  The understanding of magnetic reconnection in three-dimension (3D) is far
shallower than its counterpart in two-dimension (2D) due to its potential
complication, not to mention the evolving of the spontaneously growing
turbulence. We investigate the reason for reconnection acceleration on the
characters and development of diffusion regions and sheared 3D energy modes
(energy modes that are not parallel to the anti-parallel magnetic fields)
during the turbulence building stage. We found that multiple reconnection
layers emerge due to the growth of 3D sheared tearing instability. Diffusion
regions on adjacent reconnection layers form an inflow-outflow coupling that
enhances the local reconnection. Further coupling of the existing energy modes
breeds new energy modes near the current sheet edge. As reconnection layers
span and interact with each other across the whole current sheet, global
magnetic energy consumption accelerates. The significant contribution of 3D
energy modes and their interaction to the reconnection rate enhancement seems
to be independent on magnetic diffusivity. On the other hand, the global guide
field changes the layout of 3D reconnection layer thus determines whether the
system is fast-reconnection-preferable.
