Initial Measurements of O-ion and He-ion Decay Rates Observed from the Van Allen Probes RBSPICE Instrument

TitleInitial Measurements of O-ion and He-ion Decay Rates Observed from the Van Allen Probes RBSPICE Instrument
Publication TypeJournal Article
Year of Publication2014
AuthorsGerrard, A, Lanzerotti, L, Gkioulidou, M, Mitchell, D, Manweiler, J, Bortnik, J, Keika, K
JournalJournal of Geophysical Research: Space Physics
Volume119
Issue11
Start Page8813
Date Published11/2014
Keywordsinner magnetosphere; ion decay rates; Spacecraft measurements; Van Allen Probes
AbstractH-ion (~45-keV to ~600-keV), He-ion (~65-keV to ~520-keV), and O-ion (~140-keV to ~1130-keV) integral flux measurements, from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft B, are reported. These abundance data form a cohesive picture of ring current ions during the first nine months of measurements. Furthermore, the data presented herein are used to show injection characteristics via the He-ion/H-ion abundance ratio and the O-ion/H-ion abundance ratio. Of unique interest to ring current dynamics are the spatial-temporal decay characteristics of the two injected populations. We observe that He-ions decay more quickly at lower L-shells, on the orderof ~0.8-day at L-shells of 3–4, and decay more slowly with higher L-shell, on the order of ~1.7-days at L-shells of 5–6. Conversely, O-ions decay very rapidly (~1.5-hours) across all L-shells. The He-ion decay time are consistent with previously measured and calculated lifetimes associated with charge exchange. The O-ion decay time is much faster than predicted and is attributed to the inclusion of higher energy (>500-keV) O-ions in our decay rate estimation. We note that these measurements demonstrate a compelling need for calculation of high energy O-ion loss rates, which have not been adequately studied in the literature to date.
URLhttp://doi.wiley.com/10.1002/2014JA020374
DOI10.1002/2014JA020374
Short TitleJ. Geophys. Res. Space Physics


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