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- Title
Characteristics of Electron Precipitation During 40 Energetic Electron Injections Inferred via Subionospheric VLF Signal Propagation.
- Authors
Ghaffari, R.; Cully, C. M.; Turner, D. L.; Reeves, G. D.
- Abstract
Energetic electron injection events are associated with energetic electron precipitation (EEP) through possible resonant wave‐particle interactions. Previous studies confirm the impacts of injection‐driven precipitation on observed amplitude/phase of subionospheric VLF (very low frequency) signals transmitted from distant artificial transmitters. Currently, there are substantial uncertainties on precipitation characteristics and flux during injection events. In this work we study 40 injection events selected by Van Allen Probes particle data to investigate the changes in amplitude and phase of VLF signals at ground receivers across Canada during particle injection events. We model the ionospheric effect of the EEP flux to find its impact on VLF propagation and characterize the injection events. Typically, we find a clear phase advance of ~40° in the received VLF signal at Fort Smith (Canada, L = 8) transmitted from U.S. Navy communication transmitter NAA at Maine (USA). Comparing to other VLF transmitter‐receiver paths in North America leads us to conclude that effects are only seen on paths with adequately large range ≫200 km) through L > 7. Modeling the VLF phase change indicates that in the majority of events (>90%), less than 10% of the strong scattering limit inferred from particle flux measurements at the Van Allen Probes is required to obtain the observed VLF phase signature. The median precipitating flux during energetic particle injections is less than 4 × 106 el/cm2 s sr (<10% of the strong scattering rate) for electrons above ~40 keV extracted from trapped particles energy spectrum. This implies that strong scattering is not typical for these 40 selected energetic electron injection events. Key Points: Equatorial chorus triggered by substorm injections drives electron precipitationTypical spatially averaged scattering rate is less than 10% of the strong scattering limit (most events <1% of the strong limit)Precipitating flux during more than 90% of 40 selected energetic electron injections above ~40 keV is <4 × 106 el/cm2 s sr
- Subjects
ELECTRON precipitation; STRATOSPHERE; MAGNETOSPHERE; ION temperature; THERMOSPHERE
- Publication
Journal of Geophysical Research. Space Physics, 2020, Vol 125, Issue 11, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2019JA027233