A Robust, High-Speed Automated Detection Model for Lightning Whistler
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摘要: 张衡一号卫星在轨六年积累了海量的观测数据,从中检测所有的闪电哨声波事件(Lightning Whistler, LW)对于全面分析空间物理环境的变化规律具有非常重要的意义。然而,依靠当前主流的基于时频图像的LW检测技术完成上述任务需要约40年的时间。为了克服其推理速度慢的问题以满足实际工程需求,本研究首次从音频事件检测的角度,提出了一种高速的闪电哨声波检测模型(a novel neural network for detecting whistler at an extremely fast speed)-WhisNet,该模型将完成上述任务的时间成本从40年压缩到了54天。首先,以4秒时间滑动窗截取波形数据;然后提取其梅尔频谱音频特征;接着构建轻量的卷积循环神经网络(CRNN)进一步提取LW的音频事件特征;最后在输出层创建两个全连接网络,使其输出每个LW事件的起始时间和持续时长。为了评估模型的性能和计算速度,在2020年4月1日至10日感应磁力仪(SCM)的数据上开展实验,得到实验结果如下:WhisNet模型检测的性能与基于时频图像的方法的性能相当,但计算量与参数量明显下降了99%,计算速度显著提升了98%;进一步将该模型应用2020年5月的SCM数据,对其检测结果进行统计,并与2020年5月的WCLG (The WWLLN Global Lightning Climatology and timeseries)平均闪电密度趋势进行可视化对比发现:两者具有高度的一致性,也进一步证实了WhisNet模型在大规模卫星数据处理中的适用性和准确性。该方法对于充分挖掘其他海量的地球空间事件具有非常重要的参考意义。Abstract: The Zhangheng Satellite has accumulated a vast amount of observational data over its six years in orbit. Detecting all lightning whistler wave (LW) events from this dataset is crucial for comprehensively analyzing the variation patterns of the space physical environment. However, using the current mainstream LW detection technology, which is based on time-frequency spectrograms, it would take approximately 40 years to complete this task. To address the slow inference speed and meet practical engineering demands, this study proposes, for the first time, a high-speed detection model for lightning whistler waves from the perspective of audio event detection—WhisNet. This model reduces the time cost from 40 years to just 54 days. First, waveform data is segmented using a 4-second sliding window; then, Mel-spectrogram audio features are extracted. Next, a lightweight Convolutional Recurrent Neural Network (CRNN) is constructed to further extract the audio event features of LW. Finally, two fully connected networks are created at the output layer to predict the start time and duration of each LW event. To evaluate the model’s performance and computational speed, experiments were conducted on data from the SCM (Search Coil Magnetometer) between April 1 and April 10, 2020. The results show that the performance of the WhisNet model is comparable to that of time-frequency image-based methods, but with a 99% reduction in computational and parameter costs and a 98% increase in computational speed. The model was further applied to SCM data from May 2020, and the detection results were statistically analyzed and visually compared to the average lightning density trend from the WWLLN Global Lightning Climatology and timeseries (WCLG) for May 2020. The high consistency between the two further confirms the applicability and accuracy of the WhisNet model in processing large-scale satellite data. This method offers significant reference value for thoroughly exploring other large-scale geospace events.
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Key words:
- Lightning Whistler Wave /
- High-Speed Detection /
- Zhangheng-1 Satellite /
- CRNN
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