We attempt to propose a method for automatically detecting the solar filament
chirality and barb bearing. We first introduce the unweighted undirected graph
concept and adopt the Dijkstra shortest-path algorithm to recognize the
filament spine. Then, we use the polarity inversion line (PIL) shift method for
measuring the polarities on both sides of the filament, and employ the
connected components labeling method to identify the barbs and calculate the
angle between each barb and the spine to determine the bearing of the barbs,
i.e., left or right. We test the automatic detection method with H-alpha
filtergrams from the Big Bear Solar Observatory (BBSO) H-alpha archive and
magnetograms observed with the Helioseismic and Magnetic Imager (HMI) on board
the Solar Dynamics Observatory (SDO). Four filaments are automatically detected
and illustrated to show the results. The barbs in different parts of a filament
may have opposite bearings. The filaments in the southern hemisphere (northern
hemisphere) mainly have left-bearing (right-bearing) barbs and positive
(negative) magnetic helicity, respectively. The tested results demonstrate that
our method is efficient and effective in detecting the bearing of filament
barbs. It is demonstrated that the conventionally believed one-to-one
correspondence between filament chirality and barb bearing is not valid. The
correct detection of the filament axis chirality should be done by combining
both imaging morphology and magnetic field observations.Comment: 20 pages, 7 figures, accepted for publication in RA
