Transverse‐scale size of Pc3 ULF waves near the exterior cusp
Transverse‐scale size of Pc3 ULF waves near the exterior cusp
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DOI：
10.1029/2008ja013971
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发表时间：
2009-08
影响因子：
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通讯作者：
Y. Liu;B. Fraser;S. Ables;Beichen Zhang;Rui-yuan Liu;M. Dunlop;J. Waterman
中科院分区：
文献类型：
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作者：
Y. Liu;B. Fraser;S. Ables;Beichen Zhang;Rui-yuan Liu;M. Dunlop;J. Waterman
[1] 地磁场线的概念已广泛应用于磁层物理现象的研究中。例如，ULF波传播的模式与场的方向有关，阿尔文波模式沿着场方向传播。关于传播波的垂直范围知之甚少。本文利用波相干方法分析了 Pc3 频段的 ULF 波，这些波是由靠近外尖点的集群卫星和靠近尖点足迹的当地磁正午地面站同时观测到的。结果表明，地面观测到的H分量波的相干性远大于D分量，这与空间Cluster观测到的情况相反。地面H分量和空间y分量之间的相干性高于其他对组合，其中卫星和丹堡（DNB）站之间的相干性具有最大值。这些结果表明，波的偏振在传播通过电离层后旋转了90°，此时Cluster的磁足迹最接近DNB站。卫星之间 Pc3 波的相干性与卫星对相对于地磁场方向的排列高度相关。这种排列可以提供约 900 km 处外部尖点附近的地磁 Pc3 ULF 波的横向尺度尺寸，相干性为 0.65。
[1] The concept of a geomagnetic field line has been widely used in the study of magnetospheric physical phenomena. For example, the mode in which ULF waves propagate relates to the direction of the field, with the Alfven wave mode propagating along the field direction. Very little is known about the perpendicular extent of the propagating wave. In this paper, wave coherency methods are utilized to analyze ULF waves in the Pc3 band that were simultaneously observed by the Cluster satellites near the exterior cusp and by ground stations at local magnetic noon near the footprint of the cusp. The results show that the coherency of waves observed at the ground on the H component is much larger than that on the D component, which is opposite to that seen by Cluster in space. The coherency between the H component on the ground and the y component in space was higher than the other combination of pairs, with the coherency between the satellite and the Daneborg (DNB) station having the maximum value. These results suggest that the polarization of the waves are rotated by 90° after propagating through the ionosphere, and the magnetic footprint of Cluster is closest to the DNB station at this time. The coherency of the Pc3 waves between the satellites is highly related to the alignment of satellite pairs with respect to the geomagnetic field direction. This alignment may provide a transverse-scale size of the geomagnetic Pc3 ULF waves near the exterior cusp at ∼900 km with a coherency of 0.65.