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.
Information Processing Time Series Analysis empirical mode decomposition Morlet Wavelet Transform Complex Control System
Deng Linhua
Yunnan Observatories,Chinese Academy of Sciences,Kunming 650011,P.R.China;Key Laboratory of Solar Activity,National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100012,P.R.China;Key Laboratory of Astronomical Optics & Technology,Nanjing Institute of Astronomical Optics & Technology,Chinese Academy of Sciences,Nanjing 210042,P.R.China;Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University),Ministry of Education,Nanjing 210093,P.R.China;University of Chinese Academy of Sciences,Beijing 100049,P.R.China