Production and propagation of cosmic ray H2 and He3 nuclei

Ramadurai, S. ; Biswas, S. (1974) Production and propagation of cosmic ray H2 and He3 nuclei Astrophysics and Space Science, 30 (1). pp. 187-213. ISSN 0004-640X

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The results of detailed calculations on the production of H2 and He3 nuclei by cosmic ray protons and helium nuclei in interstellar medium are presented. The flux and energy spectra of these nuclei as well as those of cosmic ray H1 and He4 nuclei in the vicinity of the Earth are calculated. For this purpose the source spectra are assumed to be in the form of a power law in total energy per nucleon with an additional velocity dependent term. This spectrum denoted as Fermi Spectrum, is about midway between the power law spectrum in rigidity and in total energy per nucleon. The fluxes are calculated taking into account: (1) energy dependent cross-sections of thirteen nuclear reactions of cosmic ray protons and helium nuclei with interstellar H1 and He4 leading to the production of H2 and He3 nuclei, (2) angular distributions and kinematics of these reactions, (3) ionization loss of the primary and secondary nuclei in interstellar medium, (4) elastic collisions of cosmic ray protons and helium nuclei, (5) distributions of cosmic ray path-lengths in in terstellar space as in gaussian and exponential forms, and (6) interplanetary modulation of cosmic rays from the numerical solution of the complete Fokker-Planck equation describing the diffusion, convection and adiabatic deceleration of cosmic ray nuclei in the solar system. On comparing the calculated values of H2/He4 and He3/(He3+He4) as a function of energy with the observed data of several investigators, it is found that agreement between the calculated values and most of the observed data is obtained on the basis of: (a) source spectrum in the form of 'Fermi' Spectrum, (b) distribution of path-lengths as in the gaussian form with a mean value of 4 g cm-2 of hydrogen or as in exponential form with leakage path length of 4 g cm-2.

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