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Among Wolf-Rayet stars, those of subtype WN8 are the intrinsically mostvariable. We have explored the long-term photometric variability of thebrightest known WN8 star, WR 40, through four contiguous months oftime-resolved, single-passband optical photometry with the BRIght TargetExplorer (BRITE) nanosatellite mission. The Fourier transform of the observedlight-curve reveals that the strong light variability exhibited by WR 40 isdominated by many randomly-triggered, transient, low-frequency signals. Weestablish a model in which the whole wind consists of stochastic clumpsfollowing an outflow visibility promptly rising to peak brightness upon clumpemergence from the optically thick pseudo-photosphere in the wind, followed bya gradual decay according to the right-half of a Gaussian. Free electrons ineach clump scatter continuum light from the star. We explore a scenario wherethe clump size follows a power-law distribution, and another one with anensemble of clumps of constant size. Both scenarios yield simulated lightcurves morphologically resembling the observed light curve remarkably well,indicating that one cannot uniquely constrain the details of clump sizedistribution with only a photometric light curve. Nevertheless, independentevidence favours a negative-index power law, as seen in many otherastrophysical turbulent media.

The chaotic wind of WR 40 as probed by BRITE