Cosmic rays IX - Interactions and transport of cosmic rays in the Galaxy

We propose that cosmic rays interact mostly near their sources of origin. T o be specific, we differentiate the various supernovae by their mass of the progenitor star along the zero age main sequence. Stars between about 8 an d 15 solar masses explode into the interstellar medium, and accelerate cosm ic rays, as discussed by many for some time. From about 15 to 25 solar mass es stars explode into their own stellar wind; this wind has built up a thin shell of both wind material and interstellar medium material in the red an d blue giant phases preceding the supernova event. The shock accelerating c osmic ray particles races through that wind, gets loaded up with energetic particles, interacts while it goes, and finally smashes into the shell. Whi le the shock goes out, it snowplows the entire wind into the pre-existing s hell to form a composite shell. We propose that for the mass range 15 to 25 solar masses this composite shell is immediately broken up so that the tim e scale for interaction is caused by the breakup and so is convective. We n ote that the wind material for this range of zero age masses is a approxima tely half helium, and half hydrogen. The interactions in the composite wind -shell and the immediate environment produce positrons, gamma emission, but only few secondary nuclei, because for this mass range the enrichment in h eavier elements is still minor. The energy spectrum of the gamma emission a nd the positrons produced corresponds then to the source spectrum. In contr ast, from about 25 solar masses and up the wind is strongly enriched in hea vy elements, and the wind shell is massive, comprising most of the initial zero age star's mass, as well as a good part of the local interstellar medi um. We propose that for the interaction of the cosmic ray particles carried out by the shock in the snow-plow through the wind to the shell the intera ction is diffusive, and calculate the diffusion coefficient. This leads to a leakage time energy dependence of E-5/9 in the relativistic limit. This t hen gives an energy dependence of secondary nuclei, that matches the observ ations. There is a second component of positrons, and also gamma emission, but then at moderate energies all with the steeper energy dependence; spati al and velocity constraints give both a lower as well as an upper rigidity limit to the diffusion approximation. One important element in such a pictu re is the steady mixing of newly enriched material throughout the star befo re the explosion, induced by Voigt-Eddington circulation caused by rotation . The mixed material is then ejected through the wind, which at the end pro vides the source material for cosmic ray injection. This means that by the time the nuclei are subject to acceleration, they should have decayed alrea dy to final states, an effect which may be measureable in cosmic ray isotop e ratios. Therefore, considering the history of the travel of cosmic rays t hrough the normal interstellar medium, we can readily explain the ratio of secondaries to primaries, and at the same time use a spectrum of turbulence in the interstellar medium; a Kolmogorov spectrum, which is consistent wit h all other observational evidence. The escape time from the Galaxy is then proportional to E-1/3 in the relativistic range of particle energies. Tran slating this result into the language common in the literature, this means that interaction path as measured in gm/cm(2) and escape time can not be us ed synonymously.