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| Titel |
Seasonal Transport in Mars’ Mesosphere revealed by Nitric Oxide Nightglow vertical profiles and global images from IUVS/MAVEN |
| VerfasserIn |
Arnaud Stiepen, Ian Stewart, Sonal Jain, Nicholas Schneider, Justin Deighan, Francisco González-Galindo, Jean-Claude Gérard, Michael Stevens, Stephen Bougher, Zachariah Milby, Scott Evans, Michael Chaffin, William McClintock, John Clarke, Greg Holsclaw, Franck Montmessin, Franck Lefèvre, Daniel Lo, Bruce Jakosky |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149958
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| Publikation (Nr.) |
 EGU/EGU2017-14370.pdf |
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| Zusammenfassung |
| Abstract:
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).
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 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 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.
Acknowledgements
A. Stiepen is supported the Fund for Scientific Research (F.R.S.-FNRS). The
MAVEN mission is supported by NASA through the Mars Exploration Program in
association with the University of Colorado and NASA’s Goddard Space Flight Center.
M. Stevens is supported by the NASA MAVEN Participating Scientist program. |
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