• Radiocarbon, Volume 34, Number 2 (1992)

      Department of Geosciences, The University of Arizona, 1992-01-01
    • Recent and Historical Solar Proton Events

      Shea, M. A.; Smart, D. F. (Department of Geosciences, The University of Arizona, 1992-01-01)
      A study of the solar proton event data between 1954 and 1986 indicates that the large fluence events at the Earth are usually associated with a sequence of solar activity and related geomagnetic storms. This association appears to be useful to infer the occurrence of major fluence proton events extending back to 1934, albeit in a non-homogeneous manner. We discuss the possibility of identifying major solar proton events prior to 1934, using geomagnetic records as a proxy.
    • Reflection of Solar Activity Dynamics in Radionuclide Data

      Blinov, A. V.; Kremliovskij, M. N. (Department of Geosciences, The University of Arizona, 1992-01-01)
      Variability of solar magnetic activity manifested within sunspot cycles demonstrates features of chaotic behavior. We have analyzed cosmogenic nuclide proxy records for the presence of the solar activity signals. We have applied numerical methods of nonlinear dynamics to the data showing the contribution of the chaotic component. We have also formulated what kind of cosmogenic nuclide data sets are needed for investigations on solar activity.
    • Subtle 14C Signals: The Influence of Atmospheric Mixing, Growing Season and In-Situ Production

      Grootes, Pieter M. (Department of Geosciences, The University of Arizona, 1992-01-01)
      Atmospheric 14C concentrations vary with time and latitude. These variations, measured directly on atmospheric samples, or in independently-dated organic material such as tree rings, supply data essential for the calibration of dynamic models of the global carbon cycle. Short variations in the production rate of atmospheric 14C are strongly attenuated in the relatively large atmospheric CO2 reservoir. In-situ production of 14C should be negligible for ages up to 80 ka bp. Background problems in AMS dating are more likely attributable to contamination of very small samples.
    • The Sun as a Low-Frequency Harmonic Oscillator

      Damon, Paul E.; Jirikowic, John L. (Department of Geosciences, The University of Arizona, 1992-01-01)
      Solar activity, as expressed by interplanetary solar wind magnetic field fluctuations, modulates the atmospheric production of 14C. Variations of atmospheric 14C can be precisely established from the cellulose within annual tree rings, an independently dated conservative archive of atmospheric carbon isotopes. Delta-14C time series interpretation shows that solar activity has varied with a recurrence period of 2115 +/- 15 (95% confidence) yr (Hallstattzeit) (Damon & Sonett 1991) over the past 7160 yr. From a non-stationary oscillation solar activity hypothesis, 52 possible spectral harmonics may result from this period. Damon and Sonett (1991) identify powerful harmonics such as the 211.5-yr (Suess) and the 88.1-yr (Gleissberg) cycles as independent fundamental periods. These stronger harmonics appear to modulate the 11-yr (Schwabe) sunspot cycle. Variations in the solar magnetic field, thus, may respond to longer period variations of the solar diameter envelope (Ribes et al. 1989). Such variations would affect solar radiative energy output and, consequently, change total solar irradiance (Sofia 1984).
    • Theoretical and Experimental Aspects of Solar Flares Manifestation in Radiocarbon Abundance in Tree Rings

      Kostantinov, A. N.; Levchenko, V. A.; Kocharov, G. E.; Mikheeva, I. V.; Cecchini, Stefano; Galli, Menotti; Nanni, Terresa; Povinec, Pavel; Ruggiero, Livio; Salomoni, Agostino (Department of Geosciences, The University of Arizona, 1992-01-01)
      We describe our method of determining solar cosmic-ray flux and spectrum in the past, based on the comparison of different cosmogenic isotopes. For the period, AD 1781–1950, we have detected several intervals with a high probability of powerful solar flares.
    • Variation of Radiocarbon Content in Tree Rings During the Maunder Minimum of Solar Activity

      Kocharov, G. E.; Peristykh, A. N.; Kereselidze, P. G.; Lomtatidze, Z. N.; Metskhvarishvili, R. Ya; Tagauri, Z. A.; Tsereteli, S. L.; Zhorzholiani, I. V. (Department of Geosciences, The University of Arizona, 1992-01-01)
      We present here annual data on 14C abundance in tree rings during the Maunder minimum of solar activity (AD 1645–1715). We show that the solar modulation persisted during the minimum. We also compare these data with measurements of 10Be concentration in dated polar ice cores and with records of aurorae recurrence during this time interval.