Distribution of b_seg values (blue) and that of the F-corona intensity F_inv (orange) measured in different pixels in June 2001. The four rows correspond to pixels at r = 2.6 R_⊙ and ϕ = 119°, r = 4.5 R_⊙ and ϕ = 213°, r = 2.5 R_⊙ and ϕ = 0°, and r = 3.5 R_⊙ and ϕ = 270° (from top to bottom). F_inv is calculated using the inversion method. Left column: evolution of both quantities. Mid and right columns: histogram of the b_seg and F_inv distributions, respectively. In all panels, the y-axis is in the MSB units. The red and green solid lines show the Gaussian fits of the b_seg and F_inv distributions, respectively. The mean and standard deviation of these distributions are shown by means of the blue dashed and orange dotted lines with the corresponding shaded area, respectively. The upper limit of the F-corona intensity and the estimate of its systematic uncertainty inferred from the correlation method are shown for each segment as the blue arrow and the error bar, respectively (see text for details).