HR: 0800h
AN: P51A-1406    [Abstracts]
TI: The Ring-dust Plasma Torus as Observed by Cassini RPWS
AU: * Wahlund, J
EM: jwe@irfu.se
AF: Swedish Institute of Space Physics, Box 537, Uppsala, SE-751 21 Sweden
AU: Bostr”m, R
EM: rb@irfu.se
AF: Swedish Institute of Space Physics, Box 537, Uppsala, SE-751 21 Sweden
AU: Eriksson, A I
EM: aie@irfu.se
AF: Swedish Institute of Space Physics, Box 537, Uppsala, SE-751 21 Sweden
AU: Gustafsson, G
EM: gg@irfu.se
AF: Swedish Institute of Space Physics, Box 537, Uppsala, SE-751 21 Sweden
AU: Morooka, M
EM: michiko@irfu.se
AF: Swedish Institute of Space Physics, Box 537, Uppsala, SE-751 21 Sweden
AU: Gurnett, D A
EM: dag@space.physics.uiowa.edu
AF: Department of Physics and Astronomy, University of Iowa, Iowa City, Ia 52242 United States
AU: Kurth, W S
EM: wsk@space.physics.uiowa.edu
AF: Department of Physics and Astronomy, University of Iowa, Iowa City, Ia 52242 United States
AU: Desch, M
EM: michael.desch@nasa.gov
AF: Goddard Space Flight Centre, Code 695, NASA/GSFC, Greenbelt, MD 20771 United States
AU: Waite, H J
EM: hunterw@umich.edu
AF: Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Space Research Building, 2455 Hayward, Ann Arbor, Michigan 4 United States
AU: Yelle, R
EM: yelle@lpl.arizona.edu
AF: Department of Planetary Sciences, University of Arizona, 1629 E. University Blvd, Tucson, AZ 85721-0 United States
AU: Muller-Wodarg, I
EM: i.mueller-wodarg@imperial.ac.uk
AF: Space and Atmospheric Physics, Imperial College London, London, x United Kingdom
AB: We present new results indicating that ring-dust is a major plasma source for the magnetosphere of Saturn. This study of the cold plasma near the ring plane of Saturn is based on observations by the Radio and Plasma Wave Science (RPWS) instruments on board the Cassini spacecraft. A dense dusty ring plasma was detected both during the inbound and outbound crossings of the ring plane. The Langmuir probe and plasma emission measurements indicated an increase of the plasma density up to 100 cm(-3), and the dense plasma was centred around the maximum count rate of impacting micrometer sized dust particles on the spacecraft. Furthermore, the Langmuir probe observations pointed toward a cold plasma population with electron temperatures around 0.5-1 eV and ion temperatures well below 100 eV. The ram current to the spherical probe indicated an average ion mass between 20-40 amu, which was confirmed by the INMS instrument that the dominant ion was molecular oxygen (O2+). The plasma density decreased to very low values when Cassini passed over (northward) the visible rings of Saturn, which suggest that the ring-plasma is most dense just outside the F ring. The visible rings presumably absorb magnetically mirrored charged particles on conjugate magnetic field lines, and hence the plasma density is low inside the F-ring. Except during the Saturn Orbit Injection (SOI) spacecraft burn, the spacecraft potential was determined under the rings. From the information of the thermal plasma and the spacecraft potential over the rings we make an attempt to infer the electric charge of dust particles in the rings themselves. The Langmuir probe measurements therefore may provide observational constraints on the problem how the co-rotating magnetosphere of the planet Saturn affect the dynamics and structure of ring-dust.
DE: 5759 Rings and dust
DE: 5780 Tori and exospheres
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2732 Magnetosphere interactions with satellites and rings
DE: 2756 Planetary magnetospheres (5443, 5737, 6030)
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting