  Magnetic reconnection is explored on the Terrestrial Reconnection Experiment
(TREX) for asymmetric inflow conditions and in a configuration where the
absolute rate of reconnection is set by an external drive. Magnetic pileup
enhances the upstream magnetic field of the high density inflow, leading to an
increased upstream Alfven speed and helping to lower the normalized
reconnection rate to values expected from theoretical consideration. In
addition, a shock interface between the far upstream supersonic plasma inflow
and the region of magnetic flux pileup is observed, important to the overall
force balance of the system, hereby demonstrating the role of shock formation
for configurations including a supersonically driven inflow. Despite the
specialised geometry where a strong reconnection drive is applied from only one
side of the reconnection layer, previous numerical and theoretical results
remain robust and are shown to accurately predict the normalized rate of
reconnection for the range of system sizes considered. This experimental rate
of reconnection is dependent on system size, reaching values as high as 0.8 at
the smallest normalized system size applied.
