References of "Stiepen, Arnaud"
     in
Bookmark and Share    
See detailSeasonal Transport in Mars’ Mesosphere revealed by Nitric Oxide Nightglow
Stiepen, Arnaud ULg

Conference (2017, June 21)

We analyze the ultraviolet nightglow in the atmosphere of Mars through Nitric Oxide (NO) δ and γ bands emissions. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation partly ... [more ▼]

We analyze the ultraviolet nightglow in the atmosphere of Mars through Nitric Oxide (NO) δ and γ bands emissions. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation partly dissociates CO2 and N2 molecules. O(3P) and N(4S) atoms are carried by the day-to-night hemispheric transport. They preferentially descend in the nightside mesosphere in the winter hemisphere, where they can radiatively recombine to form NO(C2Π). The excited molecules promptly relax by emitting photons in the UV δ bands and in the γ bands through cascades via the A2Σ, v’ = 0 state. These emissions are thus indicators of the N and O atom fluxes transported from the dayside to Mars’ nightside and the winter descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015, 2017). Observations of these emissions have been accumulated on a large dataset of nightside disk images and vertical profiles obtained at the limb by the Imaging Ultraviolet Spectrograph (IUVS, McClintock et al., 2015) instrument when the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft is at its apoapsis and its periapsis phases along its orbit, respectively. We present discussion on the variability in the brightness and altitude and of the emission with season, geographical position and local time and possible interpretation for local and global changes in the mesosphere dynamics. IUVS images and limb scans reveal unexpected complex structure of the emission. The brightest emission is observed close to the winter pole. The emission is also surprisingly more intense in some longitude, revealing possible impact of tides and waves in Mars’ nightside mesosphere. Observations also reveal spots and streaks, indicating irregularities in the wind circulation pattern. The disk images and limb profiles are compared to the LMD-MGCM model (Gonzàlez-Galindo et al., 2009 ; Lopez-Valverde et al., 2011) to focus on the seasonal, local time and geographical influences on the NO Nightglow emission. We will also provide a statistical study of the regions of enhanced brightness (i.e. splotches and streaks) and discuss possible interpretation from the comparison to the GCM. [less ▲]

Detailed reference viewed: 13 (1 ULg)
Full Text
Peer Reviewed
See detailMartian mesospheric cloud observations by IUVSon MAVEN: Thermal tides coupled to the upper atmosphere
Stevens; Siskind; Evans et al

in Geophysical Research Letters (2017), 44

The manuscript describes the observation of Martian mesosphericclouds between 60 and 80 km altitude by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’sMAVEN spacecraft. The cloud observations are ... [more ▼]

The manuscript describes the observation of Martian mesosphericclouds between 60 and 80 km altitude by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’sMAVEN spacecraft. The cloud observations are uniquely obtained at early morning local times, whichcomplement previous observations obtained primarily later in the diurnal cycle. Differences in thegeographic distribution of the clouds from IUVS observations indicate that the local time is crucial for theinterpretation of mesospheric cloud formation. We also report concurrent observations of upperatmospheric scale heights near 170 km altitude, which are diagnostic of temperature. These observationssuggest that the dynamics enabling the formation of mesospheric clouds propagate all the way to theupper atmosphere. [less ▲]

Detailed reference viewed: 16 (3 ULg)
See detailHighlights from two years of remote sensing at Mars with MAVEN’s Imaging Ultraviolet Spectrograph
Chaffin; Schneider; Deighan et al

Poster (2017, April 27)

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission’s Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric ... [more ▼]

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission’s Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric structure and indirectly probing neutral atmospheric escape. After two Earth years in orbit (one Mars year), IUVS has assembled a large quantity of data and made many discoveries, some of which we report here. Among the key results obtained by IUVS are: (1) discovery of the widespread occurrence of a diffuse proton aurora, representing a newly discovered means of energy deposition into the atmospheres of unmagnetized planets; (2) continued investigation of time-variability in H and O escape, which have dessicated the planet over its history; and (3) synoptic characterization of thermospheric variability and response to solar input. We will present an overview of these results and a discussion of their implications for the state of the atmosphere and its evolution. [less ▲]

Detailed reference viewed: 11 (1 ULg)
See detailObjectif Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 15 (0 ULg)
See detailEmbarquement pour Mars: défi et opportunité
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 13 (1 ULg)
See detailEmbarquement pour Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 25 (4 ULg)
See detailObjectif Mars: défi ou utopie?
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 15 (1 ULg)
See detailMars Ozone mapping with MAVEN IUVS
Lefèvre; Stiepen, Arnaud ULg; IUVS team

Conference (2017, January 20)

Detailed reference viewed: 13 (1 ULg)
See detailCharacterization of High Altitude Clouds at the Martian Limb and Terminator Using MAVEN IUVS Observations
Deighan; Stiepen, Arnaud ULg; IUVS team

Conference (2017, January 20)

Detailed reference viewed: 8 (1 ULg)
See detailGlobal Simulation of UV atmospheric Emissions
Gonzalez-Galindo; Lopez-Valverde; Forget et al

Poster (2017, January 19)

Detailed reference viewed: 13 (1 ULg)
See detailA persistent meteoric layer in Mars' atmosphere
Crismani; Schneider; Plane et al

Poster (2017, January 18)

Detailed reference viewed: 13 (0 ULg)
See detailThree Types of Aurora observed by MAVEN/IUVS: Implications for Mars’ upper Atmosphere Energy Budget
Connour; Schneider; Jain et al

Poster (2017, January 17)

Detailed reference viewed: 34 (4 ULg)
See detailGlobal UV Imaging by MAVEN/IUVS: Diurnal Cloud Formation, Dust Storms and Atmospheric Scattering.
Schneider; Deighan; Jain et al

Conference (2017, January 17)

Detailed reference viewed: 13 (1 ULg)
See detailNO Nightglow studies status
Stiepen, Arnaud ULg; Jain; Deighan et al

Conference (2017, January 16)

Detailed reference viewed: 9 (1 ULg)
See detailEmbarquement pour Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailNitric Oxide Nightglow and Martian Mesospheric Circulation from MAVEN/IUVS Observations and LMD-MGCM Predictions
Stiepen, Arnaud ULg; Jain; Schneider et al

in Journal of Geophysical Research. Space Physics (2017)

We report results from a study of nitric oxide nightglow over the north- ern hemisphere of Mars during winter, the southern hemisphere during fall equinox and equatorial latitudes during summer in the ... [more ▼]

We report results from a study of nitric oxide nightglow over the north- ern hemisphere of Mars during winter, the southern hemisphere during fall equinox and equatorial latitudes during summer in the northern hemisphere based on observations of the delta and gamma bands between 190 and 270 nm by the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft. The emission reveals recombination of N and O atoms dissociated on the day- side of Mars and transported to the nightside. We characterize the bright- ness (from 0.2 to 30 kR) and altitude (from 40 to 115 km) of the NO night- glow layer, as well as its topside scale height (mean of 11 km). We show the possible impact of atmospheric waves forcing longitudinal variability, asso- ciated with an increased brightness by a factor 3 in the 140 - 200 longitude region in the northern hemisphere winter and in the -102 to -48 longitude region at summer. Such impact to the NO nightglow at Mars was not seen before. Quantitative comparison with calculations of the LMD-MGCM (Lab- oratoire de M et eorologie Dynamique - Global Circulation Model) suggests that the model globally reproduces the trends of the NO nightglow emission and its seasonal variation, but also indicates large discrepancies (up to a fac- tor 50 fainter in the model) in northern winter at low to mid-latitudes. This suggests that the predicted transport is too e cient towards the night win- ter pole in the thermosphere by 20 latitude north. [less ▲]

Detailed reference viewed: 15 (2 ULg)
Full Text
Peer Reviewed
See detailVariability of D and H in the Martian Upper Atmosphere Observed with the MAVEN IUVS Echelle Channel
Clarke, J. T.; Mayyasi, M.; Bhattacharyya, D. et al

in Journal of Geophysical Research. Space Physics (2017)

The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions ... [more ▼]

The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions, which are produced by resonant scattering of solar emission, over the course of most of a martian year. The fundamental purpose of these measurements is to understand the physical principles underlying the escape of H and D from the upper atmosphere into space, and thereby to relate present-day measurements of an enhanced HDO/H2O ratio in the bulk atmosphere to the water escape history of Mars. Variations in these emissions independent of the solar flux reflect changes in the density and/or temperature of the species in the upper atmosphere. The MAVEN measurements show that the densities of both H and D vary by an order of magnitude over a martian year, and not always in synch with each other. This discovery has relevance to the processes by which H and D escape into space. One needs to understand the controlling factors to be able to extrapolate back in time to determine the water escape history from Mars at times when the atmosphere was thicker, when the solar flux and solar wind were stronger, etc. Further measurements will be able to identify the specific controlling factors for the large changes in H and D, which likely result in large changes in the escape fluxes of both species. [less ▲]

Detailed reference viewed: 13 (1 ULg)
Full Text
Peer Reviewed
See detailThe structure and variability of Mars dayside thermosphere from MAVEN NGIMS and IUVS measurements: Seasonal and solar activity trends in scale heights and temperatures
Bougher, S. W.; Roeten, K. J.; Olsen, K. et al

in Journal of Geophysical Research. Space Physics (2017)

Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on the ... [more ▼]

Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft. Average scale heights (over 150-180 km for solar zenith angles ≤75°) from several different sampling periods were obtained from each instrument. NGIMS and IUVS scale height trends were found to be in good agreement, with both showing scale heights decreasing after perihelion and reaching a low value near aphelion (13.6 to 9.4 km). Between these two seasonal extremes, the temperature decreased by ∼70 K (from 240 to 170 K). These trends were also analyzed with respect to the changing solar flux reaching the planet, using the Lyman alpha irradiance measured by the Extreme Ultraviolet Monitor (EUVM) on MAVEN. Scale heights responded strongly to the changing solar flux. During this part of the MAVEN mission (October 2014 to May 2016), it was concluded that over longer timescales (at least several months), dayside thermospheric temperatures are chiefly driven by changing solar forcing, although it is the effects of changing heliocentric distance rather than changing solar activity which seem to have the greatest impact. Furthermore, effects of solar forcing were not observed on shorter timescales (less than a month), suggesting local wave effects may dominate solar forcing on these timescales. Finally, temperatures from two NGIMS sampling periods were compared to temperatures from the Mars Global Ionosphere-Thermosphere Model (M-GITM) and found to be in good agreement. © 2017. American Geophysical Union. All Rights Reserved. [less ▲]

Detailed reference viewed: 10 (2 ULg)
See detailSeasonal Transport in Mars’ Mesosphere revealed by Nitric Oxide Nightglow vertical profiles and global images from IUVS/MAVEN
Stiepen, Arnaud ULg; Stewart; Jain et al

Conference (2017)

We analyze the ultraviolet nightglow in the atmosphere of Mars through Nitric Oxide (NO) δ and γ bands emis- sions. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation partly ... [more ▼]

We analyze the ultraviolet nightglow in the atmosphere of Mars through Nitric Oxide (NO) δ and γ bands emis- sions. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation partly dissociates CO2 and N2 molecules. O(3P) and N(4S) atoms are carried by the day-to-night hemispheric transport. They preferentially descend in the nightside mesosphere in the winter hemisphere, where they can radiatively recombine to form NO(C2Π). The excited molecules promptly relax by emitting photons in the UV δ bands and in the γ bands through cascades via the A2Σ, v’ = 0 state. These emissions are thus indicators of the N and O atom fluxes transported from the dayside to Mars’ nightside and the winter descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015). Observations of these emissions have been accumulated on a large dataset of nightside disk images and vertical profiles obtained at the limb by the Imaging Ultraviolet Spectrograph (IUVS, McClintock et al., 2015) instrument when the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft is at its apoapsis and its periapsis phases along its orbit, respectively. We present discussion on the variability in the brightness, altitude and topside scale height of the emission with season, geographical position and local time and possible interpretation for local and global changes in the meso- sphere dynamics. IUVS images and limb scans reveal unexpected complex structure of the emission. The brightest emission is observed close to the winter pole. The emission is also surprisingly more intense in some sectors located close to the equator : at 120 ̊ and 150 ̊ longitude. Observations also reveal spots and streaks, indicating irregularities in the wind circulation pattern and possible impact of waves and tides. The disk images and limb profiles are compared to the LMD-MGCM model (Gonzàlez-Galindo et al., 2009 ; Lopez-Valverde et al., 2011) to focus on the seasonal, local time and geographical influences on the NO Nightglow emission. We will also provide a statistical study of the regions of enhanced brightness (i.e. splotches and streaks) and discuss possible interpretation from the comparison to the GCM. [less ▲]

Detailed reference viewed: 20 (1 ULg)