Development and validation of inversion technique for substorm current wedge using ground magnetic field data
Development and validation of inversion technique for substorm current wedge using ground magnetic field data
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DOI：
10.1002/2013ja019185
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发表时间：
2014-03
期刊：
影响因子：
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通讯作者：
X. Chu;T. Hsu;R. McPherron;V. Angelopoulos;Z. Pu;James J. Weygand;K. Khurana;M. Connors;J. Kissinger;Hui Zhang;O. Amm
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文献类型：
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作者：
X. Chu;T. Hsu;R. McPherron;V. Angelopoulos;Z. Pu;James J. Weygand;K. Khurana;M. Connors;J. Kissinger;Hui Zhang;O. Amm
经典的亚暴电流楔形模型表示在亚暴期间测量到的地面和空间磁扰动。我们开发了一种反演技术，利用中纬度地区的磁场数据来计算确定电流系统强度和几何形状的参数。电流楔由四个部分组成：午夜后向下到电离层的片状场对齐电流，穿过极光凸起的向西电流，午夜前向西涌动的向上片状电流，以及赤道平面上的向东电流。该模型有五个参数，包括电流强度、位置和两个场对齐电流片的宽度。环电流的同时变化由对称环电流和由三个附加参数表征的部分环电流的叠加来表示。模型参数以中纬度地面磁力计为基础，利用实际磁力线并考虑地球感应，作为时间函数确定。该模型通过多种技术进行了验证。首先，该模型预测了观测值中80%以上的方差。电流楔流强度和环流强度与西向电喷流和环流指数的变化趋势一致。第三，西向电射流的强度与电流楔的强度非常吻合。最后，宇宙飞船对极光的观测与从模型推导出的演化相一致。该亚暴电流楔块模型为研究亚暴发展及其与空间现象的关系提供了有价值的工具。
The classic substorm current wedge model represents ground and space magnetic perturbations measured during substorms. We have developed an inversion technique to calculate parameters determining the intensity and geometry of the current system using magnetic field data at midlatitudes. The current wedge consists of four segments: a sheet‐like field‐aligned current downward to the ionosphere postmidnight, a westward current across the auroral bulge, an upward sheet‐like current from the westward surge premidnight, and an eastward current in the equatorial plane. The model has five parameters including the current strength, the locations, and breadths of the two field‐aligned current sheets. Simultaneous changes in the ring current are represented by the superposition of a symmetric ring current and a partial ring current characterized by three additional parameters. Parameters of the model are determined as a function of time based on midlatitude ground magnetometers, using realistic field lines and accounting for Earth's induction. The model is validated by a variety of techniques. First, the model predicts more than 80% of the variance in the observations. Second, the intensity of the current wedge and the ring current follows the same trends of the westward electrojet and the ring current indices. Third, the intensity of the westward electrojet agrees extremely well with the intensity of the current wedge. Finally, spacecraft observations of the aurora correspond with the evolution deduced from the model. This model of the substorm current wedge provides a valuable tool for the study of substorm development and its relation to phenomena in space.