Ecliptic North-South Symmetry of Hydrogen Geocorona
Ecliptic North-South Symmetry of Hydrogen Geocorona
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氢地冕的黄道南北对称性
DOI：
10.1002/2017gl075915
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发表时间：
2017
影响因子：
5.2
通讯作者：
Fujimoto M.
中科院分区：
文献类型：
--
作者：
Kameda S.;Ikezawa S.;Sato M.;Kuwabara M.;Osada N.;Murakami G.;Yoshioka K.;Yoshikawa I.;Taguchi M.;Funase R.;Sugita S.;Miyoshi Y.;Fujimoto M.
氢外逸层构成了地球最上层的大气层，它的形状可能反映了大气逃逸过程的最后阶段。氢在外逸层的分布仍然无法观测到，因为从外逸层内部很难观测到外日冕辐射。在这项研究中，我们使用了位于外逸层外的近地天体近距离飞行与光学导航航天器上的莱曼阿尔法成像相机，获得了第一张延伸到超过38个地球半径的整个地球日冕的图像。观测到的发射强度分布可以用我们的分析模型再现，该模型有三个参数：外基温度、外基密度和太阳辐射压力，这意味着磁化等离子体层的热氢产生并不是形成外层氢外逸层的主要过程。然而，不能排除磁效应在确定总逸出通量中的作用。
The hydrogen exosphere constitutes the uppermost atmospheric layer of the Earth, and its shape may reflect the last stage of the atmospheric escape process. The distribution of hydrogen in the outer exosphere remains unobserved because outer geocoronal emissions are difficult to observe from within the exosphere. In this study, we used the Lyman Alpha Imaging Camera on board the Proximate Object Close Flyby with Optical Navigation spacecraft, located outside the exosphere, to obtain the first image of the entire geocorona that extends to more than 38 Earth radii. The observed emission intensity distribution can be reproduced using our analytical model that has three parameters: exobase temperature, exobase density, and solar radiation pressure, which implies that hot hydrogen production in the magnetized plasmasphere is not the dominant process shaping the outer hydrogen exosphere. However, the role of the magnetic effect in determining the total escape flux cannot be ruled out.