Characteristics of the Poynting flux and wave normal vectors of whistler-mode waves observed on THEMIS
Characteristics of the Poynting flux and wave normal vectors of whistler-mode waves observed on THEMIS
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DOI：
10.1002/jgra.50176
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发表时间：
2013-04-01
影响因子：
2.8
通讯作者：
LeContel, O.
中科院分区：
文献类型：
--
作者：
Li, Wen;Bortnik, J.;LeContel, O.
本文研究了等离子体层顶外哨声模波的坡印亭通量和波法矢在低频段（0.1- 0.5fce）和高频段（0.5- 0.8fce）的特性，其中fce是赤道电子回旋频率。为了分析波的特性，我们利用了2008年6月至2012年11月近赤道磁层中多个THEMIS航天器的高分辨率波形数据。波的电场和磁场的全部测量用于计算坡印亭通量和构造波的法向量，然后用于计算相对于背景磁场的极角和方位角。统计结果表明，大多数哨声波传播远离磁赤道，这表明，主要的源区是非常接近赤道。低频波法向角分布在靠近磁力线方向有一个主峰，在共振锥附近有一个次峰。相反，上频带波的波正态分布在0度和60度之间呈现出宽分布，其中在近似0度处的概率最大。波法向矢量的方位角分量主要指向径向向外的较低和较高的波段波，但方位角传播的趋势是观察到较低的波段波在白天和黄昏部门可能是由于明显的方位角密度梯度在下午的部门。我们的统计结果提供了重要的信息，坡印亭通量和哨声模式波的波法向量，这在辐射带电子动力学中起着重要的作用。
The characteristics of the Poynting flux and wave normal vectors of whistler-mode waves outside the plasmapause are investigated for the lower (0.1-0.5 fce) and upper bands (0.5-0.8 fce), where fce is the equatorial electron cyclotron frequency. To analyze the wave properties, we utilized high-resolution waveform data from multiple THEMIS spacecraft in the near-equatorial magnetosphere from June 2008 to November 2012. Full measurements of the wave electric and magnetic fields are used to calculate the Poynting fluxes and construct the wave normal vectors, which are then used to calculate the polar and azimuthal angles with respect to the background magnetic field. Statistical results show that the majority of whistler-mode waves propagate away from the magnetic equator, suggesting that the major source region is very close to the equator. The lower band wave normal angle distribution shows a major peak close to the field line direction and a secondary peak near the resonance cone. In contrast, the wave normal distribution of upper band waves exhibits a broad distribution between 0 degrees and 60 degrees with the largest probability at similar to 0 degrees. The azimuthal component of the wave normal vector predominantly points radially outward for both lower and upper band waves, but a tendency for azimuthal propagation is observed for lower band waves in the day and dusk sectors probably due to pronounced azimuthal density gradients in the afternoon sector. Our statistical results provide crucial information on the Poynting fluxes and wave normal vectors of whistler-mode waves, which play a significant role in radiation belt electron dynamics.