Published December 1998 | public
Journal Article

Maps of Hydrogen Isotopes at Low Altitudes in the Inner Zone from SAMPEX Observations

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Abstract

The PET instrument aboard the SAMPEX satellite has provided us with long-term intra-calibrated observations of geomagnetically trapped protons and deuterons in the inner zone, suitable for use in constraining the low-altitude portions of radiation belt models being developed as successors to AP-8. These observations have been summarized elsewhere (Looper et al., 1996). Here we report a detection of geomagnetically-trapped tritium at energies from 14 to 35 MeV/nuc below L = 1.2, at about 1/8 the flux of deuterium previously reported at that location and at similar energy per nucleon. We also demonstrate the utility of the SAMPEX/PET observations for measuring the east-west anisotropy in the trapped particle flux at low altitudes, which is due to displacement of particle gyrocenters from the position of observation in a region of strong flux gradients. This anisotropy is implicitly ignored in omnidirectional radiation-flux models, but it can be important to mission planners considering how to distribute shielding over the surface of oriented spacecraft in low Earth orbit.

Additional Information

© 1998 COSPAR. Published by Elsevier Science Ltd. This work was supported by NASA at The Aerospace Corporation under NASA Cooperative Agreement 26979B and at Caltech under contract NAS5-30704 and grant NAGW-1919.

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August 19, 2023
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October 19, 2023