[en] We report the results of a coordinated Hubble Space Telescope-Cassini campaign that took place between 26 October and 2 November 2005. During this period, Saturn's magnetosphere was in an expanded state and the solar wind was quiet, as indicated by the location of the magnetopause, in situ particle measurements, weak auroral SKR emission, and the generally low brightness of the aurora. We describe the morphology and dynamics of the aurora during this period in parallel with concurrent Cassini measurements. We show that the aurora exhibits considerable longitudinal structure and time variations over intervals of a few hours, in spite of the absence of observable external triggers and generally low intensity. In particular, enhancements of the dawn-morning oval are seen while no apparent indication of solar wind activity is observed. These features rotate at a speed corresponding to about 65% of the planet's angular velocity. We also describe energetic neutral atom measurements indicating that an ENA acceleration event occurred in the magnetotail on 26 October without any measured signature of solar wind activation. These observations suggest an intrinsically dynamical magnetosphere where injection of hot plasma occasionally takes place in the night or dawn sector during quiet magnetospheric conditions, possibly connected with either the Dungey or the Vasyliunas convection cycle.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Gérard, Jean-Claude ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Grodent, Denis ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Cowley, S. W. H.
Mitchell, D. G.
Kurth, William; University of Iowa > Department of Physics and Astronomy
Clarke, J. T.
Bunce, E. J.
Nichols, J. D.
Dougherty, M. K.
Crary, F. J.
Coates, A. J.
Language :
English
Title :
Saturn's auroral morphology and activity during quiet magnetospheric conditions
Publication date :
01 December 2006
Journal title :
Journal of Geophysical Research. Space Physics
ISSN :
2169-9380
eISSN :
2169-9402
Publisher :
American Geophysical Union (AGU), Washington, United States - District of Columbia
scite shows how a scientific paper has been cited by providing the context of the citation, a classification describing whether it supports, mentions, or contrasts the cited claim, and a label indicating in which section the citation was made.
Bibliography
Arridge, C. S., N. Achilleos, M. K. Dougherty, K. K. Khurana, and C. T. Russell (2006), Modeling the size and shape of Saturn's magnetopause with variable dynamic pressure, J. Geophys. Res., 111, A11227, doi:10.1029/2005JA011574.
Badman, S. V., E. J. Bunce, J. T. Clarke, S. W. H. Cowley, J.-C. Gérard, D. Grodent, and S. E. Milan (2005), Open flux estimates in Saturn's magnetosphere during the January 2004 Cassini-HST campaign, and implications for reconnection rates, J. Geophys. Res., 110, A11216, doi:10.1029/2005JA011240.
Broadfoot, A. L., et al. (1981), Extreme ultraviolet observations from Voyager 1 encounter with Saturn, Science, 212, 206.
Bunce, E. J., and S. W. H. Cowley (2003), A note on the ring current in Saturn's magnetosphere: Comparison of magnetic data obtained during the Pioneer-11 and Voyager-1 and -2 fly-bys, Ann. Geophys., 21, 661.
Bunce, E. J., S. W. H. Cowley, and S. E. Milan (2005), Interplanetary magnetic field control of Saturn 's polar cusp aurora, Ann. Geophys., 23, 1405.
Clarke, J. T., H. W. Moos, S. K. Atreya, and A. L. Lane (1981), IUE detection of bursts of H Ly α emission from Saturn, Nature, 290, 226.
Clarke, J. T., et al. (2005), Morphological differences between Saturn's ultraviolet aurorae and those of Earth and Saturn, Nature, 433, 717.
Connerney, J. E. P., M. H. Acuña, and N. F. Ness (1983), Currents in Saturn's magnetosphere, J. Geophys. Res., 88, 8779.
Cowley, S. W. H., D. M. Wright, E. J. Bunce, A. C. Carter, M. K. Dougherty, G. Giampieri, J. D. Nichols, and T. R. Robinson (2006), Cassini observations of planetary-period magnetic field oscillations in Saturn's magnetosphere: Doppler shifts and phase motion, Geophys. Res. Lett., 33, L07104, doi:10.1029/2005GL025522.
Cowley, S. W. H., E. J. Bunce, and R. Prangé (2004), Saturn's polar ionospheric flows and their relation to the main auroral oval, Ann. Geophys., 22, 1379.
Cowley, S. W. H., S. V. Badman, E. J. Bunce, J. T. Clarke, J.-C. Gérard, D. Grodent, C. M. Jackman, S. E. Milan, and T. K. Yeoman (2005), Reconnection in a rotation-dominated magnetosphere and its relation to Saturn's auroral dynamics, J. Geophys. Res., 110, A02201, doi:10.1029/ 2004JA010796.
Crary, F. J., et al. (2005), Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae, Nature, 433, 720.
Dougherty, M. K., et al. (2004), The Cassini magnetic field investigation, Space Sci. Rev., 114, 331.
Dougherty, M. K., et al. (2005), Cassini magnetometer observations during Saturn orbit insertion, Science, 307, 1266.
Espinosa, S. A., and M. K. Dougherty (2000), Periodic perturbations in Saturn's magnetic field, Geophys. Res. Lett., 27, 2785.
Espinosa, S. A., D. J. Southwood, and M. K. Dougherty (2003), Reanalysis of Saturn's magnetospheric field data view of spin-periodic perturbations, J. Geophys. Res., 108(A2), 1085, doi: 10.1029/2001JA005083.
Gérard, J.-C., and V. Singh (1982), A model of energetic electrons and EUV emission in the Jovian and Saturnian atmospheres and implications, J. Geophys. Res., 87, 4525.
Gérard, J.-C., V. Dois, D. Grodent, J. H. Waite, G. R. Gladstone, and R. Prangé (1995), Simultaneous observations of the Satumian aurora and polar haze with the HST/FOC, Geophys. Res. Lett., 22, 2685.
Gérard, J.-C., J. Gustin, D. Grodent, P. Delamere, and J. T. Clarke (2002), Excitation of the FUV Io tail on Jupiter: Characterization of the electron precipitation, J. Geophys. Res., 17(A11), 1394, doi:10.1029/2002JA009410.
Gérard, J.-C., E. J. Bunce, D. Grodent, S. W. H. Crowley, J. T. Clarke, and S. V. Badman (2005), Signature of Saturn's auroral cusp: Simultaneous Hubble Space Telescope FUV observations and upstream solar wind monitoring, J. Geophys. Res., 110, A11201, doi:10.1029/2005JA011094.
Gérard, J.-C., P. Grodent, J. Gustin, A. Saglam, J. T. Clarke, and J. T. Trauger (2004), Characteristics of Saturn's FUV aurora observed with the Space Telescope Imaging Spectrograph, J. Geophys. Res., 109, A09207, doi:10.1029/2004JA010513.
Grodent, D., J.-C. Gérard, S. W. H. Cowley, E. J. Bunce, and J. T. Clarke (2005), The global morphology of Saturn's southern ultraviolet aurora, J. Geophys. Res., 110, A01207, doi:10.1029/2004JA010717.
Gurnett, D. A., et al. (2004), The Cassini Radio and Plasma Wave Investigation, Space Sci. Rev., 114, 395.
Jackman, C. M., and S, W. H. Cowley (2006), A model of the plasma flow and current in Saturn's polar ionosphere under conditions of strong Dungey-cycle driving, Ann. Geophys., 24, 1029.
Kurth, W. S., et al. (2005), An Earth-like correspondence between Saturn's auroral features and radio emission, Nature, 433, 722.
McGrath, M. A., and J. T. Clarke (1992), H I Lyman alpha emission from Saturn (1980-1990), J. Geophys. Res., 103, 20,237.
Mitchell, D. G., et al. (2005), Energetic ion acceleration in Saturn's magnetotail: Substorms at Saturn?, Geophys. Res. Lett., 32, L20S01, doi:10.1029/2005GL022647.
Sandel, B. R., and A. L. Broadfoot (1981), Morphology of Saturn's aurora, Nature, 292, 679.
Sandel, B. R., et al. (1982), Extreme ultraviolet observations from the Voyager 2 encounter with Saturn, Science, 215, 548.
Slavin, J. A., E. J. Smith, J. R. Spreiter, and S. S. Stahara (1985), Solar wind flow about the outer planets: Gas dynamic modeling of the Jupiter and Saturn bow shocks, J. Geophys. Res., 90, 6275.
Trauger, J. T., et al. (1998), Saturn's hydrogen aurora: Wide field and planetary camera 2 imaging from the Hubble Space Telescope, J. Geophys. Res., 103, 20,237.
Waite, J. H., Jr., T. E. Cravens, J. U. Kozyra, A. F. Nagy, S. K. Atreya, and R. H. Chen (1983), Electron precipitation and related aeronomy of the Jovian thermosphere and ionosphere, J. Geophys. Res., 88, 6143.
Young, D. T., et al. (2004), Cassini Plasma Spectrometer Investigation, Space Sci. Rev., 114, 1.
This website uses cookies to improve user experience. Read more
Save & Close
Accept all
Decline all
Show detailsHide details
Cookie declaration
About cookies
Strictly necessary
Performance
Strictly necessary cookies allow core website functionality such as user login and account management. The website cannot be used properly without strictly necessary cookies.
This cookie is used by Cookie-Script.com service to remember visitor cookie consent preferences. It is necessary for Cookie-Script.com cookie banner to work properly.
Performance cookies are used to see how visitors use the website, eg. analytics cookies. Those cookies cannot be used to directly identify a certain visitor.
Used to store the attribution information, the referrer initially used to visit the website
Cookies are small text files that are placed on your computer by websites that you visit. Websites use cookies to help users navigate efficiently and perform certain functions. Cookies that are required for the website to operate properly are allowed to be set without your permission. All other cookies need to be approved before they can be set in the browser.
You can change your consent to cookie usage at any time on our Privacy Policy page.