Temporal Variability of the Flare Index (1966-2001)

A brief description and the results of the temporal variability of the flare index over the epoch of almost 4 cycles (1966-2001) are presented. Using Fourier and wavelet transforms the long- and the intermediate-term periodicities in the daily flare index data for the total surface and for the northern and the southern hemispheres of the Sun are given in detail. A significant variability was found for all periods including the 150-days and 1.3 years. A brief description and the results of the temporal variability of the flare index over the epoch of almost 4 cycles (1966-2001) are presented. Using Fourier and wavelet transforms the long- and the intermediate-term periodicities in the daily flare index data for the total surface and for the northern and the southern hemispheres of the Sun are presented. A significant variability was found for all periods. The wavelet transform results show that the occurrence of flare index power is highly intermittent in time. A comparison of the results of the Fourier transform and the time-period wavelet transform of the flare index time series has clarified the importance of different periodicities, whether they are or are not the harmonics of the basic ones, as well as the temporal location of their occurrence.