  We study a 2D cellular automaton (CA) model for the evolution of coronal loop
plasmas. The model is based on the idea that coronal loops are made of
elementary magnetic strands that are tangled and stressed by the displacement
of their footpoints by photospheric motions. The magnetic stress accumulated
between neighbor strands is released in sudden reconnection events or
nanoflares that heat the plasma. We combine the CA model with the Enthalpy
Based Thermal Evolution of Loops (EBTEL) model to compute the response of the
plasma to the heating events. Using the known response of the XRT telescope on
board Hinode we also obtain synthetic data. The model obeys easy to understand
scaling laws relating the output (nanoflare energy, temperature, density,
intensity) to the input parameters (field strength, strand length, critical
misalignment angle). The nanoflares have a power-law distribution with a
universal slope of -2.5, independent of the input parameters. The repetition
frequency of nanoflares, expressed in terms of the plasma cooling time,
increases with strand length. We discuss the implications of our results for
the problem of heating and evolution of active region coronal plasmas.
