The equivalent source method of Spherical Elementary Current Systems (SECS) has contributed valuable results for spatial magnetic interpolation purposes where no observations are available, as well as for modeling equivalent currents both in the ionosphere and in the subsurface, thus providing a separation between external and internal sources. It has been successfully applied to numerous Space Weather (SW) events, whereas some advantages have been reported over other techniques such as Fourier or Spherical (Cap) Harmonic Analysis. Although different modalities of SECS exist (either 1‐D, 2‐D, or 3‐D) depending on the number of space dimensions involved, the method provides a sequence of instantaneous pictures of the source current. We present an extension of SECS consisting in the introduction of a temporal dependence in the formulation based on a cubic B‐splines expansion. The technique thus adds one dimension, becoming 4‐D in general (e.g., 3‐D + t), and its application is envisaged for, though not restricted to, the analysis of past events including heterogeneous geomagnetic data sets, such as those containing gaps, different sampling rates or diverse data sources. A synthetic model based on the SW Modeling Framework is used to show the efficacy of the extended scheme. We apply this method to characterize the current systems of past and significant SW events producing geomagnetically induced currents, which we exemplify with an outstanding geomagnetic sudden commencement occurred on 24 March 1991.

中文翻译：

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在SECS技术中包括时间维度

球面基本电流系统（SECS）的等效源方法为无观测可用的空间磁插值目的以及为电离层和地下的等效电流建模提供了有价值的结果，从而在外部和外部之间建立了隔离。内部来源。它已经成功地应用于许多太空天气（SW）事件，而与其他技术相比，例如傅立叶或球形（上限）谐波分析，已经报道了一些优势。尽管根据所涉及的空间尺寸的数量，存在不同的SECS方式（一维，二维或3-D），但该方法提供了一系列源电流的瞬时图像。我们介绍了SECS的扩展，包括在基于三次B样条展开的公式中引入时间依赖性。因此，该技术增加了一维，通常变为4维（例如3D + t），其应用被设想为（但不仅限于）对过去事件的分析，这些事件包括异构地磁数据集，例如那些包含间隙，不同采样率或不同数据源的地磁数据集。基于SW建模框架的综合模型用于显示扩展方案的功效。我们使用此方法来表征产生地磁感应电流的过去和重大西南向事件的当前系统，我们以1991年3月24日发生的杰出地磁突然开始为例。