Stochastic relaxation oscillator model for the solar cycle

We perform a detailed analysis of the sunspot number time series to reconst ruct the phase space of the underlying dynamical system. The features of th is phase space allow us to describe the behavior of the solar cycle in term s of a simple relaxation oscillator in two dimensions. The absence of syste matic self-crossings suggests that the complexity of the sunspot time serie s does not arise as a consequence of chaos, instead, we show that it can be adequately modeled through the introduction of a stochastic fluctuation in one of the parameters of the dynamic equations.