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What Causes Radiation Belt Enhancements: A Survey of the Van Allen Probes Era
Author(s) -
Boyd A. J.,
Turner D. L.,
Reeves G. D.,
Spence H. E.,
Baker D. N.,
Blake J. B.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl077699
Subject(s) - van allen radiation belt , physics , acceleration , van allen probes , electron , earth's magnetic field , computational physics , radiation , adiabatic process , fermi acceleration , geophysics , astrophysics , magnetic field , particle acceleration , plasma , nuclear physics , classical mechanics , magnetosphere , quantum mechanics , thermodynamics
We survey radiation belt enhancement events during the Van Allen Probes era to determine what mechanism is the dominant cause of enhancements and where it is most effective. Two primary mechanisms have been proposed: (1) betatron/Fermi acceleration due to the Earthward radial transport of electrons, which produces monotonic gradients in phase space density (PSD), and (2) “local acceleration” due to gyro/Landau resonant interaction with electromagnetic waves, which produces radially localized growing peaks in PSD. To differentiate between these processes, we examine radial profiles of PSD in adiabatic coordinates using data from the Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms satellites for 80 outer belt enhancement events from October 2012 to April 2017 This study shows that local acceleration is the dominant acceleration mechanism for MeV electrons in the outer belt, with 87% of the enhancement events exhibiting growing peaks. The strong correlation of the location of these with geomagnetic activity further supports this conclusion.