Recovering the observed B/C ratio in a dynamic spiral-armed cosmic ray model

Abstract

We develop a fully three dimensional numerical code describing the diffusion of cosmic rays in the Milky Way. It includes the nuclear spallation chain up to Oxygen, and allows the study of various cosmic ray properties, such as the CR age, grammage traversed, and the ratio between secondary and primary particles. This code enables us to explore a model in which a large fraction of the cosmic ray acceleration takes place in the vicinity of galactic spiral arms and that these spiral arms are dynamic. We show that the effect of having dynamic spiral arms is to limit the age of cosmic rays at low energies. This is because at low energies the time since the last spiral arm passage governs the Cosmic Ray (CR) age, and not diffusion. Using the model, the observed spectral dependence of the secondary to primary ratio is recovered without requiring any further assumptions such as a galactic wind, re-acceleration or various assumptions on the diffusivity. In particular, we obtain a secondary to primary ratio which increases with energy below about 1 GeV.

Accepted for publication in The Astrophysical Journal

References in corpus (7)

• Observation of an anomalous positron abundance in the cosmic radiation
• The origin of the positron excess in cosmic rays
• Galactic synchrotron emission with cosmic ray propagation models
• High-energy antiprotons from old supernova remnants
• Testing astrophysical models for the PAMELA positron excess with cosmic ray nuclei
• Inhomogeneity in the Supernova Remnant Distribution as the Origin of the PAMELA Anomaly
• Antimatter Signatures of Gravitino Dark Matter Decay

Cited by in corpus (16)

• High-Energy Gamma Rays from the Milky Way: Three-Dimensional Spatial Models for the Cosmic-Ray and Radiation Field Densities in the Interstellar Medium
• Positron flux and gamma-ray emission from Geminga pulsar and pulsar wind nebula
• Different studies of the global pitch angle of the Milky Way's spiral arms
• Spiral Arms as Cosmic Ray Source Distributions
• Propagation in 3D spiral-arm cosmic-ray source distribution models and secondary particle production using PICARD
• The Galactic Magnetic Field and Ultrahigh-Energy Cosmic Ray Deflections
• Magnetic Deflections of Ultra-High Energy Cosmic Rays from Centaurus A
• Sagittarius A* as an Origin of the Galactic PeV Cosmic Rays?
• Theoretical interpretation of Pass 8 Fermi-LAT $e^{+}+e^{-}$ data
• Reconciling the diffuse Galactic gamma-ray and the cosmic ray spectra
• The B/C and sub-Iron/Iron Cosmic ray ratios - further evidence in favor of the spiral arm diffusion model
• Abundances of 59Co and 59Ni in the cosmic ray flux
• Secondary Production as the Origin for the Cosmic Ray Positron Excess
• Diffuse Gamma Rays in 3D Galactic Cosmic-ray Propagation Models
• Lower limits on the nucleosynthezis of ${}^{44}$Ti and ${}^{60}$Fe in the dynamic spiral-arms model
• Electron-Capture Isotopes could Constrain Cosmic-Ray Propagation Models