Analysis of measurements recorded from 14:15 to 16:00 UT on September 27, 2013: radial distances from the Sun vs. corrected times for STEREO-A (in red) and STEREO-B (in blue) assuming the F- (panel a)) and H-component (panel b)). Dotted lines represent results of the polynomial model (Eq. (3)). Dashed lines show the power law model (Eq. (6)). Obtained parameters of both models are shown on the top.