References of "Grodent, Denis"
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See detailObserving Jupiter’s polar stratospheric haze with HST/STIS. An HST White Paper
Grodent, Denis ULiege; Bonfond, Bertrand ULiege; Nichols, Jonathan D.

E-print/Working paper (2015)

The purpose of this HST white paper is to demonstrate that it is possible to monitor Jupiter’s polar haze with HST/STIS without breaking the ground screening limit for bright objects. This demonstration ... [more ▼]

The purpose of this HST white paper is to demonstrate that it is possible to monitor Jupiter’s polar haze with HST/STIS without breaking the ground screening limit for bright objects. This demonstration rests on a thorough simulation of STIS output from an existing image obtained with HST/WFPC2. It is shown that the STIS NUV-MAMA + F25CIII filter assembly provides a count rate per pixel ~11 times smaller than that obtained for one pixel of WFPC2 WF3 CCD + F218W corresponding filter. This ratio is sufficiently large to cope with the bright solar light scattered by Jupiter’s atmosphere, which was a lesser concern for WFPC2 CCD safety. These STIS images would provide unprecedented spatial and temporal resolution observations of small-scale stratospheric aerosol structures, possibly associated with Jupiter’s complex FUV aurora. [less ▲]

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See detailSimulations of the auroral signatures of Jupiter’s magnetospheric injections
Dumont, Maïté ULiege; Grodent, Denis ULiege; Radioti, Aikaterini ULiege et al

Poster (2015, June 04)

Jupiter’s ultraviolet auroral emissions are divided into four main components: the polar emissions, the main emission, the satellite footprints and the outer emissions. The morphology of the outer ... [more ▼]

Jupiter’s ultraviolet auroral emissions are divided into four main components: the polar emissions, the main emission, the satellite footprints and the outer emissions. The morphology of the outer emissions can be either diffuse, arc-shaped or compact emissions. In the present study, we focus on outer emissions clearly detaching from the main emission and forming compact structures that are evolving regardless of the rest of the auroral emission. These auroral features were selected because they have the same appearance as the auroral signature of a clearly identified injection previously observed by Mauk et al. [2002] at Jupiter, based on simultaneous Galileo spacecraft and Hubble Space Telescope measurements. Here, we report on the evolution of those ultraviolet auroral features appearing in Hubble Space Telescope images of the northern and southern Jovian hemispheres. We investigate the possibility that those ultraviolet auroral structures are associated with energetic particle injections. For this study, we analyze the temporal variations of the longitudinal extent and of the brightness of the auroral structures. Indeed, the injected charged particles drift at different rates due to energy-dependent gradient and curvature drifts, which leads to an increase with time of the longitudinal extent of the feature and of its associated auroral signature. Since the injected energy follows the same trend, the brightness decreases with time. Different processes can generate auroral signatures of plasma injections. We simulate them by considering that pitch angle diffusion is generated by the precipitating energy flux in the ionosphere and whistler-mode waves through electron scattering. We compare the characteristics of the simulated signature with the observed parameters. Following this comparison, we are able to test whether the aforementioned mechanism is responsible for the auroral emission and to infer the typical energy and the spectral index of the energy distribution of the electrons involved in the injection process. [less ▲]

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See detailThe Main Auroral Emission at Jupiter: Altitude profile and Dawn-Dusk Asymmetry
Bonfond, Bertrand ULiege; Gustin, Jacques ULiege; Gérard, Jean-Claude ULiege et al

Poster (2015, June 04)

The main auroral emission at Jupiter generally forms a quasi-continuous curtain around each magnetic poles. This emission magnetically maps to the middle magnetosphere and is related to the corotation ... [more ▼]

The main auroral emission at Jupiter generally forms a quasi-continuous curtain around each magnetic poles. This emission magnetically maps to the middle magnetosphere and is related to the corotation enforcement of the plasma originating from the volcanic satellite Io. The first models of corotation enforcement current system at Jupiter assumed symmetry around the magnetic axis. However, observations and further development of these models outlined the importance of local time variability of such currents. In this presentation, we show the results of two studies of this local time variability relying on the large dataset of Far-UV observations from the Hubble Space Telescope (HST). Knight’s theory of field aligned current predicts that the auroral precipitating energy flux and the energy of the precipitating electrons are correlated. Since the altitude of the auroral emissions decreases as the energy increases, it is thus expected that the altitude of the auroral brightness peak varies as a function of the local time following the variations of the field aligned currents. We compare the altitude of the main emission on the post-dusk side as seen in the visible domain by Galileo’s Solid State Imager and the same altitude for the night side as seen by the Advanced Camera for Surveys (ACS) on board HST in the Far-UV domain. We show some significant differences between the two data sets. Unfortunately, a careful analysis involving both spectral observations and simulations indicates that the Far-UV vertical profiles are hampered by observational ambiguities due to absorption by hydrocarbon molecules. Only additional and judiciously designed new observations could reveal the actual amount of methane along the line of sight. The second study consists in a comparison of the emitted power in local time sectors corresponding to dawn and dusk. Results in the northern hemisphere are difficult to interpret because the magnetic anomaly probably causes a decrease of the auroral brightness in regions of strong magnetic field. In the southern hemisphere, where the field magnitude is more uniform along the main oval, the dusk sector is ~3 times brighter than the dawn sector. In accordance with measurements of magnetic field divergence in the equatorial plane by Galileo, these results suggest the presence of a partial ring current in the night side of the magnetosphere with upward currents in the dawn side and downward currents in the dusk side. [less ▲]

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See detailHubble spectral observations of the Jovian aurora: precipitated flux and electron mean energy
Gérard, Jean-Claude ULiege; Bonfond, Bertrand ULiege; Grodent, Denis ULiege et al

Conference (2015, June 02)

The FUV Jovian aurora is excited by collisions of energetic electrons accelerated along the magnetic field lines with the ambient upper atmosphere. The emission is dominated by the H2 Lyman and Werner ... [more ▼]

The FUV Jovian aurora is excited by collisions of energetic electrons accelerated along the magnetic field lines with the ambient upper atmosphere. The emission is dominated by the H2 Lyman and Werner bands extending from the extreme ultraviolet to about 170 nm. The wavelengths below about 135 nm are partly absorbed by the methane layer overlying the auroral emission layer. The long wavelength intensity is proportional to the precipitated energy flux carried by the auroral electrons. Spectral observations with the Hubble Space Telescope were made in 2014 using the long slit of the Space Telescope Imaging Spectrograph (STIS) in the timetag mode. During these observations, the slit projection scanned the polar region down to mid-latitudes. The combination of spectral and temporal measurements was used to build up the first spectral maps of the FUV Jovian aurora. The two-dimensional distribution of the intensity ratio of the two spectral regions has been obtained by combining spectral emissions in these wavelength ranges. They show that the amount of absorption by methane varies significantly between the different components of the aurora and in the polar region. Outputs from an electron transport model are used to create maps of the distribution of the characteristic electron energies. Using model atmospheres adapted to auroral conditions, we conclude that electron energies generally range between a few tens to several hundred keV. In this presentation, we analyze the relationship between the precipitated electron energy flux and the mean electron energy derived from these observations. Although globally, no correlation can be found, we show that the two quantities co-vary in some auroral components such as in the morning sector or in the striations observed along the main emission. By contrast, the auroral input in some high-latitude regions show no correlation with the electron characteristic energy. These aspects will be quantitatively discussed and possible processes explaining this dichotomy will be proposed. Comparisons of derived energies are in general agreement with those calculated from magnetosphere-ionosphere coupling models, but they locally exceed current model predictions. These results provide a basis for three-dimensional modeling of the distribution of particle heat sources into the high-latitude Jovian upper atmosphere. [less ▲]

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See detailAuroral emission at Jupiter, through Juno's UVS eyes
Grodent, Denis ULiege; Bonfond, Bertrand ULiege; Gladstone, G. et al

Conference (2015, June 02)

Juno’s orbit insertion around Jupiter will take place in little bit more than one year (July 2016). After a 107-day capture orbit (Oct. 2016), it will perform a series of 33 eleven-day science polar ... [more ▼]

Juno’s orbit insertion around Jupiter will take place in little bit more than one year (July 2016). After a 107-day capture orbit (Oct. 2016), it will perform a series of 33 eleven-day science polar orbits offering unprecedented views of the auroral regions of Jupiter. The science payload of Juno includes an UltraViolet Spectrograph (UVS) that will characterize the UV auroral emissions of Jupiter over all science orbits. It will obtain high-resolution images and spectra that will provide context for Juno’s in situ particles and fields measurements in the larger polar magnetosphere with Juno’s JADE and JEDI detectors. At the same time, the MAG instrument will accurately constrain magnetic field models, which will provide the connection between Juno and its field line footprint in the Jovian aurora. The UVS instrument consists of a solar blind MCP detector with a “dog-bone” shape FOV of 0.2°x2.5°+0.025°x2°+0.2°x2.5° providing a spatial resolution of 125 km from 1RJ above the aurora and a spectral resolution of ~0.5 nm (~2 nm for extended sources). It is sensitive to EUV-FUV radiation ranging from 70 nm to 205 nm. Juno is a spin-stabilized spacecraft and is rotating at a frequency of 2 RPM. UVS will take advantage of this motion to scan the auroral regions in the direction perpendicular to the slit, while its steerable pickup mirror (±30° from the spin plane) will make it possible to point at specific regions of the aurora. Juno’s highly eccentric science orbits have a perijove close to 1.05 RJ (~5000 km above cloud deck) and an apojove at ~38 RJ. These orbits approximately lie in the Dawn meridian plane and are such that each successive pass is at a Jovian longitude displaced by 204° from the previous perijove. At perijove, Juno’s velocity will be ~60 km/s and about 20 km/s above the poles, meaning that the spacecraft will move over the northern and southern auroral regions in approximately two hours. In this study, we are using existing HST STIS time-tag sequences of Jupiter’s UV aurorae in order to simulate the expected measurements through UVS FOV along Juno’s predicted trajectory. The simulations account for realistic instrumental specifications and pointing and for the temporal and spatial variability of the aurora. We show the results of image reconstruction obtained from scanning the auroral region with UVS slit and provide some limits on the expected data quality as a function of the location of Juno along its orbit. We also suggest portions of the science orbits for which supporting HST observations will be necessary. [less ▲]

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See detailMagnetosphere-ionosphere mapping at Jupiter: Quantifying the effects of using different internal field models
Vogt, Marissa F.; Bunce, Emma J.; Kivelson, Margaret G. et al

Conference (2015, June)

The lack of global field models accurate beyond the inner magnetosphere (< 30 RJ) makes it difficult to relate Jupiter’s polar auroral features to magnetospheric source regions. Vogt et al. [2011] map ... [more ▼]

The lack of global field models accurate beyond the inner magnetosphere (< 30 RJ) makes it difficult to relate Jupiter’s polar auroral features to magnetospheric source regions. Vogt et al. [2011] map Jupiter’s equatorial magnetosphere to the ionosphere using a flux equivalence calculation that requires equal flux at the equatorial and ionospheric ends of flux tubes. This approach is more accurate than tracing field lines in a global field model, but only if it is based on an accurate model of Jupiter’s internal field. At present there are three widely used internal field models – VIP4, the Grodent anomaly model (GAM), and VIPAL. We will present results of a recently published study that quantifies how the choice of an internal field model affects the mapping of various auroral features using the Vogt et al. [2011] flux equivalence calculation. We find that different internal field models can shift the ionospheric mapping of points in the equatorial plane by several degrees and shift the magnetospheric mapping to the equator by ~30 Jovian radii radially and by less than one hour in local time. These shifts are consistent with differences in how well each model maps the Ganymede footprint, underscoring the need for more accurate Jovian internal field models. Understanding these differences is important for the continued analysis of HST images and in planning for Juno’s arrival at Jupiter in 2016. We will discuss differences in the size and location of the open/closed field line boundary and the mapping of specific auroral features, like polar dawn spots. We will also present some new analysis of the mapping of Jupiter’s main auroral oval and relate this to temporal variability observed in Jupiter’s magnetodisk. [less ▲]

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See detailSearch for Satellite Effects on Saturn's Auroras in Cassini UVIS Data
Pryor, Wayne; Espositio, Larry; Jouchoux, Alain et al

Poster (2015, June)

The Cassini Ultraviolet Imaging Spectrograph (UVIS) has been obtaining Saturn auroral images since 2004. We have previously reported instances when the main auroral oval brightened briefly in a quasi ... [more ▼]

The Cassini Ultraviolet Imaging Spectrograph (UVIS) has been obtaining Saturn auroral images since 2004. We have previously reported instances when the main auroral oval brightened briefly in a quasi-periodic fashion near the sub-Mimas longitude. Here we examine the large set of UVIS auroral images obtained from close range and high sub-spacecraft latitudes. We will plot the brightness of the individual auroral measurements (and binned auroral measurements) as a function of local time, and as a function of the location of Mimas and other moons to test for any correlations. Mimas, while a relatively small moon, exerts a strong influence on Saturn's ring system. Mimas creates the Cassini Division between the A and B rings and forces a non-circular shape to the outer edge of Saturn's B ring that is partially locked to Mimas phase. [less ▲]

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See detailHubble Space Telescope observations of variation of the O I 135.6 nm/ O I 130.4 nm ratio in Ganymede’s atmosphere
Molyneux, P. M.; Nichols, J. D.; Bannister, N. P. et al

Poster (2015, June)

We present new high-sensitivity HST/COS measurements of the atmospheric O I 135.6 nm/ O I 130.4 nm ratio at Ganymede, which we show exhibits significant spatial and temporal variability. Specifically, the ... [more ▼]

We present new high-sensitivity HST/COS measurements of the atmospheric O I 135.6 nm/ O I 130.4 nm ratio at Ganymede, which we show exhibits significant spatial and temporal variability. Specifically, the ratios observed on Ganymede’s leading hemispheres vary between 2.14±0.03 and 2.67±0.02, while on the trailing hemisphere the ratios are observed to be between 0.98±0.02 and 1.53±0.03. These high-sensitivity observations increase the signal to noise of these measurements by an order of magnitude over previous HST/STIS observations of the same [1], thus confirming that the temporal variation suggested by these previous observations is real. The emissions are excited through electron-impact excitation of Ganymede’s oxygen atmosphere by electrons which are locally accelerated within its magnetosphere [2,3]. The variation in the ratio magnitude may be explained either by variations in the ratio of atomic to molecular oxygen in the atmosphere or by a change in the temperature of the electrons exciting the emissions. An increase in the proportion of molecular oxygen acts to increase the ratio, as does a cooler electron temperature.References [1] Feldman, P. D., McGrath, M. A., Strobel, D. F., Moos, H. W., Retherford, K. D. and Wolven, B. C., HST/STIS ultraviolet imaging of polar aurora on Ganymede, Astrophys. J., Vol. 535, pp. 1085-1090, 2000. [2] Hall, D. T., Feldman, P. D., McGrath, M. A. and Strobel, D. F., The far-ultraviolet oxygen airglow of Europa and Ganymede, Astrophys. J., Vol. 499, pp. 475-481, 1998. [3] Eviatar, A., Strobel, D. F., Wolven, B. C., Feldman, P. D., McGrath, M. A. and Williams, D. J., Excitation of the Ganymede ultraviolet aurora, Astrophys. J., Vol. 555, pp. 1013-1019, 2001. [less ▲]

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See detailCharacteristics of Jupiter's auroral acceleration region
Ray, Licia; Gustin, Jacques ULiege; Grodent, Denis ULiege

Poster (2015, June)

Jupiter’s dynamic auroral region is the signature of magnetosphere-ionosphere coupling. The magnetospheric drivers of the emission are relatively well understood, yet the high-latitude characteristics of ... [more ▼]

Jupiter’s dynamic auroral region is the signature of magnetosphere-ionosphere coupling. The magnetospheric drivers of the emission are relatively well understood, yet the high-latitude characteristics of the interaction have not been measure in-situ. Ahead of Juno’s arrival next summer, we use HST STIS observations of Jupiter’s auroral emission to infer the location of Jupiter’s auroral acceleration region and the properties of the precipitating auroral electrons. We analyze two images of Jupiter’s northern emission, determining the precipitating electron energy and incident energy flux for the main aurora, Io spot, Ganymede footprint, and flare regions. The resulting relationships between energy flux and electron precipitation energy for the main auroral emission are compared to the theoretical relationship derived by Lundin & Sandahl [1978] for a range of auroral region locations, and temperatures and densities appropriate for the jovian system. [less ▲]

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See detailAuroral Morphologies of Jupiter and Saturn
Grodent, Denis ULiege

Conference (2015, May 31)

We review the principal differences and similarities of the morphologies of Jupiter and Saturn's auroral emissions. We then show some examples of UV images that are expected to be acquired with Cassini ... [more ▼]

We review the principal differences and similarities of the morphologies of Jupiter and Saturn's auroral emissions. We then show some examples of UV images that are expected to be acquired with Cassini UVIS at Saturn and Juno UVS at Jupiter. [less ▲]

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See detailAt the heart of Jupiter’s aurora; at the crossroads of Astrophysics Geophysics and Plasma Physics
Grodent, Denis ULiege

Scientific conference (2015, May 21)

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow ... [more ▼]

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow rotating pulsars. For these two planets, there is a direct link between this pulsar-like behaviour and the auroral processes that are taking place in their atmosphere. We will take the example of Jupiter to illustrate haw the aurora is generated in the magnetosphere as a result of the volcanic activity of the moon Io. The ultraviolet aurora of Jupiter is conveniently described in terms of components located inside (poleward of) or outside (equatorward of) the main oval emission. However, these components may also be discriminated by their temporal behaviour, where the narrowest parts of the main “oval” remain relatively stable over time periods of several hours, and the satellite footprints show large variability with timescales of minutes. Inside the main emission, at the heart of the aurora, the so-called polar aurora, presumably corresponding to the polar cap mixing open and closed magnetic field lines, is characterized by rapid motions taking the form of swirls, giving rise to the “swirl region” and by beatings in the “active region”. This delicate auroral region is difficult to apprehend because of its ever-changing shape and because of the lack of appropriate tools to study it. [less ▲]

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See detailAuroral emissions at Jupiter and Saturn, at the crossroads of Astrophysics Geophysics and Plasma Physics
Grodent, Denis ULiege

Conference (2015, May 13)

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow ... [more ▼]

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow rotating pulsars. For these two planets, there is a direct link between this pulsar-like behaviour and the auroral processes that are taking place in their atmosphere. We will take the example of Jupiter to illustrate haw the aurora is generated in the magnetosphere as a result of the volcanic activity of the moon Io. [less ▲]

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See detailJupiter's equatorward auroral features
Dumont, Maïté ULiege; Grodent, Denis ULiege; Radioti, Aikaterini ULiege et al

Conference (2015, May 13)

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See detailA Brief Review of Ultraviolet Auroral Emissions on Giant Planets
Grodent, Denis ULiege

in Space Science Reviews (2015), 187(1-4), 23-50

The morphologies of the ultraviolet auroral emissions on the giant gas planets, Jupiter and Saturn, have conveniently been described with combinations of a restricted number of basic components. Although ... [more ▼]

The morphologies of the ultraviolet auroral emissions on the giant gas planets, Jupiter and Saturn, have conveniently been described with combinations of a restricted number of basic components. Although this simplified view is very handy for a gross depiction of the giant planets’ aurorae, it fails to scrutinize the diversity and the dynamics of the actual features that are regularly observed with the available ultraviolet imagers and spectrographs. In the present review, the typical morphologies of Jupiter and Saturn’s aurorae are represented with an updated and more accurate set of components. The use of sketches, rather than images, makes it possible to compile all these components in a single view and to put aside ultraviolet imaging technical issues that are blurring the emission sources, thus preventing one from disentangling the different auroral signatures. The ionospheric and magnetospheric processes to which these auroral features allude can then be more easily accounted. In addition, the use of components of the same kind for both planets may help to put forward similarities and differences between Jupiter and Saturn. The case of the ice giants Uranus and Neptune is much less compelling since their weak auroral emissions are very poorly documented and one can only speculate about their origin. This review presents a current perspective that will inevitably evolve in the future, especially with upcoming observing campaigns and forthcoming missions like Juno. [less ▲]

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See detailThe crucial role of HST during the NASA Juno mission: a “Juno initiative”
Grodent, Denis ULiege; Bonfond, Bertrand ULiege; Gérard, Jean-Claude ULiege et al

E-print/Working paper (2015)

In 2016, the NASA Juno spacecraft will initiate its one-year mission around Jupiter and become the first probe to explore the polar regions of Jupiter. The HST UV instruments (STIS and ACS) can greatly ... [more ▼]

In 2016, the NASA Juno spacecraft will initiate its one-year mission around Jupiter and become the first probe to explore the polar regions of Jupiter. The HST UV instruments (STIS and ACS) can greatly contribute to the success of the Juno mission by providing key complementary views of Jupiter’s UV aurora from Earth orbit. Juno carries an ultraviolet Spectrograph (UVS) and an infrared spectral mapper (JIRAM) that will obtain high-resolution spectral images providing the auroral counterpart to Juno’s in situ particles and fields measurements with the plasma JADE and JEDI particle detectors. The Juno mission will be the first opportunity to measure simultaneously the energetic particles at high latitude and the auroral emissions they produce. Following programmatic and technical limitations, the amount of UVS data transmitted to Earth will be severely restricted. Therefore, it is of extreme importance that HST captures as much additional information as possible on Jupiter’s UV aurora during the one-year life of the Juno mission. This white paper is a plea for a “Juno initiative” that will ensure that a sufficient number of orbits is allocated to this unique solar system mission. [less ▲]

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See detailMagnetosphere-ionosphere mapping at Jupiter: Quantifying the effects of using different internal field models
Vogt, Marissa; Bunce, Emma; Kivelson, Margaret et al

in Journal of Geophysical Research. Space Physics (2015), 120

The lack of global field models accurate beyond the inner magnetosphere (<30 RJ) makes it difficult to relate Jupiter's polar auroral features to magnetospheric source regions. We recently developed a ... [more ▼]

The lack of global field models accurate beyond the inner magnetosphere (<30 RJ) makes it difficult to relate Jupiter's polar auroral features to magnetospheric source regions. We recently developed a model that maps Jupiter's equatorial magnetosphere to the ionosphere using a flux equivalence calculation that requires equal flux at the equatorial and ionospheric ends of flux tubes. This approach is more accurate than tracing field lines in a global field model but only if it is based on an accurate model of Jupiter's internal field. At present there are three widely used internal field models—Voyager Io Pioneer 4 (VIP4), the Grodent Anomaly Model (GAM), and VIP Anomaly Longitude (VIPAL). The purpose of this study is to quantify how the choice of an internal field model affects the mapping of various auroral features using the flux equivalence calculation. We find that different internal field models can shift the ionospheric mapping of points in the equatorial plane by several degrees and shift the magnetospheric mapping to the equator by ~30 RJ radially and by less than 1 h in local time. These shifts are consistent with differences in how well each model maps the Ganymede footprint, underscoring the need for more accurate Jovian internal field models. We discuss differences in the mapping of specific auroral features and the size and location of the open/closed field line boundary. Understanding these differences is important for the continued analysis of Hubble Space Telescope images and in planning for Juno's arrival at Jupiter in 2016. [less ▲]

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See detailThe EChO science case
Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul et al

in Experimental Astronomy (2015), 1502

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general ... [more ▼]

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. EChO can target the atmospheres of super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300K-3000K) of F to M-type host stars. Over the next ten years, several new ground- and space-based transit surveys will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO's launch and enable the atmospheric characterisation of hundreds of planets. Placing the satellite at L2 provides a cold and stable thermal environment, as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. A 1m class telescope is sufficiently large to achieve the necessary spectro-photometric precision. The spectral coverage (0.5-11 micron, goal 16 micron) and SNR to be achieved by EChO, thanks to its high stability and dedicated design, would enable a very accurate measurement of the atmospheric composition and structure of hundreds of exoplanets. [less ▲]

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See detailIn Overview of the Auroras of Jupiter and Saturn from the Cassini Perspective (Invited)
Pryor; Esposito; Jouchoux et al

Conference (2015)

The Cassini spacecraft flew by Jupiter in late 2000 and early 2001 and has been orbiting Saturn since 2004. A highlight of the mission has been an unprecedented collection of high-resolution auroral ... [more ▼]

The Cassini spacecraft flew by Jupiter in late 2000 and early 2001 and has been orbiting Saturn since 2004. A highlight of the mission has been an unprecedented collection of high-resolution auroral images of Saturn obtained in the visible by Cassini ISS, in the infrared by Cassini VIMS, and in the ultraviolet by Cassini UVIS. We will briefly discuss auroral observations of Jupiter by Cassini showing auroral storms and episodes of periodic pulsations, then highlights from the large database of Saturn auroral images and movies, and complementary fields and particles data. Complementary and sometimes simultaneous HST images will also be shown. Saturn's auroras exhibit a wide variety of changing forms. At times multiple narrow arcs are seen, at other times a single broader emission is seen. The polar cap inside the oval exhibits changing discrete forms, often near noon local time in the polar cusp region. Satellite footprints associated with Enceladus are very rarely seen. Bright auroral pulsations on the main oval sometimes occur, separated by about an hour. At times these seem associated with the moon Mimas, occurring at the sub-Mimas longitude and moving with the moon. We indicate a possible mechanism for this, involving Mimas control of the width of the Cassini Division, which forms a channel for plasma flow connecting Saturn's rings and/or flowing through Saturn's rings. [less ▲]

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See detailAuroral spirals at Saturn
Radioti, Aikaterini ULiege; Grodent, Denis ULiege; Gérard, Jean-Claude ULiege et al

in Journal of Geophysical Research. Space Physics (2015)

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See detailIn-situ & remote sensing studies of outer planet aurora
Badman, S.V.; Baines, K.H.; Bonfond, Bertrand ULiege et al

Conference (2015)

The combination of in situ and remote sensing measurements of auroral processes has yielded a wealth of information about solar wind-magnetosphere-ionosphere coupling at the giant planets. Results from ... [more ▼]

The combination of in situ and remote sensing measurements of auroral processes has yielded a wealth of information about solar wind-magnetosphere-ionosphere coupling at the giant planets. Results from the 2014 joint HST-Cassini Saturn auroral campaign are highlighted to demonstrate some of the interesting features observed in situ and their auroral counterparts, including: (1) perturbations on tens of minutes timescales in the high latitude ion fluxes, magnetic field, broadband plasma waves, and auroral intensity; (2) corotating auroral intensifications and their correspondence with models of the planetary period oscillations based on magnetic field perturbations; and (3) sub-corotating auroral features and their relationship to ring current enhancements observed in Energetic Neutral Atom (ENA) observations [less ▲]

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