Computer studies on powerful magnetic energy conversion by the spontaneous fast reconnection mechanism

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Abstract
On the basis of the spontaneous reconnection model, computer simulations study the physical mechanism by which magnetic energy, initially stored in a current sheet system, is released into plasma energies. For the uniform resistivity model, the Sweet–Parker mechanism is eventually set up with the diffusion region becoming longer with time. It is the Ohmic heating ηJ2 in the diffusion region that plays the dominant role in releasing the magnetic energy. Attached to the diffusion region, a long plasmoid is formed and propagates like a large‐amplitude Alfvén pulse, where the generator and motor effects are canceled along the plasmoid boundary. For the anomalous resistivity model, the fast reconnection mechanism is eventually set up with the diffusion region remaining to be localized near an X neutral point. It is the powerful motor effect [u⋅(J×B)≳0] along the slow shock layers that drastically releases the stored magnetic energy. A large‐scale plasmoid distinctly swells, so that the ambient magnetic fields are compressed (by the generator effect), and the enhanced magnetic energy is then reduced by the strong motor effect in the backward half of the plasmoid. The slow shocks extend with time from near the X point, leading to a drastic catastrophe for the overall magnetic field system.