Heliopause imaging in EUV: Oxygen O + ion 83.4-nm resonance line emission
Heliopause imaging in EUV: Oxygen O + ion 83.4-nm resonance line emission
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EUV 日光层顶成像：氧 O 离子 83.4 nm 共振线发射
DOI：
10.1029/1999ja000345
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发表时间：
2000
影响因子：
--
通讯作者：
H. Fahr
中科院分区：
文献类型：
--
作者：
M. Gruntman;H. Fahr
我们探索由地冕外的观察者从 1 个天文单位远程研究日球层顶的可能性。我们认为日球层顶是分隔太阳风和当地星际介质（LISM）的星系等离子体的边界，可以通过检测星际离子反射的太阳极紫外（EUV）辐射来成像。这种 EUV 成像将绘制日球层顶的地图，并提供对其三维结构和 LISM 参数的重要见解。我们考虑氧 O+ 离子共振线 (83.4 nm) 中的日球层顶映射；未来的文章将考虑氦 He+ 离子线 (30.4 nm) 成像。我们表明，83.4 nm 处的预期日球层顶亮度图与太阳风 O+ 拾取离子的前景辉光有本质上的不同。星际等离子体辉光在上风（相对于星际风）方向更亮，而拾取离子辉光在顺风方向占主导地位。 LISM 等离子体和拾取离子散射的辐射的光谱特性明显不同。 83.4 nm 的全天空图像对 LISM 的电离态高度敏感，可以让人们探测星际磁场的不对称性。我们简要讨论了日光层顶 EUV 测绘的实验要求，这需要将仪器灵敏度提高 3 个数量级。这是一项具有挑战性但并非不可能的任务。
We explore the possibility of remote, from 1 AU, study of the heliopause by an observer outside the geocorona. We argue that the heliopause, a boundary that separates the solar wind and the galactic plasma of the local interstellar medium (LISM), can be imaged by detecting solar extreme ultraviolet (EUV) radiation reflected by interstellar ions. Such EUV imaging would map the heliopause and provide important insight into its three-dimensional structure and the LISM parameters as well. We consider heliopause mapping in the oxygen O+ ion resonance line (83.4 nm); imaging in the helium He+ ion line (30.4 nm) will be considered in a future article. We show that the expected heliopause brightness map at 83.4 nm is essentially different from that of the foreground glow of the solar wind O+ pickup ions. The interstellar plasma glow is brighter in the upwind (with respect to the interstellar wind) direction, while the pickup ion glow dominates in the downwind direction. The spectral characteristics of the radiation scattered by the LISM plasma and by the pickup ions are significantly different. The all-sky images at 83.4 nm are highly sensitive to the ionization state of the LISM and would allow one to probe the asymmetry of the interstellar magnetic field. We briefly discuss the experimental requirements to heliopause EUV mapping, which would require 3 orders of magnitude improvement in instrumentation sensitivity. This is a challenging but not impossible task.