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

Poster (2016, December 14)

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

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

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See detailJupiter’s auroras during the Juno approach phase as observed by the Hubble Space Telescope
Nichols, Jonathan D; Clarke, John T; Orton, Glennn S et al

Conference (2016, December 13)

We present movies of the Hubble Space Telescope (HST) observations of Jupiter’s FUV auroras observed during the Juno approach phase and first capture orbit, and compare with Juno observations of the ... [more ▼]

We present movies of the Hubble Space Telescope (HST) observations of Jupiter’s FUV auroras observed during the Juno approach phase and first capture orbit, and compare with Juno observations of the interplanetary medium near Jupiter and inside the magnetosphere. Jupiter’s FUV auroras indicate the nature of the dynamic processes occurring in Jupiter’s magnetosphere, and the approach phase provided a unique opportunity to obtain a full set of interplanetary data near to Jupiter at the time of a program of HST observations, along with the first simultaneous with Juno observations inside the magnetosphere. The overall goal was to determine the nature of the solar wind effect on Jupiter’s magnetosphere. HST observations were obtained with typically 1 orbit per day over three intervals: 16 May – 7 June, 22-30 June and 11-18 July, i.e. while Juno was in the solar wind, around the bow shock and magnetosphere crossings, and in the mid-latitude middle-outer magnetospheres. We show that these intervals are characterised by particularly dynamic polar auroras, and significant variations in the auroral power output caused by e.g. dawn storms, intense main emission and poleward forms. We compare the variation of these features with Juno observations of interplanetary compression regions and the magnetospheric environment during the intervals of these observations. [less ▲]

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See detailInitial observations of Jupiter’s aurora from Juno’s Ultraviolet Spectrograph (Juno-UVS)
Gladstone, Randy; Versteeg; Greathouse, Thomas et al

Conference (2016, December 13)

Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes important far-ultraviolet (FUV) emissions from the H2 bands and the H Lyman series which are produced in ... [more ▼]

Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes important far-ultraviolet (FUV) emissions from the H2 bands and the H Lyman series which are produced in Jupiter’s auroras, and also the absorption signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument telescope has a 4x4 cm2 input aperture and uses an off-axis parabolic primary mirror. A flat scan mirror situated near the entrance of the telescope is used to observe at up to ±30° perpendicular to the Juno spin plane. The light is focused onto the spectrograph entrance slit, which has a “dog-bone” shape, with three sections of 2.55°x0.2°, 2.0°x0.025°, and 2.55°x0.2° (as projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses FUV light onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode. The two mirrors and the grating are coated with MgF2 to improve FUV reflectivity. Tantalum surrounds the spectrograph assembly to shield the detector and its electronics from high-energy electrons. All other electronics are located in Juno’s spacecraft vault, including redundant low-voltage and high-voltage power supplies, command and data handling electronics, heater/actuator electronics, scan mirror electronics, and event processing electronics. The purpose of Juno-UVS is to remotely sense Jupiter’s auroral morphology and brightness to provide context for in situ measurements by Juno’s particle instruments. Here we present the first near-Jupiter results from the UVS instrument following measurements made during PJ1, Juno’s first perijove pass with its instruments powered on and taking data. [less ▲]

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See detailSearch for low-latitude atmospheric hydrocarbon variations on Jupiter from Juno-UVS measurements
Hue, Vincent; Gladstone, Randy; Greathouse, Thomas et al

Conference (2016, December 13)

The Juno mission offers the opportunity to study Jupiter, from its inner structure, up to its magnetospheric environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) occurred on ... [more ▼]

The Juno mission offers the opportunity to study Jupiter, from its inner structure, up to its magnetospheric environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) occurred on July 4th 2016. The nominal Juno mission involves 35 science polar-orbits of 14-days period, with perijove and apojove distances located at 0.06 Rj and 45 Rj, respectively. Juno-UVS is a UV spectrograph with a bandpass of 70<λ<205 nm, designed to characterize Jupiter UV emissions. One of the main additions of UVS compared to its predecessors (New Horizons- and Rosetta- Alice, LRO-LAMP) is a 2.54 mm tantalum shielding, to protect it from the harsh radiation environment at Jupiter, and a scan mirror, to allow for targeting specific auroral and atmospheric features at +/- 30˚ perpendicular to the Juno spin plane. It will provide new constraints on Jupiter’s auroral morphology, spectral features, and vertical structure, while providing remote-sensing constraints for the onboard waves and particle instruments. It will also be used to probe upper-atmospheric composition through absorption features found in the UV spectra using reflected solar UV radiation. For example, stratospheric hydrocarbons such as C2H2 and C2H6 are known to absorb significantly in the 150-180 nm regions, and these absorption features can be used to determine their abundances. We will present our search for the spectroscopic features seen in Jupiter’s reflected sunlight during the first perijove. [less ▲]

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See detailDynamics of the flares in the active polar region of Jupiter
Bonfond, Bertrand ULiege; Grodent, Denis ULiege; Badman, S. V. et al

in Geophysical Research Letters (2016)

The dusk-side of the polar region of Jupiter's UV aurorae, called the active region, sometimes exhibits quasi-periodic (QP) flares on time-scales of 2-3 minutes. Based on Hubble Space Telescope Far-UV ... [more ▼]

The dusk-side of the polar region of Jupiter's UV aurorae, called the active region, sometimes exhibits quasi-periodic (QP) flares on time-scales of 2-3 minutes. Based on Hubble Space Telescope Far-UV time-tag images, we show for the first time that the northern hemisphere also displays QP-flares. The area covered by these flares can reach up to 2.4 × 108 km2 (i.e. the whole active region), but often only involves an area an order of magnitude smaller. Using a magnetic field mapping model, we deduced that these areas correspond to the dayside outer magnetosphere. In our dataset, quasi-periodic features are only seen on half of the cases and even on a given observation, a region can be quiet for one half and blinking on the other half. Consecutive observations in the two hemispheres show that the brightening can occur in phase. Combined with the size and location of the flares, this behaviour suggests that the QP-flares most likely take place on closed magnetic field lines. [less ▲]

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See detailLimb observations with NOMAD (UV,visible, IR)
Gérard, Jean-Claude ULiege; Soret, Lauriane ULiege

Scientific conference (2016, December)

We examine the possibilities and conditions to observe the Mars airglow and aurora (dayside and nightside) at the limb with the NOMAD instrument on board the TGO/EXOMARS orbiter.

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See detailFirst Hubble Space Telescope Movies of Jupiter’s Ultraviolet Aurora During the NASA Juno Prime Mission
Grodent, Denis ULiege; Gladstone, G. Randall; Clarke, John T. et al

Poster (2016, December)

The primary goal of this HST campaign is to complement Juno-UVS (Ultraviolet Spectrograph) observations. This complementarity is four-fold as HST observes Jupiter’s aurora when: 1) Juno-UVS is turned off ... [more ▼]

The primary goal of this HST campaign is to complement Juno-UVS (Ultraviolet Spectrograph) observations. This complementarity is four-fold as HST observes Jupiter’s aurora when: 1) Juno-UVS is turned off, that is about 98% of Juno’s 14-day orbit, and Juno’s in situ instruments are in operation. 2) Juno-UVS is operating, but observes the opposite hemisphere of Jupiter. 3) UVS is on in the same hemisphere, but too close to Jupiter to have a global, contextual, view of the aurora and/or UVS is affected by the noise induced by Jupiter’s radiation belts. 4) Juno is too far from Jupiter to get a detailed view of the aurora. In addition, HST will observe the auroral and airglow emissions of the Galilean moons Io, Ganymede and Europa, when UVS is measuring their auroral footprints in Jupiter’s ionosphere. During this campaign, HST is obtaining 45-min STIS time-tag images -movies- of both hemispheres of Jupiter and STIS/COS spectra of Jupiter's moons. These observations are taking place during 4 sequences of Juno's orbit (Figure: typical orbit in magnetic coordinates): 1) Perijove segment: a 6-hour sequence bracketing the time of Juno's closest approach of Jupiter. 2) Crossing segments: few hours periods during which Juno is crossing the magnetic equator of Jupiter and in situ instruments are observing the plasma sheet particles. 3) Perijove +/- 1 Jovian rotation (or more), to provide a context for the auroral activity before and after perijove. 4) Apojove segment: a 12-hour period bracketing the time when Juno is farthest from Jupiter and Juno-UVS is continuously monitoring the global auroral UV power of Jupiter. During Juno orbit PJ5, between 28 Nov. and 07 Dec. 2016, HST obtains 9 STIS movies: 3 movies of the northern aurora near perijove, 1 movie (north) one Jovian rotation before and 2 movies (south- north) one and two Jovian rotations after perijove, 2 movies (north) during two close CS crossings, and 1 movie near apojove. These movies will be commented during this presentation. [less ▲]

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See detailThe Martian diffuse aurora: Monte Carlo simulations and comparison with IUVS-MAVEN observations
Gérard, Jean-Claude ULiege; Soret, Lauriane ULiege; Schneider, N. et al

Conference (2016, December)

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar ... [more ▼]

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar activity on several occasions with the IUVS on board the MAVEN spacecraft. We describe the results of Monte Carlo simulations of the production of several ultraviolet and visible auroral emissions for initial electron energies from 0.1 to 200 keV. These include the CO2+ ultraviolet doublet (UVD) at 288.3 and 289.6 nm and the Fox–Duffendack–Barker (FDB) bands, CO Cameron and Fourth Positive bands, OI 130.4 and 297.2 nm and CI 156.1 nm and 165.7 nm multiplets. We calculate the nadir and limb intensities of several of these emissions for a unit precipitated energy flux. Our results indicate that electrons in the range 100-200 keV produce maximum CO2+ UVD emission near 75 km. We combine SWEA and SEP electron energy spectra measured during diffuse aurora to calculate the volume emission rates and compare with IUVS observations of the emission limb profiles. The strongest predicted emissions are the CO2+ FDB, UVD and the CO Cameron bands. The metastable a 3Π state which radiates the Cameron bands is deactivated by collisions below ~110 km. As a consequence, we show that the CO2+ UVD to the Cameron bands ratio increases at low altitude in the energetic diffuse aurora. [less ▲]

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See detailPulsations of the polar cusp aurora at Saturn
Palmaerts, Benjamin ULiege; Radioti, Aikaterini ULiege; Roussos, E. et al

in Journal of Geophysical Research. Space Physics (2016), 121

The magnetospheric cusp is a region connecting the interplanetary environment to the ionosphere and enabling solar wind particles to reach the ionosphere. We report the detection of several isolated high ... [more ▼]

The magnetospheric cusp is a region connecting the interplanetary environment to the ionosphere and enabling solar wind particles to reach the ionosphere. We report the detection of several isolated high-latitude auroral emissions with the Ultraviolet Imaging Spectrograph of the Cassini spacecraft. We suggest that these auroral spots, located in the dawn-to-noon sector and poleward of the main emission, are the ionospheric signatures of the magnetospheric cusp, in agreement with some previous observations with the Hubble Space Telescope. The high-latitude cusp auroral signature has been associated with high-latitude lobe reconnection in the presence of a southward interplanetary magnetic field. The occurrence rate of the polar cusp aurora suggests that lobe reconnection is frequent at Saturn. Several auroral imaging sequences reveal a quasiperiodic brightening of the polar cusp aurora with a period in the range of 60 to 70 min. Similar pulsations in the energetic electron fluxes and in the azimuthal component of the magnetic field are simultaneously observed by Cassini instruments, suggesting the presence of field-aligned currents. Pulsed dayside magnetopause reconnection is a likely common triggering process for the cusp auroral brightenings at Saturn and the quasiperiodic pulsations in the high-latitude energetic electron fluxes. [less ▲]

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See detailNitric Oxide nightglow from IUVS disk images
Stiepen, Arnaud ULiege; Schneider; Gonzàlez-Galindo et al

Conference (2016, November)

Detailed reference viewed: 15 (1 ULiège)
See detailJuno Ultraviolet Spectrograph (Juno-UVS) Observations of Jupiter during Approach
Gladstone, G. Randall; Versteeg, Maarten; Greathouse, Thomas K. et al

Conference (2016, October)

We present the initial results from Juno Ultraviolet Spectrograph (Juno-UVS) observations of Jupiter obtained during approach in June 2016. Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 ... [more ▼]

We present the initial results from Juno Ultraviolet Spectrograph (Juno-UVS) observations of Jupiter obtained during approach in June 2016. Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes all important ultraviolet (UV) emissions from the H<SUB>2</SUB> bands and the H Lyman series which are produced in Jupiter's auroras, and also the absorption signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument telescope has a 4 x 4 cm<SUP>2</SUP> input aperture and uses an off-axis parabolic primary mirror. A flat scan mirror situated near the entrance of the telescope is used to observe at up to ±30° perpendicular to the Juno spin plane. The light is focused onto the spectrograph entrance slit, which has a "dog-bone" shape 7.2° long, in three sections of 0.2°, 0.025°, and 0.2° width (as projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses UV light onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode. Tantalum surrounds the spectrograph assembly to shield the detector and its electronics from high-energy electrons. All other electronics are located in Juno's spacecraft vault, including redundant low-voltage and high-voltage power supplies, command and data handling electronics, heater/actuator electronics, scan mirror electronics, and event processing electronics. The purpose of Juno-UVS is to remotely sense Jupiter's auroral morphology and brightness to provide context for in situ measurements by Juno's particle instruments. Prior to Jupiter Orbit Insertion (JOI) on July 5, Juno approach observations provide a rare opportunity to correlate local solar wind conditions with Jovian auroral emissions. Some of Jupiter's auroral emissions (e.g., polar emissions) may be controlled or at least affected by the solar wind. Here we compare synoptic Juno-UVS observations of Jupiter's auroral emissions (~40 minutes per hour, acquired during 2016 June 3-30) with in situ solar wind observations, as well as related Jupiter observations obtained from Earth. [less ▲]

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See detailCassini UVIS Auroral Observations in 2016
Pryor, Wayne R.; Jouchoux, Alain; Esposito, Larry et al

Conference (2016, October)

In June of 2016, the Cassini Saturn orbiter began a series of high inclination orbits that will continue until September 2017 when the mission ends as Cassini enters the Saturn atmosphere. These orbits ... [more ▼]

In June of 2016, the Cassini Saturn orbiter began a series of high inclination orbits that will continue until September 2017 when the mission ends as Cassini enters the Saturn atmosphere. These orbits present excellent views of Saturn's polar regions suitable for auroral imaging at the closest distances to date, with the additional prospect of simultaneous particle and fields measurements within the sources of Saturn Kilometric Radiation (SKR) associated with ultraviolet auroral emissions and/or acceleration regions likely coinciding with them. We will present new Cassini Ultraviolet Imaging Spectrograph (UVIS) auroral images, spectra and movies obtained during the summer and fall of 2016 and put them in the context of auroral data collected since Cassini orbit insertion in 2004. Included in the new data will be UVIS south polar observations obtained simultaneously with Hubble Space Telescope observations of the north polar region on June 29, 2016 and August 19, 2016. [less ▲]

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See detailUV emissions of Jupiter: exploration of the high-latitude regions through the UV spectrograph on NASA's Juno mission
Hue, Vincent; Gladstone, G. Randall; Versteeg, Maarten et al

Conference (2016, October)

The Juno mission offers the opportunity to study Jupiter, from its inner structure to its magnetospheric environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) planned for ... [more ▼]

The Juno mission offers the opportunity to study Jupiter, from its inner structure to its magnetospheric environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) planned for July 4th 2016, will place Juno in a 53.5 days capture orbit. A period reduction maneuver will be performed two orbits later to place Juno into 14-days elliptical orbits for the duration of the nominal mission, which includes 36 orbits. Juno-UVS is a UV spectrograph with a bandpass of 70 ≤ λ ≤ 205 nm, designed to characterize Jupiter UV emissions. One of the main additions of UVS compared to its predecessors is a 2.54 mm tantalum shielding, to protect it from the harsh radiation environment at Jupiter, and a scan mirror, to allow for targeting specific auroral regions during perijove passes. The scan mirror is located at the front end of the instrument and will be used to look at +/- 30° perpendicular to the Juno spin plane. The entrance slit of UVS has a dog-bone shape composed by three sections with field of views of 0.2°x2.5°, 0.025°x2.0° and 0.2°x2.5°, as projected onto the sky. It will provide new constraints on Jupiter’s auroral nightside morphology and spectral features as well as the vertical structure of these emissions. It will bring remote-sensing constraints for the onboard waves and particle instruments (JADE, JEDI, Waves and MAG). The ability to change the pointing will allow relating the observed UV brightness of the regions magnetically connected to where Juno flies with the particles and waves measurements. We will discuss the planned observations and scientific targets for the nominal mission orbital sequence, which will consist of three UV datasets per orbit. We will present the results from the first orbit. As Juno orbit evolves during the mission, we will also present how these objectives evolve over time. [less ▲]

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See detailUVS – JIRAM image comparison during Juno PJ1
Gérard, Jean-Claude ULiege; Bonfond, Bertrand ULiege; Grodent, Denis ULiege et al

Conference (2016, September 27)

We present a comparison between images collected in the infrared and ultraviolet by the JIRAM and IUVS spectral imagers on board the Juno orbiter. Similarities and differences are pointed out.

Detailed reference viewed: 20 (2 ULiège)
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See detailNitric Oxide nightglow as a tracer of inter-hemispheric circulation: Detailed comparison with the LMD-GCM
Stiepen, Arnaud ULiege; IUVS team; Gonzales-Galindo et al

Conference (2016, September)

Detailed reference viewed: 13 (2 ULiège)
See detailAuroral evidence of flux tube blockage near noon at Saturn’s magnetosphere
Radioti, Aikaterini ULiege; Grodent, Denis ULiege; Gérard, Jean-Claude ULiege et al

Poster (2016, April)

We discuss plasma circulation in Saturn’s magnetosphere on the basis of auroral observations. Auroral enhance- ments in the dawn region are suggested to be related to intense field-aligned currents ... [more ▼]

We discuss plasma circulation in Saturn’s magnetosphere on the basis of auroral observations. Auroral enhance- ments in the dawn region are suggested to be related to intense field-aligned currents generated by hot tenuous plasma carried inward in fast moving flux tubes as they return from tail reconnection site to the dayside. Here we demonstrate that the rotation of the auroral emission in the dawn sector is occasionally (in half of the auroral sequences examined) slowed down and blocked near noon for a couple of hours. When the blockage is prominent and persistent, we observe auroral evidence of dayside magnetopause reconnection and openign of flux. A pos- sible interpretation for our observations could be that depleted flux tubes at large radial distances, which rotate around Saturn are blocked in the prenoon sector between the heavy Vasyliunas cycle flux tubes on one side, and the magnetopause on the other side. These depleted flux tubes have to move above or below the current sheet to pass this blockage. The blockage of the field lines close to midday will bend them and trigger reconnection, which opens the flux tubes and allows for solar wind material to enter the magnetosphere. Secondly, we suggest that the circulation pattern of depleted flux tubes close to noon in Saturn’s magnetosphere alternates between a ’blocked’ and ’unblocked’ state, depending on the solar wind dynamic pressure and the internal processes. [less ▲]

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See detailThe O2(a1Δ) Venus nightglow intensity: internal versus solar activity control
Soret, Lauriane ULiege; Gérard, Jean-Claude ULiege

Conference (2016, April)

Introduction: The O2(a1Δg) Venus nightglow emission at 1.27 μm occurs in the atmospheric region governed by the subsolar to antisolar circulation. Several studies showed that the intensity of this ... [more ▼]

Introduction: The O2(a1Δg) Venus nightglow emission at 1.27 μm occurs in the atmospheric region governed by the subsolar to antisolar circulation. Several studies showed that the intensity of this emission is highly variable on a timescale of hours. Here, we study the possible correlation between the solar flux and the O2 infrared emission using VIRTIS-VEx spectral images at 1.27 μm that has been predicted to exist by theVTGCM model calculations by Bougher and Borucki(1994). VIRTIS data: Using the entire VIRTIS-M-IR nadir database, Soret et al. (2014) generated seven statistical maps of the O2(a1Δg) emission, each containing 500 observations. The purpose was to analyze the location of the brightest spot of the emission and its variations over time. Here, we analyze the intensity of the emission over time. Several methods have been used by Soret et al., (2015) to do so (evolution of the emission maximum, evolution of the average intensity, …) Here we present the results of a new analysis using a masking technique to calculate the time evolution of the nightglow brightness. However, none of them follow the same trend over time. Solar flux data: We now focus on solar flux variations in the time of VIRTIS observations (between May 2006 and October 2008), which were collected during a deep solar minimum. We use the SOHO-CELIAS/SEM (Judge et al., 1998) EUV daily average full solar disk fluxes at 1 AU between 0.1 and 50 nm available from the Space Sciences Center of the University of Southern California. EUV0.1–50 daily average fluxes decrease from 2.6 in May 2006 to 1.9 in October 2008 at the Earth. These values have been adapted to Venus by taking into account the distance from the Sun to the planet, but also the shift in date, considering the difference in solar longitude of the two planets. Values at Venus vary from 4.4 to 3.4, which corresponds to a decrease of 10.4% of the solar flux at Venus compared to a complete solar cycle (ranging from 13.5 to 3.9) Comparison of VIRTIS and SEM datasets: The linear correlation coefficient between the solar flux and the intensity peak is found to be 0.62, which expresses the global decreasing trend for both quantities. This coefficient is not higher because internal variations of the two studied variables do not occur simultaneously. More significantly, the correlation coefficient between the solar flux and the averaged intensities is found to be 0.35, meaning that no relation-ship exists between the O2(a1Δg) brightness and the solar activity. Conclusions: Contrary to the VTGCM calculations, we do not observe here a correlation between the O2(a1Δg) brightness and the solar flux. However, VIRTIS data were acquired during a deep solar minimum and, more importantly, during a relatively stable phase of the solar activity. A high level of variability of the O2(a1Δg) emission has been detected in the same dataset from day to day though (Hueso et al., 2008; Soret et al., 2014). It thus appears that the variability is more controlled by internal than external conditions: transport appears to play a major role in the nightglow emissions than the solar activity eventually does. This conclusion is at least valid for solar minimum conditions. A space mission with global imaging capabilities over an entire solar cycle would definitely allow determining the relative role played by solar activity and internal factors. [less ▲]

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See detailAnalytical estimate for low-altitude ENA emissivity
Goldstein, J.; Bisikalo, D.V.; Shematovich, V.I. et al

in Journal of Geophysical Research. Space Physics (2016), 121(2), 1167-1191

We formulate the first analytical model for energetic neutral atom (ENA) emissivity that partially corrects for the global viewing geometry dependence of low-altitude emissions (LAEs) observed by Two Wide ... [more ▼]

We formulate the first analytical model for energetic neutral atom (ENA) emissivity that partially corrects for the global viewing geometry dependence of low-altitude emissions (LAEs) observed by Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS). The emissivity correction requires the pitch angle distribution (PAD) and geophysical location of low-altitude ENAs. To estimate PAD, we create an energy-dependent analytical model, based on a Monte Carlo simulation. We account for energy binning by integrating model PAD over each energy bin. We account for finite angular pixels by computing emissivity as an integral over the pitch angle range sampled by the pixel. We investigate location uncertainty in TWINS pixels by performing nine variations of the emissivity calculation. Using TWINS 2 ENA imaging data from 1131 to 1145 UT on 6 April 2010, we derive emissivity-corrected ion fluxes for two angular pixel sizes: 4° and 1°. To evaluate the method, we compare TWINS-derived ion fluxes to simultaneous in situ data from the National Oceanic and Atmospheric Administration (NOAA) 17 satellite. The TWINS-NOAA agreement for emissivity-corrected flux is improved by up to a factor of 7, compared to uncorrected flux. The highest 1° pixel fluxes are a factor of 2 higher than for 4° pixels, consistent with pixel-derived fluxes that are artificially low because subpixel structures are smoothed out, and indicating a possible slight advantage to oversampling the instrument-measured LAE signal. Both TWINS and NOAA ion fluxes decrease westward of 2000 magnetic local time. The TWINS-NOAA comparison indicates that the global ion precipitation oval comprises multiple smaller-scale (3-5° of latitude) structures. [less ▲]

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See detailThe Ionospheric Connection Explorer (ICON) : Mission Design and Planning
Immel, T. J.; England, S.; Mende, S. B. et al

Conference (2016)

The Ionospheric Connection Explorer is NASA's next Explorer mission, with a primary scientific goal of understanding the source of the extreme variability in Earth's ionosphere. The observatory is ... [more ▼]

The Ionospheric Connection Explorer is NASA's next Explorer mission, with a primary scientific goal of understanding the source of the extreme variability in Earth's ionosphere. The observatory is scheduled to be delivered to the Pegasus launch vehicle in early 2017 for a June launch. ICON carries unprecedented capability to orbit in a broader national and international effort to understand changes in our space environment occurring on a wide range of spatial and temporal scales. Here, we will discuss plans for the observatory checkout and early operations, and discuss the observing conditions expected in the atmosphere and ionosphere at that time. The status of the science data pipeline and the predicted performance of the observatory for scientific measurements will be discussed. [less ▲]

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See detailSPICAM observations and modeling of Mars aurorae
Soret, Lauriane ULiege; Gérard, Jean-Claude ULiege; Libert, Ludivine ULiege et al

in Icarus (2016), 264

Martian aurorae have been detected with the SPICAM instrument on board Mars Express both in the nadir and the limb viewing modes. In this study, we focus on three limb observations to determine both the ... [more ▼]

Martian aurorae have been detected with the SPICAM instrument on board Mars Express both in the nadir and the limb viewing modes. In this study, we focus on three limb observations to determine both the altitudes and the intensities of the auroral emissions. The CO (a3P–X1R) Cameron bands between 190 and 270 nm, the CO Fourth Positive system (CO 4P) between 135 and 170 nm, the CO2+ doublet at 289 nm, the OI at 297.2 nm and the 130.4 nm OI triplet emissions have been identified in the spectra and in the time variations of the signals. The intensities of these auroral emissions have been quantified and the altitude of the strongest emission of the CO Cameron bands has been estimated to be 137 ± 27 km. The locations of these auroral events have also been determined and correspond to the statistical boundary of open-closed magnetic field lines, in cusp-like structures. The observed altitudes of the auroral emissions are reproduced by a Monte-Carlo model of electron transport in the Martian thermosphere for mono-energetic electrons between 40 and 200 eV. No correlation between electron fluxes measured in the upper thermosphere and nadir auroral intensity has been found. Here, we simulate auroral emissions observed both at the limb and at the nadir using electron energy spectra simultaneously measured with the ASPERA-3/ELS instrument. The simulated altitudes are in very good agreement with the observations. We find that predicted vertically integrated intensities for the various auroral emissions are overestimated, probably as a consequence of the inclination and curvature of the magnetic field line threading the aurora. However, the relative brightness of the CO and CO2+ emissions is in good agreement with the observations. [less ▲]

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