References of "Hubert, Benoît"
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See detailMAVEN‐IUVS observations of the CO2+ UV doublet and CO Cameron bands in the Martian thermosphere: Aeronomy, seasonal and latitudinal distribution.
Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege; Ritter, Birgit ULiege et al

in Journal of Geophysical Research. Space Physics (2019)

We analyze two Martian years of dayglow measurements of the CO Cameron bands and the CO2+ ultraviolet doublet (UVD) at 298-299 nm with the Imaging UltraViolet Spectrograph on board the Maven orbiter. We ... [more ▼]

We analyze two Martian years of dayglow measurements of the CO Cameron bands and the CO2+ ultraviolet doublet (UVD) at 298-299 nm with the Imaging UltraViolet Spectrograph on board the Maven orbiter. We show that the altitude and the brightness of the two emissions peaks are strongly correlated, although data were collected over a wide range of latitudes and seasons. veraged limb profiles are presented and compared with numerical simulations based on updated calculations of the production of the CO (a3Π) and the CO2+ (B 2Σ) states. The model simulations use the solar flux directly measured on board MAVEN with the Extreme Ultraviolet Monitor (EUVM) and the neutral densities provided by the Mars Climate Database (MCD) version 5.3, adapted to the conditions of the observations. We show that the altitude and the shape of the sample limb profiles are well reproduced using the MCD neutral atmosphere. The simulated peak intensities of the CO2+ UVD and Cameron bands are in good agreement considering the uncertainties on the excitation cross sections and the calibration of the IUVS and EUVM instruments. No significant adjustment of the electron impact cross section on CO2 to produce the a3Π state is needed. Seasonal-latitudinal maps of the Cameron and UVD peak altitude observed during two Martian years show variations as large as 23 km. Model simulations of the amplitude of these changes are in fair agreement with the observations except during the southern summer dust period (Ls = 270°-320°) when the calculated rise of the dayglow layer is underestimated. [less ▲]

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See detailCharacteristics of Mars UV dayglow emissions from atomic oxygen at 130.4 and 135.6 nm: MAVEN/IUVS limb observations and modeling.
Ritter, Birgit ULiege; Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege et al

in Journal of Geophysical Research. Space Physics (2019)

We present an overview of two Martian years oxygen dayglow limb observations of the ultraviolet (UV) emissions at 130.4 nm and 135.6 nm. The data have been collected with the IUVS instrument on board the ... [more ▼]

We present an overview of two Martian years oxygen dayglow limb observations of the ultraviolet (UV) emissions at 130.4 nm and 135.6 nm. The data have been collected with the IUVS instrument on board the MAVEN spacecraft. We use solar flux measurements of EUVM on board MAVEN to remove the solar induced variation and show the variations of the maximum limb brightness and altitude with season, SZA and latitude, which reflects the strong variability of the Martian atmosphere. The 130.4 and 135.6 nm peak brightness and altitudes are strongly correlated and behave similarly. Both emissions are modeled for selected data using Monte Carlo codes to calculate emissions arising from electron impact on O and CO2. Additional radiative transfer calculations are made to analyze the optically thick 130.4 nm emission. Model atmospheres from the Mars Climate Database serve as input. Both simulated limb profiles are in good agreement with the observations despite some deviations. We furthermore show that the observed 130.4 nm brightness is dominated by resonance scattering of the solar multiplet with a contribution (15-20%) by electron impact on O. Over 95% of the excitation at 135.6 nm arises from electron impact on O. Simulations indicate that the limb brightness is dependent on the oxygen and CO2 content, while the peak emission altitude is mainly driven by the CO2 content because of absorption processes. We deduce [O]/[CO2] mixing ratios of 3.1% and 3.0% at 130 km for datasets collected at LS=350° in Martian years 32 and 33. [less ▲]

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See detailMartian dust storm impact on atmospheric H 2 O and D/H observed by ExoMars Trace Gas Orbiter
Vandaele, A. C.; Korablev, O.; Daerden, F. et al

in Nature (2019), 568

Global dust storms on Mars are rare 1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere 3 , primarily owing to ... [more ▼]

Global dust storms on Mars are rare 1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere 3 , primarily owing to solar heating of the dust 3 . In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars 4 . Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes 5,6 , as well as a decrease in the water column at low latitudes 7,8 . Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H 2 O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H 2 O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals 3 . The observed changes in H 2 O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere. © 2019, The Author(s), under exclusive licence to Springer Nature Limited. [less ▲]

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See detailNo detection of methane on Mars from early ExoMars Trace Gas Orbiter observations
Korablev, O.; Vandaele, A. C.; Montmessin, F. et al

in Nature (2019), 568

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today 1 . A number of different measurements of methane show evidence of ... [more ▼]

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today 1 . A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations 2–5 . These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere 6,7 , which—given methane’s lifetime of several centuries—predicts an even, well mixed distribution of methane 1,6,8 . Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections 2,4 . We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater 4 would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally. [less ▲]

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See detailLyman-α emission in the Martian proton aurora: Line profile and role of horizontal induced magnetic field
Gérard, Jean-Claude ULiege; Hubert, Benoît ULiege; Ritter, Birgit ULiege et al

in Icarus (2019), 321

Enhancements of the dayside Lyman-α emission by as much as ∼50% have been observed between 120 and 130 km in the lower Martian thermosphere from the Mars Express and MAVEN satellites, usually following ... [more ▼]

Enhancements of the dayside Lyman-α emission by as much as ∼50% have been observed between 120 and 130 km in the lower Martian thermosphere from the Mars Express and MAVEN satellites, usually following solar events such as coronal mass ejections and corotating interaction regions. They have been assumed to be optical signatures of proton aurora related to an increase in the solar wind proton flux hitting Mars’ bow shock. We present model simulations of the Lyman-α line profiles at different altitudes. These are partly guided by in situ measurements of the energy spectrum of protons in the magnetosheath region by the SWIA instrument on board the MAVEN spacecraft. We show that the auroral Lyman-α line profile is significantly broader than the hydrogen core of the planetary thermal H atom. Consequently, most of the auroral emission is produced outside the optically thick hydrogen core and creates the observed intensity enhancement. Simulations with incident energetic hydrogen atoms (H ENAs) produce a somewhat broader line profile. Monte Carlo calculations are made separately for incident solar wind protons and H ENAs produced by charge exchange in the hydrogen corona. Absorption by CO2 along the line of sight significantly affects the intensity distribution in the lower thermosphere. The calculated altitude of the peak emission for both types of incident particles is consistent with the observed characteristics of the proton aurora. We show that the presence of a horizontal induced magnetic field somewhat increases the line width and decreases the altitude of the emission peak as a consequence of the magnetic barrier effect on proton precipitation. The brightness of the Lyman-α emission also drops as a result of increased magnetic shielding of the protons. [less ▲]

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See detailStudy Of The Energy Budget During Isolated Auroral Substorms
Matar, Jessy ULiege; Hubert, Benoît ULiege; Yao, Zhonghua ULiege et al

Conference (2018, December 11)

The solar atmosphere permanently releases ionized material forming the solar wind, which carries the frozen-in interplanetary magnetic field (IMF). When the solar wind reaches the space environment of the ... [more ▼]

The solar atmosphere permanently releases ionized material forming the solar wind, which carries the frozen-in interplanetary magnetic field (IMF). When the solar wind reaches the space environment of the Earth, the IMF and the geomagnetic field can reconfigure their topology in the process of magnetic reconnection. Geomagnetic field lines are therefore opened by the interplanetary medium and dragged anti-sunward by the solar wind flow, which gives the Earth magnetosphere an elongated shape. This process results in the accumulation of open magnetic flux and energy in the geomagnetic tail. Eventually, when a significant amount of open magnetic flux has been accumulated and convected downtail, intense magnetic reconnection also occurs inside of the magnetotail, in the central plasma sheet, and the magnetic field lines return to a closed configuration, which reduces the amount of open magnetic flux. This flux closure process releases a significant amount of energy often estimated to be of the order 10^15 - 10^16 J stored in the tail, which can trigger auroral substorms, as a result of the solar wind - magnetosphere interaction. The released energy is distributed between the ionosphere, the ring current, the plasma sheet, and the formation of a plasmoid. In this work, we combine data from the ESA Cluster and the NASA IMAGE spacecraft to investigate three reconnection events occurring in 2001. We compare in-situ measurement from Cluster and auroral FUV imaging from IMAGE complemented by SuperDARN radar measurement of the ionospheric convection. The auroral hemispheric power is computed using the IMAGE-FUV images of the electron and proton aurora. The amount of open geomagnetic flux is estimated using the imaging of the proton aurora and the magnetic reconnection rates are derived from both missions and the SuperDARN data. We analyze the energy circulation by assessing the energy conversion and dissipation for each individual process during different substorm periods. We compare the hemispheric power, open magnetic flux and reconnection rates and search for a possible relation between them. [less ▲]

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See detailAnalytic methods for the Abel transform of exponential functions describing planetary and cometary atmospheres.
Hubert, Benoît ULiege; Munhoven, Guy ULiege; Opitom, Cyrielle et al

Poster (2018, December 11)

Remote sensing of planetary and cometary atmosphere is one of the most important source of data and knowledge of the gas layers surrounding the celestial objects of our solar system, including our own ... [more ▼]

Remote sensing of planetary and cometary atmosphere is one of the most important source of data and knowledge of the gas layers surrounding the celestial objects of our solar system, including our own planet. Most of the instruments used up to now and that will be used in a near future study the emission of radiations directly produced by the atmosphere. Under optically thin conditions, this observation method provides the local volume emission rate (VER) originating from the atmosphere, integrated along the full line of sight (l.o.s.) of the instrument. Under a spherical or cylindrical symmetry assumption, the l.o.s. integration of the VER takes the form of the Abel transform of the vertical VER profile. The simplest analytical functions representing VER profiles in real planetary and cometary atmosphere include an exponential function of the altitude (or radial distance), giving the isothermal profile for a planet and the Haser model for a coma. The Abel transform of these functions can be computed analytically using combinations of special functions. Retrieving the vertical (radial) profile of the VER does however require to invert the observed Abel transform to account for possible departures from these idealized analytical expressions, so that indefinite integrals defined from the Abel integral (which we will call indefinite Abel transforms) are needed (or numerical integrations need to be performed). In this study, we present a new method to produce a workable series development allowing accurate computation of the indefinite Abel transforms that appear in the study of optically thin emissions of planetary and cometary atmospheres. Indeed, taking the Taylor series development of the exponential function to reduce the problem to a series of indefinite Abel transforms of polynomial functions (which can be carried analytically) does not work. It leads to the computation of the difference of large, nearly equal numbers, which cannot be done accurately. Our method rather relies on an appropriate series development of the Jacobian of the Abel transform. We show that the computation can be done reliably up to near machine precision, and that accuracy control can be enforced for tailored applications. Possible applications are considered, that include the study of comas and of the upper atmosphere of Mars and the Earth [less ▲]

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See detailThe O(1S) 297.2 nm dayglow emission: a tracer of CO2 density variations in the Martian lower thermosphere
Gkouvelis, Leonardos ULiege; Gérard, Jean-Claude ULiege; Ritter, Birgit ULiege et al

in Journal of Geophysical Research. Planets (2018), 123

The O(1S) metastable atoms can radiatively relax by emitting airglow at 557.7 and 297.2 nm. The latter one has been observed with the Imaging Ultraviolet Spectrograph onboard the Mars Atmosphere and ... [more ▼]

The O(1S) metastable atoms can radiatively relax by emitting airglow at 557.7 and 297.2 nm. The latter one has been observed with the Imaging Ultraviolet Spectrograph onboard the Mars Atmosphere and Volatile Evolution Mars orbiter since 2014. Limb profiles of the 297.2-nm dayglow have been collected near periapsis with a spatial resolution of 5 km or less. They show a double-peak structure that was previously predicted but never observed during earlier Mars missions. The production of both 297.2-nm layers is dominated by photodissociation of CO2. Their altitude and brightness is variable with season and latitude, reflecting changes in the total column of CO2 present in the lower thermosphere. Since the lower emission peak near 85 km is solely produced by photodissociation, its peak is an indicator of the unit optical depth pressure level and the overlying CO2 column density. Its intensity is directly controlled by the Lyman-α solar flux reaching the Martian upper atmosphere. We take advantage of the Lyman-α flux measurements of the solar Extreme Ultraviolet Monitor instrument onboard Mars Atmosphere and Volatile Evolution to model the observed OI 297.2-nm limb profiles. For this, we combine photodissociation sources with chemical processes and photoelectron impact excitation. To determine the relative importance of the excitation processes, we apply the model to the atmospheric structure measured by the Viking 1 lander before applying it to a model atmosphere. We find very good agreement with the lower peak structure and intensity if the CO2 density provided by the Mars Climate Database is scaled down by a factor between 0.50 and 0.66. We also determine that the previously uncertain quantum yield for production of O(1S) atoms by photodissociation of CO2 at Lyman-α wavelength is about 8%. [less ▲]

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See detailCO2 variations in the Martian lower thermosphere from IUVS-MAVEN airglow observations.
Gkouvelis, Leonardos; Gérard, Jean-Claude ULiege; Ritter, Birgit ULiege et al

Conference (2018, September 17)

IUVS-MAVEN limb observations have been performed since 2014. We have analyzed almost four years of observations focusing on the O(1S) 297.2 nm dayglow emission line. We have developed an automatic ... [more ▼]

IUVS-MAVEN limb observations have been performed since 2014. We have analyzed almost four years of observations focusing on the O(1S) 297.2 nm dayglow emission line. We have developed an automatic methodology to retrieve the CO2 column densities near 80 km, a region difficult to probe by other techniques. We present nearly two Martian years of observations of pressure variations at different latitudes and comparisons withMCD model predictions. Generally, the best agreement is reached following scaling down of the MCD values from 0.3 to 0.8 to fit the observations. This result was previously expected on the basis of model comparisons with ultraviolet occultation measurements. [less ▲]

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See detailMars emissions from CO and CO2+: IUVS-MAVEN limb observations and model
Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege; Ritter, Birgit ULiege et al

Poster (2018, September 17)

The IUVS Ultraviolet spectrograph (McClintock et al. 2014) on board MAVEN has been collecting thousands of airglow (Jain et al. 2015) or auroral (Schneider et al., 2015) limb profiles in the range 120 to ... [more ▼]

The IUVS Ultraviolet spectrograph (McClintock et al. 2014) on board MAVEN has been collecting thousands of airglow (Jain et al. 2015) or auroral (Schneider et al., 2015) limb profiles in the range 120 to 340 nm (Fig. 1) since November 2014. We have analyzed more that three years of airglow observations and compared them to model simulations. MAVEN has been quasi-continuously collecting airglow observations since November 2014, covering more than 1.5 Martian year and various latitudes ranges. The main features are emissions from CO, CO2+, O, N2 and C. In this work, we compare the characteristics of the CO2+ ultraviolet doublet (UVD) limb profiles with model simulations. From this comparison, we derive the CO2 column density above the 120-130 km region. [less ▲]

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See detailA chemical survey of exoplanets with ARIEL
Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul et al

in Experimental Astronomy (2018)

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the ... [more ▼]

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet's birth, and evolution. ARIEL was conceived to observe a large number ( 1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25-7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H[SUB]2[/SUB]O, CO[SUB]2[/SUB], CH[SUB]4[/SUB] NH[SUB]3[/SUB], HCN, H[SUB]2[/SUB]S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed - using conservative estimates of mission performance and a full model of all significant noise sources in the measurement - using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL - in line with the stated mission objectives - will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives. [less ▲]

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See detailAtomic oxygen in the Martian thermosphere traced by the 130.4 and 135.6 nm emission lines with MAVEN/IUVS
Ritter, Birgit ULiege; Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege et al

Conference (2018, September)

We analyze limb observations of dayglow emissions from atomic oxygen in the upper Martian atmosphere. The data has been collected during the last almost four years by the Imaging Ultraviolet Spectrograph ... [more ▼]

We analyze limb observations of dayglow emissions from atomic oxygen in the upper Martian atmosphere. The data has been collected during the last almost four years by the Imaging Ultraviolet Spectrograph (IUVS) instrument on board the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) spacecraft. Mean profiles for specific solar longitude, latitude and solar zenith angle ranges are created. We then use atmospheres from the Mars General Circulation models and in situ solar flux data from the MAVEN Extreme Ultraviolet Monitor (EUVM) to perform Monte Carlo and radiative transfer modeling for comparison with the observations. In order to match the results and to eventually retrieve oxygen densities, scaling factors are applied to the GCM atmospheric densities. We will present preliminary results of this analysis [less ▲]

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See detailMonte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements
Bisikalo, D.V.; Shematovich, V.; Gérard, Jean-Claude ULiege et al

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

We present model results of the interaction of proton and hydrogen atom precipitation with the Martian atmosphere. We use a kinetic Monte Carlo model developed earlier for the analysis of the Analyzer of ... [more ▼]

We present model results of the interaction of proton and hydrogen atom precipitation with the Martian atmosphere. We use a kinetic Monte Carlo model developed earlier for the analysis of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) Mars Express data. With the availability of MarsAtmosphere and Volatile Evolution Mission in situ measurements, not only the flux of protons incident on theatmosphere but also their degradation along the orbit may now be described. The comparison of thesimulations with data collected with the Solar Wind Ion Analyzer shows that the Monte Carlo modelreproduces some of the measured features. The results of comparison between simulations andmeasurements of the proton fluxes at low altitudes make it possible to infer the efficiency of chargeexchange between solar wind and the extended hydrogen corona if the value of the magnetic field ismeasured simultaneously. We also find that the induced magnetic field plays a very important role in theformation of the backscattered flux and strongly controls its magnitude. At the same time, discrepancies between the modeled and the measured energy spectra of the backscattered protons are pointed out. We suggest that some of the physical processes controlling the upward flux are not fully understood or that the data processing of the measured backscattered proton flux should be improved [less ▲]

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See detailComparison between IUVS-MAVEN limb dayglow observations and modelling
Gkouvelis, Leonardos ULiege; Gérard, Jean-Claude ULiege; Ritter, Birgit ULiege et al

Poster (2018, May)

Limb observations of airglow emissions is a standard technique to study the altitude profiles of the chemical elements in the Martian atmosphere and its thermal structure. Several previous missions have ... [more ▼]

Limb observations of airglow emissions is a standard technique to study the altitude profiles of the chemical elements in the Martian atmosphere and its thermal structure. Several previous missions have performed observations in the past (Mariners, Mars express). Recently the IUVS Ultraviolet spectrograph (McClintock et al. 2014) on board MAVEN has been collecting thousands of airglow (Jain et al. 2015) or auroral (Schneider et al., 2015) limb prof iles in the range 120 to 340 nm. We have analysed more than three years of airglow observations and compared them to model simulations. The objective is to study the CO2, O, CO and other density prof iles as well as thermospheric temperatures. [less ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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