Sketch of the detrending process. A series of consecutive vector magnetograms (e.g., the B_z component) labeled with different time-steps (t₁, t₂, t₃, ...), is shown on the left. The black line (data) in the top right panel represents the temporal evolution of one pixel in this time-series (marked in red in the left panel). The blue line is a third-order polynomial fit to the data. Bottom right panel: detrended time-series, which shows the residuals of the data with respect to the fit.