Coronal mass ejections observed during the solar maximum mission - Latitude distribution and rate of occurrence

Sixty-five coronal mass ejections have been identified in a systematic examination of white-light coronal images obtained between March and September 1980 by the coronagraph/polarimeter flown on the solar maximum mission spacecraft. These ejections were more uniformly distributed in position angle (or 'projected' solar latitude) than the similar events observed during the Skylab mission in 1973-1974; 27 percent of the solar maximum mission mass ejections were centered at positions more than 45 deg from the solar equator. The average rate of occurrence of the observed mass ejections for the entire solar maximum mission epoch, based on the assumption that one coronagraph image per spacecraft orbit is sufficient for detection, was 0.9 + or 0.15 per 24-hour day. Application of the same sampling assumption to the Skylab data set leads to a rate of 0.75 per 24-hour day and thus a change in this rate from the Skylab era (on the declining phase of sunspot cycle 20) to solar maximum mission (near the maximum of sunspot cycle 21) of only approximately 20 percent.