2002/02/28 by D. Maurin, Michel Cassé, M. Casse +2
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #COSMIC cancer database #Cosmic ray #Cosmic ray spallation #Dark Matter and Cosmic Phenomena #Gamma-ray bursts and supernovae #High energy #Interpretation (philosophy) #Nuclear physics #Particle physics #Physics #Ultra-high-energy cosmic ray #astro-ph
paper · pdf · doi:10.1016/s0927-6505(02)00163-9
published as Astropart.Phys. 18 (2003) 471-486 · 26 pages, 7 PostScript figures. Astropart. Phys, accepted; misprint in fig6 corrected
arxiv created 2002/07/01 · openalex publication_date 2003/01/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A substantial increase of the mean logarithmic mass <ln A> of galactic cosmic rays \em vs energy has been observed . We study three effects that could explain this trend i) different source spectra for protons and heavy nuclei ii) a selective nuclear destruction in flight of heavies iii) a gradient of the source number and chemical composition in the galactic disk. We take advantage of the diffusive cosmic ray propagation model developed at LAPTH to study specifically the geometrical aspects of the propagation and extend it to high energy. Using a simple modeling of the spectral knee around 1015 eV, a bump in <ln A> appears. This feature is smoother when the spectral index of protons is steeper than Fe's. We analyze the effects of the rigidity dependence of the diffusion coefficient and the scale height of the confinement halo and we show that <ln A> is most sensitive to the first parameter. Pure geometrical effects are less determining than the diffusion coefficient spectral index. Subsequently, we conclude that the physics of cosmic ray confinement is the essential cause of the heavy nuclei enrichment until ∼ 1015 eV.