The data are observations of the longitudinal magnetic field of two large sunspots (AR NOAA 8375 and AR NOAA 8525) which were obtained at BBSO on 1998 November 4 and 1999 May 05, respectively. During the observations, the sunspots were located near the central meridian (AR NOAA 8375 -- N18W06 and AR NOAA 8525 -- N18E02).

Clockwise twist of Halpha filaments around a sunspot in AR NOAA 8375 implies positive helicity, while dark filaments and fibrils in an AR NOAA 8525 indicate that the sunspot had a weak, but noticeable counterclockwise twist (negative helicity).

©BBSO/NJIT Seminar on OCT 99, 2000