Can We Determine the Filament Chirality by the Filament Footpoint Location or the Barb-bearing?

TL;DR

This paper presents an automated method to determine solar filament chirality and barb bearing using image processing and magnetic field data, revealing that the traditional one-to-one correspondence between chirality and barb bearing is invalid.

Contribution

The authors develop a novel automated detection approach combining graph theory and magnetic measurements to accurately identify filament properties.

Findings

Filaments in the southern hemisphere mainly have left-bearing barbs.

Filaments in the northern hemisphere mainly have right-bearing barbs.

The traditional one-to-one correspondence between filament chirality and barb bearing is invalid.

Abstract

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.