Confinement of cosmic-ray nuclei in ionized source regions and interstellar medium

The problem of delineating the effects of the matter traversed by cosmic rays in the source region (which consists of matter in the ionized state) and in the interstellar medium (which is partially ionized) is investigated in great detail by studying the energy losses suffered by a charged particle in these two media. Expressions for the energy losses are derived from a consideration of the composition of neutral and ionized atoms in these media. The relative intensities of the nuclei of various energies and charges are then calculated for different path lengths traversed in such source regions and in space, taking both the effects of ionization loss and fragmentation in the media concerned. Three kinds of source spectra, namely power law spectra in total energy per nucleon, in kinetic energy per nucleon, and in rigidity are used for this purpose; the exponents and other constants involved in these spectra are deduced from the high-energy data that are little affected by solar modulation. The implications of these calculations are discussed with reference to experimental results on the ratio of intensities (1) ΓH1α of H1 nuclei (Z ≥ 20) to α particles, (2) ΓHα of H nuclei (Z ≥ 10) to α particles, and (3) ΓLS of L nuclei (Z = 3–5) to S nuclei (Z ≥ 6) in the energy region 50–1000 Mev per nucleon. It is concluded that for similar source kinetic energy per nucleon and rigidity spectra, the effect of the matter traversed by particles in the source region is negligible compared to its value in the interstellar space. On the other hand, for a source spectrum that is a power law in total energy per nucleon, the experimental results would indicate an appreciable trapping of the particles in the source region itself.