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Observations of the inner radiation belt: CRAND and trapped solar protons
Author(s) -
Selesnick R. S.,
Baker D. N.,
Jaynes A. N.,
Li X.,
Kanekal S. G.,
Hudson M. K.,
Kress B. T.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020188
Subject(s) - proton , physics , van allen radiation belt , equator , pitch angle , radiation trapping , radiation , cosmic ray , neutron , trapping , atomic physics , nuclear physics , magnetosphere , astronomy , latitude , plasma , ecology , biology
Measurements of inner radiation belt protons have been made by the Van Allen Probes Relativistic Electron‐Proton Telescopes as a function of kinetic energy (24 to 76 MeV), equatorial pitch angle, and magnetic L shell, during late 2013 and early 2014. A probabilistic data analysis method reduces background from contamination by higher‐energy protons. Resulting proton intensities are compared to predictions of a theoretical radiation belt model. Then trapped protons originating both from cosmic ray albedo neutron decay (CRAND) and from trapping of solar protons are evident in the measured distributions. An observed double‐peaked distribution in L is attributed, based on the model comparison, to a gap in the occurrence of solar proton events during the 2007 to 2011 solar minimum. Equatorial pitch angle distributions show that trapped solar protons are confined near the magnetic equator but that CRAND protons can reach low altitudes. Narrow pitch angle distributions near the outer edge of the inner belt are characteristic of proton trapping limits.