The hydromagnetic nature of solar coronal mass ejections

The Sun is our star, the nearest star. The solar coronal mass ejection (CME) is one of the most violent activities in the solar atmosphere. When a CME takes place, it releases 1015-16 g of plasma from the low corona into the solar wind, to disturb the near-Earth space and hence bring adverse consequences if the CME is directed toward us. In this paper we present a brief summary of our current understanding of the origin of CMEs. We believe that it is the twisted magnetic field that stores enough free magnetic energy for a CME to erupt. We argue that the accumulation of magnetic helicity in the corona plays an important role: not only will it bring in free magnetic energy storage as a natural result, but also it will result in a CME-type eruption as an unavoidable event in the process of a coronal evolution.