Synchronization in Sunspot Indices in the Two Hemispheres
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Historical sunspot records were analyzed by means of nonlinear tools to find synchronization phenomena at different time scales on the Sun. Using cross-recurrence plots it is shown that the north – south sunspot synchronization demonstrates a set of distinct periodic oscillations – 43.29, 18.52, and 7.63 years. Also we have traced the sunspot synchronization on shorter time scales. Very rare and episodic synchronization within half of the Carrington rotation rate was detected. By using the empirical mode decomposition technique the north – south sunspot time series were decomposed into intrinsic oscillatory modes. To determine which modes of the signal are responsible for synchronization we separated them into high- and low-frequency parts. It is shown that phase synchronization is detected only in the low-frequency modes. The high-frequency component demonstrates noisy behavior with amplitude synchronization and strong phase mixing.
KeywordsEmpirical Mode Decomposition Sunspot Area Intrinsic Mode Function Sunspot Activity Wavelet Power Spectrum
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