Simulation of a Rapid Dropout Event for Highly Relativistic Electrons with the RBE Model

A flux dropout is a sudden and sizable decrease in the energetic electron population of the outer radiation belt on the time scale of a few hours. We simulated a flux dropout of highly relativistic 2.5 MeV electrons using the Radiation Belt Environment model, incorporating the pitch angle diffusion...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2016-05, Vol.121 (5), p.4092-4102
Main Authors: Kang, S-B., Fok, M.-C., Glocer, A., Min, K.-W., Choi, C.-R., Choi, E., Hwang, J.
Format: Article
Language:English
Subjects:
Computer simulation
Cyclotrons
dropout
Dropouts
Electron density
Electron flux
EMIC waves
Environment models
Fluctuations
Flux
Geomagnetic storms
Geomagnetism
Ion cyclotron waves
KP index
Magnetic storms
Magnetopause
Magnetospheres
Mathematical models
Outer radiation belt
Pitch (inclination)
Pitch angle
pitch angle scattering
Radiation
RBE model
Relativism
Relativistic effects
relativistic electron
Spacecraft
Storms
Wave scattering
Waves
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Summary:A flux dropout is a sudden and sizable decrease in the energetic electron population of the outer radiation belt on the time scale of a few hours. We simulated a flux dropout of highly relativistic 2.5 MeV electrons using the Radiation Belt Environment model, incorporating the pitch angle diffusion coefficients caused by electromagnetic ion cyclotron (EMIC) waves for the geomagnetic storm events of 23-26 October 2002. This simulation showed a remarkable decrease in the 2.5 MeV electron flux during main phase of the storm, compared to those without EMIC waves. This decrease was independent of magnetopause shadowing or drift loss to the magnetopause. We suggest that the flux decrease was likely to be primarily due to pitch angle scattering to the loss cone by EMIC waves. Furthermore, the 2.5 MeV electron flux calculated with EMIC waves correspond very well with that observed from Solar Anomalous and Magnetospheric Particle EXplorer spacecraft. EMIC wave scattering is therefore likely one of the key mechanisms to understand flux dropouts. We modeled EMIC wave intensities by the Kp index. However, the calculated dropout is a several hours earlier than the observed one. We propose that Kp is not the best parameter to predict EMIC waves.
ISSN:2169-9380
2169-9402
DOI:10.1002/2015JA021966