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- Title
Neutralized solar wind ahead of the Earth's magnetopause as contribution to non-thermal exospheric hydrogen.
- Authors
Fahr, Hans J.; Nass, Uwe; Dutta-Roy, Robindro; Zoennchen, Jochen H.
- Abstract
In a most recent paper by Qin andWaldrop (2016), it had been found that the scale height of hydrogen in the upper exosphere of the Earth, especially during solar minimum conditions, appears to be surprisingly large. This indicates that during minimum conditions when exobasic temperatures should be small, large exospheric H-scale heights predominate. They thus seem to indicate the presence of a non-thermal hydrogen component in the upper exosphere. In the following parts of the paper we shall investigate what fraction of such expected hot hydrogen atoms could have their origin from protons of the shocked solar wind ahead of the magnetopause converted into energetic neutral atoms (ENAs) via charge-exchange processes with normal atmospheric, i.e., exospheric hydrogen atoms that in the first step evaporate from the exobase into the magnetosheath plasma region. We shall show that, dependent on the sunward location of the magnetopause, the density of these types of nonthermal hydrogen atoms (H-ENAs) becomes progressively comparable with the density of exobasic hydrogen with increasing altitude. At low exobasic heights, however, their contribution is negligible. At the end of this paper, we finally study the question of whether the H-ENA population could even be understood as a self-consistency phenomenon of the H-ENA population, especially during solar activity minimum conditions, i.e., H-ENAs leaving the exosphere being replaced by H-ENAs injected into the exosphere.
- Subjects
SOLAR wind; MAGNETOPAUSE; HYDROGEN; EXOSPHERE; NON-thermal plasmas
- Publication
Annales Geophysicae (ANGEO) (09927689), 2018, Vol 36, Issue 2, p445
- ISSN
0992-7689
- Publication type
Article
- DOI
10.5194/angeo-36-445-2018