This paper introduces the new Venus Global Ionosphere Thermosphere Model (V-GITM) which incorporates the terrestrial GITM framework with Venus-specific parameters, ion-neutral chemistry, and radiative processes in order to simulate some of the observable features regarding the temperatures, composition, and dynamical structure of the Venus atmosphere from 70 km to 170 km. Atmospheric processes are included based upon formulations used in previous Venus GCMs, several augmentations exist, such as improved horizontal and vertical momentum equations and tracking exothermic chemistry. Explicitly solving the momentum equations allows for the exploration of its dynamical effects on the day-night structure. In addition, V-GITM’s use of exothermic chemistry instead of a strong heating efficiency accounts for the heating due to the solar EUV while producing comparable temperatures to empirical models. V-GITM neutral temperatures and neutral-ion densities are compared to upper atmosphere measurements obtained from Pioneer Venus and Venus Express. V-GITM demonstrates asymmetric horizontal wind velocities through the cloud tops to the middle thermosphere and explains the mechanisms for sustaining the wind structure. In addition, V-GITM produces reasonable dayside ion densities and shows that the neutral winds can carry the ions to the nightside via an experiment advecting O$_2^+$.

Mars present-day middle and upper atmosphere, above ~100 km, connects the deep atmosphere to the Martian space environment. This region is important to understand for many reasons, including for more general insights into the evolution of atmospheres, as a comparison to other planetary atmospheres, and for current and future mission development and interpretation. The middle/upper atmosphere is greatly influenced by the physics of the lower atmosphere (water cycle, dust cycle, waves, etc.) and the solar environment (solar magnetic activity, solar events). It contains the upper branch of the overturning meridional circulation and the transitional point of the main heating source from near-IR to UV radiation. These influences feed on a primitive property of an atmosphere: temperature. This work will break down the radiative processes that drive the Martian’s thermal structure above ~100 km as a function of latitude and season. We demonstrate the on-going work on extending the NASA Ames Mars Global Climate Model (MGCM), now using the NOAA/GFDL FV3 dynamical core. The MGCM nominally extends from the surface up to ~80 km but new physics packages will extend the MGCM’s vertical domain up to ~250 km. We present the heating and cooling mechanisms that dominate this atmospheric region, discuss the parametrizations used, the state of the seasonal/diurnal thermal structure, and finally, we discuss the work in progress for the development and implementation of physics schemes in our model.

The chemical evolution of an exoplanetary Venus-like atmosphere is dependent upon the ultraviolet to near ultraviolet (FUV-NUV) radiation ratio from the parent star, the balance between CO2 photolysis and recombination via reactions that depend on the water abundance, and various catalytic chemical cycles. In this study, we use a three-dimensional (3-D) model to simulate conditions for a Venus-like exoplanet orbiting the M-dwarf type star GJ436 by varying the star/planet distance and considering the resultant effects on heating/cooling and dynamics. The simulation includes the middle and upper atmosphere (<40 mbar). Overall, these model comparisons reveal that the impact of extreme ultraviolet to ultraviolet (EUV-UV) heating on the energy balance shows both radiative and dynamical processes are responsible for driving significant variations in zonal winds and global temperature profiles at < 10-5 mbar. More specifically, CO2 15-μm cooling balances EUV/UV and Near InfraRed (NIR) heating at altitudes below 10-7 mbar pressure with a strong maximum balance for pressures at ~10-5 mbar, thus explaining the invariance of the temperature distribution at altitudes below 10-5 mbar pressure for all cases. Our model comparisons also show that moderate changes in NIR heating result in relatively small changes in neutral temperature in the upper atmosphere, and virtually no change in the middle atmosphere. However, with larger changes in the NIR heating profile, much greater changes in neutral temperature occur in the entire upper and middle atmosphere studied.