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The global response of relativistic radiation belt electrons to the January 1997 magnetic cloud
Author(s) -
Reeves G. D.,
Baker D. N.,
Belian R. D.,
Blake J. B.,
Cayton T. E.,
Fennell J. F.,
Friedel R. H. W.,
Meier M. M.,
Selesnick R. S.,
Spence H. E.
Publication year - 1998
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 - 10.1029/98gl02509
Subject(s) - van allen radiation belt , physics , electron , magnetosphere , geomagnetic storm , magnetic cloud , geosynchronous orbit , radiation , geophysics , earth's magnetic field , astrophysics , computational physics , solar wind , magnetic field , satellite , plasma , astronomy , coronal mass ejection , nuclear physics , quantum mechanics
In January 1997 a large fleet of NASA and US military satellites provided the most complete observations to date of the changes in >2 MeV electrons during a geomagnetic storm. Observations at geosynchronous orbit revealed a somewhat unusual two‐peaked enhancement in relativistic electron fluxes [ Reeves et al ., 1998]. In the heart of the radiation belts at L ≈ 4, however, there was a single enhancement followed by a gradual decay. Radial profiles from the POLAR and GPS satellites revealed three distinct phases. (1) In the acceleration phase electron fluxes increased simultaneously at L ≈ 4–6. (2) During the passage of the cloud the radiation belts were shifted radially outward and then relaxed earthward. (3) For several days after the passage of the cloud the radial gradient of the fluxes flattened, increasing the fluxes at higher L‐shells. These observations provide evidence that the acceleration of relativistic electrons takes place within the radiation belts and is rapid. Both magnetospheric compression and radial diffusion can cause a redistribution of electron fluxes within the magnetosphere that make the event profiles appear quite different when viewed at different L‐shells.