We analysed an X-ray light curve of the dwarf nova RU Peg taken by XMM-Newton with a duration of 46300 s. The power density spectrum has a complicated shape with two red noise and two white noise components , indicating the presence of two turbulent regions .
We developed a statistical ” toy model ” to study light curves with variability produced by an unstable turbulent accretion flow from the inner disc .
Our results are consistent with a disc truncation radius maximally 0.8 \times 10 ^ { 9 } cm .
We found that any fluctuation of the viscous mass accretion at the inner disc are visible as UV and X-ray variations with the same break frequency in the power density spectrum .
This process is generating low frequency variability .
A second break suggests the presence of a faster X-ray variability component which must be generated by another process likely localised between the inner disc and the white dwarf .