Aeronomy of Titan and Saturn: Recent Advances From Cassini/Huygens Observations II

Presiding:  M Galand, Center for Space Physics, Boston University; R Yelle, Lunar and Planetary Laboratory, University of Arizona

P33A-01 INVITED   13:30h

Titan's and Saturn's exospheres: First MIMI Energetic Neutral Atom Observations

* Dandouras, I (Iannis.Dandouras@cesr.fr) , Centre d'Etude Spatiale des Rayonnements, 9 Ave. du Colonel Roche B.P. 4346, Toulouse, F-31028 France
Garnier, P (Philippe.Garnier@cesr.fr) , Centre d'Etude Spatiale des Rayonnements, 9 Ave. du Colonel Roche B.P. 4346, Toulouse, F-31028 France
Roelof, E C (Edmond.Roelof@jhuapl.edu) , Applied Physics Laboratory / Johns Hopkins University, Johns Hopkins Roard, Laurel, MD United States
Mitchell, D G (don.mitchell@jhuapl.edu) , Applied Physics Laboratory / Johns Hopkins University, Johns Hopkins Roard, Laurel, MD United States
Brandt, P C (brandpc1@jhuapl.edu) , Applied Physics Laboratory / Johns Hopkins University, Johns Hopkins Roard, Laurel, MD United States
Krimigis, S M (Tom.Krimigis@jhuapl.edu) , Applied Physics Laboratory / Johns Hopkins University, Johns Hopkins Roard, Laurel, MD United States
Krupp, N (krupp@linmpi.mpg.de) , Max Planck Institute for Solar System Research, Max-Planck-Str. 2, Katlenburg-Lindau, Germany
Hamilton, D C (dch@umd.edu) , University of Maryland, College Park, MD United States
Toublanc, D (dominique.toublanc@cesr.fr) , Centre d'Etude Spatiale des Rayonnements, 9 Ave. du Colonel Roche B.P. 4346, Toulouse, F-31028 France

Titan's nitrogen-rich atmosphere is directly bombarded by energetic ions, due to its lack of a significant intrinsic magnetic field. Singly-charged energetic ions from Saturn's magnetosphere undergo charge exchange collisions with neutral atoms in Titan's exosphere, being transformed into energetic neutral atoms (ENAs). The Ion and Neutral Camera (INCA), one of the three sensors that comprise the Magnetosphere Imaging Instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images the ENA emissions from various ion/gas interaction regions in the Saturnian magnetosphere. During Cassini's second orbit around Saturn the spacecraft performed the Ta Titan flyby (October 26, 2004), at an altitude of only 1174 km. INCA data acquired during this targeted close flyby confirm model predictions of dominant finite ion gyroradii effects, but also reveal a much more complex interaction: maximum ENA emissions are originating at higher altitudes than predicted by a simple Chamberlain-type model of the Titan exosphere. These observations will be analyzed and a simulation will be presented of some of the exospheric features they reveal.

P33A-02   13:50h

THE NEUTRAL H22 CLOUD AROUND TITAN OBTAINED FROM CASSINI/INCA OBSERVATIONS

* Brandt, P C (pontus.brandt@jhuapl.edu) , The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, md 20723 United States
Roelof, E C (ed.roelof@jhuapl.edu) , The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, md 20723 United States
Dandouras, I (iannis.dandouras@cesr.fr) , Centre d'Etude Spatiale des Rayonnements, 9, avenue du Colonel Roche , Toulouse, France
Saur, J (joachim.saur@jhuapl.edu) , The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, md 20723 United States
Mitchell, D G (don.mitchell@jhuapl.edu) , The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, md 20723 United States
Mauk, B H (barry.mauk@jhuapl.edu) , The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, md 20723 United States
Paranicas, C (chris.paranicas@jhuapl.edu) , The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, md 20723 United States
Krimigis, S M (stamatios.krimigis@jhuapl.edu) , The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, md 20723 United States

The Ion Neutral Camera on board Cassini has obtained Energetic Neutral Atom (ENA) images of the interaction between the energetic (10-200 keV) ions of the magnetosphere and Titan's outer exosphere. There are several Titan encounters where Titan's atmosphere is "illuminated" by the energetic ion clouds corotating over Titan. They are characterized by ENA emissions extending to large (10,000 km) altitudes above Titan. During periods when the energetic ion clouds are much larger than 10's of Titan radii, it is possible to investigate the distribution of Titan's outermost exosphere. We find that the images are consistent with an extended H2 cloud extending out well beyond 10,000 km altitude with a 1/r2 dependence.

P33A-03 INVITED   14:05h

Cassini's first Titan encounters: a comparison of plasma results

* Coates, A J (ajc@mssl.ucl.ac.uk) , Mullard Space Science Laboratory University College London, Holmbury St Mary, Dorking, RH5 6NT United Kingdom
Crary, F J (fcrary@swri.edu) , Southwest Research Institute, Division of Space Science and Engineering 6220 Culebra Road P.O. Drawer 28510, San Antonio, TX 78228-0510 United States
Rymer, A M (amr@mssl.ucl.ac.uk) , Mullard Space Science Laboratory University College London, Holmbury St Mary, Dorking, RH5 6NT United Kingdom
Szego, K (szego@rmki.kfki.hu) , KFKI-RMKI, Konkoly Thege str. 29-33, Bldg. III,, Budapest, H-1121 Hungary
Steinberg, J T (jsteinberg@lanl.gov) , Los Alamos National Laboratory Space and Atmospheric Science Group, NIS-1 Mail stop: D-466, Los Alamos, NM 87545 United States
Vilppola, J (jari.vilppola@oulu.fi) , University of Oulu, Department of Physical Sciences Linnanmaa, Oulu, FIN-90014 Finland
Young, D T (dyoung@swri.edu) , Southwest Research Institute, Division of Space Science and Engineering 6220 Culebra Road P.O. Drawer 28510, San Antonio, TX 78228-0510 United States

We compare plasma data from the Cassini Plasma Spectrometer (CAPS) for the first encounters of Titan by the Cassini orbiter. Several features in the ionosphere are present, including at least 10 species of organic positive ions, negative ions, and ionospheric photoelectrons. Some features in the larger scale interaction are different between encounters, such as the interaction size, detailed structure, geometry and the magnetospheric conditions in which Titan is immersed. In this paper we will compare the electron and ion measurements made by CAPS and explore possible reasons for the difference in the observed structures at the different encounters.

P33A-04   14:25h

Preliminary Interpretation of Titan Plasma Interaction as Observed by the Cassini Plasma Spectrometer: Comparisons With Voyager 1

* Hartle, R E (Richard.E.Hartle@nasa.gov) , NASA Goddard Space Flight Center, Code 910, Greenbelt Road, Greenbelt, MD 20771 United States
Sittler, E C (edward.c.sittler@nasa.gov) , NASA Goddard Space Flight Center, Code 910, Greenbelt Road, Greenbelt, MD 20771 United States
Johnson, R E (rej@unix.mail.virginia.edu) , University of Virginia, Engineering Physics, Thornton Hall, Charlottesville, VA 22904 United States
Simpson, D G (David.G.Simpson@nasa.gov) , NASA Goddard Space Flight Center, Code 910, Greenbelt Road, Greenbelt, MD 20771 United States
Smith, H T (hts4f@virginia.edu) , University of Virginia, Engineering Physics, Thornton Hall, Charlottesville, VA 22904 United States
Crary, F (fcrary@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228-0510 United States
McComas, D J (dmccomas@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228-0510 United States
Young, D T (dyoung@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228-0510 United States
Coates, A J (ajc@mssl.ucl.ac.uk) , Mullard Space Flight Center, Holmbury St. Mary, Dorking, Surrey, RH5 6NT United Kingdom
Neubauer, F M (neubauer@geo.Uni-Koeln.DE) , University of Koln Institute for Geophysics and Meteorology, Albertus-Magnus-Platz, Koln, D 50923 Germany
Bolton, S (Scott.J.Bolton@jpl.nasa.gov) , Jet Propulsion Laboratory, MS 230-205, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
Reisenfeld, D (dan.reisenfeld@umontana.edu) , University of Montana Department of Physics & Astronomy, 32 Campus Drive, Missoula, MT 59812 United States
Szego, K (szego@rmki.kfki.hu) , KFKI-RMKI, KFKI Research Institute for Particle and Nuclear Physics, Konkoly Thege str. 29-33, Bldg. III, Budapest, H-1525 Hungary
Berthelier, J (jacques.berthelier@cetp.ipsl.fr) , Centre d'etude des Environnements Terrestre et Planetaires, Observatoire de Saint-Maur, 4 Avenue de Neptune, St. maur-des-Fosses, 94107 France
Michael, M (mm2eq@virginia.edu) , University of Virginia, Engineering Physics, Thornton Hall, Charlottesville, VA 22904 United States
Rymer, A (amr@mssl.ucl.ac.uk) , Mullard Space Flight Center, Holmbury St. Mary, Dorking, Surrey, RH5 6NT United Kingdom
Vippola, J (jari.vilppola@oulu.fi) , University of Oulu, Department of Physical Sciences, Linnanmaa, FIN-90014 Finland
Steinberg, J T (jsteinberg@lanl.gov) , Los Alamos National Laboratory, Space and Atmospheric Science Group, MS: D-466, Los Alamos, NM 87545 United States
Andre, N (Nicolas.Andre@cesr.fr) , CESR, 9, avenue du Colonel Roche, Toulous, 4346 31028 France

The Cassini Plasma Spectrometer (CAPS) instrument made measurements of Titan's plasma environment when the Cassini Orbiter flew through the moon's plasma wake October 26, 2004 (flyby TA) and December 13, 2004 (flyby TB). Preliminary CAPS ion and electron measurements from these encounters (1, 2) are compared with measurements made by the Voyager I Plasma Science Instrument (PLS). The comparisons are used to evaluate previous interpretations and predictions of the Titan plasma environment that have been made using PLS measurements (3, 4). The plasma wake trajectories of flybys TA, TB and Voyager 1are similar because they occurred when Titan was near Saturn's local noon. These similarities make possible direct, meaningful comparisons between the various plasma wake measurements. The inquiries stimulated by the previous interpretations and predictions made using PLS data have produced the following results from the CAPS ion measurements: A) The major ambient ion components of Saturn's rotating magnetosphere in the vicinity of Titan are H+, H2+, and O+. B) Finite gyroradius effects are apparent in ambient O+ as the result of its interaction with Titan's atmosphere. C) The principal pickup ions are composed of H+, H2+, CH4+ and N2+. D) There is clear evidence of slowing down of the ambient plasma due to pickup ion mass loading; and, as the "ionopause" is approached, heavier pickup ions such as N2+ become dominant. The similarities and differences between the magnitudes and structures of the electron densities and temperatures along the three flyby trajectories are described. 1. D. T. Young et al. (2004), Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract P41B-07. 2. A. J. Coates et al. (2004), Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract P53A-1451. 3. R. E. Hartle et al., J. Geophys. Res., 87, 1383, 1982. 4. E. C. Sittler et al., Titan Symposium Proceedings, ESTEC, Editor, Jean-Pierre Lebreton, 2004.

P33A-05 INVITED   14:40h

Cassini Ion Neutral Mass Spectrometer (INMS) Results from Titan

* Cravens, T E (cravens@ku.edu) , University of Kansas, Dept. of Physics and Astronomy, Lawrence, KS 66045 United States
Waite, J H (hunterw@umich.edu) , University of Michigan, Dept. of Atmospheric, Oceanic, and Space Sci., Ann Arbor, MI 48109 United States
Niemann, H (Hasso.Niemann@gsfc.nasa.gov) , NASA Goddard Space Flight Center, GSFC, Greenbelt, MD 20771 United States
Yelle, R V (yelle@lpl.arizona.edu) , University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ 85721 United States
Kasprzak, W T (wayne.kascprzak@gsfc.nasa.gov) , NASA Goddard Space Flight Center, GSFC, Greenbelt, MD 20771 United States
Luhmann, J G (jgluhman@sunspot.ssl.berkeley.edu) , University of California, Space Sciences Laboratory, Berkeley, CA 94720 United States
McNutt, R L (ralph_mcnutt@jhuapl.edu) , John Hopkins Univ., Applied Physics Laboratory, Laurel, MD 20723 United States
Ip, W (wingip@astro.ncu.edu.tw) , National Central University, Instit. of Astronomy, Chung-Li, Taiwan
Gell, D (gellda@umich.edu) , University of Michigan, Dept. of Atmospheric, Oceanic, and Space Sci., Ann Arbor, MI 48109 United States
De La Haye, V (vdelah@engin.umich.edu) , University of Michigan, Dept. of Atmospheric, Oceanic, and Space Sci., Ann Arbor, MI 48109 United States
Muller-Wordag, I (i.Muellerwodarg@imperial.ac.uk) , Imperial College, Space and Atmospheric Physics Group, London, United Kingdom
Ledvina, S L (ledvina@ssl.berkeley.edu) , University of California, Space Sciences Laboratory, Berkeley, CA 94720 United States
Robertson, I P (robertin@ku.edu) , University of Kansas, Dept. of Physics and Astronomy, Lawrence, KS 66045 United States
Borggren, N (borggren@lpl.arizona.edu) , University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ 85721 United States

The Cassini Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini Orbiter measured the neutral composition and structure of the upper atmosphere of Titan during the first flyby (Ta) of this satellite. The INMS detected N2, CH4, and H2, the noble gas argon, and a host of more complex hydrocarbon and nitrile species. INMS also made neutral measurements during the Tb flyby. During the T5 Titan flyby, which took place in April 2005, the INMS measured both the neutral and the ion composition of the upper atmosphere and ionosphere. These measurements will be summarized in this talk. The implications of these measurements for our current understanding of the photochemistry, dynamics, and energetics of Titan's upper atmosphere and ionosphere will also be discussed.

Cite abstracts as: Authors (2005), Title, Eos. Trans. AGU, 86(18), Jt. Assem. Suppl., Abstract #####-##.