Field-aligned currents associated with Alfven waves in the poleward boundary region of the nightside auroral oval
Field-aligned currents associated with Alfven waves in the poleward boundary region of the nightside auroral oval
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DOI：
10.1029/96ja01797
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发表时间：
1996-10-01
影响因子：
2.8
通讯作者：
Matsuoka, A
中科院分区：
文献类型：
--
作者：
Nagatsuma, T;Fukunishi, H;Matsuoka, A
利用Akebono卫星提供的磁场、电场和粒子数据，研究了夜面非道德椭圆极向边界区域的场向电流特征。我们发现，大振幅，波浪状波动的磁场和电场经常发生在中高度局限在这个纬度狭窄的区域。我们研究了电场和磁场波动之间的关系，使用复阻抗函数进行了研究，复阻抗函数定义为（Z）/波浪线= mu（o）（E）/波浪线（x）/（B）/波浪线（y），其中（E）/波浪线（x）和（B）/波浪线（y）分别是电场的X分量和磁场的Y分量。最重要的结果是，在2 × 10 ~（-3）~ 8 × 10 ~（-2）Hz频率范围内，磁层-电离层耦合模型很好地解释了阻抗函数的特征。此外，对保持对准的坡印廷通量的计算表明，大部分阿尔芬波能量在电离层反射，而不是在电离层中耗散。这些事实表明，大多数的场向电流波动观察到在中等高度的向极边界区域的夜侧非道德椭圆是由于入射和反射阿尔芬波的叠加。推测PSBL中反射Alfven波的破碎可能导致等离子体片电子和离子的加热。
We have examined characteristics of the field-aligned currents in the poleward boundary region of the nightside amoral oval, using magnetic field, electric field, and particle data obtained from the Akebono satellite. We found that large-amplitude, wave-like fluctuations of magnetic and electric fields frequently occur at mid-altitudes confined in this latitudinally narrow region. We examined the relationship between electric and magnetic field fluctuations, examined using the complex impedance function defined as (Z) over tilde = mu(o) (E) over tilde(x)/(B) over tilde(y), where (E) over tilde(x) and (B) over tilde(y) are the X component of the electric field and the Y component of the magnetic field, respectively. The most important result obtained from this analysis is that the features of the impedance functions in the frequency range between 2 x 10(-3) and 8 x 10(-2) Hz are well explained by a time-dependent magnetosphere-ionosphere coupling model. Further, the calculation of the held-aligned Poynting flux showed that most of the Alfven wave energy is reflected at the ionosphere rather than dissipated in the ionosphere. These facts suggest that the majority of the field-aligned current fluctuations observed at mid-altitudes in the poleward boundary region of the nightside amoral oval are due to the superposition of incident and reflected Alfven waves. It is speculated that the breaking of reflected Alfven waves in the PSBL may cause the heating of plasma sheet electrons and ions.