Turbulent relaxation in the vortex lattice

The time dependence of flux patterns of an untwinned YBa2Cu3O$_{7-\delta}$ single crystal showing the “meandering instability” is observed at $T= 65\;{\rm K}$ using magneto-optical imaging. When applying a reversed external field to a remanent state, along the front of penetrating antivortices, flux droplets are formed which can separate from the flux front and move in a spiral-like fashion. It is shown that the vortices along the flux front are in fast motion. These observations are discussed using a newly developed theory. Furthermore, the flux patterns are analyzed in terms of flux creep