Periodicities in X-ray solar flare occurrences and coherency with daily mean magnetic field

Abstract

ABSTRACT We present here the study of periodic behaviour of occurrence of solar X-ray flares over a wide range of time-scales during four solar cycles. We have also investigated the coherency between the value of daily mean magnetic field of the Sun and solar flare occurrences. Data of daily X-ray flare counts from the GOES network and daily mean magnetic field values from Wilcox Observatory are used to carry out the investigations reported here. Wavelet analysis method was employed to search for and identify the periodicities and to test the coherency between these two values parameters. Oscillatory periods of squared daily mean magnetic field (SMF) and weighted flare count (WFC) were found in the data. The results are consistent with and support the conjecture of the existence of wave guide concept of the solar upper atmosphere. For SMF, we found a common shortest period of 29 d in solar cycles 21–24 while the longer periods are different in different cycles. The longest period found is 890 d during SC 22. In WFC, the shortest period of 25.5 d is identified in SC 22, while the longest one of 950 d is in SC 24.