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Group sunspot number (GSN) values, averaged over decades, were reconstructed for a time interval 8505 BC–AD 1945 using data on the concentration of radiocarbon in tree rings. The prediction of an average level of solar activity was made for the future four decades by means of a nonlinear forecasting method. It was shown that the average activity of the Sun during 2005–2045 would be lower than at present. The given result is compared to the long-term forecasts by other authors. The importance of a paleoastrophysical approach for obtaining a long-term solar prognosis and for revealing the basic characteristics of solar activity change was confirmed. [ABSTRACT FROM AUTHOR]

Relations between basic indices of the Sun and the cosmogenic isotope14C and10Be records were derived using the Artificial Neural Network (ANN) technique. A reconstruction of the sunspot indices and changes in Total Solar Irradiance (TSI) was carried out. Long-term changes in TSI appear in the amplitude modulation of its 11-year cyclic variation as well as in its lower envelope describing variability of the background irradiance of the Sun. According to the reconstruction the irradiance has increased about 2.5 W m-2 since 1441. [ABSTRACT FROM AUTHOR]

Two sets of nitrate (NO3-) concentration data in Central Greenland ice, obtained through the GISP2 collaboration and by the University of Kansas, were analyzed statistically. The two records correlate well over time scales from a few years up to a century. They both contain quasi five-year, decadal and century-type time variations. A quasi five-year periodicity resulting from increases in the mean nitrate concentration before and after maximum sunspot number was confirmed. A tendency of solar proton events to occur more frequently during the rise/dec line phases of the solar cycle may cause a quasi five-year variation. Century-type (60-110 yr) variability in nitrate outstrips the corresponding Gleissberg cycle in sunspots by 12-17 years and changes synchronously (correlates with zero phase shift) with the smoothed length of the solar Schwabe cycle. A significant correlation between century-type periodicities for nitrates in Greenland ice and northern Fennoscandian temperatures was established. The results show that despite a strong dependence on local meteorology, nitrate concentration in ice contains valuable information about global geophysical phenomena in the past. [ABSTRACT FROM AUTHOR]

Long-term changes of the GCR intensity in the heliosphere were analysed making use of records of cosmogenic isotopes abundances (10Be and 14C) in natural archives and neutron monitor data. These data contain information about short-term, 11-year, 22-year, centennial and two-centennial cycles of solar activity. A mechanism to explain the long-term modulation of GCR due to changes in the curvature of the interplanetary magnetic field, resulting from changes in solar activity, is suggested. [ABSTRACT FROM AUTHOR]