Author
A. F. Li
Other affiliations: Shandong Agricultural University
Bio: A. F. Li is an academic researcher from Shandong University. The author has contributed to research in topics: Air shower & Cosmic ray. The author has an hindex of 12, co-authored 33 publications receiving 764 citations. Previous affiliations of A. F. Li include Shandong Agricultural University.
Topics: Air shower, Cosmic ray, Sidereal time, Pulsar, Galactic plane
Papers
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Hirosaki University1, Saitama University2, Chinese Academy of Sciences3, Yokohama National University4, Hebei Normal University5, Tibet University6, Shandong University7, Southwest Jiaotong University8, Yunnan University9, Kanagawa University10, Utsunomiya University11, University of Tokyo12, Konan University13, Shibaura Institute of Technology14, Shinshu University15, Tsinghua University16, Waseda University17, National Institute of Informatics18, College of Industrial Technology19, Shonan Institute of Technology20
TL;DR: Two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV) is presented, using the large data sample of the Tibet Air Shower Arrays, revealing finer details of the known anisotropies.
Abstract: The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.
259 citations
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Hirosaki University1, Chinese Academy of Sciences2, Yokohama National University3, Hebei Normal University4, Tibet University5, Shandong University6, Southwest Jiaotong University7, Yunnan University8, Kanagawa University9, Utsunomiya University10, University of Tokyo11, Konan University12, Waseda University13, Shinshu University14, Tsinghua University15, Saitama University16, National Institute of Informatics17, College of Industrial Technology18, Max Planck Society19, Shonan Institute of Technology20
TL;DR: In this paper, the authors presented an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10 14 to 10 17 eVusing 5:5 ; 10 7 events collected from 2000 November through 2004 October by the Tibet-III air-shower array located 4300 m in altitude.
Abstract: We present an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10 14 to 10 17 eVusing 5:5 ; 10 7 events collected from 2000 November through 2004 October by the Tibet-III air-shower array located 4300 m abovesealevel(anatmosphericdepthof 606gcm � 2 ).Thesizespectrumexhibitsasharpkneeatacorrespondingprimary energy around 4 PeV. This work uses increased statistics and new simulation calculations for the analysis. We discuss our extensive Monte Carlo calculations and the model dependencies involved in thefinal result, assuming interaction models QGSJET01c and SIBYLL2.1, and heavy dominant (HD) and proton dominant (PD) primary composition models. Pure protonandpureironprimarymodelsarealsoexaminedasextremecases.A detector simulationwasalsoperformedtoimproveouraccuracyindeterminingthesizeof theairshowersandtheenergyof theprimaryparticle.Weconfirmedthatthe all-particle energy spectra obtained under various plausible model parameters are not significantly different from each other, which was the expected result given the characteristics of the experiment at high altitude, where the air showers of the primary energy around the knee reach near-maximum development, with their features dominated by electromagnetic components,leadingtoaweakdependenceontheinteractionmodel or theprimarymass.Thisisthehighest statistical and the best systematics-controlled measurement covering the widest energy range around the knee energy region.
194 citations
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Hirosaki University1, Chinese Academy of Sciences2, University of Tokyo3, Hebei Normal University4, Tibet University5, Shandong University6, Southwest Jiaotong University7, Yunnan University8, Kanagawa University9, Utsunomiya University10, Konan University11, Waseda University12, Yokohama National University13, Shinshu University14, Tsinghua University15, Saitama University16, National Institute of Informatics17, Sakushin Gakuin University18, College of Industrial Technology19, Max Planck Society20, Shonan Institute of Technology21
TL;DR: In this article, the authors estimate the systematic error in determining the primary energy from its shower size, which is estimated to be less than ±12% in their experiment. But this error is consistent with other independent γ-ray observations by imaging air Cherenkov telescopes.
Abstract: The Tibet-III air shower array, consisting of 533 scintillation detectors, has been operating successfully at Yangbajing in Tibet, China since 1999. Using the data set collected by this array from 1999 November through 2005 November, we obtained the energy spectrum of γ-rays from the Crab Nebula, expressed by a power law as (dJ/dE) = (2.09 ± 0.32) × 10–12(E/3 TeV)–2.96±0.14 cm–2 s–1 TeV–1 in the energy range of 1.7-40 TeV. This result is consistent with other independent γ-ray observations by imaging air Cherenkov telescopes. In this paper, we carefully checked and tuned the performance of the Tibet-III array using data on the Moon's shadow in comparison with a detailed Monte Carlo (MC) simulation. The shadow is shifted to the west of the Moon's apparent position as an effect of the geomagnetic field, although the extent of this displacement depends on the primary energy of positively charged cosmic rays. This finding enables us to estimate the systematic error in determining the primary energy from its shower size. This error is estimated to be less than ±12% in our experiment. This energy scale estimation is the first attempt among cosmic ray experiments at ground level. The systematic pointing error is also estimated to be smaller than 0011. The deficit rate and the position of the Moon's shadow are shown to be very stable within a statistical error of ±6% year by year. This guarantees the long-term stability of pointlike source observation with the Tibet-III array. These systematic errors are adequately taken into account in our study of the Crab Nebula.
51 citations
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Hirosaki University1, Tibet University2, Hebei Normal University3, Shandong University4, Southwest Jiaotong University5, Chubu University6, Kanagawa University7, Utsunomiya University8, Konan University9, Yokohama National University10, Shinshu University11, University of Tokyo12, Shandong Agricultural University13, Saitama University14, National Institute of Informatics15, Sakushin Gakuin University16, Waseda University17, Max Planck Society18, Nihon University19, Shonan Institute of Technology20, Japan Atomic Energy Agency21
TL;DR: This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun's shadow observed in the TeV cosmic-ray flux, and it is found that the intensity deficit in the simulated Sun’s shadow is very sensitive to the corona magnetic field structure.
Abstract: We report on a clear solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun's shadow, using the potential field source surface model and the current sheet source surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun's shadow observed in the TeV cosmic-ray flux.
47 citations
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Hirosaki University1, University of Tokyo2, Hebei Normal University3, Tibet University4, Shandong University5, Yunnan University6, Kanagawa University7, Utsunomiya University8, Konan University9, Waseda University10, Yokohama National University11, Shinshu University12, Chinese Academy of Sciences13, Tsinghua University14, Saitama University15, National Institute of Informatics16, Sakushin Gakuin University17, Max Planck Society18, Nihon University19, Shonan Institute of Technology20
TL;DR: In this paper, the authors used a low threshold air-shower core detector named YAC to measure the heavy elements around the knee, which indicated the dominance of nuclei heavier than helium.
45 citations
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TL;DR: PAMELA data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy and find that the spectral shapes of these two species are different and cannot be described well by a single power law.
Abstract: 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 12 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
900 citations
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TL;DR: In this paper, the authors discuss the possible mechanisms for the generation of cosmological magnetic fields, discuss their evolution in an expanding universe filled with the cosmic plasma and provide a critical review of the literature on the subject.
Abstract: We review the possible mechanisms for the generation of cosmological magnetic fields, discuss their evolution in an expanding Universe filled with the cosmic plasma and provide a critical review of the literature on the subject. We put special emphasis on the prospects for observational tests of the proposed cosmological magnetogenesis scenarios using radio and gamma-ray astronomy and ultra-high-energy cosmic rays. We argue that primordial magnetic fields are observationally testable. They lead to magnetic fields in the intergalactic medium with magnetic field strength and correlation length in a well defined range. We also state the unsolved questions in this fascinating open problem of cosmology and propose future observations to address them.
662 citations
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TL;DR: In this article, a review of air shower data related to the mass composition of cosmic rays above 10 15 eV is presented, and the analysis of these experimental results in terms of primary mass is highly susceptible to the theoretical uncertainties of hadronic interactions in air showers.
377 citations
01 Apr 2002
TL;DR: In this article, direct and indirect measurements of cosmic rays are reviewed, with emphasis given to the understanding of the knee in the energy spectrum, and the data are compared to contemporary models for the knee.
Abstract: Results from direct and indirect measurements of cosmic rays are reviewed. Emphasis is given to the understanding of the knee in the energy spectrum. The data are compared to contemporary models for the knee. Implications on the present understanding of the origin of galactic cosmic rays are discussed.
319 citations
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TL;DR: In this paper, a review summarizes recent developments in the understanding of high-energy cosmic rays focusing on galactic and presumably extragalactic particles in the energy range from the knee (1015 eV ) up to the highest energies observed ( > 10 20 eV).
300 citations