Solar cycle variation of simple and complex active regions

Solar active regions (ARs) emerge on the Sun’s photosphere and they frequently produce flares and coronal mass ejections which are among major space weather drivers. Therefore, studying ARs can improve space weather forecast.

The Mount Wilson Classification has been used since 1919 in order to group groups ARs according to their magnetic structures. In this study, we investigated the magnetic classification of 4797 ARs and their cyclic variation, using our daily approach for the period of January 1996 to December 2018.

We show that the monthly number of the simple ARs (SARs) attained their maximum during first peak of the solar cycle, whereas more complex ARs (CARs) reached their maximum roughly two years later, during the second peak of the cycle. We also demonstrate that the total abundance of CARs is very similar during a period of four years around their maximum number. We also studied the latitudinal distributions of SARs and CAR in northern and southern solar hemispheres and show that the independent of the complexity type, the distributions are the same in both hemispheres.

Furthermore, we investigated the earlier claim of increase in number of CARs due to the decrease in ARs latitudinal band. Here we show that, contrary to this claim, CARs attained their maximum number before the latitudinal band started to decrease in both northern and southern hemispheres.