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Multiyear Measurements of Radiation Belt Electrons: Acceleration, Transport, and Loss
Journal article   Open access   Peer reviewed

Multiyear Measurements of Radiation Belt Electrons: Acceleration, Transport, and Loss

Daniel N Baker, Vaughn Hoxie, Hong Zhao, Allison N Jaynes, Shri Kanekal, Xinlin Li and Scot Elkington
Journal of geophysical research. Space physics, Vol.124(4), pp.2588-2602
04/2019
DOI: 10.1029/2018JA026259
PMCID: PMC6582599
PMID: 31245234
url
https://doi.org/10.1029/2018JA026259View
Published (Version of record) Open Access

Abstract

In addition to clarifying morphological structures of the Earth's radiation belts, it has also been a major achievement of the Van Allen Probes mission to understand more thoroughly how highly relativistic and ultrarelativistic electrons are accelerated deep inside the radiation belts. Prior studies have demonstrated that electrons up to energies of 10 megaelectron volts (MeV) can be produced over broad regions of the outer Van Allen zone on timescales of minutes to a few hours. It often is seen that geomagnetic activity driven by strong solar storms (i.e., coronal mass ejections, or CMEs) almost inexorably leads to relativistic electron production through the intermediary step of intense magnetospheric substorms. In this study, we report observations over the 6‐year period 1 September 2012 to 1 September 2018. We focus on data about the relativistic and ultrarelativistic electrons (E≥5 MeV) measured by the Relativistic Electron‐Proton Telescope sensors on board the Van Allen Probes spacecraft. This work portrays the radiation belt acceleration, transport, and loss characteristics over a wide range of geomagnetic events. We emphasize features seen repeatedly in the data (three‐belt structures, “impenetrable” barrier properties, and radial diffusion signatures) in the context of acceleration and loss mechanisms. We especially highlight solar wind forcing of the ultrarelativistic electron populations and extended periods when such electrons were absent. The analysis includes new display tools showing spatial features of the mission‐long time variability of the outer Van Allen belt emphasizing the remarkable dynamics of the system. Key Points Essential factors are plentiful substorm “seed particles” and high‐speed (V > 500 km/s) solar wind forcing The entire relativistic electron population can be wiped out in a few hours by shock wave impact but can rapidly be replenished Very long intervals have been observed without multimegaelectron volt electrons in the outer belt due to low solar wind driving
 convection electric field energetic particle deep penetration low L region radiation belts Van Allen Probes

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