Spectral analysis of coronal Fe XIV emission at 530.3 nm: Temporal behaviour of 27-day and Rieger periodicities during solar cycles 17–23

Abstract

The temporal variation of both the ≈ 27-day as well as the Rieger periodicity in Fe XIV solar corona spectral emission observed at 530.3 nm is investigated during the interval from 1 January 1940 to 31 December 2008. This time period overlaps with various phases of solar cycles 17 to 23. Daily mean values of Fe XIV emission at each annual interval are spectrally analysed using Morlet wavelet and Lomb–Scargle techniques to obtain the temporal behaviour of particularly the ≈ 155-day Rieger as well as the ≈ 27-day solar rotation periodicities. Results obtained in this study indicate substantial power in both the ≈ 27-day as well as the Rieger periodicity varying on an annual basis while applying the 95 % statistical confidence level. This analysis revealed that both the ≈ 27-day as well as the Rieger periodicity in Fe XIV exhibit their strongest power around solar maximum. In particular it has been found that the power of the Rieger periodicity exceeds that of the ≈ 27-day period during the maxima of all solar cycles, while on the other hand the power of the ≈ 27-day synodic periodicity dominates during the minima of most cycles. This paper reports for the first time the relative powers in the temporal behaviour of both the ≈ 27-day as well as the ≈ 155-day Rieger periodicity in coronal Fe XIV at 530.3 nm.