References of "Gladstone, G. R."
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See detailA new FUV auroral feature on Jupiter
Grodent, Denis ULiege; Gladstone, G. R.; Gérard, Jean-Claude ULiege et al

Conference (2003, April 01)

In December 2000, a series of HST/STIS FUV images of Jupiter's north auroral region displayed bright transient spots located near local midnight. In the images taken at CML Ë 220[SUP]o[/SUP] the spots ... [more ▼]

In December 2000, a series of HST/STIS FUV images of Jupiter's north auroral region displayed bright transient spots located near local midnight. In the images taken at CML Ë 220[SUP]o[/SUP] the spots (one or two) appear near the limb, poleward and equatorward of the main auroral oval, at latitude Ë 73[SUP]o[/SUP] and λ[SUB]III[/SUB] longitude Ë 145[SUP]o[/SUP]. The dimensions of each spot are very small, about 1[SUP]o[/SUP] in latitude and 5[SUP]o[/SUP] in longitude, which is about the size of the footprint of the Io satellite. However, the analysis of the position of the Galilean satellites and of known small-bodies (comets, asteroids) shows that these spots are not magnetically associated with any of these objects. The emitted power of the spots is variable and can reach several GW (more than the power emitted at the Io footprint). The lightcurves derived from multiple images are consistent with spots disappearing behind the planetary limb as the planet rotates. In addition, one short time-tagged image undoubtedly shows a bright double--spot feature pulsating with a period of 300 s. According to the VIP4 magnetic model, the auroral spots map along field lines down to the jovian magnetosphere in a small region roughly located near midnight at distances larger than 60~R_J. At these distances, a 1[SUP]o[/SUP] by 5[SUP]o[/SUP] auroral spot subtends an equatorial region smaller than 10~R_J by 10~R_J . Consequently, the auroral spots cannot be directly associated with large scale process involving the whole magnetotail but rather with localized events. [less ▲]

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See detailPreliminary Results from Recent Simultaneous Chandra/HST Observations of Jupiter Auroral Zones
Elsner, R. F.; Gladstone, G. R.; Waite, J. H. et al

Poster (2003)

Jupiter was observed by the Chandra X-ray Observatory in late February, 2003, for 144 ks, using both the ACIS-S and HRC-I imaging x-ray cameras. Five orbits of HST STIS observations of the planet's ... [more ▼]

Jupiter was observed by the Chandra X-ray Observatory in late February, 2003, for 144 ks, using both the ACIS-S and HRC-I imaging x-ray cameras. Five orbits of HST STIS observations of the planet's northern auroral zone were obtained during the ACIS-S observations. These data are providing a wealth of information about Jupiter's auroral activity, including the first x-ray spectra from the x-ray hot spots inside the auroral ovals. We will also discuss time variability in the auroral x-ray emission and a possible phase relation between the emission from the northern and southern x-ray aurora. [less ▲]

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See detailThe HST Campaign on Jupiter's Aurora during the Cassini Flyby
Clarke, J. T.; Grodent, Denis ULiege; Waite, J. H. et al

Conference (2002, July 29)

Detailed reference viewed: 13 (4 ULiège)
See detailThe HST Campaign on Jupiter's Aurora during the Cassini Flyby
Clarke, J. T.; Grodent, Denis ULiege; Gérard, Jean-Claude ULiege et al

Conference (2002, June 17)

Detailed reference viewed: 18 (0 ULiège)
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See detailIMAGE and FAST observations of substorm recovery phase aurora
Mende, Stephen B; Frey, Harald U; Carlson, Charles W et al

in Geophysical Research Letters (2002), 29

Images from the IMAGE Wide-band Imaging Camera (WIC) and Spectrographic Imager (SI) channel SI12, were compared to in situ data taken by FAST. The IMAGE data segment began during the expansive phase of a ... [more ▼]

Images from the IMAGE Wide-band Imaging Camera (WIC) and Spectrographic Imager (SI) channel SI12, were compared to in situ data taken by FAST. The IMAGE data segment began during the expansive phase of a substorm and a double oval configuration evolved, consisting of a set of discrete poleward auroral forms and a separate more diffuse oval. The FAST data showed that a narrow (~1.5° latitude) region of downward currents separated the two ovals. The SI-12 optical observations showed a single oval of precipitating protons located on the equatorward side within the diffuse aurora. In agreement with IMAGE, the highest intensity proton flux measured by FAST was concentrated on the equatorward region although low flux protons were present throughout the entire double oval. In the lower latitude diffuse oval occasional structured auroras were embedded. These structured auroras were mostly created by inverted V type electrons but there were narrow regions in which intense beams of accelerated electrons were seen whose energy/pitch angle distribution and accompanying electric field data were consistent with Alfven wave acceleration. The poleward oval consisted of an intense inverted V precipitation event poleward of which a weak region of Alfven wave accelerated electrons was located. From the images it appears that the Alfven wave accelerated electron event in the diffuse auroral regions and the poleward features were part of short lived or rapidly moving auroral forms. [less ▲]

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See detailChandra X-ray Observations of the Jovian System
Elsner, R. F.; Waite, J. H.; Crary, F. et al

Conference (2002)

High-spatial resolution Chandra x-ray obsrvations have demonstrated that most of Jupiter's northern auroral x-rays come from a hot spot located significantly poleward of the latitudes connected to the ... [more ▼]

High-spatial resolution Chandra x-ray obsrvations have demonstrated that most of Jupiter's northern auroral x-rays come from a hot spot located significantly poleward of the latitudes connected to the inner magnetosphere. This hot spot appears fixed in magnetic latitude and longitude and coincides with a region exhibiting anomalous ultraviolet and infrared emissions. The hot spot also exhibited approximately 45 minute quasi-periodic oscillations, a period similar to those reported for high-latitude radio and energetic electron bursts observed by near-Jupiter spacecraft. These results invalidate the idea that jovian auroral x-ray emissions are mainly excited by steady precipitation of energetic heavy ions from the inner magnetosphere. Instead, the x-rays appear to result from currently unexplained processes in the outer magnetosphere that produce highly localized and highly variable emissions over an extremely wide range of wavelengths. The Chandra observations also revealed for the first time x-ray emission (about 0.1 GW) from the Io Plasma Torus, as well as very faint x-ray emission (about 1-2 MW) from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is almost certainly due to Kalpha emission of surface atoms (and possibly impact atoms) excited by the impact of highly energetic protons, oxygen, and sulfur atoms and ions from the Torus. The Torus emission is less well understood at present, although bremsstrahlung from the non-thermal tail of the electron distribution may provide a significant fraction. In any case, further observations, already accepted and in the process of being planned, with Chandra, some with the moderate energy resolution of the CCD camera, together with simultaneous Hubble Space Telescope observations and hopefully ground-based IRTF observations should soon provide greater insight into these various processes. [less ▲]

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See detailSoft X-ray emissions from planets, moons, and comets
Bhardwaj, A.; Gladstone, G. R.; Elsner, R. F. et al

Conference (2002)

A wide variety of solar system bodies are now known to radiate in the soft X-ray energy (<5 keV) regime. These include planets (Earth, Jupiter, Venus, Saturn, Mars): bodies having thick atmospheres, with ... [more ▼]

A wide variety of solar system bodies are now known to radiate in the soft X-ray energy (<5 keV) regime. These include planets (Earth, Jupiter, Venus, Saturn, Mars): bodies having thick atmospheres, with or without intrinsic magnetic field; planetary satellites (Moon, Io, Europa, Ganymede): bodies with thin or no atmospheres; and comets and Io plasma torus: bodies having extended tenuous atmospheres. Several different mechanisms have been proposed to explain the generation of soft X-rays from these objects, whereas in the hard X-ray energy range (>10 keV) X-rays mainly result from the electron bremsstrahlung process. In this paper we present a brief review of the X-ray observations on each of the planetary bodies and discuss their characteristics and proposed source mechanisms. [less ▲]

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See detailObservations of the Jovian System with the Chandra X-ray Observatory
Elsner, R. F.; Gladstone, G. R.; Lewis, W. S. et al

Conference (2002)

Sensitive, very high spatial-resolution x-ray observations with the Chandra X-ray Observatory have revealed that Jupiter's northern x-ray aurora originates at a spot fixed in a coordinate system rotating ... [more ▼]

Sensitive, very high spatial-resolution x-ray observations with the Chandra X-ray Observatory have revealed that Jupiter's northern x-ray aurora originates at a spot fixed in a coordinate system rotating with the planet at latitude (60-70 deg north) and longitude (160-180 deg System III). The northern auroral x-ray emission varies with a period about 45 minute and has an average power of about 1 GW. Jupiter's disk also emits x-rays with a power of about 2 GW, perhaps resulting from reprocessing of solar x-rays in its atmosphere. These observations reveal for the first time x-ray emission from the Io Plasma Torus, with a power of about 0.1 GW. Finally, we report the discovery of very faint (about 1-2 MW) soft x-ray emission from the Galilean satellites Io, Europa, and probably Ganymede. [less ▲]

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See detailJupiter's Thermospheric General Circulation Model (JTGCM): Equatorial thermal structure in comparison with Galileo probe measurements
Majeed, T.; Bougher, S. W.; Waite, J. H. et al

Poster (2001, June 25)

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See detailChandra HRC Observations of X-rays from the Jupiter System
Gladstone, G. R.; Waite, J. H.; Grodent, Denis ULiege et al

Conference (2001, June 25)

Detailed reference viewed: 8 (0 ULiège)
See detailOverview of Ionospheric-Magnetospheric Coupling at Jupiter: The Jovian Aurora
Waite, J. H.; Grodent, Denis ULiege; Crary, F. et al

Conference (2001, June 25)

Detailed reference viewed: 7 (0 ULiège)
See detailDetermination of electron and proton auroral energy inputs from FUV-IMAGE
Gérard, Jean-Claude ULiege; Hubert, Benoît ULiege; Meurant, M. et al

Conference (2001, May 01)

The FUV experiment onboard the IMAGE spacecraft offers the unique possibility to obtain simultaneous snapshots of the global north aurora every 2 minutes in three different spectral channels. The WIC ... [more ▼]

The FUV experiment onboard the IMAGE spacecraft offers the unique possibility to obtain simultaneous snapshots of the global north aurora every 2 minutes in three different spectral channels. The WIC camera has a broadband channel covering the 135-190 nm interval including the N[SUB]2[/SUB] LBH bands, part of which may be absorbed by O[SUB]2[/SUB]. The SI13 channel is centered on the OI 135.6 nm line which is optically thin and includes a ~ 40% LBH contribution. Finally, the SI12 camera images the Doppler-shifted Ly-α emission excited by the proton aurora. This set of instrumentation is combined with auroral models to determine the electron and the proton energy fluxes from the magnetosphere. Examples will be presented and compared with the values deduced from the NOAA satellites. Simultaneous in-situ measurements of the particle characteristic energy have been combined with the data extracted from the FUV images to validate the models and derive empirical relationships between the particle flux measured by the detectors and the brightness observed by FUV-IMAGE at the footprint of the same magnetic field line. Finally, we will assess the ability to deduce the characteristic energy of the auroral particles from the ratio of co-registered images in the WIC and SI13 cameras. This method is based on the difference of vertical distribution of the LBH and the OI 135.6 nm emissions. It offers the potential to globally remotely sense not only the energy flux from the magnetosphere but also the main features of the electron characteristic energy. [less ▲]

Detailed reference viewed: 20 (5 ULiège)
See detailThe Forty-Minute Period of Jupiter's X-ray Polar Emission
Grodent, Denis ULiege; Crary, F. J.; Gladstone, G. R. et al

Poster (2001)

The observation of Jupiter's x-ray auroral emission during the Cassini Jupiter flyby has brought information of prime interest. The High Resolution Camera onboard the Chandra satellite has a pixel size of ... [more ▼]

The observation of Jupiter's x-ray auroral emission during the Cassini Jupiter flyby has brought information of prime interest. The High Resolution Camera onboard the Chandra satellite has a pixel size of ~.13 arcsec, which makes it possible to discriminate emission features inside the Jovian polar regions. A ten-hour (one full Jovian rotation) light curve of the northern polar cap region (i.e. a region enclosed by System-3 longitude 160-180° and latitude 60-70°) clearly shows a forty-minute oscillation. This oscillation is shown to be independent of the viewing geometry. Such an oscillation is more speculative for the southern polar cap for which the S/N is much lower than in the North. However, if statistically significant, the fluctuation observed in the southern cap may be in close anticorrelation with the northern cap light curve. This would suggest a bouncing motion of the impinging particles, presumably sulfur and oxygen ions, between the polar cap mirror points. Comparison with HST-STIS far ultraviolet (FUV) observations taken during this Jovian rotation allows us to correlate the x-ray emission with a persistent FUV feature mapping to ~30 RJ in the dayside magnetosphere. This feature shows significant local time variations. However, the sampling of the STIS observations does not permit us to highlight a forty-minute oscillation in the corresponding ultraviolet light curve. Previous STIS spectra favor a high FUV color ratio for the polar cap emission, which is consistent with precipitation of high energy sulfur and oxygen ions. [less ▲]

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See detailObservations of the Jovian low latitude FUV emission with HST/STIS
Gustin, Jacques ULiege; Grodent, Denis ULiege; Dols, V. et al

Poster (1999, October 10)

Detailed reference viewed: 7 (1 ULiège)
See detailFar ultraviolet Observations of Jovian low latitude regions with HST/STIS
Gustin, Jacques ULiege; Grodent, Denis ULiege; Gérard, Jean-Claude ULiege et al

in Bulletin of the American Astronomical Society (1999, September 01), 30(11),

Far ultraviolet observations of the Jovian disk were made at low and mid-latitudes with FUV MAMA/STIS on board HST in January 1999 both in the imaging and spectroscopic modes. An image was obtained with ... [more ▼]

Far ultraviolet observations of the Jovian disk were made at low and mid-latitudes with FUV MAMA/STIS on board HST in January 1999 both in the imaging and spectroscopic modes. An image was obtained with the Lyalpha filter in the hydrogen bulge region for comparison with the expected Lyman-alpha brightness distribution for Ly-alpha resonance scattering. Other images in the 1200-1700 { Angstroms} region show band structures parallel to the equator with fading contrast toward the center and the limb. Spectroscopic observations were made in the 1200-1700 { Angstroms} (G140L) and 1245-1298 { Angstroms} (G140M) regions at ~ 5 { Angstroms} resolution to map the H_2 airglow and the UV absorbents along the STIS slit. Preliminary results indicate that a C_2H_2 absorption signature is clearly observed in the solar ultraviolet reflected spectrum. The ethylene absorption may be mapped to derive variations of the acetylene abundance. The H_2 FUV airglow shows both the fluorescence and the electron impact components. Its spatial variation is described and compared with the expected airglow distribution. We acknowledge funding by NASA and by the PRODEX program of the European space agency. [less ▲]

Detailed reference viewed: 43 (17 ULiège)
See detailHST/STIS images of UV auroral footprints from Io, Europa, and Ganymede.
Clarke, J. T.; Ajello, J.; Ballester, G. E. et al

in Bulletin of the American Astronomical Society (1999)

Ultraviolet images of Jupiter's aurora have been obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) since September 1997 with much higher sensitivity than ... [more ▼]

Ultraviolet images of Jupiter's aurora have been obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) since September 1997 with much higher sensitivity than earlier cameras. Higher sensitivity permits shorter exposures, freezing Jupiter's rotation and providing the highest angular resolution obtained to date. This combination of sensitivity and resolution has revealed new emissions from the magnetic footprints of Io, Europa, and Ganymede, which will be reported and discussed. Io's auroral footprint, while well studied with earlier cameras, appears highly extended at a low brightness in the wake or plasma flow direction. Ganymede's auroral footprint emission is now well established from the repeated appearance of this feature under the magnetic field trace of Ganymede, and there is initial evidence for auroral emission at Europa's magnetic footprint. Ganymede's auroral footprint appears consistently equatorward of the main auroral oval, which clearly constrains the main oval auroral currents to originate from beyond about 20 R_J. The observation that the main oval emissions are observed to corotate with Jupiter's magnetic field further constrains the origin of these currents to be within about 30 R_J, so that the source region for the main oval auroral is now fairly well constrained to a region in Jupiter's middle magnetosphere and within the current sheet. This work was supported by NASA under grant GO-7308.01-96A to the University of Michigan. [less ▲]

Detailed reference viewed: 48 (9 ULiège)
See detailThe Jovian Aurora: Implications of Multiwavelength Auroral Spectra for Auroral Particle Identity and Auroral Microphysics
Waite, J. H.; Gladstone, G. R.; Bolton, S. J. et al

in Bulletin of the American Astronomical Society (1998, September 01)

Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on Jupiter's upper ... [more ▼]

Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on Jupiter's upper atmosphere. Both energetic heavy ions and electrons energized in the outer magnetosphere contribute to the auroral excitation, as indicated by the combination of x-ray and ultraviolet observations. Imaging with the HST in the ultraviolet and with the IRTF at infrared wavelengths reveals several distinct regions of interaction: 1) a dusk sector where turbulent auroral patterns extend well into the polar cap; 2) a morning sector generally characterized by a single spatially confined auroral arc originating in the outer magnetosphere of Jupiter; 3) diffuse emissions associated with the Io plasma torus; and 4) a distinct region associated with the Io Flux Tube footprint. Ultraviolet spectroscopy has provided important information about the thermal structure of the upper atmosphere and altitude distribution of the auroral particle energy deposition, while Lyman alpha line profiles offer clues to the nature of thermospheric dynamical effects. Galileo observations at visible wavelengths on the nightside have provided a new view of the jovian aurora with unprecedented spatial information. Infrared observations have added much to the understanding of thermal structure and morphology and may hold the key to understanding the role of Joule heating. Radio observations imply that energetic particle precipitation extends to low latitudes, a result that has been corroborated at x-ray wavelengths. Multispectral observations of jovian auroral emissions will be discussed within a theoretical/modeling framework that serves to provide some insight into magnetosphere-ionosphere coupling and its effect on the upper atmosphere. Particular emphasis will be placed on the use of auroral spectra to identify incident energetic particles and their energy spectra as a means of elucidating the microphysics of auroral processes. [less ▲]

Detailed reference viewed: 27 (1 ULiège)
See detailJovian Auroral Lyalpha Self-Reversals: A Window on Jupiter's Auroral Electrojet?
Gladstone, G. R.; Waite, J H, Jr; Gérard, Jean-Claude ULiege

in Bulletin of the American Astronomical Society (1998, September 01)

High-resolution GHRS profiles of Lyalpha lines emitted from Jupiter's auroral regions were presented by Prang{e} et al. (Astrophys. J., 484, L169--L173, 1997). Their data show asymmetric self-reversed ... [more ▼]

High-resolution GHRS profiles of Lyalpha lines emitted from Jupiter's auroral regions were presented by Prang{e} et al. (Astrophys. J., 484, L169--L173, 1997). Their data show asymmetric self-reversed line profiles, with the blue or red peak brighter depending on the target location in Jupiter's northern auroral region. The measured asymmetries are equivalent to Doppler velocities towards and away from the observer of several km/s. As suggested by Sommeria et al. (Icarus, 119, 2--24, 1995), electrojet velocities of ~ 10--20 km/s may be present at Jupiter. Here we investigate the possibility that the observed wavelength shifts of the auroral Lyalpha line are a result of multiple scattering by H atoms carried along in Jupiter's auroral electrojet. If this explanation is found to be viable, then HST/STIS mapping of the velocity shifts in the Lyalpha line may represent (as with ground-based high-resolution observations of jovian auroral H_3(+) emission lines) a means for determining the dynamics of Jupiter's upper atmosphere and ionosphere. [less ▲]

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See detailHST-STIS Observations of Jupiter's Aurora
Clarke, J. T.; Ajello, J.; Ballester, G. E. et al

in Bulletin of the American Astronomical Society (1998, September 01)

HST observations of the UV emissions from Jupiter's aurora have been obtained with the new Space Telescope Imaging Spectrograph (STIS) since July 1997. UV images of the aurora are now possible with an ... [more ▼]

HST observations of the UV emissions from Jupiter's aurora have been obtained with the new Space Telescope Imaging Spectrograph (STIS) since July 1997. UV images of the aurora are now possible with an order of magnitude higher sensitivity than possible with earlier cameras, and improved angular resolution from shorter exposures. Images have been obtained at 4 epochs since Sept. 1997, and reveal several new features of the auroral emission pattern. These include i) faint auroral emissions extending roughly 60 deg. in the wake or plasma flow direction beyond Io's magnetic footprint, ii) systematic motions of the main auroral oval both toward the pole and toward the equator at different local times and longitudes, and iii) clear identification of an auroral emission feature with Ganymede's magnetic footprint, from the relative motion of the feature remaining underneath Ganymede in a time series of images. Preliminary interpretations of these features will be presented. Spectra have also been obtained of auroral emission features including the northern and southern main ovals, the diffuse emission poleward of the main oval, and the northern and southern Io footprints. These spectra will be presented with estimates of the overlying hydrocarbon columns, the energy of the exciting electrons, the rotational temperature of the emitting hydrogen, and the overlying column of atomic hydrogen. This work was supported by NASA under grants GO-6743.01-95A and GO-7308.01-96A to the University of Michigan. [less ▲]

Detailed reference viewed: 18 (1 ULiège)
See detailFUV spectroscopy of the H_2 emission in the Jovian aurora: model update and results
Gérard, Jean-Claude ULiege; Dols, V.; Colignon, David ULiege et al

in Bulletin of the American Astronomical Society (1998, September 01)

The Jovian aurora exhibits bright emissions mainly due the bright Lyman-alpha line and to radiation from excited singlet states to the ground electronic state extending from 800 to 1600 Angstroms. Above ... [more ▼]

The Jovian aurora exhibits bright emissions mainly due the bright Lyman-alpha line and to radiation from excited singlet states to the ground electronic state extending from 800 to 1600 Angstroms. Above 1200 Angstroms, the molecular spectrum is dominated by the Lyman (B-X) bands and continuum and the Werner (C-X) bands. These transitions have been observed with the Goddard High Resolution Spectrometer (GHRS) and the Space Telescope Imaging Spectrometer (STIS) at various spectral and spatial resolutions. To analyze these spectra, a model synthetic auroral spectrum has been constructed and applied to the analysis of the ro-vibrational temperature of H_2 and a search for non-H_2 emission features. It has been recently updated to include the latest singlet state excitation and cascading cross sections, self-absorption in optically thick lines and to account for the energy distribution of the secondary electrons which cause additional excitation. We illustrate these effects in a few study cases and apply the model to high resolution (0.5 Angstroms) GHRS spectra and low resolution STIS spectra of the entire H_2 spectrum at wavelengths longer than Lyman-alpha. We determine the methane column overlying the auroral emission peak and find that a better fit is obtained with additional absorption by acetylene. [less ▲]

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