Implications on cosmic ray injection and propagation parameters from Voyager/ACE/AMS-02 nucleus data

TL;DR

This paper analyzes recent cosmic ray data from Voyager, ACE, and AMS-02 to refine models of cosmic ray injection and propagation, revealing a need for a modified diffusion model and composition-dependent injection spectra.

Contribution

It introduces a modified diffusion-reacceleration model with a rigidity-dependent diffusion coefficient and highlights composition-dependent injection spectra, advancing cosmic ray propagation understanding.

Findings

Diffusion coefficient increases with decreasing rigidity at low energies.

Low rigidity injection spectra vary by nuclear composition, being softer for lighter nuclei.

Data favor a modified diffusion-reacceleration scenario for cosmic ray propagation.

Abstract

We study the propagation and injection models of cosmic rays using the latest measurements of the Boron-to-Carbon ratio and fluxes of protons, Helium, Carbon, and Oxygen nuclei by the Alpha Magnetic Spectrometer and the Advanced Composition Explorer at top of the Earth, and the Voyager spacecraft outside the heliosphere. The ACE data during the same time interval of the AMS-02 data are extracted to minimize the complexity of the solar modulation effect. We find that the cosmic ray nucleus data favor a modified version of the diffusion-reacceleration scenario of the propagation. The diffusion coefficient is, however, required to increase moderately with decreasing rigidity at low energies, which has interesting implications on the particle and plasma interaction in the Milky Way. We further find that the low rigidity ($<$ a few GV) injection spectra are different for different compositions. The injection spectra are softer for lighter nuclei. These results are expected to be helpful in understanding the acceleration process of cosmic rays.