A search for chaotic behaviour in solar activity.
Abstract
We present an analysis of the behaviour of solar activity and look for the presence of low-dimensional deterministic chaos within it. The original databases for such analysis have been the daily sunspot number (1818-1990) and daily sunspot areas (1874-1989) from which we have constructed twenty different data sets, raw and filtered, displaying the solar and magnetic cycle. We have used the Grassberger-Procaccia algorithm to compute the correlation dimension which, also, has allowed us to obtain the K_2_ entropy and, for some time series, the maximum Lyapunov exponent has also been computed. Our results show that in none of the twenty time series considered does evidence appear of chaotic behaviour, since there is no saturation of the correlation dimension with the embedding dimension and the K_2_ entropy shows a divergent behaviour. A study of previous works which claim this kind of behaviour to be present in solar activity suggests that such a conclusion has been derived from very short scaling regions obtained using low time delays in the computations of the correlation dimension. The behaviour of solar cycle, with periods of low activity, suggests the presence of deterministic chaos and some of its features can be reproduced by means of simple nonlinear dynamo models. However, it seems that for an unambiguous detection of such behaviour, from solar activity data or proxy records, we will have to wait for the availability of longer and reliable data sets covering the periods of reduced activity.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 1994
- Bibcode:
- 1994A&A...290..983C
- Keywords:
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- CHAOTIC PHENOMENA;
- METHODS: DATA ANALYSIS;
- SUN: ACTIVITY;
- SUNSPOTS