  We analyze the properties of Large Scale Shocks in a cosmological volume of
size 103Mpc/h simulated with the public 1.0.1 release of the ENZO code.
Different methods to identify and characterize shocks in post processing are
discussed together with their uncertainties. Re-ionization affects the
properties of shocks in simulations, and we propose a fitting procedure to
model accurately the effect of re-ionization in non--radiative simulations,
with a post--processing procedure. We investigate the properties of shocks by
means of a procedure which uses jumps in the velocity variables across the
cells in the simulations and this allows us to have a viable description of
shocks also in relatively under-dense cosmic regions. We derive the
distributions of the number of shocks and of the energy dissipated at these
shocks as a function of their Mach number, and discuss the evolution of these
distributions with cosmological time and across different cosmic environments
(clusters, outskirts, filaments, voids). In line with some previous numerical
studies (e.g. Ryu et al.2003, Pfrommer et al.2006) relatively weak shocks are
found to dominate the process of energy dissipation in the simulated cosmic
volume, although we find a larger ratio between weak and strong shocks with
respect to previous studies. We estimate the rate of injection of CR at Large
Scale Shocks by adopting injection efficiencies taken from previous numerical
calculations. The flux dissipated in the form of CR within the whole simulated
volume at the present epoch is about 20 per cent of the thermal energy
dissipated at shocks; this fraction is smaller within galaxy clusters.
