Large parallel electric fields in the upward current region of the aurora: Evidence for ambipolar effects
Large parallel electric fields in the upward current region of the aurora: Evidence for ambipolar effects
复制标题
极光向上电流区域的大平行电场：双极效应的证据
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
C. Chaston
中科院分区：
文献类型：
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作者：
A. Hull;J. Bonnell;F. Mozer;J. Scudder;C. Chaston
[1] 与磁场平行的电场在极光区的质量、动量和能量传输中发挥着重要作用。在本文中，我们探讨了稳态电子动量方程的哪些项与极光加速区上升流部分中 Polar 电场仪器测量的大振幅宏观平行电场（∼25 mV/m 至 300 mV/m）一致。通过对八个事件的详细分析，我们发现证据表明大振幅、宏观平行电场具有双极性特征；也就是说，它们受到界面上存在的电子压力梯度的支持，该界面将极光密度腔中相对冷、稠密的电离层等离子体与热、脆弱的磁层等离子体分开。这些结构似乎不能用纯粹传播的阿尔文波来解释。这些大振幅、宏观平行电场很可能是在分隔高密度和低密度等离子体的边界处形成的鞘场，类似于实验室实验装置中遇到的情况。
[1] Electric fields parallel to the magnetic field play a major role in the transport of mass, momentum, and energy in the auroral zone. In this paper we explore which terms of the steady state electron momentum equation are consistent with the large-amplitude, macroscopic parallel electric fields (∼25 mV/m to 300 mV/m) measured by the electric field instrument on Polar in the upward current part of the auroral acceleration region. From a detailed analysis of eight events we found evidence suggesting that the large-amplitude, macroscopic parallel electric fields are ambipolar in character; namely, they are supported by electron pressure gradients present at the interface separating the relatively cold, dense ionospheric plasma from the hot, tenuous magnetospheric plasma in the auroral density cavity. These structures do not appear to be explained by purely propagating Alfven waves. These large-amplitude, macroscopic parallel electric fields are likely to be a sheath field that forms at the boundary separating a high and low density plasma, similar to that encountered in laboratory experimental devices.