Detection and segmentation for chromosphere brightpoints by CLPNet

Chromosphere bright points (CBPs) are small and bright magnetic structures, which are the reflection of the cross sections of the magnetic flux tubes crossing the chromosphere. Accurate detection and segmentation of CBPs enable large-scale data acquisition and then feature extraction. In this paper, we propose the CLPNet model based on the LPNet architecture. By restructuring the global feature extractor and patch network module, we improve the segmentation accuracy and small-object detection. The Ca II H image-series in the quiet regions from the Solar Optical Telescope (SOT) on board Hinode are used to construct a training set containing about 2800 CBPs and two test sets both containing about 1200 CBPs. The precision, recall, F1-score are 0.840, 0.831 and 0.835, respectively. For the segmentation effect at the pixel level, the pixel precision, pixel recall and pixel F1-score and mIoU value are 0.751, 0.713, 0.732 and 0.637, respectively. This indicates that CLPNet demonstrates a commendable level of efficiency and accuracy in both detection and segmentation tasks. The compactness is used for classifying the morphology of CBPs. Specifically, CBPs exhibiting compactness less than or equal to 1.13 are regarded as point-like CBPs, which could correspond to a single slender flux tube. Otherwise, CBPs are regarded as non-point-like CBPs, which could correspond to the interaction of several slender flux tubes. There are differences in features between point-like and non-point-like CBPs. The mean compactnesses are 1.06±0.04 and 1.20±0.07, respectively. The mean equivalent diameters are 201±50 and 279±60 km, respectively. The mean values of the maximum intensity contrast are 1.14±0.47 and 1.54±0.66 ⟨IQS_Ca⟩, respectively. The mean values of eccentricity are 0.60±0.14 and 0.78±0.11, respectively. This research provides a more precise methodology for the comprehensive study of CBPs, offering novel insights into the physical phenomena occurring on the chromosphere and then establishing a quantitative foundation for three-dimensional modeling of magnetic flux tubes and investigations into coronal heating mechanisms.