First proposed scenario. Two of the magnetic field lines with different degrees of twist are plotted, which belong to the flux rope underlying the filament. At the left, the flux rope is in equilibrium, while at the right it rises. The filament material is represented by the shadowed regions, where the colours indicate whether the material is blue- or redshifted relative to the observer (who is located above the top of the image). The dashed line is the photospheric polarity inversion line.