Abstract
To understand the relationship between generation of electromagnetic ion cyclotron (EMIC) waves and energetic particle injections, we performed a statistical study of EMIC waves associated with and without injections based on the Van Allen Probes (Radiation Belt Storm Probes) and Geostationary Operational Environmental Satellite (GOES; GOES-13 and GOES-15) observations. Using 47 months of observations, we identified wave events seen by the Van Allen Probes relative to the plasmapause and to energetic particle injections seen by GOES-13 and GOES-15 on the nightside. We separated the events into four categories: EMIC waves with (without) injections inside (outside) the plasmasphere. We found that He + EMIC waves have higher occurrence rate inside the plasmasphere, while H + EMIC waves predominantly occur outside the plasmasphere. Meanwhile, the time duration and peak occurrence rate of EMIC waves associated with injections are shorter and limited to a narrower magnetic local time region than those without injections, indicating that these waves have localized source regions. He + EMIC waves inside the plasmasphere associated with injection are usually accompanied by an increase in H + flux within energies of 1–50 keV through all magnetic local time regions, while most wave events outside the plasmasphere show less relationship with H + flux increase. From these observations, we suggest that injected hot ions are the major driver of He + EMIC waves inside the plasmasphere during active time. Expanding plasmasphere during quiet times can provide broad wave source regions for He + EMIC waves on the dayside. However, H + EMIC waves outside the plasmasphere show different characteristics, suggesting that these waves are generated by other processes.
Original language | English (US) |
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Pages (from-to) | 433-450 |
Number of pages | 18 |
Journal | Journal of Geophysical Research: Space Physics |
Volume | 124 |
Issue number | 1 |
DOIs | |
State | Published - Jan 2019 |
Bibliographical note
Publisher Copyright:©2019. The Authors.
Keywords
- EMIC waves associated with and without injections
- relationship between EMIC wave activity and energetic H flux variation
- simultaneous observations using the Van Allen Probes and GOES satellites
- spatial occurrence distributions of EMIC waves