Is the large-scale sidereal anisotropy of the galactic cosmic-ray intensity really instable at TeV energies?

Amenomori, M.; Bi, X. J.; Chen, D.; Chen, Wen-Yun; Cui, S. W.; Danzengluobu,; Ding, L. K.; Ding, X. H.; Feng, C.; Feng, Z.; Feng, Z. Y.; Gou, Q. B.; Guo, H. W.; Guo, Y. Q.; He, H. H.; He, Ze; Hibino, K.; Hotta, N.; Hu, Haibing; Huang, J.; Jia, H. Y.; Jiang, Linhua; Kajino, F.; Kasahara, K.; Katayose, Y.; Kato, C.; Kawata, K.; Labaciren,; Le, G. M.; Li, A. F.; Li, W. J.; Liu, C.; Liu, J. S.; Lü, H.; Meng, X. R.; Mizutani, K.; Munakata, K.; Nanjo, H.; Nakamura, Masaki; Ohnishi, M.; Ohta, I.; Ozawa, S.; Qian, X. L.; Qu, X. B.; Saito, T.; Sakata, M.; Sako, T. K.; Shao, J.; Shibata, M.; Shirai, T.; Sugimoto, H.; Takita, M.; Tan, Y. H.; Tateyama, N.; Torii, Shoji; Tsuchiya, H.; Udo, S.; Wang, H.; Wu, H. R.; Xue, L.; Yamamoto, Y.; Yang, Z.; Yasue, S.; Yuan, A. F.; Yuda, T.; Zhai, L. M.; Zhang, H. M.; Zhang, J. L.; Zhang, X. Y.; Zhang, Y.; Zhang, Yi; Zhang, Ying; Zhaxisangzhu,; Zhou, Xu

doi:10.1016/j.astropartphys.2012.06.005

Cited by 7 publications

(4 citation statements)

References 26 publications

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“…A so-called Large Scale Anisotropy (LSA) has been measured by several experiments (e.g. Tibet-ASγ [92], Milagro [93], ARGO-YBJ [94], IceCube [95]) showing an approximate dipole-like feature with an excess region between 40 • −90 • in right ascension (around the heliospheric tail) and a deficit between 150 • −240 • (in the direction of the galactic north pole), referred to as tail-in and loss cone regions respectively.…”

Section: Flux Anisotropiesmentioning

confidence: 99%

Selected Topics in Cosmic Ray Physics

Aloisio

Blasi

Mitri

et al. 2018

Multiple Messengers and Challenges in Astroparticle Physics

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The search for the origin of cosmic rays is as active as ever, mainly driven by new insights provided by recent pieces of observation. Much effort is being channelled in putting the so called supernova paradigm for the origin of galactic cosmic rays on firmer grounds, while at the highest energies we are trying to understand the observed cosmic ray spectra and mass composition and relating them to potential sources of extragalactic cosmic rays. Interestingly, a topic that has acquired a dignity of its own is the investigation of the transition region between the galactic and extragalactic components, once associated with the ankle and now increasingly thought to be taking place at somewhat lower energies. Here we summarize recent developments in the observation and understanding of galactic and extragalactic cosmic rays and we discuss the implications of such findings for the modelling of the transition between the two.

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Section: Flux Anisotropiesmentioning

confidence: 99%

Selected Topics in Cosmic Ray Physics

Aloisio

Blasi

Mitri

et al. 2018

Multiple Messengers and Challenges in Astroparticle Physics

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“…However, all other observatories can improve the anisotropy iteratively, by using the first estimate of δI (1) to re-evaluate the relative acceptance by the relative intensity I 1 + δI (1) in the next step and optimize the anisotropy to δI (2) , and so forth. This provides an iterative reconstruction scheme [52,53], that have been applied to data of Tibet-ASγ [54,44,55] and ARGO-YBJ [56].…”

Section: Reconstructionmentioning

confidence: 99%

Origin of small-scale anisotropies in Galactic cosmic rays

Ahlers

Mertsch²

2017

Progress in Particle and Nuclear Physics

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The arrival directions of Galactic cosmic rays (CRs) are highly isotropic. This is expected from the presence of turbulent magnetic fields in our Galactic environment that repeatedly scatter charged CRs during propagation. However, various CR observatories have identified weak anisotropies of various angular sizes and with relative intensities of up to a level of 1 part in 1,000. Whereas largescale anisotropies are generally predicted by standard diffusion models, the appearance of small-scale anisotropies down to an angular size of 10 • is surprising. In this review, we summarise the current experimental situation for both the large-scale and small-scale anisotropies. We address some of the issues in comparing different experimental results and remaining questions in interpreting the observed large-scale anisotropies. We then review the standard diffusive picture and its difficulty in producing the small-scale anisotropies. Having set the stage, we review the various ideas and models put forward for explaining the small-scale anisotropies.

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“…It is interesting to compare our data with the Tibet AS-γ array results given in Amenomori et al (2012), which report the amplitude of the "loss-cone" deficit over 8 years, from 2000 to 2007, for three values of the primary median energy (4.4, 6.2, and 11 TeV), compared with a Milagro measurement at 6 TeV performed in about the same time interval. According to Tibet AS-γ data, the deficit amplitude (defined as the difference between unity and the relative intensity at the minimum of the best-fit curve of the harmonic analysis) is stable during the period under study with a value in the range ∼0.0010-0.0013, while the Milagro data show a linear increase of the amplitude with time, going from ∼0.0014 in 2001 to ∼0.0034 at the end of 2006.…”

Section: Anisotropy Versus Energymentioning

confidence: 85%

“…The temporal behavior of the anisotropy is more controversial. While Milagro reported a steady increase of the intensity at a median energy of about 6 TeV from 2000 to 2007 (corresponding to a decrease of the solar activity; Abdo et al 2009), the Tibet AS γ experiment did not observe any significant difference in the anisotropy intensity at ∼5 TeV for nine years of data from 1999 to 2008 (Amenomori et al 2010(Amenomori et al , 2012. On the other hand, a weak correlation between the anisotropy amplitude at an energy of ∼0.6 TeV and the solar activity has been found in a 22 year muon data set (Munakata et al 2010).…”

Section: Introductionmentioning

confidence: 91%

Argo-Ybj Observation of the Large-Scale Cosmic Ray Anisotropy During the Solar Minimum Between Cycles 23 and 24

Bartoli¹,

Bernardini²,

Bi³

et al. 2015

ApJ

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This paper reports on the measurement of the large-scale anisotropy in the distribution of cosmic-ray arrival directions using the data collected by the air shower detector ARGO-YBJ from 2008 January to 2009 December, during the minimum of solar activity between cycles 23 and 24. In this period, more than 2 × 10 11 showers were recorded with energies between ∼1 and 30 TeV. The observed two-dimensional distribution of cosmic rays is characterized by two wide regions of excess and deficit, respectively, both of relative intensity ∼10 −3 with respect to a uniform flux, superimposed on smaller size structures. The harmonic analysis shows that the large-scale cosmic-ray relative intensity as a function of R.A. can be described by the first and second terms of a Fouries series. The high event statistics allow the study of the energy dependence of the anistropy, showing that the amplitude increases with energy, with a maximum intensity at ∼10 TeV, and then decreases while the phase slowly shifts toward lower values of R.A. with increasing energy. The ARGO-YBJ data provide accurate observations over more than a decade of energy around this feature of the anisotropy spectrum.

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Is the large-scale sidereal anisotropy of the galactic cosmic-ray intensity really instable at TeV energies?

Cited by 7 publications

References 26 publications

Selected Topics in Cosmic Ray Physics

Selected Topics in Cosmic Ray Physics

Origin of small-scale anisotropies in Galactic cosmic rays

Argo-Ybj Observation of the Large-Scale Cosmic Ray Anisotropy During the Solar Minimum Between Cycles 23 and 24

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