The Waldmeier Effect in Sunspot Cycles

Abstract

We discuss two aspects of the Waldmeier Effect, namely (1) the rise times of sunspot cycles are anti-correlated to their strengths (WE1) and (2) the rates of rise of the cycles are correlated to their strengths (WE2). To avoid overlapping effect and the lack of single peaks in some cycles, we carefully define rise times to study WE1. From analysis of four different data sets, we conclude that WE1 exists in all, although the significance levels are poor in some cases due to insufficient data. We also find strong evidence for WE2 in all the data sets. We study this effect theoretically by introducing suitable stochastic fluctuations in our regular solar dynamo model. Some preliminary results are presented.