The emission sources of umbral flashes(UFs) are believed to be closely related to running umbral and penumbral waves,and are concluded to be associated with umbral dots in the solar photosphere. Accurate identification of emission sources of UFs is crucial for investigating these physical phenomena and their inherent relationships. A relatively novel model of shape perception,namely phase congruency(PC),uses phase information in the Fourier domain to identify the geometrical shape of the region of interest in different intensity levels,rather than intensity or gradient.Previous studies indicate that the model is suitable for identifying features with low contrast and low luminance. In the present paper,we applied the PC model to identify the emission sources of UFs and to locate their positions. For illustrating the high performance of our proposed method,two time sequences of Ca II H images derived from the Hinode/SOT on 2010 August 10 and 2013 August 20 were used. Furthermore,we also compared these results with the analysis results that are identified by the traditional/classical identification methods,including the gray-scale adjusted technique and the running difference technique. The result of our analysis demonstrates that our proposed method is more accurate and effective than the traditional identification methods when applied to identifying the emission sources of UFs and to locating their positions.
Six high-resolution TiO-band image sequences from the New Vacuum Solar Telescope(NVST)are used to investigate the properties of intergranular bright points(ig BPs). We detect the ig BPs using a Laplacian and morphological dilation algorithm(LMD) and automatically track them using a threedimensional segmentation algorithm, and then investigate the morphologic, photometric and dynamic properties of ig BPs in terms of equivalent diameter, intensity contrast, lifetime, horizontal velocity, diffusion index, motion range and motion type. The statistical results confirm previous studies based on G-band or TiO-band ig BPs from other telescopes. These results illustrate that TiO data from the NVST are stable and reliable, and are suitable for studying ig BPs. In addition, our method is feasible for detecting and tracking ig BPs with TiO data from the NVST. With the aid of vector magnetograms obtained from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, the properties of ig BPs are found to be strongly influenced by their embedded magnetic environments. The areal coverage, size and intensity contrast values of ig BPs are generally larger in regions with higher magnetic flux. However, the dynamics of ig BPs, including the horizontal velocity, diffusion index, ratio of motion range and index of motion type are generally larger in the regions with lower magnetic flux. This suggests that the absence of strong magnetic fields in the medium makes it possible for the igBPs to look smaller and weaker, diffuse faster, and move faster and further along a straighter path.
Kai-Fan JiJian-Ping XiongYong-Yuan XiangSong FengHui DengFeng WangYun-Fei Yang
