11-year cycle solar modulation of cosmic ray intensity inferred from C-14 content variation in dated tree ringsA liquid scintillation-photomultiplier tube counter system was used to measure the Delta-C-14 values of 60 tree rings, dating from 1866 to 1925, that were taken from a white spruce grown in Canada at 68 deg N, 130 deg W. A 10-percent variation is found which is anticorrelated with sunspot numbers, although the amplitude of the variation is 2-3 times higher than expected in trees grown at lower latitudes. A large dip in the data at about 1875 suggests an anomalously large modulation of cosmic ray intensity during the 1867-1878 AD solar cycle, which was the most active of the 19th century.
Document ID
19850040706
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Fan, C. Y. (Arizona, University Tucson, AZ, United States)
Chen, T. M. (Arizona Univ. Tucson, AZ, United States)
Yun, S. X. (Beijing University Beijing, People's Republic of China, United States)
Dai, K. M. (Nanjing University Nanjing, People's Republic of China, United States)