Propagation and Source Charcteristics Derived from the Low-Energy Multiply Charged, Cosmic-Ray Nuclei

Models for the origin and propagation of the cosmic-ray nuclei which assume a uniform particle popula- tion defined by a single set of propagation and source characteristics (including recently proposed steady- state models with a broad path-length distribution function) do not look attractive in terms of the nearby interstellar energy spectra derived from recent low-energy measurements made on the OGO-I Earth satellite. Instead, the properties of these interstellar energy spectra strongly suggest the existence of two distinct particle populations or "components." These two components would result from different types of sources or modes of propagation We show quantitatively that such two-component models satisfy the present experimental results down to the lowest observed energies over the wide nuclear charge range of helium to iron. The constraints placed by the data on two-component models are discussed with the aid of calcu- lated interstellar energy spectra of the nuclear charge groups He, B, CNO (6 «= Z «= 8), LII (10 «= Z «= 15), and the Fe group (25 «= Z «= 28) derived for several different sets of source and propagation parame- ters. These calculated spectra are compared with the observed energy spectra of these charge groups corrected for solar modulation. Physical conditions which may give rise to two distinct particle popula- tions are discussed briefly. The analysis is based on the revised and updated differential kinetic energy spectra measured on the OGO-I satellite and reported by Comstock, Fan, and Simpson