基于ConvLSTM的电离层行波扰动时空特征预报方法

A ConvLSTM-Based Approach for Spatiotemporal Prediction of Traveling Ionospheric Disturbances

  • 摘要: 电离层行波扰动(traveling ionospheric disturbances, TIDs)是电离层电子密度在跨圈层耦合作用下形成的波状扰动,其导致的总电子含量(total electron content, TEC)变化会影响全球导航卫星系统(GNSS)精密定位的稳定性与可靠性,因此TIDs的精确预警对于高精度GNSS定位具有重要意义。针对传统时序预报模型无法顾及TIDs的空间特征问题,提出了基于卷积长短期记忆网络(ConvLSTM)的TIDs时空特征的短临预报方法。利用日本上空的去趋势TEC图像数据集,系统评估了模型在不同太阳活动水平和不同纬度条件下的预报性能。结果表明,该模型的TIDs预报特征与真实特征在整体结构上具有较高一致性,其结构相似性可达0.72,均方根误差为0.19 TECu。TIDs预报精度随太阳活动的增强而下降,太阳活动低年(2020年)明显优于高年(2024年),在28°N-35°N与42°N-48°N的纬度带上的表现优于35°N-42°N区域。结果验证了ConvLSTM模型在中纬度地区TIDs短临预报中的有效性,可为北斗/GNSS电离层扰动预警及精密定位性能保障提供重要参考。

     

    Abstract: Objectives Traveling Ionospheric Disturbances (TIDs) are wave-like perturbations in ionospheric electron density induced by atmosphere-ionosphere coupling processes, and the associated variations in Total Electron Content (TEC) can significantly affect the stability and reliability of Global Navigation Satellite System (GNSS) high-precision positioning. Existing forecasting methods mainly focus on temporal variations and have limited capability in characterizing the spatial evolution of TIDs. To improve the short-term forecasting performance of ionospheric disturbances, a ConvLSTM-based deep learning framework is proposed for the spatiotemporal prediction of TIDs using sequences of detrended TEC (dTEC) maps over Japan under different solar activity conditions and latitude regions. Methods A short-term forecasting framework based on the Convolutional Long Short-Term Memory (ConvLSTM) network is constructed using an encoder-decoder architecture. By integrating convolutional operations into recurrent neural networks, temporal dependencies and spatial structures in sequential ionospheric maps are simultaneously captured. And the residual learning and skip-connection mechanisms are incorporated to enhance the reconstruction of fine-scale disturbance features. The experimental data are derived from real-time ionospheric maps provided by the National Institute of Information and Communications Technology (NICT) of Japan based on the dense GEONET GNSS network. After preprocessing, the dTEC maps are resized to 256 × 256 pixels. Data from 2020, 2022, and 2024 are processed to represent low, moderate, and high solar activity conditions, respectively. Furthermore, the study region is divided into three latitude bands to comprehensively evaluate the latitude-dependent forecasting performance using SSIM, PSNR, RMSE, and MAE. Results The experimental results show that the proposed framework achieves robust short-term forecasting performance for TIDs in the mid-latitude region. The predicted dTEC maps maintain high structural consistency with observations, with an average SSIM of 0.72 and an RMSE of approximately 0.19 TECu. In terms of solar activity dependence, the best forecasting performance is obtained during the low solar activity year (2020), while larger prediction errors occur during the high solar activity year (2024) due to intense background perturbations. For spatial distribution, the latitude-dependent analysis further indicates that the forecasting performance in the 28°-35°N and 42°-48°N latitude bands is superior to that in the 35°-42°N region. Conclusions The forecasting performance of the proposed ConvLSTM-based framework demonstrates strong adaptability under different solar activity conditions and latitude regions, and the method can effectively preserve the structural characteristics and spatial evolution information of TIDs. The final forecasting accuracy can meet the practical needs of ionospheric disturbance warning and high-precision BDS/GNSS positioning applications.

     

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