Statistical distributions and classification of X-ray flares according to their duration on the sun

The results of the statistical analysis of the GOES data related to the length of the period, during which the X-ray emission of solar flares increases, provide reliable grounds for the objective distinction of different types, sometimes referred to in the literature as typical and nontypical for bimodal classification. The events may be also partitioned into three (“impulsive”, “typical”, and “long duration”) or more “types”. These “types” should be separated from statistical fluctuations in the case of rare events. When the number of analyzed events increases, these fluctuations are gradually smoothed and become less significant, and the distribution of flares according to the duration of their growth is, on the whole, well described by the single lognormal law.