Sidereal daily variation of~10 tev cosmic-ray intensity observed by the tibet air shower array

K. Munakata*, T. Hara, S. Yasue, C. Kato, D. L. Hall, S. Mori, M. Amenomori, S. Ayabe, L. K. Ding, K. Hibino, N. Hotta, K. Izu, H. Y. Jia, F. Kajino, K. Kasahara, D. M. Mei, K. Mizutani, K. Morimoto, J. Mu, H. NanjoM. Nishizawa, M. Ohnishi, I. Ohta, T. Ouchi, J. R. Ren, To Saito, M. Sakata, T. Sasaki, Z. Z. Shi, M. Shibata, A. Shiomi, T. Shirai, H. Sugimoto, K. Taira, Y. H. Tan, N. Tateyama, Shoji Torii, H. Wang, Y. Yamamoto, T. Yuda, C. S. Zhang, N. J. Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


We analyze the sidereal daily variation of galactic cosmic-ray intensity observed by the Tibet air-shower (AS) array in one year from January to December 1992. The Tibet AS array can detect the incident direction of each AS and allows us to examine the daily variations in different declination bands on the celestial sphere. The average hourly AS count is 26,372 and the total observation period is 5,651 hours. We analyze the hourly count rates of AS classified into nine cells according to the incident direction of each AS. The hourly count rates are corrected for the atmospheric pressure effect and also for the spurious variation due to the change in the AS size-distribution. We find that the resultant daily variations in sidereal, solar and anti-sidereal time are influenced by a significant variation (∼0.5%) which is common for the viewing directions. It is also found that such common variation is well eliminated in the "difference" variations between the eastern and western cells. From the harmonic analysis of the "difference" variations, it is concluded that there is no significant variation observed in one year of data.

Original languageEnglish
Pages (from-to)599-602
Number of pages4
JournalAdvances in Space Research
Issue number3
Publication statusPublished - 1999
Externally publishedYes

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics


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