[en] While the terrestrial aurorae are known to be driven primarily by the interaction of the Earth's magnetosphere with the solar wind, there is considerable evidence that auroral emissions on Jupiter and Saturn are driven primarily by internal processes, with the main energy source being the planets' rapid rotation. Prior observations have suggested there might be some influence of the solar wind on Jupiter's aurorae and indicated that auroral storms on Saturn can occur at times of solar wind pressure increases. To investigate in detail the dependence of auroral processes on solar wind conditions, a large campaign of observations of these planets has been undertaken using the Hubble Space Telescope, in association with measurements from planetary spacecraft and solar wind conditions both propagated from 1 AU and measured near each planet. The data indicate a brightening of both the auroral emissions and Saturn kilometric radiation at Saturn close in time to the arrival of solar wind shocks and pressure increases, consistent with a direct physical relationship between Saturnian auroral processes and solar wind conditions. At Jupiter the correlation is less strong, with increases in total auroral power seen near the arrival of solar wind forward shocks but little increase observed near reverse shocks. In addition, auroral dawn storms have been observed when there was little change in solar wind conditions. The data are consistent with some solar wind influence on some Jovian auroral processes, while the auroral activity also varies independently of the solar wind. This extensive data set will serve to constrain theoretical models for the interaction of the solar wind with the magnetospheres of Jupiter and Saturn.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Clarke, J. T.; Center for Space Physics, Boston University, Boston, Massachusetts, USA
Nichols, J.
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)
Akasofu, S.-I. (1964), The development of the auroral substorm, Planet. Space Sci., 12, 273-282, doi:10.1016/0032-0633(64)90151-5.
Arridge, C. S., C. T. Russell, K. K. Khurana, N. Achilleos, S. W. H. Cowley, M. K. Dougherty, D. J. Southwood, and E. J. Bunce (2008), Saturn's magnetodisc current sheet, J. Geophys. Res., 113, A04214, doi:10.1029/ 2007JA012540.
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, Al 1216, doi:10.1029/2005JA011240.
Ballester, G. E., et al. (1996), Time-resolved observations of Jupiter's far-UV aurora: Comparison of WFPC2 and IUE, Science, 274, 409-413, doi:10.1126/science.274.5286.409.
Baron, R. L., T. Owen, J. Connerney, T. Satoh, and J. Harrington (1996), Solar wind control of Jupiter's auroras, Icarus, 120, 437-442, doi:10.1006/icar.1996.0063.
Barrow, C. H., F. Genova, and M. D. Desch (1986), Solar wind control of Jupiter's decametric radio emission, Astron. Astrophys., 165, 244-250.
Boudouridis, A., E. Zesta, R. Lyons, P. C. Anderson, and D. Lummerzheim (2003), Effect of solar wind pressure pulses on the size and strength of the auroral oval, J. Geophys. Res., 108(A4), 8012, doi:10.1029/2002JA009373.
Brittnacher, M., M. Wilber, M. Fillingim, D. Chua, G. Parks, J. Spann, and G. Germany (2000), Global auroral response to a solar wind pressure pulse, Adv. Space Res., 25, 1377-1385, doi: 10.1016/S0273-1177(99)00647-X.
Bunce, E. J., et al. (2008), Origin of Saturn's aurora: Simultaneous observations by Cassini and the Hubble Space Telescope, J. Geophys. Res., 113, A09209, doi:10.1029/2008JA013257.
Cecconi, B., and P. Zarka (2005), Model of a variable radio period for Saturn, J. Geophys. Res., 110, A12203, doi:10.1029/2005JA011085. (Pubitemid 44971480)
Cecconi, B., L. Lamy, P. Zarka, R. Prangé, W. S. Kurth, and P. Louarn (2009), 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.
Clarke, J. T., et al. (1998), Hubble Space Telescope imaging of Jupiter's UV aurora during the Galileo orbiter mission, J. Geophys. Res., 103(E9), 20,217 - 20,236, doi:10.1029/98JE01130.
Clarke, J. T., D. Grodent, S. Cowley, E. Bunce, J. Connerney, and T. Satoh (2004), Jupiter's aurora, in Jupiter: The Planet, Satellites, and Magnetosphere, pp. 639-670, Cambridge Univ. Press, Cambridge, U. K.
Clarke, J. T., et al. (2005), Morphological differences between Saturn's ultraviolet aurorae and those of Earth and Jupiter, Nature, 433, 717-719, doi:10.1038/nature03331.
Chua, D., G. Parks, M. Brittnacher, W. Peria, G. Germany, J. Spann, and C. Carlson (2001), Energy characteristics of auroral electron precipitation: A comparison of substorms and pressure pulse related auroral activity, J. Geophys. Res., 106(A4), 5945-5956, doi:10.1029/2000JA003027.
Connerney, J. E. P., M. H. Acuña, and N. F. Ness (1983), Currents in Saturn's magnetosphere, J. Geophys. Res., 88(A11), 8779-8789, doi:10.1029/JA088iA11p08779.
Cowley, S. W. H., and E. J. Bunce (2001), Origin of the main auroral oval in Jupiter's coupled magnetosphere-ionosphere system, Planet. Space Sci., 49, 1067-1088, doi:10.1016/S0032-0633(00)00167-7.
Cowley, S. W. H., and E. J. Bunce (2003), Corotation-driven magnetosphereionosphere coupling currents in Saturn's magnetosphere and their relation to the auroras, Ann. Geophys., 21, 1691-1707.
Cowley, S. W. H., and M. Lockwood (1992), Excitation and decay of solar wind-driven flows in the magnetospere-ionosphere system, Ann. Geophys., 10, 103-115.
Cowley, S. W. H., E. J. Bunce, and R. Prangé (2003), Saturn's polar ionospheric flows and their relation to the main auroral oval, Ann. Geophys., 21, 1-16.
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.
Cowley, S. W. H., J. D. Nichols, and D. J. Andrews (2007), Modulation of Jupiter's plasma flow, polar currents, and auroral precipitation by solar wind-induced compressions and expansions of the magnetosphere: A simple theoretical model, Ann. Geophys., 25, 1433-1463.
Crary, F., et al. (2005), Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae, Nature, 433, 720-722, doi:10.1038/nature03333. (Pubitemid 40292975)
Dungey, J. W. (1961), Interplanetary magnetic field and the auroral zones, Phys. Rev. Lett., 6, 47-48, doi:10.1103/PhysRevLett.6.47.
Elphinstone, R. D., J. S. Murphree, and L. L. Cogger (1996), What is a global auroral substorm?, Rev. Geophys., 34(2), 169-232, doi:10.1029/96RG00483.
Gérard, J.-C. (2006), Saturn's auroral morphology and activity during quiet magnetospheric conditions, J. Geophys. Res., 111, A12210, doi:10.1029/2006JA011965.
Gérard, J.-C., D. 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.
Gladstone, G. R., et al. (2002), A pulsating auroral X-ray hot spot on Jupiter, Nature, 415, 1000-1003, doi:10.1038/4151000a.
Goertz, C. (1978), Energization of charged particles in Jupiter's outer magnetosphere, J. Geophys. Res., 83, 3145-3150, doi:10.1029/JA083iA07p03145.
Grodent, D., J. H. Waite Jr., and J.-C. Gérard (2001), A self-consistent model of the Jovian auroral thermal structure, J. Geophys. Res., 106(A7), 12,933-12,952, doi:10.1029/2000JA900129. (Pubitemid 33729406)
Grodent, D., J. T. Clarke, J. Kim, J. H. Waite Jr., and S. W. H. Cowley (2003a), Jupiter's main auroral oval observed with HST-STIS, J. Geophys. Res., 108(A11), 1389, doi:10.1029/2003JA009921.
Grodent, D., J. T. Clarke, J. H. Waite Jr., S. W. H. Cowley, J.-C. Gérard, and J. Kim (2003b), Jupiter's polar auroral emissions, J. Geophys. Res., 108(A10), 1366, doi:10.1029/2003JA010017.
Gurnett, D. A., W. S. Kurth, and F. Scarf (1981a), Plasma waves near Saturn: Initial results from Voyager 1, Science, 212, 235-239, doi:10.1126/science.212.4491.235.
Gurnett, D. A., W. Kurth, and F. Scarf (1981b), Narrowband electromagnetic emissions from Saturn's magnetosphere, Nature, 292, 733-737, doi:10.1038/292733a0.
Gumett, D. A., et al. (2002), Control of Jupiter's radio emission and aurorae by the solar wind, Nature, 415, 985-987, doi:10.1038/415985a.
Gurnett, D., et al. (2004), The Cassini radio and plasma wave investigation, Space Sci. Rev., 114, 395-463, doi:10.1007/sl 1214-004-1434-1440 (Pubitemid 40468867)
Gustin, J., S. W. H. Cowley, J.-C. Gérard, G. R. Gladstone, D. Grodent, and J. T. Clarke (2006), Characteristics of Jovian morning bright FUV aurora from Hubble Space Telescope/Space Telescope Imaging Spectrograph imaging and spectral observations, J. Geophys. Res., 111, A09220, doi:10.1029/ 2006JA011730.
Hanlon, P. G., M. K. Dougherty, N. Krupp, K. C. Hansen, F. J. Crary, D. T. Young, and G. Tóth (2004a), Dual spacecraft observations of a compression event within the Jovian magnetosphere: Signatures of externally triggered supercorotation?, J. Geophys. Res., 109, A09S09, doi:10.1029/ 2003JA010116.
Hanlon, P. G., M. K. Dougherty, R. J. Forsyth, M. J. Owens, K. C. Hansen, G. Tóth, F. J. Crary, and D. T. Young (2004b), On the evolution of the solar wind between 1 and 5 AU at the time of the Cassini Jupiter flyby: Multispacecraft observations of interplanetary coronal mass ejections including the formation of a merged interaction region, J. Geophys. Res., 109, A09S03, doi:10.1029/2003JA010112.
Hill, T. W. (2001), The Jovian auroral oval, J. Geophys. Res., 106(A5), 8101-8107, doi:10.1029/2000JA000302.
Hill, T. W. (2004), Auroral structures at Jupiter and Earth, Adv. Space Res., 33, 2021-2029, doi:10.1016/j.asr.2003.05.037.
Hubert, B., M. Palmroth, T. V. Laitinen, P. Janhunen, S. E. Milan, A. Grocott, S. W. H. Cowley, T. Pulkkinen, and J.-C. Gérard (2006), Compression of the Earth's magnetotail by interplanetary shocks directly drives transient magnetic flux closure, Geophys. Res. Lett., 33, L10105, doi:10.1029/2006GL026008. (Pubitemid 44027538)
Kaiser, M. (1993), Time-variable magnetospheric radio emissions from Jupiter, J. Geophys. Res., 98, 18,757-18,765, doi:10.1029/93JE01279.
Kaiser, M., M. Desch, and A. Lecacheux (1981), Saturnian kilometric radiation: Statistical properties and beam geometry, Nature, 292, 731-733, doi:10.1038/292731a0.
Kurth, W. S., et al. (2005), An Earth-like correspondence between Saturn's ultraviolet auroral features and radio emission, Nature, 433, 722-725, doi:10.1038/nature03334.
Kurth, W. S., T. F. Averkamp, D. A. Gurnett, J. B. Groene, and A. Lecacheux (2008), An update to a Saturnian longitude system based on kilometric radio emissions, J. Geophys. Res., 113, A05222, doi:10.1029/2007JA012861.
Ladreiter, H., and Y. Leblanc (1989), Jovian hectometric radiation-Beaming, source extension, and solar wind control, Astron. Astrophys., 226, 297-310.
Lamy, L., P. Zarka, B. Cecconi, R. Prangé, W. S. Kurth, and D. A. Gurnett (2008), Saturn kilometric radiation: Average and statistical properties, J. Geophys. Res., 113, A07201, doi:10.1029/2007JA012900.
Livengood, T. A., W. Moos, G. Ballester, and R. Prange (1992), Jovian ultraviolet auroral activity, 1981-1991, Icarus, 97, 26-45, doi:10.1016/0019- 1035(92)90055-C.
Louarn, P., et al. (2007), Observation of similar radio signatures at Saturn and Jupiter: Implications for the magnetospheric dynamics, Geophys. Res. Lett., 34, L20113, doi:10.1029/2007GL030368. (Pubitemid 350303249)
McPherron, R. L. (1970), Growth phase of magnetospheric substorms, J. Geophys. Res., 75, 5592-5599, doi:10.1029/JA075i028p05592.
Meurant, M., J.-C. Gerard, C. Block, B. Hubert, and V. Coumans (2004), Propagation of electron and proton shock-induced aurora and the role of the interplanetary magnetic field and solar wind, J. Geophys. Res., 109, A10210, doi:10.1029/2004JA010453.
Nichols, J. D., E. J. Bunce, J. T. Clarke, S. W. H. Cowley, J.-C. Gérard, D. Grodent, and W. R. Pryor (2007), Response of Jupiter's UV auroras to interplanetary conditions as observed by the Hubble Space Telescope during the Cassini flyby campaign, J. Geophys. Res., 112, A02203, doi:10.1029/2006JA012005.
Prangé, R., P. Zarka, G. E. Ballester, T. A. Livengood, L. Denis, T. D. Carr, F. Reyes, S. J. Bame, and H. W. Moos (1993), Correlated variations of UV and Radio emissions during an outstanding Jovian auroral event, J. Geophys. Res., 98, 18,779-18,791, doi:10.1029/93JE01802.
Prangé, R., G. Chagnon, M. G. Kivelson, T. A. Livengood, and W. Kurth (2001), Temporal monitoring of Jupiter's auroral activity with IUE during the Galileo mission: Implications for magnetospheric processes, Planet. Space Sci., 49, 405-415, doi:10.1016/S0032-0633(00)00161-6. (Pubitemid 33648524)
Prangé, R., L. Pallier, K. C. Hansen, R. Howard, A. Vourlidas, R. Courtin, and C. Parkinson (2004), An interplanetary shock traced by planetary auroral storms from the Sun to Saturn, Nature, 432, 78-81, doi:10.1038/ nature02986. (Pubitemid 39490828)
Pryor, W. R., et al. (2005), Cassini UVIS observations of Jupiter's auroral variability, Icarus, 178, 312-326, doi:10.1016/j.icarus.2005.05.021. (Pubitemid 41548992)
Rucker, H. O., et al. (2008), Saturn kilometric radiation as a monitor for the solar wind?, Adv. Space Res., 42, 40-47, doi:10.1016/j.asr.2008.02.008.
Sandel, B. R., and A. Broadfoot (1981), Morphology of Saturn's aurora, Nature, 292, 679-682, doi:10.1038/292679a0.
Skinner, T. E., S. Durrance, P. Feldman, and W. Moos (1984), IUE observations of longitudinal and temporal variations in the Jovian auroral emission, Astrophys. J., 278, 441-448, doi:10.1086/161809.
Siscoe, G. L., and T. S. Huang (1985), Polar cap inflation and deflation, J. Geophys. Res., 90, 543-547, doi:10.1029/JA090iA01p00543.
Sittler, E. C., Jr., M. F. Blanc, and J. D. Richardson (2006), Proposed model for Saturn's auroral response to the solar wind: Centrifugal instability model, J.. Geophys. Res., 111, A06208, doi:10.1029/2005JA011191.
Southwood, D., and M. Kivelson (2001), A new perspective concerning the influence of the solar wind on Jupiter, J. Geophys. Res., 106, 6123-6130, doi:10.1029/2000JA000236.
Stallard, T., C. Smith, S. Miller, H. Melin, M. Lysrrup, A. Aylward, N. Achilleos, and M. Dougherty (2007), Saturn's auroral/polar H3 + infrared emission, Icarus, 191, 678-690, doi:10.1016/j.icarus.2007. 05.016.
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(E9), 20,237-20,244, doi:10.1029/98JE01324.
Waite, J. H., et al. (2001), An auroral flare at Jupiter, Nature, 410, 787-789, doi:10.1038/35071018.
Warwick, J., et al. (1981), Planetary radio astronomy observations from Voyager 1 near Saturn, Science, 212, 239-243, doi:10.1126/science.212.4491.239.
Zarka, P. (1998), Auroral radio emissions at the outer planets: Observations and theories, J. Geophys. Res., 103(E9), 20,159-20,194, doi:10.1029/98JE01323.
Zieger, B., and K. C. Hansen (2008), Statistical validation of a solar wind propagation model from 1 to 10 AU, J. Geophys. Res., 113, A08107, doi:10.1029/2008JA013046.