Monte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements

Abstract

We present model results of the interaction of proton and hydrogen atom precipitation with the Martian atmosphere. We use a kinetic Monte Carlo model developed earlier for the analysis of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA‐3) Mars Express data. With the availability of Mars Atmosphere and Volatile Evolution Mission in situ measurements, not only the flux of protons incident on the atmosphere but also their degradation along the orbit may now be described. The comparison of the simulations with data collected with the Solar Wind Ion Analyzer shows that the Monte Carlo model reproduces some of the measured features. The results of comparison between simulations and measurements of the proton fluxes at low altitudes make it possible to infer the efficiency of charge exchange between solar wind and the extended hydrogen corona if the value of the magnetic field is measured simultaneously. We also find that the induced magnetic field plays a very important role in the formation of the backscattered flux and strongly controls its magnitude. At the same time, discrepancies between the modeled and the measured energy spectra of the backscattered protons are pointed out. We suggest that some of the physical processes controlling the upward flux are not fully understood or that the data processing of the measured backscattered proton flux should be improved.

Lyman-α emission in the Martian proton aurora: Line profile and role of horizontal induced magnetic field

“…The proton and H-ENA energy distribution functions (EDF) for the cases illustrated in this study were calculated using the Monte Carlo model. The variation of these energy distribution functions with altitude for different values of the induced magnetic field was illustrated in Bisikalo et al (2018). For simplicity, we assume that the flux of protons and H atoms at the top of the model is isotropic.…”

“…It is also identical to that used in the recent JGR paper byBisikalo et al (2018) plotted in green in their Figs. 4, 5 and 6.…”

“…It was characterized by an energy spectrum with a main peak at ∼400 eV, a fast drop beyond 2 keV and a total precipitated energy flux of 0.15 mW m −2 . The corresponding proton and fast hydrogen velocity distributions calculated as a function of altitude were described by Bisikalo et al (2018). We then use the directional H (2p) velocity vector field as a function of altitude to determine their projection and integrate all contributions along any simulated line of sight.…”

“…Deighan et al (2018) observed a correlation between the presence of auroral Lyman-α and enhancements of the penetrating proton flux measured with the Solar Wind Ion Analyzer (SWIA) instrument on board MAVEN. These penetrating protons are the product of charge exchange of penetrating ENAs colliding with the constituents of the Martian thermosphere (Kallio et al, 1997;Kallio and Barabash, 2001;Bisikalo et al, 2018). They lose their energy by ionizing, dissociating and exciting the atmospheric constitutents (mostly CO 2 , O, CO and N 2 ), heating the ambient gas and radiating.…”

Precipitating Solar Wind Hydrogen at Mars: Improved Calculations of the Backscatter and Albedo With MAVEN Observations

“…These include transient space weather events, the bow shock standoff distance, and the seasonally varying exospheric hydrogen column density. Both crustal and induced magnetic fields are also expected to strongly affect the backscatter and albedo (Bisikalo et al., 2018; Kallio et al., 2006; Wang et al., 2014; Shematovich et al., 2011). Understanding the role of magnetic fields is an interesting avenue for future investigations.…”