References of "Saglam, Adem"
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See detailThe distributions of the OH Meinel and O[SUB][/SUB](a[SUP]1[/SUP]Δ-X[SUP]3[/SUP]Σ) nightglow emissions in the Venus mesosphere based on VIRTIS observations
Gérard, Jean-Claude ULg; Soret, Lauriane ULg; Saglam, Adem ULg et al

in Advances in Space Research (2010), 45

O[SUB][/SUB](a[SUP]1[/SUP]Δ) and recently discovered OH Meinel nightglow emissions have been observed at the limb with the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS-M) instrument on board ... [more ▼]

O[SUB][/SUB](a[SUP]1[/SUP]Δ) and recently discovered OH Meinel nightglow emissions have been observed at the limb with the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS-M) instrument on board the Venus Express satellite. Hydroxyl bands belonging to Δv=1 sequence between 2.60and3.14μm and to Δv=2 sequence at 1.40-1.46μm have been unambiguously identified. In this study, we analyze the statistical distribution of the Δv=1 OH Meinel band sequence and the a[SUP]1[/SUP]Δ[SUB]g[/SUB]-X[SUP]3[/SUP]Σ (0-0) band of the O[SUB][/SUB] Infrared Atmospheric bands at 1.27 μm. We also present an analysis of the correlation between the two emissions. From a statistical point of view, we find that the limb intensity of both emissions reach their maximum value near the antisolar point, while they are significantly dimmer in the vicinity of the terminator. The average altitude of the limb emissions peaks are 95.3 ± 3 km and 96 ± 2.7 km, respectively for the OH Δv=1 sequence and O[SUB][/SUB](a[SUP]1[/SUP]Δ) emissions. The average intensities are 0.41 ± 0.37 MR and 28 ± 22 MR, respectively, corresponding to a mean ratio of about 70. The altitude of the OH nightglow layer is closely related to that of the O[SUB][/SUB](a[SUP]1[/SUP]Δ) emission and some level of co-variation of the maximum intensity along the line of sight is observed. It is suggested that the global subsolar to antisolar circulation plays a key in the control of both airglows by carrying oxygen atoms from the day to the night side of the planet. The O atoms recombine to produce O[SUB][/SUB](a[SUP]1[/SUP]Δ) molecules and they also act as precursors of ozone whose reaction with H produces excited hydroxyl. [less ▲]

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See detailConcurrent observations of the ultraviolet nitric oxide and infrared O[SUB]2[/SUB] nightglow emissions with Venus Express
Gérard, Jean-Claude ULg; Cox, Cédric ULg; Soret, Lauriane ULg et al

in Journal of Geophysical Research. Planets (2009), 114

Two prominent features of the Venus nightside airglow are the nitric oxide delta and gamma bands produced by radiative association of O and N atoms in the lower thermosphere and the O[SUB]2[/SUB] infrared ... [more ▼]

Two prominent features of the Venus nightside airglow are the nitric oxide delta and gamma bands produced by radiative association of O and N atoms in the lower thermosphere and the O[SUB]2[/SUB] infrared emission generated by three-body recombination of oxygen atoms in the upper mesosphere. The O[SUB]2[/SUB] airglow has been observed from the ground, during the Cassini flyby, and with VIRTIS on board Venus Express. It now appears that the global structure of the two emissions shows some similarities, but the statistical location of the region of strongest emission is not coincident. The Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) ultraviolet spectrograph has collected a large number of spectra of the Venus nitric oxide nightside airglow. Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) images have been obtained at the limb and in the nadir-viewing mode and have provided new information on the horizontal and vertical distribution of the emission. We present the first concurrent observations of the two emissions observed with Venus Express. We show that nadir observations generally indicate a low degree of correlation between the two emissions observed quasi-simultaneously at a common location. A statistical study of limb profiles indicates that the altitude and the brightness of the two airglow layers generally do not covary. We suggest that this lack of correlation is explained by the presence of strong horizontal winds in the mesosphere-thermosphere transition region. They carry the downflowing atoms over large distances in such a way that regions of enhanced NO emission generally do not coincide with zones of bright O[SUB]2[/SUB] airglow. [less ▲]

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See detailAtomic oxygen distribution in the Venus mesosphere from observations of O[SUB]2[/SUB] infrared airglow by VIRTIS-Venus Express
Gérard, Jean-Claude ULg; Saglam, Adem ULg; Piccioni, Giuseppe et al

in Icarus (2009), 199

This VIRTIS instrument on board Venus Express has collected spectrally resolved images of the Venus nightside limb that show the presence of the (0,0) band of the Deltag1-->Sigmag3 infrared atmospheric ... [more ▼]

This VIRTIS instrument on board Venus Express has collected spectrally resolved images of the Venus nightside limb that show the presence of the (0,0) band of the Deltag1-->Sigmag3 infrared atmospheric system of O[SUB]2[/SUB] at 1.27 mum. The emission is produced by three-body recombination of oxygen atoms created by photodissociation of CO[SUB]2[/SUB] on the dayside. It is consistently bright so that emission limb profiles can be extracted from the images. The vertical distribution of O[SUB]2[/SUB](Deltag1) may be derived following Abel inversion of the radiance limb profiles. Assuming photochemical equilibrium, it is combined with the CO[SUB]2[/SUB] vertical distribution to determine the atomic oxygen density. The uncertainties on the O density caused by the Abel inversion reach a few percent at the peak, increasing to about 50% near 120 km. We first analyze a case when the CO[SUB]2[/SUB] density was derived from a stellar occultation observed with the SPICAV spectrometer simultaneously with an image of the O[SUB]2[/SUB] limb airglow. In other cases, an average CO[SUB]2[/SUB] profile deduced from a series of ultraviolet stellar occultations is used to derive the O profile, leading to uncertainties on the O density less than 30%. It is found that the maximum O density is generally located between 94 and 115 km with a mean value of 104 km. It ranges from less than 1×10[SUP][/SUP] to about 5×10[SUP][/SUP] cm[SUP][/SUP] with a global mean of 2.2×10[SUP][/SUP] cm[SUP][/SUP]. These values are in reasonable agreement with the VIRA midnight oxygen profile. The vertical O distribution is generally in good agreement with the oxygen profile calculated with a one-dimensional chemical-diffusive model. No statistical latitudinal dependence of the altitude of the oxygen peak is observed, but the maximum O density tends to decrease with increasing northern latitudes. The latitudinal distribution at a given time exhibits large variations in the O density profile and its vertical structure. The vertical oxygen distribution frequently shows multiple peaks possibly caused by waves or variations in the structure of turbulent transport. It is concluded that the O[SUB]2[/SUB] infrared night airglow is a powerful tool to map the distribution of atomic oxygen in the mesosphere between 90 and 115 km and improve future Venus reference atmosphere models. [less ▲]

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See detailDistribution of the ultraviolet nitric oxide Martian night airglow: Observations from Mars Express and comparisons with a one-dimensional model
Cox, Cédric ULg; Saglam, Adem ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research (2008), 113

Limb observations with the SPICAM ultraviolet spectrometer on board the Mars Express orbiter revealed ultraviolet nightglow emission in the delta (190–240 nm) and gamma (225–270 nm) bands of nitric oxide ... [more ▼]

Limb observations with the SPICAM ultraviolet spectrometer on board the Mars Express orbiter revealed ultraviolet nightglow emission in the delta (190–240 nm) and gamma (225–270 nm) bands of nitric oxide. This emission arises from radiative recombination between O(3P) and N(4S) atoms that are produced on the day side and form excited NO molecules on the night side. In this study, we analyze the night limb observations obtained during the MEX mission. In particular, we describe the variability of the emission brightness and its peak altitude. We examine possible correlations with latitude, local time, magnetic field strength or solar activity. We show that the altitude of maximum emission varies between 55 and 92 km while the brightness is in the range 0.2 to 10.5 kR. The total vertical emission rate ranges from 8 to 237 R with an average value of 36 ± 52 R. The observed topside scale height of the emission profile varies between 3.8 and 11.0 km, with a mean value of 6 ± 1.7 km. We use a chemical-diffusive atmospheric model where the eddy coefficient, whose value in the Mars thermosphere is uncertain, is a free parameter to match the observed peak altitude of the emission. The model solves the continuity equation for O(3P), N(4S), and NO using a finite volume method on a one-dimensional grid. We find that the downward flux of N atoms at 100 km varies by two orders of magnitude, ranging from 10E7 to 10E9 atoms cm-2 s-1. [less ▲]

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See detailLimb observations of the ultraviolet nitric oxide nightglow with SPICAV on board Venus Express
Gérard, Jean-Claude ULg; Cox, Cédric ULg; Saglam, Adem ULg et al

in Journal of Geophysical Research. Planets (2008), 113

Limb observations of the spectrum of nightglow emission in the delta (190-240 nm) and gamma (225-270 nm) bands of nitric oxide have been made with the Spectroscopy for Investigation of Characteristics of ... [more ▼]

Limb observations of the spectrum of nightglow emission in the delta (190-240 nm) and gamma (225-270 nm) bands of nitric oxide have been made with the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) ultraviolet spectrometer on board Venus Express. These emissions arise from radiative recombination between O([SUP]3[/SUP]P) and N([SUP]4[/SUP]S) atoms that are produced on the dayside and recombine to form excited NO molecules on the nightside. No other emission feature has been identified. The mean altitude of the emission layer is located at 113 km, but it varies between 95 and 132 km. The mean brightness of the total NO emission at the limb is 32 kR, but it is highly variable with limb intensities as large as 440 kR observed at low latitude and values below 5 kR seen at northern midlatitudes. No systematic dependence of the brightness with latitude is observed, but the mean altitude of the emission maximum statistically drops with increasing latitude between 6° and 72°N. Typical observed limb profiles are compared with simulations based on a one-dimensional chemical-diffusive atmospheric model. From model fits to observed profiles, we find that the downward flux of N atoms at 130 km typically varies between 1 × 10[SUP]8[/SUP] to 4 × 10[SUP]9[/SUP] atoms cm[SUP]-2[/SUP] s[SUP]-1[/SUP]. Comparisons of observed airglow topside scale heights with modeled profiles smoothed by the instrumental field of view indicate that the observations are compatible with a downward flow of O and N atoms by molecular and turbulent transport above the peak of emission. The K coefficient deduced from comparisons to limb profiles is less than that determined from the observations made with the Pioneer Venus UV spectrometer at low latitude during periods of high solar activity. [less ▲]

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See detailDistribution of the O[SUB]2[/SUB] infrared nightglow observed with VIRTIS on board Venus Express
Gérard, Jean-Claude ULg; Saglam, Adem ULg; Piccioni, G. et al

in Geophysical Research Letters (2008), 35

We present characteristics of the statistical horizontal distribution of the O[SUB]2[/SUB] infrared nightglow over most of the southern hemisphere observed with the VIRTIS instrument over a period ... [more ▼]

We present characteristics of the statistical horizontal distribution of the O[SUB]2[/SUB] infrared nightglow over most of the southern hemisphere observed with the VIRTIS instrument over a period spanning nearly 11 months of low solar activity. We show that the distribution is inhomogeneous with the regions of brightest emission reaching ~3 MegaRayleighs (MR) located at low latitude near and dawnward of the midnight meridian. The hemispherically averaged nadir brightness is 1.3 MR, in very good agreement with earlier ground based observations. We show that the dayside supply of O atoms is sufficient to produce the observed global O[SUB]2[/SUB] nightglow if approximately 50% of the dayside O production is carried to the nightside by the subsolar to antisolar global circulation. Limb profiles observed at northern mid-latitudes exhibit large intensity variations over short time periods. Calculations with a one-dimensional chemical diffusive model produce an airglow peak at 96 km, in agreement with the limb observations. The atomic oxygen density derived from the best fits to O[SUB]2[/SUB] airglow limb profiles reaches a maximum of 1.8-3.5 × 10[SUP]11[/SUP] cm[SUP]-3[/SUP] at 104 km. [less ▲]

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See detailJupiter's changing auroral location
Grodent, Denis ULg; Gérard, Jean-Claude ULg; Radioti, Aikaterini ULg et al

in Journal of Geophysical Research (2008), 113(A1),

[1] We examine the case of significant latitudinal shifts of the Jovian northern auroral emissions appearing in a data set spanning nine years of observations with the Hubble Space Telescope in the far ... [more ▼]

[1] We examine the case of significant latitudinal shifts of the Jovian northern auroral emissions appearing in a data set spanning nine years of observations with the Hubble Space Telescope in the far ultraviolet. The extended data set makes it possible to compare the location of the main auroral emission with similar viewing geometries and satellite positions. The main auroral emission is assumed to originate from beyond the orbit of Ganymede (15 Jovian radii). At these distances, near corotation enforcement and transfer of momentum from Jupiter to the magnetospheric plasma is ensured by means of field aligned currents. The field aligned currents away from Jupiter are carried by downward energetic electrons loosing their energy to the polar atmosphere and giving rise to the main auroral emission. Analysis of the polar projected images shows that the latitudinal location of the main emission has changed by up to 3 degrees over long periods of time. It also shows that the footprint of Ganymede follows a similar trend. We have used the VIP4 magnetic field model to map the emission down to the equatorial plane. This mapping suggests that internal variations of the current sheet parameters might be used as an alternative or complementary explanation to the changing solar wind conditions at Jupiter to explain the observed shift of auroral latitudes. [less ▲]

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See detailVenus night airglow and implications for thermospheric composition and dynamics
Gérard, Jean-Claude ULg; Saglam, Adem ULg; Cox, Cédric ULg et al

Conference (2008)

Spatially resolved spectra of the NO delta and gamma ultraviolet bands have been obtained from 80 to 130 km on the Venus night side with the SPICAV instrument on board Venus Express. This NO airglow ... [more ▼]

Spatially resolved spectra of the NO delta and gamma ultraviolet bands have been obtained from 80 to 130 km on the Venus night side with the SPICAV instrument on board Venus Express. This NO airglow emission results from radiative recombination of oxygen and nitrogen atoms created on the dayside and transported by the subsolar to antisolar global circulation. Spectral images of the O2 (1 â delta g ) at 1.27 µm have also been made with the VIRTIS-M instrument both at nadir and at the limb. The O2 (1 â g ) emission is produced by three-body recombination of O atoms giving rise to an airglow layer near 96 km. The brightness of both emissions changes by over an order of magnitude. They also show variations in the altitude of the peak emission, with larger variability of the NO airglow. The characteristics of both airglows and their implications on global circulation and vertical transport on the nightside will be discussed. Concurrent observations of both limb airglows will be described. It will be shown that limb observations of the vertical and latitudinal distribution of the 1.27 µm emission make it possible to remotely determine the density of atomic oxygen in the upper mesosphere and improve current atmospheric models. One-dimensional models of the O and N distributions will be presented and global properties of the 1-D parameterization of turbulent transport will be discussed. [less ▲]

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See detailVenus Express observations of the Venus O2 and NO nightglow: distribution and constraints on vertical transport
Gérard, Jean-Claude ULg; Cox, Cédric ULg; Saglam, Adem ULg et al

Conference (2007, April)

Observations have been carried out in the infrared with VIRTIS and the ultraviolet with SPICAV to measure the distribution of the O2 (1 g) nightglow emission at 1.27 μm and the nitric oxide gamma and ... [more ▼]

Observations have been carried out in the infrared with VIRTIS and the ultraviolet with SPICAV to measure the distribution of the O2 (1 g) nightglow emission at 1.27 μm and the nitric oxide gamma and delta bands between 190 and 300 nm. These observations were collected in the tangent limb mode, which maximizes the time period spent by the line of sight through the airglow layer. The O2 (1 g) emission is excited by three-body recombination of O atoms produced on the day side and carried by the general thermospheric circulation to the night side. It is very variable in brightness and has a peak located between 95 and 100 km. The NO airglow is produced by radiative recombination of O atoms with N(4S) resulting from N2 photodissociation and reaches a maximum near 110 km.We combine the altitude and brightness information from the two emissions with simulations of a chemical diffusive model to determine the values of the vertical fluxes of O and N atoms and the strength of the eddy mixing which carries both types of atoms from above the turbopause into the recombination layer.We find that O fluxes on the order of a few 1012 atoms/cm2 s and N fluxes about 1010 atoms/cm2 s can reproduce the observations. The variability of the airglow emissions and the altitude-brightness relation will also be discussed and compared with model predictions. [less ▲]

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See detailMorphology of the ultraviolet Io footprint emission and its control by Io's location
Gérard, Jean-Claude ULg; Saglam, Adem ULg; Grodent, Denis ULg et al

in Journal of Geophysical Research. Space Physics (2006), 111(A4),

[1] A total of 74 images of the ultraviolet footprint of the Io flux tube (IFT) on Jupiter's upper atmosphere made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope have ... [more ▼]

[1] A total of 74 images of the ultraviolet footprint of the Io flux tube (IFT) on Jupiter's upper atmosphere made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope have been analyzed to characterize their location, morphology, and brightness distribution. The observations cover a wide range of central meridian Jovian longitudes and Io orbital positions and include north and south footprint emissions. Comparing the location of the IFT with that expected from the VIP4 model of the Jovian magnetic field, we find that the lead angle is generally not significantly different from zero in the System III longitude sector 125 degrees - 195 degrees. Instead, the lead angles reach about 8 degrees in the 50 degrees sector, coinciding with a region of possible magnetic anomaly. We observe that the brightness of the main footprint shows intrinsic intensity changes that appear to be controlled by the system III longitude of Io and its position above or below the center of the torus. The size of the primary spot magnetically maps into a region varying from 1 to over 10 Io diameters in Io's orbital plane. Multiple footprints are observed with varying brightness relative to the mean spot. The number of spots is found to increase as Io gets closer to the torus outer edge facing the spots. The separation between the first and second spots is typically 1 degrees-3 degrees of longitude and increases when Io is displaced from the torus center in the direction of the IFT signature. These features confirm that Alfven waves play an important role and generate energization of precipitated electrons. However, the observed variation of the FUV spot structure with Io's position appears inconsistent with models where reflections of Alfven wings occur between the torus boundary and Jupiter's ionosphere. Instead, the multiple spots apparently correspond to electron precipitation generated by Alfven waves reflected inside the plasma torus. [less ▲]

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See detailThe UV footprint emission of Io: morphology, brightness and control by Io
Gérard, Jean-Claude ULg; Saglam, Adem ULg; Grodent, Denis ULg et al

Conference (2005, August 01)

Emissions from the magnetic footprint of Io on Jupiter's upper atmosphere has been observed with the Space Telescope Imaging Spectrograph (STIS) since 1997 and more recently with the Advanced Camera for ... [more ▼]

Emissions from the magnetic footprint of Io on Jupiter's upper atmosphere has been observed with the Space Telescope Imaging Spectrograph (STIS) since 1997 and more recently with the Advanced Camera for Surveys (ACS) on board HST. The observations cover a wide range of central meridian Jovian longitudes and Io orbital positions. Most images also exhibit a long trailing tail associated with Io's wake plasma. The brightness of the footprint shows variations by over an order of magnitude and appears to be controlled by the distance from Jupiter's central meridian and the longitude of Io. Multiple footprints are also occasionally observed with varying relative brightness and mutual distance. These features apparently correspond to precipitation generated by the reflection of Alfvèn waves between Jupiter's ionosphere and the plasma torus. Observations collected in 2005 with ACS have provided high quality contrasted images that provide a direct indication of the altitude of the trailing tail and its orientation. [less ▲]

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See detailCharacteristics of Saturn's FUV aurora observed with the Space Telescope Imaging Spectrograph
Gérard, Jean-Claude ULg; Grodent, Denis ULg; Gustin, Jacques ULg et al

in Journal of Geophysical Research. Space Physics (2004), 109

We analyze a set of 15 FUV images obtained between October 1997 and January 2001 with the Hubble Space Telescope Imaging Spectrograph (STIS), providing a good view of Saturn's south auroral oval. It is ... [more ▼]

We analyze a set of 15 FUV images obtained between October 1997 and January 2001 with the Hubble Space Telescope Imaging Spectrograph (STIS), providing a good view of Saturn's south auroral oval. It is found that the morphology and brightness distribution of the aurora are dynamical with variations occurring on time scales of hours or less. The dayside main oval lies between 70° and 80° and is generally brighter and thinner in the morning than in the afternoon sector. The afternoon sector is characterized by more diffuse emission at higher latitudes. Weak emission is also observed poleward of the main oval up to the pole. A spot of enhanced auroral precipitation, tentatively identified as the optical signature of the dayside cusp, is sometimes observed poleward of the main oval in the noon sector, especially during periods when the morning arc is not fully developed. A spiral structure of the main oval with arcs at two latitudes in the same sector is occasionally observed. The brightness of the main oval ranges from below the STIS threshold of 1 kR of H[SUB]2[/SUB] emission up to ~75 kR. The total electron precipitated power varies between 20 and 140 GW, that is, comparable to the Earth's active aurora but about two orders of magnitude less than on Jupiter. An increasing trend of the precipitated power between the 1997 and the 2000-2001 observations may be related to the rising solar activity. Six spectra of the aurora in the noon sector covering the 1200-1700 Å range are dominated by emissions of the Lyman-alpha line and H[SUB]2[/SUB] Werner and Lyman bands. Their comparison with a synthetic model of electron excited H[SUB]2[/SUB] emissions indicates the presence of a weak absorption below 1400 Å by a column of methane ranging between 7 × 10[SUP]15[/SUP] and 2 × 10[SUP]16[/SUP] cm[SUP]-2[/SUP]. The corresponding energy of the primary auroral electrons is estimated 12 +/- 3 keV, using a low-latitude model atmosphere based on Voyager occultation measurements. The main oval brightness and the characteristic electron energy are generally consistent with recent models of Saturn's aurora, which colocate the main oval with the narrow upward field-aligned current system associated with departure from plasma corotation near the open-closed field line boundary. The latitude of the bright morning arc is somewhat lower than model predictions based on the plasma flow velocity measured by Voyager in the middle magnetosphere. [less ▲]

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