References of "Gérard, Jean-Claude"
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See detailThe energy the auroral electrons in Saturn's atmosphere : remote sensing and thermal consequences
Gérard, Jean-Claude ULg; Gustin, Jacques ULg; Grodent, Denis ULg et al

Poster (2011, October)

Saturn’s north aurora has been observed between January and May 2011 with the Hubble Space Telescope. The objective was to collect spatially resolved spectra at the different local time from dawn to dusk ... [more ▼]

Saturn’s north aurora has been observed between January and May 2011 with the Hubble Space Telescope. The objective was to collect spatially resolved spectra at the different local time from dawn to dusk and compare them with laboratory or synthetic spectra. For this purpose, HST was programmed to slew from mid-latitudes through the auroral oval up to above the limb while collecting data in the timetag mode. The spectra show signatures of absorption by hydrocarbons present above the peak of the auroral emission. The amount of absorption and implications in terms of penetration of the auroral electron beam into Saturn’s atmosphere will be discussed and compared with other determinations of the altitude of the aurora. The effects of the auroral heat import on the thermal structure of the atmosphere both at high and low altitudes will be examined in the light of these results. [less ▲]

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See detailThe Venus visible oxygen nightglow with VIRTIS on board Venus Express
Migliorini, A.; Piccioni, G.; Gérard, Jean-Claude ULg et al

Scientific conference (2011, October)

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See detailDetection of Auroral Emissions from Callisto’s Magnetic Footprint at Jupiter
Clarke, J. T.; Wannawichian, S.; Hernandez, N. et al

Poster (2011, October)

HST observations of Jupiter’s aurora in a large campaign reveal several cases where the main oval emission appeared at unusually low latitudes, making it possible to search for the first time for auroral ... [more ▼]

HST observations of Jupiter’s aurora in a large campaign reveal several cases where the main oval emission appeared at unusually low latitudes, making it possible to search for the first time for auroral emissions from the magnetic footprint of Callisto without the overlapping bright emissions from the main oval. Several cases have been found where point-source emissions have now been detected from locations consistent with Callisto’s magnetic footprint on Jupiter at a brightness of ten’s of kilo- Rayleighs. These observations confirm that there is an electrodynamic interaction between Callisto and Jupiter’s magnetospheric environment that is similar to those at Io, Europa, and Ganymede, which all have auroral footprints. The properties of the emissions and a comparison with other observations and theoretical expectations will be presented in this paper. [less ▲]

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See detailThe OH Venus nightglow : morphology and relation to ozone in the upper atmosphere
Soret, Lauriane ULg; Gérard, Jean-Claude ULg; Piccioni, G. et al

Conference (2011, October)

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See detailJUDE: A Far-UV Imager for JUICE
Grodent, Denis ULg; Bunce, Emma; Bannister, Nigel et al

Poster (2011, August 31)

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See detailUnderstanding the variability of nightside temperatures, NO UV and O2 IR nightglow emissions in the Venus upper atmosphere
Brecht, A. S.; Bougher, S. W.; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Planets (2011), 116

Venus Express (VEX) has been monitoring key nightglow emissions and thermal features (O[SUB]2[/SUB] IR nightglow, NO UV nightglow, and nightside temperatures) which contribute to a comprehensive ... [more ▼]

Venus Express (VEX) has been monitoring key nightglow emissions and thermal features (O[SUB]2[/SUB] IR nightglow, NO UV nightglow, and nightside temperatures) which contribute to a comprehensive understanding of the global dynamics and circulation patterns above ˜90 km. The nightglow emissions serve as effective tracers of Venus' middle and upper atmosphere global wind system due to their variable peak brightness and horizontal distributions. A statistical map has been created utilizing O[SUB]2[/SUB] IR nightglow VEX observations, and a statistical map for NO UV is being developed. A nightside warm layer near 100 km has been observed by VEX and ground-based observations. The National Center for Atmospheric Research (NCAR) Venus Thermospheric General Circulation Model (VTGCM) has been updated and revised in order to address these key VEX observations and to provide diagnostic interpretation. The VTGCM is first used to capture the statistically averaged mean state of these three key observations. This correspondence implies a weak retrograde superrotating zonal flow (RSZ) from ˜80 km to 110 km and above 110 km the emergence of modest RSZ winds approaching 60 m s[SUP]-1[/SUP] above ˜130 km. Subsequently, VTGCM sensitivity tests are performed using two tuneable parameters (the nightside eddy diffusion coefficient and the wave drag term) to examine corresponding variability within the VTGCM. These tests identified a possible mechanism for the observed noncorrelation of the O[SUB]2[/SUB] and NO emissions. The dynamical explanation requires the nightglow layers to be at least ˜15 km apart and the retrograde zonal wind to increase dramatically over 110 to 130 km. [less ▲]

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See detailUV-IR comparison: Jupiter aurora
Gérard, Jean-Claude ULg; Grodent, Denis ULg

Conference (2011, August)

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See detailThe Ultraviolet Spectrograph (UVS) on Juno
Gladstone, G. R.; Persyn, S.; Eterno, J. et al

Poster (2011, July 11)

Detailed reference viewed: 32 (5 ULg)
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)

Detailed reference viewed: 22 (12 ULg)
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)

Detailed reference viewed: 22 (11 ULg)
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 detailAurora : Global features
Gérard, Jean-Claude ULg

Conference (2011, July)

Detailed reference viewed: 5 (1 ULg)
See detailOxygen Nightglow Investigation in the Visible Spectral Range, Using VIRTIS/Venus Express Data
Migliorini, A.; Piccioni, G.; Drossart, P. et al

Conference (2011, March 01)

Oxygen emissions in the visible spectral range, detected with VIRTIS on board Venus Express, in the upper atmosphere of Venus.

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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 detailA layer of ozone detected in the nightside upper atmosphere of Venus
Montmessin, Franck; Bertaux, J.-L.; Lefèvre, F. et al

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

Detailed reference viewed: 8 (3 ULg)