Auroral Processes

  • W. S. Kurth
  • E. J. Bunce
  • J. T. Clarke
  • F. J. Crary
  • D. C. Grodent
  • A. P. Ingersoll
  • U. A. Dyudina
  • L. Lamy
  • D. G. Mitchell
  • A. M. Persoon
  • W. R. Pryor
  • J. Saur
  • T. Stallard

Abstract

Cassini has afforded a number of unique opportunities to understand auroral processes at Saturn and to highlight both differences and similarities with auroral physics at both Earth and Jupiter. A number of campaigns were coordinated with the Hubble Space Telescope such that Cassini could provide either ground truth on the impinging solar wind or in situ measurements of magnetospheric conditions leading to qualitative and sometimes quantitative relationships between the solar wind influence on the intensity, the morphology and evolution of the auroras, and magneto-spheric dynamics. The Hubble UV images are enhanced by Cassini's own remote sensing of the auroras. Cassini's in situ studies of the structure and dynamics of the magnetosphere discussed in other chapters of this book provide the context for understanding the primary drivers of Saturn's auroras and the role of magnetospheric dynamics in their variations. Finally, Cassini's three dimensional prime mission survey of the magnetosphere culminates in high inclination orbits placing it at relatively small radial distances while on auroral field lines, providing the first such in situ observations of auroral particles and fields at a planet other than Earth. The new observations have spawned a number of efforts to model the interaction of the solar wind with the magnetosphere and understand how such dynamics influence the auroras.

Keywords

Methane Convection Torque Attenuation Titan 

References

  1. Aguilar, A., Ajello, J.M., Mangina, R.S., James, G.K., Abgrall, H., Roueff, E.: The electron-excited middle UV to near IR spectrum of H2: Cross-sections and transition probabilities. Astrophys. J. Supp. Ser. 177 (2008).Google Scholar
  2. Andrews, D.J., Bunce, E.J., Cowley, S.W.H., Dougherty, M.K., Provan, G., Southwood, D.J.: Planetary period oscillations in Saturn's magnetosphere: Phase relation of equatorial magnetic field oscillations and Saturn kilometric radiation modulation. J. Geophys. Res. 113, A09205, doi:10.1029/2007JA012937 (2008).Google Scholar
  3. Badman, S.V., Cowley, S.W.H.: Significance of Dungey-cycle flows in Jupiter's and Saturn's magnetospheres, and their identification on closed equatorial field lines. Ann. Geophysicae 25, 941–951 (2007).ADSGoogle Scholar
  4. Badman, S.V., Bunce, E., Clarke, J.T., Cowley, S., Gérard, J.C., Grodent, D., Milan, S.: Open flux estimates in Saturn's magnetosphere during the January 2004 HST-Cassini campaign, and implications for reconnection rates. J. Geophys. Res. 110, A11216, doi:10.1029/2005JA011240 (2005).ADSGoogle Scholar
  5. Badman S.V., Cowley, S.W.H., Gerard, J.-C., Grodent, D.: A statistical analysis of the location and width of Saturn's southern auroras. Ann. Geophysicae 24, 3533–3545 (2006).ADSGoogle Scholar
  6. Benediktov, E.A., Getmansev, G.G., Sazonov, Y.A.: Preliminary results of measurements of the intensity of distributed extra-terrestrial radio frequency emission at 725 and 1525 kc (in Russian). Kosm. Issled. 3, 614 (1965).Google Scholar
  7. Bisikalo, D.V., Shematovich, V.I., Gérard, J.-C., Gladstone, R.G., Waite J.H.: The distribution of hot hydrogen atoms produced by electron and proton precipitation in the Jovian aurora. J. Geophys. Res. 101, 21,157–21,168 (1996).ADSGoogle Scholar
  8. Broadfoot, A.L., Sandel, B.R., Shemansky, D.E., Holberg, J.B., Smith, G.R., Strobel, D.F., McConnell, J.C., Kumar, S., Hunten, D.M., Atreya, S.K., Donahue, T.M., Moos, H.W., Bertaux, J.L., Blamont, J.E., Pomphrey, R.B., Linik, S.: Extreme ultraviolet observations from Voyager 1 encounter with Saturn. Science 212, 206–211 (1981).ADSGoogle Scholar
  9. Brown, R.H. et al.: The Cassini Visual and Infrared Mapping Spectrometer (VIMS) investigation. Space Sci. Rev. 115, 111–168 (2004).ADSGoogle Scholar
  10. Bunce, E.J., Cowley, S.W.H., Wild, J.A.: Azimuthal magnetic fields in Saturn's magnetosphere: Effects associated with plasma sub-corotation and the magnetopause-tail current system. Ann. Geo-physicae 21, 1709 (2003).ADSGoogle Scholar
  11. Bunce, E.J., Cowley, S.W.H., Yeoman, T.K.: Jovian cusp processes: implications for the polar aurora. J. Geophys. Res. 109, doi:10.1029/2003JA010280 (2004).Google Scholar
  12. Bunce, E.J., Cowley, S.W.H., Wright, D.M., Coates, A.J., Dougherty, M.K., Kurth, W.S., Krupp, N., Rymer, A.M.: In situ observations of a solar wind compression-induced hot plasma injection event in Saturn's tail. Geophys. Res. Lett. 32, 20, Art No. L20S01 (2005a).Google Scholar
  13. Bunce, E.J., Cowley, S.W.H., Milan, S.E: Interplanetary magnetic field control of Saturn's polar cusp aurora. Ann. Geophys. 23, 1405 (2005b).ADSGoogle Scholar
  14. Bunce, E.J., Cowley, S., Jackson, C., Clarke, J.T., Crary, F., Dougherty, M.: Cassini observations of the interplanetary medium upstream of Saturn and their relation to the Hubble Space Telescope aurora data. Adv. Sp. Res. 38, 806–814 (2006).ADSGoogle Scholar
  15. Bunce, E.J., Arridge, C.S., Clarke, J.T., Coates, A.J., Cowley, S.W.H., Dougherty, M.K., Gérard, J. C., Grodent, D., Hansen, K.C., Nichols, J.D., Southwood, D.J., Talboys, D.L.: Origin of Saturn's aurora: Simultaneous observations by Cassini and the Hubble Space Telescope. J. Geophys. Res. 113, A09209, doi: 10.1029/2008JA013257 (2008a).Google Scholar
  16. Bunce, E.J., Arridge, C.S., Cowley, S.W.H., Dougherty, M.K.: Magnetic field structure of Saturn's dayside magnetosphere and its mapping to the ionosphere: Results from ring current modeling. J. Geophys. Res., 113, A02207, doi:10.1029/2007JA012538 (2008b).Google Scholar
  17. Carbary, J.F., Mitchell, D.G., Krimigis, S.M., Krupp, N.: Evidence for spiral pattern in Saturn's magnetosphere using the new SKR longitudes. Geophys. Res. Lett. 34, L13105, doi:10.1029/2007GL030167 (2007).ADSGoogle Scholar
  18. Carlson, C.W., McFadden, J.P., Ergun, R.E., Temerin, M., Peria, W., Mozer, F.S., Klumpar, D.M., Shelley, E.G., Peterson, W.K., Moebius, E., Elphic, R., Strangeway, R., Cattell, C., Pfaff, R.: FAST observations in the downward auroral current regions: Energetic up-going electron beams, parallel potential drops, and ion heating. Geo-phys. Res. Lett. 25, 2017–2020 (1998).ADSGoogle Scholar
  19. Carr, T.D, Reyes, F.: Microstructure of Jovian decametric S bursts. J. Geophys. Res. 104, 25,127–25,141 (1999).ADSGoogle Scholar
  20. Cecconi, B., Lamy, L., Zarka, P., Prangé, R., Kurth, W.S., Louarn, P.: Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver. J. Geophys. Res. 114, A03215, doi:10.1029/ 2008JA013830 (2009).Google Scholar
  21. Clarke, J.T., Moos, H.W., Atreya, S.K., Lane, A.L.: IUE detection of bursts of H Ly α emission from Saturn. Nature 290, 226 (1981).ADSGoogle Scholar
  22. Clarke J.T. et al.: Morphological differences between Saturn's ultraviolet aurorae and those of Earth and Jupiter. Nature 433, 717–719 (2005).ADSGoogle Scholar
  23. Clarke, J.T. et al.: The response of Jupiter's and Saturn's auroral activity to the solar wind. J. Geophys. Res. 114, A05210, doi:10.1029/2008JA013694 (2009).Google Scholar
  24. Connerney, J.E.P., Acuna, M.H., Ness, N.F.: Currents in Saturn's magnetosphere. J. Geophys. Res. 88, 8779–8789 (1983).ADSGoogle Scholar
  25. Cowley, S.W.H., Bunce, E.J., Prangé, R.: Saturn's polar ionospheric flows and their relation to the main auroral oval. Ann. Geophys. 22, 1379–1394 (2004a).ADSGoogle Scholar
  26. Cowley, S.W.H., Bunce, E.J., O'Rourke, J.M.: A simple quantitative model of plasma flows and currents in Saturn's polar ionosphere. J. Geophys. Res., 109, A05212, doi:10.1029/2003JA010375 (2004b).Google Scholar
  27. Cowley, S.W.H., Badman, S.V., Bunce, E.J., Clarke, J.T., Gérard, J.-C., Grodent, D., Jackman, C.M., Milan, S.E., Yeoman, T.K.: Reconnection in a rotation-dominated magnetosphere and its relation to Saturn's auroral dynamics. J. Geophys. Res. 110, doi:10.1029/2004JA010796 (2005).Google Scholar
  28. Cowley, S.W.H. et al.: Auroral current systems in Saturn's magnetosphere: Comparison of theoretical models with Cassini and HST observations. Ann Geophys. 26, 2613–2630 (2008).ADSGoogle Scholar
  29. Crary, F.J. et al.: Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae. Nature 433, 720–722 (2005).ADSGoogle Scholar
  30. Davis, L.J, Smith, E.J.: A model of Saturn's magnetic field based on all available data. J. Geophys. Res. 95, 15,257–15,261 (1990).ADSGoogle Scholar
  31. Desch, M.D.: Evidence for solar wind control of Saturn radio emission. J. Geophys. Res. 87, 4549–4554 (1982).ADSGoogle Scholar
  32. Desch, M.D.: Radio emission signature of Saturn immersions in Jupiter's magnetic tail. J. Geophys. Res. 88, 6904 (1983).ADSGoogle Scholar
  33. Desch, M.D., Kaiser, M.L.: Voyager measurements of the rotation period of Saturn's magnetic field. Geophys. Res. Lett. 8, 253–256 (1981).ADSGoogle Scholar
  34. Dougherty, M.K., Achilleos, N., Andre, N., Arridge, C.S., Balogh, A., Bertucci, C., Burton, M.E., Cowley, S.W.H., Erdos, G., Giampieri, G., Glassmeier, K.-H, Khurana, K.K., Leisner, J., Neubauer, F.M., Russell, C.T., Smith, E.J., Southwood, D.J., Tsurutani, B.T.: Cassini magnetometer observations during Saturn orbit insertion, Science, 307, 1266–1270 (2005).ADSGoogle Scholar
  35. Dungey, J.W.: Interplanetary magnetic field and the auroral zones. Phys. Rev. Lett.6 Issue 2, 47–48 (1961)ADSGoogle Scholar
  36. Dyudina, U.A., Ingersoll, A.P. Ewald, S.P.: Aurora at the north pole of Saturn as seen by Cassini ISS. Presented at the Fall AGU meeting in San Francisco (2007).Google Scholar
  37. Ergun, R.E. et al.: FAST satellite observations of electric field structures in the auroral zone. Geophys. Res. Lett. 25, 2025–2028 (1998).ADSGoogle Scholar
  38. Esposito, L.W. et al.: The Cassini Ultraviolet Imaging Spectrograph Investigation. Space Sci. Rev. 115, 299–361 (2004).ADSGoogle Scholar
  39. Esposito, L.W. et al.: Ultraviolet Imaging Spectroscopy shows an active Saturnian system. Science 307, 1251–1255 (2005).ADSGoogle Scholar
  40. Flasar, F. M. et al.: Exploring the Saturn system in the thermal infrared: The composite Infrared Spectrometer. Space Sci. Rev. 115, 169–297 (2004).ADSGoogle Scholar
  41. Galopeau, P., Zarka, P., Le Queau, D.: Theoretical model of Saturn's kilometric radiation spectrum. J. Geophys. Res. 94, 8739–8755 (1989).ADSGoogle Scholar
  42. Galopeau, P., Zarka, P., Le Queau, D.: Source locations of SKR: The Kelvin–Helmholtz instability hypothesis. J. Geophys. Res. 100, 26,397–26,410 (1995).ADSGoogle Scholar
  43. Galopeau, P.H.M., Lecacheux: A. Variations of Saturn's radio rotation period measured at kilometer wavelengths. J. Geophys. Res. 105, A6, 13,089–13,102 (2000).ADSGoogle Scholar
  44. Gérard, J.-C., Singh, V.: A Model of energy deposition of energetic electrons and EUV emission in the Jovian and Saturnian atmospheres and implications. J. Geophys. Res. 87, 4525–4532 (1982).ADSGoogle Scholar
  45. Gérard, J.-C., Gustin, J., Grodent, D., Delamere, P., Clarke, J.T.: The excitation of the FUV Io tail on Jupiter: Characterization of the electron precipitation. J. Geophys. Res. 107, 1394, doi:10.1029/2002JA009410 (2002).Google Scholar
  46. Gérard, J.-C., Gustin, J., Grodent, D., Clarke, J.T., Grard, A.: Spectral observations of transient features in the FUV Jovian polar aurora. J. Geophys. Res. 108, A8, 1319, doi:10.1029/2003JA009901 (2003).Google Scholar
  47. Gérard, J.-C., Grodent, D., Gustin, J., Saglam, A., Clarke, J.T., Trauger, J.T.: Characteristics of Saturn's FUV aurora observed with the Space Telescope Imaging Spectrograph. J. Geophys. Res. 109, A09207, doi:10.1029/2004JA010513 (2004).Google Scholar
  48. Gérard, J.-C., Bunce, E., Grodent, D., Cowley, S., Clarke, J.T., Badman, S.: 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 (2005).ADSGoogle Scholar
  49. Gérard, J.-C. et al.: Saturn's auroral morphology and activity during quiet magnetospheric conditions. J. Geophys. Res. 111, A12210, doi:10.1029/2006JA011965 (2006).ADSGoogle Scholar
  50. Gérard, J.-C., Bonfond, B., Gustin, J., Grodent, D.: The altitude of Saturn's aurora and its implications for the characteristic energy of precipitated electrons. Geophys. Res. Lett. 36, L02202, doi:10.1029/2008GL036554 (2009).Google Scholar
  51. Goldstein, M.L., Goertz, C.K.: Theories of radio emissions and plasma waves. In: Dessler, A.J. (ed.): Physics of the Jovian Magnetosphere, pp. 317–352. Cambridge University Press, New York (1983)Google Scholar
  52. Grodent, D., Waite, J.H., Gérard, J.C.: A self-consistent model of the jovian auroral thermal structure. J. Geophys. Res. 106, 12,933–12,952 (2001).ADSGoogle Scholar
  53. Grodent, D., Gérard, J.-C., Cowley, S., Bunce, E., Clarke J.T.: The global morphology of Saturn's southern ultraviolet aurora. J. Geo-phys. Res. 110, A07215, doi:10.1029/2004JA010983 (2005).Google Scholar
  54. Gurnett, D.A.: The Earth as a radio source: Terrestrial kilometric radiation. J. Geophys. Res. 79, 4227–4238 (1974).ADSGoogle Scholar
  55. Gurnett, D.A., Anderson, R.R.: The kilometric radio emission spectrum: Relationship to auroral acceleration processes. In Akasofu, S.-I., Kan, J.R. (eds.) Physics of Auroral Arc Formation, 25, pp. 341–350. Geophysical Monograph Series, American Geophysical Union (1981).Google Scholar
  56. Gurnett, D.A., Kurth, W.S.,Hospodarsky, G.B., Persoon, A.M., Zarka, P., Lecacheux, A., Bolton, S.J., Desch, M.D., Farrell, W.M., Kaiser, M.L., Ladreiter, H.-P., Rucker, H.O., Galopeau, P., Louarn, P., Young, D.T., Pryor, W.R., Dougherty, M.K.: Control of Jupiter's radio emission and aurorae by the solar wind. Nature 415, 985–987. (2002).ADSGoogle Scholar
  57. Gurnett, D.A. et al.: The Cassini Radio and Plasma Wave Science Investigation. Space Sci. Rev. 114, 395–463 (2004).ADSGoogle Scholar
  58. Gurnett, D.A., Kurth, W.S., Hospodarsky, G.B., Persoon, A.M., Averkamp, T.F., Cecconi, B., Lecacheux, A., Zarka, P., Canu, P., Cornilleau-Wehrlin, N., Galopeau, P., Roux, A., Harvey, C., Louarn, P., Bostrom, R., Gustafsson, G., Wahlund, J.-E., Desch, M.D., Farrell, W.M., Kaiser, M.L., Goetz, K., Kellogg, P.J., Fischer, G.,Ladreiter, H.-P., Rucker, H., Alleyne, H., Pedersen, A.: Radio and plasma wave observations at Saturn from Cassini's approach and first orbit. Science 307, 1255–1259, doi: 10.1126/science. 1105356 (2005).ADSGoogle Scholar
  59. Gurnett, D.A., Persoon, A.M., Kurth, W.S., Groene, J.B., Averkamp, T.F., Dougherty, M.K., Southwood, D.J.: The variable rotation period of the inner region of Saturn's plasma disk. Science 316, 5823, 442–445, doi: 10.1016/science. 1138562 (2007).ADSGoogle Scholar
  60. Gustin, J., Feldman, P.D., Gérard, J.-C, Grodent, D., Vidal-Madjar, A., Ben Jaffel, L., Desert, J.-M., Moos, H.W., Sahnow, D.J., Weaver, H.A., Wolven, B.C., Ajello, J.M., Waite, J.H., Roueff, E., Abgrall, H.: Jovian auroral spectroscopy with FUSE: Analysis of self absorption and implications for electron precipitation. Icarus 171, 336–355 (2004).ADSGoogle Scholar
  61. Gustin, J., Gérard, J.C., Pryor, W., Feldman, P.D., Grodent, D., Holsclaw, G.: Characteristics of Saturn's polar atmosphere and auroral electrons derived from HST/STIS, FUSE and Cassini/UVIS spectra. Icarus 200, 176–187, doi:10.1016/j.icarus.2008.11.013 (2009).ADSGoogle Scholar
  62. Ingersoll, A.P., Vasavada, A.R., Little, B., Anger, CD., Bolton, S.J., Alexander, C, Klaasen, K.P, Tobiska, W.K.: Imaging Jupiter's aurora at visible wavelengths. Icarus 135, 251–264 (1998).ADSGoogle Scholar
  63. Isbell, J., Dessler, A.J., Waite, J.H., Jr.: Magnetospheric energization by interaction between planetary spin and the solar wind. J. Geophys. Res. 89, 10,716 (1984).ADSGoogle Scholar
  64. Jackman, CM, Cowley, S.W.H.: A model of the plasma flow and current in Saturn's polar ionosphere under conditions of strong Dungey cycle driving. Ann. Geophys. 24, 1029–1055 (2006).ADSGoogle Scholar
  65. Jackman, CM., Achilleos, N., Bunce, E.J., Cowley, S.W.H., Dougherty, M.K., Jones, G.H., Milan, S.E., Smith, E.J.: Interplanetary magnetic field at ~9 AU during the declining phase of the solar cycle and its implications for Saturn's magnetospheric dynamics. J. Geophys. Res. 109, A11203, doi: 10.1029/2004JA010614 (2004).ADSGoogle Scholar
  66. Jackman, CM., Russell, C.T., Southwood, D.J., Arridge, C.S., Achilleos, N., Dougherty M.K.: Strong rapid dipolarizations in Saturn's magnetotail: In situ evidence of reconnection. Geophys. Res. Lett. 34, L11203, doi:10.1029/2007GL029764 (2007).ADSGoogle Scholar
  67. Jackman, CM. et al.: A multi-instrument view of tail reconnection at Saturn. J. Geophys. Res. 113, A11213, doi:10.1029/2008JA013592 (2008).ADSGoogle Scholar
  68. Kaiser, M.L., Desch, M.D., Warwick, J.W, Pearce, J.B.: Voyager detection of nonthermal radio emission from Saturn. Science 209, 1238–1240 (1980).ADSGoogle Scholar
  69. Khurana, K.K., Arridge, C.S, Dougherty, M.K.: A versatile model of Saturn's magnetospheric field. Geophys. Res. Abstract, 7, 05970 (2005).Google Scholar
  70. Klumpar, D.M.: Near equatorial signatures of dynamic auroral processes. In Physics of Space Plasmas, SPI Conf. Proc. Reprint Ser. 9, p. 265. Scientific Publishers, Inc., Cambridge, Massachusetts (1990).Google Scholar
  71. Knight, S.: Parallel electric fields. Planet. Space Sci. 21, 741–750 (1973).ADSGoogle Scholar
  72. Kurth, W.S. et al.: An Earth-like correspondence between Saturn's ultraviolet auroral features and radio emission. Nature 433, 722–725 (2005a).ADSGoogle Scholar
  73. Kurth, W.S., Hospodarsky, G.B., Gurnett, D.A., Cecconi, B., Louarn, P., Lecacheux, A., Zarka, P., Rucker, H.O., Boudjada, M., Kaiser, M.L.: High spectral and temporal resolution observations of Saturn kilometric radiation. Geophys. Res. Lett. 32, L20S07, doi: 10.1029/2005GL022648 (2005b).Google Scholar
  74. Kurth, W.S., Lecacheux, A., Averkamp, T.F., Groene, J.B., Gurnett, D.A.: A Saturnian longitude system based on a variable kilometric radiation period. Geophys. Res. Lett. 34, L02201, doi:10.1029/2006GL028336 (2007).Google Scholar
  75. Kurth, W.S., Averkamp, T.F., Gurnett, D.A., Groene, J.B., Lecacheux A.: An update to a Saturnian longitude system based on kilometric radio emissions. J. Geophys. Res. 113, A05222, doi:10.1029/2007JA012861 (2008).Google Scholar
  76. Lamy, L.: Study of Saturn auroral radio emissions, modeling and UV aurorae, PhD thesis, Université Pierre et Marie Curie (2008a).Google Scholar
  77. Lamy, L., Zarka, P., Cecconi, B., Prange, R., Kurth, W.S., Gurnett, D.A.: Saturn kilometric radiation: Average and statistical properties. J. Geophys. Res. 113, A07201, doi:10.1029/2007JA012900 (2008b).Google Scholar
  78. Lamy, L., Zarka, P., Cecconi, B., Hess, S., Prangé, R.: Modeling of Saturn kilometric radiation arcs and equatorial shadow zone. J. Geo-phys. Res. 113, A10213, doi:10.1029/2008JA013464 (2008c).ADSGoogle Scholar
  79. Lamy, L., Cecconi, B., Prangé, R., Zarka, P., Nichols, J., Clarke, J.: An auroral oval at the footprint of Saturn's kilometric radiosources, colocated with the UV aurorae. J. Geophys. Res. in press (2009).Google Scholar
  80. Lecacheux, A., Galopeau, P., Aubier M.: Re-visiting Saturnian radiation with Ulysses/URAP. In Rucker, H.O., Bauer, S.J., Lecacheux, A. (eds.) Planetary Radio Emissions IV, pp. 313–325. Austrian Academy of Sciences Press, Vienna (1997).Google Scholar
  81. Louarn, P., Kurth, W.S., Gurnett, D.A., Hospodarsky, G.B., Persoon, A.M., Cecconi, B., Lecacheux, A., Zarka, P., Canu, P., Roux, A., Rucker, H.O., Farrell, W.L., Kaiser, M.L., Andre, N., Harvey, C., Blanc, M.: Observation of similar radio signatures at Saturn and Jupiter: Implications for the magnetospheric dynamics. Geophys. Res. Lett. 34, L20113, doi:10.1029/2007GL030368 (2007).ADSGoogle Scholar
  82. Main, D.S., Newman, D.L., Ergun, R.E.: Double layers and ion phase-space holes in the auroral upward-current region. Phys. Rev. Lett. 97, 185001, doi: 10.1103/PhysRevLett.97.185001 (2006).ADSGoogle Scholar
  83. Marklund, G.T., Ivchenko, N., Karlsson, T., Fazakerley, A., Dunlop, M., Lindqvist, P.-A., Buchert, S., Owen, C., Taylor, M., Vaivalds, A., Carter, P., André, M., Balogh, A.: Temporal evolution of the electric field accelerating electrons away from the auroral ionosphere. Nature 414, 724–727 (2001).ADSGoogle Scholar
  84. Mauk, B.H., Saur, J.: Equatorial electron beams and auroral structuring at Jupiter. J. Geophys. Res. 112, A10221, doi:10.1029/2007JA012370 (2007).ADSGoogle Scholar
  85. McGrath, M.A., Clarke, J.T.: HI Ly-’ emission from Saturn (1980–1990). J. Geophys. Res. 97, 13,691 (1992)ADSGoogle Scholar
  86. Melin, H., Miller, S., Stallard, T., Trafton, L.M., Geballe, T.R.: Variability in the H3 + emission of Saturn: Consequences for ionisation rates and temperature. Icarus, 186, 234–241 (2007).ADSGoogle Scholar
  87. Menietti, J.D., Mutel, R.L., Santolik, O., Scudder, J.D., Christopher, I.W., Cook, J.M.: Striated drifting auroral kilometric radiation bursts: Possible stimulation by upward traveling EMIC waves. J. Geophys. Res. 111, A04214, doi:10.1029/2005JA011339 (2006).Google Scholar
  88. Menietti, J.D., Groene, J.B., Averkamp, T.F., Hospodarsky, G.B., Kurth, W.S., Gurnett, D.A., Zarka, P.: Influence of Saturnian moons on Saturn kilometric radiation. J. Geophys. Res. 112, A08211, doi:10.1029/2007JA012331 (2007).Google Scholar
  89. Milan, S.E., Lester, M., Cowley, S.W.H., Brittnacher, M.: Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field. Ann. Geophysicae 18, 436–447 (2000).ADSGoogle Scholar
  90. Milan, S.E., Bunce, E.J., Cowley, S.W.H., Jackman, C.M.: Implications of rapid planetary rotation for the Dungey magnetotail of Saturn, J. Geophys. Res. 110, A03209, doi:10.1029/2004JA010716 (2005).Google Scholar
  91. Mitchell, D.G., Kurth, W.S., Hospodarsky, G.B., Krupp, N., Saur, J., Mauk, B.H., Carbary, J.F., Krimigis, S.M., Dougherty, M.K.: Ion conics and electron beams associated with auroral processes on Saturn. J. Geophys. Res. 114, A02212, doi:10.1029/2008ja013621 (2009a).Google Scholar
  92. Mitchell, D.G., Krimigis, S.M., Paranicas, C., Brandt, P.C., Carbary, J.F., Roelof, E.C., Kurth, W.S., Gurnett, D.A., Clarke, J.T., Nichols, J.D., Gerard, J.-C., Grodent, D.C., Dougherty, M.K.: Recurrent energization of plasma in the midnight-to-dawn quadrant of Saturn's magnetosphere, and its relationship to Auroral UV and radio emissions. Planet. Space Sci. in press doi: 10.1016/j.pss.2009.04.22 (2009b).Google Scholar
  93. Moses, J.I., Bézard, B., Lellouch, E., Feuchtgruber, H., Gladstone, G.R., Allen, M.: Photochemistry of Saturn's atmosphere I. Hydrocarbon chemistry and comparisons with ISO observations. Icarus, 143, 244–298 (2000).ADSGoogle Scholar
  94. Müller-Wodarg, I.C.F., Mendillo, M., Yelle, R.V, Aylward, A.D.: A global circulation model of Saturn's thermosphere. Icarus 180, 147–160 (2006).ADSGoogle Scholar
  95. Muschietti, L., Ergun, R.E., Roth, I., Carlson, C.W.: Phase-space electron holes along magnetic field lines. Geophys. Res. Lett. 26, 1093–1096 (1999).ADSGoogle Scholar
  96. Mutel, R.L., Menietti, J.D., Christopher, I.W., Gurnett, D.A., Cook, J.M.: Striated auroral kilometric radiation emission: A remote tracer of ion solitary structures. J. Geophys. Res. 111, A10203, doi:10.1029/2006JA011660 (2006).ADSGoogle Scholar
  97. Mutel, R.L., Christopher, I.W., Pickett, J.S.: Cluster multi-spacecraft observations of AKR angular beaming. Geophys. Res. Lett. 35, L07104, doi:10.1029/2008GL033377 (2008).Google Scholar
  98. Nichols, J.D., Cowley, S.W.H., McComas, D.J.: Magnetopause recon-nection rate estimates for Jupiter's magnetosphere based on interplanetary measurements at ~5AU. Ann. Geophys. 24, 393–406 (2006).ADSGoogle Scholar
  99. Nichols, J.D., Bunce, E.J., Clarke, J.T., Cowley, S.W.H., Crary, F.J., Dougherty, M.K., Gerard, J.-C, Grodent, D., Pryor, W.R., Rymer, A.M.: Response of Jupiter's UV auroras to interplanetary conditions as observed by the Hubble Space Telescope during the Cassini fly-by campaign. J. Geophys. Res. 112, A02203, doi:10.1029/2006JA012005 (2007).Google Scholar
  100. Nichols, J.D., Clarke, J.T., Cowley, S.W.H., Duval, J., Farmer, A.J., Gérard, J.-C, Grodent, D., Wannawichian, S.: Oscillation of Saturn's southern auroral oval, J. Geophys. Res. 113, A11205, doi:10.1029/2008JA013444 (2008).ADSGoogle Scholar
  101. Pontius, D.H., Hill, T.W.: Enceladus: A significant plasma source for Saturn's magnetosphere. J. Geophys. Res. 111, A09214, doi:10.1029/2006JA011674 (2006).Google Scholar
  102. Porco, C.C. et al.: Cassini imaging science: Instrument characteristics and anticipated scientific investigations at Saturn. Space Sci. Rev. 115, 363–497 (2004).ADSGoogle Scholar
  103. Pottelette, R., Treumann, R.A., Berthomier, M.: Auroral plasma turbulence and the cause of auroral kilometric radiation fine structure. J. Geophys. Res. 106, 8465–8476 (2001).ADSGoogle Scholar
  104. Provan, G., Cowley, S.W.H., Nichols, J.D.: Phase relation of oscillations near the planetary period of Saturn's auroral oval and the equatorial magnetospheric magnetic field. J. Geophys. Res. 114, A04205, doi:10.1029/2008JA013988 (2009).Google Scholar
  105. Pryor, W.R., Stewart, A.I.F, Esposito, L.W., Shemansky, D.E., Ajello, J.M., West, R.A., Jouchoux, A.J., Hansen, C.J., McClintock, W.E., Colwell, J.E., Tsurutani, B.T., Krupp, N., Crary, F.J., Young, D.T., Kurth, W.S., Gurnett, D.A., Dougherty, M.K., Clarke, J.T., Waite, J.H., Grodent D.: Cassini UVIS observations of Jupiter's auroral variability. Icarus 178, 312–326 (2005).ADSGoogle Scholar
  106. Radioti, A., Grodent, D., Gérard, J.C., Roussos, E., Paranicas, C, Bon-fond B., Mitchell, D G., Krupp, N., Krimigis, S., Clarke J.T.: Transient auroral features at Saturn: Signatures of energetic particle injections in the magnetosphere. J. Geophys. Res. 114, A03210, doi:10.1029/2008JA013632 (2009).Google Scholar
  107. Ray, L.C., Su, Y.-J., Ergun, R.E., Delamere, PA., Bagenal, F: Current-voltage relation of a centrifugally confined plasma. J. Geophys. Res. 114, A04214, doi:10.1029/2008JA013969 (2009).Google Scholar
  108. Richardson, J.D.: Thermal ions at Saturn: Plasma parameters and implications. J. Geophys. Res. 91, 1381 (1986).ADSGoogle Scholar
  109. Richardson, J.D.: An extended plasma model for Saturn. Geophys. Res. Lett. 22, 1177 (1995).ADSGoogle Scholar
  110. Richardson, J.D., Sittler, E.C., Jr.: A plasma density model for Saturn based on Voyager observations. J. Geophys. Res. 95, 12,019 (1990).ADSGoogle Scholar
  111. Russell, C.T., Jackman, C.M., Wei, H.Y., Bertucci, C., Dougherty, M.K.: Titan's influence on Saturnian substorm occurrence. Geo-phys. Res. Lett. 35, L12105, doi:10.1029/2008GL034080 (2008).ADSGoogle Scholar
  112. Sandel, B.R., Broadfoot, A.: Morphology of Saturn's Aurora. Nature 292, 679–682 (1981).ADSGoogle Scholar
  113. Sandel, B.R., Shemansky, D.E., Broadfoot, A.L., Holberg, J.B., Smith, G.R.: Extreme ultraviolet observations from the Voyager 2 encounter with Saturn. Science 215, 548 (1982).ADSGoogle Scholar
  114. Saur, J., Mauk, B.H., Mitchell, D.G., Krupp, N., Khurana, K.K., Livi, S., Krimigis, S.M., Newell, P.T., Williams, D.J., Brandt, P.C., Lagg, A., Roussos, E., Dougherty, M.K.: Anti-planetward auroral electron beams at Saturn. Nature, 439, 699–702, doi:10.1038/nature04401 (2006).ADSGoogle Scholar
  115. Shemansky, D.E., Ajello, J.M.: The Saturn spectrum in the EUV: Electron excited Hydrogen. J. Geophys. Res. 88, 459 (1983).ADSGoogle Scholar
  116. Sittler, E.J., Blanc, M., Richardson, J.: Proposed model for Saturn's auroral response to the solar wind: Centrifugal instability model. J. Geophys. Res. 111, A06208, doi:10.1029/2005JA011191 (2006).Google Scholar
  117. Stallard, T.S., Miller, S., Cowley, S.W.H., Bunce, E.J.: Jupiter's polar ionospheric flows: Measured intensity and velocity variations poleward of the main auroral oval. Geophys. Res. Lett. 30, 1221, doi:10.1029/2002GL016031 (2003).ADSGoogle Scholar
  118. Stallard, T., Miller, S., Trafton, L.M., Geballe, T.R., Joseph, R.D.: Ion winds in Saturn's southern auroral/polar region. Icarus 167, 204–211 (2004).ADSGoogle Scholar
  119. Stallard, T. et al.: Saturn's auroral/polar H3 + infrared emission I: General morphology and ion velocity structure. Icarus 189, 1–13 (2007a).ADSGoogle Scholar
  120. Stallard, T et al.: Saturn's auroral/polar H3 + infrared emission II: A comparison with plasma flow models, Icarus 191 678–690 (2007b)ADSGoogle Scholar
  121. Stallard, T., Lystrup, M., Miller, S.: Emission-line imaging of Saturn's H3 −2 aurora. Astrophys. J. 675, L117 (2008a).ADSGoogle Scholar
  122. Stallard, T., Miller, S., Lystrup, M., Achilleos, N., Arridge, C., Dougherty, M.: Dusk-brightening event in Saturn's H3 −2 Aurora. Astrophys. J. 673, L203–L206 (2008b).ADSGoogle Scholar
  123. Stallard, T. et al.: Jovian-like aurorae on Saturn. Nature 453, 1083–1085 (2008c).ADSGoogle Scholar
  124. Stallard, T. et al.: Complex structure within Saturn's infrared aurora. Nature 456, 214–217 (2008d).ADSGoogle Scholar
  125. Talboys, D.L., Arridge, C.S., Bunce, E.J., Coates, A.J., Cowley, S.W.H., Dougherty, M.K.: Characterisation of auroral current systems in Saturn's magnetosphere: High-latitude Cassini observations. J. Geo-phys. Res. 114, A06220, doi:10.1029/2008JA013846 (2009).Google Scholar
  126. Trauger, J.T. et al.: Saturn's far-ultraviolet hydrogen aurora, imaging observations from the Hubble Space Telescope. J. Geophys. Res. 103, E9, 20,237 (1998).ADSGoogle Scholar
  127. Vasavada, A.R., Bouchez, A.H., Ingersoll, A.P., Little, B., Anger, C.D.: The Galileo SSI team: Jupiter's visible aurora and Io footprint. J. Geophys. Res. 104, 27,133–27,142 (1999).ADSGoogle Scholar
  128. Vasyliunas, V.M.: Plasma distribution and flow. In Dessler A.J. (ed.) Physics of the Jovian Magnetosphere, p. 395. Cambridge University Press, Cambridge (1983).Google Scholar
  129. Wang, Z., Gurnett, D.A., Fischer, G., Ye, S.-Y., Kurth, W.S., Mitchell, D.G., Leisner, J.S., Russell, C.T.: Cassini observations of narrowband radio emissions in Saturn's magnetosphere, J. Geophys. Res. submitted (2009).Google Scholar
  130. Wannawichian, S., Clarke, J.T., Pontius, D.H.: Interaction evidence between Enceladus’ atmosphere and Saturn's magnetosphere. J. Geo-phys. Res. 113, A07217, doi:10.1029/2007JA012899 (2008).Google Scholar
  131. Warwick, J. et al.: Planetary radio astronomy observations from Voyager 1 near Saturn, Science 212 239–243 (1981)ADSGoogle Scholar
  132. Wilson, R.J., Tokar, R.L.,, Henderson, M.G., Hill, T.W., Thomsen, M.F., Pontius, Jr., D.H.: Cassini plasma spectrometer thermal ion measurements in Saturn's inner magnetosphere. J. Geophys. Res. 113, A12218, doi:10.1029/2008JA013486 (2008).ADSGoogle Scholar
  133. Wu, C.S., Lee, L.C.: A theory of the terrestrial kilometric radiation. Astrophys. J. 230, 621–626 (1979).ADSGoogle Scholar
  134. Ye, S.-Y., Gurnett, D.A., Fischer, G., Cecconi, B., Menietti, J.D., Kurth, W.S., Wang, Z., Hospodarsky, G.B., Zarka, P., Lecacheux, A.: Source locations of narrowband radio emissions detected at Saturn. J. Geophys. Res. 114, A06219, doi: 10.1029/2008ja013855 (2009).Google Scholar
  135. Zarka, P.: Auroral radio emissions at the outer planets: Observations and theories. J. Geophys. Res. 103, 20,159–20,194 (1998).ADSGoogle Scholar
  136. Zarka, P., Lamy, L., Cecconi, B., Prange, R., Rucker, H.: Modulation of Saturn's radio clock by solar wind speed. Nature 450, 265–267, doi:10.1038/nature06237 (2007).ADSGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • W. S. Kurth
    • 1
  • E. J. Bunce
    • 2
  • J. T. Clarke
    • 3
  • F. J. Crary
    • 4
  • D. C. Grodent
    • 5
  • A. P. Ingersoll
    • 6
  • U. A. Dyudina
    • 6
  • L. Lamy
    • 7
  • D. G. Mitchell
    • 8
  • A. M. Persoon
    • 1
  • W. R. Pryor
    • 9
  • J. Saur
    • 10
  • T. Stallard
    • 2
  1. 1.Department Physics and AstronomyThe University of IowaIowa CityUSA
  2. 2.Department Physics and AstronomyUniversity of LeicesterLeicesterGreat Britain
  3. 3.Center for Space PhysicsBoston UniversityBOUSA
  4. 4.Southwest Research InstituteSan AntonioUSA
  5. 5.LPAPUniversité de Liège, B-4000LiègeBelgium
  6. 6.CaltechPasadenaUSA
  7. 7.LESIAObservatoire de ParisFrance
  8. 8.Applied Physics LaboratoryJohns Hopkins UniversityLaurelUSA
  9. 9.Dept. PhysicsCentral Arizona CollegeCoolidgeUSA
  10. 10.Institute of Geophysics and MeteorologyUniversity of CologneCologneGermany

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