Nuclear reactions in the uppermost Earth atmosphere as a source of the magnetospheric positron radiation belt

A physical mechanism for the formation of a natural positron belt in the Ea rth's magnetosphere is considered. It is assumed that a natural source of e nergetic positrons as well as electrons can be created owing to the decay o f charged pions pi (+/-) --> mu (+/-) --> e(+/-), which have their origin i n nuclear collisions between energetic trapped inner zone protons and heavi er atoms (He and O) in the upper atmosphere of the Earth. Simulations of th ese processes demonstrate that there is a predominant production of positiv e pions over negative pions, and consequently the decays result in a substa ntial excess of positrons over electrons at energies greater than tens of M eV. This positron excess is found to be energy-dependent and to decrease wi th increasing incident proton energy; this excess is essentially absent at proton energies corresponding to cosmic ray primaries of greater than or eq ual to8 GeV. Our numerical computations for the resulting e(+)/e(-) fluxes provide ratio values of similar to4 at multi-MeV energies and at L = 1.2 +/ - 0.1. The simulation results presented herein are compared to the existing and recent experimental evidence.