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Communication Dans Un Congrès Année : 2023

Impacts of Solar Energetic Particles on the Atmospheric Composition on Present-day Mars

Résumé

Solar energetic particles (SEPs) are high-energy (from a few tens of keV to GeV) charged particles consisting mainly of electrons and protons ejected from the Sun associated with solar flares and coronal mass ejections. SEPs precipitating into planetary atmospheres induce ionization, dissociation, and excitation of atmospheric species, leading to changes in atmospheric composition (e.g., Solomon et al., 1981). The effects of SEPs on ozone concentration in Earth’s polar region have been intensively studied for the past decades. For instance, during the SEP event in late October 2003, which is known as the Halloween event, NOx and HOx concentrations were enhanced, and ozone concentration was depleted by 40% at the polar lower mesosphere (e.g., Jackman et al., 2005). The impacts of SEPs on the Martian atmospheric composition are expected to be global due to the lack of an intrinsic magnetic field and different from Earth due to the dissimilarity in atmospheric composition, however, the impacts of SEPs on atmospheric neutral composition are far from understood in contrast to Earth. This study estimates the impacts of SEPs on neutral chemical composition in the present-day Martian atmosphere using a Monte Carlo model and a one-dimensional photochemical model. Our results show that the ozone density decreases by a factor of 10 at 40 km altitude during a Halloween-class SEP event due to the loss of O by an enhanced HO2 density through ion-neutral chemistry and CO recombination catalytic cycle. We perform a sensitivity test of ozone changes on the SEP flux intensity and find that a 75% depletion of the ozone density at 40 km can be expected even during even a less intense SEP event occurring once a year. Such ozone depletion is expected to be detected by the Nadir and Occultation for MArs Discovery (NOMAD) instrument on board the Trace Gas Orbiter (TGO) spacecraft measurements in future SEP events. We show that the ozone density sufficiently decreases during a SEP event on Mars as on Earth but through different chemical pathways driven by CO2 ionization and CO recombination catalytic cycle.
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Dates et versions

insu-04343557 , version 1 (13-12-2023)

Identifiants

  • HAL Id : insu-04343557 , version 1

Citer

Yuki Nakamura, François Leblanc, Naoki Terada, Sayano Hiruba, Isao Murata, et al.. Impacts of Solar Energetic Particles on the Atmospheric Composition on Present-day Mars. AGU Fall Meeting 2023, Dec 2023, San Francisco, United States. ⟨insu-04343557⟩
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