EDP Sciences
Free access
Volume 506, Number 3, November II 2009
Page(s) 1381 - 1391
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361/200811074
Published online 22 July 2009
A&A 506, 1381-1391 (2009)
DOI: 10.1051/0004-6361/200811074

Complexity in the sunspot cycle

G. Consolini1, R. Tozzi2, and P. De Michelis2

1  INAF – Istituto di Fisica dello Spazio Interplanetario, 00133 Roma, Italy
    e-mail: consolini@ifsi-roma.inaf.it
2  Istituto Nazionale di Geofisica e Vulcanologia, 00143 Roma, Italy

Received 2 October 2008 / Accepted 5 June 2009

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

© ESO 2009