[P-CG19] Planetary Magnetosphere, Ionosphere, and Atmosphere

[PCG19-08] Three-dimensional simulation of the Martian diffuse auroral emission in the crustal magnetic field regions

*Yuki Nakamura^1,2,3, Francois Leblanc², Jean-Claude Gérard⁴, Lauriane Soret⁴, Naoki Terada¹, Hiromu Nakagawa¹, Shotaro Sakai^1,5, Kiyoka Murase^6,7, Ryuho Kataoka^6,7, Dave A Brain⁸, Kanako Seki³ (1.Department of Geophysics, Graduate School of Science, Tohoku University, 2.LATMOS, Sorbonne Université, 3.Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, 4.LPAP, STAR Institute, Université de Liège, 5.Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, 6.National Institute of Polar Research, 7.The Graduate University for Advanced Studies, SOKENDAI, 8.Laboratory for Atmospheric and Space Physics, University of Colorado Boulder)

Keywords:Mars, Diffuse aurora, Solar energetic particles

The recent discovery of the Martian diffuse aurora, which spans the whole nightside Mars due to the precipitation of solar energetic particles (SEPs), has highlighted that SEPs globally impacted the Martian atmosphere at low altitudes [Schneider et al., 2015, 2018]. Our recent Monte Carlo model, which is one dimension in space vertically without considering magnetic fields, has shown that both the SEP electrons and protons should have been at the origin of the Martian diffuse auroral emissions during the SEP events in December 2014 and September 2017 [Nakamura et a., 2022]. The spatial structure of the Martian diffuse auroral emission would provide insight into how SEPs precipitate into the Martian atmosphere through the magnetic field environment around Mars, however, it is still poorly understood due to the small number of observations.

In this study, we extend our Monte Carlo model to three dimensions with magnetic fields to investigate the effects of the crustal magnetic fields in the southern hemisphere of Mars on the spatial distribution of the Martian diffuse auroral emission. Our results show different morphology for the electron- and proton-induced emissions in the crustal magnetic field region due to the difference in their gyro radii. The electron-induced CO₂⁺ UVD emission is patchy and bright in the cusp regions because the concentration of precipitating electrons into the cusp regions compensates for the magnetic mirror effect, while the proton-induced CO₂⁺ UVD emission is diffuse without any fine structures. We also simulated atomic oxygen 557.7 nm and 630.0 nm emission lines, which have not yet been observed as auroral emissions on Mars. The oxygen 557.7 nm emission is similar in shape and intensity to the CO₂⁺ UVD emission. The oxygen 630.0 nm emission is restricted to the cusp regions, SEP electron precipitation being its dominant source because proton-induced emission is completely quenched at low altitudes.