The Cosmic Ray Boron/Carbon Ratio Measured at Voyager and at AMS-2 from 10 MeV/nuc up to ~1 TeV/nuc and a Comparison With Propagation Calculations

TL;DR

This study compares cosmic ray boron/carbon ratios measured by Voyager and AMS-2 with propagation models, finding close agreement across a wide energy range and highlighting discrepancies below 50 MeV/nuc.

Contribution

It provides the first comprehensive comparison of B/C ratios from Voyager and AMS-2 with propagation models over an extended energy range from MeV/nuc to TeV/nuc.

Findings

Models agree with measurements within +/-10% from 50 MeV/nuc to 1 TeV/nuc.

Propagation models match data without requiring significant additional acceleration.

Discrepancies exist below 50 MeV/nuc, with Voyager data exceeding model predictions.

Abstract

We have used new measurements of the B/C ratio in galactic cosmic rays at both low and high energies by the Voyager and AMS-2 spacecraft, respectively, along with propagation calculations using a truncated LBM to examine the implications of these new measurements over an extended energy range from a few MeV/nuc to 1 TeV/nuc. We find that the predictions from both the truncated LBM and the Diffusive Reacceleration model for GALPROP both agree with the Voyager and AMS-2 measurements of the B/C ratio to within +/- 10 percent throughout the entire energy range from 50 MeV/nuc to 1 TeV/nuc. The two propagation approaches also agree with each other to within +/-10 percent or less throughout this energy range. In effect a diffusion model, without significant additional acceleration, provides a match within +/-10 percent to the combined data from Voyager 1 and AMS-2 on the B/C ratio from 50 MeV/nuc to 1 TeV/nuc. The B/C ratio below 50 MeV/nuc measured at V1 exceeds the predictions of both propagation models by as much as 3 sigma in the data measurement errors.