Initial measurements of O-ion and He-ion decay rates observed from the Van Allen probes RBSPICE instrument

Andrew Gerrard, Louis Lanzerotti, Matina Gkioulidou, Donald Mitchell, Jerry Manweiler, Jacob Bortnik, Kunihiro Keika

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

H-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 9 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 order of ∼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 h) 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.

Original languageEnglish (US)
Pages (from-to)8813-8819
Number of pages7
JournalJournal of Geophysical Research: Space Physics
Volume119
Issue number11
DOIs
StatePublished - Nov 2014

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Geophysics

Keywords

  • Van Allen Probes
  • inner magnetosphere
  • ion decay rates
  • spacecraft measurements

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