PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra

By O. Adriani, G. Barbarino, Galina Bazilevskaya, R. Bellotti, M. Boezio, É. Bogomolov, L. Bonechi, M. Bongi, V. Bonvicini, S. Borisov and 55 more. Science, 2011

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Satellite measurements challenge the current understanding of cosmic-ray acceleration and propagation in our Galaxy. Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/52b8e3a3d58e1f43e036bfc5b355d25df85495c9

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Citations in the corpus

AMS-02 antiprotons, at last! Secondary astrophysical component and immediate implications for Dark Matter (2015, methodology): “The spectra are measured up to a rigidity of 1.8 and 3 TV for p and α nuclei, respectively, and, as already reported by the Pamela Collaboration [29], they cannot be described by a single power law: a hardening at energies higher than ∼300 GV is observed for both.”
Cosmic-ray energy spectrum and composition up to the ankle - the case for a second Galactic component (2016, background): “…rise of the positron fraction above ⇠10 GeV (Aguilar et al. 2013), the harder energy spectrum of helium nuclei with respect to the proton spectrum (Adriani et al. 2011), and the spectral hardening of both the proton and helium nuclei at TeV energies (Yoon et al. 2011), are di cult to explain…”
GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THE FERMI LARGE AREA TELESCOPE (2012, neutral): “The diffuse neutral-pion-decay component for the Milky Way has spectral index∼ 2.75 above ∼ 1 GeV, matching the locally measured CR proton spectrum (Simpson 1983; Sanuki et al. 2000; Adriani et al. 2011).”
The Nine Lives of Cosmic Rays in Galaxies (2015, methodology): “To do so, we have extrapolated the Voyager 1 data down to 1 MeV and we have used the ionization cross section of Spitzer & Tomasko (1968) and solar modulation potentials of 450-500 MV for Pamela (Adriani et al. 2011) and 400 MV for AMS02.”
TIME DEPENDENCE OF THE e− FLUX MEASURED BY PAMELA DURING THE 2006 JULY–2009 DECEMBER SOLAR MINIMUM (2013, methodology): “The analysis procedure was similar to previous work on highenergy proton and helium fluxes (Adriani et al. 2011).”
DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA (2016, methodology): “±0.005 (syst.) measured by the PAMELA experiment in the range 30 GV to 1.2 TV, which is beyond the influence of solar modulation (Adriani et al. 2011).”
Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. II: anisotropy (2011, result): “The case of fast diffusion also leads in general to negligible spallation of nuclei, so that the Helium spectrum at Earth is roughly parallel to that of protons, in contradiction with recent CREAM [10] and PAMELA [11] data that suggest a harder He spectrum above TeV energies.”
THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV (2014, methodology): “…break in the energy spectrum and the harder injection spectrum for helium are motivated by the results of the measurements of the proton spectrum by the PAMELA satellite (Adriani et al. 2011b), and by the CR spectrum inferred from LAT observations of Earth limb γ rays (Ackermann et al. 2014)11.”
A new model of cosmogenic production of radiocarbon 14C in the atmosphere (2012, background): “…(in particle number) to LIS of GCR leading to the nucleonic fraction of heavier species to protons of the160 order of 0.25-0.3 outside the heliosphere (e.g. Alcaraz et al., 2000a,b; Adriani et al., 2011; Webber and Higbie, 2003;161 Nakamura et al., 2010), viz. half of that assumed by MB09.”
MEASUREMENT OF BORON AND CARBON FLUXES IN COSMIC RAYS WITH THE PAMELA EXPERIMENT (2014, methodology): “The error estimation procedure is described in the Supporting Online Material of Adriani et al. (2011) .”
An Introduction to Particle Dark Matter (2019, background): “Positrons, and in part antiprotons, have attracted attention due to “anomalies” reported by the detector PAMELA (part of the AMS-02 project mounted on the International Space Station) [5].”