Two types of coronal bright points as indicators of global and local dynamo processes
Abstract
ABSTRACT The existence of two distinct populations of coronal bright points (CBPs) is investigated based on their intensity and correlation with the solar activity cycle. Using SOHO/EIT 195 Å data spanning solar cycles 23 and 24, a classification method is applied to group CBPs by their maximal intensity. The results confirm the presence of two types of CBPs: bright CBPs that positively correlate with solar activity, likely associated with the global dynamo; and dim CBPs, that show anticorrelation or no correlation, possibly associated with a local turbulent dynamo. In solar cycle 24, characterized by reduced global magnetic activity, the intensity thresholds separating the two populations shift toward lower values, and the number of bright CBPs decreases significantly. An analysis of spatial distributions reveals that bright CBPs follow Spörer’s law, forming a butterfly diagram similar to sunspots, while dim CBPs are more uniformly distributed in latitude. Cross-correlation analysis indicates that bright CBPs lag sunspots by approximately one month, suggesting that they may form from the remnants of decaying active regions. These findings are consistent with magnetohydrodynamic simulations, which predict that small-scale magnetic fields become uncorrelated or anticorrelated with the global magnetic cycle when both local and global dynamos are active. The results provide observational evidence for the combined operation of global and local dynamo processes in generating small-scale coronal magnetic structures.