Average EMDs per unit surface area for each type of magnetic structure observed with Yohkoh. The black lines are the two flaring EMDs tested within this work: a time-averaged distribution derived from a sample of eight flares from Class C to X observed with a pair of hard filters with Yohkoh (solid black line; Sect. 3.2.4) and a time-averaged distribution derived from the flares of Class C and M in the sample (dotted black line; Sect. 3.2.5); M flares were also observed with a pair of soft filters.