Direct measurements of the Poynting flux associated with convection electric fields in the magnetosphere
Direct measurements of the Poynting flux associated with convection electric fields in the magnetosphere
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DOI：
10.1029/2010ja015491
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发表时间：
2010-12
影响因子：
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通讯作者：
Y. Nishimura;T. Kikuchi;A. Shinbori;J. Wygant;Y. Tsuji;T. Hori;T. Ono;S. Fujita;Takashi Tanaka
中科院分区：
文献类型：
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作者：
Y. Nishimura;T. Kikuchi;A. Shinbori;J. Wygant;Y. Tsuji;T. Hori;T. Ono;S. Fujita;Takashi Tanaka
[1]对流电场是磁层-电离层耦合系统中最基本的参数之一，对流电场的变化是太阳风向磁层电磁能量输运的结果，对流电场的观测对理解这一过程至关重要。我们提出的集群多航天器观测坡印廷通量与突然的变化，在大规模的电场突然开始和南转向行星际磁场（IMF）。星团探测器探测到坡印廷通量占主导地位的领域对齐向上的分量在初步的冲动突然开始，并在初期向南转向的IMF。向上的坡印亭通量表明存在阿尔芬波从电离层向磁层传输电磁能量，导致磁层对流变化。波导模型和全球磁流体动力学（MHD）模拟计算的坡印廷通量的演变后，太阳风压力的增强也显示向上坡印廷通量从电离层向磁层传播的速度比传播的压缩波。我们的结论是，电离层作为一个通道，传输电磁能量作为场向电流提供了一个广泛的区域在磁层电离层系统瞬间，导致磁层对流电场的变化。
[1] Observations of Poynting fluxes associated with onset of convection electric fields are essential for understanding of electromagnetic energy transport from the solar wind toward the magnetosphere leading to changes in the convection electric field, which is one of the most fundamental parameters in the magnetosphere-ionosphere coupled system. We present Cluster multispacecraft observations of Poynting fluxes associated with abrupt changes in large-scale electric fields during sudden commencements and southward turning of the interplanetary magnetic field (IMF). The Cluster spacecraft detected Poynting fluxes dominated by the field-aligned upward component during the preliminary impulse of sudden commencements and in the initial period after southward turning of the IMF. The upward Poynting flux indicates existence of Alfven waves transporting electromagnetic energy from the ionosphere toward the magnetosphere leading to magnetospheric convection changes. The waveguide model and global magnetohydrodynamic (MHD) simulation calculating evolution of the Poynting flux following solar wind pressure enhancements also show upward Poynting fluxes propagating from the ionosphere toward the magnetosphere faster than the propagation of compressional waves. We conclude that the ionosphere acts as a channel to transmit electromagnetic energy supplied as field-aligned currents toward a wide region in the magnetosphere-ionosphere system instantaneously, leading to changes in magnetospheric convection electric fields.