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See detailSun-Earth Interaction
Grodent, Denis ULiege

Learning material (2017)

Sun-Earth Interaction

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See detailRadiative Transfer
Grodent, Denis ULiege

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Radiative Transfer

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See detailIntroduction (master in aerospace engineering)
Grodent, Denis ULiege

Learning material (2017)

Introduction

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See detailAtmospheric structure
Grodent, Denis ULiege

Learning material (2017)

Atmospheric structure

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See detailIntroduction
Grodent, Denis ULiege

Learning material (2017)

Introduction

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See detailThe tails of the satellite auroral footprints at Jupiter
Bonfond, Bertrand ULiege; Saur, J.; Grodent, Denis ULiege et al

in Journal of Geophysical Research. Space Physics (2017), 122

The electro-magnetic interaction between Io, Europa and Ganymede and the rotating plasma that surrounds Jupiter has a signature in the aurora of the planet. This signature, called the satellite footprint ... [more ▼]

The electro-magnetic interaction between Io, Europa and Ganymede and the rotating plasma that surrounds Jupiter has a signature in the aurora of the planet. This signature, called the satellite footprint, takes the form of a series of spots located slightly downstream of the feet of the field lines passing through the moon under consideration. In the case of Io, these spots are also followed by an extended tail in the downstream direction relative to the plasma flow encountering the moon. A few examples of a tail for the Europa footprint have also been reported in the northern hemisphere. Here we present a simplified Alfvénic model for footprint tails and simulations of vertical brightness profiles for various electron distribution, which favour such a model over quasi-static models. We also report here additional cases of Europa footprint tails, in both hemispheres, even though such detections are rare and difficult. Furthermore, we show that the Ganymede footprint can also be followed by a similar tail. Finally, we present a case of a 320° long Io footprint tail, while other cases in similar configurations do not display such a length. [less ▲]

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See detailSimilarity of the Jovian satellite footprints: spots multiplicity and dynamics
Bonfond, Bertrand ULiege; Grodent, Denis ULiege; Badman, S. V. et al

in Icarus (2017), 292(2017), 208217

In the magnetospheres of Jupiter and Saturn, the intense interaction of the satellites Io, Europa, Ganymede and Enceladus with their surrounding plasma environment leaves a signature in the aurora of the ... [more ▼]

In the magnetospheres of Jupiter and Saturn, the intense interaction of the satellites Io, Europa, Ganymede and Enceladus with their surrounding plasma environment leaves a signature in the aurora of the planet. Called satellite footprints, these auroral features appear either as a single spot (Europa and Enceladus) or as multiple spots (Io and Ganymede). Moreover, they can be followed by extended trailing tails in the case of Io and Europa, while no tail has been reported for Ganymede and Enceladus, yet. Here we show that all Jovian footprints can be made of several spots. Furthermore, the footprints all experience brightness variations on timescale of 2-3 minutes. We also demonstrate that the satellite location relative to the plasma sheet is not the only driver for the footprint brightness, but that the plasma environment and the magnetic field strength also play a role. These new findings demonstrate that the Europa and Ganymede footprints are very similar to the Io footprint. As a consequence, the processes expected to take place at Io, such as the bi-directional electron acceleration by Alfvén waves or the partial reflection of these waves on plasma density gradients, can most likely be extended to the other footprints, suggesting that they are indeed universal processes. [less ▲]

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See detailNorth and South: Simultaneous observations of both Jovian poles from Juno and the Hubble Space Telescope
Bonfond, Bertrand ULiege; Gladstone, George R.; Grodent, Denis ULiege et al

Poster (2017, June 15)

On its elongated orbit, Juno flies over the poles of Jupiter every 53.5 days. The few hours before and after the perijove offer unique opportunities to observe the whole polar region from close distance ... [more ▼]

On its elongated orbit, Juno flies over the poles of Jupiter every 53.5 days. The few hours before and after the perijove offer unique opportunities to observe the whole polar region from close distance. However, Juno’s instruments can only observe one hemisphere at a time. Fortunately, the Hubble Space Telescope points its 2.4 m mirror toward the opposite hemisphere during some of these time intervals, providing truly simultaneous observations of both poles. We compare observations from Juno-UVS with Far-UV imaging sequences from the Hubble’s Space Telescope Imaging Spectrograph (STIS). Juno-UVS acquires spectrally resolved images of 17 ms exposure every 30 s Juno spin in the 70-205 nm wavelength range, while STIS can acquire about 270 consecutive 10 s images per HST orbit in the 130-160 nm range, but without any spectral resolution. Despite some differences, these datasets are similar enough in terms of spectral coverage, temporal and spatial resolution to allow direct comparisons. On Jupiter, the magnetic field is highly asymmetric and displays significant localized anomalies. Furthermore, most processes leading to auroral emissions depend on the magnetic field magnitude, either in the equatorial plane, in the acceleration regions, or in the upper atmosphere. Investigating morphological and brightness discrepancies between the two hemispheres provides precious clues on the current systems flowing in the magnetosphere and on the charged particles acceleration mechanisms. [less ▲]

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See detailMorphology of the UV aurorae Jupiter during Juno’s first perijove observations
Bonfond, Bertrand ULiege; Gladstone, G. R.; Grodent, Denis ULiege et al

in Geophysical Research Letters (2017)

On 27 August 2016, the NASA Juno spacecraft performed its first close-up observations of Jupiter during its perijove. Here we present the UV images and color ratio maps from the Juno-ultraviolet ... [more ▼]

On 27 August 2016, the NASA Juno spacecraft performed its first close-up observations of Jupiter during its perijove. Here we present the UV images and color ratio maps from the Juno-ultraviolet spectrometer UV imaging spectrograph acquired at that time. Data were acquired during four sequences (three in the north, one in the south) from 5:00 UT to 13:00 UT. From these observations, we produced complete maps of the Jovian aurorae, including the nightside. The sequence shows the development of intense outer emission outside the main oval, first in a localized region (255 ∘ –295 ∘ System III longitude) and then all around the pole, followed by a large nightside protrusion of auroral emissions from the main emission into the polar region. Some localized features show signs of differential drift with energy, typical of plasma injections in the middle magnetosphere. Finally, the color-ratio map in the north shows a well-defined area in the polar region possibly linked to the polar cap. [less ▲]

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See detailTransient brightening of Jupiter’s aurora observed by the Hisaki satellite and Hubble Space Telescope during approach phase of the Juno spacecraft
Kimura, Tomoki; Nichols, J.D.; Gray, R.L. et al

in Geophysical Research Letters (2017), 44

In early 2014, continuous monitoring with the Hisaki satellite discovered transient auroral emission at Jupiter during a period when the solar wind was relatively quiet for a few days. Simultaneous ... [more ▼]

In early 2014, continuous monitoring with the Hisaki satellite discovered transient auroral emission at Jupiter during a period when the solar wind was relatively quiet for a few days. Simultaneous imaging made by the Hubble Space Telescope (HST) suggested that the transient aurora is associated with a global magnetospheric disturbance that spans from the inner to outer magnetosphere. However, the temporal and spatial evolutions of the magnetospheric disturbance were not resolved because of the lack of continuous monitoring of the transient aurora simultaneously with the imaging. Here we report the coordinated observation of the aurora and plasma torus made by Hisaki and HST during the approach phase of the Juno spacecraft in mid‐2016. On day 142, Hisaki detected a transient aurora with a maximum total H2 emission power of ~8.5 TW. The simultaneous HST imaging was indicative of a large “dawn storm,” which is associated with tail reconnection, at the onset of the transient aurora. The outer emission, which is associated with hot plasma injection in the inner magnetosphere, followed the dawn storm within less than two Jupiter rotations. The monitoring of the torus with Hisaki indicated that the hot plasma population increased in the torus during the transient aurora. These results imply that the magnetospheric disturbance is initiated via the tail reconnection and rapidly expands toward the inner magnetosphere, followed by the hot plasma injection reaching the plasma torus. This corresponds to the radially inward transport of the plasma and/or energy from the outer to the inner magnetosphere. [less ▲]

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See detailHST observations of Jupiter's UV aurora during Juno's orbits PJ03, PJ04 and PJ05
Grodent, Denis ULiege; Gladstone, G Randall; Clarke, John T. et al

Poster (2017, April)

The intense ultraviolet auroral emissions of Jupiter are currently being monitored in the frame of a large Hubble Space Telescope (HST) program meant to support the NASA Juno prime mission. The present ... [more ▼]

The intense ultraviolet auroral emissions of Jupiter are currently being monitored in the frame of a large Hubble Space Telescope (HST) program meant to support the NASA Juno prime mission. The present study addresses the three first Juno orbits (PJ03, 04 and 05) during which HST obtained parallel observations. These three campaigns basically consist of a 2-week period bracketing the time of Juno’s closest approach of Jupiter (CA). At least one HST visit is scheduled every day during the week before and the week following CA. During the ∼12-hour period centered on CA and depending on observing constraints, several HST visits are programmed in order to obtain as many simultaneous observations with Juno-UVS as possible. In addition, at least one HST visit is obtained near Juno’s apojove, when UVS is continuously monitoring Jupiter’s global auroral power, without spatial resolution, for about 12 hours. We are using the Space Telescope Imaging Spectrograph (STIS) in time-tag mode in order to provide spatially resolved movies of Jupiter’s highly dynamic aurora with timescales ranging from seconds to several days. We discuss the preliminary exploitation of the HST data and present these results in such a way as to provide a global magnetospheric context for the different Juno instruments studying Jupiter’s magnetosphere, as well as for the numerous ground based and space based observatories participating to the Juno mission. [less ▲]

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See detailImplications of Juno energetic particle observations over Jupiter’s polar regions for understanding magnetosphere-ionosphere coupling at strongly magnetized planets
Mauk, Barry; Haggerty, Dennis; Paranicas, Christopher et al

Conference (2017, April)

Juno obtained low altitude space environment measurements over Jupiter’s poles on 27 August 2016 and then again on 11 December 2016. Particle distributions were observed over the poles within the downward ... [more ▼]

Juno obtained low altitude space environment measurements over Jupiter’s poles on 27 August 2016 and then again on 11 December 2016. Particle distributions were observed over the poles within the downward loss cones sufficient to power nominally observed auroral emissions and with the characteristic energies anticipated from remote spectroscopic ultra-violet auroral imaging. However, the character of the particle distributions apparently causing the most intense auroral emissions were very different from those that cause the most intense aurora at Earth and from those anticipated from prevailing models of magnetosphere-ionosphere coupling at Jupiter. The observations are highly suggestive of a predominance of a magnetic field-aligned stochastic acceleration of energetic auroral electrons rather than the more coherent acceleration processes anticipated. The Juno observations have similarities to observations observed at higher altitudes at Saturn by the Cassini mission suggesting that there may be some commonality between the magnetosphere-ionosphere couplings at these two giant planets. Here we present the Juno energetic particle observations, discuss their similarities and differences with published observations from Earth and Saturn, and deliberate on the implications of these finding for general understanding of magnetosphere-ionosphere coupling processes. [less ▲]

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See detailSynergistic observations of the giant planets with HST and JWST: Jupiter's auroral emissions
Grodent, Denis ULiege

Conference (2017, March 20)

The James Webb Space Telescope is perfectly suited to observe most Solar System objects, including the extended giant planets. Its high sensitivity, high spatial resolution, field of view, very high ... [more ▼]

The James Webb Space Telescope is perfectly suited to observe most Solar System objects, including the extended giant planets. Its high sensitivity, high spatial resolution, field of view, very high spectral resolution and wide spectral coverage all combine to make JWST a fantastic instrument that will result in significant advances and progress in most fields of Solar System exploration. Here, we focus on the case of Jupiter’s aurora for several reasons. 1) The auroral emissions on Jupiter are very intense, both in ultraviolet and in infrared. Each of these bandpasses is bringing complementary information on how Jupiter is interacting with its near and distant environment. 2) Even though Jupiter’s aurora appears to be responding to the conditions prevailing in the solar wind, contrary to the Earth it is a permanent emission that can also be observed on the sunlit side of the planet. 3) The NASA Juno mission is currently exploring the magnetosphere and the atmosphere of this planet with a suite of in situ and remote instruments, including an ultraviolet spectrograph (UVS) and an infrared imaging spectrograph (JIRAM). The Juno mission is gathering a broad scientific community that will foster the study of Jupiter’s system for several years. 4) A large HST program was allocated in support of the NASA Juno prime mission (GO-14634) and is currently providing us with regular movies of Jupiter’s ultraviolet aurora. They provide a global magnetospheric context for the different Juno instruments, as well as for the numerous ground based (infrared) and space based observatories participating to the Juno mission. 5) It is currently very difficult to plan truly simultaneous UV and IR observations, mainly because of the inherent limitations of Earth based infrared telescopes. As a result, comparisons of Jupiter’s auroral emissions rest on a very limited dataset. Nevertheless, they are suggesting similarities and discrepancies between IR and UV aurorae, the study of which would greatly benefit from synergistic observations with HST and JWST. 6) The case of Saturn’s aurora is as important, especially in view of the upcoming ‘Grand Finale’ of the Cassini mission, and all above arguments apply to Saturn as well. The case of Uranus and Neptune’s aurorae still belongs to the area of discovery and will take full advantage of JWST’s advanced capabilities. [less ▲]

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See detailMulti-instrument overview of the 1-hour pulsations in Saturn's magnetosphere
Palmaerts, Benjamin ULiege; Roussos, Elias; Radioti, Aikaterini ULiege et al

Conference (2017, March 16)

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See detailStagnation of Saturn's auroral emission at noon
Radioti, Aikaterini ULiege; Grodent, Denis ULiege; Gérard, Jean-Claude ULiege et al

in Journal of Geophysical Research. Space Physics (2017)

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See detailJupiter's magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits
Connerney, J. E. P.; Adriani, A.; Allegrini, F. et al

in Science (2017), 356(6340), 826--832

Jupiter is the largest and most massive planet in our solar system. NASA\textquoterights Juno spacecraft arrived at Jupiter on 4 July 2016 and made its first close pass on 27 August 2016. Bolton et al ... [more ▼]

Jupiter is the largest and most massive planet in our solar system. NASA\textquoterights Juno spacecraft arrived at Jupiter on 4 July 2016 and made its first close pass on 27 August 2016. Bolton et al. present results from Juno\textquoterights flight just above the cloud tops, including images of weather in the polar regions and measurements of the magnetic and gravitational fields. Juno also used microwaves to peer below the visible surface, spotting gas welling up from the deep interior. Connerney et al. measured Jupiter\textquoterights aurorae and plasma environment, both as Juno approached the planet and during its first close orbit.Science, this issue p. 821, p. 826The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral emissions from a vantage point above the poles. Juno\textquoterights capture orbit spanned the jovian magnetosphere from bow shock to the planet, providing magnetic field, charged particle, and wave phenomena context for Juno\textquoterights passage over the poles and traverse of Jupiter\textquoterights hazardous inner radiation belts. Juno\textquoterights energetic particle and plasma detectors measured electrons precipitating in the polar regions, exciting intense aurorae, observed simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited beneath the most intense parts of the radiation belts, passed about 4000 kilometers above the cloud tops at closest approach, well inside the jovian rings, and recorded the electrical signatures of high-velocity impacts with small particles as it traversed the equator. [less ▲]

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See detailResponse of Jupiter's auroras to conditions in the interplanetary medium as measured by the Hubble Space Telescope and Juno
Nichols, J. D.; Badman, S. V.; Bagenal, F. et al

in Geophysical Research Letters (2017)

We present the first comparison of Jupiter's auroral morphology with an extended, continuous and complete set of near-Jupiter interplanetary data, revealing the response of Jupiter's auroras to the ... [more ▼]

We present the first comparison of Jupiter's auroral morphology with an extended, continuous and complete set of near-Jupiter interplanetary data, revealing the response of Jupiter's auroras to the interplanetary conditions. We show that for ∼1-3 days following compression region onset the planet's main emission brightened. A duskside poleward region also brightened during compressions, as well as during shallow rarefaction conditions at the start of the program. The power emitted from the noon active region did not exhibit dependence on any interplanetary parameter, though the morphology typically differed between rarefactions and compressions. The auroras equatorward of the main emission brightened over ∼10 days following an interval of increased volcanic activity on Io. These results show that the dependence of Jupiter's magnetosphere and auroras on the interplanetary conditions are more diverse than previously thought. [less ▲]

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See detailJuno-UVS Approach Observations of Jupiter's Auroras
Gladstone, G. R.; Versteeg, M. H.; Greathouse, T. K. et al

in Geophysical Research Letters (2017)

Juno-UVS observations of Jupiter's aurora obtained during approach are presented. Prior to the bow-shock crossing on 24 June 2016, the Juno approach provided a rare opportunity to correlate local solar ... [more ▼]

Juno-UVS observations of Jupiter's aurora obtained during approach are presented. Prior to the bow-shock crossing on 24 June 2016, the Juno approach provided a rare opportunity to correlate local solar wind conditions with Jovian auroral emissions. Some of Jupiter's auroral emissions are expected to be controlled or modified by local solar wind conditions. Here we compare synoptic Juno-UVS observations of Jupiter's auroral emissions, acquired during 3-29 June 2016, with in situ solar wind observations, and related Jupiter observations from Earth. Four large auroral brightening events are evident in the synoptic data, in which the total emitted auroral power increases by a factor of 3-4 for a few hours. Only one of these brightening events correlates well with large transient increases in solar wind ram pressure. The brightening events which are not associated with the solar wind generally have a rise time of ~2 hours and a decay time of ~5 hours. [less ▲]

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See detailEnergy Dissipation in Saturn’s Magnetotail: A Comparative Magnetotail Approach
Yao, Zhonghua ULiege; Coates, Andrew; Ray, Licia et al

Poster (2016, December 16)

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See detailThe complex behavior of the satellite footprints at Jupiter: the result of universal processes?
Bonfond, Bertrand ULiege; Grodent, Denis ULiege; Badman, Sarah V. et al

Poster (2016, December 14)

At Jupiter, some auroral emissions are directly related to the electromagnetic interaction between the moons Io, Europa and Ganymede on one hand and the rapidly rotating magnetospheric plasma on the other ... [more ▼]

At Jupiter, some auroral emissions are directly related to the electromagnetic interaction between the moons Io, Europa and Ganymede on one hand and the rapidly rotating magnetospheric plasma on the other hand. Out of the three, the Io footprint is the brightest and the most studied. Present in each hemisphere, it is made of at least three different spots and an extended trailing tail. The variability of the brightness of the spots as well as their relative location has been tentatively explained with a combination of Alfvén waves’ partial reflections on density gradients and bi-directional electron acceleration at high latitude. Should this scenario be correct, then the other footprints should also show the same behavior. Here we show that all footprints are, at least occasionally, made of several spots and they all display a tail. We also show that these spots share many characteristics with those of the Io footprint (i.e. some significant variability on timescales of 2-3 minutes). Additionally, we present some Monte-Carlo simulations indicating that the tails are also due to Alfvén waves electron acceleration rather than quasi-static electron acceleration. Even if some details still need clarification, these observations strengthen the scenario proposed for the Io footprint and thus indicate that these processes are universal. In addition, we will present some early results from Juno-UVS concerning the location and morphology of the footprints during the first low-altitude observations of the polar aurorae. These observations, carried out in previously unexplored longitude ranges, should either confirm or contradict our understanding of the footprints. [less ▲]

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