1. Daily Variation of Cosmogenic Nuclide Be-7 Concentrations in High Altitude Atmosphere at Mt. Chacaltaya in the solar minimum from 2009 Hirohisa Sakurai

2. H. Sakurai 1, T. Sato 1, T. Oe 1, S. Kikuchi 1, Y. Takahashi 1, S. Namai K. Masuda 2, Y. Matsubara 2, H. Miyahara 3, H. Ohashi 4, W. Tavera 5, J. Salinas 5 1. Department of Physics, Yamagata University, 1-4-12 Kojirakawa,Yamagata 990-8560, Japan 2. STEL, Nagoya University, Furocho chikusa-ku, Nagoya 464- 8601, Japan 3. ICRC, The University of Tokyo, 5-1-5 Kashiwanoha Kashiwa- city, 277-8582, Japan 4. Tokyo University of Marine Science and Technology, 4-5-7 Kounan Minato-ku, Tokyo, 108-8477 Japan 5. IIF, Universidad Mayor De San Andres, Calle 27 Cota Cota s/n Campus Universitario, La Paz, Bolivia

3. The cosmogenic nuclides, which are radioisotopes produced in the Earth by cosmic rays, show the solar variations?

4. Stratosphere Geomagnetic fields Solar magnetic fields Cosmic rays 22 Na 14 C 10 Be ７ Be Troposphere 12 km Radioisotopes produced by cosmic rays in the Earth

5. Daily Sampling and Measurement of Be-7 in the atmosphere from 2000 High Volume Air Sampler (HV-100F) Sampling time: 23 hours/day Intake rate: 1000 L/min. Collected filter ・ Glass fiber filter collection efficiency : 99.99% （  m particle ） ・ Glass fiber filter collection efficiency : 99.99% （  m particle ） HPGe detector Measurement time ： 6 hours detection efficiency 2.68% resolution ＠ 1.33MeV 1.69keV Sampling site Altitude: 153 m Latitude: 38.25 Longitude:140.3

6. Yearly profile of Be-7 concentrations

7. Daily profile of Be-7 concentrations @Yamagata Japan

8. Daily sampling of Be-7 in atmosphere at high altitude Expecting observation of short term variations such as 27-day, GLE, Fourbush decrease, CME, etc. Chacaltaya Altitude: 5600 m (16.34° S, 68.12° W)

9. Sampling at Chacaltaya HV-500F

10. Rn-222 Pb-210 Be-7 Stratosphere Troposphere Cosmic Ray origin and Earth origin Rn-222 Pb-210 3.8 day Attempting to remove the environmental effects of the Earth

11. Monthly profiles of Be-7 and Pb-210 concentrations @ Chacaltaya The profiles show a seasonal variation, including different variability.

12. Daily profiles of Be-7 and Pb-210 concentrations @ Chacaltaya Sharp peaks of Be-7 is visible compared to Pb-210

13. Periodic components of Be-7 and Pb-210 concentrations Be-7 Pb-210 For the days from100 to 200, the periodicity around 27-day are different for the Be-7 and the Pb-210.

14. Correlation between daily concentrations of Be-7 and Pb-210

15. Be-7 concentrations subtracting the correlation components between Be-7 and Pb-210 Be-7s show up sharp peaks with a periodic component around 27-day.

16. Summary In addition to the observation of daily Be-7 concentrations in the atmosphere at middle latitude from 2000, we started daily observation of Be-7 concentrations at Chacaltaya in the altitude of 5600 m from September 2009. Using correlation with Pb-210, we tried to extract the variation of Be-7 connecting to short term solar variability for one year data.