Reconstruction of two-dimensional magnetopause structures from Cluster observations: verification of method
Reconstruction of two-dimensional magnetopause structures from Cluster observations: verification of method
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DOI：
10.5194/angeo-22-1251-2004
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发表时间：
2004-04
影响因子：
1.9
通讯作者：
H. Hasegawa;B. Sonnerup;M. Dunlop;A. Balogh;S. Haaland;B. Klecker;G. Paschmann;B. Lavraud;I. Dandouras;H. Rème
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文献类型：
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作者：
H. Hasegawa;B. Sonnerup;M. Dunlop;A. Balogh;S. Haaland;B. Klecker;G. Paschmann;B. Lavraud;I. Dandouras;H. Rème
抽象的。利用最近发展起来的一种重建近似二维（λ/λ z λ 0）空间定常磁场结构的技术，对4个星团航天器在距地2000 km左右时，在磁层顶晨侧进行的两次穿越进行了研究。该方法包括求解磁流体静力结构的Grad-Shafranov方程，使用沿着单个航天器轨道测量的等离子体和磁场数据作为空间初始值。我们通过比较一个航天器产生的磁场图与其他航天器实际观察到的场矢量来评估这种基于单航天器的技术的有用性。对于一个最佳选择的不变（z）轴，从重建的地图和相应的测量分量预测的字段之间的相关性达到0.97以上。这一结果表明，重建技术可以很好地预测其他航天器位置的条件。最佳不变轴相对接近从测量磁场的最小方差分析计算的中间方差方向，并且通常相对于围绕最大方差方向的旋转被很好地确定，但是相对于围绕最小方差方向的旋转不太好地确定。在其中一次事件中，分别为间隔几十秒穿越磁层顶的两个航天器恢复的场图显示了配置上的巨大差异。通过比较这些磁场图，讨论了磁层顶结构的时间演化，如磁岛的形成、磁层顶结构的运动以及磁层顶电流层的增厚等。关键词。磁层物理学（磁层顶、尖点和边界层）.空间等离子体物理学（实验和数学技术、磁重联）
Abstract. A recently developed technique for reconstructing approximately two-dimensional (∂/∂z≈0), time-stationary magnetic field structures in space is applied to two magnetopause traversals on the dawnside flank by the four Cluster spacecraft, when the spacecraft separation was about 2000km. The method consists of solving the Grad-Shafranov equation for magnetohydrostatic structures, using plasma and magnetic field data measured along a single spacecraft trajectory as spatial initial values. We assess the usefulness of this single-spacecraft-based technique by comparing the magnetic field maps produced from one spacecraft with the field vectors that other spacecraft actually observed. For an optimally selected invariant (z)-axis, the correlation between the field components predicted from the reconstructed map and the corresponding measured components reaches more than 0.97. This result indicates that the reconstruction technique predicts conditions at the other spacecraft locations quite well. The optimal invariant axis is relatively close to the intermediate variance direction, computed from minimum variance analysis of the measured magnetic field, and is generally well determined with respect to rotations about the maximum variance direction but less well with respect to rotations about the minimum variance direction. In one of the events, field maps recovered individually for two of the spacecraft, which crossed the magnetopause with an interval of a few tens of seconds, show substantial differences in configuration. By comparing these field maps, time evolution of the magnetopause structures, such as the formation of magnetic islands, motion of the structures, and thickening of the magnetopause current layer, is discussed. Key words. Magnetospheric physics (Magnetopause, cusp, and boundary layers) – Space plasma physics (Experimental and mathematical techniques, Magnetic reconnection)