Lopes,, Ilídio and Passos, Dário (2009), "Evidence for a Long-term Variation of the Dynamo Action Responsible by the Solar Magnetic Cycle", Monthly Notices of the Royal Astronomical Society, 397, 1: 320-324.
Abstract: By using the sunspot time series as a proxy, we have made a detailed analysis of the mean solar magnetic field over the last two and half centuries, by means of a reconstruction of its phase space. We find evidences for a long-term trend variation of some of the solar physical processes (over a few decades), that might be responsible for the apparent erratic behavior of the solar magnetic cycle. The analysis is done by means of a careful study of the axis-symmetric dynamo model equations, where we show that the temporal counterpart of the magnetic field can be described by a self-regulated two dimensional dynamic system, usually known, as a Van der Pol-Duffing oscillator. This work’s results suggests that during the last two and half centuries, the velocity of the meridional flow, vp, and the efficiency of the mechanism responsible for the conversion of toroidal magnetic field into poloidal magnetic field might have su ered variations that can explain the observed variability in the solar cycle.
Keywords: solar dynamo, magnetic fields phase space, solar variability, sunspots, statistics
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