References of "Clarke, J"
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See detailThe variation of different components of Jupiter's auroral emission
Nichols, J.; Clarke, J.; Gérard, Jean-Claude ULg et al

Conference (2008, December 01)

In this paper we use the extensive HST data set obtained over two month-long campaigns in 2007 to determine the long term variability of the different components of Jupiter's auroras. We define three ... [more ▼]

In this paper we use the extensive HST data set obtained over two month-long campaigns in 2007 to determine the long term variability of the different components of Jupiter's auroras. We define three regions on the planet's disc, i.e. the main oval, the low latitude, and high latitude auroras, and extract the UV auroral power emitted therefrom. The high latitude region was also further divided into the polar inner and polar outer regions. We discuss the temporal variation of these parameters with reference to the auroral morphology and estimated solar wind conditions projected to Jupiter's orbit from data obtained at Earth orbit. We show that the auroral morphology was very different between the first and second campaigns. In the first campaign the emitted power originated mainly from the main oval and the high latitude regions, which roughly correlated, and exhibited enhancements that are suggested to be associated with compression regions. In the second campaign the high latitude and main oval auroras were generally dimmer overall and less variable, while the low latitude region was populated with bright, patchy emission. We show that a particular auroral morphology is probably associated specifically with compression regions, i.e. over longitudes greater than approx. 180 degrees the main oval is bright and located approx. 1 degree poleward of its previous location, while over smaller longitudes the main oval is not bright or well defined. Instead there is bright emission originating from the contiguous poleward region in the afternoon/dusk sector where bright, sometimes multiple arcs form. It remains unclear, however, whether this state is a response to the initial shock or some other event within the rapidly-varying compression regions. We also show that the dawn storm events, typically associated with intense dawn side main oval auroras also result in the brightening of the high latitude auroras, even to the very highest latitude components, which presumably map to a very different region of the magnetosphere. However, apart from the dawn storms and bright poleward arcs in the afternoon/dusk sector, the power emitted from the poleward auroras is generally uncorrelated with that of the main oval. [less ▲]

Detailed reference viewed: 22 (2 ULg)
See detailSaturn Auroral Movies from Cassini UVIS
Pryor, W. R.; Stewart, I.; Esposito, L. et al

Conference (2008, December 01)

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed four 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 four 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. Auroral emissions are seen from electron-excited molecular and atomic hydrogen. In 2008 UVIS obtained data with the spacecraft well out of Saturn's ring plane, permitting UVIS to obtain a number of short movies of the rotating auroral structures. In some movies a cusp-like feature is present near noon inside the oval. One movie from 2008 day 201 shows parallel linear features on the day side almost at right angles to the main auroral oval that appear, then lengthen, separate in the middle, and then fade away. The same movie also shows one bright "polar flare" inside the oval. A few of the most recent images were obtained at sufficiently close range that 2 spacecraft slews were needed to completely cover the oval. These images provide almost 100 pixels of information across the oval and clearly show multiple arcs of emission on the main oval and scattered emissions inside the oval. We will discuss these features, their locations, and possible interpretations. [less ▲]

Detailed reference viewed: 47 (2 ULg)
See detailAuroral Movies and Spectroscopy from Cassini UVIS
Pryor, W. R.; West, R.; Stewart, I. et al

Conference (2007, December 01)

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed three 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 three 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. Auroral emissions are seen from electron-excited molecular and atomic hydrogen. In 2007 UVIS obtained data with the spacecraft well out of Saturn's ring plane, permitting us to create images, spectra, and at times movies. We will present an auroral movie from 2007-145 that has been processed to remove flat-fielding artifacts and deconvolved to remove scattering along the slit. The movie shows near co- rotation of N polar auroral features with the planet's rotation. An auroral oval is present. The oval appears doubled on the midnight side. Other images from this year show emissions inside the auroral oval. We will discuss these images and their spectra. Additional images and movies are planned in coming months. [less ▲]

Detailed reference viewed: 36 (1 ULg)
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 ▲]

Detailed reference viewed: 31 (1 ULg)
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 ▲]

Detailed reference viewed: 32 (6 ULg)
See detailThe Solar Wind Upstream of Saturn: Cassini Plasma measurements and Saturn's Aurora
Crary, F. J.; Young, D. T.; Barraclough, B. et al

Conference (2004, May 17)

For a full solar rotation in January and early February, 2004, the Cassini spacecraft and Hubble and Chandra Space Telescopes were used to make simultaneous observations of the solar wind and Saturn's ... [more ▼]

For a full solar rotation in January and early February, 2004, the Cassini spacecraft and Hubble and Chandra Space Telescopes were used to make simultaneous observations of the solar wind and Saturn's aurora. We report here on initial results from data taken with the Cassini Plasma Spectrometer's electron and high-resolution ion sensors in the solar wind upstream of Saturn. These measurements, combined with those of other particles and fields instruments on Cassini show two shock and corotating interaction regions, which reached Saturn approximately twelve hours later. An auroral response to each of these events was observed by the Hubble Space Telescope. [less ▲]

Detailed reference viewed: 63 (4 ULg)
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Peer Reviewed
See detailDYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields
Chassefière, E.; Nagy, A.; Mandea, M. et al

in Advances in Space Research (2004), 33

DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to ... [more ▼]

DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to better understand the magnetic, geologic and thermal history of Mars. The internal structure and evolution of Mars is thought to have influenced climate evolution. The collapse of the primitive magnetosphere early in Mars history could have enhanced atmospheric escape and favored transition to the present arid climate. These objectives are achieved by using a low periapsis orbit. DYNAMO has been proposed in response to the AO released in February 2002 for instruments to be flown as a complementary payload onboard the CNES Orbiter to Mars (MO-07), foreseen to be launched in 2007 in the framework of the French PREMIER Mars exploration program. MO-07 orbital phase 2b (with an elliptical orbit of periapsis 170 km), and in a lesser extent 2a, offers an unprecedented opportunity to investigate by in situ probing the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, and therefore the present atmospheric escape rate. Ultraviolet remote sensing is an essential complement to characterize high, tenuous, layers of the atmosphere. One Martian year of operation, with about 5,000 low passes, should allow DYNAMO to map in great detail the residual magnetic field, together with the gravity field. Additional data on the internal structure will be obtained by mapping the electric conductivity, sinergistically with the NETLANDER magnetic data. Three options have been recommended by the International Science and Technical Review Board (ISTRB), who met on July 1st and 2nd, 2002. One of them is centered on DYNAMO. The final choice, which should be made before the end of 2002, will depend on available funding resources at CNES. [less ▲]

Detailed reference viewed: 43 (2 ULg)
See detailComparison of auroral processes at Jupiter and Saturn
Clarke, J.; Gérard, Jean-Claude ULg

Conference (2003, April 01)

Extensive series of images of Jupiter's aurora have been obtained from HST and ground-based telescopes, while only a handful of images of Saturn's aurora have been taken to date and only with the HST ... [more ▼]

Extensive series of images of Jupiter's aurora have been obtained from HST and ground-based telescopes, while only a handful of images of Saturn's aurora have been taken to date and only with the HST. With the Cassini spacecraft approaching Saturn, it is timely to compare what we know of Saturn's aurora with the better-studied case of Jupiter. This presentation will summarize the basic features of Jupiter's auroral processes, give an overview of what we know about Saturn's auroral processes, and speculate on what might be learned from further studies at the time of Cassini approach to Saturn. [less ▲]

Detailed reference viewed: 10 (1 ULg)
See detailCassini UVIS and HST STIS Time-Resolved Jupiter Auroral Data Compared to QP Radio Bursts
Pryor, W.; Hospodarsky, G.; Stewart, I. et al

Poster (2003)

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Jupiter in a 4-sec integration "high time-resolution mode" on Jan 8, 13-14, and 20-21 in 2001. In this mode Extreme-Ultraviolet and Far ... [more ▼]

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Jupiter in a 4-sec integration "high time-resolution mode" on Jan 8, 13-14, and 20-21 in 2001. In this mode Extreme-Ultraviolet and Far-Ultraviolet spectra were obtained with reduced spectral and spatial resolution in order to study rapid variations in H2 band and H Lyman alpha emission. Previous work has shown that the region inside Jupiter's main auroral ovals contains highly variable spots of emission (auroral flares) that persist for typically 1 or 2 minutes. This duration is similar to that in Jupiter's quasi-periodic (QP) radio bursts. We compare UVIS data to simultaneous Galileo Plasma Wave Subsystem (PWS) and Cassini Radio and Plasma Wave Subsystem (RPWS) observations. Jan 8 was an active period for UV variability, that we associate with polar auroral flares. There is a correlation between the radio and UV bursts in this period, suggesting that they are related phenomena. We will also explore coordinated Hubble Space Telescope Imaging Spectrograph (STIS) time-tagged UV images from Dec 14 and Dec 16, 2000, and Jan 13-14, and Jan 20-21, 2001 to study the spatial properties of the auroral flares. The auroral emissions inside the main oval were most prominent in the Dec 14, 2000 HST data. We acknowledge support from the Cassini Project, the Space Telescope Science Institute, and the NASA OSS Minority University Initiative. [less ▲]

Detailed reference viewed: 8 (0 ULg)
See detailCassini UVIS time-resolved Jupiter auroral data compared to QP radio bursts
Pryor, W.; Hospodarsky, G.; Stewart, I. et al

Poster (2003)

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Jupiter in a 4-sec integration "high time-resolution mode" on Jan 8, 13-14, and 20-21 in 2001. In this mode Extreme-Ultraviolet and Far ... [more ▼]

The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Jupiter in a 4-sec integration "high time-resolution mode" on Jan 8, 13-14, and 20-21 in 2001. In this mode Extreme-Ultraviolet and Far-Ultraviolet spectra were obtained with reduced spectral and spatial resolution in order to study rapid variations in H2 band and H Lyman alpha emission. Previous work has shown that the region inside Jupiter's main auroral ovals contains highly variable spots of emission (auroral flares) that persist for typically 1 or 2 minutes. This duration is similar to that in Jupiter's quasi-periodic (QP) radio bursts. We compare UVIS data to simultaneous Galileo Plasma Wave Subsystem (PWS) and Cassini Radio PWS (RPWS) observations. Jan 8 was an active period for UV variability, that we associate with polar auroral flares. There is a correlation between the radio and UV bursts in this period, suggesting that they are related phenomena. We will also explore coordinated Hubble Space Telescope Imaging Spectrograph time-tagged UV images from Jan 13-14 and Jan 20-21, 2001 to study the spatial properties of the auroral flares. [less ▲]

Detailed reference viewed: 7 (0 ULg)
See detailX-Ray Emissions from Jupiter
Gladstone, G.; Waite, J.; Grodent, Denis ULg et al

Conference (2001, May 29)

X-ray emissions from Jupiter have been observed for over 20~years. Jovian x-ray emissions are associated with the high-latitude aurora and with solar fluorescence and/or an energetic particle source at ... [more ▼]

X-ray emissions from Jupiter have been observed for over 20~years. Jovian x-ray emissions are associated with the high-latitude aurora and with solar fluorescence and/or an energetic particle source at low-latitudes as identified by past Einstein and ROSAT observations. Enhanced auroral x-rays were also observed to be associated with the impact of Comet Shoemaker-Levy~9. The high-latitude x-ray emissions are best explained by energetic sulfur and oxygen ion precipitation from the Jovian magnetosphere, a suggestion that has been confirmed by recent Chandra ACIS observations. Exciting new information about Jovian x-ray emissions has been made possible with Chandra's High Resolution Camera. We report here for the first time the detection of a forty minute oscillation associated with the Jovian x-ray aurora. With the help of ultraviolet auroral observations from Hubble Space Telescope, we pinpoint the auroral mapping of the x-rays and provide new information on the x-ray source mechanism. [less ▲]

Detailed reference viewed: 5 (0 ULg)