title: Maps of hydrogen isotopes at low altitudes in the inner zone from SAMPEX observations.
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 tritum 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.
authors.affiliation: The Aerospace Corporation, Los Angeles, CA 90009, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Looper
authors.forename: J B
authors.initials: JB
authors.lastname: Blake
authors.forename: R A
authors.initials: RA
authors.lastname: Mewaldt
mesh_terms: D016880:Anisotropy; D001267:Atlantic Ocean; D003903:Deuterium; D004583:Electrons; D008280:Magnetics; D011522:Protons; D011834:Radiation Monitoring; D011835:Radiation Protection; D019445:Solar Activity; D013020:South America; D013026:Space Flight / Q000295:instrumentation*; D018531:Spacecraft / Q000295:instrumentation*; D014316:Tritium
chemical_list: D011522:Protons; D014316:Tritium; D003903:Deuterium