HR: 1340h
AN: P43A-1032    [Abstracts]
TI: Molecular Oxygen Ions in Saturn's Inner Magnetosphere for the First 24 Cassini Orbits
AU: * Martens, H R
EM: hilarymartens@gmail.com
AF: University of Montana Department of Physics and Astronomy, 32 Campus Drive No. 1082, 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. 1082, Missoula, MT 59812, United States
AU: Williams, J D
EM: john2.williams@umontana.edu
AF: University of Montana Department of Physics and Astronomy, 32 Campus Drive No. 1082, Missoula, MT 59812, United States
AU: Johnson, R E
EM: rej@virginia.edu
AF: University of Virginia Engineering Physics, Thorpe Hall, Charlottesville, VA 22904, United States
AU: Smith, H T
EM: h.todd.smith@jhuapl.edu
AF: University of Virginia Engineering Physics, Thorpe Hall, Charlottesville, VA 22904, United States
AU: Baragiola, R A
EM: rb9a@virginia.edu
AF: University of Virginia Engineering Physics, Thorpe Hall, Charlottesville, VA 22904, United States
AU: Thomsen, M F
EM: mthomsen@lanl.gov
AF: Los Alamos National Laboratory Space and Atmospheric Sciences, 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 West Commerce, San Antonio, TX 78227, United States
AU: Sittler, E C
EM: Edward.C.Sittler@nasa.gov
AF: NASA/Goddard Space Flight Center, 8800 Greeenbelt Road, Greenbelt, MD 20771, United States
AB: We present an analysis of molecular oxygen ions in Saturn\'s inner magnetosphere for the first 24 orbits of Cassini about Saturn. Apoapses of these orbits have local times between 3 and 8 MLT. Data from the Ion Mass Spectrometer (IMS) are summed to achieve better statistics and to bring out features that are otherwise difficult to resolve from an individual orbital pass. In particular, O₂⁺ is well-resolved by this method. Through a combination of peak fitting and baseline subtraction, we isolate O₂⁺ counts from the tail of the W⁺[O⁺, OH⁺, H₂O⁺, H₃O⁺] mass distribution, and from background radiation. We detect O₂⁺ from L = 4.5 out to L = 11 with high confidence, and tentatively detect O₂⁺ inward to L = 3.5 and outward to L = 12. Molecular oxygen ions were initially reported to account for approximately 1-2% of the total ion population in the inner magnetosphere based on IMS data from the inbound Saturn orbital insertion (SOI) pass [Young et al., 2005]. Through refined analysis techniques, we have found O₂⁺ to account for approximately 0.5% of the W⁺ peak at L = 4.5 with only minor fluctuations in relative density out to L = 12. The mean O₂⁺ energy lies above co-rotation, but nevertheless tracks theoretical co-rotation out to L = 9.5, beyond which its energy falls.
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