Poleward-Motion Aware Network for Poleward Moving Auroral Forms Recognition

Poleward moving auroral forms (PMAFs) are a common dayside auroral phenomenon, and the study of PMAFs has important implications for the exploration of the near-earth space physical processes for geosciences. In the all-sky imager (ASI) image sequence, PMAFs show a tendency to move northward in the northern hemisphere. Therefore, this particular motion pattern can be used for PMAF recognition. Previous works for automatic recognition of PMAFs tend to rely on optical flow. However, both the traditional and the deep learning-based optical flow estimation methods are time- and memory-expensive. In view of the large number of auroral images generated every year, it is impractical to estimate the optical flow for all auroral data with limited computational resources. In this letter, a poleward-motion aware network (PA-Net) is proposed to extract the motion features directly from ASI images. PA-Net computes the correlation between each point in an image and the points at the poleward direction in the following image by means of a poleward-motion aware operation (PA-Operation), to verify whether the point under consideration has undergone poleward motion. In addition, a channel attention mechanism is applied to the features obtained by PA-Operation to suppress information less helpful for recognizing PMAFs. The PA-Net achieves the best performance on the PMAFs recognition dataset over other commonly used action recognition models, validating the superiority of our approach. More importantly, the complicated optical flow estimation is avoided, making it possible to apply the proposed method to large-scale auroral data.