References of "Grodent, Denis"
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See detailThe auroral footprint of Enceladus on Saturn
Pryor, Wayne R; Rymer, Abigail M; Mitchell, Donald G et al

in Nature (2011), 472

Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus could lead to electrodynamic coupling between ... [more ▼]

Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus 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 ionosphere. 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-detection. 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. [less ▲]

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See detailDiscovery of pulsed polar flares in the Jovian aurorae
Bonfond, Bertrand ULg; Vogt, M~F; Grodent, Denis ULg et al

Poster (2010, December)

The most active part of the aurora at Jupiter is certainly the polar region, i.e. the emissions located poleward of the main auroral oval. This region is known to occasionally show localized but dramatic ... [more ▼]

The most active part of the aurora at Jupiter is certainly the polar region, i.e. the emissions located poleward of the main auroral oval. This region is known to occasionally show localized but dramatic enhancements of its brightness, referred to as polar flares. These emissions have been associated with the polar cusp, based on their location in the polar cap. In summer 2009, right after the refurbishment of the Space Telescope Imaging Spectrograph camera, the Hubble Space Telescope acquired the longest high-time resolution sequence ever of images of the Jovian aurora. We report the first observations of a quasi-periodicity in the occurrence of these flares, with a timescale of ~2-3 minutes. By using a magnetic flux mapping model, we show that these features originate from a region located at a radial distance ranging from 80 to 100 Jovian radii and local times between 10:00 and 15:00. As a consequence, by analogy with similar behaviors observed in the Earth aurora, we suggest that these emissions could be attributed to pulsed reconnections in the dayside magnetopause. [less ▲]

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See detailThe Juno Mission
Bolton, S. J.; Gérard, Jean-Claude ULg; Grodent, Denis ULg et al

in Barbieri, Cesare; Coradini, Marcello; Chakrabarti, Supriya (Eds.) et al Proceedings IAU Symposium No. 269. "Galileo's Medicean Moons: their impact on 400 years of discovery" (2010, November 03)

Juno is the next NASA New Frontiers mission which will launch in August 2011. The mission is a solar powered spacecraft scheduled to arrive at Jupiter in 2016 and be placed into polar orbit around Jupiter ... [more ▼]

Juno is the next NASA New Frontiers mission which will launch in August 2011. The mission is a solar powered spacecraft scheduled to arrive at Jupiter in 2016 and be placed into polar orbit around Jupiter. The goal of the Juno mission is to explore the origin and evolution of the planet Jupiter. Juno's science themes include (1) origin, (2) interior structure, (3) atmospheric composition and dynamics, and (4) polar magnetosphere and aurora. A total of nine instruments on-board provide specific measurements designed to investigate Juno's science themes. The primary objective of investigating the origin of Jupiter includes 1) determine Jupiter's internal mass distribution by measuring gravity with Doppler tracking, 2) determine the nature of its internal dynamo by measuring its magnetic fields with a magnetometer, and 3) determine the deep composition (in particular the global water abundance) and dynamics of the sub-cloud atmosphere around Jupiter, by measuring its thermal microwave emission. [less ▲]

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See detailComparison Of Jupiter's Infrared And Uv Aurorae With Simultaneous And Near-simultaneous HST And Ground-based Observations
Lystrup, Makenzie B; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

Conference (2010, October)

Jupiter's UV aurorae have been observed extensively for the last twenty years using the Hubble Space Telescope and the infrared aurorae have been investigated using ground-based telescope observations ... [more ▼]

Jupiter's UV aurorae have been observed extensively for the last twenty years using the Hubble Space Telescope and the infrared aurorae have been investigated using ground-based telescope observations. The two wavelength regimes complement each other; the UV is a tracer of inputs from the magnetosphere while the infrared emissions from the H3+ molecular ion show how the ionosphere responds to those inputs. Between 1995 and 2000 Spectroscopic, J.E.P Connerney & T. Satoh carried out observations with the NSFCAM imaging instrument at the NASA Infrared Telescope Facility. Results from this data set have been published, although the entire data set has not been examined and there has been only limited comparison with the UV. We reanalyze this data set in order to statistically characterize the infrared aurora and compare with the UV. Here we present a detailed study of simultaneous and near-simultaneous observations of the UV (STIS instrument on HST) and infrared northern aurorae made on July 26, 1998 and December 16, 2000. The comparative study addresses the main oval emissions, satellite footprints, and polar aurorae. M. Lystrup is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0802021. [less ▲]

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See detailJupiter's ultraviolet polar emission: a statistical study
Coumans, Valérie ULg; Bonfond, Bertrand ULg; Grodent, Denis ULg et al

Conference (2010, September)

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See detailSaturn's polar auroral emissions
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Conference (2010, June 07)

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See detailSaturn's aurora seen by HST and UVIS
Grodent, Denis ULg; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

Conference (2010, June 07)

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See detailJupiter's and Saturn's auroras as observed by the Hubble Space Telescope
Nichols, J. D.; Grodent, Denis ULg

Conference (2010, May 17)

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See detailA Far-UV Imager for the Jupiter Ganymede Orbiter
Bunce, E. J.; Molyneux, P.; Bannister, N. et al

Poster (2010, May 17)

Detailed reference viewed: 19 (2 ULg)
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See detailAuroral footprints; everywhere
Grodent, Denis ULg; Bonfond, Bertrand ULg; Radioti, Aikaterini ULg et al

Conference (2010, May 06)

Jupiter’s moons Io, Europa and Ganymede are continuously interacting with the Jovian magnetic field and with the sheet of plasma flowing near its equatorial plane. The interaction between these moons and ... [more ▼]

Jupiter’s moons Io, Europa and Ganymede are continuously interacting with the Jovian magnetic field and with the sheet of plasma flowing near its equatorial plane. The interaction between these moons and the Jovian magnetosphere causes strong Alfvénic perturbations which propagate along the magnetic field lines. On their way towards Jupiter’s polar regions, these perturbations accelerate charged particles which then interact with Jupiter’s ionosphere where they loose a fraction of their energy in the form of auroral emissions. Each of the three moons leaves an auroral footprint around the poles of Jupiter which departs from the bulk of the auroral emission. Their location is mainly controlled by the topology of the field lines and thus analysis of the auroral footprints provides information on the magnetic field itself. In that regard, the satellites auroral footpaths were used to highlight the presence of a strong magnetic anomaly in the northern hemisphere of Jupiter. Detailed inspection of the footprints’ brightness and morphology as a function of time reveals fundamental information on the interaction mechanisms near the moons, on the particles acceleration mechanisms as well as on the Jovian ionosphere. For example, it was suggested that the Io footprint actually consists of several spots resulting from successive steps in the perturbation propagation process. Another example is the finding of three different timescales in the variations of Ganymede’s footprint; each of them is pointing to a different part of the electromagnetic interaction between the moon’s mini-magnetosphere and the Jovian plasma. Several recent images of Saturn’s auroral regions obtained with Cassini/UVIS at high latitude show an obvious auroral spot at the predicted location of Enceladus’ footprint. This major finding demonstrates that the electromagnetic interaction between a moon and its parent planet is not unique to Jupiter but appears to be a common feature in planetary systems. [less ▲]

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See detailAuroral footprints of tail reconnection at Jupiter and Saturn
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Conference (2010, May 03)

Tail reconnection at Jupiter’s magnetosphere, has recently been shown to leave its signature in the aurora. The Hubble Space Telescope observed transient polar dawn spots on the Jovian aurora, with a ... [more ▼]

Tail reconnection at Jupiter’s magnetosphere, has recently been shown to leave its signature in the aurora. The Hubble Space Telescope observed transient polar dawn spots on the Jovian aurora, with a characteristic recurrence period of 2-3 days. Because of their periodic occurrence cycle and observed location, it is suggested that the transient auroral features are related to the precipitated, heated plasma during reconnection processes taking place in the Jovian magnetotail. Particularly, it is proposed that the transient auroral spots are triggered by the planetward moving flow bursts released during the process. A comparison of their properties with those of the <br />auroral spots strengthen the conclusion that they are signatures of tail reconnection. <br />Cassini recently revealed magnetotail reconnection events at Saturn similar to those observed at Jupiter. Based on the UVIS dataset we present transient features at Saturn’s polar auroral region, which are possible signatures of tail reconnection. We study their size, power, duration and duty cycle and we suggest possible triggering mechanisms associated with magnetotail dynamics. We compare these auroral emissions with those at Jupiter and we discuss how energy is transferred to the ionosphere during tail reconnection. [less ▲]

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See detailOn the origin of Saturn's outer auroral emission
Grodent, Denis ULg; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

in Journal of Geophysical Research. Space Physics (2010), 115

Ultraviolet Hubble Space Telescope images reveal a faint but distinct auroral emission equatorward of the main ring of emission of Saturn's southern polar region. This outer auroral emission is only ... [more ▼]

Ultraviolet Hubble Space Telescope images reveal a faint but distinct auroral emission equatorward of the main ring of emission of Saturn's southern polar region. This outer auroral emission is only visible near the nightside limb for the strongly tilted viewing geometry achieved in January 2004. We model the limb-brightening amplification of this emission, and we show that the observations are compatible with an ∼7° wide emission ring approximately centered on the 67°S parallel. The 1.7 kR brightness of this emission requires an injected electron energy flux of ∼0.3 mW m[SUP]‑2[/SUP]. The outer auroral emission maps to a region of the equatorial plane between 4 and 11 R[SUB]S[/SUB]. We suggest that a population of suprathermal electrons observed by Cassini can provide more than the required energy flux without the need for field-aligned acceleration. This auroral UV emission may also be associated with energetic neutral oxygen and hydrogen atoms originating from the energetic protons and O[SUP]+[/SUP] of magnetosphere and/or with a secondary infrared auroral oval. [less ▲]

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See detailUVIS FUV spectra of Saturn’s aurora
Gustin, Jacques ULg; Gérard, Jean-Claude ULg; Grodent, Denis ULg et al

Conference (2010)

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See detailSaturn's secondary auroral ring
Grodent, Denis ULg; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

Conference (2010)

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See detailAuroral signatures of flow bursts released during magnetotail reconnection at Jupiter
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Space Physics (2010), 115

Recent studies based on Hubble Space Telescope (HST) data reported the presence of transient polar dawn spots in the Jovian auroral region and interpreted them as signatures of internally driven magnetic ... [more ▼]

Recent studies based on Hubble Space Telescope (HST) data reported the presence of transient polar dawn spots in the Jovian auroral region and interpreted them as signatures of internally driven magnetic reconnection in the Jovian magnetotail. Even though an association of the polar dawn spots with the reconnection process has been suggested, it has not been yet investigated which part of the process and what mechanism powers these auroral emissions. In the present study, we examine the scenario that the auroral spots are triggered by the inward moving flow bursts released during magnetic reconnection at Jupiter. We base our analysis on a model adapted from the terrestrial case, according to which moving plasma flow burst is coupled with the ionosphere by field-aligned currents, giving rise to auroral emissions. We estimate the upward field-aligned current at the flank of the flow bursts, using in-situ magnetic field measurements and we derive the auroral emitted power. We statistically study the observed emitted power of the polar dawn spots, based on HST data from 1998 to 2007, and we compare it with the emitted power derived according to the proposed scenario. Apart from the emitted power, other properties of the polar dawn spots such as their location, periodicity, duty cycle and multiplicity suggest that they are associated with the inward moving flow bursts released during magnetic reconnection in Jupiter's tail. [less ▲]

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See detailHow large is the Io UV footprint?
Bonfond, Bertrand ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Conference (2010)

Located close to the feet of the magnetic field lines connecting Io to each Jovian hemisphere, the Io footprint is the auroral signature of the electromagnetic interaction between Io and Jupiter's ... [more ▼]

Located close to the feet of the magnetic field lines connecting Io to each Jovian hemisphere, the Io footprint is the auroral signature of the electromagnetic interaction between Io and Jupiter's magnetosphere. It consists of several spots followed downstream by an extended tail. The size of the main spot is expected to scale to the size of the interaction region close to Io. Consequently, this quantity is crucial to understand the processes involved. However, the main spot size is a controversial issue as previously published values range from ~400 km to ~10000 km, leading to contradictory conclusions. Based on observations carried on with the Hubble Space Telescope STIS and ACS FUV instruments from 1997 to 2009, we estimate the size of the main footprint spot on a much larger image sample than previously. Additionally, we carefully selected the images in order to avoid viewing geometry ambiguities when measuring the spatial extent of the different features. The main spot length along the footpath is ~900 km while its width perpendicular to the footpath is <200 km. The spot length is larger than the projected diameter of Io along unperturbed magnetic field lines, which appears to be consistent with recent simulations. The vertical extent and the peak altitude of the main spot are similar to those measured in the tail. Nevertheless, the secondary spot attributed to trans-hemispheric electron beams has been measured to peak at ∼200 km below the main spot and the tail, which confirms their different origins. [less ▲]

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See detailHow bright is the Io UV footprint?
Bonfond, Bertrand ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Conference (2010)

The electro-magnetic interaction between Io and the Jovian magnetosphere generates a perturbation in the magnetospheric plasma which propagates along the magnetic field lines and creates auroral footprint ... [more ▼]

The electro-magnetic interaction between Io and the Jovian magnetosphere generates a perturbation in the magnetospheric plasma which propagates along the magnetic field lines and creates auroral footprint emissions in both hemispheres. Recent results showed that this footprint is formed of several spots and an extended tail. Each feature is suggested to correspond to a different step in the propagation of the perturbation and in the electron energization processes. The present study focuses on the variations of the spots' brightness at different timescales from minutes to years through the rotation period of Jupiter. It relies on FUV images acquired with the STIS and ACS instruments onboard the Hubble Space Telescope. Since the footprint is composed of several localized features, a good understanding of the emission region geometry is critical to derive the actual vertical brightness and thus the precipitated energy flux. We developed a 3D emission model in order to assess as precisely as possible the respective contribution of each individual feature and to correctly estimate the precipitating energy flux. As far as the brightness variations on timescales of minutes are concerned, we will present results from the high time resolution campaign executed during summer 2009. On timescale of several hours, we will show that the variation of the emitted power as a function of the location of Io in the plasma torus suggests that the Jovian surface magnetic field strength is an important controlling parameter. Finally, the measured precipitated power and particle fluxes will be discussed in comparison with recent simulations considering both Alfvén waves filamentation and electron acceleration when the Alfvén waves become inertial. [less ▲]

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See detailModeling of the longitudinal modulation of the Io interaction
Hess, S.; Bonfond, Bertrand ULg; Delamere, P. A. et al

Poster (2010)

The Io interaction with the Jovian magnetosphere is the best known case of moon-magnetosphere interaction. It leads to bright emissions from radio to UV, which are mostly due to the acceleration of ... [more ▼]

The Io interaction with the Jovian magnetosphere is the best known case of moon-magnetosphere interaction. It leads to bright emissions from radio to UV, which are mostly due to the acceleration of electrons by Alfvén waves along the magnetic field lines passing Io. We previously presented a model of the electron acceleration by the Iogenic Alfvén waves, which explains the average brightness of the emissions. We now present a study of the modulation of the Io-magnetosphere interaction with longitude, and compare our results with the observed brightness modulation of the auroral emissions. This study highlights how the satellite-magnetosphere interactions depend on the variation of the magnetic field, the equatorial plasma density,... A new model of the Jovian internal magnetic field, giving an accurate description of the longitudinal modulations of the Jovian magnetic field has been computed for this study, and is also presented. [less ▲]

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