Correlation between decay rate and amplitude of solar cycles as revealed from observations and dynamo theory

Abstract

Using different proxies of solar activity, we have studied the following features of the solar cycle: i) The linear correlation between the amplitude of cycle and its decay rate, ii) the linear correlation between the amplitude of cycle n and the decay rate of cycle (n−1), and iii) the anti-correlation between the amplitude of cycle n and the period of cycle (n−1). Features ii) and iii) are very useful because they provide precursors for future cycles. We have reproduced these features using a flux-transport dynamo model with stochastic fluctuations in the Babcock–Leighton α effect and in the meridional circulation. Only when we introduce fluctuations in meridional circulation, are we able to reproduce different observed features of the solar cycle. We discuss the possible reasons for these correlations.