Spallation-dominated propagation of heavy cosmic rays and the Local Interstellar Medium (LISM)

Abstract

Abstract. Measurements of ultra-heavy nuclei at GeV/n energies in the galactic cosmic radiation address the question of their sources (nucleosynthetic s-and r-processes). As such, the determination of CR source abundances is a promising way to discriminate between existing nucleosynthesis models. For primary species (nuclei present and accelerated at the source), it is generally assumed that the relative propagated abundances, if they are close in mass, are not too different from their relative source abundances. The range of the correction factor associated with propagation has been estimated in weighted slab models only. Heavy CRs that are detected near the Earth were accelerated from regions that are closer to us than were the light nuclei. Hence, both the geometry of sources in the Solar neighbourhood, and the geometry of gas in the same region, must be taken into account. In this paper, a two zone diffusion model is used, and as was previously investigated for radioactive species, we report here on the impact of the local interstellar medium (LISM -under-dense medium over a scale ∼100 pc) on primary and secondary stable nuclei propagated abundances. Considering down to Fe nuclei, the connection between heavy and light abundances is also inspected. A general trend is found that decreases the UHCR source abundances relative to the HCR ones. This could have an impact on the level of r-processes required to reproduce the data.

The Origin of Cosmic Rays: How Their Composition Defines Their Sources and Sites and the Processes of Their Mixing, Injection, and Acceleration

“…Calculations ) of cosmic ray elemental enrichment ratios of the ThU/Pt group from supernovae also suggests a similar ejecta mixing ratio F EJ close to 20% for the products of explosive r-process supernova nucleosynthesis. These calculations based on Kratz et al (1993) of the radioactive Actinide/Pt group abundance ratio predicted a cosmic ray source value of 0.027±0.005, which is quite consistent with the latest balloon measurements (Combet et al 2005;Donnelly et al 2012) of ~0.032.…”

“…Moreover, comparisons of cosmic ray elemental abundance ratios measurements (Combet et al 2005;Donnelly et al 2012) of the ThU/Pt group with supernova r-process nucleosynthetic calculations ) also suggest a similar ~20% ejecta mixing ratio F EJ for such products of explosive r-process supernovae. The possibility of determining the relative contributions of CCSN s-and r-process yields can also be seen from the (Z/H) GCRS/SMGI outliers above (Z > 30) that appear to result from the contributions of r-process elements to the cosmic rays from CCSNe in addition to that calculated by (Woosley & Heger 2007) solely for the s-process.…”

Astrophysics in 2005

“…Combet et al (2005) conclude that the cosmic ray actinides were accelerated within 150 pc of us, vs. 1.25 kpc for Li, Be, and B. Higdon & Lingenfelter (2005) put most of the acceleration of the heavier nuclei in superbubbles, also close to us; and Derbina et al (2005) draw attention to the rapid change in composition, from a mean mass of five amu 5 at eV 12 15…”

Cosmic-Ray Database Update: Ultra-High Energy, Ultra-Heavy, and Antinuclei Cosmic-Ray Data (CRDB v4.0)

“…How much p- [56,57], r-, and s-processes [58,59] contribute to the various UHCRs, and which astrophysical sites are involved remain debated. Moreover, the abundance of UHCRs slightly differs from the Solar system ones, and these differences are likely to be related to specific acceleration (e.g., [60]) or transport processes (e.g., [61]).…”