An econometric investigation of the sunspot numbers since the year 1700

Solar activity, as measured by the yearly revisited time series of sunspot numbers (SSN) for the period 1700–2014 undergoes in this paper a triple statistical and econometric checkup. The conclusions are that the SSN sequence: (1) is best modeled as a signal that features nonlinearity in mean and variance, long memory, mean reversion, ‘threshold’ symmetry, and stationarity; (2) is best described as a discrete damped harmonic oscillator which linearly approximates the flux-transport dynamo model; (3) its prediction well into the 22nd century testifies of a substantial fall of the SSN centered around the year 2030. All of these conclusions are achieved by making use of modern tools developed in the field of Financial Econometrics and of two new proposed procedures for signal smoothing and prediction. Published in September 2015, Advances in Space Research, Solar and Heliospheric Physics, Vol.56, Issue 5, Pages 992-1002.