  Through a direct comparison between numerical simulations in two and three
dimensions, we investigate topological effects in reconnection. A simple
estimate on increase in reconnection rate in three dimensions by a factor of
$\sqrt{2}$, when compared with a two-dimensional case, is confirmed in our
simulations. We also show that both the reconnection rate and the fraction of
magnetic energy in the simulations depend linearly on the height of the
reconnection region. The degree of structural complexity of a magnetic field
and the underlying flow is measured by current helicity and cross-helicity. We
compare results in simulations with different computational box heights.
