  We report on the photospheric evolution of an intermediate-scale (~4 Mm
footpoint separation) magnetic bipole, from emergence to decay, observed in the
quiet Sun at high spatial 0".3 and temporal (33 s) resolution. The observations
were acquired by the IMaX imaging magnetograph during the first science flight
of the Sunrise balloon-borne solar observatory. The bipole flux content is 6 x
10^17 Mx, representing a structure bridging the gap between granular scale
bipoles and the smaller ephemeral regions. Footpoints separate at a speed of
3.5 km s-1 and reach a maximum distance of 4.5 Mm before the field dissolves.
The evolution of the bipole is revealed to be very dynamic: we found a proper
motion of the bipole axis and detected a change of the azimuth angle of
90{\deg} in 300 seconds. The overall morphology and behaviour are in agreement
with previous analyses of bipolar structures emerging at granular scale, but we
also found several similarities with emerging flux structures at larger scale.
The flux growth rate is 2.6 x 15 Mx s-1, while the mean decay rate is one order
of magnitude smaller. We describe in some detail the decay phase of the bipole
footpoints which includes break up into smaller structures, interaction with
pre-existing fields leading to cancellation but appears to be dominated by an
as-yet unidentified diffusive process that removes most of the flux with an
exponential flux decay curve. The diffusion constant (8 x 10^2 km^2 s-1)
associated with this decay is similar to the values used to describe the large
scale diffusion in flux transport models.
