Open AccessTailward flow of energetic neutral atoms observed at Mars
Author(s) -
Galli A.,
Wurz P.,
Kallio E.,
Ekenbäck A.,
Holmström M.,
Barabash S.,
Grigoriev A.,
Futaana Y.,
Fok M.C.,
Gunell H.
Publication year - 2008
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008je003139
Subject(s) - mars exploration program , solar wind , martian , atmosphere (unit) , energetic neutral atom , hydrogen , astrobiology , atmosphere of mars , exosphere , physics , plasma , computational physics , spectral line , magnetohydrodynamics , atmospheric sciences , atomic physics , environmental science , astronomy , ion , meteorology , nuclear physics , quantum mechanics
The ASPERA‐3 experiment on Mars Express provides the first measurements of energetic neutral atoms (ENAs) from Mars. These measurements are used to study the global structure of the interaction of the solar wind with the Martian atmosphere. In this study we describe the tailward ENA flow observed at the nightside of Mars. After characterizing energy spectra of hydrogen ENA signals, we present composite images of the ENA intensities and compare them to theoretical predictions (empirical and MHD models). We find that the tailward flow of hydrogen ENAs is mainly generated by shocked solar wind protons. Despite intensive search, no oxygen ENAs above the instrument threshold are detected. The results challenge existing plasma models and constrain the hydrogen exospheric densities and atmospheric hydrogen and oxygen loss rates at low solar activity.
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