TEMPORAL VARIABILITY OF THE CORONAL GREEN-LINE INDEX (1947–1998)

摘要

Temporal variability of the coronal index – the `Sun as a star' coronal green-line irradiance – is presented using wavelet transform over the epoch of almost 5 solar cycles. A significant index variability was found for all periods, particularly for the periods of 150 days and 1 year as well as 28 days. Connection of the variability with the phase of solar magnetic activity is outlined. The enhanced power of the 150-day period is dominant before and after the magnetic activity maxima in four out of the five cycles analyzed. To the contrary, no enhanced power was found just during the maxima of all cycles for this period. No clear periodic power behavior was found for the periods at about one year. Substantial rotation period variations of the coronal index up to 5 days take place over relatively short time intervals. A comparison of the results of the Fourier transform and the time-period wavelet transform of the coronal index time series shows that only the application of the wavelet analysis enables one to find the relation between the coronal index variability and the course of the magnetic activity of the Sun.