  As modeling of collisionless magnetic reconnection in most space plasmas with
realistic parameters is beyond the capability of today's simulations, due to
the separation between global and kinetic length scales, it is important to
establish scaling relations in model problems so as to extrapolate to realistic
scales. Recently, large scale particle-in-cell (PIC) simulations of island
coalescence have shown that the time averaged reconnection rate decreases with
system size, while fluid systems at such large scales in the Hall regime have
not been studied. Here we perform the complementary resistive MHD, Hall MHD and
two fluid simulations using a ten-moment model with the same geometry. In
contrast to the standard Harris sheet reconnection problem, Hall MHD is
insufficient to capture the physics of the reconnection region. Additionally,
motivated by the results of a recent set of hybrid simulations which show the
importance of ion kinetics in this geometry, we evaluate the efficacy of the
ten-moment model in reproducing such results.
