A new Mars Global Ionosphere-Thermosphere Model (M-GITM) is presented that combines the terrestrial GITM framework with Mars fundamental physical parameters, ion-neutral chemistry, and key radiative processes in order to capture the basic observed features of the thermal, compositional, and dynamical structure of the Mars atmosphere from the ground to the exosphere (0-250 km). Lower, middle, and upper atmosphere processes are included, based in part upon formulations used in previous lower and upper atmosphere Mars GCMs. This enables the M-GITM code to be run for various seasonal, solar cycle, and dust conditions. M-GITM validation studies have focused upon simulations for a range of solar and seasonal conditions. Key upper atmosphere measurements are selected for comparison to corresponding M-GITM neutral temperatures and neutral-ion densities. In addition, simulated lower atmosphere temperatures are compared with observations in order to provide a first-order confirmation of a realistic lower atmosphere. M-GITM captures solar cycle and seasonal trends in the upper atmosphere that are consistent with observations, yielding significant periodic changes in the temperature structure, the species density distributions, and the large-scale global wind system. For instance, mid afternoon temperatures near ∼200 km are predicted to vary from ∼210 to 350 K (equinox) and ∼190 to 390 k (aphelion to perihelion) over the solar cycle. These simulations will serve as a benchmark against which to compare episodic variations (e.g., due to solar flares and dust storms) in future M-GITM studies. Additionally, M-GITM will be used to support MAVEN mission activities (2014)(2015)(2016).

The response of the Mars dayside exospheric temperatures to short and long term solar flux changes was recently established. Characterization of the relative importance of various thermospheric heating and cooling mechanisms for maintaining these Mars exospheric temperatures requires the systematic application of modern global dynamical models that capture both lower and upper atmosphere thermal and dynamical processes. Coupled Mars General Circulation Model (MGCM) plus Mars Thermospheric General Circulation Model (MTGCM) simulations are utilized for this study, closely matching conditions during Mars Global Surveyor drag measurements. Simulations confirm the major balance of EUV heating and thermal heat conduction at dayside exospheric altitudes. However, the influence of variable Martian global winds is significant and must be carefully considered when investigating the global regulation of Mars exospheric temperatures over the solar cycle and Martian seasons. Finally, the present MGCM‐MTGCM heating and cooling processes suggests that an EUV‐UV heating efficiency of 19% yields net heating in accord with MGS exospheric temperatures.

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[1] We characterize middle-atmosphere polar warming (PW) using nearly three Martian years of temperature observations by the Mars Climate Sounder. We report the observed structure of PW and share hypotheses as to possible explanations, which have yet to be tested with global dynamical models. In the data, PW manifested between p = 15 Pa and p = 4.8Â10 -3 Pa. The latitude where PW maximized shifted poleward with decreasing pressure. The nightside magnitude was larger than the dayside magnitude. The maximum nightside magnitudes ranged from 22 to 67 K. As expected, the annual maximum magnitude in the north occurred during late-local fall to middle-local winter. In the south it occurred during late-local winter. Also as expected, the maximum magnitude near MY 28's southern winter solstice was smaller than that at that same year's northern winter solstice, when a global dust storm was occurring. Unexpectedly, the maximum magnitude at southern winter solstice was comparable to that at northern winter solstice for both MY 29 and MY 30, years that did not experience global dust storms but certainly experienced greater dust loading during L s = 270 than L s = 90 . Another unexpected result was a hemispheric asymmetry in PW magnitude during most of the observed equinoxes. This paper also provides tables of (1) averaged temperatures as a function of latitude, pressure, and season, and (2) the maximum polar warming features as a function of pressure and season. These tables can be used to validate GCM calculations of middle-atmosphere temperatures and constrain calculations of unobserved winds.