Left panel: 2D image composed by the 250 continuum intensity profiles measured along the spatial direction (47′′) and sequentially plotted along the ordinate. The time required to store a Stokes image is 6.7 s. The 250 profiles thus report the evolution of the intensity seen by the spectrograph slit in 28 min. Right panel: one of the 250 continuum intensity profiles (solid line). The dotted line is a smoothed profile obtained by applying a Fourier filter to remove fluctuations at granular scale.