A Representation of the Sunspot Cycle

L T H O U G H sunspots had been observed occasionally back to ancient times, their study may be said to date from their rediscovery by Galileo in the spring of 1610 with the then newly invented telescope. Since then much has been written about their nature, their periodicities and possible influence on human affairs. The purpose of the study reported on in this paper was to analyze the components of the sunspot data and thereby to reconstruct a curve which would not only represent the variation in sunspot numbers from 1749 to date but would also be consistent with times of maxima and minima from 1610 to 1749. A number of attempts along this line have been made in the past, 3 - 4> s' 6- 9- 11 all of which have neglected the data previous to 1749 and all have used a slightly different method of analysis. It is believed that the agreement in the present study is somewhat better than in those of the past; nevertheless, no claim is made for any great accuracy in predicting future sunspot activity. Harmonic analysis based on a fraction of a period is always a source of danger and, furthermore, we have no assurance that all the components of the sunspot curve are periodic functions. 8 In fact, some papers have appeared in which each cycle was treated as a more or less independent outburst. 2 , 1 0 , 12·13 Nevertheless, because of the long base line over which agreement is obtained in this present study, it is hoped that the results may not be too much in error for at least a few cycles.