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

Document Type

Article

Publication Date

10-1-2019

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.

Identifier

85074101207 (Scopus)

Publication Title

Journal of Geophysical Research Space Physics

External Full Text Location

https://doi.org/10.1029/2019JA026801

e-ISSN

21699402

ISSN

21699380

First Page

7786

Last Page

7798

Issue

10

Volume

124

Grant

NASA HTIDeS NNX16AG21G

Fund Ref

Alfred P. Sloan Foundation

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