Characterizing Precipitation Behaviors of H in the Martian Atmosphere

Author:

Henderson Sarah12ORCID,Halekas Jasper1ORCID,Jolitz Rebecca3,Mitchell David3,Mazelle Christian4ORCID,Eparvier Frank5,Elrod Meredith67ORCID

Affiliation:

1. The University of Iowa Iowa City IA USA

2. Montana State University Bozeman MT USA

3. Space Sciences Laboratory University of California Berkeley Berkeley CA USA

4. IRAP Université de Toulouse CNRS UPS CNES Toulouse France

5. Laboratory for Atmospheric and Space Physics University of Colorado Boulder CO USA

6. Planetary Environments Lab Goddard Space Flight Center NASA Greenbelt MD USA

7. CRESST II University of Maryland, College Park College Park MD USA

Abstract

AbstractSolar wind protons can charge exchange with the extensive hydrogen corona of Mars, resulting in a significant flux of energetic neutral atoms (ENAs). As these solar wind hydrogen ENAs precipitate into the upper atmosphere, they can experience electron attachment or detachment, resulting in populations of H and H+, respectively, with upstream velocity. We seek to characterize the behavior of H in the ionosphere of Mars through a combination of in situ data analysis and mathematical models. Observations indicate that measurable H precipitation in the ionosphere of Mars is rare, occurring during only 1.8% of available observations. These events occur primarily during high energy solar wind conditions near perihelion. We also compare H fluxes to those of H+ and find that H fluxes are ∼4.5 times less than H+, indicating preferential conversion of hydrogen ENAs to H+. We develop a simple model describing the evolution of the charged and neutral fraction of ENAs and H ions versus altitude. We find that 0.29%–0.78% of ENAs are converted to H for solar wind energies 1–3 keV. We also predict that the effects of photodetachment on the H‐H system are non‐negligible.

Publisher

American Geophysical Union (AGU)

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