References of "Gérard, Jean-Claude"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailJupiter's aurora observed with HST during Juno orbits 3 to 7
Grodent, Denis ULiege; Bonfond, Bertrand ULiege; Yao, Zhonghua ULiege et al

in Journal of Geophysical Research. Space Physics (in press)

A large set of observations of Jupiter’s ultraviolet aurora was collected with the Hubble Space Telescope concurrently with the NASA-Juno mission, during an 8-month period, from 30 November 2016 to 18 ... [more ▼]

A large set of observations of Jupiter’s ultraviolet aurora was collected with the Hubble Space Telescope concurrently with the NASA-Juno mission, during an 8-month period, from 30 November 2016 to 18 July 2017. These Hubble observations cover Juno orbits 3 to 7 during which Juno in situ and remote sensing instruments, as well as other observatories, obtained a wealth of unprecedented information on Jupiter’s magnetosphere and the connection with its auroral ionosphere. Jupiter’s ultraviolet aurora is known to vary rapidly, with timescales ranging from seconds to one Jovian rotation. The main objective of the present study is to provide a simplified description of the global ultraviolet auroral morphology that can be used for comparison with other quantities, such as those obtained with Juno. This represents an entirely new approach from which logical connections between different morphologies may be inferred. For that purpose, we define three auroral subregions in which we evaluate the auroral emitted power as a function of time. In parallel, we define six auroral morphology families that allow us to quantify the variations of the spatial distribution of the auroral emission. These variations are associated with changes in the state of the Jovian magnetosphere, possibly influenced by Io and the Io plasma torus and by the conditions prevailing in the upstream interplanetary medium. This study shows that the auroral morphology evolved differently during the five ~2-week periods bracketing the times of Juno perijove (PJ03 to PJ07), suggesting that during these periods, the Jovian magnetosphere adopted various states. [less ▲]

Detailed reference viewed: 22 (4 ULiège)
Full Text
Peer Reviewed
See detailSimulating the detection of traveling ionospheric disturbances with the ICON mission
Wautelet, Gilles ULiege; Hubert, Benoît ULiege; Gérard, Jean-Claude ULiege

Conference (2018, April 11)

Traveling Ionospheric Disturbances (TIDs) are of the utmost importance in energy and momentum transfer from the lower atmosphere to the ionosphere. The upcoming NASA’s ICON mission will address these ... [more ▼]

Traveling Ionospheric Disturbances (TIDs) are of the utmost importance in energy and momentum transfer from the lower atmosphere to the ionosphere. The upcoming NASA’s ICON mission will address these topics by performing remote sensing of ion and electron density, velocity and temperature from the bottom of the ionosphere up to the altitude of the spacecraft. More precisely, the ICON Far UltraViolet (FUV) instrument will image the ionospheric limb in two wavelength channels: the first one is dedicated to atomic oxygen and detects its emission at 135.6 nm. The second one studies the N2 Lyman-Birge-Hopfield (LBH) band around 155 nm. With an inclination of 27° and a circular orbit at an altitude of 550 km, the ICON mission will focus on low-latitudes only. Using ICON/FUV data, TID detection can be performed following two different approaches. The first possibility makes use of raw measurements (level-1) of the limb, corresponding to the line-of-sight integrated values of the O+ ion density. The second option consists in analyzing vertical profiles of the O+ density (level-2 product) derived from the inverse Abel transform of level-1 data. In this study, we simulate integrated O+ emission based on a background ionosphere provided by IRI-2016 on which we superimpose a TID of known characteristics: wavelength, period and velocity. This work investigates the retrieval of TID characteristics with algorithms using either level-1 or level-2 data. Given that the assumed spherical symmetry used in inverse Abel transform is rarely met in low-latitude regions, TID detection using ICON/FUV could prove to be more reliable using line-of-sight integrated values directly provided by the imager rather than using the inverted O+ profiles. We investigate the advantages and drawbacks of both above-mentioned methods in detecting TIDs and untangle possible ambiguities that may arise from the spherical symmetry hypothesis. [less ▲]

Detailed reference viewed: 14 (1 ULiège)
See detailMars UV-Visible airglow observations and predictions for EXOMARS-TGO
Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege; Ritter, Birgit ULiege et al

Conference (2018, February)

Airglow observations have proven to be an efficient tool to probe composition and dynamics of planetary atmospheres. Several missions to Mars such as Mariners, Mars Express and MAVEN were equipped with ... [more ▼]

Airglow observations have proven to be an efficient tool to probe composition and dynamics of planetary atmospheres. Several missions to Mars such as Mariners, Mars Express and MAVEN were equipped with ultraviolet spectrometers that probed the distribution of airglow intensity features in the spectral range extending from 120 to 340 nm. They have provided a wealth of information on several emissions arising from O, C and N excited atoms or CO, CO2 + and N2 molecules. These, in turn, have been analyzed to provide thermospheric temperature, O densities, etc. [less ▲]

Detailed reference viewed: 17 (1 ULiège)
See detailAurorae on Mars
Ritter, Birgit ULiege; Gérard, Jean-Claude ULiege; Hubert, Benoît ULiege et al

Conference (2018, February)

Three kinds of UV aurora have been detected on Mars: the discrete aurora [1], the diffuse aurora [2], and the proton aurora [3]. The discrete and the diffuse aurora are seen on the Martian nightside and ... [more ▼]

Three kinds of UV aurora have been detected on Mars: the discrete aurora [1], the diffuse aurora [2], and the proton aurora [3]. The discrete and the diffuse aurora are seen on the Martian nightside and result from electron impact on the upper atmosphere. Figure 1 shows an electron excited auroral spectrum extended into the visible using laboratory measurements. The proton aurora is observed on the dayside and originates from precipitating protons. We present an overview of these aurorae, combining observations of the SPICAM ultraviolet spectrometer on board Mars Express and modeling results, giving an estimate of what we might be able to observe in the future with UVIS-NOMAD [4] on board Trace Gas Orbiter (TGO). [less ▲]

Detailed reference viewed: 13 (1 ULiège)
Full Text
Peer Reviewed
See detailEvidence for Auroral Emissions from Callisto's Footprint in HST UV Images
Bhattacharyya, Dolon; Clarke, John T.; Montgomery, Jordan et al

in Journal of Geophysical Research. Space Physics (2018), 123

Auroral emissions are expected from the footprint of Callisto in Jupiter's upper atmosphere owing to the known interaction of its atmosphere with Jupiter's magnetosphere, and from the observed auroral ... [more ▼]

Auroral emissions are expected from the footprint of Callisto in Jupiter's upper atmosphere owing to the known interaction of its atmosphere with Jupiter's magnetosphere, and from the observed auroral emissions from the footprints of the other three Galilean satellites. The mapping of Callisto along modeled magnetic field lines at Jupiter, however, places the expected footprint at the same latitude as the main auroral emissions, making it difficult to detect. We analyzed ultraviolet images of Jupiter taken using the HST/ACS instrument during a large observing campaign in 2007. Using a co-addition method similar to one used for Enceladus, we have identified a strong candidate for the footprint of Callisto on May 24, 2007. We tested this finding by applying the same co-addition technique to a nearly identical auroral configuration on May 30, 2007 when Callisto was behind Jupiter, not visible from Earth (CML = 22°; sub-Callisto system III longitude = 327°). By comparing the two co-added images, we can clearly see the presence of a strongly sub-corotating spot close to the expected Callisto footprint location on 24th May and its absence on 30th May. On the 24th Callisto was located in the current sheet. We also found a probable candidate on 26th May 2007 during which time Callisto was positioned below the current sheet. The measured location and intensity of the auroral emission provides important information about the interaction of Callisto with Jupiter's magnetic field, the corotating plasma, and the neutral and ionized state of the thin atmosphere of Callisto. [less ▲]

Detailed reference viewed: 30 (9 ULiège)
Full Text
Peer Reviewed
See detailObservations of the Proton Aurora on Mars With SPICAM on Board Mars Express
Ritter, Birgit ULiege; Gérard, Jean-Claude ULiege; Hubert, Benoît ULiege et al

in Geophysical Research Letters (2018), 45

We report observations of the proton aurora at Mars, obtained with the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet spectrograph on board Mars ... [more ▼]

We report observations of the proton aurora at Mars, obtained with the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet spectrograph on board Mars Express between 2004 and 2011. This is a third type of UV aurora that is discovered on Mars, in addition to the discrete and diffuse nightside aurora. It is observed only on the dayside as it is produced by the direct interaction of solar wind protons with the upper atmosphere. The auroral signature is an enhancement of the Lyman-α emission in the order of a few kilorayleighs. The proton aurora features peak emissions around 120 to 150 km. From the full SPICAM database, limb observations have been investigated and six clear cases have been found. We identify either coronal mass ejections and/or corotating interaction regions as triggers for each of these events. [less ▲]

Detailed reference viewed: 15 (1 ULiège)
Full Text
Peer Reviewed
See detailTemperature estimation from hydroxyl airglow emission in the Venus night side mesosphere
Migliorini, Alessandra; Snels, M.; Gérard, Jean-Claude ULiege et al

in Icarus (2018), 300

The temperature of the night side of Venus at about 95 km has been determined by using spectral features of the hydroxyl airglow emission around 3 μm, recorded from July 2006 to July 2008 by VIRTIS ... [more ▼]

The temperature of the night side of Venus at about 95 km has been determined by using spectral features of the hydroxyl airglow emission around 3 μm, recorded from July 2006 to July 2008 by VIRTIS onboard Venus Express. The retrieved temperatures vary from 145.5 to about 198.1 K with an average value of 176.3 ± 14.3 K and are in good agreement with previous ground-based and space observations. The variability with respect to latitude and local time has been studied, showing a minimum of temperature at equatorial latitudes, while temperature values increase toward mid latitudes with a local maximum at about 35°N. The present work provides an independent contribution to the temperature estimation in the transition region between the Venus upper mesosphere and the lower thermosphere, by using the OH emission as a thermometer, following the technique previously applied to the high-resolution O[SUB]2[/SUB](a[SUP]1[/SUP]Δ[SUB]g[/SUB]) airglow emissions observed from ground. [less ▲]

Detailed reference viewed: 25 (3 ULiège)
Full Text
Peer Reviewed
See detailThe Ionospheric Connection Explorer Mission: Mission Goals and Design
Immel, T. J.; England, S. L.; Mende, S. B. et al

in Space Science Reviews (2018), 214(13),

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space ... [more ▼]

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. However, it has been recognized in the 21st century that equally significant changes in ionospheric conditions are apparently associated with energy and momentum propagating upward from our own atmosphere. ICON's goal is to weigh the competing impacts of these two drivers as they influence our space environment. Here we describe the specific science objectives that address this goal, as well as the means by which they will be achieved. The instruments selected, the overall performance requirements of the science payload and the operational requirements are also described. ICON's development began in 2013 and the mission is on track for launch in 2018. ICON is developed and managed by the Space Sciences Laboratory at the University of California, Berkeley, with key contributions from several partner institutions. [less ▲]

Detailed reference viewed: 20 (3 ULiège)
Full Text
Peer Reviewed
See detailThe Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter
Korablev, O.; Montmessin, F.; Trokhimovskiy, A. et al

in Space Science Reviews (2018), 214

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared ... [more ▼]

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7-1.6 μm spectral range with a resolving power of ˜20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2-4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7-17 μm with apodized resolution varying from 0.2 to 1.3 cm[SUP]-1[/SUP]. TIRVIM is primarily dedicated to profiling temperature from the surface up to ˜60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described. [less ▲]

Detailed reference viewed: 24 (1 ULiège)
See detailJuno-UVS observation of the Io footprint: Influence of Io’s local environment and passage into eclipse on the strength of the interaction
Hue, Vincent; Gladstone, Randy; Greathouse, Thomas K et al

Poster (2017, December 13)

The Juno mission offers an unprecedented opportunity to study Jupiter, from its internal structure to its magnetospheric environment. Juno-UVS is a UV spectrograph with a bandpass of 70<λ<205 nm, built to ... [more ▼]

The Juno mission offers an unprecedented opportunity to study Jupiter, from its internal structure to its magnetospheric environment. Juno-UVS is a UV spectrograph with a bandpass of 70<λ<205 nm, built to characterize Jupiter’s UV emissions and provide remote sensing capacities for the onboard fields and particle instruments (MAG, Waves, JADE and JEDI). Juno’s orbit allows observing Jupiter from a unique vantage point above the poles. In particular, UVS has observed the instantaneous Io footprint and extended tail as Io enters into eclipse. This observation may better constrain whether the atmosphere of Io is sustained via volcanic activity or sublimation. Among other processes, the modulation of Io’s footprint brightness correlates to the strength of the interaction between the Io plasma torus and its ionosphere, which, in turn, is likely to be affected by the atmospheric collapse. UVS observed the Io footprint during two eclipses that occurred on PJ1 and PJ3, and one additional eclipse observation is planned during PJ9 (24 Oct. 2017). We present how the electrodynamic coupling between Io and Jupiter is influenced by changes in Io’s local environment, e.g. Io’s passage in and out of eclipse and Io’s traverse of the magnetodisc plasma sheet. [less ▲]

Detailed reference viewed: 24 (2 ULiège)
Full Text
See detailOverview of HST observa7ons of Jupiter’s ultraviolet aurora during Juno orbits 3 to 7
Grodent, Denis ULiege; Bonfond, Bertrand ULiege; Yao, Zhonghua ULiege et al

Conference (2017, December 12)

Jupiter’s permanent ultraviolet auroral emissions have been systematically monitored from Earth orbit with the Hubble Space Telescope (HST) during an 8-month period. The Girst part of this HST large ... [more ▼]

Jupiter’s permanent ultraviolet auroral emissions have been systematically monitored from Earth orbit with the Hubble Space Telescope (HST) during an 8-month period. The Girst part of this HST large program (GO-14634) was meant to support the NASA Juno prime mission during orbits PJ03 through PJ07. The HST program will resume in Feb 2018, in time for Juno’s PJ11 perijove, right after HST’s solar and lunar avoidance periods. HST observations are designed to provide a Jovian auroral activity background for all instruments on-board Juno and for the numerous ground based and space based observatories participating to the Juno mission. In particular, several HST visits were programmed in order to obtain as many simultaneous observations with Juno-UVS as possible, sometimes in the same hemisphere, sometimes in the opposite one. In addition, the timing of some HST visits was set to take advantage of Juno’s multiple crossings of the current sheet and of the magnetic Gield lines threading the auroral emissions. These observations are obtained with the Space Telescope Imaging Spectrograph (STIS) in time-tag mode, they consist in spatially resolved movies of Jupiter’s highly dynamic aurora with timescales ranging from seconds to several days. Here, we present an overview of the present -numerous- HST results. They demonstrate that while Jupiter is always showing the same basic auroral components, it is also displaying an ever-changing auroral landscape. The complexity of the auroral morphology is such that no two observations are alike. Still, in this apparent chaos some patterns emerge. This information is giving clues on magnetospheric processes at play at the local and global scales, the latter being only accessible to remote sensing instruments such as HST. [less ▲]

Detailed reference viewed: 23 (6 ULiège)
See detailAn overview of the first year of observations of Jupiter’s auroras by Juno-UVS with multi-wavelength comparisons
Gladstone, Randy; Greathouse, Thomas K; Versteeg, Maarten H et al

Conference (2017, December 12)

Juno’s Ultraviolet Spectrograph (Juno-UVS) has observed the Jovian aurora during eight perijove passes. UVS typically observes Jupiter for 10 hours centered on closest approach in a series of swaths, with ... [more ▼]

Juno’s Ultraviolet Spectrograph (Juno-UVS) has observed the Jovian aurora during eight perijove passes. UVS typically observes Jupiter for 10 hours centered on closest approach in a series of swaths, with one swath per Juno spin (~30s). During this period the spacecraft range to Jupiter’s aurora decreases from ~6 RJ to ~0.3 RJ (or less) in the north, and then reverses this in the south, so that spatial resolution changes dramatically. A scan mirror is used to target different features or raster across the entire auroral region. Juno-UVS observes a particular location for roughly 17 ms/swath, so the series of swaths provide snapshots of ultraviolet auroral brightness and color. A variety of forms and activity levels are represented in the Juno-UVS data–some have been described before with HST observations, but others are new. One interesting result is that the color ratio, often used as a proxy for energetic particle precipitation, may instead (in certain regions) indicate excitation of H2 by low-energy ionospheric electrons. Additional results from comparisons with simultaneous observations at x-ray, visible, and near-IR wavelengths will also be presented. [less ▲]

Detailed reference viewed: 18 (4 ULiège)
See detailA Study of Local Time Variations of Jupiter’s Ultraviolet Aurora using Juno-UVS
Greathouse, Thomas K; Gladstone, Randy; Versteeg, Maarten H et al

Conference (2017, December 12)

Juno’s Ultraviolet Spectrograph (Juno-UVS) offers unique views of Jupiter’s auroras never before obtained in the UV, observing at all local times (unlike HST observations, limited to the illuminated disk ... [more ▼]

Juno’s Ultraviolet Spectrograph (Juno-UVS) offers unique views of Jupiter’s auroras never before obtained in the UV, observing at all local times (unlike HST observations, limited to the illuminated disk). With Juno’s 2-rpm spin period, the UVS long slit rapidly scans across Jupiter observing narrow stripes or swaths of Jupiter’s poles, from 5 hours prior to perijove until 5 hours after perijove. By rotating a mirror interior to the instrument, UVS can view objects from 60 to 120 degrees off the spacecraft spin axis. This allows UVS to map out the entire auroral oval over multiple spins, even when Juno is very close to Jupiter. Using the first 8 perijove passes, we take a first look for local time effects in Jupiter’s northern and southern auroras. We focus on the strength of auroral oval emissions and polar emissions found poleward of the main oval. Some unique polar emissions of interest include newly discovered polar flare emissions that start off as small localized points of emission but quickly (10’s of sec) evolve into rings. These emissions evolve in such a way as to be reminiscent of raindrops striking a pond. [less ▲]

Detailed reference viewed: 26 (3 ULiège)
See detailCassini UVIS Observations of Saturn during the Grand Finale Orbits (Invited)
Pryor, Wayne R; Esposito, Larry W; West, Robert et al

Conference (2017, December 11)

In 2016 and 2017, the Cassini Saturn orbiter executed a final series of high inclination, low-periapsis orbits ideal for studies of Saturn's polar regions. The Cassini Ultraviolet Imaging Spectrograph ... [more ▼]

In 2016 and 2017, the Cassini Saturn orbiter executed a final series of high inclination, low-periapsis orbits ideal for studies of Saturn's polar regions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) obtained an extensive set of auroral images, some at the highest spatial resolution obtained during Cassini's long orbital mission (2004-2017). In some cases, two or three spacecraft slews at right angles to the long slit of the spectrograph were required to cover the entire auroral region to form auroral images. We will present selected images from this set showing narrow arcs of emission, more diffuse auroral emissions, multiple auroral arcs in a single image, discrete spots of emission, small scale vortices, large-scale spiral forms, and parallel linear features that appear to cross in places like twisted wires. Some shorter features are transverse to the main auroral arcs, like barbs on a wire. UVIS observations were in some cases simultaneous with auroral observations from the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) that will also be presented. UVIS polar images also contain spectral information suitable for studies of the auroral electron energy distribution. The long wavelength part of the UVIS polar images contains a signal from reflected sunlight containing absorption signatures of acetylene and other Saturn hydrocarbons. The hydrocarbon spatial distribution will also be examined. [less ▲]

Detailed reference viewed: 16 (1 ULiège)
See detailCassini UVIS Auroral Observations in 2016 and 2017
Pryor, Wayne R.; Esposito, Larry W.; Jouchoux, Alain et al

Poster (2017, December 06)

In 2016 and 2017, the Cassini Saturn orbiter executed a final series of high-inclination, low-periapsis orbits ideal for studies of Saturn's polar regions. The Cassini Ultraviolet Imaging Spectrograph ... [more ▼]

In 2016 and 2017, the Cassini Saturn orbiter executed a final series of high-inclination, low-periapsis orbits ideal for studies of Saturn's polar regions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) obtained an extensive set of auroral images, some at the highest spatial resolution obtained during Cassini's long orbital mission (2004-2017). In some cases, two or three spacecraft slews at right angles to the long slit of the spectrograph were required to cover the entire auroral region to form auroral images. We will present selected images from this set showing narrow arcs of emission, more diffuse auroral emissions, multiple auroral arcs in a single image, discrete spots of emission, small scale vortices, large-scale spiral forms, and parallel linear features that appear to cross in places like twisted wires. Some shorter features are transverse to the main auroral arcs, like barbs on a wire. UVIS observations were in some cases simultaneous with auroral observations from the Cassini Imaging Science Subsystem (ISS) the Cassini Visual and Infrared Mapping Spectrometer (VIMS), and the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) that will also be presented. [less ▲]

Detailed reference viewed: 15 (1 ULiège)
See detailThree types of aurora on Mars
Schneider, N.; Jain, S.; Deighan, J. et al

Conference (2017, December)

Observations by the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft have identified three types of aurora on Mars, each profoundly different from comparable types on Earth and other ... [more ▼]

Observations by the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft have identified three types of aurora on Mars, each profoundly different from comparable types on Earth and other planets. The primary reason for these differences is Mars’ lack of a global magnetic field and presence of localized crustral magnetic fields primarily in the southern hemisphere. IUVS is MAVEN’s remote sensing instrument for study of the Mars atmosphere. The instrument records spatially-resolved spectra in the far-UV (110-190 nm) and Mid-UV (180-340 nm). By virtue of an internal scan mirror and a gimbaled instrument platform, IUVS obtains useful spectra on Mars with >50% duty cycle, including Mars’ nightside. IUVS performs limb scans during the spacecraft periapse, and obtains UV images of the planet from reconstructed apoapse disk scans. Two types of aurora have been detected on Mars’ nightside by virtue of emissions requiring excitation by precipitating charged particles. The first type, discrete aurora, are localized near the boundary between open and closed crustal magnetic field lines. They generally appear at ~140 km altitude and the spectra correspond to moderate mean electron energy precipitation. These detections confirm the discovery of discrete discovered by Mars Express/SPICAM. IUVS has discovered a second type, diffuse aurora, which are widespread and potentially global. They occur as low as 70 km altitude; the spectra, depth of penetration and timing are consistent with the precipitation of relativistic electrons from the Sun. IUVS has discovered a third type, proton aurora, on Mars’ dayside as excess hydrogen Lyman alpha emission confined to Mars’ thermosphere. The intermittent excesses appear correlated with enhanced solar wind conditions. This type is the most common form of aurora detected by IUVS. IUVS results dispel a common misconception that aurora only occur near the edges of closed planetary magnetic field lines. While this is true for terrestrial aurora and discrete aurora on Mars, it is false for Mars’ diffuse and proton auroras. In this sense, Mars serves as the best archetype for auroral processes on unmagnetized planets in our solar system and beyond. [less ▲]

Detailed reference viewed: 26 (2 ULiège)
See detailMars, Venus, Earth and Titan UV Laboratory Aeronomy by Electron Impact
Ajello, J.; Malone, C.P.; Eastes, R. et al

Conference (2017, December)

The UV response of the Mars, Earth, Titan and Venus upper atmospheres to the solar radiation fields [solar wind and solar EUV] is the focus of the present generation of Mars, Earth, Titan and Venus ... [more ▼]

The UV response of the Mars, Earth, Titan and Venus upper atmospheres to the solar radiation fields [solar wind and solar EUV] is the focus of the present generation of Mars, Earth, Titan and Venus missions. These missions are Mars Express (MEX), the Mars Atmosphere and Volatile Evolution Mission (MAVEN), Cassini at Titan, Global-scale Observations of the Limb and Disk (GOLD) mission for Earth and Venus Express (VEX). Each spacecraft is equipped with a UV spectrometer that senses far ultraviolet (FUV) emissions from 110-190 nm, whose dayglow intensities are proportional to three quantities:1) particle (electron, ion) fluxes, 2) the altitude distribution of species in the ionosphere: CO, CO2, O, N2 at Venus and Mars and N2, O and O2 at Titan and Earth and 3) the emission cross section for the interaction process. UV spectroscopy provides a benchmark to the present space environment and indicates pathways for removing upper atmosphere gas (e.g., water escape from Mars and Earth) or N2 escape at Titan over eons. We present a UV laboratory program that utilizes an instrument, unique in the world, at the University of Colorado that can measure excitation mechanisms by particle (electron, ion) impact and the resulting emission cross sections that include processes occurring in a planetary atmosphere, particularly the optically forbidden emissions presented by the Cameron bands, the Lyman Birge Hopfield bands and the OI 135.6 nm multiplet. There are presently uncertainties by a factor of two in the existing measurements of the emission cross section, affecting modeling of electron transport. We have utilized the MAVEN Imaging Ultraviolet Spectrograph (IUVS) engineering model which operates at moderate spectral resolution (~0.5–1.0nm FWHM) to obtain the full vibrational spectra of the Cameron band system CO(a 3Π → X 1Σ+) from both CO direct excitation and CO2 dissociative excitation, and for the dipole-allowed Fourth Positive band system of CO, while for N2 we have studied molecular nitrogen (N2 LBH bands, a 1Πg → X 1Σg+). We have performed laboratory measurements using mono-energetic electrons in a large chamber to excite band systems by the same processes as occur at low densities in planetary atmospheres. We have ascertained vibrational structure and emission cross sections for the strongest band systems on solar system objects. [less ▲]

Detailed reference viewed: 15 (1 ULiège)
See detailH3+ Measurements in the Jovian Atmosphere with JIRAM/Juno
Migliorini, A.; Dinelli, M.L.; Altieri, F. et al

Poster (2017, December)

The NASA Juno mission has been investigating Jupiter’s atmosphere since August 2016, providing unprecedented insights into the giant planet. The Jupiter Infrared Auroral Mapper (JIRAM) experiment, on ... [more ▼]

The NASA Juno mission has been investigating Jupiter’s atmosphere since August 2016, providing unprecedented insights into the giant planet. The Jupiter Infrared Auroral Mapper (JIRAM) experiment, on board Juno, performed spectroscopic observations of the H3+ emissions both in the auroral regions (Dinelli et al., 2017; Adriani et al., 2017; Mura et al., 2017) and at mid latitudes. In the present work, we analyse the observations acquired by the JIRAM spectrometer during the first perijove passage on 26-27 August 2016, when the spacecraft was at about 500,000-1,200,000 km (7-17 RJ) from the planet. During a portion of the observations, the slit of the spectrometer sampled Jupiter’s limb in the latitude range from 30° to 60° in both hemispheres. The limb spectra show the typical features of the H3+ emission in the 3-4 μm spectral range, which are generally used to retrieve the H3+ concentration and temperature in the auroral region. In this work we employ above spectral region to provide new insight into the H3+ vertical distribution. The spatial resolution of the limb observations of Jupiter, ranging between 50 and 130 km, is favorable for investigating the vertical distribution of H3+. The vertical profiles of the H3+ limb intensity will be presented along with the preliminary results of the retrieval on H3+ vertical volume mixing ratio (VMR) height profiles, and comparison with predictions from the available atmospheric models of the planet. Possible variability of the altitude of the peak emission with respect to latitude and longitude will also be discussed. [less ▲]

Detailed reference viewed: 14 (1 ULiège)
See detailSeasonal transport in Mars' mesosphere-thermosphere revealed by NO nightglow
Stiepen, Arnaud ULiege; Royer; Schneider et al

Conference (2017, December)

Detailed reference viewed: 4 (1 ULiège)
Full Text
Peer Reviewed
See detailDawn Auroral Breakup at Saturn Initiated by Auroral Arcs: UVIS/Cassini Beginning of Grand Finale Phase
Radioti, Aikaterini ULiege; Grodent, Denis ULiege; Yao, Zhonghua ULiege et al

in Journal of Geophysical Research. Space Physics (2017)

Detailed reference viewed: 18 (8 ULiège)