HR: 1340h
AN: P53A-1456    [Abstracts]
TI: Cassini Observations of Co-rotating Heavy Ions Near Saturn's Rings
AU: * Tokar, R L
EM: rlt@lanl.gov
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Young, D T
AF: Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228 United States
AU: Thomsen, M F
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Crary, F J
AF: Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228 United States
AU: Reisenfeld, D B
AF: The University of Montana, 32 Campus Drive, Missoula, MT 59812 United States
AU: Sittler, E C
AF: NASA Goddard Space Flight Center, MC 692, Greenbelt, MD 20771 United States
AU: Johnson, R E
AF: The University of Virginia, Thornton Hall Room B103, Charlottesville, VA 22904 United States
AU: Coates, A J
AF: Mullard Space Science Laboratory University College London, Holmbury St Mary/Dorking , Surrey, RH5 6NT United Kingdom
AU: Gurnett, D A
AF: The University of Iowa, Van Allen Hall, Iowa City, IA 52242 United States
AU: Kurth, W S
AF: The University of Iowa, Van Allen Hall, Iowa City, IA 52242 United States
AU: Hill, T W
AF: Rice University, MS 108, Houston, TX 77005 United States
AU: Steinberg, J T
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Goldstein, R
AF: Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228 United States
AU: McComas, D J
AF: Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228 United States
AB: During Saturn orbit insertion on July 1, 2004, Cassini passed over the B, A, and F rings and the Cassini division before descending, just inside the G ring, through the ring plane. The ion mass spectrometer (IMS), a component of the Cassini plasma spectrometer (CAPS), observed ion flux during this ring plane crossing whenever the instrument viewing was into the co-rotation direction. This occurred in two time intervals, the first from about 03:36 to 03:58 UT (interval 1) and the second from about 04:14 to 04:48 UT (interval 2). Interval 1 is about 0.2 Rs above the A and B rings and the Cassini division. Interval 2 includes the ring plane crossing, inside the G ring. A predictive model that incorporates the IMS view direction and detector response, the spacecraft velocity, and the assumption of co-rotation reproduces many of the salient features in these data. In interval 1, the IMS flux peaks at about 20 and 40 eV in the IMS frame, consistent with co-rotating ions with mass per charge of 16 and 32. It is plausible that these peaks are produced by the heavy ions O+ and O2+, a by product of erosion of the main icy rings. The interval 2 data are similar, with the most intense flux at ~80 eV, extending down to about 40 eV, again in the IMS frame. These energies are also consistent with the co-rotating model predictions for mass per charge values of 16 and 32. Quantitative analysis will be presented at the meeting, including ion identification via the IMS time of flight spectra.
DE: 5421 Interactions with particles and fields
DE: 5465 Rings and dust
DE: 6265 Planetary rings
DE: 6275 Saturn
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting