CEDAR: Physics of the Hydrogen Geocorona

在威斯康星州麦迪逊附近的Pine Bluff天文台和新墨西哥州的Kitt Peak使用法布里-珀罗涉仪继续对地冕巴尔默-阿尔法辐射进行长期测量。由于低噪声图像平面探测，仪器具有前所未有的灵敏度，这使得这些地冕测量可以扩展到包括亚瑞利巴尔默-贝塔发射的测量。由于来自同一来源的这两种辐射的光学输运性质不同，因此有可能从几千公里的高层热层提取准确的氢原子密度分布的值。H原子是上层电离层的中性源，可以利用电荷交换平衡来确定高层热层中氧原子的密度。一旦确定，H原子的高度分布就被用来确定H的垂直通量。长期数据库还被用来确定外圈H的太阳周期变化，并探索与全大气含氢物种丰度的变化有关的长期变化的可能性，这种变化可能随着低层大气中甲烷沉积的变化而变化。在派恩布拉夫的高光谱分辨率测量也被用来量化外基附近和之上的有效温度，并量化对巴尔默谱线轮廓的原子级联贡献。

Long-term measurements of the geocoronal Balmer-alpha emission are continued at the Pine Bluff Observatory near Madison, WI, and at Kitt Peak, NM using Fabry-Perot interferometers. Unprecedented instrument sensitivity due to low-noise image plane detection allows these geocoronal measurements to be extended to include measurements of the sub-Rayleigh Balmer-beta emission. Due to the dissimilar optical transport properties of these two emissions from the same source, it is possible to extract accurate values of atomic hydrogen (H) density profiles from the upper thermosphere to several thousand kilometers. That atomic H is the neutral source of the topside ionosphere, and can be used by virtue of charge exchange equilibrium to determine the density of atomic oxygen (O) in the upper thermosphere. Once determined, the atomic H altitude profiles are used to determine the vertical flux of H. The long term data base is also used to determine the solar cycle variability of exospheric H, and to explore the possibility of secular variability that relates to changes in whole-atmosphere hydrogenous species abundance that may be changing in concert with methane deposition in the lower atmosphere. High spectral resolution measurements at Pine Bluff are also used to quantify effective temperature near and above the exobase, and to quantify atomic cascade contributions to the Balmer line profiles.