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Solar Influences on the North Atlantic Oscillation by Wavelet-Based Multifractal Analysis

There is increasing interest in the relation between the solar activity and climate change. Regarding the solar activity, the fractal property of the sunspot number (SSN) has been studied by many previous works. In general, fractal properties have been observed in the time series of the dynamics of complex systems.

In this study, the authors examined the relationship among the solar activity, total ozone, and the North Atlantic Oscillation (NAO) from a viewpoint of multi-fractality and investigated the change of multifractal behavior of the SSN, F10.7 flux, geomagnetic aa, total ozone, NAO, the global temperature, and NH sea ice area indices by the multifractal analysis using the wavelet transform. For this purpose, they also illustrated the change of multifractality by plotting the τ-function and used the wavelet coherence.

The results showed that the solar activity related to the NAO, by observing the matching in monofractality or multifractality of these indices. When the SSN increased, the solar activity became stable and the NAO also became stable. When the SSN became maximum, the fractality of the SSN, F10.7 flux, geomagnetic aa, and NAO indices changed from multifractality to monofractality and those states became stable for most of the solar cycles. Also, an increase of a fluctuation was observed in a coupled chaotic system just before chaos synchronization. When the SSN became maximum, the fluctuations became large and multifractality became strong, and a change from multifractal to monofractal behavior was observed in the SSN, F10.7 flux, geomagnetic aa, and NAO indices. The strong interactions of the solar flux, geomagnetic activity, total ozone, and NAO occur in the SSN maximum. The strong interactions were inferred from the similarity of fractality changes and the wavelet coherence. The influence of the solar activity on the NAO was shown from a viewpoint of multi-fractality.

In short, these findings will contribute to the research on the effects of the solar activity on climate change.


Article by Fumio Maruyama, et al, from Japan.

Full access: http://suo.im/4LEOAK

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