a) East and west peak intensities in each frequency-averaged image as a function of the CML at the middle of the 2-h interval corresponding to each image. b) East and west peak intensities – as a proxy of the peak emissivity – as a function of λ_III, derived from a) following the sketch of Fig. 11. Measured values are filled diamonds connected by the solid line. Open diamonds are interpolated from a spline adjustment of east and west measurements separately. Dashed lines are the two resulting independent determinations of the peak emissivity profiles versus λ_III. c), d) east-to-west peak intensity ratios deduced from panels a) and b).