Hemispheric distribution of coronal mass ejections from 1996 to 2020

Abstract

ABSTRACT Solar magnetic structures are known to be asymmetrically distributed between the two hemispheres. To date, the hemispheric variations of the coronal mass ejections (CMEs) at different latitudes, in different cycles, and for different types (regular and specific events) are still unclear. From the list of white-light CMEs in the Coordinated Data Analysis Web catalogue, we investigate the hemispheric asymmetry of high-latitude and low-latitude CMEs in the time interval from 1996 January to 2020 December. The main results are shown for the following: (1) in each hemisphere, regular CMEs are significantly correlated with solar activity, particularly for low latitudes. However, specific CMEs are not correlated with solar activity; (2) the main reason for the hemispheric asymmetry of the CMEs is attributable to specific CMEs, not regular CMEs. The hemispheric asymmetry of high-latitude CMEs appears to have little connection to that of low-latitude CMEs; (3) for the total and specific CMEs, the relationship between the absolute asymmetry index at high and low latitudes has a positive correlation prior to the cycle maximum, but a negative correlation after the cycle maximum; and (4) the dominant hemisphere, the cumulative trend, and the amplitude of the total, specific, and regular CMEs in cycle 23 differ from those in cycle 24. Our analysis results could be useful for understanding the cyclical variation of the magnetic free energy during different solar cycles, and could also provide insight into more physical processes responsible for the solar–terrestrial relationship.