The Cosmic Ray Helium and Carbon Nuclei Spectra Measured by Voyager 1 at Low Energies and Earth Based Measurements of these Nuclei up to 200 GeV nuc Concordance at High Energies with a Leaky Box Propagation Model

TL;DR

This study compares Voyager 1 and Earth-based measurements of helium and carbon cosmic ray spectra, demonstrating that a leaky box model with specific parameters accurately fits observed data across a wide energy range, revealing an excess of helium at low energies.

Contribution

The paper provides a detailed interpretation of cosmic ray helium and carbon spectra, showing consistency with a leaky box propagation model and highlighting differences in low-energy behavior compared to hydrogen.

Findings

Voyager and PAMELA data fit a leaky box model with P-2.28 source spectra.

The model accurately describes spectra from 40 MeV/nuc to 100 GeV/nuc.

An excess of helium at low energies (~20%) is observed compared to model predictions.

Abstract

A comparison of the Helium and Carbon interstellar spectra measured at Voyager in the local interstellar medium leads to a different interpretation than a comparison of the Hydrogen to Helium spectra. This is because the He/C ratio is observed to increase rapidly with energy below 40 MeV/nuc in contrast to an almost constant H/He ratio at these low energies. Both the He and C spectra that are observed at Voyager above 40 MeV/nuc and much higher energy spectra from the PAMELA measurements of these two components up to 100 GeV/nuc can be accurately fit to within 10% assuming galactic propagation in a leaky box type of diffusion model in the galaxy with identical source spectra P-2.28 for He and C using a diffusion coefficient P0.50 above 1 GV rigidity. These same exponents also fit the H spectrum from 40 MeV to over 100 GeV. At low energies an excess of He relative to C is observed that would amount to about 20% of the modeled galactic component at 10 MeV/nuc.