Evolution of field line parameters extracted for a low-lying field line including a downward moving transition region cork. Top row: projections of the field line on the xz-, yz-, and xy-planes. The field line parameters are shown as a function of the coordinate s along the field line, where s = 0 Mm corresponds to the position of the right footpoint of the loop in the panels of the top row. The evolution of the field line parameters is shown for t = 5000  ± 30 s, and the field line evolves from dark blue colors to red colors. The cork positions are indicated by asterisks and the loop apices by crosses.