The aim of the present paper {s to provide workers on phenomena which are allied to solar activity with a new table on sunspot-frequency in addition to the tables published by Brunner in the September 1939 issue of this JOURNAl,. Brunner's Table 1, which contains the observed relative sunspot-numbers for all months from January, 1749, to December, 1938, shows that the variations of the spo.t-frequency through the eleven-year cycle are disturbed by secondary short variations. On the assumption that these short variations are of an accidental character (this assumption is supported by the fact that investigations of the curve of observed spot-numbers by periodogram-analysis have revealed no persistent periods shorter than the eleven-year cycle), they can be eliminated by smoothing the observed spot-numbers. The method of smoothing used by the Z•rich astronomers consists in forming the average of every !2 consecutive values of the observed monthly relative numbers and in taking the average of two consecutive averages; this latter {s taken as smoothed relative sunspot-number for the central of the 13 consecutive months whose observed sunspot-numbers have been used for forming the average. If, for example, A denotes the
After an explanation of the method of forecasting based upon the 80-yr sunspot cycle, reasons are given for assuming that the maximum of the present 80-yr cycle now has passed. Starting from this assumption the following predictions can be made: (1) Cycle 21 will be so weak that the highest value of the smoothed monthly means of the sunspot-relative-numbers will lie between 56 and 96; (2) The minimum at the beginning of Cycle 21 will occur during the first half of 1975;(3) Cycle 21 will attain its maximum between 1979.5 and 1980.5; (4) The minimum terminating Cycle 21 will take place during the first half of 1986. A comparison with other predictions shows that they differ considerably from one another; nevertheless, several of them yield results similar to the predictions stated here.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.