Here, we represent linear and nonlinear analyses of the daily coronal index (CI) time series of solar activity for the years 1939 to 2008. This index shows the irradiance of the green corona (W s-1) at the wavelength of 530.3 nm belonging to Fe XIV. We studied the periodicity of CI by the Lomb-Scargle periodogram (LSP). It is found the dominant period of the CI is about 11 years. As nonlinear analysis, the multi-scale entropy (MSE) of CI interval time series in different scales follow the q-exponential function after scale three. Moreover, we applied the detrended fluctuation analysis (DFA) to the CI time series to inspect the complexity of the system.
