Magnetic field lines (white) on a colour contour plot of electron flow speed. Magnetic field lines flow in towards the centre of the view and merge. After they merge, the magnetic field line tension flings the plasma to the left and right away from the origin. The electron diffusion region corresponds to the red, yellow and green regions along the centre. Once reconnection starts, this region grows with time, reaching a length of 20 ion skin depths, much longer than previously thought.
Size of electron diffusion region