A Model for Solar Coronal Mass Ejections

We propose a new model for the initiation of a solar coronal mass ejection(CME). The model agrees with two properties of CMEs and eruptive flares thathave proved to be very difficult to explain with previous models. a) Verylow-lying magnetic field lines, down to the photospheric neutral line, can opentoward infinity during an eruption. b) The eruption is driven solely bymagnetic free energy stored in a closed, sheared arcade; consequently, themagnetic energy of the closed state is well above that of the post-eruptionopen state. The key new feature of our model is that CMEs occur in multi-polartopologies, in which reconnection between a sheared arcade and neighboring fluxsystems triggers the eruption. In this ``magnetic breakout'' model,reconnection removes the unsheared field above the low-lying, sheared core fluxnear the neutral line, thereby allowing this core flux to burst open. Wepresent numerical simulations which demonstrate that our model can account forthe energy requirements for CMEs. We discuss the implication of the model forCME/flare prediction.Comment: Astrophysical Journal latex file, 28 pages, 8 color and 2 b-w figures (gif files