抚仙湖太阳观测和研究基地知识库

Solar filaments, hypothermia and dense structures suspended in the solar corona are formed above the magnetic polarity inversion line. Polar crown filaments (PCFs) at high-latitude regions of the Sun are of profound significance to the periodic variation of solar activities. In this paper, we statistically analyze PCFs by using full disk H alpha data from 1912 to 2018, which were obtained by Kodaikanal Solar Observatory (KODA, India), National Solar Observatory (NSO, USA), Kanzelhohe Solar Observatory (KSO, Austria), Big Bear Solar Observatory (BBSO, USA), and Huairou Solar Observing Station (HSOS, China). We first manually identify PCFs from every solar image based on the centennial data, and record the latitude and other features corresponding to the PCFs. Then we plot the PCF latitude distribution as a function of time, which clearly shows that PCFs rush to the poles at the ascending phase of each solar cycle. Our results show that the filaments drift toward mid-latitude covering solar cycle 15 to 24 after the PCFs reach the highest latitudes. The poleward migration rates of PCFs are calculated in ten solar cycles, and the range is about 0.12 degree to 0.50 degree per Carrington Rotation (CR). We also investigate the north-south (N-S) asymmetry of migration rates and the normalized N-S asymmetry index.