Elemental and Isotopic Composition of the Galactic Cosmic Rays

Simpson, J. A.

doi:10.1146/annurev.ns.33.120183.001543

Cited by 621 publications

(318 citation statements)

References 83 publications

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“…For this reason, the event generator has been built to provide as accurately as possible these cross sections over the range of sensitivity of the measurements. The latter extends from a few hundred MeV/c above threshold on the low energy side, up to a few hundred GeV/c at high energy, where the sensitivity vanishes with the spectral distribution of the cosmic flux which varies like ≈ E −2.7 [6,12]. The maximum of sensitivity is expected around 10 GeV.…”

mentioning

confidence: 99%

“…This EW angle dependence consists of a GC momentum P GC much lower for E-bound (P E GC ≈11 GeV/c) than for W-bound (P W GC ≈60 GeV/c) protons [7]. Consequently, a much larger flux of E-bound protons is allowed to interact in the atmosphere, since the incident flux decreases rapidly with the particle momentum as E −2.7 , E being the particle energy [6]. 2.…”

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confidence: 99%

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Secondary electrons and positrons in near earth orbit

2001

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The secondary e + and e − populations in near earth's orbit have been calculated by simulation. The results are in very good agreement with the recent AMS measurements. The e + over e − flux ratio for particles below the geomagnetic cutoff appears to be due to the geomagnetic East-West effect.The study of particle populations in the earth environment has been a field of intense research activity for more than 50 years [1]. After a period of latence, the field is regaining interest with the new generation of ambitious experimental projects. They should bring major improvements to the instrumental accuracy of the measurements and orders of magnitudes to the statistics of counting, with respect to previous experiments (see the references quoted in [2,3] for the current and historical context). Some new measurements of particle flux close to earth have been performed recently by the AMS experiment, providing a large sample of new data. These measurements open new prospects for high precision studies of the cosmic ray (CR)-atmosphere interactions and the dynamics of particles in the magnetosphere. This is of particular importance for the atmospheric neutrino issue, in the current context of this research field, since the knowledge of the (electron and muon) neutrino flux produced in the same decay chain of pions in the atmosphere is necessary for interpreting the results of the underground neutrino experiments [4]. Consequently, a good understanding of the electron and positron flux is highly relevant.The proton distributions measured below the earth geomagnetic cutoff (GC) by AMS [2] have been successfully interpreted recently in terms of interactions of the (proton) cosmic ray (CR) flux with the atmosphere [5]. This work is referred to as I in the following. Extending the work reported in I on protons, the present paper addresses the interpretation of the flux of positrons and electrons measured by AMS below the cutoff (subGC) [3] in the same phenomenological framework.The lepton distributions observed by AMS showed a few remarkable features, of which the main two follow. First, the kinetic energy spectra have a strong subGC (then secondary) component (figure 1), similar to those observed in the proton flux. Second, the ratio of the e + over e − flux is large in the equatorial region (≈ 4) and decreasing towards higher latitudes (≈ 1). The measured spectra extended from the kinetic energy threshold of the spectrometer at ≈0.15 GeV, up to about 30 GeV for e − and 3 GeV for e + . At low energy, the subGC secondary spectral yield decreases rapidly from a maximum around the low energy limit of the spectrometer up to the GC energy, around 15 GeV/c for equatorial latitudes (electrons) where 1

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confidence: 99%

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confidence: 99%

Secondary electrons and positrons in near earth orbit

2001

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“…1 can be ruled out by the γ -ray data. The expression R 2.7 d N/dtd d Ad R = 1.8 × 10 4 (R 0.9 /E) GV 1.7 /(ssr-m 2 ) translates into a cosmic-ray proton flux , with E p the total energy in GeV, based on the cosmic-ray proton spectrum shown in Simpson's review [24]. )…”

Section: γ -Ray Constraints On Cosmic Raysmentioning

confidence: 99%

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

Dermer

2015

EPJ Web of Conferences

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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 → π 0 → 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 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 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.

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“…An energy of 290 A MeV would represent the nucleon-nucleon threshold. Simpson [11] also provides the cosmic ray spectrum for nuclei, such as He, C, Fe. Again the spectrum peak for these nuclei is right near the pion threshold.…”

Section: Sub-threshold Pion and Kaon Production In Nucleus-nucleus Comentioning

confidence: 99%

“…The approximate total experimental cross sections are from Reference [20]. To obtain the flux for Ni, the flux of Fe was used but multiplied by 0.05, which is the average ratio of the abundance of Ni to Fe over all energy intervals [11]. …”

Section: An Example Transport Calculationmentioning

confidence: 99%

Threshold meson production and cosmic ray transport

Norbury¹,

Townsend²,

Norman³

2006

J. Phys. G: Nucl. Part. Phys.

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Abstract. An interesting accident of nature is that the peak of the cosmic ray spectrum, for both protons and heavier nuclei, occurs near the pion production threshold. The Boltzmann transport equation contains a term which is the cosmic ray flux multiplied by the cross section. Therefore when considering pion and kaon production from proton-proton reactions, small cross sections at low energy can be as important as larger cross sections at higher energy. This is also true for subthreshold kaon production in nuclear collisions, but not for subthreshold pion production.PACS numbers: 96.50. 96.50.sb, 96.50.sd, 96.50.Vg, 13.85.Qk, 13.60.Le

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Elemental and Isotopic Composition of the Galactic Cosmic Rays

Cited by 621 publications

References 83 publications

Secondary electrons and positrons in near earth orbit

Secondary electrons and positrons in near earth orbit

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

Threshold meson production and cosmic ray transport

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