Comments on stochastic acceleration of cosmic rays

Abstract

The spectrum of particles subjected to second-order Fermi acceleration is studied, and the spectra of both the primary particles such as C and O and their nuclear secondaries such as Li, Be, and B are derived explicitly. The second-order term is seen to be of prime importance in the acceleration process. The secondary-to-primary ratio is shown to increase logarithmically with energy contrary to observation. These considerations are extended to arbitrary stochastic processes, and it is concluded that cosmic rays are not accelerated in the interstellar medium.