Simple models of the temporal dynamics of the solar cycle may be constructed and I shall present an example that has the qualitative allure of the variation of the Wolf number. But what fixes the time scale of the cycle? I shall propose an origin for that magic number.
Then I shall mention some arguments for supposing that the origin of the solar activity cycle — the wave of solar excitation — lies in a layer just below the solar cycle called the solar tachocline. Along the way there will be some talk about the chaotic process that may be involved.
Beyond that, the audience will have a choice between my American English and my mauvais francais.