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Transverse-scale size of Pc3 ULF waves near the exterior cusp

【标题】Transverse-scale size of Pc3 ULF waves near the exterior cusp

【Title】Transverse-scale size of Pc3 ULF waves near the exterior cusp

【DOI】10.1029/2008JA013971

【作者】 刘勇华; B. J. Fraser; S. T. Ables; 张北辰; 刘瑞源; M. W. Dunlop; J. Waterman

【Author】 Liu Yonghua ; B. J. Fraser ; S. T. Ables ; Zhang Beichen ; Liu Ruiyuan ; M. W. Dunlop ; J. Waterman

【期刊】遥感技术与应用

【Journal】Journal of Geophysical Research: Space Physics

【期刊年份】2009

【卷】114

【期】

【关键词】

【Keywords】 Pc3 waves; coherence; conjugate; exterior cusp

【摘要】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 they 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.

【Abstract】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 they 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.

【基金/项目】 高纬pc5脉动共轭研究 ; 极区磁层与电离层耦合的动力学过程 ; 极区能量沉积过程及其对120E子午面电离层影响的研究

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