Testing the Origin of High-Energy Cosmic Rays

TL;DR

This paper analyzes recent cosmic-ray spectral features, exploring their possible origins and making testable predictions for secondary cosmic-ray fluxes, anisotropy, and gamma-ray emission to understand high-energy Galactic CRs.

Contribution

It offers new interpretations of spectral hardening and softening in cosmic rays and predicts observable signatures for upcoming experiments.

Findings

Spectral hardening observed above a few hundred GeV per nucleon.

He spectrum is harder than proton spectrum.

Predicted secondary CR fluxes and gamma-ray emissions vary across scenarios.

Abstract

Recent accurate measurements of cosmic-ray (CR) protons and nuclei by ATIC-2, CREAM, and PAMELA reveal: a) unexpected spectral hardening in the spectra of CR species above a few hundred GeV per nucleon, b) a harder spectrum of He compared to protons, and c) softening of the CR spectra just below the break energy. These newly-discovered features may offer a clue to the origin of the observed high-energy Galactic CRs. We discuss possible interpretations of these spectral features and make predictions for the secondary CR fluxes and secondary to primary ratios, anisotropy of CRs, and diffuse Galactic {\gamma}-ray emission in different phenomenological scenarios. Our predictions can be tested by currently running or near-future high-energy astrophysics experiments.