Abstract
In this paper, we present a very important and quite controversial observational property of penumbral filaments that may exhibit twisting motions and change their chirality. Using high-resolution observations from the Solar Optical Telescope on board Hinode, we study the unwinding and twisting motions in the penumbral filaments of active region NOAA 10930. Penumbral filaments, including those to the northwest of the magnetic polarity inversion line (PIL) and those inside the PIL region, are found to make unwinding motions associated with the decrease of their right-handed twists. After unwinding, the filaments inside the PIL region are found to twist continuously to develop left-handed twists in them. Moreover, we find the filament elongating, expanding, splitting, and the screw pitch decreasing in the unwinding process and, getting shorter, shrinking, merging, and the screw pitch increasing in the twisting process. These observational results indicate that penumbral filaments are more inclined to be twisted magnetic flux tubes in nature.