An emerging flux trigger mechanism for coronal mass ejections

Observations indicate that reconnection-favored emerging flux has a strong correlation with coronal mass ejectons (CMEs). Motivated by this observed c orrelation and based on the flux rope model, an emerging flux trigger mecha nism is proposed for the onset of CMEs, using two-dimensional magnetohydrod ynamic (MHD) numerical simulations : when such emerging flux emerges within the filament channel, it cancels the magnetic field below the flux rope, l eading to the rise of the flux rope (owing to loss of equilibrium) and the formation of a current sheet below it. Similar global restructuring and a r esulting rise motion of the flux rope occur also when reconnection-favored emerging flux appears on the outer edge of the filament channel. In either case, fast magnetic reconnection in the current sheet below the flux rope i nduces fast ejection of the flux rope (i.e., CME). It is also shown that th e nonreconnecting emerging flux, either within the filament channel or on t he outer edge of the channel, makes the flux rope move down, i.e., no CMEs can be triggered. Although the present two-dimensional model can not provid e many details of the largely unknown three-dimensional processes associate d with prominence eruptions, it shows some observational features such as t he height-time profile of erupting prominences. Most importantly, our model can well explain the observed correlation between CMEs and the reconnectio n-favored emerging flux.