  We give a theoretical description of avalanche-like dynamics of magnetic flux
in the critical state of "hard" type-II superconductors using a model of a
one-dimensional multijunction SQUID that well reproduces the main magnetic
properties of these objects. We show that the system under consideration
demonstrates the self-organized criticality. The avalanches of vortices
manifest themselves as jumps of the total magnetic flux in the sample. The
sizes of these jumps have a power-law distribution. Our results are in
qualitative agreement with experiments.
