A CATASTROPHE MECHANISM FOR CORONAL MASS EJECTIONS

We use the ideal-MHD equations to show that a coronal current filament can suddenly lose equilibrium if its magnetic energy exceeds a critical value. The loss of equilibrium in our configuration results from an imbalance between magnetic tension and compression, and this imbalance ejects the filament upwards. Near the critical value the equilibrium configuration develops a vertical current sheet attached to the photosphere at the point directly below the filament. When equilibrium is lost, field lines anchored to the photosphere are stretched upwards, and the current sheet rapidly grows longer. Without reconnection in the current sheet, the filament travels only a short distance before reaching a new equilibrium, and the net magnetic energy released is less than 1% of the stored magnetic energy. However, with reconnection, the filament travels upwards indefinitely, and all of the stored energy is released.