Simulated light curves (left column) and corresponding rms–flux binned data. Middle column shows the rms–flux data taken from full light curves with linear fits as dashed lines with a being linear coefficients of equation rms = aψ + b (where ψ is the flux). The two lower-right panels show linear fits to individual simulated light-curve subsamples (outbursts). The upper-right square panel is a detail of the upper middle panel. Flux is in arbitrary units (au). A – constant mass accretion rate, B – increasing mass accretion rate with correspondingly increasing number of flickering flares per light-curve subsegment, C – the same as B but with constant flickering flare number per light-curve subsegment and an additional vertical offset is added instead, D and E – the same as B and C, respectively, but light-curve subsegments are randomly redistributed in order to simulate the outbursts. See the text for details.