摘要: This paper examines a possible mechanism for the initiation of coronal mass ejections by means of the eruption of magnetic flux beneath a closed magnetic structure analogous to a coronal helmet structure. Anumerical computation shows that such an eruption deforms the helmet structure into an expanding bright "loop", followed by a dark cavity due to the expansion of the erupted magnetic field. The morphology and the internal structure of the loop are mainly determined by the background magnetic field whereas its ejective speed is largely controlled by the rate of flux ejection. The present model identifies the loop-like mass ejections with the above plasma structures moving with the frozen-in magnetic field and it may well explain some general properties of such ejections.