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Acceleration of radiation belt electrons and the role of the average interplanetary magnetic field B z component in high‐speed streams
Author(s) -
Souza V. M.,
Lopez R. E.,
Jauer P. R.,
Sibeck D. G.,
Pham K.,
Da Silva L. A.,
Marchezi J. P.,
Alves L. R.,
Koga D.,
Medeiros C.,
Rockenbach M.,
Gonzalez W. D.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024187
Subject(s) - physics , van allen radiation belt , magnetosphere , electron , whistler , solar wind , van allen probes , interplanetary magnetic field , interplanetary spaceflight , computational physics , astrophysics , geophysics , magnetic field , nuclear physics , quantum mechanics
In this study we examine the recovery of relativistic radiation belt electrons on 15–16 November 2014, after a previous reduction in the electron flux resulting from the passage of a corotating interaction region (CIR). Following the CIR, there was a period of high‐speed streams characterized by large, nonlinear fluctuations in the interplanetary magnetic field (IMF) components. However, the outer radiation belt electron flux remained at a low level for several days before it increased in two major steps. The first increase is associated with the IMF background field turning from slightly northward on average to slightly southward on average. The second major increase is associated with an increase in the solar wind velocity during a period of southward average IMF background field. We present evidence that when the IMF B z is negative on average, the whistler mode chorus wave power is enhanced in the outer radiation belt, and the amplification of magnetic integrated power spectral density in the ULF frequency range, in the nightside magnetosphere, is more efficient as compared to cases in which the mean IMF B z is positive. Preliminary analysis of the time evolution of phase space density radial profiles did not provide conclusive evidence on which electron acceleration mechanism is the dominant. We argue that the acceleration of radiation belt electrons requires (i) a seed population of keV electrons injected into the inner magnetosphere by substorms and both (ii) enhanced whistler mode chorus waves activity as well as (iii) large‐amplitude MHD waves.