P53B-01 13:40h

Saturn's UV Aurora Imaged with HST during the Cassini Approach to Saturn

* Clarke, J T (jclarke@bu.edu) , Center for Space Physics Boston University, 725 Commonwealth Ave, Boston, MA 02215 United States
Gerard, J (JC.Gerard@ulg.ac.be) , University of Liege, Allee du 6 Aout Sart Tilman, Liege, B4000 Belgium
Grodent, D (D.Grodent@ulg.ac.be) , University of Liege, Allee du 6 Aout Sart Tilman, Liege, B4000 Belgium
Wannawichian, S (suwichaw@bu.edu) , Center for Space Physics Boston University, 725 Commonwealth Ave, Boston, MA 02215 United States
Gustin, J (J.Gustin@ulg.ac.be) , University of Liege, Allee du 6 Aout Sart Tilman, Liege, B4000 Belgium
Connerney, J (jec@lepjec.gsfc.nasa.gov) , NASA Goddard Space Flight Center, Code 695, Greenbelt, MD 20771 United States
Crary, F (fcrary@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228 United States
Dougherty, M (m.dougherty@ic.ac.uk) , Imperial College, Blackett Lab., London, SW7 2AZ United Kingdom
Kurth, W (wsk@space.physics.uiowa.edu) , Univ. of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
Cowley, S W (swhc1@ion.le.ac.uk) , Univ. of Leicester, Dept. of Physics and Astronomy, Leicester, LE1 7RH United Kingdom
Bunce, E (ejb10@ion.le.ac.uk) , Univ. of Leicester, Dept. of Physics and Astronomy, Leicester, LE1 7RH United Kingdom
Hill, T (hill@rice.edu) , Rice University, Dept. of Physics and Astronomy, Houston, TX 77005 United States
Kim, J (juwhan@hotmail.com) , Yonsei Univ., School of Civil and Environmental Engineering, Seoul, 120-749 Korea, Republic of

A series of HST STIS UV images of Saturn's aurora were obtained on 13 days in Jan. 2004 as the Cassini spacecraft measured the approaching solar wind properties. Clear general correlations have been found between the auroral power and a) Saturn's kilometric radiation, and b) the solar wind dynamic pressure, but not with the direction of the interplanetary magnetic field. While these general correlations are now well established, a closer examination of the data raises many interesting questions. Saturn's auroral emissions exhibit both local time and co-rotational properties, the auroral oval does not appear centered on the magnetic and rotational pole, the auroral emissions exhibit large and unexpected motions in latitude with time and/or planetary rotation, and the auroral oval does not appear continuous, but broken with longitude. This talk will present a more detailed look at Saturn's aurora from the HST images, with a comparison of auroral emission properties to those at the Earth and Jupiter.

P53B-02 INVITED 13:55h

Initial Cassini Plasma Observations at Saturn

* Crary, F J (fcrary@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78229 United States
Young, D T (dyoung@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78229 United States
Burch, J L (jburch@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78229 United States
Goldstein, R (rgoldstein@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78229 United States
McComas, D J (dmccomas@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78229 United States
Furman, F D (jfurman@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78229 United States
Zinsmeyer, C (czinsmeyer@swri.edu) , Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78229 United States
Berthelier, J (jean-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
Illiano, J (jean-marie.illiano@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
Blanc, M (blanc@obs-mip.fr) , Observatoire Midi-Pyrenees, 14, Avenue Edouard Belin , Toulouse, 31400 France
Maurice, S (maurice@obs-mip.fr) , Observatoire Midi-Pyrenees, 14, Avenue Edouard Belin , Toulouse, 31400 France
Pallier, E (etienne.pallier@obs-mip.fr) , Observatoire Midi-Pyrenees, 14, Avenue Edouard Belin , Toulouse, 31400 France
Bolton, S (Scott.J.Bolton@jpl.nasa.gov) , Jet Propulsion Laboratory, 4800 Oak Grove Drive , Pasadena, CA 91109 United States
Coates, A J (ajc@mssl.ucl.ac.uk) , University College London, Mullard Space Science Laboratory Holmbury St. Mary, Dorking, RH5 United Kingdom
Linder, D R (drl@mssl.ucl.ac.uk) , University College London, Mullard Space Science Laboratory Holmbury St. Mary, Dorking, RH5 United Kingdom
Rymer, A M (amr@mssl.ucl.ac.uk) , University College London, Mullard Space Science Laboratory Holmbury St. Mary, Dorking, RH5 United Kingdom
McAndrews, H (hjm@mssl.ucl.ac.uk) , University College London, Mullard Space Science Laboratory Holmbury St. Mary, Dorking, RH5 United Kingdom
Grande, M (m.grande@rl.ac.uk) , Rutherford Appleton Laboratory, Chilton, Didcot Oxfordshire, Chilton, Didcot, OX11 0QX United Kingdom
Hill, T W (hill@rice.edu) , Rice University, Physics and Astronomy Department MS 108, Houston, TX 77251 United States
Johnson, R E (rej@virginia.edu) , University of Virginia, Engineering Physics, Thornton Hall, Charlottesville, VA 22904 United States
Baragiola, R A (rb9a@virginia.edu) , University of Virginia, Engineering Physics, Thornton Hall, Charlottesville, VA 22904 United States
Smith, H T (hts4f@virginia.edu) , University of Virginia, Engineering Physics, Thornton Hall, Charlottesville, VA 22904 United States
Kelha, V (vaino.kelha@pp.inet.fi) , VTT Industrial Systems, Metallimiehenkuja 8, P.O. Box 1303 , Metallimiehenkuja, 1303 Finland
Holmlund, C (christer.holmlund@vtt.fi) , VTT Industrial Systems, Metallimiehenkuja 8, P.O. Box 1303 , Metallimiehenkuja, 1303 Finland
Mursula, K (kalevi.mursula@oulu.fi) , University of Oulu, Department of Physical Sciences, Linnanmaa, FIN-90014 Finland
Tanskanen, P (pekkatanskanen@kolumbus.fi) , University of Oulu, Department of Physical Sciences, Linnanmaa, FIN-90014 Finland
Vilppola, J (jari.vilppola@oulu.fi) , University of Oulu, Department of Physical Sciences, Linnanmaa, FIN-90014 Finland
Sittler, E C (Edward.C.Sittler@nasa.gov) , Goddard Space Flight Center, Goddard Space Flight Center, Greenbelt, MD 20771 United States
Glenn, D (dglenn@pop500.gsfc.nasa.gov) , Goddard Space Flight Center, Goddard Space Flight Center, Greenbelt, MD 20771 United States
Bakshi, S (Sarabjit.S.Bakshi.1@gsfc.nasa.gov) , Goddard Space Flight Center, Goddard Space Flight Center, Greenbelt, MD 20771 United States
Svenes, K R (ksv@ffi.no) , Norwegian Defence Research Establishment, Division for Electronics P.O. Box 25, Kjeller, N-2027 Norway
Norheim, B T (btn@ffi.no) , Norwegian Defence Research Establishment, Division for Electronics P.O. Box 25, Kjeller, N-2027 Norway
Szego, K (szego@rmki.kfki.hu) , KFKI Research Institute for Particle and Nuclear Physics, P. O. Box 49, Budapest, H-1525 Hungary
Bebesi, Z (bzsofi@rmki.kfki.hu) , KFKI Research Institute for Particle and Nuclear Physics, P. O. Box 49, Budapest, H-1525 Hungary
Thomsen, M F (mthomsen@lanl.gov) , Los Alamos National Laboratory, Space and Atmospheric Science Group NIS-1 (505) 667-2701 Mail Stop: D-466, Los Alamos, NM 87545 United States
Barraclough, B L (bbarraclough@lanl.gov) , Los Alamos National Laboratory, Space and Atmospheric Science Group NIS-1 (505) 667-2701 Mail Stop: D-466, Los Alamos, NM 87545 United States
Delapp, D (ddelapp@nis.lanl.gov) , Los Alamos National Laboratory, Space and Atmospheric Science Group NIS-1 (505) 667-2701 Mail Stop: D-466, Los Alamos, NM 87545 United States
Nordholt, J E (jnordholt@lanl.gov) , Los Alamos National Laboratory, Space and Atmospheric Science Group NIS-1 (505) 667-2701 Mail Stop: D-466, Los Alamos, NM 87545 United States
Steinberg, J (jsteinberg@lanl.gov) , Los Alamos National Laboratory, Space and Atmospheric Science Group NIS-1 (505) 667-2701 Mail Stop: D-466, Los Alamos, NM 87545 United States
Tokar, R L (rlt@lanl.gov) , Los Alamos National Laboratory, Space and Atmospheric Science Group NIS-1 (505) 667-2701 Mail Stop: D-466, Los Alamos, NM 87545 United States
Reisenfeld, D (dan.reisenfeld@umontana.edu) , University of Montana, Department of Physics and Astronomy 32 Campus Drive, Missoula, MT 59812 United States

The Cassini Plasma Spectrometer (CAPS) measures ion energy and mass from 1 eV to 50 keV and electron spectra from 1 eV to 28 keV. It thus fills in important gaps in earlier Voyager measurements of plasma energy and composition. This paper gives an overview of data taken during the first two Cassini orbits, including the closest approach to Saturn and the rings during the tour (1.3 $_{S}$), and a close flyby of Titan (1250 km altitude), two passes through Saturn's inner magnetosphere (one at a moderate, 10-15$^{o}$ latitude height above the equatorial plane, and one crossing the equatorial plane at approximately 8 R$_{S}$), and period of roughly 50 days of solar wind monitoring in conjunction with Cassini remote sensing of Saturn's aurora. Initial analysis shows the existence of H$^{+}$, H$_{2}$$^{+}$ and/or He$++}$, N$^{+}$, water group, and O$_{2}$$^{+}$ ions within Saturn's magnetosphere, the exact composition depending on location. Several distinctive regions of plasma have been identified including a cold ``ionosphere'' located over the rings, a region of quiescent, corotating plasma between approximately 2 R$_{S}$ and 6 R$_{S}$, a region of highly disturbed plasma between 6 $_{S}$ and 14 $_{S}$, containing numerous injection and/or local acceleration events, and a region of hot, very low density plasma outside approximately 14 $_{S}$. We also anticipate being able to give an overview of observations of plasma in the proximity of Titan and its ionosphere.

P53B-03 INVITED 14:15h

Cassini Magnetometer observations at Saturn

* Dougherty, M K (m.dougherty@imperial.ac.uk) , Imperial College, The Blackett Laboratory, London, SW7 2AZ United Kingdom

An overview of the magnetic field observations at Saturn from the dual technique magnetometer onboard the Cassini orbiter will be described. This will include a discussion of the approach science phase; Saturn Orbit Insertion itself which was a critical observation for resolution of the internal planetary field; as well as the first observations for 25 years taken within the Saturnian magnetosphere. Comparisons will be made with the previous Pioneer and Voyager flyby data sets and the very dynamic nature of magnetosphere and the clear magnetospheric regions which Cassini traversed will be discussed.

P53B-04 14:35h

Saturn's Magnetosphere During Cassini's Approach and Initial Orbit

* Hansen, K C (kenhan@umich.edu) , University of Michigan, 1411D Space Research Bldg., Ann Arbor, MI 48109-2143
Clarke, J T , Boston University, Center for Space Physics Boston University 725 Commonwealth Ave, Boston, MA 02215
Crary, F J , Southwest Research Institute, 6220 Culebra Road P.O. Box 28510, San Antonio, TX 78228-0510
De Zeeuw, D L , University of Michigan, 1411D Space Research Bldg., Ann Arbor, MI 48109-2143
Dougherty, M , Imperial College, H/707 Huxley Building South Kensington campus, London, SW7 2AZ
Gurnett, D A , University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242-1479
Gombosi, T I , University of Michigan, 1411D Space Research Bldg., Ann Arbor, MI 48109-2143
Hospodarsky, G , University of Iowa, Van Allen Hall, Iowa City, IA 52242-1479
Kurth, W S , University of Iowa, Van Allen Hall, Iowa City, IA 52242-1479
Ridley, A J , University of Michigan, 1411D Space Research Bldg., Ann Arbor, MI 48109-2143
Young, D T , Southwest Research Institute, 6220 Culebra Road P.O. Box 28510, San Antonio, TX 78228-0510

We present results of a 3D global magnetohydrodynamic (MHD) model of the Saturnian system during Cassini's approach to Saturn and its initial orbit. During approach Cassini made measurements of the solar wind conditions upstream of Saturn while at the same time HST measurements were made of the Saturnian aurora and remote sensing measurements of the Saturn Kilometric Radiation (SKR) were made. Using both Cassini data and data propagated from Earth as input to our MHD model, we examine the state of the magnetosphere-ionosphere system for this period. In addition we examine the correlations between remote sensing measurements and the simulations. During orbital insertion and its initial orbit, Cassini measured several crossings of the bow shock and magnetopause of Saturn. Several of these crossing would not have been predicted by Voyager era measurements. Using our MHD model we examine the structure and location of these boundaries and compare them with locations measured by Voyager. Our MHD model includes all the major factors that influence the Kronian magnetosphere: solar wind IMF, planetary rotation, ionospheric conductivities, plasma mass loading and the magnetospheric interaction with Titan.

P53B-05 14:50h

Transport in Saturn's Outer Magnetosphere: Cassini Observations

* Thomsen, M F (mthomsen@lanl.gov) , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Tokar, R L (rlt@lanl.gov) , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Barraclough, B (bbarraclough@lanl.gov) , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Delapp, D (ddelapp@lanl.gov) , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Reisenfeld, D (dan.reisenfeld@umontana.edu) , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Reisenfeld, D (dan.reisenfeld@umontana.edu) , University of Montana, 32 Campus Dr., Missoula, MT 59812 United States
Steinberg, J T (jsteinberg@lanl.gov) , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Fish, B (brian.fish@umontana.edu) , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Fish, B (brian.fish@umontana.edu) , University of Montana, 32 Campus Dr., Missoula, MT 59812 United States
Sittler, E C (Edward.C.Sittler@nasa.gov) , Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
Hill, T W (hill@rice.edu) , Rice University, MS 108, Houston, TX 77251 United States
Young, D T (dyoung@swri.edu) , Southwest Research Institute, 6220 Culebra Rd. P.O. Drawer28510, San Antonio, TX 78228 United States
Crary, F (fcrary@swri.edu) , Southwest Research Institute, 6220 Culebra Rd. P.O. Drawer28510, San Antonio, TX 78228 United States
Andre, N (Nicolas.Andre@cesr.fr) , Centre d'Etude Spatiale des Rayonnements, 14, Avenue Edouard Belin, Toulouse, 31400 France
Coates, A J (ajc@mssl.ucl.ac.uk) , Mullard Space Science Laboratory, Dorking, Holmbury St. Mary, RH5 6NT United Kingdom

In its first pass through Saturn's magnetosphere, the Cassini spacecraft traversed several distinct regions, as previously identified in Pioneer and Voyager data. Beyond approximately 7 RS, the plasma distributions observed by the Cassini Plasma Spectrometer (CAPS) exhibited a very structured character, with cool, dense plasma alternating with hotter, more tenuous material, often on a very short time scale. The properties of this region as seen by CAPS will be described, with particular attention to composition, energy spectra, and flow velocities. The implications of the observations for various models of plasma origin and transport will be examined.

P53B-06 15:05h

Evidence for Alfven Wave Plasma Heating in the Middle Magnetosphere of Saturn

* Burch, J L (jburch@swri.edu) , Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510 United States
Goldstein, J (jgoldstein@swri.edu) , Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510 United States
Young, D T (dyoung@swri.edu) , Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510 United States
Coates, A J (ajc@mssl.ucl.ac.uk) , Mullard Space Science Laboratory, Hombury St. Mary, Dorking, Sur RH5 6NT United Kingdom
Kurth, W S (william-kurth@uiowa.edu) , University of Iowa, 210 VAN, Iowa City, IA 52242 United States
Gurnett, D A (donald-gurnett@uiowa.edu) , University of Iowa, 210 VAN, Iowa City, IA 52242 United States
Dougherty, M K (m.dougherty@imperial.ac.uk) , Imperial College, Blackett Lab, London, SW7 2BZ United Kingdom
Crary, F J (fcrary@swri.edu) , Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510 United States
Hill, T W (hill@rice.edu) , Rice University, P. O. Box 1892, Houston, TX 77005 United States
Andre, N (andre@cesr.fr) , CESR, BP4346 , Toulouse, 31028 France
Sittler, E C (edward.c.sittler@nasa.gov) , NASA GSFC, Code 692, Greenbelt, MD 20771 United States

On July 1, 2004, during the outbound pass following the Saturn orbital insertion of Cassini, the plasma spectrometer (CAPS), magnetometer, and plasma wave instrument observed a region of enhanced wave activity at radial distances between 6 and 7 Rs showing magnetic oscillations near the oxygen cyclotron frequency and lower frequency MHD waves with periods of a few minutes. The three largest low-frequency oscillations were associated on a one-to-one basis with significantly energized electrons and ions with energies ranging from 100s of eV up to several keV. Coincident with these events were deep total density dropouts indicated by the plasma wave data, as well as energy-dispersed energetic ion signatures signifying injections at local times a few hours earlier than the approximately 02 hours LT of the observation point. Centrifugal interchange is likely to be responsible for the apparent mixing of low-density hot plasma with higher density colder plasma. However, there is also evidence for strong Alfven perturbations (dB/B above 0.1) generated possibly by unstable pick-up ion distributions and leading to heating of both ions and electrons via Alfven wave dissipation along the plasma gradient that is observed in this region.

P53B-07 15:20h

Interchange Injection and Drift Dispersion of Hot Plasma in Saturn's Magnetosphere

* Hill, T W (hill@rice.edu) , Rice University, MS 108, Houston, TX 77005 United States
Burch, J L , Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510 United States
Crary, F J , Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510 United States
Thomsen, M F , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Delapp, D , Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
Rymer, A M , Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Sur RH5 6NT United Kingdom
Coates, A J , Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Sur RH5 6NT United Kingdom
Young, D T , Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510 United States
Bolton, S J , Jet Propulsion Laboratory, 4800 Oak Grove Drive, MS 230-205, Pasadena, CA 91109 United States
Sittler, E C , NASA Goddard Space Flight Center, MC 692, Greenbelt, MD 20771 United States

During the first pass of the Cassini-Huygens spacecraft through Saturn's magnetosphere, the Cassini Plasma Spectrometer (CAPS) observed several intermittent occurrences of multi-keV ions and electrons superimposed on a cooler (10 - 100 eV) background plasma. These events are tentatively interpreted as signatures of centrifugally driven interchange motions that inject isolated flux tubes of hot tenuous plasma toward Saturn, similar to injection events reported at Jupiter by the Galileo spacecraft. Both ions and electrons show evidence of energy-time dispersion resulting from adiabatic (gradient-curvature) drift relative to the partially corotating plasma frame of reference. Rotation converts a longitude structure in the rotating frame into a temporal structure in the spacecraft frame. Ions (electrons) drift eastward (westward) relative to the rotating frame with a speed proportional to thermal energy. Thus ions (electrons) display a negative (positive) slope in an energy-time spectrogram. The magnitude of the slope is a measure of the elapsed time since injection. Such events are observed both inbound and outbound in a radial range L = 6 - 10, and are frequently associated with narrow but deep density cavities in the cooler background plasma.

Author(s) (2004), Title, Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract #####-##.