  We build a minimal, mean-field, model of plasticity of amorphous solids,
based upon a phenomenology of dissipative events derived, in a preceding paper
[A. Lemaitre, C. Caroli, arXiv:0705.0823] from extensive molecular simulations.
It reduces to the dynamics of an ensemble of identical shear transformation
zones interacting via the dynamic noise due to the long ranged elastic fields
induced by zone flips themselves. We find that these ingredients are sufficient
to generate flip avalanches with a power-law scaling with system size,
analogous to that observed in molecular simulations. We further show that the
scaling properties of avalanches sensitively depend on the detailed shape of
the noise spectrum. This points out the importance of developing a realistic
coarse-grained description of elasticity in these systems.
