  We show the existence of a system size coherence resonance effect for an
ensemble of globally coupled excitable systems. Namely, we demonstrate
numerically that the regularity in the signal emitted by an ensemble of
globally coupled Fitzhugh-Nagumo systems, under excitation by independent noise
sources, is optimal for a particular value of the number of coupled systems.
This resonance is shown through several different dynamical measures: the time
correlation function, correlation time and jitter.
