The most complex and interesting magnetic configurations of active regions are considered to draw the attention of the community to the problem of significant systematic deviations from the traditional paradigm of an active region (AR) as an emerging bipolar magnetic flux tube. Observations allow us to make the following assumptions. Large spots (including unipolar ones) are stable, deeply rooted features that serve as channels for the emergence of magnetic structures to the surface. Apparently, the convective flows under the photosphere regularly create a configuration that fundamentally differs from the classical bipolar one: a vertical rope-spot and a system of chaotically entangled loops in the vicinity. It was in such magnetic structures that the most powerful flares occurred in Cycles 23, 24, and 25. According to the Crimean magneto-morphological classification (MMC), such magnetic structures — a rope-spot plus a tangle of loops — belong to the class of the highest complexity, B3. The class B3 groups are responsible for extreme flare activity (Abramenko, 2021). Apparently, everything that does not fit into the classical empirical laws of the AR structure is ordered by itself and bears the ultimate load of the magnetic and flare activity of the Sun.
V. I. Abramenko (Wed,) studied this question.