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MAVEN Observations of H- Ions in the Martian Atmosphere
  • +2
  • Nicholas Jones,
  • Jasper S. Halekas,
  • Zachary Girazian,
  • David L. Mitchell,
  • Christian Mazelle
Nicholas Jones
University of Iowa

Corresponding Author:nicholas-a-jones@uiowa.edu

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Jasper S. Halekas
University of Iowa
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Zachary Girazian
The University of Iowa
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David L. Mitchell
University of California, Berkeley
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Christian Mazelle
Institut de Recherche en Astrophysique et Planetologie
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At Mars, charge exchange between solar wind protons and neutral exospheric hydrogen produces energetic neutral atoms (ENAs) that can penetrate into the collisional atmosphere, where they can be converted through collisions into H+ and H. The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observed a population of negatively charged particles at low altitudes, whose energies, angular distribution, and dependence on the upstream solar wind were consistent with Horiginating in the solar wind. The highest fluxes of H were observed near perihelion and the southern summer solstice. We calculated an average ratio of ~4% between H density and H+ density, implying a slightly smaller relative abundance than reported previously (~10%). We found that the fraction of H ENAs converted to H increases with the solar wind energy, in agreement with laboratory measurements of the H–CO2 electron capture cross section.