Dust storm impacts on the Mars upper atmosphere

Coupling between the Mars lower (less than or equal to 80 km) and upper atmospheres is a fundamental issue affecting dynamics, tracer distributions, and energy balance. Also, this coupling has significant bearing on future mission planning to the planet (e.g. Mars Global Surveyor aerobraking). Two general circulation models are currently being run in tandem to investigate tides and their generation, propagation, and impact upon the Mars lower thermosphere. The NASA. Ames Mars General Circulation Model (MGCM) is first run for Mars near-perihelion (Ls similar to 270) conditions for which a 20-SOL dust-storm is initiated and allowed to self-consistently evolve. Subsequently, selected MGCM upper boundary fields are used to specify the height of the lower boundary and to drive semi-diurnal tides in the NCAR Mars Thermospheric General Circulation Model (MTGCM) for identical Mars parameters. MTGCM key fields are presented to illustrate the profound impact of Mars lower atmosphere heating and tides upon the Mars thermospheric structure and dynamics. (C) 1997 COSPAR. Published by Elsevier Science Ltd.