High‐latitude ground‐based observations of the thermospheric ion‐drag time constant
High‐latitude ground‐based observations of the thermospheric ion‐drag time constant
复制标题
热层离子拖曳时间常数的高纬度地面观测
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
K. Schlegel
中科院分区：
文献类型：
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作者：
M. Kosch;K. Cierpka;M. Rietveld;T. Hagfors;K. Schlegel
以往的研究已经确凿地证明，F区热层风遵循磁层对流的离子漂移模式，但通常滞后于磁层对流离子漂移模式。对离子-中性动量交换方程的分析表明，离子阻力和热压是F区中性动量强迫的主要贡献因素，科里奥利力、平流力和粘性力的影响相对较小。定义了一个离子-中性耦合时间常数(e-折叠时间)，它描述了在对流中发生阶跃变化后，中性气体速度接近离子速度所需的时间。在这项研究中，用EISCAT三站非相干散射装置和地基法布里-珀罗涉仪分别在斯堪的纳维亚半岛北部观测到F区离子漂移和中性风。电子折叠时间在0.5-6.5小时之间变化，地磁活跃期和平静期的平均时间分别为1.8小时和3.3小时，与以前卫星测量的0.5-3.5小时相比很好。
From previous studies, it has been conclusively demonstrated that F‐region thermospheric winds follow, but generally lag behind, the ion drift pattern of magnetospheric convection. Analysis of the ion‐neutral momentum exchange equation shows that ion‐drag and thermal pressure are the major contributors to neutral momentum forcing at F‐region heights with relatively minor effects from coriolis, advection and viscous forces. An ion‐neutral coupling time constant (e‐folding time) has been defined which describes the time taken for the neutral gas velocity to approach the ion velocity after a step change in convection. In this study, F‐region ion drift and neutral winds have been observed by the EISCAT tristatic incoherent scatter facility and a ground‐based Fabry‐Perot interferometer, respectively, from northern Scandinavia. The e‐folding time varies in the range 0.5–6.5 hours, with an average of 1.8 and 3.3 hours for a geomagnetically active and quiet period, respectively, which compares well with previous satellite measurements of 0.5–3.5 hours.