Planetary Sciences: Solar System Objects: Titan; Planetary Sciences: Comets and Small Bodies: Aurorae; airglow; and X-ray emission; Atmospheric Composition and Structure: Airglow and aurora
Abstract :
[en] We present the first UV airglow observations of Titan's atmosphere by the Ultraviolet Imaging Spectrograph (UVIS) on Cassini. Using one spectral channel in the EUV from 561-1182 Å and one in the FUV from 1115-1913 Å, UVIS observed the disk on 13 December, 2004 at low solar activity. The EUV spectrum consists of three band systems of N[SUB]2[/SUB] (b [SUP]1[/SUP]∏[SUB]u[/SUB], b' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP], c[SUB]4[/SUB]' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP] -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP]), while the FUV spectrum consists of one (a [SUP]1[/SUP]∏[SUB]g[/SUB] -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP]). Both the EUV and FUV spectra contain many N I and N II multiplets that are produced primarily by photodissociative ionization. Spectral intensities of the N[SUB]2[/SUB] c[SUB]4[/SUB]' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP](v' = 0) -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP](v'' = 0-2) progression from 950-1010 Å are resolved for the first time. The UVIS observations reveal that the c[SUB]4[/SUB]' [SUP]1[/SUP]∑[SUB]u[/SUB] [SUP]+[/SUP](0) -> X [SUP]1[/SUP]∑[SUB]g[/SUB] [SUP]+[/SUP] (0) vibrational band near 958 Å is weak and undetectable, and that N I multiplets near 953.2 and 964.5 Å are present instead. Magnetospheric particle excitation may be weak or sporadic, since the nightside EUV spectrum on this orbit shows no observable nitrogen emission features and only H Ly-β.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Ajello, Joseph M.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Stevens, Michael H.; Space Science Division, Naval Research Laboratory, Washington, D. C., USA
Stewart, Ian; Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Larsen, Kristopher; Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Esposito, Larry; Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Colwell, Josh; Science Department, Central Arizona College, Coolidge, Arizona, USA
McClintock, William; Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Holsclaw, Greg; Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Gustin, Jacques ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Physique des atmosphères et des environnements planétaires
Pryor, Wayne; Science Department, Central Arizona College, Coolidge, Arizona, USA)
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