We find that a sunspot with positive polarity had an obvious
counter-clockwise rotation and resulted in the formation and eruption of an
inverse S-shaped filament in NOAA active region (AR) 08858 from 2000 February 9
to 10. The sunspot had two umbrae which rotated around each other by 195
degrees within about twenty-four hours. The average rotation rate was nearly 8
degrees per hour. The fastest rotation in the photosphere took place during
14:00UT to 22:01UT on February 9, with the rotation rate of nearly 16 degrees
per hour. The fastest rotation in the chromosphere and the corona took place
during 15:28UT to 19:00UT on February 9, with the rotation rate of nearly 20
degrees per hour. Interestingly, the rapid increase of the positive magnetic
flux just occurred during the fastest rotation of the rotating sunspot, the
bright loop-shaped structure and the filament. During the sunspot rotation, the
inverse S-shaped filament gradually formed in the EUV filament channel. The
filament experienced two eruptions. In the first eruption, the filament rose
quickly and then the filament loops carrying the cool and the hot material were
seen to spiral into the sunspot counterclockwise. About ten minutes later, the
filament became active and finally erupted. The filament eruption was
accompanied with a C-class flare and a halo coronal mass ejection (CME). These
results provide evidence that sunspot rotation plays an important role in the
formation and eruption of the sigmoidal active-region filament.Comment: 20 pages, 9 figures, Accepted for publication in Ap