标题： 利用L5处的现场观测预测太阳活动极小期的Dst 显示英文标题

标题： Prediction of Dst during solar minimum using in situ measurements at L5

摘要： 由高速流引发的地磁风暴由于太阳风与地磁场之间复杂的相互作用，可能对现代基础设施产生显著的负面影响。 衡量这种影响程度的一个指标是京都 $Dst$ 指数。 我们提出了一种方法，利用拉格朗日点5（L5）处测量的数据预测 $Dst$，这使得我们可以提前4.5天预报太阳风的发展。 以STEREO-B卫星作为替代物，我们将L5附近的测量数据映射到近地环境，并使用基于机器学习改进的Temerin-Li $Dst$ 模型预测该点的 $Dst$。 我们采用传统的逐点误差度量以及基于事件的验证方法评估该方法的准确性。 结果显示，使用L5数据的预测在所有验证指标上都优于27天太阳风持久性模型，但未能达到L1监测器的水平。 与 $B_x$ 和 $B_y$ 相比，时间偏差和 $B_z$ 的快速变化发展降低了准确性。 L5预测的$Dst$的 RMSE 为$9$纳特，这是近地测量误差$4$纳特的两倍。 L5 测量最有用的应用体现在对未来四天的最小值$Dst$进行预测。 该方法正在使用 STEREO-A 作为 L5 代理实现实时预报，并对未来 L5 任务的实用性具有影响。 显示英文摘要

摘要： Geomagnetic storms resulting from high-speed streams can have significant negative impacts on modern infrastructure due to complex interactions between the solar wind and geomagnetic field. One measure of the extent of this effect is the Kyoto $Dst$ index. We present a method to predict $Dst$ from data measured at the Lagrange 5 (L5) point, which allows for forecasts of solar wind development 4.5 days in advance of the stream reaching the Earth. Using the STEREO-B satellite as a proxy, we map data measured near L5 to the near-Earth environment and make a prediction of the $Dst$ from this point using the Temerin-Li $Dst$ model enhanced from the original using a machine learning approach. We evaluate the method accuracy with both traditional point-to-point error measures and an event-based validation approach. The results show that predictions using L5 data outperform a 27-day solar wind persistence model in all validation measures but do not achieve a level similar to an L1 monitor. Offsets in timing and the rapidly-changing development of $B_z$ in comparison to $B_x$ and $B_y$ reduce the accuracy. Predictions of $Dst$ from L5 have an RMSE of $9$ nT, which is double the error of $4$ nT using measurements conducted near the Earth. The most useful application of L5 measurements is shown to be in predicting the minimum $Dst$ for the next four days. This method is being implemented in a real-time forecast setting using STEREO-A as an L5 proxy, and has implications for the usefulness of future L5 missions.