The auroral footprint of Enceladus on Saturn

Pryor, W. R.; Rymer, A. M.; Mitchell, D. G.; Hill, T. W.; Young, D. T.; Saur, Joachim; Jones, G. H.; Jacobsen, Sven; Cowley, S. W. H.; Mauk, B. H.; Coates, A. J.; Gustin, Jacques; Grodent, Denis; Gérard, Jean‐Claude; Lamy, Laurent; Nichols, J. D.; Krimigis, S. M.; Esposito, L. W.; Dougherty, M. K.; Jouchoux, A.; Stewart, A. I. F.; McClintock, W. E.; Holsclaw, Gregory M.; Ajello, J. M.; Colwell, Joshua; Hendrix, Amanda; Crary, F. J.; Clarke, J. T.; Zhou, X.

doi:10.1038/nature09928

Cited by 90 publications

(80 citation statements)

References 30 publications

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“…The value thus rather needs to be considered an upper limit. Based on the observed brightness a footprint size corresponding to 1.3 R Enceladus with a downstream extension of 20 R Enceladus would lead to an auroral electron energy input of ∼1−4 × 10 6 W assuming 1 kR requires an energy input of 1 × 10 −4 W m −2 (Pryor et al 2011). Thus the predicted Poynting flux is larger and sufficient to account for the UV observations and its large extension.…”

Section: Poynting Flux: Saturn's Inner Icy Satellitesmentioning

confidence: 99%

“…At Saturn so far only an Enceladus footprint has been observed by Pryor et al (2011). The observed spot brightness in the UV ranges from 0.45 to 1.55 kR with the size of the spots possibly extending 20 R Enceladus downstream.…”

Section: Poynting Flux: Saturn's Inner Icy Satellitesmentioning

confidence: 99%

“…Recently, Cassini spacecraft observations identified a significant sub-Alfvénic interaction at Saturn's satellite Enceladus generated by geyser activity near its south pole (Dougherty et al 2006;Tokar et al 2006;Khurana et al 2007;Saur et al 2007Saur et al , 2008Kriegel et al 2009;Jia et al 2010;Simon et al 2011a). The Alfvén waves launched near Enceladus also generate footprints in Saturn's upper atmosphere as recently discovered (Pryor et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Saur

Grambusch

Duling

et al. 2013

A&A

176

332

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Context. Electromagnetic coupling of planetary moons with their host planets is well observed in our solar system. Similar couplings of extrasolar planets with their central stars have been studied observationally on an individual as well as on a statistical basis. Aims. We aim to model and to better understand the energetics of planet star and moon planet interactions on an individual and as well as on a statistical basis. Methods. We derived analytic expressions for the Poynting flux communicating magnetic field energy from the planetary obstacle to the central body for sub-Alfvénic interaction. We additionally present simplified, readily useable approximations for the total Poynting flux for small Alfvén Mach numbers. These energy fluxes were calculated near the obstacles and thus likely present upper limits for the fluxes arriving at the central body. We applied these expressions to satellites of our solar system and to HD 179949 b. We also performed a statistical analysis for 850 extrasolar planets. Results. Our derived Poynting fluxes compare well with the energetics and luminosities of the satellites' footprints observed at Jupiter and Saturn. We find that 295 of 850 extrasolar planets are possibly subject to sub-Alfvénic plasma interactions with their stellar winds, but only 258 can magnetically connect to their central stars due to the orientations of the associated Alfvén wings. The total energy fluxes in the magnetic coupling of extrasolar planets vary by many orders of magnitude and can reach values larger than 10 19 W. Our calculated energy fluxes generated at HD 179949 b can only explain the observed energy fluxes for exotic planetary and stellar magnetic field properties. In this case, additional energy sources triggered by the Alfvén wave energy launched at the extrasolar planet might be necessary. We provide a list of extrasolar planets where we expect planet star coupling to exhibit the largest energy fluxes. As supplementary information we also attach a table of the modeled stellar wind plasma properties and possible Poynting fluxes near all 850 extrasolar planets included in our study. Conclusions. The orders of magnitude variations in the values for the total Poynting fluxes even for close-in extrasolar planets provide a natural explanation why planet star coupling might have been only observable on an individual basis but not on a statistical basis.

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Section: Poynting Flux: Saturn's Inner Icy Satellitesmentioning

confidence: 99%

Section: Poynting Flux: Saturn's Inner Icy Satellitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Saur

Grambusch

Duling

et al. 2013

A&A

176

332

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“…In addition to these aurorae, each moon also has currents that flow through the perturbed plasma in the moon's vicinity, producing discrete spots of auroral emission on the planet [11,12]. Jupiter also has a mid-to-low latitude emission that varies between approximately 1 per cent and 40 per cent of the peak auroral emission; the source for this emission remains unexplained [13].…”

Section: In the Giant Planetsmentioning

confidence: 99%

Temperature changes and energy inputs in giant planet atmospheres: what we are learning from H ₃ ⁺

Stallard

Melin

Miller

et al. 2012

Phil. Trans. R. Soc. A.

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Since its discovery at Jupiter in 1988, emission from H + 3 has been used as a valuable diagnostic tool in our understanding of the upper atmospheres of the giant planets. One of the lasting questions we have about the giant planets is why the measured upper atmosphere temperatures are always consistently hotter than the temperatures expected from solar heating alone. Here, we describe how H at Saturn and the first profile of H + 3 emission at Uranus not significantly distorted by the effects of the Earth's atmosphere. We also review past observations of variations in temperature measured at Uranus and Jupiter over a wide variety of time scales. To this, we add new observations of temperature changes at Saturn, using observations by Cassini. We conclude that the causes of the significant level of thermal variability observed over all three planets is not only an important question in itself, but that explaining these variations could be the key to answering the more general question of why giant planet upper atmospheres are so hot.

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“…Clarke et al 1998). At Saturn, analogous footpoint emissions from Enceladus have been observed (Pryor et al 2011). Footpoint emissions associated with Titan have yet to be identified, however the motion of Titan itself has the potential for modulating Saturn's kilometric radiation (SKR)-a phenomenon which is associated with the auroral process (Menietti et al 2007).…”

Section: General Propertiesmentioning

confidence: 99%

Transport of Mass, Momentum and Energy in Planetary Magnetodisc Regions

Achilleos

André

Blanco‐Cano

et al. 2015

The Magnetodiscs and Aurorae of Giant Planets

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The rapid rotation of the gas giant planets, Jupiter and Saturn, leads to the formation of magnetodisc regions in their magnetospheric environments. In these regions, relatively cold plasma is confined towards the equatorial regions, and the magnetic field generated by the azimuthal (ring) current adds to the planetary dipole, forming radially distended field lines near the equatorial plane. The ensuing force balance in the equatorial magnetodisc is strongly influenced by centrifugal stress and by the thermal pressure of hot ion populations, whose thermal energy is large compared to the magnitude of their centrifugal potential energy. The sources of plasma for the Jovian and Kronian magnetospheres are the respective satellites Io (a volcanic moon) and Enceladus (an icy moon). The plasma produced by these N.

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The auroral footprint of Enceladus on Saturn

Cited by 90 publications

References 30 publications

Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Temperature changes and energy inputs in giant planet atmospheres: what we are learning from H ₃ ⁺

Transport of Mass, Momentum and Energy in Planetary Magnetodisc Regions

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The auroral footprint of Enceladus on Saturn

Cited by 90 publications

References 30 publications

Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Temperature changes and energy inputs in giant planet atmospheres: what we are learning from H 3 +

Transport of Mass, Momentum and Energy in Planetary Magnetodisc Regions

Contact Info

Product

Resources

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Temperature changes and energy inputs in giant planet atmospheres: what we are learning from H ₃ ⁺