HR: 1340h
AN: P43A-1033    [Abstracts]
TI: Abundances and Energetics for Water Group Ions in Saturn's Magnetosphere
AU: * Williams, J D
EM: john2.williams@umontana.edu
AF: University of Montana Department of Physics and Astronomy, 32 Campus Drive, No. 1080, Missoula, MT 59812, United States
AU: Reisenfeld, D B
EM: dan.reisenfeld@umontana.edu
AF: University of Montana Department of Physics and Astronomy, 32 Campus Drive, No. 1080, Missoula, MT 59812, United States
AU: Martens, H R
EM: hilarymartens@gmail.com
AF: University of Montana Department of Physics and Astronomy, 32 Campus Drive, No. 1080, Missoula, MT 59812, United States
AU: Johnson, R E
EM: rej@virginia.edu
AF: University of Virginia Engineering Physics, Thornton Hall, Charlottesville, VA 22904, United States
AU: Smith, H T
EM: H.Todd.Smith@jhuapl.edu
AF: University of Virginia Engineering Physics, Thornton Hall, Charlottesville, VA 22904, United States
AU: Thomsen, M F
EM: mthomsen@lanl.gov
AF: Los Alamos National Laboratory Space and Atmospheric Science Group, NIS-1, Los Alamos, NM 87545, United States
AU: Young, D T
EM: dyoung@swri.edu
AF: Southwest Research Institute Division of Space Science and Engineering, 9503 W.Commerce, San Antonio, TX 78227, United States
AU: Sittler, E C
EM: edward.c.sittler@nasa.gov
AF: NASA/Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, United States
AU: Baragiola, R A
EM: rb9a@virginia.edu
AF: University of Virginia Engineering Physics, Thornton Hall, Charlottesville, VA 22904, United States
AB: We present magnetospheric ion composition results obtained from the Cassini Plasma Spectrometer (CAPS) time-of-flight instrument for orbits over a two year period in which Cassini was almost entirely in the dawn magnetosphere. Water group ions (O⁺,\ OH⁺,\ H₂O⁺,\ H₃O⁺; or collectively,\ W⁺) dominate over H⁺ in the inner magnetosphere to approximately L = 20. W⁺ ions are seen sporadically out to L = 36. Within the water group,\ O⁺ dominates at all distances, H₃O⁺ is second to O⁺ for L < 5, H₂O⁺ is second from L = 5 to L = 8, and OH⁺ is second for L > 10. The density of H₃O⁺ peaks at L = 3 and drops off rapidly, becoming undetectable beyond L = 11 . The W⁺ group plasma has both a core and a high energy tail; characteristics of each component have a separate dynamical history and vary as a function of radial distance. The ratio of number densities for the tail to the core is seen to have a broad peak between 10 < L < 20,\ indicating a source mechanism in this location,\ possibly the ring current. Finally,\ we show how the time variation of W⁺ number densities at specific locations is indicative of bursty events in the magnetosphere.
DE: 2730 Magnetosphere: inner
DE: 5709 Composition (1060)
DE: 5737 Magnetospheres (2756)
DE: 5780 Tori and exospheres
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting