Hemispheric Distribution of Long-term Solar Activity: Coronal Bright Points from 1996 to 2023

Abstract Coronal bright points (CBPs) are ubiquitous in the Sun and represent a key class of solar magnetic activities. They offer valuable insights into unresolved problems in solar cycle studies, but their hemispheric distribution in different cycles and for different types has not been understood yet. Based on the observations of the Extreme-ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory mission, a total of more than 1.8 million CBPs are identified in full-disk images spanning the period 1996–2023, and the hemispheric distribution of bright and dim CBPs is studied in detail. Our main results are as follows: (1) Bright CBPs are significantly correlated with sunspot activity, whereas dim CBPs are in antiphase with the solar activity cycle, suggesting that bright and dim CBPs have different characteristics and sources. (2) Two types of CBPs both exhibit significant hemispherical asymmetry, implying that the north–south asymmetry of CBPs is a real observational phenomenon and not a random fluctuation. (3) Before and after the solar cycle maximum, the slope of the normalized and absolute asymmetry indices of both bright and dim CBPs changes the sign or value, which suggests that the hemispheric distribution of CBPs might be influenced by the reversal of magnetic field polarity. (4) The cumulative trend and difference of bright and dim CBPs both display an intercycle- and intracycle-dependent pattern. Our analysis results are beneficial for elucidating the underlying mechanism of hemispheric variation of small-scale magnetic structures in solar corona, and could offer a new perspective on the fundamental physical processes responsible for the global and local dynamo theories.

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