The occurrence of complexity in the solar cycle, as monitored by the sunspot area butterfly diagram, is investigated by means of the
natural orthogonal composition (NOC) technique and information theory approach. Although the butterfly diagram may be reconstructed
using only two modes as already found in other papers for the Hale cycle, on deeper investigation it is possible to notice
that the high variability, complexity, and stochasticity observed during the solar cycle are missing. A full description of the complex
evolution of the solar cycle requires at least 30 modes. We show that these modes identify two different dynamical regimes, whose
existence is also confirmed by the analysis of the Lyapunov exponents of the associated principal components. We suggest that the
existence of these two physical dynamical regimes is at the origin of the dynamical complexity of the solar cycle. We attempt a
discussion of these dynamical regimes also in terms of a nearly stable dynamo process described by the first two modes and a local
superficial turbulent dynamo responsible for the more stochastic features observed in the solar cycle.
Key words. Sun: activity – Sun: sunspots – methods: statistical – chaos
The occurrence of complexity in the solar cycle, as monitored by the sunspot area butterfly diagram, is investigated by means of the
natural orthogonal composition (NOC) technique and information theory approach. Although the butterfly diagram may be reconstructed
using only two modes as already found in other papers for the Hale cycle, on deeper investigation it is possible to notice
that the high variability, complexity, and stochasticity observed during the solar cycle are missing. A full description of the complex
evolution of the solar cycle requires at least 30 modes. We show that these modes identify two different dynamical regimes, whose
existence is also confirmed by the analysis of the Lyapunov exponents of the associated principal components. We suggest that the
existence of these two physical dynamical regimes is at the origin of the dynamical complexity of the solar cycle. We attempt a
discussion of these dynamical regimes also in terms of a nearly stable dynamo process described by the first two modes and a local
superficial turbulent dynamo responsible for the more stochastic features observed in the solar cycle.
Key words. Sun: activity – Sun: sunspots – methods: statistical – chaos
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