NUMERICAL MODELING OF STABLY AND TRANSIENTLY CONFINED ENERGETIC HEAVY-ION RADIATION IN THE EARTHS MAGNETOSPHERE

The Earth's radiation belts contain substantial fluxes of electrons an d ions of hydrogen, helium, carbon, nitrogen, oxygen, silicon, iron an d other ion species. In the early space exploration era it was thought that hydrogen ions (protons) were the dominant ion species with only minor contributions of helium and heavier ions. Sophisticated instrume ntation flown on modern spacecraft have shown that the heavier ion spe cies can be very important and even be the dominant contributor to the Earth's trapped particle environment when relative comparison is view ed in terms of total ion energy rather than energy per nucleon. In suc h comparisons it is found that helium ions can compete favorably with hydrogen in relative abundance, and that at MeV energies oxygen and ev en iron ions can be very significant. In contrast, comparison of ionic composition generally tends to favor protons in the upper keV and MeV energy ranges when energy per nucleon is considered. Copyright (C) 19 96 Elsevier Science Ltd.