Dst Index Prediction Method Based on LSTM Neural Network
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摘要: Dst指数是当前使用较广泛的用于反映磁暴过程的小时地磁指数, 对Dst指数的预报是现代空间天气学主要研究内容之一. 基于LSTM神经网络方法, 利用2008-2022年的太阳风参数和Dst指数建立Dst指数预报模型, 分别为使用全时域数据建模的LSTM模型和仅使用磁暴期间数据建模的Storm模型. 使用LSTM模型对2001-2002年间的Dst指数进行滚动预报, 预报结果显示该模型对提前1~6 h的Dst指数预报相关系数达到0.94以上, 均方根误差在11 nT以内. Storm模型能够较好地解决LSTM模型在磁暴(尤其是强磁暴, Dst< –100 nT)主相期间预报误差较大的问题, 对2001-2002年期间的23次强磁暴事件预报结果表明, Storm模型对磁暴期间提前6 h的预报结果相关系数较LSTM模型由0.902提升至0.948. 综合两个预报模型组成的LSTM-Storm模型对Dst指数的预报结果相关系数在0.95以上, 均方根误差在9 nT以内, 相比单LSTM模型的预报精度有显著提升.
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关键词:
- Dst指数预报 /
- LSTM神经网络 /
- 预报模型 /
- LSTM-Storm模型
Abstract: The Dst index is one of the widely used hourly geomagnetic indices to reflect geomagnetic storm processes, and forecasting the Dst index constitutes a primary concern in modern space weather studies. This study leverages Long Short-Term Memory (LSTM) neural network methodology alongside solar wind parameters and Dst index data spanning from 2008 to 2022 to construct a predictive model for the Dst index. Two models are established: the LSTM model, modeling the entire temporal domain, and the Storm model, modeling solely data from storm periods. Employing the LSTM model for rolling forecasts of Dst index during 2001 to 2002 yields a correlation coefficient exceeding 0.94 and a root mean square error within 11 nT for forecasts ranging from 1 to 6 hours in advance. The Storm model effectively addresses the issue of pronounced forecast errors during storm periods, particularly during the main phase of intense storms (Dst < –100 nT), showcasing improved forecast accuracy. Forecasting experiments conducted on 23 strong storm events occurring during 2001―2002 demonstrate an enhancement in the correlation coefficient for forecasts made 6 hours in advance during storm periods, increasing from 0.902 with the LSTM model to 0.948 with the Storm model. Integration of both forecasting models into the LSTM-Storm model yields correlation coefficients above 0.95 and root mean square errors within 9 nT for Dst index forecasts, presenting a marked improvement in forecasting accuracy compared to the standalone LSTM model.-
Key words:
- Dst index prediction /
- LSTM neural network /
- Forecasting model /
- LSTM-Storm model
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表 1 2001-2002年强磁暴事件参数
Table 1. Parameters of severe magnetic storm events in 2001-2002
Start date Start time (UT) End date End time (UT) Min. Dst /nT 2001-03-19 12:00 2001-03-22 15:00 –149 2001-03-31 00:00 2001-04-04 11:00 –387 2001-04-10 10:00 2001-04-14 10:00 –271 2001-04-18 01:00 2001-04-19 19:00 –114 2001-04-22 02:00 2001-04-24 17:00 –102 2001-08-17 07:00 2001-08-19 07:00 –105 2001-09-30 22:00 2001-10-06 16:00 –166 2001-10-19 11:00 2001-10-25 12:00 –187 2001-10-27 05:00 2001-10-31 16:00 –157 2001-10-31 17:00 2001-11-03 09:00 –106 2001-11-05 20:00 2001-11-12 11:00 –292 2001-11-22 19:00 2001-11-28 10:00 –221 2002-03-23 14:00 2002-03-25 05:00 –100 2002-04-17 09:00 2002-04-19 02:00 –127 2002-04-19 09:00 2002-04-26 06:00 –149 2002-05-11 12:00 2002-05-13 16:00 –110 2002-05-23 09:00 2002-05-26 07:00 –109 2002-08-01 23:00 2002-08-03 23:00 –102 2002-08-18 23:00 2002-08-22 22:00 –106 2002-09-04 01:00 2002-09-06 04:00 –109 2002-09-07 01:00 2002-09-14 08:00 –181 2002-09-30 09:00 2002-10-12 20:00 –176 2002-11-20 16:00 2002-11-26 22:00 –128 表 2 LSTM模型对2001-2002年Dst指数的预报结果
Table 2. Dst index prediction results of the LSTM model during 2001-2002
提前时间/h t+1 t+2 t+3 t+4 t+5 t+6 CC 0.971 0.968 0.962 0.955 0.947 0.940 RMSE/ nT 7.44 7.92 8.53 9.26 9.96 10.64 表 3 LSTM-Storm模型提前1~6 h预报结果与已有研究的比较
Table 3. Comparison of LSTM-Storm model forecast results 1~6 h in advance with past studies
提前时间/h LSTM-Storm Ref. [16] Ref. [17] Ref. [18] CC RMSE/nT CC RMSE/nT CC RMSE/nT CC RMSE/nT t+1 0.989 4.51 0.966 5.25 0.982 2.68 0.983 2.85 t+2 0.984 5.41 0.946 6.55 0.949 4.48 0.952 4.80 t+3 0.980 6.16 0.928 7.59 0.918 5.62 0.921 6.11 t+4 0.970 7.41 0.910 8.53 0.887 6.52 0.895 7.03 t+5 0.963 8.21 0.892 9.18 0.858 7.17 0.874 7.65 t+6 0.957 8.91 0.873 9.86 0.826 7.99 0.857 8.09 -
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