  We perform real-space imaging of propagating magnetic domains in the
fractional quantum Hall system using spin-sensitive photoluminescence
microscopy. The propagation is continuous and proceeds in the direction of the
conventional current, i.e. opposite to the electron flow direction. The
mechanism of motion is shown to be connected to polarized nuclear spins around
the domain walls. The propagation velocity increases when nuclei are
depolarized, and decreases when the source-drain current generating this
nuclear polarization is increased. We discuss how these phenomena may arise
from spin interactions along the domain walls.
