Mars Global Ionosphere‐Thermosphere Model: Solar cycle, seasonal, and diurnal variations of the Mars upper atmosphere

Abstract

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).

Solar wind interaction with the Martian upper atmosphere: Crustal field orientation, solar cycle, and seasonal variations

“…In this section, we will briefly introduce the Mars Global Ionosphere Thermosphere Model (M-GITM) [Bougher et al, 2015], the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) [Lee et al, 2013[Lee et al, , 2014a[Lee et al, , 2014b, and the 3-D BATS-R-US Mars multifluid MHD (MF-MHD) model [Najib et al, 2011;Dong et al, 2014]. All these models are being used to generate a model library of simulated outputs for the MAVEN mission (2014)(2015)(2016).…”

“…Mars Global Ionosphere Thermosphere Model (M-GITM) [Bougher et al, 2015] is a 3-D whole atmosphere code that captures both the Mars lower atmosphere and its thermosphere-ionosphere. The applied domain of this model is 0-250 km (ground-to-exobase).…”

“…Detailed M-GITM simulations have been conducted over the past few years, spanning various seasonal, solar cycle, and dust conditions [Bougher et al, 2015]. Model validation thus far has focused upon simulations for solar longitude Ls = 90, 180, and 270 for both solar minimum (F 10.7 = 70) and solar maximum (F 10.7 = 200) conditions.…”

“…Atmospheric dynamics and chemistry are greatly affected by temperature, suggesting that the entire Mars atmosphere is an integrated system that must be treated as a whole from the ground to the exobase (∼0 to 250 km) [Bougher et al, 2015]. In fact, strong coupling processes are known to link the Mars lower to upper atmospheres [e.g., Bougher et al, 2014].…”

“…Basically, the hot oxygen has a thermal speed larger than the local background thermal speed (calculated based on M-GITM thermospheric profile [Bougher et al, 2015]), indicating the scale height of hot oxygen is larger than that of the cold oxygen [e.g., Ma et al, 2004, Figures 1 and 2]. However, the hot oxygen can be converted to the thermal oxygen via collisions with other background cold neutral species before it escapes to interplanetary space [Lee et al, 2013].…”