The Mars thermosphere. 2. General circulation with coupled dynamics and composition

Conference · Thu Aug 30 00:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

OSTI ID:5313222

Bougher, S W ^[1]; Roble, R G; Ridley, E C; Dickinson, R E ^[2]

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1. Univ. of Arizona, Tucson (USA)
2. National Center for Atmospheric Research, Boulder, CO (USA)

The National Center for Atmospheric Research thermospheric general circulation model (TGCM) for the Earth's thermosphere has been modified to examine the three-dimensional structure and circulation of the upper mesosphere and thermosphere of Mars (MTGCM). The computational framework and major processes unique to a CO{sub 2} thermosphere are similar to those utilized in a recent Venus TGCM. Solar EUV, UV, and IR heating alone combine to drive the Martian winds above {approximately}100 km. An equinox version of the code is used to examine the Mars global dynamics and structure for two specific observational periods spanning a range of solar activity: Viking 1 (July 1976) and Mariner 6-7 (August-September 1969). The MTGCM is then modified to predict the state of the Mars thermosphere for various combinations of solar and orbital conditions. Calculations show that no nightside cryosphere of the type observed on Venus is obtained on the Mars nightside. Instead, planetary rotation significantly modifies the winds and the day-to-night contrast in densities and temperatures, giving a diurnal behavior similar to the Earth under quiet solar conditions. Maximum exospheric temperatures are calculated near 1,500 LT ({le} 305 K), with minimum values at 0500 LT ({le} 175 K). The global temperature distribution is strongly modified by nightside adiabatic heating (subsidence) and dayside cooling (upwelling). The global winds also affect vertical density distributions; vertical eddy diffusion much weaker than used in previous one-dimensional models is required to maintain observed Viking profiles. A solar cycle variation in dayside exospheric temperatures of {approximately}195-305 K is simulated by the Viking and Mariner runs.

• OSTI ID: 5313222
• Report Number(s): CONF-9001119-; CODEN: JGREA
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:B9; Conference: 4. international conference on Mars, Tucson, AZ (United States), 10-13 Jan 1990; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MARS PLANET
PLANETARY ATMOSPHERES
ATMOSPHERIC CIRCULATION
CARBON DIOXIDE
CHEMICAL COMPOSITION
DYNAMICS
GENERAL CIRCULATION MODELS
HEATING
MODIFICATIONS
ROTATION
SOLAR CYCLE
SOLAR RADIATION
TEMPERATURE GRADIENTS
THREE-DIMENSIONAL CALCULATIONS
VARIATIONS
WIND
ATMOSPHERES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
MATHEMATICAL MODELS
MECHANICS
MOTION
OXIDES
OXYGEN COMPOUNDS
PLANETS
RADIATIONS
STELLAR RADIATION
640107* - Astrophysics & Cosmology- Planetary Phenomena