UVI Image Segmentation of Auroral Oval: Dual Level Set and Convolutional Neural Network Based Approach

Abstract

The auroral ovals around the Earth’s magnetic poles are produced by the collisions between energetic particles precipitating from solar wind and atoms or molecules in the upper atmosphere. The morphology of auroral oval acts as an important mirror reflecting the solar wind-magnetosphere-ionosphere coupling process and its intrinsic mechanism. However, the classical level set based segmentation methods often fail to extract an accurate auroral oval from the ultraviolet imager (UVI) image with intensity inhomogeneity. The existing methods designed specifically for auroral oval extraction are extremely sensitive to the contour initializations. In this paper, a novel deep feature-based adaptive level set model (DFALS) is proposed to tackle these issues. First, we extract the deep feature from the UVI image with the newly designed convolutional neural network (CNN). Second, with the deep feature, the global energy term and the adaptive time-step are constructed and incorporated into the local information based dual level set auroral oval segmentation method (LIDLSM). Third, we extract the contour of the auroral oval through the minimization of the proposed energy functional. The experiments on the UVI image data set validate the strong robustness of DFALS to different contour initializations. In addition, with the help of deep feature-based global energy term, the proposed method also obtains higher segmentation accuracy in comparison with the state-of-the-art level set based methods.

Automatic Auroral Boundary Determination Algorithm With Deep Feature and Dual Level Set

“…The training samples extraction procedure is shown in Figure 4. Two thousand auroral oval pixels and 2000 background pixels (redpoint) are selected randomly from each mask image (Tian et al, 2020). Centering the corresponding pixels (white point) in the UVI images, subimages with the size of 11 × 11 are cropped and served as the training samples.…”