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 gamma-ray emissivity. Calculations are made of the diffuse cosmic-ray induced p+p --> pi^0 --> 2 gamma 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 R >~ 300 GV. A single power-law momentum "shock" spectrum for the local interstellar medium cosmic-ray proton spectrum cannot be ruled out from the gamma-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 alpha-particle hardening are discussed.
Highlights
On the way to writing this proceedings article for the 2nd SUGAR (Searching for the sources of galactic cosmic rays) Workshop, held in the Departement de Physique nucleaire et corpusculaire at Universite Geneve on 21–23 January 2015, the Alpha Magnetic Spectrometer Collaboration held a significant data release on its “AMS days at CERN,” which took place 15–17 April 2015 [1]
The major results presented at the AMS days were the p / p ratio from kinetic energies Tp 1 GeV to Tp≈ 350 GeV, and the cosmic-ray proton and α particle spectra for rigidities 10 GV R 1500 GV (p) and 10 GV R 2500 GV (α)
In the most recent AMS-02 data [1], the p / p ratio is reported to be roughly constant for 10 GeV Tp 350 GeV with a value of ≈ 2 × 10−4
Summary
On the way to writing this proceedings article for the 2nd SUGAR (Searching for the sources of galactic cosmic rays) Workshop, held in the Departement de Physique nucleaire et corpusculaire at Universite Geneve on 21–23 January 2015, the Alpha Magnetic Spectrometer Collaboration held a significant data release on its “AMS days at CERN,” which took place 15–17 April 2015 [1]. We consider whether the breaks in the spectra of cosmicray protons and ions are a consequence of propagation effects, multiple injection sources with different spectral indices, or due to hardening produced by nuclear collisions which preferentially depletes the low-energy particles that traverse larger grammages.
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