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The Proton and Helium cosmic ray spectra from 50 GeV to 15 TeV
A. V. Karelin, S. V. Borisov, A. M. Galper,S. A. Voronov for PAMELA collaboration
Astrophysics and Space Sciences Transactions (ASTRA) , 2011, DOI: 10.5194/astra-7-235-2011
Abstract: To date, very little has been done in the field of research of the nuclei cosmic ray spectra in the energy range between 1 and 10 TeV per nucleon and especially there were even fewer direct measurements in space. The PAMELA experiment (Casolini et al., 2008) has a possibility to make progress in this range. The method of the measurement of the helium and proton cosmic ray spectra with the energy higher than 50 GeV/nucleon was developed mainly with the use of the PAMELA calorimeter. This analysis method and the results obtained based on 3 years of measurements are presented.
TeV cosmic-ray proton and helium spectra in the myriad model  [PDF]
Guilhem Bernard,Timur Delahaye,Yong-Yeon Keum,Wei Liu,Pierre Salati,Richard Taillet
Physics , 2012, DOI: 10.1051/0004-6361/201321202
Abstract: Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundreds of GeV. This excess is hard to understand in the framework of the conventional models of Galactic cosmic ray production and propagation. We propose here to explain this anomaly by the presence of local sources (myriad model). Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. Improving over a similar analysis, we consistently derive these fluxes by taking into account both local and remote sources for which a unique injection rate is assumed. We find cosmic ray propagation parameters compatible with B/C measurements and for which the proton and helium spectra remarkably agree with the PAMELA and CREAM measurements over four decades in energy.
Anomaly in the cosmic-ray energy spectrum at GeV-TeV energies  [PDF]
Satyendra Thoudam,J?rg H?randel
Physics , 2015, DOI: 10.1088/1742-6596/632/1/012026
Abstract: Recent measurements of cosmic rays by various experiments have found that the energy spectrum of cosmic rays is harder in the TeV region than at GeV energies. The origin of the spectral hardening is not clearly understood. In this paper, we discuss the possibility that the spectral hardening might be due to the effect of re-acceleration of cosmic rays by weak shocks associated with old supernova remnants in the Galaxy.
Are GeV and TeV spectra connected? the case of Galactic gamma-ray sources  [PDF]
P. Tam,S. Wagner
Physics , 2011,
Abstract: To understand Galactic objects that emits GeV-TeV emission, a spatial correlation study between the Fermi bright source catalog and TeV source population was carried out in Tam et al. (2010), finding that a significant number of very high-energy (VHE; E >100 GeV) sources are also emitting at GeV energies. We extended our previous study utilizing the first Fermi catalog (1FGL) sources. A cross-correlation comparison of the 1FGL sources was carried out with the VHE gamma-ray sources in the literature as of May 2011. While it is found that a significant number of VHE gamma-ray sources were also detected in the GeV band, the GeV-TeV spectra of some of these spatially coincident sources cannot be described by a single spectral component. While some of these cases are gamma-ray pulsars accompanied by VHE gamma-ray emitting nebulae, we present cases where the 100 MeV to multi-TeV spectra of coincident 1FGL/VHE source pairs do not seem to be well fit by a single spectral component.
TeV cosmic-ray proton and helium spectra in the myriad model II  [PDF]
Wei Liu,Pierre Salati,Xuelei Chen
Physics , 2014, DOI: 10.1088/1674-4527/15/1/002
Abstract: Recent observations show that the cosmic ray nuclei spectra start to harden above 100 GeV, in contradiction with the conventional steady-state cosmic ray model. We had suggested that this anomaly is due to the propagation effect of cosmic rays released from local young cosmic ray sources, the total flux of the cosmic ray should be computed with the myriad model, where contribution from sources in local catalog is added to the background. However, while the hardening could be elegantly explained in this model, the model parameters obtained from the fit skew toward a region with fast diffusion and low supernova rate in the Galaxy, in tension with other observations. In this paper, we further explore this model in order to set up a concordant picture. Two possible improvements related to the cosmic ray sources have been considered. Firstly, instead of the usual axisymmetric disk model, we considered a spiral model of source distribution. Secondly, for the nearby and young sources which are paramount to the hardening, we allow for an energy-dependent escape time. We find that major improvement comes from the energy-dependent escape time of the local sources, and with both modifications, not only the cosmic ray proton and helium anomalies are solved, but also the parameters attain reasonable range values compatible with other analysis.
GeV-TeV cosmic-ray spectral anomaly as due to re-acceleration by weak shocks in the Galaxy  [PDF]
Satyendra Thoudam,J?rg R. H?randel
Physics , 2014, DOI: 10.1051/0004-6361/201322996
Abstract: Recent cosmic-ray measurements have found an anomaly in the cosmic-ray energy spectrum at GeV-TeV energies. Although the origin of the anomaly is not clearly understood, suggested explanations include effect of cosmic-ray source spectrum, propagation effects, and the effect of nearby sources. In this paper, we propose that the spectral anomaly might be an effect of re-acceleration of cosmic rays by weak shocks in the Galaxy. After acceleration by strong supernova remnant shock waves, cosmic rays undergo diffusive propagation through the Galaxy. During the propagation, cosmic rays may again encounter expanding supernova remnant shock waves, and get re-accelerated. As the probability of encountering old supernova remnants is expected to be larger than the younger ones due to their bigger sizes, re-acceleration is expected to be mainly due to weaker shocks. Since weaker shocks generate a softer particle spectrum, the resulting re-accelerated component will have a spectrum steeper than the initial cosmic-ray source spectrum produced by strong shocks. For a reasonable set of model parameters, it is shown that such re-accelerated component can dominate the GeV energy region while the non-reaccelerated component dominates at higher energies, explaining the observed GeV-TeV spectral anomaly.
Ultra-High Energy Cosmic Rays and the GeV-TeV Diffuse Gamma-Ray Flux
Kalashev, Oleg E.;Semikoz, Dmitry V.;Sigl, Guenter
High Energy Physics - Phenomenology , 2007,
Abstract: Ultra-high energy cosmic ray protons accelerated in astrophysical objects produce secondary electromagnetic cascades during propagation in the cosmic microwave and infrared backgrounds. We show that such cascades can contribute between ~1% and ~50% of the GeV-TeV diffuse photon flux measured by the EGRET experiment. The GLAST satellite should have a good chance to discover this flux.
Production of secondary particles and nuclei in cosmic rays collisions with the insterstellar gas using the {\tt FLUKA} code  [PDF]
M. N. Mazziotta,F. Cerutti,A. Ferrari,D. Gaggero,F. Loparco,P. R. Sala
Physics , 2015,
Abstract: The measured fluxes of secondary particles produced by the interactions of Cosmic Rays (CRs) with the astronomical environment play a crucial role in understanding the physics of CR transport. In this work we present a comprehensive calculation of the secondary hadron, lepton, gamma-ray and neutrino yields produced by the inelastic interactions between several species of stable or long-lived cosmic rays projectiles (p, D, T, 3He, 4He, 6Li, 7Li, 9Be, 10Be, 10B, 11B, 12C, 13C, 14C, 14N, 15N, 16O, 17O, 18O, 20Ne, 24Mg and 28Si) and different target gas nuclei (p, 4He, 12C, 14N, 16O, 20Ne, 24Mg, 28Si and 40Ar). The yields are calculated using FLUKA, a simulation package designed to compute the energy distributions of secondary products with large accuracy in a wide energy range. The present results provide, for the first time, a complete and self-consistent set of all the relevant inclusive cross sections regarding the whole spectrum of secondary products in nuclear collisions. We cover, for the projectiles, a kinetic energy range extending from $0.1~GeV/n$ up to $100~TeV/n$ in the lab frame. In order to show the importance of our results for multi-messenger studies about the physics of CR propagation, we evaluate the propagated spectra of Galactic secondary nuclei, leptons, and gamma rays produced by the interactions of CRs with the insterstellar gas, exploiting the numerical codes DRAGON and GammaSky. We show that, adopting our cross section database, we are able to provide a good fit of a complete sample of CR observables, including: leptonic and hadronic spectra measured at Earth, the local interstellar spectra measured by Voyager, and the gamma-ray emissivities from Fermi-LAT collaboration. We also show a set of gamma-ray and neutrino full-sky maps and spectra.
Observations of High Energy Cosmic-Ray Electrons from 30 GeV to 3 TeV with Emulsion Chambers  [PDF]
Tadashi Kobayashi,Yoshiko Komori,Kenji Yoshida,Kazuki Yanagisawa,Jun Nishimura,Takamasa Yamagami,Yoshitaka Saito,Nobuhito Tateyama,Toshinori Yuda,Jeffrey Wilkes
Physics , 2012, DOI: 10.1088/0004-637X/760/2/146
Abstract: We have performed a series of cosmic-ray electron observations using the balloon-borne emulsion chambers since 1968. While we previously reported the results from subsets of the exposures, the final results of the total exposures up to 2001 are presented here. Our successive experiments have yielded the total exposure of 8.19 m^2 sr day at the altitudes of 4.0 - 9.4 g/cm^2. The performance of the emulsion chambers was examined by accelerator beam tests and Monte-Carlo simulations, and the on-board calibrations were carried out by using the flight data. In this work we present the cosmic-ray electron spectrum in the energy range from 30 GeV to 3 TeV at the top of the atmosphere, which is well represented by a power-law function with an index of -3.28+-0.10. The observed data can be also interpreted in terms of diffusive propagation models. The evidence of cosmic-ray electrons up to 3 TeV suggests the existence of cosmic-ray electron sources at distances within ~1 kpc and times within ~1x10^5 yr ago.
Cosmic-Ray Proton and Helium Spectra from the First CREAM Flight  [PDF]
Y. S. Yoon,H. S. Ahn,P. S. Allison,M. G. Bagliesi,J. J. Beatty,G. Bigongiari,P. J. Boyle,J. T. Childers,N. B. Conklin,S. Coutu,M. A. DuVernois,O. Ganel,J. H. Han,J. A. Jeon,K. C. Kim,M. H. Lee,L. Lutz,P. Maestro,A. Malinine,P. S. Marrocchesi,S. A. Minnick,S. I. Mognet,S. Nam,S. Nutter,I. H. Park,N. H. Park,E. S. Seo,R. Sina,S. Swordy,S. P. Wakely,J. Wu,J. Yang,R. Zei,S. Y. Zinn
Physics , 2011, DOI: 10.1088/0004-637X/728/2/122
Abstract: Cosmic-ray proton and helium spectra have been measured with the balloon-borne Cosmic Ray Energetics And Mass experiment flown for 42 days in Antarctica in the 2004-2005 austral summer season. High-energy cosmic-ray data were collected at an average altitude of ~38.5 km with an average atmospheric overburden of ~3.9 g cm$^{-2}$. Individual elements are clearly separated with a charge resolution of ~0.15 e (in charge units) and ~0.2 e for protons and helium nuclei, respectively. The measured spectra at the top of the atmosphere are represented by power laws with a spectral index of -2.66 $\pm$ 0.02 for protons from 2.5 TeV to 250 TeV and -2.58 $\pm$ 0.02 for helium nuclei from 630 GeV/nucleon to 63 TeV/nucleon. They are harder than previous measurements at a few tens of GeV/nucleon. The helium flux is higher than that expected from the extrapolation of the power law fitted to the lower-energy data. The relative abundance of protons to helium nuclei is 9.1 $\pm$ 0.5 for the range from 2.5 TeV/nucleon to 63 TeV/nucleon. This ratio is considerably smaller than the previous measurements at a few tens of GeV/nucleon.
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