References of "Gustin, Jacques"
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See detailCassini-UVIS observation of dayglow FUV emissions of carbon in the thermosphere of Venus
Hubert, Benoît ULg; Gérard, Jean-Claude ULg; Gustin, Jacques ULg et al

in Icarus (2012), 220

We analyze FUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus. The intensities of the ultraviolet multiplets of carbon at 126.1 ... [more ▼]

We analyze FUV spatially-resolved dayglow spectra obtained at 0.37 nm resolution by the UVIS instrument during the Cassini flyby of Venus. The intensities of the ultraviolet multiplets of carbon at 126.1, 156.1 and 165.7 nm are determined using a least squares fit technique applied to all dayglow spectra recorded by UVIS along the Cassini track. These intensities are compared with the results of a full radiative transfer model of these emissions, that includes the known photochemical sources of photons and resonant scattering of sunlight. The carbon density profile of the Venus thermosphere has never been directly measured and is taken from a model. We find a serious disagreement between these observations and modeling that can be accounted for by applying a scaling factor to the carbon column. This needed scaling factor is found to increase monotonically with solar zenith angle, suggesting a possible photochemical origin to the disagreement, possibly involving the photochemistry of molecular oxygen to which the carbon density is highly sensitive. [less ▲]

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See detailSimultaneous Cassini VIMS and UVIS observations of Saturn's southern aurora
Melin, H.; Stallard, T.; Miller, S. et al

Conference (2012)

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See detailSaturn night-­‐side variability
Pryor, W.; Gustin, Jacques ULg; Holsclaw, G. et al

Conference (2012)

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See detailMulti‐spectral simultaneous observations of Saturn's aurorae in Jan. 2009
Lamy, L.; Prange, R.; Gustin, Jacques ULg et al

Conference (2012)

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See detailUranus Pathfinder: exploring the origins and evolution of Ice Giant planets
Arridge, Christopher S.; Agnor, Craig B.; Andre, Nicolas et al

in Experimental Astronomy (2012)

The "Ice Giants" Uranus and Neptune are a different class of planet compared to Jupiter and Saturn. Studying these objects is important for furthering our understanding of the formation and evolution of ... [more ▼]

The "Ice Giants" Uranus and Neptune are a different class of planet compared to Jupiter and Saturn. Studying these objects is important for furthering our understanding of the formation and evolution of the planets, and unravelling the fundamental physical and chemical processes in the Solar System. The importance of filling these gaps in our knowledge of the Solar System is particularly acute when trying to apply our understanding to the numerous planetary systems that have been discovered around other stars. The Uranus Pathfinder (UP) mission thus represents the quintessential aspects of the objectives of the European planetary community as expressed in ESA's Cosmic Vision 2015-2025. UP was proposed to the European Space Agency's M3 call for medium-class missions in 2010 and proposed to be the first orbiter of an Ice Giant planet. As the most accessible Ice Giant within the M-class mission envelope Uranus was identified as the mission target. Although not selected for this call the UP mission concept provides a baseline framework for the exploration of Uranus with existing low-cost platforms and underlines the need to develop power sources suitable for the outer Solar System. The UP science case is based around exploring the origins, evolution, and processes at work in Ice Giant planetary systems. Three broad themes were identified: (1) Uranus as an Ice Giant, (2) An Ice Giant planetary system, and (3) An asymmetric magnetosphere. Due to the long interplanetary transfer from Earth to Uranus a significant cruise-phase science theme was also developed. The UP mission concept calls for the use of a Mars Express/Rosetta-type platform to launch on a Soyuz-Fregat in 2021 and entering into an eccentric polar orbit around Uranus in the 2036-2037 timeframe. The science payload has a strong heritage in Europe and beyond and requires no significant technology developments. [less ▲]

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See detailAuroral counterpart of magnetic field dipolarizations in Saturn's tail
Jackman, C. M.; Achilleos, N.; Bunce, E. J. et al

in American Geophysical Union, Fall Meeting 2011, abstract #SM14A-07 (2011, December 01)

Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations ... [more ▼]

Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations can be initially identified from the magnetometer data by looking for a southward turning of the magnetic field, indicating the transition from a radially stretched configuration to a more dipolar field topology. The highly stretched geometry of the kronian magnetotail lobes gives rise to a tail current which flows eastward (dusk to dawn) in the near equatorial plane across the centre of the tail. During reconnection and associated dipolarization of the field, the inner edge of this tail current can be diverted through the ionosphere, in a situation analogous to the substorm current wedge picture at Earth [McPherron et al. 1973]. We present a picture of the current circuit arising from this tail reconfiguration, and outline the equations which govern the field-current relationship. We show a number of examples of dipolarizations as identified in the Cassini magnetometer data and use this formalism to calculate limits for the ionospheric current density that would arise for these examples. In addition to the magnetometer data, we also present data from the Cassini VIMS and UVIS instruments which have observed small 'spots' of auroral emission lying near the main oval - features thought to be associated with dipolarizations in the tail. We compare the auroral intensities as predicted from our calculation with the observed spot sizes and intensities. [less ▲]

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See detailSaturn's aurora as viewed by Cassini VIMS
Melin, H.; Stallard, T.; Badman, S. V. et al

Conference (2011, December 01)

The stunning views of the kronian aurora captured by the Visual and Infrared Imaging Spectrograph (VIMS) onboard the Cassini spacecraft continues to provide crucial observations of the fervent interaction ... [more ▼]

The stunning views of the kronian aurora captured by the Visual and Infrared Imaging Spectrograph (VIMS) onboard the Cassini spacecraft continues to provide crucial observations of the fervent interaction between the upper atmosphere and the magnetosphere of Saturn. Here, we present recent findings of VIMS auroral research, which includes both statistical studies and case studies of auroral events and morphology. In addition to stand-alone observations, there is a small subset of VIMS observations during which UVIS was also acquiring data. These observations enable the comparison between observations of H, H2 in the ultraviolet and H3+ in the infrared that are both spatially overlapping and temporally simultaneous. Whilst emission tends to coincide for these three species on the main oval, there are significant differences both pole-ward and equator-ward, such that observations of H and H2 is generally a poor proxy for emissions of H3+. VIMS is sensitive to infrared thermal emission from the H3+ molecule, which is formed very efficiently via the ionisation of H2. Therefore, the morphology of H3+ emission becomes a tracer of energy injected into the upper atmosphere - the most striking of which is auroral particle precipitation. [less ▲]

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See detailCassini UVIS Observations of Titan Ultraviolet Airglow Spectra with Laboratory Modeling from Electron- and Proton-Excited N2 Emission Studies
Ajello, J. M.; West, R. A.; Malone, C. P. et al

Conference (2011, December 01)

Joseph M. Ajello, Robert A. West, Rao S. Mangina Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 Charles P. Malone Jet Propulsion Laboratory, California Institute of ... [more ▼]

Joseph M. Ajello, Robert A. West, Rao S. Mangina Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 Charles P. Malone Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 & Department of Physics, California State University, Fullerton, CA 92834 Michael H. Stevens Space Science Division, Naval Research Laboratory, Washington, DC 20375 Jacques Gustin Laboratoire de Physique Atmosphérique et Planétaire, Université de Liège, Liège, Belgium A. Ian F. Stewart, Larry W. Esposito, William E. McClintock, Gregory M. Holsclaw Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 E. Todd Bradley Department of Physics, University of Central Florida, Orlando, FL 32816 The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed photon emissions of Titan's day and night limb-airglow and disk-airglow on multiple occasions, including three eclipse observations from 2009 through 2010. The 77 airglow observations analyzed in this paper show EUV (600-1150 Å) and FUV (1150-1900 Å) atomic multiplet lines and band emissions (lifetimes less than ~100 μs), including the Lyman-Birge-Hopfield (LBH) band system, arising from photoelectron induced fluorescence and solar photo-fragmentation of molecular nitrogen (N2). The altitude of peak UV emission on the limb of Titan during daylight occurred inside the thermosphere/ionosphere (near 1000 km altitude). However, at night on the limb, the same emission features, but much weaker in intensity, arise in the lower atmosphere below 1000 km (lower thermosphere, mesosphere, haze layer) extending downwards to near the surface at ~300 km, possibly resulting from proton- and/or heavier ion-induced emissions as well as secondary-electron-induced emissions. The eclipse observations are unique. UV emissions were observed during only one of the three eclipse events, and no Vegard-Kaplan (VK) or LBH emissions were seen. Through regression analysis using laboratory spectra, we have analyzed the intensity and identified each spectral feature from the limb or disk emission spectrum. The strongest dipole-allowed transitions of N2 occur in the EUV. The electronic transitions proceed from the X 1Σg+ ground-state to about seven closely spaced (~12-15 eV) Rydberg-valence (RV) states, which are the source of the molecular emissions in the EUV observed by spacecraft and have recently been studied in our laboratory at medium-to-high spectral resolution (delta-λ = 0.1 Å FWHM). Three of these RV states (b 1Πu, b' 1Σu+, and c4' 1Σu+) are highly-perturbed, weakly-to-strongly predissociated, and have significant emission cross sections, which will be summarized in this paper. We will also discuss our recently published proton and electron impact emission cross sections for the LBH (a 1Πg - X 1Σg+) band system of N2, and their significance to the modeling of the day and night FUV spectra of the atmospheres of Earth and Titan. [less ▲]

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See detailSimultaneous Cassini VIMS and UVIS observations of Saturn's southern aurora
Melin, H.; Stallard, T.; Miller, S. et al

in EPSC-DPS Joint Meeting 2011 (2011, October 01)

Here, temporally simultaneous and spatially overlapping Cassini VIMS and UVIS observations of Saturn's southern aurora are presented. The pointing is fixed at a constant local time of 04:55, covering ... [more ▼]

Here, temporally simultaneous and spatially overlapping Cassini VIMS and UVIS observations of Saturn's southern aurora are presented. The pointing is fixed at a constant local time of 04:55, covering latitudes between 64°S and 82°S and longitudes between 127° and 186°. The spatial resolution is high, with 1 mrad covering ˜300 km, such that only a small part of the pre-dawn aurora is observed. Ultraviolet auroral H and H2 emissions from UVIS are compared to infrared H+3 emission from VIMS. The auroral emission is structured into three arcs - H, H2 and H+3 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 H2 and H+3 . These observations indicate that, for the main auroral oval, the UV emission is a good proxy for the infrared H+3 morphology (and vice versa), but for emission either poleward or equatorward this is no longer true. Hence, given the highly dynamic nature of the aurora of Saturn, simultaneous UV/IR observations are crucial for completing the picture of how the atmosphere interacts with the magnetosphere. [less ▲]

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See detailMeasurements of the helium 584 Å airglow during the Cassini flyby of Venus
Gérard, Jean-Claude ULg; Gustin, Jacques ULg; Hubert, Benoît ULg et al

in Planetary and Space Science (2011), 59

The helium resonance line at 584 Å has been observed with the UltraViolet Imaging Spectrograph (UVIS) Extreme Ultraviolet channel during the flyby of Venus by Cassini at a period of high solar activity ... [more ▼]

The helium resonance line at 584 Å has been observed with the UltraViolet Imaging Spectrograph (UVIS) Extreme Ultraviolet channel during the flyby of Venus by Cassini at a period of high solar activity. The brightness was measured along the disk from the morning terminator up to the bright limb near local noon. The mean disk intensity was ˜320 R, reaching ˜700 R at the bright limb. These values are slightly higher than those determined from previous observations. The sensitivity of the 584 Å intensity to the helium abundance is analyzed using recent cross-sections and solar irradiance measurements at 584 Å. The intensity distribution along the UVIS footprint on the disk is best reproduced using the EUVAC solar flux model and the helium density distribution from the VTS3 empirical model. It corresponds to a helium density of 8×10[SUP]6[/SUP] cm[SUP]-3[/SUP] at the level of where the CO[SUB]2[/SUB] is 2×10[SUP]10[/SUP] cm[SUP]-3[/SUP]. [less ▲]

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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 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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