Melting of moving vortex lattices in systems with periodic pinning

We study numerically the effects of temperature on moving vortex lattices i nteracting with periodic pinning arrays. For low temperatures the vortex la ttice flows in channels, forming a hexatic structure with long-range transv erse and longitudinal ordering. At higher temperatures, a transition to a s mectic state occurs where vortices wander between channels and longitudinal order is lost while transverse order remains. At the highest temperatures the vortex lattice melts into an isotropic liquid.