Bibliography

Formation of the mass density peak at the magnetospheric equator triggered by EMIC waves

Abstract We report a simultaneous observation of two band electromagnetic ion cyclotron (EMIC) waves and toroidal Alfvén waves by the Van Allen Probe mission. Through wave frequency analyses, the mass density ρ is found to be locally peaked at the magnetic equator. Perpendicular fluxes of ions (< 100 eV) increase simultaneously with the appearances of EMIC waves, indicating a heating of these ions by EMIC waves. In addition, the measured ion distributions also support the equatorial peak formation, which accords with the result of the frequency analyses. The formation of local mass density peaks at the equator should be due to enhancements of equatorial ion concentrations, which are triggered by EMIC waves’ perpendicular heating on low energy ions.

Xue, Zuxiang; Yuan, Zhigang; Yu, Xiongdong; Shiyong, Huang; Qiao, Zheng;

Published by: Earth and Planetary Physics      Published on: 03/2021

YEAR: 2021     DOI: https://doi.org/10.26464/epp2021008

Toroidal Alfven waves; EMIC waves; magnetoseismology; equatorial mass density peak; Van Allen Probes

Global distribution of reversed energy spectra of ring current protons based on Van Allen Probes observations

Abstract Energy spectra of ring current protons are crucial to understanding the ring current dynamics. Based on high-quality Van Allen Probes RBSPICE measurements, we investigate the global distribution of the reversed proton energy spectra using the 2013-2019 RBSPICE datasets. The reversed proton energy spectra are characterized by the distinct flux minima around 50 - 100 keV and flux maxima around 200 - 400 keV. Our results show that the reversed proton energy spectrum is prevalent inside the plasmasphere, with the occurrence rates > 90\% at L ∼2 - 4 during geomagnetically quiet periods. Its occurrence also manifests a significant decrease trend with increasing L-shell and enhanced geomagnetic activity. It is indicated that the substorm-associated and/or convection processes are likely to lead to the disappearances of the reversed spectra. These results provide important clues for exploring the underlying physical mechanisms responsible for the formation and evolution of reversed proton energy spectra.

Juan, Yi; Song, Fu; Binbin, Ni; Xudong, Gu; Hua, Man; Xiang, Zheng; Cao, Xing; Shi, Run; Zhao, Yiwen;

Published by: Geophysical Research Letters      Published on: 01/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020GL091559

Van Allen Probes

Prompt emergence and disappearance of EMIC waves driven by the sequentially enhanced solar wind dynamic pressure

Van Allen Probes (VAPs) and multiple ground-based stations simultaneously observed prompt emergences and disappearances of electromagnetic ion cyclotron (EMIC) waves driven by the sequentially enhanced solar wind dynamic pressure in the dayside inner magnetosphere on 6 November 2015. The measured hot protons (> 60 keV) display enhancements of perpendicular temperature during compressions, which provides sufficient temperature anisotropies for the EMIC wave generation so that the calculated linear growth rate also agrees well with the observed wave spectrum. There are bidirectionally propagating EMIC waves observed by VAPs at off equator regions (MLAT from ∼ 13° to ∼ 18°), which indicates local wave excitation under the compressions’ impact. The quick responses of waves and particle distributions to the compressions and decompressions at multiple points in the dayside suggest that the external pressure pulses can be a direct driver for the inner magnetospheric wave evolution and energetic particle dynamics.

Xue, Zuxiang; Yuan, Zhigang; Yu, Xiongdong;

Published by: Geophysical Research Letters      Published on: 12/2020

YEAR: 2020     DOI: https://doi.org/10.1029/2020GL091479

EMIC wave; solar wind dynamic pressure; Magnetospheric compression; Multipoint observations; Van Allen Probes

Characteristics of high energy proton responses to geomagnetic activities in the inner radiation belt observed by the RBSP satellite

High energy trapped particles in the radiation belts constitute potential threats to the functionality of satellites as they enter into those regions. In the inner radiation belt, the characteristics of high-energy (>20MeV) protons variations during geomagnetic activity times have been studied by implementing four-year (2013-2016) observations of the Van Allen probes. An empirical formula has been used to remove the satellite orbit effect, by which proton fluxes have been normalized to the geomagnetic equator. Case studies show that the region of L<1.7 is relatively stable, while L>1.7 is more dynamic and the most significant variation of proton fluxes occurs at L=2.0. The four-year survey at L=2.0 indicates that for every geomagnetic storm, sharp descent in proton fluxes is accompanied by the corresponding depression of SYM-H index, with a one-to-one correspondence, regardless of the storm intensity. Proton fluxes dropouts are synchronous with SYM-H reduction with similar short timescales. Our observational results reveal that high-energy protons in the inner radiation belt are very dynamic, especially for the outer zone of the inner belt, which is beyond our previous knowledge.

Xu, Jiyao; He, Zhaohai; Baker, D.N.; Roth, Ilan; Wang, C.; Kanekal, S.G.; Jaynes, A.N.; Liu, Xiao;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2019

YEAR: 2019     DOI: 10.1029/2018JA026205

geomagnetic activities; high energy proton; Inner radiation belt; one-to-one correspondence; prompt responses; RBSP satellite; Van Allen Probes