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Introduction

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  1. 29th International Cosmic Ray Conference Pune(2005)Do Be-10 and C-14 give us the information about cosmic rays in the past?I. Nikitina, Yu. Stozhkova, V. Okhlopkovb, N. Svirzhevskya(a) P.N. Lebedev Physical Institute, Russian Academy of Sciences, 119991, Leninsky Prospect 53, Moscow, Russia(B) D.V. Skobeltsyn Institute of Nuclear Physics, Moscow State University, Vorobjevy gory, Moscow, 119992, RussiaPresenter: Yu. Stozhkov(stozhkov@fian.fiandns.mipt.ru),

  2. 29th International Cosmic Ray Conference Pune(2005)Do Be-10 and C-14 give us the information about cosmic rays in the past?I. Nikitina, Yu. Stozhkova, V. Okhlopkovb, N. Svirzhevskya(a) P.N. Lebedev Physical Institute, Russian Academy of Sciences, 119991, Leninsky Prospect 53, Moscow, Russia(B) D.V. Skobeltsyn Institute of Nuclear Physics, Moscow State University, Vorobjevy gory, Moscow, 119992, RussiaPresenter: Yu. Stozhkov(stozhkov@fian.fiandns.mipt.ru),

  3. In the atmosphere cosmic rays (CR) produceBe-10, C-14 and other radionuclides. It is commonly supposed that the concentrationsof Be-10 in polar iceand C-14 in tree rings are good proxies of CR fluxes impinging on the top of the atmosphere. But before the precipitation on the Earth’s surface theseelements spend several years in the atmosphere. The atmospheric processes play an essential role in the radionuclideprecipitationand destroy the relationship between CR and these radionuclide concentrations. Introduction

  4. Kepler’s Supernova Remnant 10-year averages of C-14 data over the period of 859 - 1900; Yearly Be-10 data from Greenland for the period of 1423 - 1985; 22-year smoothed Be-10 data from Antarctica over the period of 859 - 1973

  5. There is a large difference in the mean values of Be-10 concentrations obtained from Greenland and Antarctic ice cores. The <Be-10> concentrations in Greenland and Antarctica calculated over periods shown in the Figure are 1.05 and 3.86 (in the units of 104 atoms/g) accordingly. The correlation between Be-10 data from Greenland and C-14 data is low. After exclusion of the trend in C-14 dataset the maximum value of a correlation coefficient was 0.49 with a time shift of 6 years.

  6. Correlation coefficient between Antarctic Be-10 data and C-14 data vs. time shift (C-14  Be-10).

  7. The averaged amplitude of 11-solar cycle in Be-10 data from Greenland ice cores was found as where and where the values of CRzminand CRzminare the values of Be-10 concentrations during minima and maximaof sunspot number periods accordingly. Then the mean fractional ratio values <A> vs. different time shifts between Be-10 and solar activity data were calculated. and

  8. The values of A time shift. Filled circles – over the period since 1900 till 1986. Boxes – over the period since 1711 till 1900. Dashed curve – average.

  9. During the last 250 years we has not observed SN explosions in our Galaxy. Although ~ 2 such events could have been observed if we take the part of Galaxy restricted by the distance r 5 kpc from the solar system and suggest that light absorption in this part is weak.

  10. The maximum mean value of <A> for Be-10data calculated over the period since 1711 till 1986 is 0.31 witha 4-year time shift. The mean value of <A> for CR (particles with E > 0.1 GeV), calculated over the period since 1954 till 1981 is 2.44  0.08. It means that the amplitude of 11-year modulation in CR is much bigger than in Be-10 produced by CR. The facts given above could be explained by the weather (climate changes) influence.

  11. One of the main weather parameter is the average temperature of the atmosphere surface layer. The temperature data were reduced to the values of dT = <dT> - T. The time dependences of Be-10 and dT data and correlation between them are shown below.

  12. Be-10 concentration (thick curve) and dT temperature fluctuation (thin curve) vs. time.

  13. The relationship between Be-10 concentration and dT surface temperature data.The correlation coefficient between these data isr = – 0.54. The slope is – 0.08  104Be-10 atoms/g per 1C. In relative values it is 7.6 % per 1C.

  14. Conclusions The different sets of data on radionuclides produced by CRs are agreed with each other not so well. The amplitude of variation in Be-10 data is much lower than that of CR in the 11-year solar cycle. The atmospheric effects play a main role in the variations of Be-10 and C-14 concentration. It is better to use the relationship of CR fluxes with sunspot number (correlation coefficient is ~ -0.9) to calculate the CR fluxes in the past.

  15. References J. Beer, J., S. Tobias, and N. Weiss, Solar Phys., 181, 237 (1998). J. Beer et. all, The Sun as a Variable Star: Solar and Stellar Irradiance Variations (eds. J.M. Pap, C. Frahlich, H.S. Hudson and S.K. Solanki), Cambridge University Press, 291 (1994). M. Stuiver, P. J. Reimer and T. F. Braziunas, Radiocarbon, 40, 1127 (1998). Yu.I. Stozhkov, V.P. Okhlopkov, N.S. Svirzhevsky, Solar Physics, 224, 323 (2004). I. Hansen et al., JGR, 104, No. D24, 30,997 (1999).

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