Atmospheric Loss of Atomic Oxygen during Proton Aurorae on Mars

V I Shematovich

doi:10.1134/s0038094621040079

V I Shematovich

Open Access

https://doi.org/10.1134/s0038094621040079

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Abstract

—For the first time, the calculations of the penetration of protons of the undisturbed solar wind into the daytime atmosphere of Mars due to charge exchange in the extended hydrogen corona (Shematovich et al., 2021) are used allowing us to determine self-consistently the sources of suprathermal oxygen atoms, as well as their kinetics and transport. An additional source of hot oxygen atoms—collisions accompanied by the momentum and energy transfer from the flux of precipitating high-energy hydrogen atoms to atomic oxygen in the upper atmosphere of Mars—was included in the Boltzmann kinetic equation, which was solved with the Monte-Carlo kinetic model. As a result, the population of the hot oxygen corona of Mars has been estimated; and it has been shown that the proton aurorae are accompanied by the atmospheric loss of atomic oxygen, which is evaluated within a range of (3.5–5.8) × 107 cm–2 s–1. It has been shown that the exosphere becomes populated with a substantial amount of suprathermal oxygen atoms with kinetic energies up to the escape energy, 2 eV. The atomic oxygen loss rate caused by a sporadic source in the Martian atmosphere—the precipitation of energetic neutral atoms of hydrogen (H‑ENAs) during proton aurorae at Mars—was estimated by the self-consistent calculations according to a set of the Monte-Carlo kinetic models. These values turned out be comparable to the atomic oxygen loss supported by a regular source—the exothermic photochemical reactions (Groeller et al., 2014; Jakosky et al., 2018). It is currently supposed that the atmospheric loss of Mars due to the impact of the solar wind plasma and, in particular, the fluxes of precipitating high-energy protons and hydrogen atoms during solar flares and coronal mass ejections may play an important role in the loss of the neutral atmosphere on astronomic time scales (Jakosky et al., 2018).

Highlights

The Sun influences the upper layers of the Martian atmosphere through both the radiation absorbed in the soft X-ray and extreme UV ranges and the solar wind plasma forcing, which results in the formation of the extended neutral corona populated by suprathermal Н, С, N, and О atoms
We considered the processes of formation, kinetics, and transport of suprathermal oxygen atoms in the thermosphere-to-exosphere transition region during proton aurorae in the illuminated atmosphere of Mars, which are induced by precipitation of energetic hydrogen atoms
The population of the hot oxygen corona of Mars was estimated; and we showed that the proton aurorae are accompanied by the atmospheric losses of atomic oxygen ranging within (3.5–5.8) × 107 cm–2 s–1

Summary

Introduction

The Sun influences the upper layers of the Martian atmosphere through both the radiation absorbed in the soft X-ray and extreme UV ranges and the solar wind plasma forcing, which results in the formation of the extended neutral corona populated by suprathermal (hot) Н, С, N, and О atoms (see, e.g., Groeller et al, 2014). Since the proton auroral events are observed on the dayside of Mars (Hughes et al, 2019) and induced by the fluxes of high-energy hydrogen atoms penetrating into the atmosphere (Deighan et al, 2018), to calculate the source function of suprathermal oxygen atoms, we use the Monte-Carlo kinetic models (Shematovich et al, 2019) developed before.

Results

Conclusion