References of "Gustin, Jacques"
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See detailSimultaneous Cassini VIMS and UVIS observations of Saturn's southern aurora: Comparing emissions from H, H2 and H3+ at a high spatial resolution
Melin, H.; Stallard, T.; Miller, S. et al

in Geophysical Research Letters (2011), 38

Here, for the first time, temporally coincident and spatially overlapping Cassini VIMS and UVIS observations of Saturn's southern aurora are presented. Ultraviolet auroral H and H[SUB]2[/SUB] emissions ... [more ▼]

Here, for the first time, temporally coincident and spatially overlapping Cassini VIMS and UVIS observations of Saturn's southern aurora are presented. Ultraviolet auroral H and H[SUB]2[/SUB] emissions from UVIS are compared to infrared H[SUB]3[/SUB][SUP]+[/SUP] emission from VIMS. The auroral emission is structured into three arcs - H, H[SUB]2[/SUB] and H[SUB]3[/SUB][SUP]+[/SUP] are morphologically identical in the bright main auroral oval (˜73°S), but there is an equatorward arc that is seen predominantly in H (˜70°S), and a poleward arc (˜74°S) that is seen mainly in H[SUB]2[/SUB] and H[SUB]3[/SUB][SUP]+[/SUP]. These observations indicate that, for the main auroral oval, UV emission is a good proxy for the infrared H[SUB]3[/SUB][SUP]+[/SUP] morphology (and vice versa), but for emission either poleward or equatorward this is no longer true. Hence, simultaneous UV/IR observations are crucial for completing the picture of how the atmosphere interacts with the magnetosphere. [less ▲]

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See detailCassini UVIS Observations of Varying Auroral Emissions on Saturn's Night Side
Pryor, W.; Esposito, L.; Jouchoux, A. et al

Poster (2011, July 11)

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See detailAuroral signatures of injections in the magnetosphere of Saturn
Radioti, Aikaterini ULg; Roussos, E.; Grodent, Denis ULg et al

Poster (2011, July 11)

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See detailInside the Jupiter Main Auroral Emissions: Flares, Spots, Arc...and Satellite Footprints?
Bonfond, Bertrand ULg; Vogt, M. F.; Yoneda, M. et al

Conference (2011, July 11)

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See detailThe multiple spots of the Ganymede footprint
Bonfond, Bertrand ULg; Hess, S.; Grodent, Denis ULg et al

Poster (2011, July 11)

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See detailThe production of Titan's ultraviolet nitrogen airglow
Stevens, Michael H; Gustin, Jacques ULg; Ajello, Joseph M et al

in Journal of Geophysical Research. Space Physics (2011), 116

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Titan's dayside limb in the extreme ultraviolet (EUV) and far ultraviolet (FUV) on 22 June 2009 from a mean distance of 23 Titan radii. These ... [more ▼]

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Titan's dayside limb in the extreme ultraviolet (EUV) and far ultraviolet (FUV) on 22 June 2009 from a mean distance of 23 Titan radii. These high-quality observations reveal the same EUV and FUV emissions arising from photoelectron excitation and photofragmentation of molecular nitrogen (N[SUB]2[/SUB]) as found on Earth. We investigate both of these solar driven processes with a terrestrial airglow model adapted to Titan and find that total predicted radiances for the two brightest N[SUB]2[/SUB] band systems agree with the observed peak radiances to within 5%. Using N[SUB]2[/SUB] densities constrained from in situ observations by the Ion Neutral Mass Spectrometer on Cassini, the altitude of the observed limb peak of the EUV and FUV emission bands is between 840 and 1060 km and generally consistent with model predictions. We find no evidence for carbon emissions in Titan's FUV airglow in contrast to previous Titan airglow studies using UVIS data. In their place, we identify several vibrational bands from the N[SUB]2[/SUB] Vegard-Kaplan system arising from photoelectron impact with predicted peak radiances in agreement with observations. These Titan UV airglow observations are therefore comprised of emissions arising only from solar processes on N[SUB]2[/SUB] with no detectable magnetospheric contribution. Weaker EUV Carroll-Yoshino N[SUB]2[/SUB] bands within the v′ = 3, 4, and 6 progressions between 870 and 1020 Å are underpredicted by about a factor of five while the (0,1) band near 980 Å is overpredicted by about a factor of three. [less ▲]

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See detailEUV spectroscopy of the Venus dayglow with UVIS on Cassini
Gérard, Jean-Claude ULg; Hubert, Benoît ULg; Gustin, Jacques ULg et al

in Icarus: International Journal of Solar System Studies (2011), 211

We analyze EUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus on 24 June 1999, a period of high solar activity level. Emissions ... [more ▼]

We analyze EUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus on 24 June 1999, a period of high solar activity level. Emissions from OI, OII, NI, CI and CII and CO have been identified and their disc average intensity has been determined. They are generally somewhat brighter than those determined from the observations made with the HUT spectrograph at a lower activity level, We present the brightness distribution along the foot track of the UVIS slit of the OII 83.4 nm, OI 98.9 nm, Lyman-ß + OI 102.5 nm and NI 120.0 nm multiplets, and the CO C-X and B-X Hopfield-Birge bands. We make a detailed comparison of the intensities of the 834 nm, 989 nm, 120.0 nm multiplets and CO B-X band measured along the slit foot track on the disc with those predicted by an airglow model previously used to analyze Venus and Mars ultraviolet spectra. This model includes the treatment of multiple scattering for the optically thick OI, OII and NI multiplets. It is found that the observed intensity of the OII emission at 83.4 nm is higher than predicted by the model. An increase of the O[SUP]+[/SUP] ion density relative to the densities usually measured by Pioneer Venus brings the observations and the modeled values into better agreement. The calculated intensity variation of the CO B-X emission along the track of the UVIS slit is in fair agreement with the observations. The intensity of the OI 98.9 nm emission is well predicted by the model if resonance scattering of solar radiation by O atoms is included as a source. The calculated brightness of the NI 120 nm multiplet is larger than observed by a factor of ˜2-3 if photons from all sources encounter multiple scattering. The discrepancy reduces to 30-80% if the photon electron impact and photodissociation of N[SUB]2[/SUB] sources of N([SUP]4[/SUP]S) atoms are considered as optically thin. Overall, we find that the O, N[SUB]2[/SUB] and CO densities from the empirical VTS3 model provide satisfactory agreement between the calculated and the observed EUV airglow emissions. [less ▲]

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See detailSmall-scale structures in Saturn's ultraviolet aurora
Grodent, Denis ULg; Gustin, Jacques ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Space Physics (2011), 116

On 26 August 2008, the Ultraviolet Imaging Spectrograph Subsystem (UVIS) instrument onboard the Cassini spacecraft recorded a series of spatially resolved spectra of the northern auroral region of Saturn ... [more ▼]

On 26 August 2008, the Ultraviolet Imaging Spectrograph Subsystem (UVIS) instrument onboard the Cassini spacecraft recorded a series of spatially resolved spectra of the northern auroral region of Saturn. Near periapsis, the spacecraft was only five Saturn radii (R[SUB]S[/SUB]) from the surface and spatially resolved auroral structures as small as 500 km across (0.5° of latitude). We report the observation of two types of UV auroral substructures at the location of the main ring of emission, bunches of spots and narrow arcs. They are found in the noon and dusk sectors, respectively, at latitudes ranging from 73 to 80° corresponding to equatorial regions located beyond 16 R[SUB]S[/SUB]. Their brightness ranges from 1 to 30 kR and their characteristic size varies from 500 km to several thousands of km. These small-scale substructures are likely associated with patterns of upward field aligned currents resulting from nonuniform plasma flow in the equatorial plane. It is suggested that magnetopause Kelvin-Helmholtz waves trigger localized perturbations in the flow, like vortices, able to give rise to the observed UV auroral substructures. [less ▲]

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See detailBifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Space Physics (2011), 116

This work reports for the first time on bifurcations of the main auroral ring at Saturn observed with the UVIS instrument onboard Cassini. The observation sequence starts with an intensification on the ... [more ▼]

This work reports for the first time on bifurcations of the main auroral ring at Saturn observed with the UVIS instrument onboard Cassini. The observation sequence starts with an intensification on the main oval, close to noon, which is possibly associated with dayside reconnection. Consecutive bifurcations appear with the onset of dayside reconnection, between 11 and 18 magnetic local time, while the area poleward of the main emission expands to lower latitudes. The bifurcations depart with time from the main ring of emission, which is related to the open-closed field line boundary. The augmentation of the area poleward of the main emission following its expansion is balanced by the area occupied by the bifurcations, suggesting that these auroral features represent the amount of newly open flux and could be related to consecutive reconnection events at the flank of the magnetopause. The observations show that the open flux along the sequence increases when bifurcations appear. Magnetopause reconnection can lead to significant augmentation of the open flux within a couple of days and each reconnection event opens ∼10% of the flux contained within the polar cap. Additionally, the observations imply an overall length of the reconnection line of ∼4 hours of local time and suggest that dayside reconnection at Saturn can occur at several positions on the magnetopause consecutively or simultaneously. [less ▲]

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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 detailThe Production of Titan's Ultraviolet Nitrogen Airglow
Stevens, Michael H.; Gustin, Jacques ULg; Ajello, J. M. et al

in AAS/Division for Planetary Sciences Meeting Abstracts #42 (2010, October 01)

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Titan's dayside limb on 22 June, 2009, obtaining high quality extreme ultraviolet (EUV) and far ultraviolet (FUV) spectra from a distance of ... [more ▼]

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Titan's dayside limb on 22 June, 2009, obtaining high quality extreme ultraviolet (EUV) and far ultraviolet (FUV) spectra from a distance of only 60,000 km (23 Titan radii). The observations reveal the same EUV and FUV emissions arising from photoelectron excitation and photofragmentation of molecular nitrogen (N[SUB]2[/SUB]) on Earth but with the altitude of peak emission much higher on Titan near 1000 km altitude. In the EUV, emission bands from the photoelectron excited N[SUB]2[/SUB] Carroll-Yoshino c[SUB]4[/SUB]'-X system and N I and N II multiplets arising from photofragmentation of N[SUB]2[/SUB] dominate, with no detectable c[SUB]4[/SUB]'(0,0) emission near 958 Å, contrary to many interpretations of the lower resolution Voyager 1 Ultraviolet Spectrometer data. The FUV is dominated by emission bands from the N[SUB]2[/SUB] Lyman-Birge-Hopfield a-X system and additional N I multiplets. We also identify several N[SUB]2[/SUB] Vegard-Kaplan A-X bands between 1500-1900 Å, two of which are located near 1561 and 1657 Å where C I multiplets were previously identified from a separate UVIS disk observation. We compare these limb emissions to predictions from a terrestrial airglow model adapted to Titan that uses a solar spectrum appropriate for these June, 2009 observations. Volume production rates and limb radiances are calculated, including extinction by methane and allowance for multiple scattering within the readily excited c[SUB]4[/SUB]'(0,v') system, and compared to UVIS observations. We find that for these airglow data only emissions arising from processes involving N[SUB]2[/SUB] are present. [less ▲]

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See detailSaturn's radio, UV and IR aurorae observed simultaneously by Cassini
Lamy, L.; Prangé, R.; Gustin, Jacques ULg et al

in European Planetary Science Congress 2010 (2010, September 01)

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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 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 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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