The Martian Atmosphere in Late 2003 to Early 2004: Observations, Predictions, and Analyses I Posters
Presiding: P Withers, Boston University; M D Smith, NASA Goddard Space Flight Center
P21F-01 0830h
MOC Observations of Water-Ice Clouds Over Major Martian Volcanoes
Using Mars Global Surveyor Mars Orbiter Camera daily global maps, cloud areas have been measured daily for water-ice clouds associated with the topography of the major volcanoes Olympus Mons, Ascraeus Mons, Pavonis Mons, Arsia Mons, Elysium Mons, and Alba Patera. This study expands on that of Benson et al. (2003, Icarus 165, 34) by continuing their cloud area measurements of the Tharsis volcanoes, Olympus Mons and Alba Patera for an additional Martian year (August 2001 - May 2003) and also including Elysium Mons measurements from March 1999 through May 2003. The seasonal trends in cloud activity established by Benson et al. (2003) for the five volcanoes studied earlier are corroborated here with an additional year of coverage. Interannual variations that could be associated with the large 2001 planet encircling dust storm are minimal. Elysium Mons cloud activity is similar to that of Olympus and Ascraeus Mons, however the peak in cloud area is near Ls = 140° rather than near Ls = 100°. At Arsia Mons, where cloud activity was continuous in the first two years, clouds disappeared totally for ~85° of Ls (Ls = 188° - 275°) due to the planet encircling dust storm in 2001. This work is supported by the NASA Mars Data Analysis Program (Grant &35; NAG5-18126) and a MGS Team Science Analysis grant from JPL.
P21F-02 0830h
Modeling the Middle and Upper Atmosphere of Mars for Late 2003 to Early 2004
We have created a new Mars GCM that extends from about 14 km above the planetary surface to altitudes of about 300km, thus coupling the lower and upper atmospheres. The model includes Mars-appropriate dynamics, chemistry, and energetics. Some preliminary results for a dust-free tide-free atmosphere are presented, showing temperature and composition profiles, electron density distributions, and global wind patterns for late 2003 to early 2004. The simulations are validated against measurements of neutral density, temperature, and electron density.
P21F-03 0830h
Solar Wind Conditions at Mars Predicted in Late 2003 and Early 2004
The solar wind plays a key role in the dynamics of the Martian upper atmosphere, ionosphere and radiation environment. The Hakamada-Akasofu-Fry (HAFv.2) solar wind model was used in a real-time prediction mode to forecast solar wind conditions and interplanetary shock arrival times at Mars in late 2003 and early 2004. The HAFv.2 model uses a modified kinematic approach to simulate solar wind speed, density, dynamic pressure and interplanetary magnetic field in the global heliosphere. The late 2003-early 2004 period included intervals of very disturbed solar wind observed at Earth. We compare simulations from the HAFv.2 model with data from the ACE L1 spacecraft near Earth, with observations in the close Martian environment, and with simulations by the Han-Wu-Dryer-Detman 3D-MHD solar wind model. The NASA Living With a Star Targeted Research and Technology Program is supporting this work.
P21F-04 0830h
The Mars Polar Vortex: 2003-2004
The winter season, westerly circumpolar flow of the martian atmosphere, like that of the terrestrial stratosphere, is concentrated into a jet which lies near 60 degrees latitude. This jet is known as the polar vortex. Polar vortices are of interest because they act as a barrier, inhibiting energy transport and potentially preventing the mixing of aerosols and chemical species. Thus, they control the response of winter polar processes to climatic forcings, both short term and long term. We have used the Mars Global Surveyor Thermal Emission Spectrometer nadir-pointed data set to generate a gridded time series of vertically resolved temperatures, and from this time series we estimate the horizontal wind field using an adaption of the "balance winds" methodology suggested by Randel (1987, J. Atmos. Sci, 44). From the wind field we calculate Ertel potential vorticity (PV), which is a conserved quantity for adiabatic flow and therefore acts as a dynamical tracer for evaluating the extent of mixing into the winter polar region. Animations of these PV maps are an important tool for visualizing the polar vortex's behaviors. The Mars polar vortex in the northern winter of 2003 shows a variety of interesting structures and behaviors, some of which appear to be characteristic of the martian polar vortices, and some of which are unique to that year and season. Characteristic features of the martian polar vortex include: 1) Rossby number of order 1, and often exceeding 1 in northern winter, in the core of the circumpolar jet; 2) a local maximum in PV on the poleward flanks of the jet, giving the potential vorticity field an annular shape and suggesting the possibility of barotropic instability; 3) a well organized northern hemisphere polar vortex that persists past Ls 330 into early 2004, and which we expect acts as an effective barrier to mixing over time scales less than the PV conservation time scale of 10 days. One notable event unique to the 2003 northern winter is a major displacement of the polar vortex, greatest on December 15, 2003, which was associated with a concurrent increase in global dust opacity. The polar vortex returned to its normal symmetric configuration by December 27.
P21F-05 INVITED 0830h
MHD Studies on the Electron Impact Ionization and Charge Exchange Effects of the Solar Wind Interaction with Mars
We have improved our recently published 3D global MHD model of Mars(Ma et al., 2004) by incorporating the global variation of the neutral densities, using the appropriate Mars TGCM results. We also improved on the Chapman approximation used in our earlier model and now use appropriate optical depth values in calculating the ionization rates. In this paper we present results from this improved model and compare them with Viking and MGS observations. Finally in order to evaluate the importance of charge exchange and impact ionization on the interaction between the solar wind and Mars, we made calculations both including and neglecting these two processes and compare these results.
P21F-06 0830h
A new Model of the Solar Wind Interaction with the Mars Ionosphere
We introduce a new MHD model of the Mars atmosphere-ionosphere-solar wind system. The model is adapted from a terrestrial MHD model of the global ionosphere-thermosphere-magnetosphere system, and includes a chemistry set appropriate for Mars and the presence of crustal magnetic fields. We present first results of the solar wind interaction with the Mars ionosphere, including the effects of the crustal fields on ionopause height and bow shock location.