Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1768682 | Advances in Space Research | 2005 | 5 Pages |
Abstract
Daily Be-7 concentrations in air at the height of 15 m are continuously observed at 38°15.2â²N, 140°20.9â²E, between 2000 and 2001. The average concentration and the relative standard deviation were 4.0 mBq/m3 and 50% in 2000-2001, respectively. The Be-7 concentrations increased 2.5% with the decrease in the sunspot numbers by 6.7% for the term of two years. From the power spectral analysis, the periodicity of 26 days is shown for the daily Be-7 concentrations. The folding analysis indicates that the time variation of the Be-7 concentration is similar to that of the ground-based neutron counting rate, and the phase delay for the minimum portion of Be-7 concentration was roughly 8 days to the maximum sunspot number. These results indicate that the Be-7 concentrations in the air at ground level have 26 day periodicity as a component of time variations and the time variation is caused by the solar modulation of galactic cosmic rays, which corresponds to the variation of the sunspot number due to the rotation of the sun.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Space and Planetary Science
Authors
H. Sakurai, Y. Shouji, M. Osaki, T. Aoki, T. Gandou, W. Kato, Y. Takahashi, S. Gunji, F. Tokanai,