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- Title
On the Spatial and Temporal Evolution of EMIC Wave‐Driven Relativistic Electron Precipitation: Magnetically Conjugate Observations From the Van Allen Probes and CALET.
- Authors
Blum, L. W.; Bruno, A.; Capannolo, L.; Ma, Q.; Kataoka, R.; Torii, S.; Baishev, D.
- Abstract
Electromagnetic ion cyclotron (EMIC) waves have been shown to be able to drive strong electron precipitation, particularly at MeV energies. However, the spatio‐temporal evolution of both the waves and the resulting precipitation is still not well understood. Here we investigate the evolution of relativistic electron precipitation driven by EMIC waves through combined observations from the Van Allen Probes and the CALorimetric Electron Telescope experiment onboard the International Space Station. Two case studies are examined where EMIC waves near the magnetic equator and precipitation at low altitude were detected in close magnetic conjunction, both of which were confined to narrow radial regions but persisted multiple hours. These observations, combined with quasilinear calculations, confirm that long‐lived EMIC waves can drive hours‐long MeV electron precipitation loss. However, the magnitude of the precipitation varied significantly during one of the events, as resonance conditions, particularly plasma density, evolved. Plain Language Summary: Earth's radiation belts contain high energy electrons, hazardous to both humans and electronics in space. This population exhibits dramatic variations in time, showing both rapid enhancements as well as depletions. One potential cause of these depletions is the loss of these electrons into Earth's atmosphere, through a process termed "precipitation." While precipitation has been shown to contribute to the global dynamics of the radiation belts, when, where, and how much loss it contributes are still open questions. This study examines the spatial and temporal evolution of radiation belt electron precipitation as well as the electromagnetic waves that can cause it. Key Points: Two events are examined where electromagnetic ion cyclotron waves and MeV electron precipitation were observed in close magnetic conjunctionWave and associated precipitation regions were radially confined but lasted multiple hoursPrecipitation magnitude and energy spectrum varied over time due to an evolving plasmasphere and trapped electron population
- Subjects
RELATIVISTIC electrons; RADIATION belts; SPATIOTEMPORAL processes; TERRESTRIAL radiation; ION acoustic waves
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 5, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL107087