Hemispheric variation of coronal mass ejections in cycle 23

Abstract

In this paper, we analyse the behaviour of the activity of coronal mass ejection (CME) observed by the Large Angle and Spectrometric Coronagraph Experiment on board the Solar and Heliospheric Observatory (SOHO/LASCO) in cycle 23 from 1997 to 2007 separately for the Northern and Southern hemispheres. The results show the following. (1) At all and low latitudes, the dominant hemisphere of the activity of CME changes from the Northern hemisphere before cycle maxima to the Southern hemisphere after cycle maxima; a southern dominance of the activity of CME is shown to occur in cycle 23. This is consistent with sunspot studies. The relationship between the two lines of the cumulative counts of monthly CME numbers for the Northern and Southern hemispheres is similar to those of monthly sunspot group numbers and sunspot areas. (2) At high latitudes, prior to 2002, the trend of the monthly values of the north-south asymmetry of numbers of CMEs is similar to those of sunspot group numbers and sunspot areas; the relationship between the two lines of the cumulative counts of monthly CME numbers for the Northern and Southern hemispheres is similar to those of sunspot group numbers and sunspot areas. However, after 2001, the trend of dominant hemisphere of the activity of CME at high latitudes is different from those of sunspot group numbers and sunspot areas; the relationship between the two lines of the cumulative counts of monthly CME numbers for the Northern and Southern hemispheres at high latitudes is different from those sunspot group numbers and sunspot areas. Our results seem to suggest that the activity of CME at high latitudes should have close connection with 'rush to the poles'.