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The auroral footprint of Enceladus on Saturn



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

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Authors and Affiliations



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.

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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).

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