From the International Flare Patrol data over 1972-2010, we conducted statistical investigations into Ha solar flares. 91% of all the flares occurring on the Sun were established to refer to low-power flares, of which the bulk is SF flares (64%). In terms of evolution features, low-power flares do not differ from major solar flares. They, as well as powerful flares,are accompanied by filament activations and disappearances, have the explosive phase,and multiple intensity bursts. Among them, there are flares covering sunspot umbrae, two-ribbon, and white flares. From the data on temporal parameters of more than 85,000 flares, we determined the mean times of rise and decay, and durations for solar flares of various types, classes of area and of importance. The lifetime of 94.6% flares was established not to exceed 60 minutes; for powerful flares, this time is no more than 8.3 hours. On rarest occasions, flares may last about 12 hours. The most short-lived are the flares with one increasedbrightness center in the flare region; the longest are two-ribbon flares and the flares accompanied by multiple intensity bursts. Explosive type flares possess the shortest flash-phase. Such flares, in most cases, have one increased-brightness center, and they are most often observed in sites of filament disappearance.
展开▼
