  A new Self-Organized Criticality (SOC) model is introduced in the form of a
Cellular Automaton (CA) for ion temperature gradient (ITG) mode driven
turbulence in fusion plasmas. Main characteristics of the model are that it is
constructed in terms of the actual physical variable, the ion temperature, and
that the temporal evolution of the CA, which necessarily is in the form of
rules, mimics actual physical processes as they are considered to be active in
the system, i.e. a heating process and a local diffusive process that sets on
if a threshold in the normalized ion temperature gradient R/L_T is exceeded.
The model reaches the SOC state and yields ion temperature profiles of
exponential shape, which exhibit very high stiffness, in that they basically
are independent of the loading pattern applied. This implies that there is
anomalous heat transport present in the system, despite the fact that diffusion
at the local level is imposed to be of a normal kind. The distributions of the
heat fluxes in the system and of the heat out-fluxes are of power-law shape.
The basic properties of the model are in good qualitative agreement with
experimental results.
