  As a key to undertanding the basic mechanism for fast reconnection in solar
flares, plasmoid-induced-reconnection and fractal reconnection are proposed and
examined. We first briefly summarize recent solar observations that give us
hints on the role of plasmoid (flux rope) ejections in flare energy release. We
then discuss the plasmoid-induced-reconnection model, which is an extention of
the classical two-ribbon-flare model which we refer to as the CSHKP model. An
essential ingredient of the new model is the formation and ejection of a
plasmoid which play an essential role in the storage of magnetic energy (by
inhibiting reconnection) and the induction of a strong inflow into reconnection
region. Using a simple analytical model, we show that the plasmoid ejection and
acceleration are closely coupled with the reconnection process, leading to a
nonlinear instability for the whole dynamics that determines the macroscopic
reconnection rate uniquely. Next we show that the current sheet tends to have a
fractal structure via the following process path: tearing, sheet thinning,
Sweet- Parker sheet, secondary tearing, further sheet thinning... These
processes occur repeatedly at smaller scales until a microscopic plasma scale
(either the ion Larmor radius or the ion inertial length) is reached where
anomalous resistivity or collisionless reconnection can occur. The current
sheet eventually has a fractal structure with many plasmoids (magnetic islands)
of different sizes. When these plasmoids are ejected out of the current sheets,
fast reconnection occurs at various different scales in a highly time dependent
manner. Finally, a scenario is presented for fast reconnection in the solar
corona on the basis of above plasmoid-induced-reconnection in a fractal current
sheet.
