  We use spectro-polarimetric data recorded by Hinode to analyze the magnetic
field configuration of a part of a sunspot (AR 10923) where a bundle of
penumbral filaments are intruding into its umbra. We want to explore the role
of the sunspot magnetic configuration in the formation and kinematics of the
fine-structures, such as umbral dots and light bridges, inside the sunspot
umbra. Both direct inferences from polarization Stokes profiles and the
inversion results using the SIR code indicate an aligned magnetic field
configuration in the umbra where moving umbral dots are easily formed at the
leading edges of the rapidly intruding penumbral filaments. We suggest that the
magnetic field topology is rearranged leading to the observed aligned magnetic
field lines via magnetic reconnection process by which a part of the magnetic
energy is converted into thermal and kinetic energy. This new configuration
causes the umbral fine-structures to form easily and more frequently.
