  Recent experiments and realistic flux-gradient-driven computer simulations
provide evidence of plastic flow of flux lines in a superconductor. The
striking videos of the onset of vortex motion vividly illustrate the existence
of flowing "rivers" of quantized magnetic flux that intermittently form,
freeze, and reappear at different locations in the sample. These rivers flow
around "islands" (or domains) of flux lines which are temporarily trapped by
the pinning sites. The shape and size of these temporarily frozen islands
abruptly change over time with every loading-unloading cycle. Videos of the
phenomena are available at: http://www-personal.engin.umich.edu/~nori/
(theory).
