Article (Scientific journals)
The production of Titan's ultraviolet nitrogen airglow
Stevens, Michael H; Gustin, Jacques; Ajello, Joseph M et al.
2011In Journal of Geophysical Research. Space Physics, 116, p. 05304
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Keywords :
Atmospheric Composition and Structure: Airglow and aurora; Atmospheric Composition and Structure: Radiation: transmission and scattering; Atmospheric Composition and Structure: Thermosphere: energy deposition (3369); Planetary Sciences: Solar System Objects: Titan; Atmospheric Composition and Structure: Planetary atmospheres (5210; 5405; 5704)
Abstract :
[en] The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Titan's dayside limb in the extreme ultraviolet (EUV) and far ultraviolet (FUV) on 22 June 2009 from a mean distance of 23 Titan radii. These high-quality observations reveal the same EUV and FUV emissions arising from photoelectron excitation and photofragmentation of molecular nitrogen (N[SUB]2[/SUB]) as found on Earth. We investigate both of these solar driven processes with a terrestrial airglow model adapted to Titan and find that total predicted radiances for the two brightest N[SUB]2[/SUB] band systems agree with the observed peak radiances to within 5%. Using N[SUB]2[/SUB] densities constrained from in situ observations by the Ion Neutral Mass Spectrometer on Cassini, the altitude of the observed limb peak of the EUV and FUV emission bands is between 840 and 1060 km and generally consistent with model predictions. We find no evidence for carbon emissions in Titan's FUV airglow in contrast to previous Titan airglow studies using UVIS data. In their place, we identify several vibrational bands from the N[SUB]2[/SUB] Vegard-Kaplan system arising from photoelectron impact with predicted peak radiances in agreement with observations. These Titan UV airglow observations are therefore comprised of emissions arising only from solar processes on N[SUB]2[/SUB] with no detectable magnetospheric contribution. Weaker EUV Carroll-Yoshino N[SUB]2[/SUB] bands within the v′ = 3, 4, and 6 progressions between 870 and 1020 Å are underpredicted by about a factor of five while the (0,1) band near 980 Å is overpredicted by about a factor of three.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Stevens, Michael H;  Space Science Division, Naval Research Laboratory, Washington, D. C., USA
Gustin, Jacques ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Physique des atmosphères et des environnements planétaires
Ajello, Joseph M;  Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Evans, J Scott;  Computational Physics, Inc., Springfield, Virginia, USA
Meier, R. R.;  Department of Physics and Astronomy, George Mason University, Fairfax, Virginia, USA
Kochenash, Andrew J;  Computational Physics, Inc., Springfield, Virginia, USA
Stephan, Andrew W;  Space Science Division, Naval Research Laboratory, Washington, D. C., USA
Stewart, A Ian F;  Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
Esposito, Larry W;  Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
McClintock, William E;  Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
Holsclaw, Greg;  Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
Bradley, E Todd;  Department of Physics, University of Central Florida, Orlando, Florida, USA
Lewis, B. R.;  Research School of Physics and Engineering, Australian National University, Canberra, ACT, Australia
Heays, A. N.;  Research School of Physics and Engineering, Australian National University, Canberra, ACT, Australia
More authors (4 more) Less
Language :
English
Title :
The production of Titan's ultraviolet nitrogen airglow
Publication date :
01 May 2011
Journal title :
Journal of Geophysical Research. Space Physics
ISSN :
2169-9380
eISSN :
2169-9402
Publisher :
American Geophysical Union (AGU), Washington, United States - District of Columbia
Volume :
116
Pages :
05304
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 13 March 2012

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