抚仙湖太阳观测和研究基地知识库

The Sun exhibits a complex spatial and temporal chaotic behavior, and can be descried by a goal of observing solar phenomena.This study is an attempt to investigate the short-, mid- and long-term periodicities by analysing the time-series of coronal index for the time interval from 1 January 1939 to 31 December 2008. By means of the combination of empirical mode decomposition (EMD) and morlet wavelet transform (MWT) tools, the analysis results show the existence of a variety of prominent short- and mid-term periodicities in coronal index. Apart from the 11-year Schwabe cycle and the 22-year magnetic cycle which are the fundamental periodicities and are found in this solar indicator, the rotational periodicities of 26.4 and 29.44 days, the annual variation, and the near-three years periodicity are also observed. In addition, the 17-year periodicity corresponding to 'solar full-disk activity cycle' is observed. Our study shows that the combination of EMD and MWT techniques for the periodic analysis of solar-, space-, and terrestrial- time series is fairly powerful.