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G. S. Choe, C. Z. Cheng (Princeton Plasma Physics Laboratory)
The evolution of a quadrupolar magnetic field system bearing a flux rope is investigated by MHD simulations. In a quadrupolar magnetic configuration with separatrices involved, the magnetic island generated in the central underlying arcade is diamagnetic in a sense that the toroidal current in the magnetic island is in the opposite direction to the subsurface current generating the overlying arcade field. The magnetic island is thus subject to an upward Lorentz force and rises upward pushing the surrounding closed magnetic field toward the overlying arcade. Magnetic reconnection takes place first between these two fields and then between the island field and the overlying arcade field. These reconnection processes remove the closed field barrier surrounding the magnetic island and accelerate the island as well.