Electron acceleration signatures in the magnetotail associated with substorms
Electron acceleration signatures in the magnetotail associated with substorms
复制标题
DOI：
10.1029/2009ja014587
复制
发表时间：
2010-05
影响因子：
--
通讯作者：
Y. Asano;I. Shinohara;A. Retinò;P. Daly;E. Kronberg;T. Takada;R. Nakamura;Y. Khotyaintsev;
中科院分区：
文献类型：
--
作者：
Y. Asano;I. Shinohara;A. Retinò;P. Daly;E. Kronberg;T. Takada;R. Nakamura;Y. Khotyaintsev;
[1]我们目前的集群多卫星观测加速电子在近地磁尾与亚暴。我们发现，最硬的电子能谱出现在亚暴膨胀的最早阶段，在近地尾区，他们逐渐变软的事件。高能电子通量的增强通常与离子（快流）和电子的体加速相关联地发生。它还表明，高能电子有时会表现出优先的垂直加速与磁场的正常分量的时间增强，然后各向异性的分布很快变成各向同性。在偶极期间，没有观察到对流信号，垂直通量下降到小于初始值，平行通量大于垂直通量。结果表明，电子加速机制与绝热电子感应加速器加速机制基本一致，而费米加速机制在高能部分不明显。俯仰角散射的影响也很重要。高能量电子通量的色散特征表明快速的朝晨漂移损耗，即有限等离子体加速区域的三维效应。
[1] We present Cluster multisatellite observations of accelerated electrons in the near-Earth magnetotail associated with substorms. We found that the hardest electron energy spectra appear in the earliest stage of substorm expansion in the near-Earth tail region and that they gradually become softer during the events. Enhancement of the high-energy electron flux occurs generally associated with the bulk acceleration of ions (fast flow) and electrons. It is also shown that the high-energy electrons sometimes show preferential perpendicular acceleration associated with the temporal enhancement of the normal component of the magnetic field, and then the anisotropic distribution quickly becomes isotropic. During the dipolarization interval, in which no convection signature is observed, perpendicular flux drops to less than the initial value, and the parallel flux is more than the perpendicular flux. The results suggest that the electron acceleration mechanism is mostly consistent with adiabatic betatron acceleration, while Fermi acceleration is not clear in the high-energy part. The effect of the pitch angle scattering is also important. The dispersive signature of the high-energy electron flux indicates fast dawnward drift loss, namely, the three-dimensional effect of the limited plasma acceleration region.