  Solar filaments/prominences exhibit rotational motion during different phases
of their evolution from their formation to eruption. We have observed the
rotational/vortical motion in the photosphere near the ends of ten filaments
during their initial phase of eruption, at the onset of the fast rise phase.
All the filaments were associated with active regions. The photospheric
vortical motions we observed lasted for 4--20 minutes. In the vicinity of the
conjugate ends of the filament the direction of rotation was opposite, except
for two cases, where rotational motion was observed at only one end point. The
sudden onset of a large photospheric vortex motion could have played a role in
destabilizing the filament by transporting axial flux into the activated
filament thereby increasing the outward magnetic pressure in it. The outward
magnetic pressure may have pushed the filament/flux rope to the height where
the torus instability criterion was satisfied, and hence it could have caused
the filament instability and eruption.
