Optical estimation of auroral ion upflow: Theory
Optical estimation of auroral ion upflow: Theory
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极光离子上流的光学估计：理论
DOI：
10.1029/2007ja012691
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发表时间：
2007
影响因子：
--
通讯作者：
M. Díaz
中科院分区：
文献类型：
--
作者：
M. Zettergren;J. Semeter;P. Blelly;M. Díaz
这项工作提出了与极光离子上涌有关的光学发射的系统分析。利用流体动力学模型计算了单能入射电子束的光强和场向离子输运。动力学部分用多流方法模拟高能粒子输运，并为电离层的八矩流体模型提供电离、激发和加热速率，然后计算产生的离子上涌。该分析用于开发一种技术，用于估计从光度测量在五个离散波长：427.8 nm, 557.7 nm, 630.0 nm， 732 nm和844.6 nm向上离子通量。该过程包括：(1)通过反演磁天顶的多波长光学测量来估计入射粒子谱，(2)将该入射谱应用于流体动力学模型来估计向上流动响应。通过对已知电子谱计算的亮度进行反演，然后将从已知谱直接计算的上流与从估计谱计算的上流进行比较，证明了该方法的鲁棒性。发现反演提供了沉淀电子能谱和离子上涌的可靠估计，即使在亮度存在现实不确定性的情况下。该技术为研究磁层和电离层之间的质量耦合提供了一种新的工具。潜在的应用范围从上升流事件研究到通过融合来自多个传感器的光学数据来估计在亚风暴潮期间进入过渡区域的等离子体总量。
[1] This work presents a systematic analysis of optical emissions related to auroral ion upflow. Optical intensities and field-aligned ion transport are computed for a set of monoenergetic incident electron beams using a combined fluid-kinetic model. The kinetic portion models the energetic particle transport with a multiple stream approach and provides ionization, excitation, and heating rates to an eight-moment fluid model of the ionosphere, which then calculates the resulting ion upflow. The analysis is used to develop a technique for estimating upward ion flux from photometric measurements at five discrete wavelengths: 427.8 nm, 557.7 nm, 630.0 nm, 732 nm, and 844.6 nm. The procedure involves (1) estimating the incident particle spectrum by inversion of multiwavelength optical measurements in the magnetic zenith, (2) applying this incident spectrum to the fluid-kinetic model to estimate the upflow response. The robustness of the procedure is demonstrated by inverting brightnesses computed for a known electron spectrum and then comparing upflow directly calculated from the known spectrum to the upflow calculated from the estimated spectrum. The inversion is found to provide a reliable estimate of the precipitating electron spectrum and ion upflow, even in the presence of realistic uncertainties in brightness. The technique represents a new tool for studying mass coupling between the magnetosphere and ionosphere. Potential applications range from upflow event studies to estimating the total amount of plasma entering the transition region during a substorm surge via fusion of optical data from multiple sensors.