Anisotropy and Corotation of Galactic Cosmic Rays

Southwest Jiaotong University, Hua-yang, Sichuan, China
Science (Impact Factor: 33.61). 11/2006; 314(5798):439-43. DOI: 10.1126/science.1131702
Source: PubMed


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.

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Available from: Huihai He, Jul 13, 2014
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    • "Our result represents the first measurement in the multi-TeV energy range covering the entire southern hemisphere. The phase of the observed anisotropy matches the one of previously measured cosmic ray anisotropies in the northern hemisphere by the Tibet (Amenomori et al., 2006) and Milagro (Abdo et al., 2009) experiments, indicating that we observe a continuation of the effect measured by these experiments. "
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    ABSTRACT: The IceCube collaboration is building a cubic kilometer scale neutrino telescope at a depth of 2 km at the geographic South Pole, utilizing the clear Antarctic ice as a Cherenkov medium to detect cosmic neutrinos. The IceCube observatory is complemented by IceTop, a square kilometer air shower array on top of the in-ice detector. The construction of the detector is nearly finished with 79 of a planned 86 strings and 73 of 80 IceTop stations deployed. Its completion is expected in the winter 2010/11. Using data from the partially built detector, we present initial results of searches for neutrinos from astrophysical sources such as supernova remnants, active galactic nuclei, and gamma ray bursts, for anisotropies in cosmic rays, and constraints on the dark matter scattering cross section. Further, we discuss future plans and R&D (research and development) activities towards new neutrino detection techniques.
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    • "The Tibet Air Shower experiment has been successfully operated at Yangbajing (90.522 • E, 30.12 • N; 4300 m above sea level) in Tibet, China, since 1990[1]. The experiment was gradually enlarged and upgraded to current scale (Tibet III array) by increasing the number (Tibet I to Tibet II) and density (Tibet II to Tibet III) of detectors. "
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    ABSTRACT: The periodicities of cosmic ray intensity variation are analyzed using Lomb-Scargle Fourier transformation method with about 37 billion cosmic ray events recorded by Tibet III Air Shower Array during the period from November 1999 to November 2005. To eliminate meteorological effect, we adopt East-West subtraction method. According to our analysis, besides the well known solar diurnal, sidereal diurnal and sidereal semi-diurnal periodic modulations at a level of 10¡3, no other periodicity is found to have large enough significance from 1 hour to 2 years in energy range from 3.0 TeV to 12.0 TeV.
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    ABSTRACT: The sidereal anisotropy of galactic cosmic rays with energy in the range 10 14 ∼ 10 16 eV was measured by using extensive air showers (EAS) detected with the Large Area Air Shower (LAAS) experiments. The anisotropy amplitude onto the right ascension axis for EAS arrival directions, was obtained as (2.04±0.50)×10 −3 with a phase −0.1±1.6 hour. The celestial map in equatorial coordinates indicates, however, an isotropic distribution of cosmic rays in this energy region.
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