Gravity Wave Effects in the Martian Thermosphere: Simulations from the M-GITM 3D General Circulation Model Utilizing a Nonlinear Gravity Wave Parameterization Scheme

The effects of gravity waves have been observed up to 250 km altitude in the Martian thermosphere, where they are associated with fluctuations seen in densities and temperatures (e.g. Yiğit et al., 2015; England et al., 2017). Modeling studies have indicated that gravity waves can have significant effects in the mesosphere and lower thermosphere of Mars, including notable impacts on the circulation pattern through momentum deposition and additional heating/cooling (e.g., Medvedev et. al., 2011; Medvedev and Yiğit, 2012).

In this study, the effects of gravity waves on the Martian upper atmosphere, and in particular, the thermospheric winds, will be discussed based on simulations from a Mars global circulation model (MGCM). A spectral nonlinear gravity wave parameterization scheme (Yiğit et al., 2008) has been newly incorporated into the Mars GCM, M-GITM (Mars Global Ionosphere-Thermosphere Model). M-GITM is able to simulate the Martian atmosphere from the ground to 250 km, and includes physics appropriate for thermospheric altitudes. Comparisons have been done between runs of M-GITM with gravity wave effects included and a baseline case without the effects of gravity waves. Adding the gravity wave parameterization scheme has produced notable changes in the mean flow, including altering the velocities of the thermospheric winds.

The goal of this research is to produce new model simulations with improved physics that can be compared to the neutral thermospheric wind measurements from the NGIMS (Neutral Gas and Ion Mass Spectrometer) instrument on the MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft. These data-model comparisons will help determine the impacts of gravity waves on the mean circulation in the thermosphere and as well as the possible role of gravity wave effects during specific NGIMS wind observational campaigns.