The Solar Cycle Dependence of Coronal Mass Ejections

Abstract

The Solwind white light coronagraph on P78-1 has been making routine observations of the solar corona since 28 March 1979. Data from the 1984/1985 time period has just been analyzed. During this interval, a period of low solar activity, coronal mass ejections (CMEs) occurred at the rate of 0.2– 0.4/day, in contrast to the rate of 1.8/day during the period around solar maximum, 1979–1981. The rate of equatorial CMEs also dropped by the same amount during this period. A class of CMEs, “streamer blowouts”¹, occurred at the same rate during the two epochs. Many of the parameters associated with CMEs, their type, their angular span, central latitude, mass, speed, and energy, have changed from their distributions at solar maximum. During the 1984/1985 period, CMEs are confined to low latitudes, rarely reaching the high latitudes seen during the maximum years. They are smaller, slower, less massive, and less energetic.