Based on the retrieved Martian exospheric temperature from MAVEN/IUVS Lyman-α airglow observations, this study comprehensively analyzed the long-term and short-term effects of solar radiation, dust activity, and atmospheric tides on the upper atmosphere of Mars, and developed an empirical model incorporating the coupling of multiple factors.
Solar, Dust, and Tidal Effects on Martian Dayside Exospheric Temperature: An Empirical Model Based on a Decadal MAVEN/IUVS Data Set
Zhen Xu and Jianqi Qin
Abstract
The Martian exospheric temperature, Texo, is a fundamental parameter that regulates atmospheric escape from Mars to space. Previous studies have shown that this parameter varies significantly in response to both solar forcing and atmospheric dynamics. Accurately quantifying and modeling exospheric temperature is essential for understanding Mars' long-term climate evolution. Using a decadal dataset of Lyman-α airglow emission observed by the Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere and Volatile Evolution (MAVEN) mission, we derived the Martian dayside exospheric temperature under varying solar and atmospheric conditions during 2014–2023. Our analysis indicates that the Martian dayside exospheric temperature varies from ~140–300 $K$ over the past decade. Long-term variations are primarily driven by solar forcing, with a sensitivity of ~45 $K·mW^{-1}·m^2$ to the solar Lyman-α flux measured at Mars. Short-term variations are influenced by dust activity and atmospheric tides. On average, the Martian dayside exospheric temperature is enhanced by ~20.1 $K$ during large-scale dust storms, and atmospheric tides lead to longitudinal variations with magnitudes of ~10–15 $K$ and ~10–30 $K$ near aphelion and perihelion, respectively. We developed an empirical model of the Martian dayside exospheric temperature through multi-dimensional least-squares fitting, which is capable of capturing the combined effects of solar, dust, and tidal forces. This model offers a valuable tool for estimating the Martian exospheric variability under diverse conditions.
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