Zoom on NOAA 11589. a) Photospheric mapping of QSLs from the computation of the squashing degree, Q. White regions are related to magnetic field lines that are open on the scale of the extrapolation domain and where Q is not computed. b) Selected magnetic field lines and c) photospheric footprints of the identified QSLs plotted over the photospheric Q-map. The field lines labeled L_{i = { 1,2,3,4 }} indicate possible candidates for the four post-flare loops labeled in Fig. 4. d) Flare ribbons labeled with respect to the identified QSLs footprints. The white arrow indicates the northern direction.