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      Non-thermal hydrogen atoms in the terrestrial upper thermosphere

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      Nature Communications
      Nature Publishing Group

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          Abstract

          Model predictions of the distribution and dynamical transport of hydrogen atoms in the terrestrial atmosphere have long-standing discrepancies with ultraviolet remote sensing measurements, indicating likely deficiencies in conventional theories regarding this crucial atmospheric constituent. Here we report the existence of non-thermal hydrogen atoms that are much hotter than the ambient oxygen atoms in the upper thermosphere. Analysis of satellite measurements indicates that the upper thermospheric hydrogen temperature, more precisely the mean kinetic energy of the atomic hydrogen population, increases significantly with declining solar activity, contrary to contemporary understanding of thermospheric behaviour. The existence of hot hydrogen atoms in the upper thermosphere, which is the key to reconciling model predictions and observations, is likely a consequence of low atomic oxygen density leading to incomplete collisional thermalization of the hydrogen population following its kinetic energization through interactions with hot atomic or ionized constituents in the ionosphere, plasmasphere or magnetosphere.

          Abstract

          Model predictions of atomic hydrogen behaviour in the terrestrial atmosphere have long-standing discrepancies with geocoronal observations. Here, using satellite measurements, Qin and Waldrop note the existence of hot hydrogen atoms in the upper thermosphere, reconciling observational modelling differences.

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          NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues

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            The terrestrial ring current: Origin, formation, and decay

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              Geocoronal imaging with Dynamics Explorer

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                Author and article information

                Journal
                Nat Commun
                Nat Commun
                Nature Communications
                Nature Publishing Group
                2041-1723
                06 December 2016
                2016
                : 7
                : 13655
                Affiliations
                [1 ]Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois, USA
                Author notes
                Article
                ncomms13655
                10.1038/ncomms13655
                5150641
                27922018
                15e414dc-0bee-4958-a04e-45d8cc3c4c6e
                Copyright © 2016, The Author(s)

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 10 June 2016
                : 20 October 2016
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