Machine Identification Method of Auroral Substorm Onset Time
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摘要: 极光亚暴是地球磁场与太阳风相互作用产生的一种地磁扰动现象, 对于其爆发时点的准确识别有助于深入理解其背后的物理机制. 现有的极光亚暴爆发时点机器识别方法在标准上与人工识别存在差异, 且通常需要经过复杂的图像预处理和人工调参. 为了实现与人工识别标准一致的极光亚暴爆发时点机器识别方法, 设计了两种识别策略, 旨在解决在复现人工识别标准时遇到的图像序列长度不定长问题. 研究采用深度学习方法, 并提出了一种基于CBAM注意力的EfficientNet, 以此作为重要组件来构建模型. 使用Polar卫星1996-1998年的紫外极光图像对模型进行训练, 并在1999-2000年的图像数据上进行测试. 模型识别精确率可达0.98, 识别效率可达36.93 frame·s–1. 该模型不仅摆脱了现有模型对于图像预处理的依赖, 还能够适用于真实观测下图像序列不等长以及暴时序列与非暴时序列样本数量极端不均衡的情况, 具有较高的实用性.Abstract: Auroral substorm is a geomagnetic disturbance resulting from the interaction between Earth’s magnetic field and the solar wind. The accurate identification of the onset times is crucial for a deep understanding of the underlying physical mechanisms. The existing machine methods for auroral substorm identification differ from manual identification standards and typically require complex image preprocessing and parameter tuning by manual. To achieve a machine model consistent with manual identification standards, this paper designs two identification strategies aimed at addressing the issue of variable image sequence lengths encountered in replicating manual standards. Based on deep learning methods, this paper proposes an EfficientNet model featuring CBAM attention as a key component for model construction. The model is trained using ultraviolet auroral images from the Polar satellite between 1996 and 1998 and tested on image data from 1999 to 2000. The model achieves an identification accuracy of up to 0.98 and an efficiency of 36.93 frames per second. This model not only eliminates the reliance on image preprocessing present in existing models but also adapts to real-world observations with unequal image sequence lengths and extreme imbalances in the number of samples between substorm and non-substorm sequences, demonstrating its high practicality.
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Key words:
- Auroral substorm /
- Onset time /
- Machine identification /
- Deep learning
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表 1 两组数据集的序列与图像数量
Table 1. Number of sequences and images in two datasets
训练集1 测试集1 训练集2 测试集2 暴时序列数量 1367 615 1367 615 非暴时序列数量 3740 1772 72028 37666 暴时图像数量 7382 8545 7382 8545 非暴时图像数量 17926 23712 337442 447926 表 2 CBAM-EfficientNet组成架构
Table 2. Architecture of CBAM-EfficientNet
阶段 模块 卷积核大小 通道数 步长 模块数量 1 Conv2d-BN-Swish 3×3 32 2 1 2 CBAM 7×7 32 1 1 3 CBAM-MB 3×3 16 1 1 4 CBAM-MB 3×3 24 2 2 5 CBAM-MB 5×5 40 2 2 6 CBAM-MB 3×3 80 2 3 7 CBAM-MB 5×5 112 1 4 8 CBAM-MB 5×5 192 2 5 9 CBAM-MB 3×3 320 1 1 10 Conv2d-BN-Swish 1×1 1280 1 1 11 Global Average Pooling - - - 1 表 3 以不同网络结构为主干网络的模型在测试集上的识别准确性评估结果
Table 3. Identification accuracy evaluation results of the models with different networks as backbone
模型 测试集1 测试集2 P R F1 P R F1 InceptionV3-CFS 0.98 0.90 0.94 0.96 0.87 0.91 ViT-CFS 0.98 0.93 0.96 0.93 0.88 0.90 CBAM-EfficientNet-CFS 0.99 0.91 0.95 0.98 0.87 0.92 InceptionV3-SMS 0.91 0.87 0.89 0.82 0.88 0.85 ViT-SMS 0.93 0.90 0.91 0.86 0.88 0.87 CBAM-EfficientNet-SMS 0.94 0.94 0.94 0.84 0.89 0.86 -
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