A Simple Model to Describe Solar Cycle Periodicities below 11 Years

Together with the main 11-year cycle, solar activity also displays intracycle periodicities. A simple nonlinear model that describes the 11-year solar cycle with subperiodicities can be derived from the usual α – ω dynamo theory in the form of a Van der Pol equation with a forcing term. In this paper the results obtained from the Van der Pol oscillator describing the amplitude modulations and periodicities observed from the data set of the global daily coronal emission of the Fe xiv line at 530.3 nm are presented.