Coronal Holes during the Period of Maximum Asymmetry in the 24th Solar Activity Cycle

The current 24th solar activity cycle differs substantially from previous cycles in a number of parameters, especially in terms of a large asymmetry in the number of sunspots (Sp) during the second peak of its maximum. From March 2013 through December 2015. a significant predominance was observed in the number of sunspots in the southern hemisphere. The main purpose of this paper is to clarify the behavior of coronal holes (CH) during this period. This study is based on an analysis of data recorded by the 19.3 nm channel of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO). Two methods of detecting CH (simplified visual and the Spatial Possibilistic Clustering Algorithm (SPoCA)) are used to obtain time series of daily total CH areas for the Sun's northern and southern hemispheres. The two methods agree on the estimated areas of the CH. A comparison of the observed variations in the areas of the CH with the numbers and areas of sunspots showed that in this period, activity predominates in the S-hemisphere both in terms of sunspots and in terms of the total CH area. Here a rise in the area of the CH follows a rise in sunspot activity by roughly half a year. It is suggested that the CH and spots are associated elements of the overall magnetic activity of the Sun, in qualitative agreement with studies of activity complexes. A dipole poloidal field in the form of open CH fields and a toroidal field in the form of active regions are related on time scales substantially shorter than the solar cycle.