Oxygen Ion Dynamics in the Earth's Ring Current: Van Allen Probes Observations

Chao Yue, Jacob Bortnik, Wen Li, Qianli Ma, Chih Ping Wang, Richard M. Thorne, Larry Lyons, Geoffrey D. Reeves, Harlan E. Spence, Andrew J. Gerrard, Matina Gkioulidou, Donald G. Mitchell

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Oxygen (O+) enhancements in the inner magnetosphere are often observed during geomagnetically active times, such as geomagnetic storms. In this study, we quantitatively examine the difference in ring current dynamics with and without a substantial O+ ion population based on almost 6 years of Van Allen Probes observations. Our results have not only confirmed previous finding of the role of O+ ions to the ring current but also found that abundant O+ ions are always present during large storms when sym-H < −60 nT without exception, while having the pressure ratio (ℛ) between O+ and proton (H+) larger than 0.8 and occasionally even larger than 1 when L < 3. Simultaneously, the pressure anisotropy decreases with decreasing sym-H and increasing L shell. The pressure anisotropy decrease during the storm main phase is likely related to the pitch angle isotropization processes. In addition, we find that ℛ increases during the storm main phase and then decreases during the storm recovery phase, suggesting faster buildup and decay of O+ pressure compared to H+ ions, which are probably associated with some species dependent source and/or energization as well as loss processes in the inner magnetosphere.

Original languageEnglish (US)
Pages (from-to)7786-7798
Number of pages13
JournalJournal of Geophysical Research: Space Physics
Volume124
Issue number10
DOIs
StatePublished - Oct 1 2019

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Geophysics

Keywords

  • Van Allen Probe
  • ion dunamics
  • oxygen ions
  • ring current
  • storm time

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