The acceleration of interstellar grains and the composition of the cosmic rays

It is shown that if strong interstellar shock waves provide the main energy source for the galactic cosmic rays, then these same shock waves efficiently accelerate the nuclei contained in the interstellar grains up to relativistic energies. This occurs in three stages: (1) Grains are accelerated to many times the shock velocity by the converging flow in the shock front, (2) Interactions with the ambient gas cause the grains to shed mass thereby producing super-thermal ions. (3) The ions re-enter the shock front and are accelerated to relativistic energies. This process may explain the relatively high abundances of the refractory elements in the cosmic rays and possibly the unusual isotropic ratios of the cosmic ray neon.

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