The most important aspect of the solar variability is the 11 year-old cycle, observed in sunspot number variations. This cycle has already been observed in terrestrial records, such as the nuclear activity variations of cosmogenic 14C from tree rings and 10Be in ice sample of polar caps, by sophisticated and high cost methods. By more simple methods, chronologies of tree ring width index recently began to be used as possible record of the solar activity variations in the past. In different locations of the world an influence of the 11 year-old solar cycle was observed in tree growth rings. However, in some other places it was not possible to find the influence of solar activity variations in trees. This led us to perform a study of the possible influence of the solar activity in tree rings from trees grown in South America. The tree rings width determination is made using an optical and computational methodology. This work shows the results obtained at one of the locations studied, at San Francisco of Paula, Brazil. A 65 year-old mean chronology was determined for the tree ring width at this place. For the periodicity search, related to the phenomena of solar origin, the iterative regression analysis method was used. Periods were found at 20.7, 12.8 and 5.6 years related to the cycles 22 year solar (Hale Cycle), 11 year (Schwabe cycle) and the second harmonic of the 11 year cycle. It was also found a 8.6 year period, which is due to periodical thinning down for forest management and preservation.
Tree ring; Solar activity; Spectral Analysis; Iterative regression; Image analysis
