  The recent observations of Singh et al. (2012) have shown multiple plasma
ejections and the intermittent nature of magnetic reconnection in the solar
chromosphere, highlighting the need for fast reconnection to occur in highly
collisional plasma. However, the physical process through which fast magnetic
reconnection occurs in partially ionized plasma, like the solar chromosphere,
is still poorly understood. It has been shown that for sufficiently high
magnetic Reynolds numbers, Sweet-Parker current sheets can become unstable
leading to tearing mode instability and plasmoid formation, but when dealing
with a partially ionized plasma the strength of coupling between the ions and
neutrals plays a fundamental role in determining the dynamics of the system. We
propose that as the reconnecting current sheet thins and the tearing
instability develops, plasmoid formation passes through strongly,
intermediately, and weakly coupled (or decoupled) regimes, with the time scale
for the tearing mode instability depending on the frictional coupling between
ions and neutrals. We present calculations for the relevant time scales for
fractal tearing in all three regimes. We show that as a result of the tearing
mode instability and the subsequent non-linear instability due to the
plasmoid-dominated reconnection, the Sweet-Parker current sheet tends to have a
fractal-like structure, and when the chromospheric magnetic field is
sufficiently strong the tearing instability can reach down to kinetic scales,
which are hypothesized to be necessary for fast reconnection.
