Cyclic Variations, Magnetic Morphology, and Complexity of Active Regions in Solar Cycles 23 and 24
Abstract
In this paper, 2046 active regions of solar cycle 23 and 1507 active regions of solar cycle 24 observed during the period from May 1996 to December 2018 have been studied. The sunspot groups are distributed according to the recently proposed magneto-morphological classification. Regular active regions (obeing Hale's polarity law, Joy's law, and having a leading sunspot that prevails over the main tail sunspot), irregular sunspot groups, and unipolar spots have been identified. It is shown that regular active regions make the major contribution to the development of the cycle, which is consistent with the magnetic cycle models. The contribution of irregular sunspot groups is about two to five times smaller (at the cycle maxima) and comparable with the contribution of regular active regions in the cycle minima, which may indicate the joint action of the global mean field dynamo and the fluctuation dynamo. The increase in the number of irregular active regions in the southern hemisphere at the second maximum of each of the studied cycles can be explained by weakening of the toroidal field (produced by the global dynamo) and an increase in the contribution of the fluctuation dynamo to their competitive interaction. Comparison of the curves describing the time dependence of the sunspot group asymmetry index of regular and irregular active regions showed that, when the activity moves to the southern hemisphere, regular active regions are ahead irregular active regions by ~1.5-2 years. The application of the magneto-morphological classification made it possible to detect the alternating activity of the northern and southern hemispheres in both studied cycles; the order of a response of the hemispheres changed from cycle to cycle; the opposite priority with respect to each other was observed for regular and irregular active regions in the given cycle. Comparison of our results with the results on the cyclic variations of sunspot groups of simple and complex magnetic configuration in different hemispheres obtained earlier by other authors showed the following. An increase of the toroidal field produced by the global dynamo makes it difficult to detect asymmetry manifestations and to reveal the effect of the fluctuation dynamo on the magnetic tubes of the active regions.
- Publication:
-
Geomagnetism and Aeronomy
- Pub Date:
- November 2020
- DOI:
- 10.1134/S001679322006016X
- Bibcode:
- 2020Ge&Ae..60..673Z