Analysis of the piecewise de-trended data corresponding to Fig. 6. Panels A_k,k = 1,2,3,4 show the evolution of de-trended intensity (shown with asterisks) for the first four bright blobs (1 to 4), respectively (see Fig. 4) fitted by sin functions (solid lines). Panels B_k,k = 1,2,3,4 show the fitting errors with dashed lines. The dotted horizontal lines represent the average error for the whole considered time span and the solid horizontal lines show the average error corresponding to the shorter time span up to approximately 12:28 UT.