Temporal and Periodic Variations of Sunspot Counts in Flaring and Non-Flaring Active Regions

Abstract

We analyzed temporal and periodic variations of sunspot counts (SSCs) in flaring (C-, M-, or X-class flares), and non-flaring active regions (ARs) for nearly three solar cycles (1986 through 2016). Our main findings are as follows: i) temporal variations of monthly means of the daily total SSCs in flaring and non-flaring ARs behave differently during a solar cycle and the behavior varies from one cycle to another; during Solar Cycle 23 temporal SSC profiles of non-flaring ARs are wider than those of flaring ARs, while they are almost the same during Solar Cycle 22 and the current Cycle 24. The SSC profiles show a multi-peak structure and the second peak of flaring ARs dominates the current Cycle 24, while the difference between peaks is less pronounced during Solar Cycles 22 and 23. The first and second SSC peaks of non-flaring ARs have comparable magnitude in the current solar cycle, while the first peak is nearly absent in the case of the flaring ARs of the same cycle. ii) Periodic variations observed in the SSCs profiles of flaring and non-flaring ARs derived from the multi-taper method (MTM) spectrum and wavelet scalograms are quite different as well, and they vary from one solar cycle to another. The largest detected period in flaring ARs is $113\pm 1.6~\mbox{days}$ while we detected much longer periodicities ($327\pm 13$, $312 \pm 11$, and $256\pm 8~\mbox{days}$) in the non-flaring AR profiles. No meaningful periodicities were detected in the MTM spectrum of flaring ARs exceeding $55\pm 0.7~\mbox{days}$ during Solar Cycles 22 and 24, while a $113\pm 1.3~\mbox{days}$ period was detected in flaring ARs of Solar Cycle 23. For the non-flaring ARs the largest detected period was only $31\pm 0.2~\mbox{days}$ for Cycle 22 and $72\pm 1.3~\mbox{days}$ for the current Cycle 24, while the largest measured period was $327\pm 13~\mbox{days}$ during Solar Cycle 23.