A Strong Anticorrelation between Sunspot Maximum and the Lead Time from Hemispheric-average First-spot Emergence to Maximum Epoch: Significant Only in Even Cycles?

Abstract Based on R. Leussu et al.’s data, a tabulation of the epoch of the first sunspot group in each hemisphere (“ t 1−H ”) in Cycles 8–24 was recently performed by J. G. Richard. The hemispheric-average first-group emergence epoch (“ t 1−2H ”) was found to be, as a median, 1.4 yr before sunspot-number minimum (“tSNmin”). Now, in the nine even-numbered cycles, a strong linear anticorrelation (Pearson coefficient r = −0.89) is found between sunspot-number maximum (“SNmax”) and the lead time from t 1−2H to SNmax epoch. Using, instead, the lead time from tSNmin as M. Waldmeier did in 1935 (“Waldmeier effect”), r = −0.84 only. Thus, the effect detected in 1935 appears to physically set in as early as t 1−2H in even cycles: a “first-spot effect.” Neither effect is significant at the 95% confidence level in odd cycles.