References of "Gustin, Jacques"
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See detailCassini UVIS Observations of Saturn's Auroras
Pryor, W. J.; Ajello, J. M.; Gustin, Jacques ULg et al

Conference (2007, June 25)

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See detailSaturn's Auroras and Polar Atmosphere from Cassini UVIS
Pryor, W. R.; West, R.; Larsen, K. et al

Conference (2006, December 01)

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed two years of study of Saturn's atmosphere and auroras. Two long slit spectral channels are used to obtain EUV data from 56.3-118.2 nm and ... [more ▼]

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed two years of study of Saturn's atmosphere and auroras. Two long slit spectral channels are used to obtain EUV data from 56.3-118.2 nm and FUV data from 111.5-191.3 nm. 64 spatial pixels along each slit are combined with slit motion to construct spectral images of Saturn, with sufficient spatial resolution to image Saturn's auroral oval when Cassini leaves Saturn's equatorial plane. We will present new images and time-series data from summer 2006. Detailed spectral models of molecular hydrogen auroral emissions that include hydrocarbon absorption and hydrogen self- absorption have now been compared to UVIS data. We are analyzing a UV spectral feature detected in an auroral oval image from 2005. The feature is an absorption feature concentrated inside the oval, at wavelengths dominated by reflected sunlight and acetylene absorption. The absorption feature appears as a broad absorption "scoop". One plausible molecule that has a similar absorption feature is benzene, which has a cross-section some 500 times larger than acetylene in this spectral region. Thus UVIS is sensitive to small quantities of benzene. Enhanced polar benzene has been previously observed at Jupiter and can be generated in coupled photochemical/auroral models. We will explore the uniqueness of this interpretation, and compare the inferred benzene abundances to results from complementary Cassini CIRS infrared observations. Additional out of the equatorial plane UVIS Saturn data planned for the coming months will improve the signal- to-noise ratio and spatial resolution on the auroral ovals and their interior. Coordinated observations with Cassini VIMS and Hubble Space Telescope are being scheduled for 2007. [less ▲]

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See detailCharacteristics of Jovian morning bright FUV aurora from Hubble Space Telescope/Space Telescope Imaging Spectrograph imaging and spectral observations
Gustin, Jacques ULg; Cowley, S. W. H.; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Space Physics (2006), 111(A9),

Observation of an exceptionally bright (peaking at similar to 1.8 MR) Jovian auroral morning arc was obtained with the Space Telescope Imaging Spectrograph (STIS) on 21 September 1999, both in the imaging ... [more ▼]

Observation of an exceptionally bright (peaking at similar to 1.8 MR) Jovian auroral morning arc was obtained with the Space Telescope Imaging Spectrograph (STIS) on 21 September 1999, both in the imaging and spectral modes. The images of the HST orbit are used to describe the variation of the position of the bright arc, while the time-tagged spectra are examined to derive the properties of the precipitating auroral electrons, such as their mean energy and the electron current density at the top of the atmosphere. The first and the last images of the HST orbit, separated by 37 min, show that the bright morning emission is situated on the reference oval, with a "leading" edge fixed in lambda(III) longitudes (i.e., rotating with the planet), and a "trailing" edge that extends into the nightside. The auroral arc is divided in two branches, as was also observed in some previous analyses. An isolated bright spot is also observed at lambda(III) similar to 184 degrees. Its brightness reaches 500 kR and it also approximately corotates with Jupiter. Four regions of the auroral morning arc captured by the STIS aperture were extracted from the spectral observation. The four associated low-resolution spectra (similar to 4.8 degrees) show very different characteristics. In particular, two spectra reveal unusually high color ratios (18.5 and 45.5), with corresponding mean electron energies of similar to 280 and similar to 460 keV, respectively. The current densities associated with three of the spectra lie in the range 0.09-0.2 mu A m(-2), consistent with previous estimates, while the fourth spectrum is characterized by a mean current density of 0.54 mu A m(-2), outside the range similar to 0.04-0.4 mu A m(-2) obtained in a previous study of G140L spectra of the Jovian main oval. Assuming that main oval aurorae are caused by field-aligned electric fields, the relationship between the energy flux and the current density derived from the spectra has been compared to the Knight's theory of field-aligned currents. Because of the very high acceleration potential derived from two of the extracted spectra, a relativistic treatment of the Knight theory was used. Assuming an electron temperature T-e = 2.5 keV, it is seen that the two regions corresponding to earlier local times (higher lambda(III) longitudes) reveal an electron source density lower than the values observed in the equatorial plane during the Voyager flybys. On the other hand, the equatorward region (lowest latitude) exhibits an electron source density in the upper range of usual values. Analysis of time-tag spectra reveals that the variations of the energy flux and the color ratios are large but continuous and generally covary. [less ▲]

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See detailIo footprint: Position, Multiplicity, Variability
Bonfond, Bertrand ULg; Gérard, Jean-Claude ULg; Grodent, Denis ULg et al

Conference (2006, July)

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See detailUltraviolet spectroscopy of giant planets's aurora with HST/STIS, FUSE and Cassini/UVIS
Gustin, Jacques ULg; Gérard, Jean-Claude ULg; Pryor, Wayne et al

Conference (2006, July)

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See detailEuropa's FUV auroral tail on Jupiter
Grodent, Denis ULg; Gérard, Jean-Claude ULg; Gustin, Jacques ULg et al

in Geophysical Research Letters (2006), 33(6),

Ultraviolet images of Jupiter's northern aurora obtained in 2005 confirm the existence of an electromagnetic interaction between Europa and the Jovian ionosphere. The auroral signature shows a two ... [more ▼]

Ultraviolet images of Jupiter's northern aurora obtained in 2005 confirm the existence of an electromagnetic interaction between Europa and the Jovian ionosphere. The auroral signature shows a two-component structure: a quasi-circular Europa spot, followed by a previously undetected faint tail emission trailing in the direction of corotation flow. The characteristic brightness for the auroral spot is similar to 14 +/- 1 kR above background, and approximately 7 +/- 1 kR for the tail. The spot's size is similar to 1100 km, magnetically mapping to an interaction region <= 15 Europa diameters. The auroral tail extends over similar to 5000 km, which maps along a region of at least 70 Europa diameters. The ultraviolet power emitted by both components varies from a fraction to several GW. The present study suggests auroral interaction at Europa similar to that at Io, but scaled-down by an order of magnitude, including a sub-corotating plasma plume in the geometrical wake of Europa. [less ▲]

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See detailCurrent thinking about Jupiter's magnetic anomaly
Grodent, Denis ULg; Gérard, Jean-Claude ULg; Gustin, Jacques ULg et al

Conference (2006)

Repeated imaging of Jupiter's aurora has shown that the northern main oval has a distorted 'kidney bean' shape in the general range of 90-150o System III longitude, which appears unchanged since 1994 ... [more ▼]

Repeated imaging of Jupiter's aurora has shown that the northern main oval has a distorted 'kidney bean' shape in the general range of 90-150o System III longitude, which appears unchanged since 1994. While it is more difficult to observe the conjugate regions in the southern aurora, no corresponding distortion appears in the south. Recent improved accuracy in locating the auroral footprint emission of Io has provided new information about the geometry of Jupiter's magnetic field in this and other areas. The persistent pattern of the main oval implies a disturbance of the local magnetic field, and the increased latitudinal separation of the locus of the Io footprint from the main oval implies a locally weaker field strength. The most recent images obtained with the Hubble Space Telescope Advance Camera for Surveys (ACS) allow us to complement previous observations with the location of the auroral footprints of Io, Europa, and Ganymede in the region of interest. Their footpaths vary in parallel and form a kink in the 90-150° S3 sector which strongly suggests the presence of a magnetic anomaly in this region. [less ▲]

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See detailObservations of Saturn's Atmosphere and Auroras by Cassini UVIS and VIMS
Pryor, W. R.; Baines, K.; West, R. et al

Conference (2005, December 01)

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed a year of study of Saturn's atmosphere and auroras. Two long slit spectral channels are used to obtain EUV data from 56.3-118.2 nm and FUV ... [more ▼]

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed a year of study of Saturn's atmosphere and auroras. Two long slit spectral channels are used to obtain EUV data from 56.3-118.2 nm and FUV data from 111.5-191.3 nm. 64 spatial pixels along each slit are combined with slit motion to build up spectral images of Saturn, with sufficient spatial resolution to reveal Saturn's auroral oval. Saturn images include evidence for rapid auroral variations and polar UV-dark regions mostly inside the auroral ovals. Absorption bands of acetylene are clearly seen in the reflected sunlight spectrum. The auroral emission spectrum is similar to that of Jupiter, showing H2 band emission and H Lyman-alpha emission. Saturn's auroral, dayglow, and nightglow spectra show significant differences. Saturn's aurora is observed to vary in brightness by at least a factor of four. The brightest auroral emissions seen so far occurred after 2004 day 207 19:30 when Cassini CAPS and MAG recorded passage of a solar wind shock. The enhanced auroral brightness persisted for days, and is seen at both poles of Saturn. Cassini RPWS observed enhanced auroral kilometric emissions during several auroral brightening events seen by UVIS. A campaign of Hubble Space Telescope UV imaging with ACS (Advanced Camera for Surveys) of Saturn's dayside southern auroral zone took place on 2005 February 17. Cassini UVIS and VIMS observed Saturn's nightside northern aurora during this period. The UVIS long slit was aligned with lines of latitude on Saturn, providing information about intensity and spectral variations along the auroral oval. Cassini VIMS has now obtained an initial image and spectrum of Saturn's H3}+ auroral emissions. [less ▲]

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See detailThe Cassini Campaign observations of the Jupiter aurora by the Ultraviolet Imaging Spectrograph and the Space Telescope Imaging Spectrograph
Ajello, Joseph M.; Pryor, Wayne; Esposito, Larry et al

in Icarus (2005), 178(2), 327-345

We have analyzed the Cassini Ultraviolet Imaging, Spectrometer (UVIS) observations of the Jupiter aurora with an auroral atmosphere two-stream electron transport code. The observations Of Jupiter by UVIS ... [more ▼]

We have analyzed the Cassini Ultraviolet Imaging, Spectrometer (UVIS) observations of the Jupiter aurora with an auroral atmosphere two-stream electron transport code. The observations Of Jupiter by UVIS took place during the Cassini Campaign. The Cassini Campaign included Support spectral and imaging observations by the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). A major result for the UVIS observations was the identification of a large color variation between the far ultraviolet (FUV: 1100-1700 angstrom) and extreme ultraviolet (EUV: 800-1100 angstrom) spectral regions. This change probably occurs because of a large variation in the ratio of the soft electron flux (10-3000 eV) responsible for the EUV aurora to the hard electron flux (similar to 15-22 keV) responsible for the FUV aurora. On the basis of this result a new color ratio for integrated intensities for EUV and FUV was defined (4 pi I1550-1620 angstrom/4 pi I (1030-1150 angstrom)) which varied by approximately a factor of 6. The FUV color ratio (4 pi I (1550-1620) angstrom/4 pi (1230-1300) (angstrom)) was note stable with a variation of less than 50% for the observations studied. The medium resolution (0.9 angstrom FWHM, G140M grating) FUV observations (1295-1345 angstrom and 1495-1540 angstrom) by STIS on 13 January 2001, on the other hand, were analyzed by a spectral modeling technique using a recently developed high-spectral resolution model for the electron-excited H-2 rotational lines. The STIS FUV data were analyzed with a model that considered the Lyman band spectrum (B (1) Sigma(u)(+) -> X-1 Sigma(g)(+)) as composed of an allowed direct excitation component (X-1 Sigma(g)(+) B-1 (+)(Sigma u)) and an optically forbidden component (X-1 Sigma(g)(+) -> EF, GK, H (H) over bar,.... (1)Sigma(u)(+) followed by the cascade transition (1)Sigma -> B-1 Sigma(u)(+)). The medium-resolution spectral regions for the Jupiter aurora were carefully chosen to emphasize the cascade component. The ratio of the two components is a direct measurement of the mean secondary electron energy of the aurora. The mean secondary electron energy of the aurora varies between 50 and 200 eV for the polar cap, limb and auroral oval observations. We examine a long time base of Galileo Ultraviolet Spectrometer color ratios from the standard mission (1996-1998) and compare them to Cassini UVIS, HST, and International Ultraviolet Explorer (IUE) observations. (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailUltraviolet Spectroscopy of Saturn: Determination of Auroral characteristics with FUSE, STIS and UVIS Spectra
Gustin, Jacques ULg; Gérard, Jean-Claude ULg; Feldman, P. D. et al

Poster (2005, September 01)

Ultraviolet (UV) lines from Saturn's aurorae are emitted following inelastic collisions between energetic electrons and H[SUB]2[/SUB] molecules. De-excitation by radiative process lead to Far Ultraviolet ... [more ▼]

Ultraviolet (UV) lines from Saturn's aurorae are emitted following inelastic collisions between energetic electrons and H[SUB]2[/SUB] molecules. De-excitation by radiative process lead to Far Ultraviolet (FUV) and Extreme Ultraviolet (EUV) emissions in the 750-1750 Å spectral window. Low resolution spectra ( 12 Å) obtained with HST/STIS in the 900-1700 Å window are employed to derive the absorption of the auroral photons by hydrocarbons (mainly methane) and depth of the auroral energy deposition. Determination of H[SUB]2[/SUB] temperature and overlying H[SUB]2[/SUB] column is achieved by analyzing spectra obtained with the FUSE instrument ( 0.2 Å resolution with the LWRS aperture in the 900-1200 Å spectral window). Below 1100 Å, transitions connecting to the v" = 0 and 1 levels of ground-state H[SUB]2[/SUB] are partially or totally absorbed by ambient H[SUB]2[/SUB] (self-absorption). Comparisons between observed and synthetic spectra allow to derive the gaz temperature and the overlying H[SUB]2[/SUB] column, which is an indicator of the depth of the aurora, hence of the energy of the precipitated electrons. Auroral spectra of Saturn at 12 Å resolution were also obtained with Cassini's Ultraviolet Imaging Spectrograph (UVIS), both in the EUV and FUV spectral bands. While the spectral resolution of UVIS is too low to estimate temperatures, the coverage of the entire UV domain allows to determine the energy of precipitated particles through the quantification of the methane and molecular hydrogen columns. Results from observations with these three instruments are presented and compared in order to characterize the auroral atmosphere and auroral electrons precipitated from Saturn's magnetosphere. [less ▲]

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See detailLocation and Morphology of Io's FUV Footprint Emissions on Jupiter
Grodent, Denis ULg; Gérard, Jean-Claude ULg; Saglam, A. et al

Conference (2005, August 07)

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See detailUltraviolet Spectroscopy of Saturn: Determination of Auroral characteristics with FUSE, STIS and UVIS Spectra
Gustin, Jacques ULg; Gérard, Jean-Claude ULg; Feldman, P. D. et al

in Bulletin of the American Astronomical Society (2005, August 01)

Ultraviolet (UV) lines from Saturn's aurorae are emitted following inelastic collisions between energetic electrons and H[SUB]2[/SUB] molecules. De-excitation by radiative process lead to Far Ultraviolet ... [more ▼]

Ultraviolet (UV) lines from Saturn's aurorae are emitted following inelastic collisions between energetic electrons and H[SUB]2[/SUB] molecules. De-excitation by radiative process lead to Far Ultraviolet (FUV) and Extreme Ultraviolet (EUV) emissions in the 750-1750 Ã spectral window. Low resolution spectra ( 12 Ã ) obtained with HST/STIS in the 900-1700 Ã window are employed to derive the absorption of the auroral photons by hydrocarbons (mainly methane) and depth of the auroral energy deposition. Determination of H[SUB]2[/SUB] temperature and overlying H[SUB]2[/SUB] column is achieved by analyzing spectra obtained with the FUSE instrument ( 0.2 Ã resolution with the LWRS aperture in the 900-1200 Ã spectral window). Below 1100 Ã , transitions connecting to the v" = 0 and 1 levels of ground-state H[SUB]2[/SUB] are partially or totally absorbed by ambient H[SUB]2[/SUB] (self-absorption). Comparisons between observed and synthetic spectra allow to derive the gaz temperature and the overlying H[SUB]2[/SUB] column, which is an indicator of the depth of the aurora, hence of the energy of the precipitated electrons. Auroral spectra of Saturn at 12 Ã resolution were also obtained with Cassini's Ultraviolet Imaging Spectrograph (UVIS), both in the EUV and FUV spectral bands. While the spectral resolution of UVIS is too low to estimate temperatures, the coverage of the entire UV domain allows to determine the energy of precipitated particles through the quantification of the methane and molecular hydrogen columns. Results from observations with these three instruments are presented and compared in order to characterize the auroral atmosphere and auroral electrons precipitated from Saturn's magnetosphere. [less ▲]

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See detailSpectral Analysis of HST-STIS Observations of Jovian UV Auroral Emissions
Gladstone, G. R.; Gérard, Jean-Claude ULg; Gustin, Jacques ULg et al

Conference (2005, August 01)

Spectral observations of Jupiter's far-ultraviolet (FUV) auroral emissions are commonly used to determine a ``color ratio, - defined as I(155-162nm) / I(123-130nm), which provides an estimate for the peak ... [more ▼]

Spectral observations of Jupiter's far-ultraviolet (FUV) auroral emissions are commonly used to determine a ``color ratio, - defined as I(155-162nm) / I(123-130nm), which provides an estimate for the peak emission altitude of the aurora and thus, assuming an accurate model atmosphere, for the mean energy of precipitating electrons. This is because the nascent emission spectrum resulting from electron impact on H[SUB]2[/SUB] is relatively unchanging over a wide range of energy, so that differential absorption by overlying CH[SUB]4[/SUB] is the primary modifier of the spectral shape of the emergent FUV emissions. This method is analogous to that used at Earth, with N[SUB]2[/SUB] LBH auroral emissions instead of H[SUB]2[/SUB] Lyman and Werner bands and differential absorption by O[SUB]2[/SUB] rather than methane. More detailed simulations of Jupiter's FUV auroral spectra can be used to place useful constraints on higher hydrocarbons, such as acetylene and ethane. Here we present a spectral analysis of HST-STIS G140L observations taken in September 1999, which include a region with the largest color ratio yet observed (i.e., the deepest aurora). A non-linear least squares model fit to the data is used to search for the presence of several important overlying hydrocarbons with strong and distinctive FUV absorption cross sections, e.g., CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]2[/SUB], C[SUB]2[/SUB]H[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], CH[SUB]3[/SUB]C[SUB]2[/SUB]H, C[SUB]3[/SUB]H[SUB]8[/SUB], C[SUB]4[/SUB]H[SUB]2[/SUB], C[SUB]2[/SUB]H[SUB]2[/SUB], and C[SUB]4[/SUB]H[SUB]10[/SUB]. We gratefully acknowledge support from NASA through grant NNG05GG97G. [less ▲]

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See detailThe electron excited ultraviolet spectrum of HD: Cross sections and transition probabilities
Ajello, J.; Palle, P. V.; Abgrall, H. et al

in Astrophysical Journal Supplement Series (2005), 159(2), 314-330

We have analyzed the high-resolution ultraviolet (UV) emission spectrum of molecular deuterium hydride (HD) excited by electron impact at 100 eV under optically thin, single-scattering experimental ... [more ▼]

We have analyzed the high-resolution ultraviolet (UV) emission spectrum of molecular deuterium hydride (HD) excited by electron impact at 100 eV under optically thin, single-scattering experimental conditions. The high-resolution spectrum (FWHM = 160 m angstrom) spans the wavelength range from 900 to 1650 angstrom and contains the two Rydberg series of HD: (1)Sigma(u)(+) 1s sigma, np sigma(B, B', B '', n = 2, 3, 4) --> X (1)Sigma(g)(+) and (1)Pi(u)(+)1s sigma, np pi(C, D', D '', D '', n = 2, 3, 4, 5) --> X (1)Sigma(g)(+). A model spectrum of HD, based on newly calculated transition probabilities and line positions including rovibrational coupling for the strongest band systems, B 1 Sigma(u)(+)- X (1)Sigma(+)(g), B' (1)Sigma(u)(+)- X (1)Sigma(g)(+), C (1)Pi(u) - X (1)Sigma(g)(+), and D (1)Pi(u) X (1)Sigma(g)(+), is in excellent agreement with observed intensities. The cross sections for direct excitation at 100 eV of the B (1)Sigma(u)(+), B' (1)Sigma(u)(+), C (1)Pi(u), and D (1)Pi(u) states were derived from a model analysis of the experimental fluorescence spectrum to the ground state. The absolute cross section values for excitation to the B (1)Sigma(u)(+), B' (1)Sigma(u)(+), C (1)Pi(u), and D (1)Pi(u) states were found to be (2.57 +/- 0.26) x 10(-17), (0.22 +/- 0.06) x 10(-17), (2.54 +/- 0,25) x 10(-17), and (0.17 +/- 0.04) x 10(-17) cm(2), respectively. We have also determined the dissociative excitation cross sections at 100 eV for the emission of Ly alpha at 1216 angstrom and Ly beta at 1025 angstrom lines, which are (7.98 +/- 1.12) x 10(-18) and (0.40 +/- 0.10) x 10(-18) cm(2), respectively. The summed excitation function of the closely spaced pair of lines, H Ly alpha and D Ly alpha, resulting from dissociative excitation of HD, has been measured from the threshold to 800 eV and is analytically modeled with a semiempirical relation. The model cross sections are in good agreement with the corrected Ly alpha cross sections of Mohlmann et al. up to 2 keV. Based on measurements of H, D (2s) production cross section values by Mohlmann et al., the H, D (n = 2) cross section is estimated to be 1.6 x 10(-17) cm(2) at 100 eV. [less ▲]

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See detailCassini ultraviolet imaging spectrograph observations of Saturn's auroras
Pryor, W. R.; West, R.; Stewart, A. I. F. et al

Conference (2005, August)

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See detailHST UV Imaging of Saturn's Southern Aurora during Simultaneous Cassini Imaging of the Northern Aurora
Clarke, J. T.; Gérard, Jean-Claude ULg; Grodent, Denis ULg et al

Conference (2005, May 01)

On 17 Feb. 2005, one week after the AGU abstract deadline, Hubble Space Telescope (HST) observations are scheduled with the Advanced Camera for Surverys (ACS) to image Saturn's UV aurora for a period of 5 ... [more ▼]

On 17 Feb. 2005, one week after the AGU abstract deadline, Hubble Space Telescope (HST) observations are scheduled with the Advanced Camera for Surverys (ACS) to image Saturn's UV aurora for a period of 5 HST orbits, or 8 hours, corresponding to 0.7 of one Saturn rotation. In the present epoch, observations from the Earth can observe nearly the entire southern auroral oval in sunlight, but none of the northern oval, due to the tilt of Saturn's axis. Over the same period, a Cassini imaging sequence will scan across the northern nightside auroral emission region from the nightside of the planet. This presents a unique opportunity to determine the relationship between the conjugate points in the auroral emission regions, along with charged particle and magnetic field measurements in the nightside Saturn magnetosphere. This campaign of observations will be presented in this paper, with a concentration on the HST images, along with scientific conclusions as appropriate. [less ▲]

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See detailMorphological differences between Saturn's ultraviolet aurorae and those of Earth and Jupiter
Clarke, J. T.; Gérard, Jean-Claude ULg; Grodent, Denis ULg et al

in Nature (2005), 433(7027), 717-719

It has often been stated that Saturn's magnetosphere and aurorae are intermediate between those of Earth, where the dominant processes are solar wind driven(1), and those of Jupiter, where processes are ... [more ▼]

It has often been stated that Saturn's magnetosphere and aurorae are intermediate between those of Earth, where the dominant processes are solar wind driven(1), and those of Jupiter, where processes are driven by a large source of internal plasma(2-4). But this view is based on information about Saturn that is far inferior to what is now available. Here we report ultraviolet images of Saturn, which, when combined with simultaneous Cassini measurements of the solar wind(5) and Saturn kilometric radio emission(6), demonstrate that its aurorae differ morphologically from those of both Earth and Jupiter. Saturn's auroral emissions vary slowly; some features appear in partial corotation whereas others are fixed to the solar wind direction; the auroral oval shifts quickly in latitude; and the aurora is often not centred on the magnetic pole nor closed on itself. In response to a large increase in solar wind dynamic pressure(5) Saturn's aurora brightened dramatically, the brightest auroral emissions moved to higher latitudes, and the dawn side polar regions were filled with intense emissions. The brightening is reminiscent of terrestrial aurorae, but the other two variations are not. Rather than being intermediate between the Earth and Jupiter, Saturn's auroral emissions behave fundamentally differently from those at the other planets. [less ▲]

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See detailSaturn's UV Aurora Imaged with HST during the Cassini Approach to Saturn
Clarke, J. T.; Gérard, Jean-Claude ULg; Grodent, Denis ULg et al

Poster (2004, December 13)

A series of HST STIS UV images of Saturn's aurora were obtained on 13 days in Jan. 2004 as the Cassini spacecraft measured the approaching solar wind properties. Clear general correlations have been found ... [more ▼]

A series of HST STIS UV images of Saturn's aurora were obtained on 13 days in Jan. 2004 as the Cassini spacecraft measured the approaching solar wind properties. Clear general correlations have been found between the auroral power and a) Saturn's kilometric radiation, and b) the solar wind dynamic pressure, but not with the direction of the interplanetary magnetic field. While these general correlations are now well established, a closer examination of the data raises many interesting questions. Saturn's auroral emissions exhibit both local time and co-rotational properties, the auroral oval does not appear centered on the magnetic and rotational pole, the auroral emissions exhibit large and unexpected motions in latitude with time and/or planetary rotation, and the auroral oval does not appear continuous, but broken with longitude. This talk will present a more detailed look at Saturn's aurora from the HST images, with a comparison of auroral emission properties to those at the Earth and Jupiter. [less ▲]

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