Energetic Electron Precipitation: Multievent Analysis of Its Spatial Extent During EMIC Wave Activity

Electromagnetic ion cyclotron (EMIC) waves can drive precipitation of tens of keV protons and relativistic electrons, and are a potential candidate for causing radiation belt flux dropouts. In this study, we quantitatively analyze three cases of EMIC‐driven precipitation, which occurred near the dus...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2019-04, Vol.124 (4), p.2466-2483
Main Authors: Capannolo, L., Li, W., Ma, Q., Shen, X.‐C., Zhang, X.‐J., Redmon, R. J., Rodriguez, J. V., Engebretson, M. J., Kletzing, C. A., Kurth, W. S., Hospodarsky, G. B., Spence, H. E., Reeves, G. D., Raita, T.
Format: Article
Language:English
Subjects:
ASTRONOMY AND ASTROPHYSICS
Cyclotrons
Electron precipitation
Electrons
EMIC waves
energetic electron precipitation
Equator
Heliospheric physics
Herbivores
Ion cyclotron waves
Low earth orbits
Magnetometers
Magnetospheres
Magnetospheric Physics
Magnetospheric waves
Pitch (inclination)
pitch angle scattering
POES satellites
Proton precipitation
quasi‐linear theory
Radiation
radiation belts dropouts
Relativism
Relativistic effects
Satellite observation
Satellites
Scattering
Spatial analysis
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Summary:Electromagnetic ion cyclotron (EMIC) waves can drive precipitation of tens of keV protons and relativistic electrons, and are a potential candidate for causing radiation belt flux dropouts. In this study, we quantitatively analyze three cases of EMIC‐driven precipitation, which occurred near the dusk sector observed by multiple Low‐Earth‐Orbiting (LEO) Polar Operational Environmental Satellites/Meteorological Operational satellite programme (POES/MetOp) satellites. During EMIC wave activity, the proton precipitation occurred from few tens of keV up to hundreds of keV, while the electron precipitation was mainly at relativistic energies. We compare observations of electron precipitation with calculations using quasi‐linear theory. For all cases, we consider the effects of other magnetospheric waves observed simultaneously with EMIC waves, namely, plasmaspheric hiss and magnetosonic waves, and find that the electron precipitation at MeV energies was predominantly caused by EMIC‐driven pitch angle scattering. Interestingly, each precipitation event observed by a LEO satellite extended over a limited L shell region (ΔL ~ 0.3 on average), suggesting that the pitch angle scattering caused by EMIC waves occurs only when favorable conditions are met, likely in a localized region. Furthermore, we take advantage of the LEO constellation to explore the occurrence of precipitation at different L shells and magnetic local time sectors, simultaneously with EMIC wave observations near the equator (detected by Van Allen Probes) or at the ground (measured by magnetometers). Our analysis shows that although EMIC waves drove precipitation only in a narrow ΔL, electron precipitation was triggered at various locations as identified by POES/MetOp over a rather broad region (up to ~4.4 hr MLT and ~1.4 L shells) with similar patterns between satellites. Key Points We show three cases of proton and relativistic electron precipitation observed simultaneously with EMIC waves EMIC‐driven precipitation was observed by POES/MetOp satellites at different locations over a broad L‐MLT region Each precipitation event extended over ΔL ~ 0.3 on average, showing that wave‐driven pitch angle scattering is localized
ISSN:2169-9380
2169-9402
DOI:10.1029/2018JA026291