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Communication Dans Un Congrès Année : 2022

Modeling of diffuse auroral emission on Mars: Contribution of MeV protons

Résumé

Recently, a new type of the Martian aurora, diffuse aurora, has been discovered by simultaneous observations with the Solar Energetic Particle (SEP) and the imaging ultraviolet spectrograph (IUVS) instruments on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft [Schneider et al., 2015]. Diffuse aurora is characterized by the brightening across the nightside of Mars due to the interaction of solar energetic particles (SEPs) with the Martian atmosphere [Schneider et al., 2015, 2018]. It is unclear whether the diffuse aurora originates from precipitating electrons or protons, and previous numerical models were not able to reproduce the observed emission profiles [Schneider et al., 2015; Gérard et al., 2017; Haider and Masoom, 2019]. This study aims to model the diffuse auroral emission during SEP events by both electrons and protons to explain the observed emission profiles. We have developed a Monte Carlo model, Particle TRansport In Planetary atmospheres (PTRIP), to calculate the limb intensity profile of the CO _{2} + ultraviolet doublet (UVD) due to precipitation of energetic electrons and protons with energy ranges from 100 eV to 100 keV and from 100 eV to 5 MeV, respectively. We used electron and proton fluxes observed by MAVEN during the December 2014 SEP event and the September 2017 SEP event. Our results showed that proton-induced CO _{2} + UVD emission is brighter and narrower with respect to the altitude profile and has a lower peak altitude than electron-induced CO _{2} + UVD emission. The calculated peak altitudes of the CO _{2} + UVD limb profiles are 76 km and 56 km in the SEP events that occurred during December 2014 and September 2017, respectively, which are in good agreement with the IUVS observations. We have succeeded in reproducing the peak altitudes and shapes of the observed CO2+ UVD limb profiles using the SEP fluxes observed by MAVEN. This was possible by taking into account the contribution of protons with energy up to MeV, indicating that both energetic electrons and protons contribute to producing the observed MAVEN/IUVS diffuse aurora.
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Dates et versions

insu-04469621 , version 1 (20-02-2024)

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Yuki Nakamura, Naoki Terada, François Leblanc, Ali Rahmati, Hiromu Nakagawa, et al.. Modeling of diffuse auroral emission on Mars: Contribution of MeV protons. 44th COSPAR Scientific Assembly, Jul 2022, Online, Unknown Region. pp.Abstract C3.2-0010-22. ⟨insu-04469621⟩
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