Evidence From Sunspot Statistics That the Sun Has Changed Activity Modes During the Last Ten Cycles (Abstract)

Volume 29 number 1 (2001)

France B. Berger

4 Russell Drive Harwich, MA 02645

James C. Carlson

P.O. Box 56 Harwich, MA 02645

Abstract

(Abstract only) An examination of sunspot cycle data suggests that the Sun has occupied two activity modes in the years for which the most reliable records are available. Evidence for this is found, first, in the graph of the yearly averages of the daily sunspot numbers dating from 1882 to the present; and second, from statistical comparisons of various data sets for the years 1882 to 1946 (Early period) with their counterparts for 1947 to 1996 (Late period). Examination of a plot of the running correlation coefficient between the number of days per year when the Sun’s disk was devoid of spots and the yearly average of the daily sunspot numbers, starting in 1882, is quite consistent with the two-mode hypothesis and a transition around 1946. The most compelling quantitative evidence for separate modes comes from comparing the Early with the Late daily sunspot numbers averaged over each cycle. The former (the average over cycles 13–17) is 42.0 ± 8.7. The latter (cycles 18–22) is 78.2 ± 13.1. The separation of the averages is 36.2 ± 15.7, or 2.3 standard deviations. Finding distributions this compact compared to their separation lends considerable support to the correctness of the hypothesis.