Statistical Analysis of Solar Flare Properties from 1975 to 2017

The statistical analysis of solar flares is essential for understanding their characteristics and properties, serving as a fundamental tool to interpret flare distributions and constrain the physical mechanisms driving their occurrence. In this paper, we investigated the statistical properties of these energetic phenomena over the last four solar cycles, spanning the period from September 1975 to June 2017. Specifically, we analysed the temporal (i.e., waiting time and duration) and energetic (i.e., peak intensity) aspects of soft X-ray (SXR) flares from the GOES catalogue in terms of flare occurrence rates and frequency distributions. We found that (i) the duration of most of the events increases with the increase of the intensity of a given flare, i.e. with its class. X-class flares exhibit a second peak centred around the 80th minute after its formation. (ii) Waiting times, i.e. the interval between the starting time of two consecutive flares, correlate with the solar activity variation within the solar cycle. (iii) In all solar cycles considered here, the flare and CME waiting-time distributions (WTDs) show similar power-law indices of the frequency event distribution and time variation, especially in the tail of the power-law distribution. (iv) Peak-intensity energy does not correlate with the waiting time, contrary to the idea that the more time elapses between two consecutive events the higher the intensity of the flare is.