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Observations of molecular oxygen ions in Saturn's inner magnetosphere
Author(s) -
Martens Hilary R.,
Reisenfeld Daniel B.,
Williams John D.,
Johnson Robert E.,
Smith H. Todd
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl035433
Subject(s) - magnetosphere , saturn , ion , physics , population , magnetosphere of saturn , oxygen , atomic physics , astrophysics , plasma , magnetopause , nuclear physics , planet , demography , quantum mechanics , sociology
We present an analysis of molecular oxygen ion (O 2 + ) abundance in Saturn's inner magnetosphere based on observations made with the Cassini Plasma Spectrometer (CAPS). Using data summed over 23 orbits, we resolve and isolate O 2 + counts from the tail of the water group ion mass distribution (W + [O + , OH + , H 2 O + , H 3 O + ]) and from background sources. O 2 + was initially estimated at ∼1–2% of the total ion population in the inner magnetosphere based on CAPS data from the Saturn orbital insertion pass. Through refined analysis techniques, we have found O 2 + to account for just above 0.3% of all W + ions at L = 4.5, with only minor fluctuations in relative density out to L = 7.5 − 8.0. Beyond L = 7.5, the relative O 2 + /W + abundance exhibits a statistically significant increase through L = 10.5, which may indicate a neutral O 2 source in the vicinity of Rhea.