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- Title
The Effect of Energetic Ion Dispersionless Injections on the Ring Current Dynamics.
- Authors
Zhuang, Yan; Yue, Chao; Zong, Qiu‐Gang; Zhou, Xu‐Zhi; Fu, Haobo; Mitchell, Donald G.; Gkioulidou, M.; Cooper, Matthew
- Abstract
Energetic particle injections, usually observed as sudden flux enhancements of charged particles from tens to hundreds of keV, are one of the main mechanisms for ring current enhancement. In this study, we statistically analyzed the influence of dispersionless injections on Earth's ring current based on the measurements of radiation belt storm probes ion composition experiment onboard Van Allen Probes from 2013 to 2019. We identified 813 dispersionless proton injection events, which are mainly in the pre‐midnight sector. With a greater SuperMAG electrojet index (SME), the observed injections extend to lower L shells. Meanwhile, Helium (He+) and oxygen (O+) ions experience almost simultaneous injections with protons. Superposed epoch results show that ion energy densities enhance significantly after injections. As SMEmax increases, the ring current energy densities of all three species are increasing, and the magnitude of the enhancements, defined as the ratio of the energy densities after and before the injection, hardly changes for protons (∼2.0) and He+ ions (∼2.0) but increases for O+ ions (2.6 and 3.0 for SMEmax < 1,000 nT and SMEmax ≥ 1,000 nT, respectively), suggesting the contribution of O+ ions to ring current becomes more significant during super substorms. With proton injections, the dawn‐dusk electric field is enhanced sharply to twice as large as before. Simultaneously, there is a dip followed by gradual dipolarization of the magnetic fields. Moreover, particle anisotropies increase following ion injections, which may generate electromagnetic ion cyclotron waves. These statistical results indicate that ion injections during substorms contribute significantly to the ring current. Plain Language Summary: Ring current is one of the most significant current systems in the Earth's magnetosphere, and substorm injections are major mechanisms for ring current enhancement. Dispersionless injections are considered to be in the source region, characterized by simultaneous sudden flux enhancements of charged particles from tens to hundreds of keV. Using data from Van Allen Probes, we statistically surveyed the impact of dispersionless injections on the ring current from 2013 to 2019. We found that injection events are mainly at the pre‐midnight sector, and the depth increases with stronger substorms. Along with proton injections, He+ and O+ ions are also simultaneously injected into the ring current region. The ion injections increase the energy densities of the ring current significantly, with energy densities of H+ and He+ ions increasing to twice as much as before and O+ ions rising to over 2.6 times the level before injections. Following ion injections, the configurations of the electric and magnetic fields in the ring current region change, and particle anisotropies that may generate electromagnetic ion cyclotron waves increase, leading to the loss or acceleration of inner magnetospheric particles. Key Points: We analyze the energetic particle dispersionless injections inside the geosynchronous orbit from 2013 to 2019 through RBSP observationsThe contributions of H+, He+, and O+ ion injections on the energy densities of ring current are investigated under different conditionsThe configuration of the electromagnetic fields and particle anisotropies in the ring current region change with ion injections
- Subjects
ION energy; GEOSYNCHRONOUS orbits; ELECTROMAGNETIC fields; EARTH currents; ION acoustic waves
- Publication
Journal of Geophysical Research. Space Physics, 2023, Vol 128, Issue 2, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2022JA030914