Episodic Occurrence of Field‐Aligned Energetic Ions on the Dayside
Name
Geophysical Research Letters - 2020 - Yue - Episodic Occurrence of Field‐Aligned Energetic Ions on the Dayside.pdf
Description
Published version
Size
4.12 MB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Yue, Chao
Bortnik, Jacob
Zou, Shasha
Nishimura, Yukitoshi
Foster, John C
Coppeans, Thomas
Ma, Qianli
Zong, Qiugang
Hull, AJ
Henderson, Mike
Date Issued
January 9, 2020
Journal
Geophysical Research Letters
Publisher
American Geophysical Union
Citation
Yue, C., Bortnik, J., Zou, S., Nishimura, Y., Foster, J. C., Coppeans, T., et al. (2020). Episodic Occurrence of Field-Aligned Energetic Ions on the Dayside. Geophysical Research Letters, 47, e2019GL086384.
Version
Final published version
Abstract
The tens of kiloelectron volt ions observed in the ring current region at L ~ 3–7 generally have pancake pitch angle distributions, that is, peaked at 90°. However, in this study, by using the Van Allen Probe observations on the dayside, unexpectedly, we have found that about 5% time, protons with energies of ~30 to 50 keV show two distinct populations, having an additional field-aligned population overlapping with the original pancake population. The newly appearing field-aligned populations have higher occurrence rates at ~12–16 magnetic local time during geomagnetically active times. In particular, we have studied eight such events in detail and found that the source regions are located around 12 to 18 magnetic local time which coincides with our statistical result. Based on the ionospheric and geosynchronous observations, it is suggested that these energetic ions with field-aligned pitch angle distributions probably are accelerated near postnoon in association with ionospheric disturbances that are triggered by tail injections.
MIT Department
Haystack Observatory
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DOI of Published Version
https://doi.org/10.1029/2019gl086384
