Coronal Mass Ejections

Abstract

Coronal mass ejections are seen as bright features that move outward through the solar corona at speeds from 10 to about 2,000 km s^-1. They involve the expulsion of substantial quantities of plasma from large regions of the corona. The spectacular nature of the largest mass ejections is illustrated in Figure 5.1 by a time sequence of four images obtained on 1989 October 24 with the coronagraph flown on the Solar Maximum Mission (SMM) spacecraft. In these and other SMM coronagraph images used in this chapter, the solar disc is indicated by the dashed circle within the shadow of the instrumental occulting disc. The arrow at the center of the sun points northward along the solar rotation axis and the short radial line crossing the solar disc indicates the location of the heliographic equator. The vertical streak in the middle of each image is a defect in the coronagraph detector system; such defects will be seen on most SMM coronagraph images.