Comparison of terrestrial and Martian TEC at dawn and dusk during solstices

Abstract

This paper used the similarities between the ionospheres on Mars and Earth, the most similar of the terrestrial planets, to examine the relative importance of photochemical and transport processes at dawn and dusk. The amount of plasma present in the ionosphere, as measured by the total electron content (TEC), was examined at different locations for both solstice seasons over a solar cycle. Using the rate of change of TEC as a function of solar zenith angle made it possible to compare the plasma production via photoionisation and loss via recombination in the main layer of each planetary ionosphere despite the extreme differences in the total quantity of plasma. This study finds that, at least to first order, the dawn and dusk TEC slopes at Mars are symmetric. This symmetry is interpreted as an indicator of photochemical equilibrium. Deviations from photochemical equilibrium in different geographic and aerographic regions were used to explore the underlying processes responsible for plasma transport. Seasonal and solar cycle variations were also examined at dusk. These variations found that differing interactions with solar forcing mechanisms resulted in a Martian ionosphere with regions that showed evidence of significant transport processes at solar maximum, while at Earth transport processes were most important at solar minimum. In general, the photochemical processes in both ionospheres behave similarly when no magnetic field is considered. The presence or absence of a magnetic field shape the production via photoionisation and loss via recombination processes in both ionospheres, especially when considering plasma transport. This study has notable implications for comparative aeronomy, as a good understanding of how the ionosphere of magnetised and un-magnetised bodies compares is important for characterising planetary environments and atmospheric evolution over long time scales.

Sun resonant forcing of Mars, Moon, and Earth seismicity

“…These densities are possibly due to transport via kinetic Alfvén waves during exposure to northward IMF, where the higher current density reveals the higher duskside magnetic field that also energizes faster (Walsh et al, 2014). Thus, while MHD simulations suggest that dawn-dusk asymmetry in solar wind entry by reconnection is related to ionospheric conductance (Li et al, 2008), the similarity between magnetized Earth's ionosphere and non-magnetized Mars's ionosphere (Burrell et al, 2020) makes it plausible that similar proportions of the dawn-dusk asymmetry should hold for Mars as well.…”

Electron Densities in the Ionosphere of Mars: Comparison of MAVEN/ROSE and MAVEN/LPW Measurements

“…Lastly, recent work has suggested that the traditional approach of excluding time of day when considering Mars ionospheric variations with solar zenith angle may obscure important trends (Benna et al, 2015;Burrell et al, 2020;Cui et al, 2020;Gupta et al, 2021Gupta et al, , 2019Lee et al, 2020;Pilinski et al, 2019Pilinski et al, , 2017Steckiewicz et al, 2019). For instance, consider the dawn and dusk terminators.…”