Impact of Fermi-LAT and AMS-02 results on cosmic-ray astrophysics

Space Science Division, US Naval Research Laboratory, Washington, DC, USA

^a e-mail: charles.dermer@nrl.navy.mil

Published online: 8 December 2015

Abstract

This article reviews a few topics relevant to Galactic cosmic-ray astrophysics, focusing on the recent AMS-02 data release and Fermi Large Area Telescope data on the diffuse Galactic γ-ray emissivity. Calculations are made of the diffuse cosmic-ray induced p + p → π⁰ → 2γ spectra, normalized to the AMS-02 cosmic-ray proton spectrum at ≈ 10 − 100 GV, with and without a hardening in the cosmic-ray proton spectrum at rigidities R300 GV. A single power-law momentum “shock” spectrum for the local interstellar medium cosmic-ray proton spectrum cannot be ruled out from the γ-ray emissivity data alone without considering the additional contribution of electron bremsstrahlung. Metallicity corrections are discussed, and a maximal range of nuclear enhancement factors from 1.52 to 1.92 is estimated. Origins of the 300 GV cosmic-ray proton and α-particle hardening are discussed.