Multi-scale spectral analysis of solar magnetic activity over the past 70 years

The complex spatial and temporal behaviors of long-term solar magnetic activity are an important aspect in solar data set analysis, however it is not an easy work in practice owing to its complex features of solar dynamo process. This paper can improve our knowledges on periodic variations of F10.7 radio flux and sunspot areas by determining the phase relationship between periodic identification and time series decomposition. Several quantitative analysis approaches, including auto-correlation analysis, cross-correlation analysis, and empirical mode decomposition, are combined to study their periodic behavior, phase relationship, and multi-scale modes. The analysis results indicate that the above analysis approaches can be used to decompose a data set into several meaningful components. To sum up, these techniques can be improved to study the periodic features of solar magnetic activity, moreover, it can also identify the natural modes or components, i.e., high-frequency mode, mid-frequency mode, and low-frequency mode.