The Waldmeier Effect: An Artifact of the Definition of Wolf Sunspot Number?

Abstract

We show that the well-known “Waldmeier effect,” or anticorrelation between the peak in sunspot number of a cycle and the time from minimum to reach that peak, is not present in sunspot area data averaged in the same way. With a 13-rotation Gaussian running average applied to both sunspot number and sunspot area, we find the correlation between cycle rise time and cycle peak is r=-0.71 for sunspot number and r=10^-4 for sunspot area. Hathaway et al. previously showed that the Waldmeier effect is much weaker (r=-0.34) in sunspot group number. Thus the Waldmeier effect may be specific to only Wolf sunspot number.