A Statistical Study of the Vertical Scale Height of the Martian Ionosphere Using MAVEN Observations

Abstract

The Vertical Scale Height (VSH) is a crucial parameter that describes the shape of the ionospheric electron density profile. Evidence suggests a complex relationship between VSH and the thermal structure and dynamics of the ionosphere. A statistical study was conducted on the VSH at low altitudes (175 km) and high altitudes (300 km) in the Martian ionosphere, using data from the MAVEN observations from 2014 to 2023. The results suggest that the influence of the crustal magnetic field on VSH₁₇₅ is more pronounced than on VSH₃₀₀. VSH₁₇₅ shows a minor peak around −20° latitudes, which is more than 7% higher than the average value, and an increasing trend with latitude in the northern hemisphere. VSH₃₀₀ is higher in the southern hemisphere than in the northern hemisphere, especially in summer, by approximately 42.1%. Regarding the local time variation of VSH, we observed an increasing trend from midnight to morning and a decreasing trend from dusk to midnight in almost all conditions. The local time variation of VSH also exhibits seasonal and latitudinal dependence. These variations have different levels of consistency with the gradient of the electron temperature (Te) and the collision frequency between charged particles and neutrals. Specifically, the correlation coefficient between VSH₁₇₅ and the collision frequency between charged particles and neutrals reaches as high as 0.93 in the northern hemisphere winter and southern hemisphere summer. The correlation coefficient between VSH₃₀₀ and the gradient of the Te reaches up to 0.72 in the southern hemisphere equinox.