Top: illustration of the converging flux model parameters, as used in combination with the results of magnetic balltracking. The X-ray brightening starts at time t₂. This time is used to define the interaction distance d^∗. The barycentre is the weighted average of the position of the tracking balls used in the algorithm. Bottom: example with case C2b of the weighted average of the tracked position. The green circle is the barycentre of the 3 balls labeled 19, 22, 94. The blue diamond is the barycentre of ball 56; the only one tracking the white patch so it is at the same position as the ball centre (red dot).