Numerical modeling of stably and transiently confined energetic heavy ion radiation in the Earth's magnetosphere

Abstract

The Earth's radiation belts contain substantial fluxes of electrons and ions of hydrogen, helium, carbon, nitrogen, oxygen, silicon, iron and 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 instrumentation flown on modern spacecraft have shown that the heavier ion species can be very important and even be the dominant contributor to the Earth's trapped particle environment when relative comparison is viewed in terms of total ion energy rather than energy per nucleon. In such comparisons it is found that helium ions can compete favorably with hydrogen in relative abundance, and that at MeV energies oxygen and even 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.