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The auroral footprint of Enceladus on Saturn

Nature volume 472, pages 331–333 (2011)Cite this article

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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.

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Acknowledgements

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

Author information

Author notes

  1. Wayne R. Pryor and Abigail M. Rymer: These authors contributed equally to this work.

Authors and Affiliations

  1. Science Department, Central Arizona College, Coolidge, 85128, Arizona, USA

    Wayne R. Pryor

  2. Space Environment Technologies, Pacific Palisades, 90272, California, USA

    Wayne R. Pryor

  3. Applied Physics Laboratory, Johns Hopkins University, Laurel, 20723, Maryland, USA

    Abigail M. Rymer, Donald G. Mitchell, Barry H. Mauk & Stamatios M. Krimigis

  4. Department of Physics and Astronomy, Rice University, Houston, 77005, Texas, USA

    Thomas W. Hill

  5. Space Science and Engineering Division, Southwest Research Institute, San Antonio, 78238, Texas, USA

    David T. Young & Frank J. Crary

  6. Institut für Geophysik und Meteorologie, Universität zu Köln, Cologne, D-50923, Germany

    Joachim Saur & Sven Jacobsen

  7. Department of Space and Climate Physics, Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK

    Geraint H. Jones & Andrew J. Coates

  8. The Centre for Planetary Sciences at University College London/Birkbeck, London WC1E 6BT, UK

    Geraint H. Jones

  9. Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK

    Stan W. H. Cowley & Jonathan D. Nichols

  10. Département d'Astrophysique, Laboratoire de Physique Atmosphérique et Planétaire, Géophysique et Océanographie, Université de Liège, Liège, B-4000, Belgium

    Jacques Gustin, Denis Grodent & Jean-Claude Gérard

  11. Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, Université Paris Diderot, 92195 Meudon, France

    Laurent Lamy

  12. Academy of Athens, Soranou Efesiou 4, 115 27, Athens, Greece

    Stamatios M. Krimigis

  13. Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, 80303, Colorado, USA

    Larry W. Esposito, Alain J. Jouchoux, A. Ian F. Stewart, William E. McClintock & Gregory M. Holsclaw

  14. Space and Atmospheric Physics, The Blackett Laboratory, Imperial College, London SW7 2AZ, UK

    Michele K. Dougherty

  15. Jet Propulsion Laboratory, Pasadena, 91109, California, USA

    Joseph M. Ajello, Amanda R. Hendrix & Xiaoyan Zhou

  16. Department of Physics, University of Central Florida, Orlando, 32816, Florida, USA

    Joshua E. Colwell

  17. Astronomy Department, Boston University, Boston, 02215, USA

    John T. Clarke

Authors
  1. Wayne R. Pryor
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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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