Deducing composition and incident electron spectra from ground-based auroral optical measurements: Theory and model results
Deducing composition and incident electron spectra from ground-based auroral optical measurements: Theory and model results
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DOI：
10.1029/ja094ia10p13527
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发表时间：
1989-10
影响因子：
--
通讯作者：
D. Strickland;R. Meier;J. Hecht;A. Christensen
中科院分区：
文献类型：
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作者：
D. Strickland;R. Meier;J. Hecht;A. Christensen
我们研究的问题，监测成分和行为的沉淀电子光谱在极光使用N2+ 4278 A（蓝色），O I 6300 A（红色），O I 7774 A（窄; e+O），和O I 7774 A（宽; e+O2）从地面观察。这些功能以及窄O I 8446 A和宽O I 8446 A的计算列发射率作为入射电子光谱的硬度和O和O2的浓度的函数。还提供了这些速率的选定比率，例如窄/宽（对于7774 A）和红/蓝。入射光谱的特征在于麦克斯韦能量分布的特征能量范围从0.1至8千电子伏。使用Jacchia（1977）模型对组成进行建模，其中将比例因子应用于O和O2数密度。O的比例因子范围为0.1至1，O2的比例因子为1和1.5。作为一个组，上述速率和比率在刚刚描述的参数范围内显示出相当大的变化，使得它们对于监测入射电子能量通量、其平均能量以及O和O2相对于N2的浓度具有吸引力。红线是上述组的一个关键特征，它对入射电子光谱的低能部分（亚千伏）敏感。由于这可以从一个极光到另一个具有相同近似平均能量的极光有很大的不同，它成为任何使用红线的算法中要考虑的附加参数。论文2（Meier等人，本期）将此问题作为红线详细调查的一部分进行讨论。在目前的文件中，一个特定的代表性的低能量的组成部分被认为是使红线计算。本文的最后一个主题是使用温度推导出的旋转线分布和原子线多普勒宽度的测量来推断沉淀电子的平均能量。计算出的有效温度与硬度的入射电子光谱的背景下，更精确的技术相关的旋转线分布和多普勒宽度的测量电子光谱硬度进行了讨论。
We examine the problem of monitoring composition and the behavior of precipitating electron spectra in auroras using N2+ 4278 A (blue), O I 6300 A (red), O I 7774 A (narrow; e+O), and O I 7774 A (broad; e+O2) as observed from the ground. Calculated column emission rates for these features as well as those of narrow O I 8446 A and broad O I 8446 A are presented as functions of the hardness of the incident electron spectrum and the concentrations of O and O2. Selected ratios of these rates such as narrow/broad (for 7774 A) and red/blue are also presented. Incident spectra are characterized by Maxwellian energy distributions with characteristic energies ranging from 0.1 to 8 keV. Composition is modeled using a Jacchia (1977) model where scaling factors are applied to the O and O2 number densities. Scaling factors for O range from 0.1 to 1, and factors of 1 and 1.5 are considered for O2. As a group, the above rates and ratios show considerable variation over the just described parameter ranges, making them attractive for monitoring incident electron energy flux, its mean energy, and the concentrations of O and O2 relative to N2. The red line is a key feature of the above group which is sensitive to the low-energy portion (subkilovolt) of the incident electron spectrum. Since this can vary considerably from one aurora to another having the same approximate mean energy, it becomes an added parameter to be considered within any algorithm using the red line. Paper 2 (Meier et al., this issue) discusses this problem as part of a detailed investigation of the red line. In the current paper, one particular representation of a low-energy component is considered for making the red line calculations. A final subject of this paper is the use of temperatures deduced from measurements of rotational line distributions and atomic line Doppler widths to infer mean energies of precipitating electrons. Calculated effective temperatures versus hardness of the incident electron spectrum are presented and discussed in the context of more precise techniques for relating measurements of rotational line distributions and Doppler widths to electron spectral hardness.