The evolution of the two variables ni, as resulting from the
integration of Eq. (8), has been reported in Fig. 11. With respect
to the Lotka-Volterra standard model (see Haken 1983; Demirel
2007, and references therein), the variables show a fluctuating
amplitude from one cycle to the other. This behavior resembles
that of the solar cycle, whose amplitude changes from one cycle
to the other. However, in spite of the stochasticity of the coupling