Precipitation of Energetic Neutral Atoms and Induced Non-Thermal Escape Fluxes from the Martian Atmosphere

Nicholas Lewkow, Vasili Kharchenko

(Submitted on 23 Apr 2014)

The precipitation of energetic neutral atoms (ENAs), produced through charge exchange (CX) collisions between solar wind (SW) ions and thermal atmospheric gases, is investigated. Subsequent induced non-thermal escape fluxes have been carried out for the Martian atmosphere. Detailed modeling of the ENA energy input and determination of connections between parameters of precipitating ENAs and resulting escape fluxes, reflection coefficients of fast atoms from the Mars atmosphere, and altitude dependent ENA energy distributions are established using Monte Carlo (MC) simulations of the precipitation process with accurate quantum mechanical (QM) cross sections.

Detailed descriptions of secondary hot (SH) atoms and molecules induced by ENAs have been obtained for a better understanding of the mechanisms responsible for atmospheric escape and evolution. The effects of using isotropic hard sphere (HS) cross sections as compared to realistic, anisotropic quantum cross sections are examined for energy-deposition profiles, intensities and energy distributions of atomic and molecular escape fluxes, and time dependent atmospheric heating. 3D MC simulations have been carried out using a step-by-step transport method to track large ensembles of ENAs in a time-dependent manner as they propagate into the Martian atmosphere and transfer their energy to the ambient atoms and molecules.

Altitude-dependent rates of atmospheric heating, thermalization depths, the altitude profiles of the production rates of SH atoms and molecules, and induced, non-thermal, escape fluxes have been determined. All MC results were obtained for both realistic, anisotropic cross sections and compared with a simplified model employing isotropic, HS cross sections.

Comments:

Submitted to the Astrophysical Journal

Subjects:

Earth and Planetary Astrophysics (astro-ph.EP)

Cite as:

arXiv:1404.5986 [astro-ph.EP] (or arXiv:1404.5986v1 [astro-ph.EP] for this version)

Submission history

From: Nicholas Lewkow 

[v1] Wed, 23 Apr 2014 21:14:34 GMT (163kb)

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