Investigation of Martian UV Dayglow Emissions in the Southern Hemisphere during Solar Quiet-time Conditions: Insights from Multi-year MAVEN/IUVS Observations

Abstract

The southern hemisphere of Mars possesses concentrated region of strong crustal magnetic fields (CMF), which generate localized magnetic anomalies that can influence atmospheric dynamics and energy deposition in the Martian thermospheric-ionospheric system. Although their effects on the atmosphere (>200 km) in the southern hemisphere are well documented, however their role in modulating the behavior of atmospheric plasma and neutrals below 200 km are poorly understood. The atmosphere at these altitudes can be comprehended by studying the variation of dayglow emissions. We have investigated few dayglow emissions over the CMF and non-CMF regions using the MAVEN remote-sensing measurements from Martian Years 33-37. Particularly, the CO Cameron bands, CO2+ ultraviolet doublet, and atomic oxygen emissions at 297.2 nm, 130.4 nm, and 135.6 nm have been studied below 200 km during solar quiet-time conditions. The results show strong seasonal variations in all the emissions peak altitudes and intensities in the dayside and near-terminator regions. The variation in the peak altitude of molecular and atomic emissions are nearly 20 km and 30 km, respectively. On the dayside, the emissions show minimal variation across CMF and non-CMF regions, indicating a minimal effect of the CMF at these altitudes, suggesting a key role of plasma demagnetization and photochemical processes. In addition, an insignificant variation in the dayglow emissions is likely masked by compensating mechanisms such as energy-dependent electron shielding and thermospheric expansion. This work presents the first focused investigation on the dayglow emissions over CMF and non-CMF regions across different seasons and solar zenith angles.