Premium
The elemental composition of low altitude 0.49 MeV/nucleon trapped equatorial ions
Author(s) -
Mazur J. E.,
Mason G. M.,
Greenspan M. 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 - 10.1029/98gl00465
Subject(s) - van allen radiation belt , physics , ion , population , equator , atomic physics , altitude (triangle) , cosmic ray , nucleon , ring current , earth's magnetic field , magnetosphere , nuclear physics , astronomy , latitude , magnetic field , geometry , plasma , demography , mathematics , quantum mechanics , sociology
Using instrumentation on board the SAMPEX satellite at ∼600 km we present new measurements of the composition of a population of >0.49 MeV/nucleon ions that are trapped near the geomagnetic equator. These ions gain access to the SAMPEX orbit as neutral particles via charge exchange collisions that continually occur within the higher altitude radiation belt and contribute to the decay of storm‐time enhanced ring current. At low altitudes a second charge exchange collision produces a trapped ion belt near the magnetic equator. This belt is ephemeral, as it is necessarily observed on drift paths that reach deep into the atmosphere near the South Atlantic Anomaly. We find the relative abundances of H:He:C:O:Ne‐Fe are 7000 : 7.5 : 0.14 : 1.0 : 0.03. The low altitude particles are underabundant in Z>8 ions compared to the radiation belt, possibly because the radiation belt Z>8 ions may not be stably trapped once they charge exchange to higher rigidities. We cannot rule out the possible contribution of trapped anomalous cosmic rays to the heavy ions observed above 0.49 MeV/nucleon in this low altitude population.