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An externally driven magnetic reconnection is simulated for two two‐dimensional MHD models with anomalous resistivity: a closed boundary model where an O‐type neutral point is formed between two X‐type neutral points and an open‐ended model where only an X‐type neutral point is formed. Computer runs have shown the following: (1) X‐shaped (Petschek type) slow shocks are formed. Upon examination of their fine structure it is found that the Rankine‐Hugoniot shock conditions are extremely well satisfied. (2) In the closed boundary case the plasmas entering into the magnetic island through the X‐type neutral points are moderately accelerated along the magnetic island boundaries. Two pairs of vortices are formed internally in such a way that the plasmas are confined. Consequently, the region of the island expands as the pressure increases. As reconnection proceeds, another set of vortices is generated in the expanding island causing the plasma to become turbulent. (3) In the open‐ended case the plasma acceleration is intensified, and strong jet streams are generated on the downstream side of the slow shocks, with the speed approaching the Alfvén speed of the upstream region. Interestingly, the jet streams tend to concentrate preferentially along the plasma sheet boundaries (shock fronts). This is attributed to sharp pressure gradients along the magnetic field lines as a result of slow shocks whose fronts obliquely intersect the field lines. These features of strong jetting of plasmas along the plasma sheet boundaries can explain the recent observations of high‐velocity proton flows in the earth's magnetotail during substorm expansions. (4) Examination of the energy conversion rate has shown that the externally driven magnetic reconnection acts as a powerful magnetic energy converter.
Tetsuya Sato (Sat,) studied this question.