Effects of Global and Regional Dust Storms on the Martian Hot O Corona and Photochemical Loss

Abstract

We examine here for the first time the effects of both global and regional dust storms on the formation of the Martian hot O corona and associated photochemical loss of O. Our study is conducted by utilizing our integrated model framework, which couples our Martian hot O corona model with a multifluid magnetohydrodynamic model for Mars for the dusty and clear atmospheric condition cases. We present our results with the most up-to-date cross sections for the O( 3 P)-CO 2 collisions. The main effect of dust storms on the ionosphere is the upward shift of the ionosphere on the dayside, which results in an increase in production of hot O at all altitudes above the ionospheric peak. However, the dust-induced inflation of the neutral upper atmosphere results in an enhancement in collisional loss of hot O and thus effectively suppresses the hot O density, reducing the global photochemical loss rate by~28% for the global dust storm scenario. The relative density structure of the hot O corona does not show any significant changes, while its magnitude decreases at all altitudes.

Effects of the 10 September 2017 Solar Flare on the Density and Composition of the Thermosphere of Mars

“…Over the same altitude range of 170-220 km, modeling by Y. Lee et al (2020) also indicates enhanced densities during regional dust storms, by roughly 25-80% (O) and 80-185% (CO 2 ) above baseline levels. In contrast, the aforementioned density enhancements from baseline to solar flare-affected conditions were smaller than regional dust storm effects below ∼190 km but exceeded them at higher altitudes.…”

“…Journal of Geophysical Research: Space Physics density changes with those produced by the 10 September 2017 flare, we compare flare event observations with observed and modeled densities of O and CO 2 derived from figures in Liu et al (2018), Y. Lee et al (2020), and Elrod et al (2020).…”

“…Modeled global dust storm conditions, based from the 1971–1972 global dust storm on Mars, indicate in contrast with the flare, solar cycle, and regional dust storm effects in the thermosphere that the abundance of O decreases compared to in the undisturbed, baseline atmosphere, at altitudes above 150 km (Y. Lee et al., 2020). In the 170–220 km altitude range, the O densities decrease by roughly ∼35–40% and most greatly at middle thermospheric altitudes (∼190 km).…”

Studies of the 2018/Mars Year 34 Planet‐Encircling Dust Storm

“…While the upward shift in the ionosphere increases the production of hot oxygen (“hot O”), the expansion of the neutral atmosphere increases its collisional loss. In combination, this reduced the oxygen escape rate during the storm by ∼28% (Lee et al., 2020).…”

“…Future work is needed to determine the robustness of this O density decline and how it could impact Mars' atmospheric evolution through time. Recall that Lee et al (2020) find a 28% decrease in the escape of ionized hot O during the storm.…”