Modeling of Diffuse Aurora due to Precipitation of H⁺‐H and SEP Electrons in the Nighttime Atmosphere of Mars: Monte Carlo Simulation and MAVEN Observation

Abstract

The nighttime limb intensity of diffuse auroral emission of CO 2 + (B 2 Σ u + -X 2 π g ) Ultraviolet Doublet (UVD) is observed in the northern hemisphere of Mars during 17-21 December 2014 from Imaging Ultraviolet Spectrograph instrument onboard Mars Atmosphere and Volatile Evolution. We have used hybrid model and four-dimensional yield spectrum approach based on Monte Carlo simulation to calculate the ionization rate, limb intensity, and ion and electron densities of diffuse aurora due to precipitation of solar energetic particle and proton-hydrogen (H + -H) fluxes in the nighttime ionosphere of Mars. It is found that the production rates of atmospheric ions (CO 2 + , N 2 + , and O + ) are dominant in the upper ionosphere at about 100-150 km due to impact of H + -H. The solar energetic particle formed auroral ionosphere (CO 2 + , NO + , and O + ) in the middle ionosphere between 50 and 100 km due to precipitation of monoenergetic electrons of energies 25 to 100 keV. The simulated limb intensities of CO 2 + UVD due to impact of H + -H and auroral electrons are compared with Imaging Ultraviolet Spectrograph observations. Our model results are overestimating the observations, but 100 keV electrons deposited maximum energy around 75 km, closer to the observed altitude of the maximum emission. The densities of upper ionosphere (O 2 + , NO + , and CO 2 + ) due to impact of H + -H are smaller by one to two orders of magnitude than that produced by auroral electrons in the middle ionosphere.

Modeling of Diffuse Auroral Emission at Mars: Contribution of MeV Protons

“…(2017); the possible reasons are the different total elastic cross section and ionization cross section used in the two models. However, the penetration altitude of electrons during the December 2014 SEP event in our calculation (in case 2) is consistent with Haider and Masoom (2019), as explained in Section 4.2.…”

“…Case A Case B ASPEN (Jolitz et al, 2017) elastic cross section. and Masoom (2019). For protons, the penetration altitude of 5 MeV protons is approximately 55-65 km, which is approximately 10-20 km higher than Jolitz et al (2017).…”

“…Previous studies were not able to reproduce the observed SEP-induced CO2 + UVD auroral emission profiles with precipitating energetic electrons considering the electron energy flux during SEP events observed by MAVEN (Schneider et al, 2015;Gérard et al, 2017;Haider and Masoom, 2019). This study aimed to reproduce the observed CO2 + UVD profiles by taking into account the contribution of energetic protons reaching MeV energies.…”

“…Penetration of SEPs into the Martian atmosphere leads to increased ionization, heating of the atmosphere and alteration of the atmospheric chemistry (Leblanc et al, 2002;Jolitz et al 2017;Haider and Masoom, 2019;Gérard et al, 2017;Lingam et al, 2018). One of the consequences of the interaction of SEPs with the Martian atmosphere is the production of auroral emissions (Schneider et al, 2015).…”

Test Particle Model Predictions of SEP Electron Transport and Precipitation at Mars

“…An extended diffuse emission over the northern hemisphere was observed during a strong SEP electron event in December 2014. Modeling has suggested the emission is caused by ∼60–200 keV electrons (Gérard et al., 2017; Haider & Masoom, 2019; Schneider et al., 2015). Our simulations suggest electrons of these energies would preferentially precipitate discretely along open field lines, rather than precipitating diffusely.…”