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The auroral footprint of Enceladus on Saturn

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Abstract

Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus1,2,3,4,5,6,7,8,9 could lead to electrodynamic coupling between Enceladus and Saturn like that which links Jupiter with Io, Europa and Ganymede. Powerful field-aligned electron beams associated with the Io–Jupiter coupling, for example, create an auroral footprint in Jupiter’s ionosphere10,11. Auroral ultraviolet emission associated with Enceladus–Saturn coupling is anticipated to be just a few tenths of a kilorayleigh (ref. 12), about an order of magnitude dimmer than Io’s footprint and below the observable threshold, consistent with its non-detection13. Here we report the detection of magnetic-field-aligned ion and electron beams (offset several moon radii downstream from Enceladus) with sufficient power to stimulate detectable aurora, and the subsequent discovery of Enceladus-associated aurora in a few per cent of the scans of the moon’s footprint. The footprint varies in emission magnitude more than can plausibly be explained by changes in magnetospheric parameters—and as such is probably indicative of variable plume activity.

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Figure 1: Cassini particle and field observations on 11 August 2008.
Figure 2: Cassini images of Saturn’s northern aurora, including the Enceladus auroral footprint.

References

  1. Porco, C. C. et al. Cassini observes the active south pole of Enceladus. Science 311, 1393–1401 (2006)

    Article  ADS  CAS  Google Scholar 

  2. Spencer, J. R. et al. Cassini encounters Enceladus: background and the discovery of a south polar hot spot. Science 311, 1401–1405 (2006)

    Article  ADS  CAS  Google Scholar 

  3. Dougherty, M. K. et al. Identification of a dynamic atmosphere at Enceladus with the Cassini magnetometer. Science 311, 1406–1409 (2006)

    Article  ADS  CAS  Google Scholar 

  4. Tokar, R. L. et al. The interaction of the atmosphere of Enceladus with Saturn's plasma. Science 311, 1409–1412 (2006)

    Article  ADS  CAS  Google Scholar 

  5. Jones, G. H. et al. Enceladus' varying imprint on the magnetosphere of Saturn. Science 311, 1412–1415 (2006)

    Article  ADS  CAS  Google Scholar 

  6. Spahn, F. et al. Cassini dust measurements at Enceladus and implications for the origin of the E ring. Science 311, 1416–1418 (2006)

    Article  ADS  CAS  Google Scholar 

  7. Waite, J. H. et al. Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure. Science 311, 1419–1422 (2006)

    Article  ADS  CAS  Google Scholar 

  8. Hansen, C. J. et al. Enceladus' water vapor plume. Science 311, 1422–1425 (2006)

    Article  ADS  CAS  Google Scholar 

  9. Brown, R. H. et al. Composition and physical properties of Enceladus' surface. Science 311, 1425–1428 (2006)

    Article  ADS  CAS  Google Scholar 

  10. Connerney, J. E. P., Baron, R., Satoh, T. & Owen, T. Images of excited H3 + at the foot of the Io flux tube in Jupiter's atmosphere. Science 262, 1035–1038 (1993)

    Article  ADS  CAS  Google Scholar 

  11. Clarke, J. T. et al. Ultraviolet emissions from the magnetic footprints of Io, Ganymede, and Europa on Jupiter. Nature 415, 997–1000 (2002)

    Article  ADS  CAS  Google Scholar 

  12. Pontius, D. H., Jr & Hill, T. W. Enceladus: a significant plasma source for Saturn's magnetosphere. J. Geophys. Res. 111 A09214 10.1029/2006JA011674 (2006)

    Article  ADS  Google Scholar 

  13. Wannawichian, S., Clarke, J. T. & Pontius, D. H., Jr Interaction evidence between Enceladus' atmosphere and Saturn's magnetosphere. J. Geophys. Res. 113 A07217 10.1029/2007JA012899 (2008)

    Article  ADS  Google Scholar 

  14. Gurnett, D. A. & Goertz, C. K. Multiple Alfven wave reflections excited by Io, origin of the Jovian decametric arcs. J. Geophys. Res. 86 (A2). 717–722 (1981)

    Article  ADS  Google Scholar 

  15. Bonfond, B. et al. UV Io footprint leading spot: a key feature for understanding the UV Io footprint multiplicity? Geophys. Res. Lett. 35 L05107 10.1029/2007GL032418 (2008)

    Article  ADS  CAS  Google Scholar 

  16. Jacobsen, S. J. et al. Location and spatial shape of electron beams in Io’s wake. J. Geophys. Res. 115 A04205 10.1029/2009JA014753 (2010)

    Article  ADS  Google Scholar 

  17. Persoon, A. M., Gurnett, D. A., Kurth, W. S. & Groene, J. B. A simple scale height model of the electron density in Saturn’s plasma disk. Geophys. Res. Lett. 33 L18106 10.1029/2006GL027090 (2006)

    Article  ADS  Google Scholar 

  18. Saur, J. et al. Evidence for temporal variability of Enceladus' gas jets: modeling of Cassini observations. Geophys. Res. Lett. 35 L20105 10.1029/2008GL035811 (2008)

    Article  ADS  Google Scholar 

  19. Smith, H. T. et al. Enceladus plume variability and the neutral gas densities in Saturn's magnetosphere. J. Geophys. Res. 115 A10252 10.1029/2009JA015184 (2010)

    Article  ADS  CAS  Google Scholar 

  20. Esposito, L. W. et al. the Cassini ultraviolet imaging spectrograph investigation. Space Sci. Rev. 115, 299–361 (2004)

    Article  ADS  CAS  Google Scholar 

  21. Gérard, J.-C. et al. Altitude of Saturn's aurora and its implications for the characteristic energy of precipitated electrons. Geophys. Res. Lett. 36 L02202 10.1029/2008GL036554 (2009)

    Article  ADS  CAS  Google Scholar 

  22. Burton, M. E., Dougherty, M. K. & Russell, C. T. Model of Saturn's internal planetary magnetic field based on Cassini observations. Planet. Space Sci. 57, 1706–1713 (2009)

    Article  ADS  Google Scholar 

  23. Connerney, J. E. P., Acuñna, M. H., Ness, N. F. & Satoh, T. New models of Jupiter's magnetic field constrained by the Io flux tube footprint. J. Geophys. Res. 103, 11929–11939 (1998)

    Article  ADS  Google Scholar 

  24. Nichols, J. D. et al. Saturn’s equinoctial auroras. Geophys. Res. Lett. 36 L24102 10.1029/2009GL041491 (2009)

    Article  ADS  Google Scholar 

  25. Kanani, S. J. et al. A new form of Saturn’s magnetopause using a dynamic pressure balance model, based on in situ, multi-instrument Cassini measurements. J. Geophys. Res. 115 A06207 10.1029/2009JA014262 (2010)

    Article  ADS  Google Scholar 

  26. Krimigis, S. M. et al. Magnetospheric imaging instrument (MIMI) on the Cassini mission to Saturn/Titan. Space Sci. Rev. 114, 233–329 (2004)

    Article  ADS  CAS  Google Scholar 

  27. Young, D. T. et al. Cassini plasma spectrometer investigation. Space Sci. Rev. 114, 1–112 (2004)

    Article  ADS  CAS  Google Scholar 

  28. Dougherty, M. K. et al. The Cassini magnetic field investigation. Space Sci. Rev. 114, 331–383 (2004)

    Article  ADS  Google Scholar 

  29. Jia, Y.-D. et al. Time varying magnetospheric environment near Enceladus as seen by the Cassini magnetometer. Geophys. Res. Lett. 37 L09203 10.1029/2010GL042948 (2010)

    Article  ADS  CAS  Google Scholar 

  30. Waite, J., Jr et al. Electron precipitation and related aeronomy of the Jovian thermosphere and ionosphere. J. Geophys. Res. 88, 6143–6163 (1983)

    Article  ADS  CAS  Google Scholar 

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Acknowledgements

We acknowledge support from the NASA/ESA Cassini Project and NASA's Cassini Data Analysis Program.

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Authors and Affiliations

Authors

Contributions

A.M.R. and W.R.P. discovered the electron beams and the auroral footprint, respectively, and wrote most of the paper. D.G.M. discovered the ion beams and contributed to the text and interpretation. T.W.H. contributed extensively to the text and interpretation. D.T.Y. is CAPS PI and contributed extensively to the text and interpretation. J.S., G.H.J., S.J., B.H.M. and A.J.C. advised on the interpretation of the in situ data. S.W.H.C. performed the field line mapping and provided advice on the paper. J.G., D.G., J.-C.G., L.L. and J.D.N. advised on the interpretation of the UVIS data. S.M.K. is the MIMI PI and oversaw the ion data. M.K.D. is the MAG PI and oversaw the magnetometer data. L.W.E. is the UVIS PI and oversaw the UVIS data. A.J.J. and F.J.C. designed the auroral observation campaign. A.I.F.S., W.E.M., J.M.A., J.E.C. and A.R.H. helped to process the UVIS data. J.T.C. provided advice on the HST observations. X.Z. contributed to auroral discussions related to comparisons with terrestrial auroral processes.

Corresponding author

Correspondence to Abigail M. Rymer.

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The authors declare no competing financial interests.

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Pryor, W., Rymer, A., Mitchell, D. et al. The auroral footprint of Enceladus on Saturn. Nature 472, 331–333 (2011). https://doi.org/10.1038/nature09928

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