JM, Hansen CJ, Hendrix AR, West RA, Keller HU, Korth A, Pryor WR, Reulke R, Yung YL. Ultraviolet Imaging Spectroscopy Shows an Active Saturnian System. Science 2005; 307:1251-5. [PMID: 15604361 DOI: 10.1126/science.1105606] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Neutral oxygen in the saturnian system shows variability, and the total number of oxygen atoms peaks at 4 x 10(34). Saturn's aurora brightens in response to solar-wind forcing, and the auroral spectrum resembles Jupiter's. Phoebe's surface shows variable water-ice content, and the data indicate it originated in the outer solar system. Saturn's rings also show variable water abundance, with the purest ice in the outermost A ring. This radial variation is consistent with initially pure water ice bombarded by meteors, but smaller radial structures may indicate collisional transport and recent renewal events in the past 10(7) to 10(8) years.
Collapse
Affiliation(s)
- Larry W Esposito
- University of Colorado, Laboratory for Atmospheric and Space Physics, 234 Innovation Drive, Boulder, CO 80303-7814, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Clarke JT, Gérard JC, Grodent D, Wannawichian S, Gustin J, Connerney J, Crary F, Dougherty M, Kurth W, Cowley SWH, Bunce EJ, Hill T, Kim J. Morphological differences between Saturn's ultraviolet aurorae and those of Earth and Jupiter. Nature 2005; 433:717-9. [PMID: 15716945 DOI: 10.1038/nature03331] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2004] [Accepted: 12/22/2004] [Indexed: 11/10/2022]
Abstract
It has often been stated that Saturn's magnetosphere and aurorae are intermediate between those of Earth, where the dominant processes are solar wind driven, and those of Jupiter, where processes are driven by a large source of internal plasma. But this view is based on information about Saturn that is far inferior to what is now available. Here we report ultraviolet images of Saturn, which, when combined with simultaneous Cassini measurements of the solar wind and Saturn kilometric radio emission, demonstrate that its aurorae differ morphologically from those of both Earth and Jupiter. Saturn's auroral emissions vary slowly; some features appear in partial corotation whereas others are fixed to the solar wind direction; the auroral oval shifts quickly in latitude; and the aurora is often not centred on the magnetic pole nor closed on itself. In response to a large increase in solar wind dynamic pressure Saturn's aurora brightened dramatically, the brightest auroral emissions moved to higher latitudes, and the dawn side polar regions were filled with intense emissions. The brightening is reminiscent of terrestrial aurorae, but the other two variations are not. Rather than being intermediate between the Earth and Jupiter, Saturn's auroral emissions behave fundamentally differently from those at the other planets.
Collapse
Affiliation(s)
- J T Clarke
- Boston University, 725 Commonwealth Avenue, Boston, Massachusetts 02215, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
|
12
|
Badman SV, Bunce EJ, Clarke JT, Cowley SWH, Gérard JC, Grodent D, Milan SE. Open flux estimates in Saturn's magnetosphere during the January 2004 Cassini-HST campaign, and implications for reconnection rates. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2005ja011240] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
13
|
|
14
|
Cowley SWH. Reconnection in a rotation-dominated magnetosphere and its relation to Saturn's auroral dynamics. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004ja010796] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
15
|
Gérard JC, Bunce EJ, Grodent D, Cowley SWH, Clarke JT, Badman SV. Signature of Saturn's auroral cusp: Simultaneous Hubble Space Telescope FUV observations and upstream solar wind monitoring. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2005ja011094] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
16
|
Jackman CM. Interplanetary conditions and magnetospheric dynamics during the Cassini orbit insertion fly-through of Saturn's magnetosphere. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2005ja011054] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
17
|
Prangé R, Pallier L, Hansen KC, Howard R, Vourlidas A, Courtin R, Parkinson C. An interplanetary shock traced by planetary auroral storms from the Sun to Saturn. Nature 2004; 432:78-81. [PMID: 15525983 DOI: 10.1038/nature02986] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Accepted: 08/27/2004] [Indexed: 11/09/2022]
Abstract
A relationship between solar activity and aurorae on Earth was postulated long before space probes directly detected plasma propagating outwards from the Sun. Violent solar eruption events trigger interplanetary shocks that compress Earth's magnetosphere, leading to increased energetic particle precipitation into the ionosphere and subsequent auroral storms. Monitoring shocks is now part of the 'Space Weather' forecast programme aimed at predicting solar-activity-related environmental hazards. The outer planets also experience aurorae, and here we report the discovery of a strong transient polar emission on Saturn, tentatively attributed to the passage of an interplanetary shock--and ultimately to a series of solar coronal mass ejection (CME) events. We could trace the shock-triggered events from Earth, where auroral storms were recorded, to Jupiter, where the auroral activity was strongly enhanced, and to Saturn, where it activated the unusual polar source. This establishes that shocks retain their properties and their ability to trigger planetary auroral activity throughout the Solar System. Our results also reveal differences in the planetary auroral responses on the passing shock, especially in their latitudinal and local time dependences.
Collapse
Affiliation(s)
- Renée Prangé
- LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France.
| | | | | | | | | | | | | |
Collapse
|
18
|
Gérard JC. Characteristics of Saturn's FUV aurora observed with the Space Telescope Imaging Spectrograph. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2004ja010513] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
19
|
Jackman CM. Interplanetary magnetic field at ∼9 AU during the declining phase of the solar cycle and its implications for Saturn's magnetospheric dynamics. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2004ja010614] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
20
|
Cowley SWH. A simple quantitative model of plasma flows and currents in Saturn's polar ionosphere. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003ja010375] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
21
|
Galand M, Chakrabarti S. Auroral processes in the solar system. ATMOSPHERES IN THE SOLAR SYSTEM: COMPARATIVE AERONOMY 2002. [DOI: 10.1029/130gm05] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
22
|
Galopeau PHM, Lecacheux A. Variations of Saturn's radio rotation period measured at kilometer wavelengths. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999ja005089] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
23
|
Zarka P. Auroral radio emissions at the outer planets: Observations and theories. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98je01323] [Citation(s) in RCA: 339] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
24
|
Clarke JT, Ballester G, Trauger J, Ajello J, Pryor W, Tobiska K, Connerney JEP, Gladstone GR, Waite JH, Ben Jaffel L, Gérard JC. Hubble Space Telescope imaging of Jupiter's UV aurora during the Galileo orbiter mission. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98je01130] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|