Hydrogen and helium isotope inner radiation belts in the Earth's magnetosphere

Abstract

Abstract. Radial transport theory for inner radiation zone MeV ions has been extended by combining radial diffusive transport and losses due to Coulomb friction with local generation of D, T and 3He ions from nuclear reactions taking place on the inner edge of the inner radiation zone. Based on interactions between high energy trapped protons and upper atmospheric constituents we have included a nuclear reaction yield D, T and 3He flux source that was numerically derived from a nuclear reaction model code originally developed at the Institute of Nuclear Researches in Moscow, Russia. Magnetospheric transport computations have been made covering the L-shell range L=1.0–1.6. The resulting MeV energy D, T and 3He ion flux distributions show a strong influence of the local nuclear source mechanism on the inner zone energetic D, T and 3He ion content.Key words: Atmospheric composition and structure (Thermosphere-composition and chemistry) · Magnetospheric physics (Energetic particles · trapped).

Geomagnetically trapped light isotopes observed with the detector NINA

“…The deuterium flux shows a reasonable agreement with calculations; a deeper analysis, nevertheless, reveals that the sum of the p + He and p + O reaction does not provide a sufficient deuterium intensity, as already pointed out by Selesnick and Mewaldt [1996] and Pugacheva et al [1998], who compared calculations with SAMPEX data. Figure 6 presents, in fact, fluxes averaged over a L shell interval, but fluxes around the boundary of radiation belts have a very steep dependence on the L shell value.…”

“…[36] NINA measured 2 H/ 3 H ratio at 10 MeV/n is $4, roughly 2 times lower than that measured by SAMPEX at higher energies, but this may be explained by the differing production cross sections of 2 H and 3 H as a function of energy, inferred for instance by data in the work of Wu et al [1979]. From Figure 6 it is visible that the 2 H/ 3 H ratio calculated by Pugacheva et al [1998] increases with energy, but its minimum value is $30.…”

“…(left) Calculations for secondary production of deuterium at different energies for different reactions [ Selesnick and Mewaldt , 1996]. (right) Experimental deuterium flux as a function of L shell measured by NINA in the energy range 7–13 MeV nucleon −1 , together with calculations from the combined action of secondary production and radiation belt radial diffusion at 10 MeV made by [ Pugacheva et al , 1998]. …”

“…The solid and dotted lines represent the calculated helium flux at equatorial pitch angles a 0 = 80°and a 0 = 70°, respectively, assuming atmospheric helium as the source of secondary production [Selesnick and Mewaldt, 1996]. The dashed line is the sum of the p + He and p + O contributions at a 0 = 80°, while the thick line comes from calculations by [Pugacheva et al, 1998], at a 0 = 90°. pheric density model, and cross-section parameterization, and also on the solar cycle phase.…”

“…[10] Another possible mechanism discussed in literature is a radial diffusion of nuclei inside the magnetosphere. In the work by Pugacheva et al [1998] the secondary production rate for 2 H, 3 H, and 3 He in the upper part of the atmosphere was compared with radial diffusion, and it appeared to dominate at L shell in the interval 1.2 Ä 1.6. The results of the calculations depend on the detailed knowledge of some parameters, such as the radiation belt models and the boundary condition of diffusion equations.…”