Mars Thermospheric Variability: Disentangling the Influence of Irradiance, Dust, and Dynamics
Journal Article
Overview
abstract
Abstract; We present a comprehensive analysis of Martian thermospheric variability using nearly a decade of solar occultation measurements from the MAVEN Extreme Ultraviolet Monitor (EUVM). These data provide vertical profiles of density and temperature from to 180 km at dawn and dusk, enabling the investigation of long‐term drivers of variability and latitudinal structure. Exospheric temperatures, derived from fits to 130–200 km temperature profiles, are found to be strongly correlated with solar EUV irradiance and track the solar cycle, while densities at 180 km are dominated by seasonal variability driven by total solar irradiance and dust heating of the lower atmosphere. This decoupling of temperature and density highlights the importance of both solar and lower atmospheric processes in regulating thermospheric structure. Latitudinal patterns differ by local time: dawn is influenced primarily by large‐scale meridional circulation, while dusk variability reflects a combination of solar heating and dynamical modulation by dust. Comparisons with the Mars Global Ionosphere‐Thermosphere Model (MGITM) indicate that gravity waves play a key role in shaping the observed latitudinal structure. Regional dust storms enhance dynamical effects at dawn and local heating at dusk, with impacts extending to latitudes decoupled from the storm locations. The exospheric temperature response to solar EUV irradiance is compared to recent measurements at Earth, showing a ∼50% difference from prior comparisons, with Earth being 3–5× more sensitive than Mars to solar EUV irradiance induced temperature changes. These results provide new constraints on the coupled solar, dust, and dynamical forcing of the Martian thermosphere.
